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anatomy and physiology exam 4 > chapter 12- nervous tissue > Flashcards

chapter 12- nervous tissue Flashcards

1
Q

the spinal cord & brain make up the what nervous system?

A

central

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2
Q

a bundle of axons with connective tissue & blood vessels that is connected to the spinal cord is a what?

A

spinal nerve

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3
Q

what division of the PNS carries info. coming into the CNS from the internal organs?

A

visceral afferent

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4
Q

what nervous system carries info. from the CNS to the skeletal muscles?

A

somatic

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5
Q

a large visible nucleolus tells you what about a cell?

A

making lots of ribosomes which it will use to make lots of protein

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6
Q

the visible collection of RER & ribosomes in the soma of a neuron are called what?

A

nissl bodies

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7
Q

what are the neuron cell processes that carry graded potentials?

A

dendrites

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8
Q

the membrane of the axon is called the what?

A

axolemma

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9
Q

what are the cells of the CNS that are responsible for the myelin?

A

oligodendrocytes

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10
Q

anterograde transport in an axon functions to do what?

A

move neurotransmitters from the soma to the terminal

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11
Q

how many axons does an anaxonic neuron have?

A

one, all neurons have one axon

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12
Q

most sensory neurons are structurally what neurons with their somas in peripheral sensory what cells?

A

unipolar & ganglia

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13
Q

the ependymal cells are responsible for the secretion & circulation of what?

A

cerebrospinal fluid (CSF)

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14
Q

if resistance is high, current is what?

A

low

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15
Q

ion channels that are always open & allow free flow of ions are called what channels?

A

passive/leak

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16
Q

a ligand-gated channel will open in response to a what?

A

chemical bonding

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17
Q

why does potassium generate less current than sodium when the ion channels are open on the membrane?

A

movements of sodium ions into the cell is favored by both the diffusion & electrical gradients whereas movement of potassium ions out of the cell its favored only by the diffusion gradient

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18
Q

opening of a sodium channel causes a what graded potential?

A

depolarizing

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19
Q

during an action potential, what happens at +30mV?

A

sodium channels close &potassium channels open

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20
Q

during which period do sodium channels open & the membrane can’t respond to additional stimuli?

A

absolute refractory

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21
Q

continuous propagation of action potentials occurs on what axons?

A

unmyelinated

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22
Q

what kind of info. is carried on type A axons?

A

somatic motor & sensory

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23
Q

inhibitory neurotransmitters cause a what of the post synaptic cell?

A

hyperpolarization

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24
Q

what is the neurotransmitter used at cholinergic synapses?

A

acetylcholine

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25
Q

if a neurotransmitter works by the direct effect, it will cause what to happen on the post synaptic cell?

A

open or close ion channels

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26
Q

in the indirect effect on the membrane potential, what is created inside the cell to open ion channels?

A

second messenger

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27
Q

what summation occurs when one synapse produces multiple ESPS in a row on one spit to reach the threshold?

A

temporal

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28
Q

a what neurons have been brought closer to the threshold by a depolarizing stimulus?

A

facilitated

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29
Q

the neurotransmitter responsible for our reward feelings is what?

A

dopamine

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30
Q

neurons get ATP through what?

A

aerobic respiration of glucose

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31
Q

neural tissue

A

-3% of body mass
-cellular, ~20% extracellular space
-two categories: neurons & neuroglia/glial cells

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32
Q

neurons

A

conduct nerve impulses

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33
Q

neuroglia/glial cells

A

“nerve glue”, supporting cells

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34
Q

central nervous system (CNS)

A

-spinal cord, brian
-function: integrate, process, coordinate, sensory input & motor output

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35
Q

peripheral nervous system (PNS)

A

-all neural tissue outside CNS
-function: carry info to/from CNS via nerves

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36
Q

nerve

A

bundle of axons (nerve fibers) with blood vessels & CT
-cranial nerves <-> brain
-spinal nerves <-> spinal cord

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37
Q

sensory/afferent division (division of PNS)

