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Neuroscience
the multidisciplinary study of the nervous system and its role in behavior
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biopsychology
- the branch of psychology that studies the
- relationship between behavior and the body, particularly the brain. Also known as psychobiology or physiological psychology
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Behavior
- a very broad term that includes internal events such as learning, thinking, and emotion, as well as the overt acts
- everyone would identify as behavior
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When did psychology arise as a discipline?
- 1879 when William Wundt established the
- first psychology laboratory in Leipzig Germany
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mind brain/ mind body problem
- deals with what the mind is and what its
- relationship is to the brain
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monism
- the idea that the mind and the body consist
- of the same substance
idealistic monists believe that everything is nonphysical mind
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materialistic monism
- most monists take the position that the
- body and mind and everything else are physical
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Dualism
- the idea that the mind and the brain are separate. The body is material and the
- mind is nonmaterial
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model
- a proposed mechanism for how something works, sometimes a model is in the form of
- a theory. Can also be a simple organism or system that researchers study in an
- attempt to understand a more complex
- one. Ex: rat
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Rene Descartes explanation of brain activity
- A hydraulic model
o Proposed that nerves were hollow tubes that carried animal spirits
o Said that the pineal gland pumped the animal spirits through the brain
- o it appeared capable of bending at different angels to direct the flow of animal
- spirits into critical areas of the brain. Descartes called it the seat of the
- soul, where the mind interacted with the body.
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pineal gland
attached just below the two cerebral hemispheres by its flexible stalk
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Empiricism
- gather information through observation
- rather than logic intuition, or other means
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Luigi Falvani
- late 1700’s made a frogs leg muscle twitch by stimulating the attached nerve with
- electricity, even after the nerve and muscle had been removed from the body
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1800’s Frtich and Hitzig
- produced movement in dogs by electrically stimulating their exposed brains
o Each of these cases showed that nerves operated by electricity
- o After, Hemholtz demonstrated that nerves do not behave like wires conducting
- electricity. Measured the speed of conduction in nerves, and his calculation of
- about 90 feel/second
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Localization
- the idea that specific areas of the brain carry out specific functions
o Functions are as much distributed as they are localized
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phrenology
- each of 35 different faculties of emotion
- and intellect- such as combativeness,
- inhabitiveness (love and home), calculation, and order – was located in a
- precise area of the brain
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Equipotentionally
- the idea that the brain functions as an undifferentiated whole. The extent of
- damage, not the location, is what determines how much function is lost
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gene
- a biological unit that directs cellular processes and transmits inherited
- characteristics. Most genes are found on the chromosomes, which are located in
- the nucleus of each cell
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Mitochondria
few genes in structures outside the nucleus
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body cells
- - 46 chromosomes in 23 pairs. Genes for
- specific functions are found on specific chromosomes. Referred to by number,
- except for the sex chromosomes. All pairs are similar except for the sex
- chromosomes – y is much shorter than x
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How many chromosomes do sex cells have?
23
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Deoxyribonucleic acid (DNA)
- a double stranded chain of chemical molecules that looks like a ladder that has
- been twisted around itself. Also known as the double helix
- o Composed of adenine, thymine, guanine, and cytosine – the order that these appear on the ladder forms the code that carries all our genetic information
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What do proteins do?
- - Genes make proteins, some of these proteins are used in the construction of the body, and others are enzymes; enzymes act
- as caralysts, modifying chemical reactions in the body
o Because chromosomes are paired, most genes are as well
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Allele
- different versions of a gene
- o ex: an
- allele for type A blood on one chromosome and the allele type B blood on the
- other will have AB blood
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Phenotype
A characteristic
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Human Genome
all the genes in our chromosomes
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How many different combinations of chromosomes can a parent produce?
8 million
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heritability
- – the percentage of the variation in a characteristic that can be attributed to
- genetic factors
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Neurons
- specialized cells that convey sensory information into the brain; carry out the operations involved in thought, feeling, and action;and transmit commands out into the
- bnody to control muscles and organs
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How many neurons are in the brain?
100 billion
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What makes up the brains cells?
10% neurons 90% glial cells
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cell body/soma
- the most prominent part of the neuron. Filled with a watery liquid called cytoplasm
- and contains a number of organelles. The largest organelle is the nucleus,
- which contains the cells chromosomes
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What are some responsibilities of organelles?
