Lecture Ch12 Nervous Tissue and Ch13 Central Nervous tissue
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What are the functions of the nervous tissues?
To maintain homeostasis and integrate all body activities. includes:
- sense changes "Sensory functions"
- integrate information "integrative functions"
- response "motor neuron functions"
What is the Sensory neuron function?
mostly unipolar, Senses changes in the environment by conducting action potentials towards the cns cranial and spinal nerves
What is an Interneuron function?
Multipolar; located between sensory and motor neurons. Integrate incoming information and coordinates a motor response.
What is a motor neuron function?
Multipolar; Respond by controlling muscles and glands
Define an effector
a responsive body part such as; muscles (contraction) or glands (secretes hormones)
List the organization of the nervous system.
Central nervous system:
Peripheral nervous system:
- cranial nerves
- spinal nerves
- enteric plexuses
- sensory receptors
List the organizations of the cns
Processes incoming impulses from the pns
brain and spinal cord
- source of:
List the organizations of the pns
- Sensory receptors
- -cranial nerves
- -spinal nerves
- enteric plexuses
What are sub divisions of the pns?
somatic nervous system (sns) voluntary:
Automatic nervous system (ans) involuntary
Enteric nervous system (ens) involuntary
What are the functions of the pns?
Somatic nervous system is voluntary:
controls the skeletal muscles
Autonomics nervous system affects the heart and digestive system:
Sympathetic nervous system --controls the activity of the heart (fight or flight)
Parasympathetic nervous system---controls the body for rest and repair
A bundle of neurons
What are Ganglias
small clusters of nerve tissues
Transmits information throughout the body
Enteric plexuses (pns)
located in hollow walls of the organs of the gastrointestinal tracks, regulated the digestive system
Sensory receptors (pns)
nervous system structures that monitor changes in the internal and external environment and communicates them back to the cns.
subdivision of the pns
somatic nervous tissues are voluntary
consists of sensory neurons to the cns from somatic receptors in the head, body wall, and limbs
-receptors of the senses of vision, hearing, taste, and smell
includes motor neurons that conduct impulses from the cns to only skeletal muscles.
subdivision of the pns
Autonomic nervous system involuntary
sensory neurons convey info to the cns from autonomic sensory receptors located in the visceral organs (stomach and lungs)
Also consists of motor neurons that conduct nerve impulses from the cns to smooth muscle, cardiac muscle, and glands
What are the motor parts to the ans
Sympathetic division are neurons that have stimulate effectors that increase heart rate (fight or flight)
Parasympathetic division are neurons that stimulate effectors that decrease the heart rate (rest and repair)
Subdivision of pns
Enteric nervous system involuntary
Extends most of the gastrointestinal tract. It monitors chemical changes within the GI tract and the stretching of the walls.
Many of these neurons function independently of the cns, but could communicated via (sns and pns)
Describe the histology of a nervous tissue?
Nervous tissues are designed to transmit electrical impulses and includes:
- cell body--analyzes incoming information
- dendrites--receives incoming information
- axon--transmits information to other cells
- neuroglia cells--protects,protects and nourishes the neurons
- myelin sheath--allows axons to send faster signals
- terminal--synaptic ends
Neroglia--supports,nourishes, and protects neurons
define a neuron.
functional cell responsible for nervous system signaling
List three functional classes of a neuron.
sensory neuron--transmits signals
interneuron neuron--integrates incoming impulses with motor responses
motor neuron-transmits to the effectors
List three structural classes of a neuron.
- Multipolar--short dendrites and several axons
- ***located in motor and interneurons***
- Bipolar--longer dendrites two axons
- ***sensory neurons eyes,ears***
Unipolar--one dendrite and one axon ***sensory neurons***
receptors that detect stimuli touch, pressure, pain***
neurons that contain sensory receptors at their distal ends (dendrites) or synapse with sensory receptors that are separate cells.
neurons that convey action potentials away from the cns to the effector.
Neurons that interpret incoming impulses from the cns
have multipolar neurons
Multipolar neuron structures
- has several dendrites and axons
- mostly found in the brain and spinal cord
Bipolar neuron structure
Has one dendrite and two axons
considered a sensory neuron and is found in the retina, inner ear of the brain
Unipolar neuron structure
Has dendrites and one axon
Found in the sensory receptors that detect stimuli (touch,pain,pressure)
considered a sensory neuron
List all neuroglia cells in the CNS
Can be distinguished by the size and arrangement of their processes
- Ependymal cells
located in the CNS; controlls the chemical environment by forming blood brain barriers to prevent harmful substances from entering the cns.
Located in the CNS; has processes that wrap around several axons to form and maintain myelin sheath.
cns; neurons that function as phagocytic cells that get rid of old damaged nervous tissues and debris (vacuum cleaners)
Ependymal cells neuroglia
cubodial to columnar cells with microvilla and cilia that line hollow spaces in the brain and spinal canal. Forms the csf and assists in the circulation of cerebral spinal fluids.
List all neuroglia cells in the PNS
Neuroglia cells that wrap around axons and cell bodies of neurons.