A

sensory receptors -> CNS

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38
Q

somatic afferent division

A

from skin, skeletal muscles, joints

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39
Q

visceral afferent division

A

from internal organs

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40
Q

motor/efferent division (division of PNS)

A

CNS -> effectors

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41
Q

somatic nervous system

A

-“voluntary nervous system”
-to skeletal muscles

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42
Q

autonomic nervous system (ANS)

A

-“involuntary nervous system”
-to smooth & cardiac muscle, glands
-both sympathetic & parasympathetic divisions tend to be antagonistic to each other

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43
Q

sympathetic division of the autonomic nervous system (ANS)

A

“fight or flight”

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44
Q

parasympathetic division of the autonomic nervous system (ANS)

A

“rest and digest”

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45
Q

neuron

A

-function: conduct nervous impulses (messages)
-characteristics: extreme longevity, amiotic (except hippocampus & olfactory receptors) & high metabolic rate: need O2 & glucose

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46
Q

nissl bodies

A

visible RER & ribosomes, gray

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47
Q

neurofilaments

A

neurofibrils, neurotubules (internal structures)

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48
Q

dendrites (cell extension of a neuron)

A

-receive info
-carry a graded potential toward soma
-contain same organelles as soma
-short, branched
-end in dendritic spines

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49
Q

neuron structure

A

-large soma/perikaryon
-large nucleus, large nucleolus (rRNA)
-many mitochondria, ribosomes, RER, Golgi (increases ATP & protein synthesis to produce neurotransmitters)
-no centrioles
-2 types of processes

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50
Q

axon (cell extension of a neuron)

A

-single, long
-carry an action potential away from soma
-release neurotransmitters at end to signal next cell
-long ones = “nerve fibers”

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51
Q

axon contains:

A

-neurofibrils & neurotubules (abundant)
-vesicles of neurotransmitter
-lysosomes, mitochondria, enzymes
-no nissl bodies, no golgi (no protein synthesis in axon)
-connects soma at axon hilock
-covered in axolemma
-end in synaptic terminals or knobs

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52
Q

axon collaterals

A

branches of axon

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53
Q

axon myelin sheath:

A

-protein + lipid
-protection
-insulation
-increase speed of impulse
-CNS: myelin from oligodendrocytes
-PNS: myelin from Schwann cells/neurilemma cells

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54
Q

axoplasmic transport

A

-move material between soma & terminal
-along neurotubules on kinesins
-2 transport systems: anterograde & retrograde
-some viruses use retrograde transport to gain access to CNS (Polio, Herpes, Rabies)

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55
Q

anterograde transport (axoplasmic transport)

A

soma -> terminal (neurotransmitters from soma)

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56
Q

retrograde transport (axoplasmic transport)

A

terminal -> soma (recycle breakdown products from used neurotransmitters)

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57
Q

synapse

A

site where neuron communicates with another cell: neuron or effector

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58
Q

presynaptic cell

A

sends message along axon to axon terminal

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59
Q

postsynaptic cell

A

receives message as neurotransmitter

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60
Q

neurotransmitter

A

chemical, transmits signal from pre- to post- synaptic cell across synaptic cleft

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61
Q

synaptic knob

A

small, round, when postsynaptic cell is neuron, synapse on dendrite or soma

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62
Q

synaptic terminal

A

complex structure, at neuromuscular or neuroglandular junction

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63
Q

anaxonic neurons (structural classification of neurons)

A

-dendrites & axons look the same
-brain & special sense organs

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64
Q

bipolar neurons (structural classification of neurons)

A

-1 dendrite, 1 axon
-soma in the middle
-rare: special sense organs, relay from receptor to neuron

65
Q

unipolar neurons (structural classification of neurons)

A

-1 long axon, dendrites at one end, soma off-side (T shape)
-most sensory neurons

66
Q

multipolar neurons (structural classification of neurons)

A

-2 or more dendrites
-1 long axon
-99% all neurons
-most CNS

67
Q

sensory/afferent neurons (functional classification of neurons)

