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What structures make up the nervous system?
the brain, spinal cord, nerves, neural support cells, and certain sensory organs (eye, ear)
What is the functional unit of the nervous system?
neuron
What are the major structures of the neuron?
several dendrites, a single branched axon, and cell body (soma)
What describes the regenerative capabilities of neurons?
they cannot divide
What substances are neurons highly dependent upon for chemical energy?
glucose
neurons use what process to move glucose from the blood into the cell?
facilitated transport
(Note: not uniquely dependent on insulin for this transport)
What describes how neurons store nutrients?
contain low stores of glycogen and oxygen
(Note: depend on blood mostly for these nutrients)
What is the structure where the soma connects to the axon called?
axon hillock
(Note: action potentials are generated here)
What structure receives information and transfers it to the cell body in the neuron?
dendrites
What structure transfers impulses away from the cell body in the neuron?
axon
What distinguishes gray and white matter?
white: myelinated axons
gray: neuronal cell bodies (no myelin)
What category of nervous tissue cells are capable of cell division?
glial cells
Which glial cells produce myelin in the central nervous system (CNS)?
oligodendrocytes
Which glial cells produce myelin in the peripheral nervous system (PNS)
Schwann cells
What are the fatty sheaths that act as insulators in the nervous system?
myelin sheaths
Myelin sheaths are separated by what divisions?
nodes of Ranvier
The nodes of Ranvier allow the action potential to do what?
travel continuously down the axon jumping from node to node
(Note: this process is called saltatory conduction, which speeds up the impulse)
What is the only type of animal that has myelinated axons?
vertibrates
What are the phagocytes of the CNS?
microglia
What cells use cilia to circulate cerebrospinal fluid
ependymal cells
What are groups of cell bodies in the PNS that serve as support cells?
satellite cells
What is a kind of satellite cell that provides physical support to neurons of the CNS and maintains the mineral and nutrient balance?
astrocytes
What are the three types of neurons important to the DAT?
sensory (afferent) neurons
association (interneuron) neurons
motor (efferent) neurons
What kind of neuron receives the initial stimulus from the brain (ex: neurons in the skin)?
sensory (afferent) neuron
What kind of neuron is located in the spinal cord and brain, and receives impulses from sensory neurons and sends impulses to motor neurons?
association (interneuron) neuron
Which neurons are integrators as they evaluate impulses for the appropriate response?
association (interneuron) neuron
What percentage of neurons are interneurons?
99%
In which neural pathway are interneurons often found?
reflex arcs
(Note: note required for reflex arc though)
What neurons travel from the brain/spinal cord and stimulate effectors?
motor (efferent) neurons
(Note: May stimulate muscles, sweat glands, or cells in the stomach to secrete gastrin
What are target cells that elicit some response?
effectors
What is an electrical signal that is transmitted along a nerve fiber, allowing us to send signals to perform actions like raising an arm to catch a ball or recoiling a hand when touching a hot stove.
nerve impulse
What is the mechanism behind a nerve impulse?
polarized neurons
(Note: high concentration of Na+ is presented outside the cell and a high concentration of K+ inside)
What channel maintains the resting potential of a neuron?
Na+/K+ ATPase pump
(Note: 3Na+ are pumped out for every 2K+ brought in, resulting in the net removal of one positive charge from the intracellular space)
What are the steps of nerve impulse transmission?
resting potential
action potential
repolarization
hyperpolarization
refractory period
What is the typical resting potential of a neuron?
-70 mV
What is the first step of an action potential?
a stimulus causes gated ion channels to open and Na+ ions enter the axon, depolarizing the neuron.
What measure needs to be reached in order for an action potential to occur?
the threshold level, which is around -50 mV
(Note: if the threshold level is not reached, no action potential occurs!)
What is the direct result of the threshold level being reached in terms of ion channels?
opening of voltage gated Na+ channels down the entire length of the neuron
(Note: All or nothing event!)
What happens during the repolarization phase in terms of ion channels?
in response to the Na+ flow in, more gated ion channels let K+ out of the cell, restoring polarization
Which ions are in and which ions are out after repolarization?
Na+ are now IN and the K+ are OUT!
What describes hyperpolarization in terms of ions?
too much K+ is released (~ -80 mV)
What term describes the period where the neuron will not respond to a new stimulus until Na+/K+ pumps return the ions to their resting potential locations?
refractory period
What term describes when Na+ channels are inactivated and there is no chance of responding to a new stimulus?
absolute refractory period
(Note: sets an upper limit to action potential frequency)
What period is it called when an abnormally large stimulus can create an action potential after the absolute refractory period?
relative refractory period
What is the function of the refractory period?
prevents an action potential from moving backwards
What metric is related to the frequency of action potential firing, or how many nervous cells contribute to result in the action potential?
strength of a neural signal
What is the name of the ion channel that will close in the presence of ATP, causing K+ to be unable to escape?