- Schwann cells
- Satelite cells
Schwann cells neuroglia
PNS; surrounds axons and forms,maintains myelin sheath.
Satelite cell neuroglia
- surrounds the cell bodies of the ganglia neurons.
- Maintains the chemical environment of the neurons.
Describe the structure of myelin sheath.
made of lipids and proteins
***oligodendrocytes and schwann cells***
Compare myelinated and unyelinated sheath.
Myelinated sheath covers a single axon
unmyelinated sheath do not cover axons.
What are nodes of ranvier?
Gaps in the myelin sheath that appear at the intervals along the axons between adjacent schwann cell neuroglia
fewer seen in cns (oligodendrocytes)
What function does the myelin sheath have?
It electrically insulates the axons and increases the speed of an impulse conduction.
***oligodendrocytes and schwann cells***
Define nerve impulse
A change of the membranes potential during depolarization and repolarization.
a nerve impulse that communicates with other neurons over long distances.
during the opening of deploarization and hyperpolarization
nerve impulses derived from the environment that communicate with other neurons over short distances.
A graded potential that is able to change a neurons resting membrane to rise past its threshold level of -55mv to +30mv.
a greater outflow of K+ causing the membranes potential to become more negative than the resting membrane level of -70mv.
When the neurons membrane comes back to a resting state of -70mv.
Na+ and K+ are at equallibum
Explain resting membrane potential
When the membrane sees no action potentials and remains at a constant -70 mv.
Describe the conditions that exist across the neuronal membrane during the resting state.
cytosol side of the plasma membrane has more negative ions.
extracellular fluid has more positive ions
keeping the resting membrane at a constant -70mv.
Summarize the events that take place during one action potential.
- a strong graded potential causes the membrane threshold to be met -55mv
- Na+ voltage gates open allowing Na+ to rush into the cell causing the membrane to depolarize at +30mv.
- Na+ gates close
- k+ ion gates open allowing potassium to exit the cell and repolarize the membrane
- K+ gates close
- cell returns to a resting state of -70 mv
Graph changes of events during an action potential within a neuron.
- Resting state:
- voltage channels are closed
- small buildup of negative charges buildup inside of cell
- small buildup of positive charges outside of cell
- Depolarizing state:
- neuron reaches threshold
- voltage Na+ gates open and build up occurs
- channels close
- K+ channels open
- K+ leave the membrane causing resting membrane to become negative within
- repolarization of the resting membrane
- K+ channels close
- restoration of the resting membrane
Explain the action potential all-or-none phenomenom
A resting membrane either reaches a threshold of -55mv, opening Na+ gates or it does not.
What is a stimulus?
A change in the environment that causes a reaction to occur
what is a threshold stimulus?
a membranes potential to reach -55mv and depolarize a neurons membrane to cause an action potential
what are graded potentials?
sensory stimuli impulse signals that vary in amplitude when generating impulses and travel in short distances when communicating with other neurons.
what are receptor potentials?
the amount of a neurotransmitter that binds to a receptor determines the action of the membrane.
What are post synaptic potentials?
A neurons response to a neurotransmitter that may or may not cause a depolarization of the postsynaptic cell.
the change of the membranes voltage as ions flow across the membrane during a depolarization(Na+) or re-polarization(K+).
Compare graded potentials with action potentials.
Graded potentials are:
- stimulated short lived sensory neurons
- that occur within the dendrites
- and communicate with other close neurons.
Action potentials are:
long lived potential impulses that occur along axons and communicate with other neurons at long distances.
What initiates a graded potential in sensory neurons?
stimuli from the environment.
What initiates a graded potential in motor and interneurons?
Define presynaptic neuron
a neuron that carries an impulse to a synapse.
Define postynaptic neuron
a neuron that carries an impulse away from a synapse.
What are EPSP's (excitatory presynaptic potential)?
excited impulses that drive a neurons membrane closer to threshold (more positive).
What are IPSP's (Inhibit post-synaptic potential)?
a hyper polarized membrane that is further from a threshold (more negative).
Describe an electrical synapse
impulses that conduct directly with other neurons through gap junctions, allowing faster communication.
ex. cardiac muscles, smooth muscles, and visceral muscles.
Describe a chemical synapse
an impulse in the presynaptic neuron causes the release of neurotransmitters into the postsynaptic cleft.
Compare excitatory and inhibiting chemical synapsis
Excitatory synapsis causes the postsynaptic membrane to become depolarized and closer to a threshold.
Inhibiting potential causes the postsynaptic membrane to become more hyperpolarized, and further from threshold.
Discuss the role of a neurotransmitter
Neurotransmitters either causes an EPSP or an IPSP of the membrane.
What triggers the release of the neurotransmitters into the synaptic cleft?
a stimuli impulse in a presynaptic neuron
Where are neurotransmitters made and what are they made of?
Neurons cell body and made of amino acids.
Briefly describe the regeneration of neurons.
Regeneration occurs in the pns if the cell body is intact and the schwann cells remain active.