A

-transmit info from sensory receptor to CNS
-most unipolar
-soma in peripheral sensory ganglia

68
Q

ganglia

A

collection of cell bodies in PNS

69
Q

somatic sensory neurons

A

receptor monitor outside conditions

70
Q

visceral sensory neurons

A

receptors monitor internal conditions

71
Q

motor/efferent neurons (functional classification of neurons)

A

-transmit commands from CNS to effector
-most multipolar

72
Q

somatic motor neurons

A

-innervate skeletal muscle
-conscious control or reflexes

73
Q

visceral/autonomic motor neurons

A

-innervate effectors on smooth muscle, cardiac muscle, glands, adipose

74
Q

interneurons/association neurons (functional classification of neurons)

A

-distribute sensory info & coordinate motor activity
-between sensory & motor neurons
-in brain, spinal cord, autonomic ganglia
-most multipolar

75
Q

neuroglia in CNS

A

-outnumber neurons 10:1
-half mass of brain

76
Q

ependymal cells (neuroglia in CNS)

A

-line central canal of spinal cord & ventricles of brain
-secrete cerebrospinalal fluid (CSF)
-have cilia to circulate CSF

77
Q

cererospinal fluid (CSF)

A

cushion brain, nutrient & gas exchange

78
Q

astrocytes (neuroglia in CNS)

A

-most abundant CNS neuroglia
-varying functions

79
Q

functions of astrocytes:

A

a. blood-brain barrier
b. framework of CNS
c. repair damaged neural tissue
d. guide neuron development in embryo
e. control interstitial environment: regulate conc. ions, gasses, nutrients, neurotransmitters

80
Q

oligodendrocytes (neuroglia in CNS)

A

-create myelin sheath
-1 cell contributes myelin to many neighboring axons
-lipid in membrane insulates axon for faster action potential conductance
-nodes (of ranvier)
-“white matter”

81
Q

myelin sheath

A

wide flat processes wrap local axons

82
Q

Nodes (of Ranvier)

A

gaps on axon between processes/myelin, necessary to conduct impulse

83
Q

“white matte” of oligodendrocytes

A

white, myelinated axons

84
Q

microglia (neuroglia in CNS)

A

-phagocytic
-wander CNS
-engulf debris, pathogens
-important CNS defense (no immune cells or antibodies)

85
Q

satellite cells (neuroglia in PNS)

A

-surround somas in ganglia
-isolate PNS cells
-regulate interstitial environment

86
Q

Schwann cells/neurilemma cells

A

-myelinated axons in PNS
-whole cells wrap axon, many layers, organelles compressed in superficial layer (neurilemma)
-Nodes (of Ranvier) between cells
-vital to repair of peripheral nerve fibers after injury: guide growth to original synapse

87
Q

neurophysiology

A

-requires transmembrane potential = electrical difference across cell membrane
-cells: positive charge outside (pump cations out) & neg. charge inside (proteins)

88
Q

voltage

A

measure of potential energy generated by separation of opposite charges

89
Q

current

A

flow of electrical charges (ions), cell can produce current (nervous impulse) when ions move to eliminate the potential differences (volts) across the membrane

90
Q

resistance

A

restricts ion movement (current) (high resistance = low current); membrane has resistance, restricts ion flow/current

91
Q

Ohm’s law

A

-current = voltage ÷ resistance
-current highest when voltage high & resistance low
-cell voltage set at -70mV but membrane resistance can be altered to create current
-membrane resistance depends on permeability to ions: open or close ion channels

92
Q

cells must always have what?