- Converting nutrients into fuel for the cell, constructing proteins, and removing waste
- materials
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Motor Neuron
carries commands to the muscles and organs
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Dendrites
- extensions that branch out from the cell body to receive information from other neurons.
- Branchlike structures allow them to collect information from many neurons
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Axon
extends like a tail from the cell body and carries information to other locations
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What does Myelin sheath do?
- supports the axon and provides other
- benefits that we will consider later.
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terminals
- contain chemical neurotransmitters which the neuron releases to communicate with a
- muscle or an organ or the next neuron in a chain
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sensory neurons
- carry information from the body and from the outside world into the brain and spinal
- cord. Can be either unipolar or bipolar
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Why is a motor neuron also known as a multipolar neuron?
- Its axon and dendrites extend in several
- directions from the cell body
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interneurons
connect one neuron to another in the same part of the brain or spinal cord. Because they make connections over short distances they don’t need long axons
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What is the most critical factor in the neurons ability to communicate?
The membrane that encloses the cell
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What are some molecules that can pass through the cell membrane?
Water, oxygen, and carbon dioxide
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polarization
- there is a difference in electrical charge between the inside and the outside of the
- cell. Difference between two points is called voltage
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Resting Potential
- the
- difference in charge between the inside and outside of the membrane of a neuron
- at rest. The voltage is negative and varies anywhere from -40 to -80 millivolts
- (mV) in different neurons but is typically around -70. Result from charges from
- ions
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What makes the resting potential of a neuron negative
- The inside of the neuron has more negative
- ions than positive ions, while the ions on the outside are mostly positive
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Why do ions move through the membrane to the side where they are less concentrated?
The force of diffusion
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What is a result of electrostatic pressure?
- Ions are repelled from the side that is similarly charged and attracted to the side
- that is oppositely charged
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Sodium potassium pump
- consists of large protein molecules that
- move sodium ions through the cell membrane to the outside and potassium ions
- back inside. Metabolic process (uses energy)
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Action Potential
- an abrupt depolarization of the membrane that allos the neuron to communicate over
- long distances
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What is the voltage across the resting neuron?
Stored energy
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What happens at the peak of action potential?
- The sodium channels close, so there is no
- further depolarization. By that time the potassium ions inside the membrane
- combine to move potassium ions out. This outward flow of potassium ions returns
- the axon to its resting potential
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How does the action potential differ from the local potential?
- The local potential is a graded potential, which means that it varies in magnitude
- with the strength of the stimulus that produced it. The action potential on the
- other hand is ungraded. It operates according to the all or none law. Meaning
- that it occurs at full strength or not at all
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How is action potential nondecremental?
- It travels down the axon without any decrease in size, propagated anew and at full
- strength at each successive point along the way, which allows the neuron to
- work over long distances.
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Absolute refractory period
- right after the action potential occurs the is a brief time during which it
- cannot fire again. Occurs because the
- sodium channels cannot reopen
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Relative refractory period
- the neuron can be fired again, but only by a stronger than-threshold stimulus. A
- stimulus that is greater than threshold will cause the neuron to fire again
- earlier and thus most frequently
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Rate Law
- the axon encodes stimulus intensity not
- in the size of its action potential but in its firing rate
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Glial Cells
- nonneural cells that provide a number of
- supporting functions to neurons. Glial = glue
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Myelination
- –
- glial cells produce myelin, a fatty tissue that wraps around the axon to
- insulate it from the surrounding fluid and from other neurons. Only the axon is
- covered, not the cell body. Myelin is produced in the brain and spinal cord by
- a type of glial cell called oligodendrocytes and in the rest of the nervous
- system by schwann cells
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Can action potentials occur in the myelin sheath?
No because there are very few sodium channels there.
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What are the gaps in the myelin sheath called?
Nodes of Ranvier
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Salutatory conduction
form of transmission when action potentials jump from node to node
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How did Santiago Ramon y Cajal find that each neuron is a separate cell
Tissue staining method
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Synapse
the connection between two neurons
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What did loewi demonstrate about transmission?
- That transmission at the synapse is chemical and that there are at least two
- different chemicals that carry out different functions
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Vesicles
- membrane enclosed containers that store neurotransmitters. When the action potential arrives at the terminals, it opens that channels that allow calcium ions o
- enter the terminals from the extracellular fluid.
