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What is the neuraxis?
An imaginary line drawn through the center of the length of the central nervous system, from the bottom of the spinal cord to the front of the forebrain.
What direction is anterior?
With respect to the central nervous system, located near or toward the head. (front of brain)
What does rostral mean?
Literally, "toward the beak;" with respect to the CNS, in a direction along the neuraxis toward the front of the face. (front of brain)
What direction is posterior?
With respect to the CNS, located near or toward the tail (the bottom of the brain).
What direction is caudal?
Literally, "toward the tail;" with respect to the CNS, in a direction along the neuraxis away from the front of the face. (bottom of brain)
What direction is dorsal?
Literally, "toward the back" it is a diretion perpendicular to the neuraxis toward the top of the bead or back
What direction is ventral?
"Toward the belly" in respect to the CNS, it is a direction perpendicular to the neuraxis toward the bottom of the skull or the front surface of the body.
What direction is "lateral"?
Toward the side of the body, away from the middle.
What direction is "medial"?
Toward the middle of the body, away from the side?
What direction is "ipsilateral"?
Located on the same side of the body.
What direction is "contralateral"?
located on the opposite side of the body.
What is a "cross section"?
With respect to the CNS, a slice taken at right angles to the neuraxis.
What is a frontal brain section?
A slice through the brain parallel to the forehead.
What is a horizontal brain section?
A slice through the brain parallel to the ground.
What is a sagittal section?
A slice through the brain parallel to the neuraxis and perpendicular to the ground.
What is the midsagittal plane?
The plane through the neuraxis perpendicular to the ground; divides the brain into two symmetrical halves.
What are the major divisions of the nervous system?
- CNS = Brain & Spinal Cord
- PNS = Nerves & Peripheral Ganglia
Which layers of meninges cover the PNS? the CNS?
PNS = Although the PNS lacks the arachnoid membrane and the associated pool of CSF in the subarachnoid space, the outer and inner layers (dura and pia mater) fuse and form a sheath that covers the spinal and cranial nerves and the peripheral ganglia.
CNS = Arachnoid membrane, dura mater, and pia mater
What are meninges (singular: meninx)?
The three layers of tissue that encase the central nervous system: dura mater, the arachnoid membrane, and pia mater.
What is dura mater?
The outermost of the meninges; tough and flexible.
What is the arachnoid membrane?
The middle layer of the meninges, located between the outer dura mater and inner pia mater.
What is pia mater?
The layer of the meninges that clings to the surface of the brain; thin and delicate.
What is the subarachnoid space?
The fluid-filled space that cushions the brain; located between the arachnoid membrane and the pia mater.
What is cerebrospinal fluid (CSF)?
A clear fluid, similar to blood plasma, that fills the ventricular system of the brain and the subarachnoid space surrounding the brain and spinal cord.
What is a ventricle?
One of the hollow spaces within the brain, filled with CSF.
What is the lateral ventral?
One of the two ventricles located in the center of the telencephalon.
What is the thrid ventricle?
The ventricle located in the center of the diencephalon.
What is the cerebral aqueduct?
A narrow tube interconnecting the third and fourth ventricles of the brain, located in the center of the mesencephalon.
What is the fourth ventricle?
The ventricle located between the cerebellum and dorsal pons, in the center of the metencephalon.
What is a choroid plexus?
The highly vascular tissue that protrudes into the ventricles and produces CSF.
What are arachnoid granulations?
Small projections of the arachnoid membrane through the dura mater into the superior sagittal sinus; CSF flows through them to be reabsorbed into the blood supply.
What is the superior sagittal sinus?
A venous sinus located in the midline just dorsal to the corpus callosum, between the two cerebral hemispheres.
What is Obstructive hydrocephalus?
A condition in which all or some of the brain's ventricles are enlarged; caused by an obstruction that impedes the normal flow of CSF.
When does the development of the human nervous system begin? How does it begin?
It begins around the 18th day of conception. It is formed by the neural tube, which is a hollow tube that is closed at the rostral end that forms from the ectodermal tissue early in embryonic development.
What are the three major parts of the brain? How are they designated?
They are designated by which ventricle they surround. The three major parts of the brain are the forebrain, the midbrain, and the hindbrain.
What is the cerebral cortex? How many layers does it have?
It is the outermost layer of gray matter of the cerebral hemisphere. It has 6 layers, w/ the last layer formed being closest to the skull.
What are progenitor cells?
Cells of the ventricular zone that divide and give rise to cells of the CNS
What is the ventricular zone (VZ)?
A layer of cells that line the inside of the neural tube; contains progenitor cells that divide and give rise to cells of the CNS
What is the subventricular zone (SVZ)?
A layer of progenitor cells located just inside the ventricular zone; thicker in mammals w/ large brains.
What is a symmetrical division?
Division of a progenitor cell that gives rise to two identical progenitor cells; increases the size of the ventricular zone and hence the brain that develops from it.
What is an asymmetrical division?
Division of a progenitor cell that gives rise to another progenitor cell and a neuron, which migrates away from the ventricular zone toward its final resting place in the brain.
What are radial glia?
Special glia with fibers that grow radially outward from the ventricular zone to the surface of the cortex; provide guidance for neurons migrating outward during brain development.
What is neurogensis?
The production of new neurons through the division of neural stem cells; occurs in the hippocampus and olfactory bulb and appears to play a role in learning.
What ventricles does the forebrain surround?
The lateral and third ventricles
What are the subdivisions of the forebrain?
The Telencephalon and the Diencephalon
What are the principal structures of the Forebrain?