A

resistance or else ions would equalize, voltage = zero, no current generated = no nervous impulse

93
Q

membrane ion channels

A

-allow ion movement (alter resistance)
-each channel specific to one ion type

94
Q

passive channels (leak channels) (membrane ion channels)

A

-always open, free flow
-sets resting membrane potential at -70mV

95
Q

active channels (membrane ion channels)

A

-open/close in response to signal
-3 types: chemically regulated, voltage regulated, mechanically regulated

96
Q

chemically regulated/Ligand-gated (active channel)

A

-open in response to chemical binding
-located on any cell membrane (dendrites, soma)

97
Q

voltage regulated channels (active channel)

A

-open/close in response to shift in transmembrane potential
-excitable membrane only: conduct action potentials (axolemma, sarcolemma)

98
Q

mechanically regulated channels (active channel)

A

-open in response to membrane distortion
-on dendrites of sensory neurons for touch, pressure, vibration

99
Q

when channels opens, ions flow along electrochemical gradient:

A

-diffusion (high conc. to low)
-electrical attraction
/repulsions

100
Q

sodium-potassium pump

A

-uses ATP to move 3 Na+ out 2 K+ in (70% of neuron ATP for this)
-runs anytime cell not conducting impulse
-creates high (K+) inside & high (Na+) outside

101
Q

when Na+ channels open in sodium-potassium pump:

A

-Na+ flows into cell:
1. favored by diffusion gradient
2. favored by electrical gradient
-open channel = decrease in resistance = increase in ion flow/current

102
Q

when K+ channels open in sodium-potassium pump:

A

-K+ flows out of cell:
1. favored by diffusion gradient only
2. electrical gradient repels K+ exit
-thus less current than Na+

103
Q

channels open = resistance low = ions move until equilibrium potential, what does this depend on?

A

diffusion gradient & electrical gradient

104
Q

what are the equilibrium potentials for K+ & Na+?

A

-K+ = -90mV (K+ can’t leave cell)
-Na+ = +66mV (too positive in cell, so Na+ can no longer enter)

105
Q

open channel -> current = what?

A

graded potential

106
Q

graded potential

A

localized shift in transmembrane potential due to movement of charges into/out of cell (not nervous impulse messages)

107
Q

Na + channel opens (graded potential):

A

Na+ flows in, depolarization (cell less negative)

108
Q

K + channel opens (graded potential):

A

K+ flows out, hyperpolarization (cell more negative)

109
Q

graded potentials:

A

-occur on any membrane: dendrites and somas
-can be depolarizing or hyperpolarizing
-amount of depolarization or hyperpolarization depends on intensity of stimulus: increase channels open = increase voltage change
-passive spread from site of stimulation over short distance
-effect on membrane potential decreases with distance from stimulation site
-repolarization occurs as soon as stimulus is removed: leak channels & Na+/K+ pump reset resting potential

110
Q

action potentials:

A

-occur on excitable membranes only (axolemma, sarcolemma)
-always depolarizing
-must depolarize to threshold (-55mV) before action potential begins (voltage-gated channels on excitable
membrane open at threshold to propagate action potential)
-action potential at one site depolarizes adjacent sites to threshold
-propagated across entire membrane surface without decrease in strength

111
Q

action potentials “all or none”

A

all stimuli that exceed threshold will produce identical action potentials

112
Q

generation of an action potential: depolarization to threshold step 1

A

-a graded potential depolarizes local membrane & flows toward axon
- if threshold is met (-55mV) at the hillock, an action potential will be triggered

113
Q

generation of an action potential: activation of sodium channels & rapid depolarization step 2

A
  • at threshold (-55mV), voltage-regulated sodium channels on excitable axolemma membrane open
    -Na+ flows into cell depolarizing it
  • transmembrane potential rapidly changes from -55mV to +30mV
114
Q

generation of an action potential: inactivation of sodium channels & activation of potassium channels step 3

A
  • at +30mV Na+ channels close & K+ channels open
    -K+ flows out of the cell repolarizing it
115
Q

generation of an action potential: return to normal permeability step 4

A
  • at -70mV K+ channels begin to close
    -cell hyper polarizes to -90mV until all channels finish closing
    -leak channels restore the resting membrane potential to -70mV
116
Q

restimulation only when Na+ channels closed:

A

-influx of Na + necessary for action potential
-cell has ions for thousands of action potentials, eventually must run Sodium-Potassium pump (burn ATP) to reset high [K+] inside and high [Na+] outside