K-ATP sensitive channel
(Note: when exposed to ATP, this event causes depolarization, activating voltage dependent calcium channels (VDCC) to open, which results in the exocytosis of insulin)
What is the event called when a signal travels from a pre-synaptic neuron to a post-synaptic neuron?
signal transmission
What are the two types of signal transmission in the nervous system?
electrical and chemical
Which type of signal transmission is a bidirectional action potential
electrical
Which type of signal transmission is a unidirectional action potential that is most typical in animal cells?
chemical
Over what kind of membrane does an electrical transmission occur?
gap junction
In what tissues is electrical signal transmission common?
cardiac and visceral smooth muscle
What are the steps of transmission across a synapse?
Ca 2+ gates open
synaptic vessels release neurotransmitter
neurotransmitter binds with post-synaptic receptors
post-synaptic membrane is either excited or inhibited
Neurotransmitter is degraded/ recycled/diffused away
When the Ca 2+ gates open during synaptic transmission, what event allows Ca2+ to enter the cell via VDCC's (are also found in beta cells!)?
depolarization
Influx of calcium ions during synaptic transmission causes what event?
release of neurotransmitters into the synaptic cleft
By what mechanism do neurotransmitters diffuse across the synapse during synaptic transmission?
brownian motion
In synaptic transmission, what is the result called when Na+ gates open and the membrane is depolarized, allowing an action potential to be generated if threshold potential is succeeded?
excitatory post synaptic potential (EPSP)
In synaptic transmission, what is the result called when K+ gates open and the membrane is hyperpolarized, making it more difficult to generate an action potential?
inhibitory post synaptic potential (IPSP)
What are the mechanisms in which neurotransmitters can be cleared from the synapse?
broken down by enzymes in the cleft
reuptaken
diffused
What are the factors that alter the rate at which impulses travel?
diameter
myelination
Which type of diameter will allow an action potential to travel faster?
larger diameter
(Note: less resistance to flow of ions)
Which type of myelination will allow action potential to travel faster?
more myelination
(Note: Na+ ions can't leak out, thereby driving saltatory conduction to occur faster)
What neurotransmitter is secreted at neuromuscular junctions and cause muscle contraction or relaxation?
Acetylcholine (Ach)
In the parasympathetic nervous system, Ach is released from which nerves?
pre and post ganglionic nerves
What enzyme breaks down Ach?
acetylcholinesterase
(Note: terminates the signal)
In what tissues is Ach found?
nerve tissue
muscle tissue
(Note: both central and peripheral tissues)
In which nerve fibers is Ach found?
sensory and motor fibers
What neurotransmitter is located at the neuromuscular junction in invertebrates?
Glutamate
(Note: most common CNS neurotransmitter in vertebrates. Is an amino acid)
What neurotransmitter is the inhibitory neurotransmitter among brain neurons
Gamma aminobutyric acid (GABA)
(Note: amino acid)
What neurotransmitter is the inhibitory neurotransmitter among synapses of the CNS outside the brain?
Glycine
(Note: amino acid)
What are the Amino acid-derived neurotransmitters (biogenic amines) that are secreted between neurons of the CNS?
epinephrine, norepinephrine, dopamine, and serotonin (5HT)
In which system do epinephrine/norepinephrine act?
sympathetic nervous system
From what nerves are epinephrine/norepinephrine released?
post ganglionic nerves
What neurotransmitters are short chains of amino acids and are a diverse group including substance P and endorphins?
neuropeptides
What neurotransmitters are not stored in vesicles and are actually synthesized and released into synapse directly?
gases
The autonomic and somatic nervous systems have which branches?
afferent (sensory) and efferent (motor) branches
Which division of the nervous system has sensory components which convey sensations from the eyes, nose, and other sensory organs to the brain + motor components transmitting impulses to the skeletal muscles?
somatic nervous system
Which division of the nervous system conveys sensory impulses form the blood vessels, heart, organs in the chest, abdomen, and pelvis via nerves to the brain. The motor component transmits signals to end organs.?
autonomic nervous system
Which nervous system consists of the interneurons, brain, and spinal cord?
central nervous system
The brain and spinal cord have three layers of protective covering called what?
meninges
(Note: right underneath the bone)
What are the layers of the meninges?
dura mater
arachnoid mater
pia mater
(Note: from outer to innermost layer)
Which meninges layer is the outermost layer; thick, protects brain and spinal cord, has vein-like structures to carry blood from brain back to heart?
dura mater
Which meninges layer is middle layer with a spiderweb-like appearance?
arachnoid mater