The cerebral cortex, the basal ganglia, and the limbic system.
What ventricle does the Midbrain surround?
The Cerebral aqueduct.
What is the subdivision of the midbrain?
What are the principal structures of the Midbrain?
The Tectum and Tegmentum.
What ventricle does the Hindbrain surround?
The Fourth Ventricle.
What are the subdivisions of the Hindbrain?
The Metencephalon and the Myelencephalon.
What are the principal structures of the Hindbrain?
The Cerebellu, the Pons, and the Medulla oblongata.
What is the Forebrain?
The most rostral of the three major divisions of the brain; includes the telencephalon and the diencephalon.
The telencephalon includes most of the ______
Cerebral hemispheres, which is one of the major portions of the forebrain because it is covered by the Cerebral Cortex.
What are subcortical regions?
The region located within the brain, beneath the cortical surface.
What are sulci (singular: sulcus)?
A groove in the surface of the cerebral hemisphere, smaller than a fissure.
What is a fissure?
A major groove in the surface of the brain, larger than a sulcus.
What are gyri?
Convolutions of the cortex of the cerebral hemispheres, separated by sulci or fissures.
Approximately how much of the surface of the cortex is hidden in the grooves? What does this ultimately do to the size of the cortex?
Approximately two thirds of the surface of the brain is hidden by convolutions. As a result, the size of the cortex is tripled.
What is the cerebral cortex mostly made of?
Glia and the cell bodies, dendrites, and interconnecting axons, which is why it is referred to as gray matter.
Beneath the cerebral cortex are axons that connect the neurons of the cerebral cortex with those located elsewhere in the brain. The large concentration of myelin gives this tissue the nickname____
What are the three areas of the cerebral cortex that receive info from the sensory organs?
The primary visual cortex, the primary auditory cortex, the prmary motor cortex, and the primary somatosensory cortex.
Primary visual cortex
The region of the posterior occipital lobe whose primary input is from the visual system. It is location on the occipital lobe on the inner surfaces of the cerebral hemispheres, primarily on the upper and lower banks of the calcarine fissure.
What is the calcarine fissure?
a fissure located in the occipital lobe on the medial surface of the brain; most of the primary visual cortex is located along its upper and lower banks.
What and where is the primary auditory cortex?
It is the area that receives auditory info. It's located on the lower surface of a deep fissure in the side of the brain- the lateral fissure. It is in the superior temporal lobe.
What is the lateral fissure?
It is the fissure that separates the temporal lobe from the overlying frontal and parietal lobes. The primary auditory cortex resides on its lower surface.
What and where is the primary somatosensory cortex?
Is is a vertical strip of cortex just caudal to the central sulcus. It receives information from the body senses. Different regions of the primary somatosensory cortex receive info from different regions of the body. It is located in a regio of the anterior partietal lobe.
What is the central sulcus?
The sulcus that separates the frontal lobe from the parietal lobe.
What is the insular cortex? In addition to the primary somatosensory cortex, what is it involved in?
It is a sunken regio of the cerebral cortex that's normally covered by the rostral superior temporal lobe and caudal inferior frontal lobe.
What and where is the primary motor cortex?
It is the region of the posterior frontal lobe that contains neurons that control movements of the skeletal muscles. It is located just in front of the primary somatosensory cortex. Neurons in different parts of the primary motor cortex are connected to muscles in different parts of the body.
The regions of the primary snesory and motor cortex occupy only a small part of the cerebral cortex. The rest accomplishes ____. Where does these processes take place?
perceiving, learning and remembering, plannings and acting. They take place in association areas of the cortex.
The central sulcus provides an important dividing line between the rostral and caudal regions of the cortex. What are the regions involved in?
The rostral region is involved in movement-related activities, such as planning and executing behaviors. The caudal region is involved in perceiving and learning.
What are the four lobes of the Cerebral Cortex? Where are they located?
- The frontal lobe: includes everything in front of the central sulcus. It is the anterior portion of the cerebral cortex, rostral to the parietal lobe and dorsal to the temporal lobe.
- The parietal lobe: the :wall" is located on the side of the cerebral hemisphere, just being the central sulcus, caudal to the frontal lobe. The region of the cerebral cortex caudal to the frontal lobe and dorsal to the temporal lobe.
- The temporal lobe: The "temple" juts forward from the base of the brain, ventral to the frontal and parietal lobes. It's the region of the cerebral cortex rostral to the occipital lobe and ventral to the parietal and frontal lobes.
- The occipital lobe: Lies at the very back of the brain, caudal to the parietal and temporal lobes.
What is a sensory association cortex?
Those regions of the cerebral cortex that receive information from the regions of primary sensory cortex.
Regions of the sensory association cortex located closest to the primary sensory areas receive information from only one sensory system. Ones that are far from primary sensory regions receive info from more than one sensory system.
Sensory association areas perceive and store memories.
What is the motor association cortex?
It is the region of the frontal lobe rostral to the primary motor cortex and it is also known as the premotor cortex. It is the region that controls the pimary motor cortex.
The rest of the frontal lobe, rostral to the motor association cortex is the ____. It is involved in ____
The prefrontal cortex. It is involved in formulating plans and strategies.
Although the two cerebral hemispheres cooperate with each other, they don't perform identical functions. Some are lateralized. What does this mean?
Functions are located primarily on one side of the brain.
In general, the left hemisphere participates in ___. The right hemisphere participates in___
- Left = analysis of information
- Right = synthesis of "big picture"
The cortex can be further subdivided into ___ & ____.
The neocortex and the limbic cortex
The neocortex includes which lobes and what other cortices?
