Week 2 (Exam 2): The Nervous System Flashcards
what are the components of the central nervous system?
brain & spinal cord
what are the components of the peripheral nervous system
nerves that extend from the central nervous system to the muscles, skin, & organs
what is the function of the peripheral nervous system?
send info towards the CNS
cranial nerves
one of 12 paired nerves that emerge from the brain
-involved in many sensory functions
spinal nerves
run from the spinal cord to the periphery containing axons of both sensory & motor neurons
what is the somatic (voluntary) component of the peripheral nervous system
-sensing & responding to external stimuli
-made of sensory neurons that respond to external stimuli & motor neurons that synapse w/ voluntary muscles
what is the autonomic (involuntary) component of the nervous system?
- controls internal functions of the body
-organized into sympathetic & parasympathetic divisions
sympathetic division of the autonomic nervous system function
produces arousal & increased activity
-active in fight-or-flight response
parasympathetic division of the autonomic nervous system
enables the body to “rest & digest”
knee-extension reflex
involves a single synapse between a sensory neuron & a motor neuron
-activates the extensor muscles, causing the bent leg to straighten
reciprocal inhibition
the activation of opposing sets of muscles so that one set is inhibited as the other is activated, allowing the movement of joints such as the knee
hindbrain function
controls basic body functions & behavior along with the midbrain
midbrain function
controls basic body functions & behaviors as well as the hindbrain
forebrain function
governs cognitive functions (cerebral cortex, thalamus, hypothalamus)
cerebral cortex function
a portion of the forebrain that is greatly expanded in mammals
-the largest part of the brain overseeing sensory perception, memory, & learning
what does the hindbrain develop into
the cerebellum & part of the brainstem
cerebellum function
coordinates complex motor tasks by integrating motor & sensory info
brainstem function
activates the forebrain by relaying info from lower spinal levels
-consists of medulla, pons, & midbrain
medulla function
inner layer of the mammalian kidney & adrenal gland
pons
part of the brain stem
thalamus function
the inner brain region of the forebrain
-relay station for sensory information sent to the cerebrum
hypothalamus function
the underlying brain region of the forebrain, which interacts w/ the autonomic & endocrine systems to regulate the general physiological state of the body
cerebrum function
the outer left & right hemispheres of the cerebral cortex
cerebral cortex function
the largest part of the brain, overseeing sensory perception, memory, & learning
limbic system function
inner components of the forebrain that control physiological drives, instincts, emotions, motivation, spatial memory, & sense of reward
hippocampus function
posterior region of the limbic system within the mammalian brain involved in spatial cognition & long-term memory function
what parts of the brain does signal go through sequentially
sensory info —> cerebral cortex —> brainstem —> thalamus —> specific brain region
gray matter
densely packed neuron cell bodies & dendrites that make up the cortex, a highly folded outer layer of the mammalian brain that’s about 4 mm thick
white matter
the axons of cortical neurons in the interior of the vertebrate brain & spinal cord; the fatty myelin produced by glial cells surrounding the axons make it white
sulci
deep crevices in the brain that separate the lobes of the cerebral hemispheres
frontal lobe
the region of the brain located in the anterior region of the cerebral cortex, important in decision making & planning
parietal lobe
posterior to the frontal lobe that controls body awareness & the ability to perform complex tasks
temporal lobe
the region of the brain involved in the processing of sound, language & reading, & object identification & naming
occipital lobe
processes visual info from the eyes
central sulcus
separates the primary motor cortex of the frontal lobe from the primary somatosensory cortex of the parietal lobe
primary motor cortex
produces complex coordinated behaviors by controlling skeletal muscle movements
primary somatosensory cortex
integrates tactile info from specific body regions & relays it to the motor cortex
step 2 of a chemical synapse
depolarization of the axon terminal opens voltage-gated Ca2+ channel
step 3 of a chemical synapse
vesicles fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft
step 4 of a chemical synapse