Name the 4 regions of the brain and the subdivisions of each
- brain stem
thalamus and hypothalamus
- medulla oblangata
What is the blood brain barrier?
A mechanism that surrounds the brain and blocks most chemicals from entering
What are the three mengies?
- Dura mater
- Archnoid nater
- pia mater
Describe the Dura Mater mengie.
The outermost part of the brain and spinal cord that adheres to the periosteum of the cranial bones interieor surface. Serves as protection. Made of dense irregular tissue.
Describe the Archnoid Mater
The middle layer of the brain and spinal cord. Made of collagen fibers and some elastic fibers
Describe the pia mater
the innermost layer of the brain and spinal cord, that is thin and translucent. Made of transparent CT and adheres tightly to the brain and spinal cord surface.
What are ventricles within the brain?
Cavities within the brain that are filled with CSF
List the ventricles of the brain.
- Lateral ventricle (on on each side of the hemispheres)
- Third ventricle (located between the lateral ventricles
- Fourth ventricle (under the third ventricle)
What are the functions of the cerebral spinal fluids?
- Mechanical protection--absorbs shock
- chemical protection--keeps an optimal environment for accurate signaling
- circulation blood plasma to the brain and spinal cord
location and functions of the 3 brain stem regions
Relay centers for processing and controlling involuntary reflexes.
- superior caliculi
- corpora quadrigemina for visual tracking
- inferior caliculi has startle reflexes
Pons--bridges of fiber tracks within white matter
medulla oblangata--primary autonomic control center
Describe the circulation of the CSF
- choroid plexuses
- lateral ventricles
- third ventricle
- cerebral aqueduct
- fourth ventricle
- the central and spinal canal
- plasma goes back into the blood stream
Functions of the midbrain
cerebral peduncles--has lots of fiber tracks and serves as a connection point for impulses.
superior caliculi--(2) functions in visual tracking
inferior caliculi--(2) functions as a startle reflex.
Two functions that help control skeletal muscles.
Cerebellum and basal nuclei
Describe the structure and function of the cerebellum.
Highly folded surface that increases the surface are of the gray matter.
primarily helps control skeletal muscle.
List 3 parts of the Diencephalon
Functions of the Epithalamus, Thalamus, Hypothalamus
Thalamus---(made up of the pineal gland and chorozoid plexses) directs sensory info to other areas
hypothalamus-controls the pituitary gland, regulates body temps, produces hormones, and hunger/thirst center
Describe the structure of the cerebrum
- largest part of the brain
- Cerebral cortex--(Gray matter) that contains gyri, sulci, longitudinal fissures, and corpus callosum
Basal nuclei--(clusters of gray and white matter) located deep within the cerebral hemispheres
White matter-- bundles of myelinated axon tracks(association, commisural, projection)
folds of elevated(hills) gray matter ridges that are located in the cerebral cortex region
shallow (valley) grooves between the folds of gray matter
Define longitudinal fissures
Deep groove that separated the two halves into cerebral hemispheres
Define corpus callosum
a brad band of white matter that contains axons with the cerebral hemispheres
What are the lobes of the cerebrum?
What are fiber tracks?
bundles of myelinated neurons that run through white matter for better communication with the commissure region.
what is the function of fiber tracks?
to communicate with other neurons
Compare association tracks, commissure tracks,and projection tracks.
association tracks---conduct impulses within the same hemisphere
commissural tracks--conducts impulses from one hemisphere to another
projection tracks--long axons,conducts impulses from the cerebrum to the lower extremities of the cns
what is the role of the limbic system?
Fight or flight
controls emotional responses
What is the reticular formation?
a net like arrangement of gray and white matter
What is the role of reticular formation?
- filters out sensory information
- maintains consciousness (sensory).
What effects would lesions have on the function of the primary somatory in the brain?
inability to detect stimuli from an area of occurance
What effects would lesions have on the function of the somatory association?
unable to interpret or integrate sensations
What effect would lesions have on the function of primary visual?
blindness in one eye
What effect would lesions have on the function of visual assocation?
inability to relate to present or past visual experinces
What effect would lesions have on the function of primary auditory?
deafness in one ear
What effect would lesions have on the function of auditory assocation?
inability to recognize sounds, music, or noise
What effect would lesions have on the function of primary gustatory?
unable to taste foods
What effect would lesions have on the function of wernickes area?
unable to translate words into thoughts
What effect would lesions have on the function of primary olfactory?
inability to smell odors
What effect would lesions have on the function of primary motor?
paralysis on one side
What effect would lesions have on the function of premotor?
inability to control muscles
What effects would lesions have on the frontal eye fields
eyes would not be able to scan
What effect would be made to the Brocas speech are of the brain?
unable to formulate words into sentences
What is an EEG?
Recording of electrical activity within the brain
List the 4 types of brain waves
What mental state is normally associated with delta waves?
What mental state is normally associated with theta waves?
What mental state is normally associated with alpha waves?
when relaxed and calm
What mental state is normally associated with beta waves?
actively thinking and problem solving
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