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Ionotropic Receptors
- open the channels directly to produce the immediate reactions required for muscle
- activity and sensory processing; metabotropic receptors open channels indirectly and slowly to produce longer lasting effects
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What effects can opening ion channels on the dendrites and cell body have?
- It can cause the local membrane potential
- to shift in a positive direction toward zero, partially depolarizing the membrane or it can shift the potential farther in the negative direction.
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Partial depolarization, or hypopolarization
is excitatory and facilitates the occurrence of an action potential
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Increased polarization or hyperpolarization
- inhibitory and makes an action potential
- less likely to occur
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How many mVs does it take for depolarization to trigger and action potential?
10 mV
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How many synaptic connections are in the brain?
- 10000 in most parts of the brain and up to
- 100000 in the cerebellum.
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Spatial summation
- combines potentials occurring simultaneously at different locations on the dendrites and
- cell body
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Temporal summation
- combines potentials arriving a short time apart. Possible because it takes a few
- milliseconds for a potential to die out
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Peptides
- chains of amino acids (longer chains are called proteins). Neuropeptides are peptides
- that act as neurotransmitters.
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Acetylcholine
- transmitter at muscles; in brain involved
- in learning etc. neurotransmitter
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Serotonin
involved in mood, sleep,and arounsal and in aggression,depression, obsessive-compulsive disorder and alcoholism. Monamine
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Dopamine
contributes to movement control and promotes reinforcing effects of abused drugfs, food, and sex; involved in schizophrenia and Parkinson’s disease. Moamine
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Norepinephrine
- a hormone released during stress.
- Functions as a neurotransmitter in the brain to increase arousal and attentiveness to events in the environment; involved in depression. Monamine
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Epinephrine
a stress hormone related to norepinephrine; plays a minor role as a neurotransmitter in the brain. Monamine
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Glutamate
- the principal excitatory neurotransmitter in the brain and spinal cord. Vitally
- involved in learning and implicated in schizophrenia. Amino acid
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Gamma-aminobutyric acid (GABA)
- the predominant inhibitory neurotransmitter. Its receptors respond to alcohol and
- the class of tranqulizers called benzodiazepines. Deifiency in GABA or
- receptors is one cause of epilepsy. Amino acids
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Glycine
- inhibitory transmitter in the spinal cord and lower brain. The posion strychnine causes
- convulsions and death by affecting glycine activity. Amino acids
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Endorphins
neuromodulators that reduce pain and enhance reinforcement. Peptides
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Substance P
transmitter in neurons sensitive to pain. Peptides
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Neuropeptide Y
initiates eating and produces metabolic shifts. Peptides
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Neural Networks
- groups of neurons that function together to carry out a process. Where the most
- complex neural processing is carried out
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Lissencephalic
smooth brained
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Central nervous system (CNS)
includes the brain and the spinal cord
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Nerve
- a bundle of axons running together like a multiwire cable – this term is only
- used in the peripheral nervous system, inside the CNS bundles of axons are
- called tracts
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What is a group of bodies called in the CNS and the Peripheral Nervous System?
- CNS = nucleus PNS = ganglion
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What are the major structures of the forebrain?
- The two cerebral hemispheres, the thalamus,
- and the hypothalamus
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Where does the highest level processing occur in the brain?
The cortex- the outer layer of the hemispheres
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Longitudinal fissure
runs the length of the brain and separates the two cerebral hemispheres
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convoluted
- the ridges and grooves that give the brain
- a wrinkly appearance
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Gyrus
each ridge in the brain
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Sulcus
the groove or space between two gyri, if it is large it is called a fissure
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How thick is the cortex?
1.5-4 millimeters thick
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How many layers are in the brain?