neurotransmitters bind with receptors on the postsynaptic cells that are ligand-gated ion channels, opening a change in membrane potential
step 5 of a chemical synapse
neurotransmitters are actively reabsorbed into the presynaptic terminal & stored in vesicles until the next action potential arrives
step 1 of a chemical synapse
action potential travels to the action terminal
nervous system
a network of many interconnected nerve cells
which animals first evolved to have a nervous system
jellyfish & flatworms
-became more elaborate as animals evolved specialized nervous systems
neurons
the functional units of the nervous system
3 types of neurons
sensory neurons, interneurons, & motor neurons
sensory neuron function
receive & transmit info about an animal’s environment or its internal psychological state
-respond to physical features of the environment (temp, light, & touch or to chemical signals such as odor & taste)
interneurons
processes info received by sensory neurons & transmits it to motor neurons
motor neurons
signals a muscle or gland to cause a response in the body
ganglia
a group of nerve cell bodies that processes sensory information received from a local region, resulting in a signal to motor neurons that control some physiological function of the animal
-relay stations in nerve cell circuits
-assist in processing information from the eyes & controlling the digestive state of an animal’s gut
brain
the complex organ located in the head that processes sensory stimuli from the environment & the body, sends motor signals to the body, & controls thought, emotions, & other processes
which animal lacks a nervous system
sponges
which animal has the simplest nervous system
cnidarians
-made up of neurons arranged like a net (no ganglia or central brain)
which group of animals has the most complex nervous system
bilaterians
nerves
a bundle of long fiberlike extensions (axons) from multiple nerve cells
-exist in animals with an organized nerve system
paired ganglia
help regulate key processes in local regions & organs of the animal’s body
what resulted from the evolution of brains?
vertebrates developed complex behaviors, learning, and memory
dendrites
fiberlike extensions from the cell body of a neuron that receives signals from other nerve cells or from specialized sensory endings
axons
the fiberlike extensions from the cell body of a matrix that transmit signals away from the nerve’s cell body
first step of neuron organization
stimuli are received by the dendrites & cell body
second step of neuron organization
synaptic stimuli are summed at the axon hillock, where an axon potential is triggered if the sum of the arriving signals is high enough
third step of neuron organization
axon potentials are conducted to the axon terminal, where they cause the release of neurotransmitters that are stored in vesicles
-these bind to receptors on the postsynaptic cell membrane, creating a new signal in the postsynaptic neuron
axon hillock
the junction of the nerve cell body and its axon, which initiates an action potential
action potential
a brief membrane electrical signal transmitted from the nerve cell body along one or more axons
synapse
a junction through which the axon terminal of a nerve cell communicates with a neighboring cell
synaptic cleft
separates the end of the axon of the presynaptic cleft & the neighboring postsynaptic cell
neurotransmitters
a molecule that conveys a signal from the end of an axon to the postsynaptic target cell, such as another neuron or a muscle fiber
what triggers the release of neurotransmitters from vesicles at the terminal?
the arrival of a nerve signal at the axon terminal
how is the strength of a signal determined?
the frequency of signals
information integration
the process of bringing together information gathered from different sources
glial cells
a type of cell that surrounds neurons & provides them with nutrition & physical support
endothelial cells
linked by tight junctions to form the blood-brain barrier that limits the type of compounds that can diffuse from the blood into the brain
blood-brain barrier
prevents pathogens & toxic compounds in the blood from entering the brain
how fast do neuron signals travel?
up to 450 mph
what is significant about the inside & outside surfaces of a neuron?
they carry opposite & unequal charges
membrane potential
a difference in electrical charge across the cell membrane
what is the key to producing an electrical signal in a neuron?
the movement of ions across the membrane
resting membrane potential
the negative voltage across a cell membrane at rest
what is the ratio of Na+ to K+ transfer
3 Na+ ions moved outside for every 2 K+ ions moved inside
what happens to the membrane potential when a nerve cell is excited?