It includes all of the lobes, the primary sensory cortex, the primary motor cortex, and association cortices. It is phylogenetically newest.
Where is the limbic cortex located? What is it part of? What does it contain?
It is located around the medial edge of the cerebral cortex. It is the phylogenetically oldest cortex and it is part of the limbic system. It contains the cingulate gyrus.
What is the cingulate gyrus?
It is a strip of the limbic cortex lying along the lateral walls of the groove separating the cerebral hemispheres, just above the corpus callosum.
What is the limbic system? What is its primary function and primary parts?
The limbic system is a group of brain regions including the anterior thalamic nuclei, the amygdala, hippocampus, limbic cortex, and parts of the hypothalamus (mammillary bodies), as well as their interconnecting fiber bundles (fornix). It is involved in regulating emotion and motivation, among other things.
What is the hippocampus?
It is a forebrain structure of the temporal lobe, constituting an important part of the limbic system; includes the hippocampus proper, dentate gyrus, and the subiculum.
What is the Amygdala?
A structure in the interior of the rostral temporal lobe, containing a set of nuclei; part of the limbic system
What is the fornix?
The fornix is a fiber bundle that connects the hippocampus with other parts of the brain, including the mamillary bodies of the hypothalamus; part of the limbic system.
What are mammillary bodies?
They are a protrusion of the bottom of the brain at the posterior end of the hypothalamus, containing some hypothalamic nuclei; part of the limbic system.
What are the basal ganglia? What are the major parts?
They are a collection of subcortical nuclei in the telencepahlon, which lie beneath the anterior portion of the lateral ventricles. The major nuclei are the caudate nucleus, the globus pallidus, and the putamen; important parts of the motor system.
What is the diencephalon? What does it contain?
It is a region of the forebrain surrounding the third ventricle; it includes the thalamus and the hypothalamus
What is the thalamus? Where is it located and what does it do?
The thalamus is the largest portion of the diencephalon, located above the hypothalamus. It contains nuclei that project information to specific regions of the cerebral cortex and receive info from it (the cerebral cortex). It makes up the dorsal part of the diencephalon. It is situated near the middle of the cerebral hemispheres, immediately medial and caudal to the basal ganglia. Most neural input to the cerebral cortex is received from the thalamus; indeed, much of the cortical surface can be divided into regions that receive projections from specific parts of the thalamus.
What is a projection fiber?
An axon of a neuron in one region of the brain whose terminals form synapses with neurons in another region.
What is the lateral geniculate nucleus?
A group of cell bodies within the lateral geniculate body of the thalamus that receives fibers from the retina and projects fibers to the primary visual cortex.
What is the medial geniculate nucleus?
It's a group of cell bodies within the medial geniculate body of the thalamus; receives fibers from the audiotry system and projects fibers to the primary auditory cortex.
What is the ventrolateral nucleus?
A nucleus of the thalamus that receives inputs from the cerebellum and sends axons to the primary motor cortex.
What is the Hypothalamus?
It is the group of nuclei of the diencephalon situated beneath the thalamus; involved in regulation of the autonomic nervous system, control of the anterior and posterior pituitary glands, and integration of species-typical behaviors. It also controls the endocrine system and orgranizes behaviors related to survival- the Four F's.
Much of the endocrine system is controlled by hormones produces by cells in the ____.
What is the anterior pituitary gland?
The anterior part of the pituitary gland; an endocrine gland whose secretions are controlled by the hypothalamic hormones.
What are neurosecretory cells?
Neurons that secrete a hormone or hormonelike substance. They secrete hypothalamus hormones and are located near the base of the pituitary stalk. They stimulate the anterior pituitary gland to secrete its hormones.
The hypothalamus also produces the hormones of the ____ and controls their secretion.
The posterior pituitary gland, which is the posterior part of the pituitary glad; or, an endocrine gland that contains hormone-secreting terminal buttons of axons whose cell bodies lie within the hypothalamus.
The midbrain, or mesencephalon, surrounds which ventricle? What does it consist of?
- The cerebral aqueduct
- The tectum and tementum
What is the Tectum?
- *Think "Roof"
- *It is the dorsal part of the midbrain and it includes the superior and inferior colliculi, which appear as four bumps on the dorsal surface of the brain stem.
What are the Superior Colliculi?
Protrusions on top of the midbrain. They are part of the visual system and work w/ the ingerior colliculi to react to moving stimuli and w/ visual reflexes.
What are the inferior colliculi?
They are protrustions on top of the midbrain. They are involved in the auditory system. They work with the superior colliculi to respond to moving stimuli and to create visual reflexes.
What is the brain stem?
The "stem" of the brain, from the medulla to the midbrain, excluding the cerebellum. It also includes the hindbrain.
What is the Tegmentum?
It is the ventral part of the midbrain and it includes the periaqueductal gray matter, reticular formation, red nucleus, and the substantia nigra.
What is the Reticular Formation?
The Reticular Formation is a large network of neural tissue located in the central region of the brain stem, from the medulla to the diencephalon. It receives sensory information by means of various pathways and projects axons to the cerebral cortex, thalamus and spinal cord. It plays a role in sleep and arousal, attention, muscle tonus, movement, and various vital reflexes.
It is part of the tegmentum of the midbrain
What is periqueductal gray matter? Why is it called that?
It is the region of the midbrain, in the tegmentum, surrounding the cerebral aqueduct. It contains neural circuits involved in species-typical behaviors, like fighting and mating. It is named as such because it consists mostly of cell bodies of neurons that surround the cerebral aqueduct as it travels from the thirds to the fourth ventricle.
