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Physiology > Nervous System and Neuron Excitability parts 1 & 2 > Flashcards

Nervous System and Neuron Excitability parts 1 & 2 Flashcards

1
Q

The nervous system plays a major role/is responsible for what (5)?

A
  1. Maintaining homeostasis
  2. Sensations
  3. Behaviors
  4. Memories
  5. Initiation of all voluntary movements
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2
Q

When stimuli cause variables to deviate from their set points, neurons respond by forming _______. The ability to form these is called ______.

A

electrical signals (graded and action potentials)
electrical excitability

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3
Q

What are the two types of electrical signals neurons can form?

A

Graded potentials
Action potentials

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4
Q

Electrical excitability is measured in what?

A

Action potentials (because electrical excitability is the ability to produce action potentials in response to stimuli)

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5
Q

Explain the difference between graded potentials and action potentials.

A

Graded potentials - “tiny potentials” that build up to an action potential; goes shorter distances
Action potentials - longer distances; electrical excitability is measured in action potentials

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6
Q

Action potentials communicate with other ____, ____, and ____ to regulate organ activity and restore homeostasis.

A

neurons, muscles, and glands

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7
Q

Regional specialization results in _______

A

predictable symptoms

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8
Q

Collectively, the ______ of the body constitute the nervous system.

A

Nervous tissue

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9
Q

The nervous system has a mass of ____ which constitutes about ___ of total body weight.

A

2 kg (~4.5 lbs); 3%

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10
Q

T/F The nervous system is the smallest and most complex of the 12 body systems

A

T

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11
Q

What are the two main subdivisions of the nervous system and their components?

A
  1. CNS - brain and spinal cord ONLY
  2. PNS - ALL nervous tissue OUTSIDE of the CNS: nerves and sensory receptors (I.e. cranial n. is part of the PNS - it is a NERVE that branches FROM the CNS, but is not part of it)
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12
Q

part of the CNS located in the skull

A

brain

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13
Q

part of the CNS that is connected to the brain and is enclosed by the bones of the vertebral column

A

spinal cord

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14
Q

What are the 4 functions of the CNS?

A
  1. Processes incoming sensory information (input)
  2. Thoughts
  3. Emotions
  4. Memories
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15
Q

Where do most signals that stimulate the muscles and glands originate?

A

CNS

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16
Q

What are nerves?

A

Bundles of axons that lie OUTSIDE the brain and spinal cord

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17
Q

_____ pairs of cranial nerves emerge from the _____

A

12; brain

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18
Q

____ pairs of spinal nerves emerge from the ______

A

31; spinal cord

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19
Q

Structure that monitors changes in the internal and external environment

A

sensory receptor (I.e. touch receptors in skin, olfactory/smell receptors in nose, stretch receptors in stomach wall/organs)

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20
Q

What are the subdivisions of the PNS and their functions?

A
  1. Afferent (Arrives to CNS) - conveys input INTO the CNS from the sensory receptors in the body (I.e., somatic senses and special senses)
  2. Efferent (Exits CNS) - conveys output FROM CNS to Effectors (muscles and glands)
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21
Q

What are the subdivisions of the Efferent NS and their functions?

A
  1. Somatic NS - coveys output from the CNS to the skeletal muscles ONLY (voluntary control)
  2. Autonomic NS - conveys output from the CNS to the smooth muscle, cardiac muscle, and glands (involuntary control)
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22
Q

Which branch of the nervous system is specific for voluntary control?

A

Somatic NS (branch of the Efferent NS which is a branch of the PNS)

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23
Q

Which branch of the nervous system is specific for involuntary control?

A

Autonomic NS (branch of the Efferent NS which is a branch of the PNS)

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24
Q

Conveys output from CNS to cardiac muscle, smooth muscle, and glands

A

Autonomic NS

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25
Q

Conveys output from CNS to the skeletal muscle

A

Somatic NS

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26
Q

Conveys input into the CNS from sensory receptors such as somatic and special senses

A

Afferent NS

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27
Q

What are the 3 subdivisions of the Autonomic NS and their functions?