117
Q

absolute refractory period

A

-55mV (threshold) to +30mV, Na + channels open, membrane cannot respond to additional stimulus

118
Q

relative refractory period

A

+30mV to -70mV (return to resting potential), Na+ channels closed, membrane capable of second action potential but requires larger/longer stimulus (threshold elevated)

119
Q

propagation of action potentials:

A

-once generated must be transmitted length of axon: hillock to terminal
-speed depends on: degree of myelination (yes or no) & axon diameter

120
Q

continuous propagation

A

-unmyelinated axons
-whole membrane depolarizes and repolarizes sequentially hillock to terminal
-only forward movement; membrane behind always in absolute refractory period

121
Q

saltatory propagation

A

-myelinated axons
-depolarization only on exposed membrane at nodes
-myelin insulates covered membrane from ion flow
-action potential jumps from node to node: faster and requires less energy to reset

122
Q

axon diameter (propagation of action potentials)

A

larger axon -> less resistance -> easier ion flow -> faster action potential

123
Q

type A fibers/axon

A
  • 4-20μm diameter
  • myelinated (saltatory propagation)
  • action potentials 140m/sec
  • carry somatic motor & somatic sensory info
124
Q

type B fibers/axon

A
  • 2-4μm diameter
  • myelinated (saltatory propagation)
  • action potentials 18m/sec
  • carry autonomic motor & visceral sensory info
125
Q

type C fibers/axon

A
  • < 2μm diameter
  • unmyelinated (continuous propagation)
  • action potentials 1m/sec!
  • carry autonomic motor & visceral sensory info
126
Q

myelination

A

-requires space, metabolically expensive
-only important fibers large and myelinated
-occurs in early childhood
-results in improved coordination

127
Q

multiple sclerosis

A

genetic disorder, myelin on neurons in PNS destroyed ->numbness, paralysis

128
Q

synapse

A

-junction between transmitting neuron (presynaptic cell) and receiving cell (postsynaptic cell), where nerve impulse moves from one cell to next
-two types: electrical & chemical

129
Q

electrical synapse

A

-direct contact via gap junctions
-ions flow directly from pre to post cell
-less common synapse
-in brain (conscious perception)

130
Q

chemical synapse

A

-most common
-pre and post-cells separated by synaptic cleft
-presynaptic neuron releases neurotransmitter to trigger effect on postsynaptic cell

131
Q

dynamic (of chemical synapses)

A

facilitate or inhibit transmission, depending on neurotransmitter

132
Q

excitatory neurotransmitter (dynamic of chemical synapses)

A

-depolarization
-propagate action potential

133
Q

inhibitory neurotransmitter (dynamic of chemical synapses)

A

-hyperpolarization
-suppress action potential

134
Q

events at a cholinergic synapse with acetylcholine as neurotransmitter: an action potential arrives step 1

A

-an arriving action potential depolarizes the synaptic knob

135
Q

events at a cholinergic synapse with acetylcholine as neurotransmitter: extracellular Ca2+ enters the synaptic terminal triggering the exocytosis of ACh step 2

A

-calcium ions enter the cytoplasm of the synaptic knob
-ACh is released through exocytosis of neurotransmitter vesicles

136
Q

events at a cholinergic synapse with acetylcholine as neurotransmitter: ACh binds to receptors & depolarizes postsynaptic membrane step 3

A

-ACh diffuses across synaptic cleft & binds to receptors in postsynaptic membrane
-chemically regulated sodium channels on postsynaptic surface are activated, producing graded depolarization
-ACh release ceases bc calcium ions are removed from cytoplasm of synaptic knob

137
Q

events at a cholinergic synapse with acetylcholine as neurotransmitter: ACh is removed by AChE (acetylcholinesterase) step 4

A

-depolarization ends as ACh is broken down into acetate & choline by AChE
-synaptic knob reabsorbs choline from synaptic cleft & uses it to resynthesize ACh