What are the red nucleus and the substantia nigra? What are they important for?
- Red Nucleus: A large nucleus of the midbrain that receives inputs from the cerebellum and motor cortex and sends axons to motor neurons in the spinal cord.
- Substantia Nigra: A darkly stained region of the tementum that contains neurons that communicate with the caudate nucleus and putamen in the basal ganglia.
They are important components of the motor system.
What is the Hindbrain? What ventricle does it surround and what are its two major divisions?
The hindbrain is the most caudal of the three major divisions of the brain. It includes the metencephalon and the myelencephalon. It surrounds the fourth ventricle.
What is the cerebellum?
The cerebellum has two hemispheres and resembles an little brain, even covered by a cerebellar cortex and a set of deep cerebellar nuclei. It is located dorsal to the pons and is an important component of the motor system.
It is in the metencephalon of the hindbrain/
What is the cerebellar cortex?
It is the cortex the covers the surface of the cerebellum.
What are the deep cerebellar nuclei?
They are the nuclei located within the cerebellar hemispheres. They receive projections from the cerebellar cortex and send projections out of the cerebellum to other parts of the brain.
What are cerebellar peduncles?
3 bundles of axons that attach each cerebellar hemisphere to the dorsal pons
What is the Pons?
It is the region of the metencephalon (Hindbrain) rostral to the medulla, caudal to the midbrain, and ventral to the cerebellum. The pons contains, in its core, a portion of the reticular formation, including some nuclei that appear to be important in sleep and arousal. It also contains a large nucleus that relays information from the cerebral cortex to the cerebellum
The Myelencephalon is a part of the ____brain and contains one major structure, the ___.
- 1.) The Hindbrain
- 2.) The medulla oblongata, which contains part of the reticular formation, including the nuclei that control vital functions such as regulation of the cardiovascular system, respiration, and skeletal muscle tonus. It is the most caudal portion of the brain. It is immediately rostral to the spinal cord.
What is the spinal cord? What is its principal function?
It is a cord of nervous tissue that extends caudally from the medulla. Its principal function is to distribute motor fibers to the effector organs of the body (glands and muscles) and to collect somatosensory info to be passed on to the brain. Various reflexive control circuits are located here, giving the spinal cord some autonomy from the brain.
The spinal cord is protected by the vertebral column, which is composed of ___ vertebrae that are divided into three regions named ___; and fused vertebrae that make up the ___ & ___ of the column
- 1.) 24
- 2.) Cervical, Thoracic, Lumbar
- 3.) Sacral and Coccygeal
The spinal cord is only about 2/3 as long as the certebral column; the rest of the space is filled by a mass of ___ composing the ____
- Spinal Roots: a bundle of axons surrounded by connective tissue that occurs in pairs, which fuse and form a spinal nerve
- Cauda Equina: A bundle of spinal roots located caudal to the end of the spinal cord.
Small bundles of fibers emerge from each side of the spinal cord in two straight lines along its dorsolateral and ventrolateral surfaces. Groups of these bundles fuse together and become 31 paired sets of ___ and ___ roots. These join together as they pass through the intervertebral foramens and become ____
- Dorsal Roots: the spinal roots that contains incoming (afferent) sensory fibers
- Ventral Roots: The spinal roots that contains outgoing (efferent) motor fibers.
- Spinal Nerves
What are spinal nerves? Where do they begin?
A spinal nerve is a peripheral nerve attached to the spinal cord. They begin at the junction of the dorsal and ventral roots of the spinal cord.
What is an afferent axon?
It is an axon directed toward the central nervous system, conveying sensory information.
What is an efferent axon?
An axon directed away from the CNS, conveying motor commands to muscles and glands.
The cell bodies that give rise to the afferent axons that bring somatosensory info to the spinal cord reside in the ____.
Dorsal Root Ganglia, which are nodules on a dorsal root that contains cell bodies of afferent spinal nerve neurons.
There are ___ pairs of cranial nerves. What do they do?
- There are 12 pairs of cranial nerves
- They are peripheral nerves attached directly to the brain, most of which serve sensory and motor functions of the head and neck region.
What is the Vagus Nerve?
The largest of the cranial nerves, it conveys efferent fibers of the parasympathetic division of the autonomic nervous system to organs of the thoracic and abdominal cavities.
What is the olfactory bulb?
It is a protrusion at the end of the olfactory nerve. It receives input from the olfactory receptors.
The peripheral nervous system is divided into two parts, the ___ & the ___.
- The somatic nervous system: which is the part of the PNS that controls the movement of the skeletal muscles or transmits somatosensory info to the CNS
- The autonomic nervous system: The portion of the PNS that controls the body's vegetative functions. It is concerned with the regulation of smooth muscle, cardiac muscle, and glands.
The autonomic nervous system (ANS) is divided into two systems, the ___ & the ____.
The Sympathetic and the Parasympathetic.
What does the sympathetic division of the ANS do?
The sympathetic division of the ANS is the portion that controls functions that accompany arousal and expenditure of energy. Excitation.
The cell bodies of the sympathetic motor neurons are located in the gray matter of the thoracic and lumbar regions of the spinal cord. The fibers of these neurons exits via the ventral roots. After joining the spinal nerves, the fibers branch off and pass into ____. What are these?
Sympathetic Ganglia: Nodules that contain synapses between preganglionic and post ganglionic neurons of the sympathetic nervous system.
Individual sympathetic ganglia are connected to the neighboring ganglia above and below, forming the ____.