A
  1. Sympathetic NS - supports exercise or emergency “fight or flight”
  2. Parasympathetic NS - supports “rest and digest” functions
  3. Enteric NS - nerves in the wall of the GI tract
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28
Q

Which branch of the Autonomic NS innervates its effectors?

A

Both sympathetic and parasympathetic

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29
Q

How do the sympathetic and parasympathetic NSs function together?

A

Opposing actions - 1 “revs up” while the other “revs down”

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30
Q

What are the 3 basic functions of the nervous system?

A
  1. Sensory - sensory receptors detect external/internal stimuli
  2. Integrative - CNS processes sensory information by analyzing it and making decisions for appropriate responses (integration)
  3. Motor - after integration (decision of appropriate response is made), an appropriate motor response is elicited (motor info conveyed from CNS through cranial and spinal nerves of PNS to effectors (muscles and glands) where a response (muscle contraction or gland secretion) occurs
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31
Q

What are the two principal types of cells of the nervous system?

A
  1. Neurons - nerve cells
  2. Neuroglia
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32
Q

The basic functional unit of the nervous system:

A

neuron/nerve cell

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33
Q

5 examples of neuron functions:

A
  1. Sensing
  2. Thinking
  3. Remembering
  4. Controlling muscle activity
  5. Regulating glandular secretions
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34
Q

Main INPUT portion of the neuron

A

dendrites

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35
Q

control center of the neuron

A

cell body/soma (“brain” of the neuron)

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36
Q

Cluster of cell bodies in the CNS = ?

A

Nucleus

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37
Q

Cluster of cell bodies in the PNS = ?

A

Ganglion

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38
Q

OUTPUT portion of neuron

A

axon

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39
Q

Bundle of axons in the PNS

A

Nerve (nerves are NEVER part of CNS)

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40
Q

Bundle of axons in CNS

A

Tract

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41
Q

Single, long process that extends from the cell body of a neuron and functions to generate and propagate actions potentials

A

axons

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42
Q

Short, highly branched processes that extend from the cell body and receive signals from other neurons/environment

A

dendrites

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43
Q

Dendrites receive signals/input from ____ and ____

A

other neurons; environment

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44
Q

In a neuron, structure that contains organelles and directs protein synthesis (of enzymes, membrane proteins, organelles, etc.) as well as other cellular activities; also receives signals from other neurons

A

cell body of neuron

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45
Q

Function of the axon:

A

generates and conducts action potentials

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46
Q

cone-shaped process where axon leaves the cell body

A

axon hillock

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47
Q

Axon hillock is also called the ______, why?

A

“trigger zone’; because it activates/”triggers” action potentials (area where lots of Na+ channels rush into cell causing depolarization)

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48
Q

side branches that extend off the axon

A

axon collateral

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49
Q

function of the axon collateral?

A

“talks” to other neurons

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50
Q

The end of an axon along with its collaterals

A

axon terminal

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51
Q

Axon terminals swell into synaptic end bulbs and contain _____ that house ______

A

synaptic vesicles; neurotransmitters

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52
Q

the chemical messengers of the nervous system

A

neurotransmitters

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53
Q

site of communication between a neuron and target cell (other neuron, muscle fiber, gland cell)

A

synapse

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54
Q

T/F Axonal transport uses ATP

A

T

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55
Q

Term referring to the movement of substances along the microtubule within an axon toward the axon terminal

A

Anterograde

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56
Q

Term referring the the movement of substances along the microtubule within an axon back toward the cell body

A

retrograde

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57
Q

What molecule is involved in moving substances anterograde along the microtubule of an axon?

A

Kinesin

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58
Q

What molecule is involved in transporting substances along the microtubule in an axon retrograde?

A

Dyneins

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59
Q

What substances may be moved anterograde by kinesins?