it becomes less negative than the outside of the cell
depolarization
an increase in membrane potential from a negative resting potential
-starts at the end of the dendrite in response to neurotransmitter binding to membrane receptor
-travels cell body
-loses strength
-if depolarization is strong enough at the axon hillock, the cell fires an action potential
threshold potential
the critical depolarization voltage of -55 mV required for an action potential
first stage of an action potential
summed input depolarizes the cell membrane at the axon hillock above the threshold potential
second stage of an action potential
voltage-gated Na+ channels open & Na+ rapidly enters the cell, causing a potential spike in the membrane potential
third stage of an action potential
as the voltage rises to 40 mV, Na+ channels close & are inactivated, & voltage-gated K+ channels remain open, allowing K+ ions to leave the cell and causing the membrane potential to become more negative
fourth stage of an action potential
an overshoot in K+ ions leaving the cell makes the cell membrane hyperpolarized, resulting in a refractory period
fifth stage of an action potential
gradually the membrane returns to resting, as excess K+ ions are returned to the cell, assisted by Na+ - K+ pump
positive feedback
the output/product of a pathway enhances the initial stimulus, leading to larger and larger response
-self-reinforcing
refractory period
the period following an action potential during which the inner membrane voltage falls below & then returns to the resting potential
how do action potentials move along axons?
by sequentially opening & closing adjacent ion channels
what is the conduction speed of action potentials limited by?
the neuron’s membrane properties & the diameter of its axon
myelin
fatty insulating layers surrounding the axons of vertebrate neurons, produced by glial cells, that speed up the propogation of action potentials
nodes of Ranvier
lie between adjacent myelin-wrapped segments, where the axon membrane is exposed
saltatory propogation
the movement of an action potential along a vertebrate myelinated axon “jumping” from node to node
two types of synapses
electrical or chemical
electrical synapses
provide direct electrical communication through gap junctions
first step of a chemical synapse
synaptic transmission begins with action potential conduction to the axon terminal
second step of a chemical synapse
depolarization of the axon terminal opens voltage-gated Ca 2+ channels
third step of chemical synapses
vesicles respond by fusing with presynaptic membrane, releasing neurotransmitters into the synaptic cleft
fourth step of chemical synapses
neurotransmitters bind with receptors on the postsynaptic cell that are ligand-gated ion channels, opening the channels to allow in ions & causing a change in membrane potential
fifth step of chemical synapse
neurotransmitters are actively reabsorbed into the presynaptic terminal & stored in vesicles until the next action potential arrives
ligand-gated ion channels
a receptor that alters the flow of ions across the cell membrane when bound by its ligand
excitatory postsynaptic potential (EPSP)
a positive change in the postsynaptic membrane potential
hyperpolarization
making a membrane potential more negative
inhibitory postsynaptic potential (IPSP)
a negative change in the postsynaptic membrane potential
when does a postsynaptic nerve cell fire an action potential?
only if the combined EPSPs and IPSPs exceed the threshold at the axon hillock
temporal summation
the summation of postsynaptic potentials over time, which determines whether the postsynaptic cell fires an action potential
spatial summation
the converging of multiple receptors onto a neighboring neuron, increasing its firing rate proportionally to the number of signals received
stretch receptors in the knee extensor muscles stimulated by the tap of a physician’s reflex hammer just below the knee cap directly triggers a nerve impulse in which answer choice?
a sensory neuron
what is inhibited following a tap of the physician’s reflex hammer just below the knee cap?
motor neurons of the knee flexor muscle
the interneuron in the spinal cord triggers what?
an inhibitory stimulus that prevents contraction of the knee flexor muscles
how many synapses are involved in the contraction of the knee extensor muscles in the knee-jerk reflex?
1
how many synapses in total are involved in the knee-jerk reflex?