The sympathetic ganglion chain
The axons that leave the spinal cord through the ventral root belong to the ____
The preganglionic neuron, which is the efferent neuron of the autonomic nervous sytem wh ose cell body is located in a cranial nerve nucleus or in the intermediate horn of the spinal gray matter and whose terminal buttons synapse upon postganglionic neurons in the autonomic ganglia.
What is a post ganglionic neuron?
Neurons of the ANS that form synapses directly with the target organ. They form synapses with the axons of the preganglionic neurons.
What is the adrenal medulla?
It is the inner portion of the adrenal gland, located atop the kidney, controlled by sympathetic nerve fibers; secretes epinephrine and norepinephrine.
What is the function of the parasympathetic division of the ANS?
It supports activities that are involved with increases in the body's supply of stored energy. These activities include salvation, gastric and intestinal motility, secretion of digestive juices, and increased blood glow to the gastro-intestinal system.
It is the portion of the autonomic nervous system that controls functions that occur during a relaxed state.
Why is the parasympathetic division of the ANS sometimes referred to as the "craniosacral system"?
It is sometimes called the craniosacral system because the cell bodies that give rise to the preganglionic axons in the parasympathetic nervous system are located in two regions: the nuclei of some of the cranial nerves and the intermediate horn of the gray matter in the sacral region of the spinal cord.
What is a sensory neuron?
A neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system.
What is a motor neuron?
A motor neuron is a neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland.
What is an interneuron? What are two subtypes?
- A neuron located entirely within the CNS.
- Local interneurons: form circuits with nearby neurons and analyze small pieces of information.
- Relay interneurons: connect circuits of local interneurons in one region of the brain with those in other regions.
Neurons come in three main shapes. What are they and what differentiates them?
- Multipolar: The dendrites connect to the soma, which is connected to a long axon, and finally the axon connects to the terminal buttons. A prototypical neuron.
- Bipolar: one axon and one dentritic tree, at opposite ends of the soma. Bipolar neurons are usually sensory; that is, their dendrites detect events occurring in the environment and communicate information about these events to the CNS.
- Unipolar: like bipolar neurons, they transmit sensory information. The arborizations outside the CNS are dendrites; the arborizations within the CNS end in terminal buttons. The dendrites of most unipolar neurons detect events in our joins, muscles and internal organs.
When an action potential traveling down the axon reaches the terminal buttons, the secrete a chemical called a ___. This chemical either ___ or ___ the receiving cell and thus helps to determine whether an action potential occurs in its axon.
What is a membrane?
A structure consisting principally of lipid molecules that defines the outer boundaries of a cell and also constitutes many of the cell organelles, such as the Golgi apparatus.
Embedded within the membrane are a variety of protein molecules that have special functions.
What is the nucleus? What are the primary residents of the nucleus?
The nucleus is a structure in the central region of a cell, containing the nucleolus and chromosomes.
What is the nucleolus?
It is the structure w/in the nucleus of a cell that produces ribosomes, which are cytoplasmic structures made of protein that serve as the site of production of the proteins translated from mRNA.
What is a chromosome?
It is a strand of DNA, with associated proteins, found in the nucleus; carries genetic info
When they are active, portions of the chromosomes (genes) cause production of ____, which receives a copy of the info stored at that location. The ____then leaves the nuclear membrane and attaches to ___ where it causes the production of ____
- a particular protein
What is a gene?
A gene is the functional unit of the chromosome, which directs synthesis of one or more proteins.
Proteins are important in cell function. Not only do they provide cellular structure, they also serve as enzymes. What do enzymes do?
Enzymes direct the chemical processes of a cell by controlling chemical reactions. Enzymes are special protein molecules that act as catalysts.
Because cells contain the ingredients needed to synthesize an enormous variety of compounds, the ones that cells actually do produce depend primarily on the particular enzymes that are present.
Enzymes either break molecules apart as well as put them together.
What is mRNA?
A macromolecule that delivers genetic info concerning the synthesis of a protein from a portion of a chromosome to a ribosome
What is the genome?
The sequence of nucleotide bases on the chromosomes that provide the information needed to snythesize all the proteins that can be produced by a particular organism
While the size of the genome does not correlate with the complexity of the genome, the amount of ___ does.
non-protein-coding DNA, or "junk" DNA.
What do the non-coding sequences of DNA do?
It gets transcribed in to non-coding RNA, ncRNA, which can be used as spliceosomes, which cut and splice mRNA that contains the final info required to make a protein. Molecules of ncRNA also attach to and modify proteins that regular gene expression.
The bulk of the cell consists of ___. What does this substance contain?
- The cytoplasm, which is the viscous, semiliquid substance contained w/in the interior of the cell.
- It contains small specialized structures, just as the body contains specialized organs. As such, these structures are called "organelles."
What is the Mitochondria? Where did they originate from?
It is an organelle that is responsible for extracting energy from nutrients. The cells provide mitochondria nutrients and the mitochondria provides cells with ATP, which is what cells use as their immediate source of energy.
Most cell biologists believe that they were free-living organisms that came to "infect" larger cells. Because they could extract energy more efficiently, they stayed put.
What is the Endoplasmic Reticulum?
It is a set of parallel layers of membrane found within the cytoplasm of a cell.
Rough ER contains ribosomes and is involved with the production of of proteins that are secreted by the cell. The protein produced by the ribosomes that are attached to the rough ER is destined to be transported out of the cell or used in the membrane. Unattached ribosomes are also distributed around the cytoplasm for protein production w/in the neuron.
Smooth ER is the site of synthesis of lipids and provides channels for the segregation of molecules involved in various cellular processes.
What is the Golgi Apparatus?