A

organelles and synaptic vessicles

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60
Q

What substances may be moved retrograde by dyneins?

A
  1. membrane vesicles
  2. cellular materials to be recycled
  3. Trophic chemicals (NGF)
  4. Harmful agents (toxins)
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61
Q

How would a toxin be carried into the CNS in a neuron?

A

retrograde transport

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62
Q

What does release of a tetanus toxin in a wound cause?

A

toxin is carried to CNS by retrograde transport => activation of neurons that stimulate the muscle to contract leading to prolonged muscle spasms (tetanus)

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63
Q

What is the cause of delay between release of toxin in nervous system and symptoms?

A

takes time for toxin to travel

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64
Q

Wounds in what area of the body are most susceptible to more rapid infection?

A

head/neck

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65
Q

Where are interneurons located?

A

located ENTIRELY in the CNS between the sensory and motor neurons

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66
Q

literally means “nerve glue”

A

neuroglia

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67
Q

Neuroglia make up about ____ the volume of the CNS

A

1/2

68
Q

Which is NOT a function of neuroglia?:
- provides structural support
- transmits action potentials
- nourishment
- protection
- facilitates neurotransmission
- maintains homeostasis of interstitial fluid

A

transmits action potentials

69
Q

What can neuroglia cells do that neurons cannot which contribute to formation of tumors by neuroglia cells and difficulty/inability for neurons to heal?

A

multiply and divide

70
Q

brain tumors = _____

A

Gliomas

71
Q

neuroglia of PNS

A

Schwann cells

72
Q

Neuroglia found in CNS:

A
  1. Oligodendrocytes
  2. Astrocytes
  3. Microglia
  4. Ependymal cells
73
Q

most numerous glial cell

A

astrocytes

74
Q

neuroglial cell which maintains blood brain barrier

A

astrocytes

75
Q

Responsible for forming and maintaining myelin sheath around axons in CNS

A

Oligodendrocytes

76
Q

How do oligodendrocytes contribute to the difficulty to heal damaged neurons?

A

secrete inhibitory protein after nerve injury

77
Q

remove cellular debris and phagocytize microbes and damaged nervous tissue

A

microglia - phagocyte of the nervous system

78
Q

produces and assists in the circulation of CSF; line ventricles of the brain and central canal of the spinal cord

A

Ependymal cells

79
Q

What contributes in the difficulty for a neuron (CNS) to heal?

A

Astrocytes rapidly react to damaged neural tissue by proliferation (creates scar - a physical barrier to regeneration)
Oligodendrocytes secrete inhibitory protein after nerve injury
Absence of growth stimulating cues from fetal development

80
Q

Function of Schwann cells:

A

form myelin sheaths around axons of PERIPHERAL neurons
Participate in axon regeneration (PNS)

81
Q

Myelin sheaths are multilayer coverings composed of _____ and _____

A

lipids; proteins

82
Q

Function of myelin sheaths are to:

A
  1. insulates axon
  2. increases speed of the conduction of APs
83
Q

What 2 types of neuroglia produce myelin sheaths?

A
  1. Oligodendrocytes in CNS
  2. Schwann cells of PNS
84
Q

Gaps in myelin sheath =

A

Nodes of Ranvier

85
Q

Each Schwann cell wraps ___ axon segment between 2 nodes

A

1

86
Q

term for “sheath of Schwann” that contains the cytoplasm and nuclei of Schwann cells which lie OUTSIDE the myelin sheath

A

Neurilemma

87
Q

Schwann cells wrap about ____ of a single axon’s length by spiraling many times around the axon (as many as ___ layers)

A

1 mm; 100

88
Q

How can neurilemma be used to regenerate axons?

A

neurilemma form a regeneration tube through which the re-growing axon re-establishes its original connection

89
Q

each oligodendrocyte puts forth about ___ broad flat processes that spiral around CNS axons to form myelin sheath

A

15

90
Q

T/F Nodes of Ranvier are absent when oligodendrocytes form myelin sheath on the axon of a neuron in the CNS

A

F - they are present, but are fewer in number

91
Q

term for myelinated axons

A

white matter

92
Q

term for unmyelinated axons

A

gray matter

93
Q

Where can white matter be found?

