The Nervous System Flashcards

1
Q

neurons

A

specialized cells capable of transmitting electrical impulses, and then translating those electrical impulses to chemical signals
shape matches its function, dictated by the other cells with which it interacts

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2
Q

cell body (soma)

A

where nucleus of neuron is located

location of the endoplasmic reticulum and ribosomes

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3
Q

dendrites

A

appendages of neuron emanating directly from the soma

receive incoming messages from other cells

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4
Q

axon hillock

A

integrates incoming signals
plays an important role in action potentials
sums signals in order to determine whether excitatory enough to initiate an action potential

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5
Q

action potentials

A

transmission of electrical impulses down the axon
signals can be either excitatory or inhibitory–if excitatory enough, will initiate these
relay electrical impulses down the axon to the synaptic bouton
all-or-nothing messages
cause the release of neurotransmitters into the synaptic cleft

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6
Q

axon

A

long appendage of neuron that terminates in close proximity to a target structure (a muscle, glad, or other neuron)

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7
Q

myelin

A

insulates most mammalian nerve fibers to prevent signal loss or crossing of signals
increases the speed of conduction in the axon
produced by oligodendrocytes (CNS) or Schwann cells (PNS)

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8
Q

myelin sheath

A

maintains the electric signal within one neuron

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9
Q

oligodendrocytes

A

produce myelin in CNS

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10
Q

Schwann cells

A

produce myelin in PNS

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11
Q

nodes of Ranvier

A

at certain intervals along the axon, there are small breaks in the myelin sheath with exposed areas of axon membrane
critical for rapid signal conduction

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12
Q

nerve terminal/ synaptic bouton (knob)

A

at the end of the axon

enlarged and flattened to maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters

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13
Q

neurotransmitters

A

chemicals that transmit information between neurons

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14
Q

synaptic cleft

A

small space between neurons into which the terminal portion of the axon releases neurotransmitters which bind to the dendrites of the postsynaptic neuron

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15
Q

synapse

A

collectively, the nerve terminal, synaptic cleft, and postsynaptic membrane

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16
Q

nerve

A

multiple neurons bundled together in the PNS

may be sensory, motor, or mixed

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17
Q

tracts

A

axons bundled together in CNS

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18
Q

nuclei

A

how cell bodies of neurons in the same tract are grouped (CNS)

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19
Q

glial cells/ neuroglia

A

play both structural and supportive roles

  • astrocytes
  • ependymal cells
  • microglia
  • oligodendrocytes (CNS) & Schwann cells (PNS)
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20
Q

astrocytes

A

nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue

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21
Q

ependymal cells

A

line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber

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22
Q

microglia

A

phagocytic cells that ingest and break down waste products and pathogens in the CNS

23
Q

resting membrane potential

A

-70 mV
inside of neuron negative relative to outside
use selective permeability to ions and Na+/K+ ATPase to maintain this negative internal environment
electrical potential difference (voltage) between inside of the neuron and extracellular space

24
Q

Na+/K+ ATPase

A

maintains resting membrane potential at -70 mV by moving 3 Na+ ions out of the cell for every 2 K+ ions moved into the cell
important for restoring gradient after action potentials have been fired (energy necessary to move ions against their gradients)
active transport

25
depolarization
caused by excitatory input (raises the membrane potential, Vm, from its resting potential makes neuron more likely to fire an action potential
26
hyperpolarization
caused by inhibitory input (lowers the membrane potential from its resting potential) makes neuron less likely to fire an action potential
27
threshold
usually in the range of -55 to -40 mV if enough excitatory input to be depolarized to this point, action potential will be triggered (opening of voltage-gated sodium channels in membrane) therefore, not every stimulus generates a response
28
summation
additive effects of multiple signals | temporal and spatial
29
temporal summation
multiple signals integrated during a relatively short period of time
30
spatial summation
additive effects are based on the number and location of incoming signals
31
electrochemical gradient
promotes the migration of sodium into the cell interior of cell more negative than exterior of cell, which favors the movement of positively charged sodium cations into the cell higher conc of sodium outside the cell than inside, which also favors movement of sodium into the cell
32
depolarization
occurs when membrane potential becomes more positive as sodium passes through ion channels into the cell
33
inactivated sodium channels
occurs when Vm approaches +35 mV | have to be brought back near the resting potential to be reversed
34
closed sodium channels
before the cell reaches threshold, and after inactivation has been reversed
35
open sodium channels
from threshold to approximately +35 mV
36
inactive sodium channels
from approximately +35 mV to the resting potential
37
repolarization
restoration of the negative membrane potential as positively charged potassium cations are driven out of the cell
38
hyperpolarization
efflux of K+ causes an overshoot of resting membrane potential serves an important function: makes the neuron refractory to further action potentials
39
refractory periods
absolute and relative
40
absolute refractory period
no amount of stimulation can cause another action potential to occur
41
relative refractory period
there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value
42
impulse propagation
for a signal to be conveyed to another neuron, the action potential must travel down the axon and initiate neurotransmitter release information can only flow in one direction
43
saltatory conduction
process by which an electrical signal jumps across the nodes of Ranvier to travel down the axon
44
neurotransmitters
released into synapse at nerve terminal when action potential arrives, voltage-gated calcium channels open influx of calcium causes fusion of vesicles filled with these with the presynaptic membrane, resulting in exocytosis of these into synaptic cleft bind to receptors on the postsynaptic cell, which may be ligand-gated ion channels or G protein-coupled receptors must be cleared from postsynaptic receptors to stop the propagation of the signal can be enzymatically broken down, can be absorbed back into presynaptic cell, can diffuse out of synaptic cleft
45
reuptake channels
absorb neurotransmitters back into the presynaptic cell
46
white matter
in CNS, consists of myelinated axons--in brain, deeper than grey matter; in spinal cord, grey matter deeper
47
grey matter
in CNS, consists of unmyelinated cell bodies and dendrites
48
somatic NS
voluntary
49
autonomic NS
automatic | divided into parasympathetic NS and sympathetic NS
50
parasympathetic NS
rest-and-digest
51
sympathetic NS
fight-or-flight
52
reflex arcs
use ability of interneurons in spinal cord to relay information to the source of stimuli while simultaneously routing it to the brain
53
monosynaptic reflex arc
sensory (afferent, presynaptic) neuron fires directly onto motor (efferent, postsynaptic) neuron
54
polysynaptic reflex arc
sensory neuron may fire onto motor neuron as well as interneurons that fire onto other motor neurons