The Golgi Apparatus is a complex of parallel membranes in the cytoplasm that wraps the products of a secretory cell. It is a special form of smooth ER within which, some complex molecules are assembled.
In addition to assembly of complex molecules and packaging products for exocytosis, the Golgi Apparatus also produces lysosomes. What are they and what do they do?
Lysosomes are organelles surrounded by membrane that contain enzymes that break down waste products.
What is the cytoskeleton? How is it formed?
The cytoskeleton gives the neuron its shape. It is formed of microtubules and other protein fibers that are linked to each other, forming a cohesive mass. The thickest of these strands, microtubules, are bundles of protein filaments arranged around a hollow core.
What is axoplasmic transport?
It is an active process by which substances are propelled along microtubules that run the length of the axon. Movement from the soma to the terminal buttons is called anterograde axoplasmic transport. Movement from terminals to soma is called retrograde axoplasmic transport.
How is anterograde axoplasmic transport accomplished?
It is accomplished by molecules of a protein called kinesin. In the cell body, kinesin molecules, which resemble a pair of legs and feet, attach to the item being transported down the axon. The kinesin molecule the walks down a microtubule, carrying the cargo to its destination. Energy is supplied by ATP molecules produced by the mitochondria.
How is retrograde axoplasmic transport accomplished?
A protein, dyein, carries substances from the terminal buttons to the soma.
Neurons constitute only about ___ of the volume of the CNS. The rest consists of a variety of supporting cells. In what way do supporting cells support neurons? What are the two major types of supporting cells?
- Because neurons have a very high rate of metabolism, but have no means of storing nutrients, they must constantly be supplied with nutrients and oxygen or they will die.
- Glia & Schwann Cells
Glial cells are the most important supporting cells of the CNS. What do they do and what are the three subtypes of Glial cells?
- They glue the CNS together, as well as buffer the neurons physically and chemically from the rest of the body. They surround neurons and hold them in place, controlling their supply of nutrients and some of the chemicals they need to exchange messages w/ other neurons; they insulate neurons from one another so that neural messages don't get scrambled; and thy even act as housekeepers; destroying and removing the carcasses of neurons that are killed by disease or injury.
- Astrocytes, oligodendrocytes, and microglia
What does an Astrocyte do?
It is a glial cell that provides support for neurons of the CNS, it provides nutrients and other substances, and regulates the chemical composition of the extracellular fluid.
Some of the astrocyte's processes (arms) are wrapped around blood vessels; the others are wrapped around parts of neurons, so the somatic and dendritic membranes of neurons are largely surrounded by astrocytes...this is how the neurons receive most of their nutrients- by converting glucose to lactate.
The maintain the blood-brain barrier, regulate local pH and ion gradients.
They form scar tissue of CNS in a process called gliosis
They also serve as the matrix that holds the neurons in place. Finally, they surround and isolate synapses, limiting the dispersion of neurotransmitters that are released by the terminal buttons.
How do astrocytes "feed" neurons?
Astrocytes receive glucose from capillaries and break it down into lactate, the chemical produced during the first step of glucose metabolism. They then release lactate into the extracellular fluid that surrounds neurons, and neurons take up the lactate, transport it to their mitochondria, and use it for energy.
How do astrocytes clean up neurons?
Through phagocytosis, which is a process by which cells engulf and digest other cells or debris caused by cellular degeneration.
What is an oligodendrocyte?
It is a type of glial cell in the CNS that forms myelin sheaths and supports the axons.
A given oligodendrocyte produces up to 50 segments of myelin. During the development of the CNS, oligodendrocytes form processes shaped something like canoe paddles. Each of these paddle-shaped processes then wraps itself many times around a segment of an axon and, while doing so, produces layers of myelin. Each paddle thus becomes a segment of an axon's myelin sheath.
What is microglia?
The smallest type of glial cell. Like some types of astrocytes, they act as phagocytes. In addition, they serve as one of the representatives of the immune system in the brain, protecting the brain from invading microorganisms. They are primarily responsible for the inflammatory reaction in response to brain damage.
What are Schwann Cells?
They serve the same function as oligodendrocytes in the CNS, but in the PNS. That is, they support axons and produce myelin. The difference is that a Schwann cell provides myelin for only one axon, and the entire Schwann cell, surrounds the axon. The composition in the myelin is different between the CNS and PNS.
They also aid in the digestion of the dead and dying axons in the PNS. Then, they arrange themselves in a series of cylinders that act as guides for regrowth of the axons. The CNS supporting cells do not do this.
The blood-brain barrier is a ____.
A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain's capillaries. Substances must be actively transported through the capillary walls by special proteins.
The blood-brain barrier is not uniform thoughout the nervous system. In several places, the barrier is relatively permeable, allowing substances that are excluded elsewhere. For example, ____ is a part of the brain that controls vomiting. It does this by permitting neurons in this region to detect the presence of toxic substances w/in the blood.
What is a membrane potential?
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell
What is the resting potential of a neuron?
The membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials; approximately -70mV.
What is depolarization? What happens to a neuron when it depolarizes?
Depolarization is the reduction of the membrane potential of a cell from its normal resting potential.
When a neuron depolarizes at a certain threshold, it creates an action potential in the process of righting itself.
What is hyperpolarization?
An increase in the membrane potential of a cell, relative to the normal resting potential.
What is the action potential?
The brief electical impulse that provides the basis for conduction of info along an axon.
The membrane potential is the result of a balance of what two opposing forces?
Diffusion and electrostatic pressure.