A

brain and spinal cord; myelinated axons

94
Q

Where can gray matter be found?

A

brain and spinal cord
neuronal cell bodies
dendrites
unmyelinated axons
axon terminals
neuroglia

95
Q

What does multiple sclerosis do/cause and where?

A

Auto immune disease that causes progressive destruction of myelin sheaths of CNS
Multiple regions in the myelin sheaths deteriorate to scleroses
Myelin sheath destruction = slowing the short-circuiting of APs

96
Q

What is the difference between plasticity and repair?

A

Plasticity - ability to change throughout life (sprouting dendrites, new protein synthesis, changes in synaptic contacts)
Repair - regeneration after damage is LIMITED (need intact cell body and Schwann cell for regeneration)

97
Q

Graded potentials and action potentials are deviations of _____

A

Membrane potential (Voltage)

98
Q

Nerve AP results in a ____

A

nerve impulse

99
Q

Production of action potentials depend on 2 basic features of the plasma membrane of excitable cells:

A
  1. presence of specific types of ion channels
  2. resting membrane potential
100
Q

ion channel with gates that randomly alternate between open and closed positions

A

leak channels

101
Q

What are leak channel important for?

A

establishing the resting membrane potential

102
Q

opens or closes in response to a specific ligand (chemical) stimulus

A

ligand-gated channel

103
Q

Ligand channels participate in generation of ________

A

graded potentials

104
Q

opens or closes in response to mechanical stimulation (touch, pressure, tissue stretching, and vibration)

A

mechanically-gated channels

105
Q

Mechanically gated channels participate in generation of ________

A

graded potentials

106
Q

opens in response a change in membrane potential (voltage)

A

Voltage gated channels

107
Q

Voltage-gated channels are responsible for the generation and conduction of ______

A

action potentials

108
Q

Functions of ion channels:

A

Causes changes in membrane permeability
- ions can flow
- resting membrane potential changes
- allows for electrical communication

109
Q

Ion channels are common in excitable tissues such as:

A

muscle and nervous tissue

110
Q

What is membrane potential? What are its units?

A

Voltage/electrical potential difference that exists across the plasma membrane (charges along PM); volts (V) or mV

111
Q

Voltage is also known as ______

A

electrical potential difference

112
Q

The presence of the plasma membrane creates a(n) _______ distribution of positive and negative charges.

A

unequal

113
Q

____ cells display a resting membrane potential.

A

Unstimulated

114
Q

What is Resting Membrane Potential?

A

the voltage/electrical potential difference that exists across the plasms membrane of excitable cells (nervous and muscle) under resting conditions

115
Q

Generally, membrane potential will exhibit more ____ charges on the outside (side of ECF) and _____ charges on the inside (side of the cytosol) of the membrane.

A

positive; negative

116
Q

Describe Ohm’s law and its relationship to membrane potential.

A

I = V/R
I = current/flow of charged particles
V = voltage/electrical potential difference
R = Resistance/hindrance to flow of charges
Increasing voltage = decrease in resistance
Increasing resistance = decrease in voltage
- V and R are inversely proportional

117
Q

Voltage at RMP = ___

A

-70 mV

118
Q

In the plasma membrane, there are more _____ leak channels than ____ leak channels

A

K+; Na+; leak channels important for establishing the RMP

119
Q

In general, which ion is the plasma membrane most permeable to at resting membrane potential? Why?

A

K+ - has more leak channels for K+ than Na+

120
Q

What effect does an ion have when the plasma membrane is more permeable to that particular ion?

A

that ion has a greater influence on the resting membrane potential

121
Q

Which ion has the greatest influence on resting membrane potential? Why?