138
Q

direct effect on membrane potential (neurotransmitter mechanism of action)

A

-open or close channels upon binding to post synaptic cell
-provides a rapid response
- ex: ACh (cholinergic synapse)

139
Q

indirect effect on membrane potential (neurotransmitter mechanism of action)

A

-binds a receptor that activates a G protein in post-synaptic cell
-active G protein activates a 2nd messenger (cAMP, cGMP, diacyglyceride, Ca++)
-2nd messenger opens ion channels or activates enzymes
-provides slower but long-lasting effects
-ex: norepinephrine (adrenergic synapse)

140
Q

example of indirect action (neurotransmitter mechanism of action)

A
  1. neurotransmitter binds receptor
  2. receptor activates G protein
  3. G protein activates adenylate cyclase
  4. adenylate cyclase converts ATP to cyclic AMP
  5. cAMP opens ion channels
141
Q

post synaptic potential

A

-graded potential caused by a neurotransmitter due to opening or closing of ion channels on postsynaptic cell membrane
-two types: excitatory postsynaptic potential (EPSP) & inhibitory post synaptic potential (IPSP)

142
Q

inhibitory post synaptic potential (IPSP)

A

-causes hyperpolarization
-inhibits postsynaptic cell (need larger stimulus to reach threshold)

143
Q

excitatory postsynaptic potential (EPSP)

A

-causes depolarization
-multiple EPSPs needed to trigger action potential in post-cell axon

144
Q

temporal summation (EPSP summation)

A

-single synapse fires repeatedly: string of EPSPs in one spot
-each EPSP depolarizes more until threshold reaches hillock

145
Q

spatial summation (EPSP summation)

A

-multiple synapses fire simultaneously
-collective depolarization reaches threshold

146
Q

facilitated

A

depolarized; brought closer to threshold by some sort of stimulus, less stimulus now required to reach threshold (e.g. caffeine)

147
Q

post synaptic potentiation

A

repeat stimulation of same synapse conditions synapse, pre-cell more easily stimulates post-cell to threshold (repetition)

148
Q

neuromodulators

A

chemicals that influence synthesis, release, or degradation of neurotransmitters thus altering normal response of the synapse

149
Q

acetylcholine- cholinergic synapses (common neurotransmitter)

A

-excitatory
-direct effect
-skeletal neuromuscular junctions, many CNS synapses, all neuron to neuron PNS, all parasympathetic ANS

150
Q

norepinephrine- adrenergic synapses

A

-excitatory
-second messengers
-many brain synapses, all sympathetic ANS effector junctions

151
Q

dopamine

A

-excitatory or inhibitory
-second messengers
-many brain synapses, many functions
-responsible for reward feeling
-cocaine: inhibits removal = “high”
-Parkinson’s disease: damaged neurons = ticks, jitters

152
Q

serotonin

A

-inhibitory
-direct or second messenger
-brain stem for emotion
-anti-depression/ anti-anxiety drugs block uptake

153
Q

gamma aminobutyric acid (GABA)

A

-inhibitory
-direct effect
-brain: anxiety control, motor coordination
-alcohol: augments effects = loss of coordination

154
Q

pH (factors that disrupt neural function)

A

pH: normal = 7.4
-pH 7.8 -> spontaneous action potentials = convulsions
-pH 7.0 -> no action potentials = unresponsive

155
Q

ion concentrations (factors that disrupt neural function)

A

high extracellular [K+] depolarize membranes = death, cardiac arrest

156
Q

temperature (factors that disrupt neural function)

A

-normal: 37°C
-higher: neurons more excitable (fever = hallucinations)
-lower: neurons non-responsive (hypothermia = lethargy, confusion)

157
Q

nutrient (factors that disrupt neural function)

A

-neurons: no reserves, use a lot of ATP
-require constant and abundant glucose
-glucose only

158
Q

oxygen (factors that disrupt neural function)

A

-aerobic respiration only for ATP
-no ATP = neuron damage/death

anatomy and physiology exam 4 (5 decks)

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