When some substances are dissolved in water, they split into two parts, each with an opposing electrical charge. Substances with this property are called ___
Electrolytes- an aqueous solution of a material that ionized- namely, a soluble acid, base, or salt.
What is electrostatic pressure?
The attractive force between atomic particles charged with opposite sings or the repulsive force between atomic particles charged with the same sign.
What ions are most prominent in and around the neuron?
- Organic anions- proteins and intermediate products of the cell's metabolic processes found only in the intracellular fluid.
- Chloride ions- predominately extracellular
- Sodium ions- predominately extracellular
- Potassium ions- predominately intracellular
How can sodium remain in the greatest concentration in the extracellular fluid, despite the fact that both forces tend to push it inside?
The sodium-potassium pump continuously pushed sodium out of the axon. sodium-potassium transporters are proteins found in the membranes of all cells that extrudes 3 NA+ and transports 2 K+ into the cell.
What causes the action potential w/in a neuron?
A brief increase in the permeability of the membrane to Na+, thus allowing these ions to rush into the cell, is immediately followed by a transient increase in the permeability of the membrane to K+ (allowing these ions to rush out of the cell).
How does the permeability of the membrane change to allow ions to enter or leave the cells?
Through ion channels, specialized protein molecules that permit specific ions to enter or leave the cells when they're activated.
In the 1800s, many believed in a reticular theory of the brain. What did this theory say about the brain? How was it supported?
It stated that the brain was a network of fused cells, lacking specialization w/ every part being involved in all functions. This was furthered by the staining of the cells, by Golgi. This was the formation of histology.
Ramon Cajal refined the Golgi stain and proposed the neuron doctrine, or, cell theory. How did he do this and what did it state?
He cut the cell and it would die, but others wouldn't...thus suggesting that they're not fused.
The cell theory, or neuron doctrine, is what we know and love today. That the cells in the brain are not fused.
What are the ways to classify neurons?
HINT: w/ respect to the flow of info and w/ respect to the # of processes emanating from the cell body
- Flow of info w/ respect to the CNS:
- - Afferent: brings info toward a reference point, the CNS (sensory info)
- - Efferent: carries info away from the CNS
- - Interneuron: all parts of neuron in CNS
- - Relay/Local interneurons: processes lie w/in a subdivision of the CNS
- Number of processes:
- - Unipolar: retina, one axon
- - Bipolar: one dendrite, one axon
- - Multipolar: Most common type of neuron w/ multiple dendrites and one axon
- - Psuedo-unipolar: A little nubbin for the soma that isn't in between the dendrite and axon. Prevalent in the nervous system.
Describe the external (cell membrane) structure of the neuron.
What types of proteins are found w/in the membrane?
The cell membrane is made out of a phospholipid bilayer. Since the hydrophobic tails are not water soluble and are made out of fatty acids, they are electrically neutral. The hydophilic head is water soluble and is negatively polarized.
- There are different types of membrane proteins, intrinsic and extrinsic.
- - Intrinsic: are embedded in the membrane and have both an extracellular and an intercellular domain. They are receptors, transporters, and channels.
- - Extrinsic: peripheral proteins that are usually found on the intercellular, cytoplasmic side. While they're embedded in the membrain, they don't go through the entire membrane. They are typically enzymes.
The nucleus contains DNA. What is DNA made out of?
DNA is made up of polymers of nucleotides (guanine/Cytosine; Thymine/Adenine), and a sugar/phosphate backbone.
What does the sequences of nucleotides determine?
The sequences of nucleotides determines how DNA is expressed through the manufacture of proteins
DNA is long, so it is compacted in to chromosomes. How many are there?
23: 1-22 are autosomes. #23 is a pair of sex chromosomes
What is a karyotype?
A description of chromosomes.
How does DNA make proteins?
First the transcription process copies a segment of DNA into mRNA by using transcription factors that recruit or block RNA polymerase, which binds to protomotor regions on DNA and code it into a complimentary strand of mRNA.
Second, mature mRNA, lacking non-coding sections, leaves the nucleus and attaches to a ribosome.
Third, tRNA delivers the amino acid specified by the 3 nucleotide bases (codons) to the appropriate site on the mRNA.
Fourth, and finally, the next amino acid is delivered to the ribosome and peptide bonds are formed.
Each proteinogenic amino acid is represented by a triplet of bases. What is this called?
What is a neurofilament's primary ingredient and function?
- structural support of the cell
What is inclusive fitness?
The broader concept of fitness that suggests that fitness includes not only an individual's reproductive success, but the reproductive success of their relatives as well.
What are radial glia?
They are glial cells that guide neuronal migration in development
The resting potential is caused by an uneven distribution of ions across the cell wall. What factors are involved in creating and maintaining resting potentials?
- Active transport
- force of diffusion
- electrostatic force
- membrane resistance/permeability of membrane
What is the Nernst potential?
For any ion, the amount of electrostatic force necessary to create equilibrium. It is a relation between Eion (energy required to maintain a concentration gradients) and mV/VM (membrane voltage)
What are the two types of postsynaptic potentials? How are they caused?
- Excitatory EPSP: membrane voltage decreases (depolarization of the cell) They trigger action potential
- Inhibitory IPSP: membrane voltage increases and they inhibit AP
They're caused by transmembrane ion currents, which occur via a change in conductance
How does a change in membrane conductance occur?
Membrane conductance for ions is changed by opening and closing ion channels, which are either ligand or voltage gated.
What is ligand gating?
The opening and closing of ion channels that causes PSP via NT
What is voltage gating?
The opening and closing of ion channels that causes an AP by a different in voltage
What are some characteristics of PSPs?