A

K+; plasma membrane is more permeable to K+ due to having more K+ leak channels

122
Q

What are the 3 determinants of the RMP?

A
  1. Unequal distribution of ions in the ECF and cytosol - want more Na+ outside (ECF) and more K+ inside
  2. Differences in membrane permeability (more permeable to K+ at RMP due to more K+ leak channels)
  3. Action of the Na+/K+ pump also contributes to the generation of the RMP (maintains unequal ion distribution)
123
Q

An inside-_______ membrane potential is reached upon a greater K+ concentration gradient (not considering electrical gradient for K+ or Na+ electrochemical gradient)

A

Negative

124
Q

An Inside-______ membrane potential is reached with a greater K+ concentration gradient along with a weaker K+ electrical gradient going in the opposite direction (K+ only cell)

A

negative (more negative)

125
Q

When concentration and electrical gradient for K+ are equal in strength and are going in opposite directions, _____ potential is reached (K+ only cell)

A

Potassium Equilibrium potential (Ek)

126
Q

At what voltage is potassium equilibrium potential?

A

-90 mV

127
Q

What occurs at the K+ leak channel when a potassium equilibrium potential is reached (K+ only cell)?

A

K+ ion will go down its concentration gradient and another K+ ion will go down its electrical gradient simultaneously

128
Q

An inside-_______ membrane potential is reached upon a greater Na+ concentration gradient (not considering electrical gradient for Na+ or K+ electrochemical gradient)

A

positive

129
Q

An Inside-______ membrane potential is reached with a greater Na+ concentration gradient along with a weaker Na+ electrical gradient going in the opposite direction (Na+ only cell)

A

positive (more positive)

130
Q

When concentration and electrical gradient for Na+ are equal in strength and are going in opposite directions, _____ potential is reached (Na+ only cell)

A

Sodium equilibrium potential (ENa)

131
Q

At what voltage is Na+ equilibrium potential?

A

+60 mV

132
Q

What occurs at the Na+ leak channel when a Na+ equilibrium potential is reached (Na+ only cell)?

A

Na+ ion will go down its concentration gradient and another Na+ ion will go down its electrical gradient simultaneously

133
Q

____ - the point at which there is no net flow of an ion

A

Equilibrium potential

134
Q

At equilibrium potential, the electrical and chemical gradient are ___ and ___.

A

equal and opposite

135
Q

What equation is used to calculate equilibrium potential?
What is the equilibrium potential for K+? for Na+?

A

Nernst equation (Ex = 61/z(always is 1) log([X] out from cytosol/[X] in from ECF)
-90 mV for K+; +60 mV for Na+

136
Q

What equation is used to calculate membrane potential and takes into account ion permeabilities?

A

Goldman-Hodgkin-Katz equation
Vm = 61log((Pk[K+ out] + PNa [Na+ out]) / (PNa[K+ in] + PNa[Na+ in])

137
Q

What result should be obtained after using Goldman-Hodgkin-Katz equation?

A

-70 mV

138
Q

T/F Graded potentials always are excitatory.

A

F - will not always build up to a response/action potential

139
Q

Graded potentials are generated from ____ and ___ gated channels

A

ligand-gated; mechanically-gated

140
Q

Graded potentials experience a ___ deviation from RMP

A

small (less than 10 mV difference)

141
Q

Depolarizing graded potentials makes the membrane potential ______ polarized and therefore have a ___ charge

A

less; less negative

142
Q

Hyperpolarizing graded potentials makes the membrane potential ____ polarized and therefore have a _____ charge

A

more; more negative

143
Q

______ occur when stimulus causes mechanically or ligand-gated channels to open or close

A

Graded potentials

144
Q

Where are mechanically-gated channels located?

A

Dendrites of sensory neurons (stimulus deforms membrane - I.e., pressing fingers against a table)

145
Q

Where are ligand-gated channels located?