3
a neuron’s ability to generate action potentials depends
on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to enter the axon
at the moment that the action potential has reached its maximum height, the potential (or voltage) difference across the nerve membrane is
more positive inside than out
under normal (resting) cellular conditions, the ______ concentration is greater inside the cell, and the plasma membrane is most permeable to _____
potassium; potassium
______ concentration is always higher outside the cell. during the peak of the peak of the action potential, the plasma membrane is becoming more permeable to ______
sodium; potassium
in a typical neuron, what happens during an action potential when a voltage-gated potassium channel opens?
potassium leaves cell, cell repolarizes
what happens when a neuron is depolarized?
sodium ions enter the neuron through voltage-gated sodium channels
transmission of impulses along a neuron in the vertebrate nervous system ordinarily occurs in only one direction because, following passage of an action potential, the neuron is temporarily in a refractory period or hyperpolarized. this is caused by…
the movement of potassium out of the axon
in vertebrates, the speed of transmission along a neuron can be increased by…
myelinating the axon
in vertebrates, the speed of transmission along neurons is much faster in myelinated neurons. what is not true of transmission along myelinated & unmyelinated neurons?
saltatory conduction in non-myelinated neurons slows the process of tranmission
action potentials typically move in one direction along the neuron away from the cell body due to…
the temporary hyperpolarization of the axon membrane following the action potential spike
when an action potential reaches the axon terminal…
neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either an inhibitory hyperpolarization or an excitatory depolarization
what causes the increase in cytosolic calcium that triggers the fusion of secretory vesicles to the membrane and the release of neurotransmitters into the synaptic cleft?
the change in conformation of voltage-gated calcium channels in the axon terminal membrane
what determines whether or not an action potential is triggered in the postsynaptic neuron
the overall net change in membrane potential caused by the combined EPSPs and IPSPs
what could be inhibited by greatly decreasing extracellular calcium?
the fusion of secretory vesicles with the presynaptic plasma membrane
true/false: although animal nervous systems differ in complexity, their nerve cells are still remarkably similar
true
membrane potential is determined by…
the difference in concentration of ions and charged molecules on the two sides of a cell’s plasma membrane
true/false: ganglia were the evolutionary precursor to the centralized concentration of neurons that we now call a brain
true
the release of neurotransmitter from the presynaptic cell is an example of…
exocytosis
what part of a cell’s cytoplasm is responsible for the diversity of nerve cell shape?
the cytoskeleton
what would happen to a neuron’s resting membrane potential if the number of sodium ion leak channels increased?
the membrane potential would become more positive
true/false: IPSPs are associated with depolarization, wheras EPSPs are associated with hyperpolarization
false
what class of membrane-transport protein is associated with triggering an action potential?
a voltage-gated ion channel
the interior or a neuron is more negative than the outside due to the presence in the interior of…
proteins and chloride ions
why does an action potential travel down one direction down an axon?
because voltage-gated sodium ion channels cannot immediately reopen after depolarization due to the refractory period
how can low levels of calcium harm an individual?
low levels of calcium would result in fewer signals sent between the presynaptic and postsynaptic cell
temporal summation is a response to the
frequency of stimulation of a postsynaptic cell
which portion of the forebrain regulates the endocrine system and body temperature?
hypothalamus
true/false: all neurons have either a sensory or motor function
false
body functions such as heart rate, blood flor, and digestion are controlled by the
autonomic nervous system
the signal to “rest and digest” comes from the
parasympathetic system
which brain region controls drives, instincts, and emotion?
limbic system
memory and learning take place in which area of the brain?
cerebrum and hippocampus
which brain region is associated with language in humans?
temporal lobe
which region of the brain is larger in humans and primates than in other vertebrates?
cerebral cortex
which portion of the forebrain regulates the endocrine system and body temperature?
hypothalamus
what symptoms might you see if a person suffered a stroke in their cerebellum?
loss of balance and coordination