6
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The frontal lobe
the area anterior to (in front of) the cenral sulcus and superior to (above) the lateral fissure
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The coronal plane
divides the brain vertically from side to side
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The precentral gyrus
extends the length of the central sulcus, is the location of the primary motor cortex, which controls voluntary (nonreflexive) movement
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Broca's Area
controls speech production, contributing the movements involved in speech and grammatical structure
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Prefrontal Cortex
- the largest region in the human brain (29% of the brain) involved in planning and
- organization, impulse control, adjusting behavior in response to rewards and
- punishments, and some forms of decision making
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Lobotomy
- a surgical procedure that disconnects the
- prefrontal area from the rest of the brain
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Psychosurgery
- the use of surgical intervention to treat cognitive and emotional disorders, is
- generally held in disfavor
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Parietal Lobes
- located superior to the lateral fissure
- and between the central sulcus and the occipital lobe
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The primary somatosensory cortex
- located on the postcentral gyrus, processes
- the skin senses (touch, warmth, cold, and pain) and the senses that inform us
- about body position and movement. Usually serves the opposite area of the body
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What happens when the posterior parietal cortex is damaged?
- May produce neglect, a disorder in which
- the person ignores objects, people, and activity on the side opposite the
- damage. Occurs more frequently when the right side is damaged
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Primary projection area
in occipital lobes. Occupies the posterior tip of each lobe, anterior to the primary area are four secondary areas that detect individual components of a scene, such as color, movement, and form, which are then combined in association areas
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Thalamus
lies just below the lateral ventricles, where it receives information from all the sensory systems except olfaction and relays it to the respective cortical projection areas
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hypothalamus
a smaller structure just inferior to the thalamus, plays a major role in controlling emotion and motivated behaviors such as eating, drinking, and sexual activity. Controls the autonomic nervous system and the pituitary gland (hormonal environment)
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Pituitary Gland
- known as the master gland because its
- hormones control other glands in the body
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Pineal Gland
- secretes melatonin, a hormone that induces sleep. It controls seasonal cycles in
- nonhuman animals and participates with othe strctures in controlling daily
- rhythms in humans
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Corpus Callosum
a dense band of fibers that carry information between the hemispheres
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What does each hemisphere specialize in?
left: language (language activity is mostly controlled by the left in 9 out of10 people) right: spatial tasks and face recognition
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Ventricles
cavities in the brain andcentral canal in the spinal cord. Filled with cerebrospinal fluid, whichcarries material from the blood vessels to the CNS and transports wastematerials in the other direction
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Midbrain
contains structures that havesecondary roles in vision, audition, and movement
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Superior colliculi
help guide eyemovements and fixation of gaze and the inferior colliculi help locate thedirection of sounds
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Pons
contain centers related to sleep and arousal, which are part of the reticular formation
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Reticular formation
a collection of manynuclei running through the middle of the hindbrain and the midbrain
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Medulla
forms the lower part of thehindbrain; its nuclei are involved with control of essential life processes,such as cardiovascular activity and respiration
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How do sensory neurons enter the spinal
cord?
Through the dorsal root of each spinal nerve
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Reflex
an automatic movement in responseto a sensory stimulus
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Peripheral nervous system (PNS)
made upof the cranial nerves, which enter and leave the underside of the brain
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Spinal nerves
connect to the sides of thespinal cord at each vertebra
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Somatic nervous system
includes the motorneurons that operate the skeletal muscles
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Automatic nervous system (ANS)
controlssmooth muscle (stomach, blood vessels, etc) the glands, and the heart and otherorgans
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Sympathetic nervous system
activates thebody in ways that help it cope with demands such as emotional stress andphysical emergencies
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Parasympathetic nervous system
slows theactivity of most organs to conserve energy and activates digestion to renewenergy
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What are the four stages of the development
of the nervous system?
Cell proliferation, migration, circuit formation, andcircuit pruning
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Proliferation
cells that will becomeneurons divide and multiply at the rate of 250,000 new cells every minute
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Migration
newly formed neurons migratefrom the ventricular zone outward to their final location. Do so with the aidof specialized radial glial cells
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Circuit formation
the axons of developingneurons grow toward their target cells and form functional connections
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Circuit pruning
involves the eliminationof excess neurons and synapses
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Neurotrophins
chemicals that enhance the development and survival of neurons
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Regeneration
the growth of severed axons
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Hydrocephalus
occurs when the circulationof cerebrospinal fluid is blocked and the accumulating fluid interferes withthe brain’s growth producing severe intellectual impairment
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Stem cells
undifferentiated cells thatcan develop into specialized cells such as neurons, muscle, or blood
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How does action potential work?
The actionpotential causes nearby sodium channels to open as well. A new action potentialis triggered right next to the first one. A signal flows from one end of theneuron to the other
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