A

Dendrites AND cell bodies of interneurons and motor neurons

146
Q

Graded potentials experience ______, a bidirectional movement from stimulus site

A

Local current flow

147
Q

T/F Graded potentials and axons participate in local current flow - the bidirectional movement from stimulus site

A

F - only graded potentials participate in local current flow; axons go in one direction => towards their terminals

148
Q

What are primary differences between graded and action potentials?

A

Graded potentials:
- along dendrites (mechanically and ligand-gated channels)
- small deviation from RMP
- local current flow - bidirectional movement from stimulus
- decremental conduction- gradual “dying out” from loss of charges through leak channels
- can vary in amplitude
- amplitude of GPs decrease as distance from point of origin increases
- ONLY USEFUL FOR SHORT DISTANCE COMMUNICATION
- GPs can be added together (SUMMATE) to generate an action potential
Action Potentials:
- along axon
- Voltage-gated channels
- move in one direction towards axon terminals
- threshold at -55 mV
- all-or-nothing principle (AP generated if stimulus causes potential to reach threshold)
- does NOT vary in amplitude (no such thing as a “strong AP), but a suprathreshold stimulus can cause for multiple APs to be generated
- LONG DISTANCE

149
Q

When do graded potentials occur?

A

when stimulus causes mechanically or ligand-gated channels to open or close

150
Q

Amplitude of GP ____ as distance from point of origin _______; what does this mean?

A

decreases; increases; GPs are only useful for SHORT distances

151
Q

What is decremental conduction?

A

The gradual “dying out” of graded potentials from loss of charges through leak channels

152
Q

____ - when two or more graded potentials add together, increasing the amplitude of the potential and therefore has the potential to reach threshold if combined graded potentials are strong enough

A

Summation of graded potentials

153
Q

____ and ____ graded potentials can summate

A

1 Depolarizing GP and 1 hyperpolarizing GP

154
Q

threshold = ____ mV

A

-55 mV

155
Q

How is an action potential generated?

A

stimulus must be strong enough to depolarize the membrane to threshold (-55 mV)

156
Q

Will a subthreshold stimulus cause an AP?

A

no (stimulus must cause depolarization to -55 mV)

157
Q

Will a suprathreshold stimulus cause an AP?

A

yes because it caused depolarization to threshold (-55 mV)

158
Q

T/F A suprathreshold stimulus will produce a stronger AP than a stimulus that just reached threshold

A

F - no such thing as a “strong AP”; an AP is just an AP and nothing else (all-or-nothing); a suprathreshold stimulus CAN produce more than 1 AP all of the same strength (because there are no APs that vary in strength)

159
Q

What are the 3 phases to an AP?

A
  1. Depolarizing phase - less polar, less negative
  2. Repolarizing phase - more polar, more negative
  3. After hyperpolarizing phase - returning back to RMP at -70 mV
160
Q

What occurs during the depolarizing phase of an AP?

A
  • Rising phase of an AP - less negative
  • rises until the MP reaches +30 mV
  • Caused by opening of voltage-gated Na+ channels
161
Q

What is it called when the depolarizing phase reaches between 0-30 mV?

A

overshoot

162
Q

How many Na+ ions flow across membrane during depolarization of an axon?

A

~10,000 Na+ ions

163
Q

What occurs during the repolarization phase?

A
  • Falling phase of an AP - more negative
  • becomes more negative until it reaches -70 mV (may continue to become more negative during hyperpolarization (-90 mV))
  • Caused by opening of the voltage-gated K+ channels
  • voltage-gated Na+ channels are inactivating
164
Q

What occurs during after-hyperpolarization phase?

A
  • After RMP is reestablished, undershoot (-90 mV) is observed
  • Voltage-gated K+ channels remain open, voltage-gated Na+ channels are in resting state
165
Q

Depolarization and most of the repolarization phase are part of the _______ period

A

absolute refractory period

166
Q

Then end portion of repolarization and after-hyperpolarizing phase are part of the _____ period

A

relative refractory period

Physiology (8 decks)

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