HINT: time and space
PSPs decrease as they move away from the point of origin and the change in membrane voltage is time-dependent.
What is the length constant? What are two factors that affect it?
It is the distance that the potential travels until it has decreased to 2/3 of its original voltage.
It is effected by membrane and internal resistance via the ration rM/rI.
Why don't PSPs develop or decay instantly?
The delayed onset of PSPs is caused by the capactive property of the cell membrane. It needs to charge.
IPSPs and EPSPs are additive. What does this mean? What types can you get?
The input from all of the presynaptic potentials gets added together:
- Spatial: all literally add/subtract together
- Temporal: a consecutive set of signals of the same magnitude
What is neural integration?
Determined by spatial or temporal summation, it is the decision to send the signal on or not.
What are the characteristics of Action Potentials?
- They start at the axon hillock
- The spread toward the axon terminal
- The propagation is active
- They can travel long distances
- The amplitude is fixed. While you can get a stronger PSP, AP is all or none
What is the absolute refractory period?
When you can't generate another AP, due to the inactivation of the Na+ channels, which is at the "top" of the bell
What is the Relative refractory period?
You can generate another AP, but it takes a stronger stimulus. In essence, you'll need a larger depolarizing input to bring the undershoot back up to the threshold and then pass it.
How does Myelination increase the speed of the AP?
It increases speed through Saltatory Conduction.
The myelin keeps the signal from dissipating by increasing the resistance, so K+ can't leak out. It also decreases capactiance by separating the "plates" of either side of the cell even more- it's a thicker insulator.
The sheath is segmented to prevent the charge from getting used up before it gets to the axon terminal- nodes of Ranvier.
The signal continues to go down the axon passively and gets boosted by the nodes via the pumps and channels located there...as long as the voltage is sufficient when it gets to a node.
What are the two types of synapses?
- Gap Junctions/Electrical synapses: the connection is between the cytoplasm of the two cells, allowing molecules and ions to flow between cells. The junctions where the ions flow between the cells is an electrical synapse.
- Chemical synapses: The cytoplasm of the two cells is not continuous and information is transmitted by release of a chemical by one cell. If junction is between adjacent neurons or a neuron and an effector cell, the chemical is called a neurotransmitter.
What are the criteria of a chemical synapse?
- NT should be synthesized in neuron from which it is released
- NT should be released upon neuronal excitation
- NT should act on specific receptors on postsynaptic membrane
- There should be mechanisms for terminating action of the NT after release
What are the mechanisms for terminating action of NT after its release?
- Uptake: astrocyte takes NT
- Enzymatic breakdown
What is Dale's Principle? What's wrong w/ it?
A given neuron releases only one neurotransmitter from all terminals and all terminals released the same NT for a given neuron. While this isn't really true, it is common to classify neurons by what is presumably their principal NT.
An vesicular transporter transports NT into the synaptic vesicle. Is this passive or active?
This process is active, requiring ATP to complete.
What is a conformational change?
On the post-synaptic membrane, the NT comes into contact w/ the receptors (proteins) and binds w/ it. This changes the interactions among the atoms and the different regions in the protein, results in a shape change of the receptor. This opens up an ion channel so ions can flow into the post-synaptic cell. This utilizes ligand-gated ion channels.
There are receptors on the presynaptic cell that releases the NT that are autoreceptors. What do they do?
It regulates how much NT to make and released by detecting the NT that's released via presynaptic inhibition.
Vesicular transporters are antiporters, energized by V-ATPase. What does this mean? What type of transport is this? Why?
NT move in and protons come out. This is a type of secondary active transport because the proton pump requires ATP and, in turn, it creates a gradient that allows all of this to happen. V-ATPase acidifies the synaptic vesicles by pumping in protons, resulting in electrochemical gradients that provide energy for transporting NTs into synaptic vesicles.
Unlike vesicular transporters, membrane transporters are symporters. What does this mean and what do they do? How?
The NT and the sodium that drives the gradient change move in the same direction - in.
The co/counter transport of other ions may also occur.
What are the 4 main types of receptors on a post-synaptic neuron?
- Physiological receptors: it exists to receive endogenous chemical messengers
- Enzymes: many drugs bind to enzymes, making them receptors of those drugs
- Transporters (carriers): cells can get info from their transporters, but they're there to move stuff from one side of the membrane to the other.
- Non-protein macromolecules like DNA: things can bind to and alter DNA
What is transduction? How does it occur?
It is the translation of extracellular messenger into an intracellular response.
The ligand bind to the receptor, then a series of biological responses changes it.
What is occurs during the intrinsic phase of transduction?
- Molecular machinery, the effector, initiates the response.
- The transducers, or intermediate molecules, act between the binding target and the effector
- The ligand binding may directly regulate gates of ion channels or synthesis of molecules that become ligands for intracellular receptors- these are second messengers
What are the general properties of signal transduction?
- Pleiotropy: cell is responding to the enodgenous ligand w/ a multitude of effects
- Integration: integrates all signals received
- Can have rapid or slow onset of effects and the effects can be varying of duration
What are some common effector actions?
- They alter the ionic milieu of cells
- The alter the concentration of endogenous ligands
How do Effector Actions alter the concentration of endogenous ligands?
- They inhibit/activate enzymes
- Prevent storage of endogenous messengers
- Alter reuptake of endogenous messengers
- Up/Down regulate receptors (add or take away receptors on the membrane)
- Alter genetic expression
Why are signal transduction pathways important?
- They're necessary to understand brain physiology
- May be critical for understanding mental illness
- Signaling pathways may be useful targets for drugs