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anatomy and physiology > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

What are the three main functions of the nervous system?

A

The nervous system collects information, processes and evaluates it, and initiates a response to the information

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2
Q

What is the difference between the central nervous system (CNS) and peripheral nervous system (PNS)?

A

The CNS consists of the brain and spinal cord, while the PNS includes nerves and ganglia

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3
Q

What is the difference between the sensory and motor nervous systems

A

The sensory nervous system (afferent) receives sensory information and sends it to the CNS, while the motor nervous system (efferent) transmits motor output from the CNS to effectors.

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4
Q

What are the two divisions of the sensory and motor systems?

A

The sensory system has somatic and visceral divisions, while the motor system has somatic and autonomic (with sympathetic and parasympathetic) divisions.

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5
Q

What is the difference between cranial and spinal nerves?

A

Cranial nerves extend from the brain, while spinal nerves extend from the spinal cord.

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6
Q

What is the functional classification of nerves?

A

Sensory nerves transmit signals to the CNS, motor nerves transmit signals from the CNS, and mixed nerves contain both sensory and motor neurons.

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7
Q

what is a ganglion?

A

A ganglion is a cluster of neuron cell bodies in the peripheral nervous system (PNS).

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8
Q

cranial nerves extend from

A

brain

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9
Q

spinal nerves extend from

A

spinal cord

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10
Q

a ganglion is a

A

cluster of neuron cell bodies in the PNS
6

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11
Q

What are the main characteristics of neurons?

A

Excitability, conductivity, secretion, extreme longevity, and amitotic.

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12
Q

What does “excitability” in a neuron mean?

A

Excitability is the neuron’s ability to respond to a stimulus, causing a change in the cell’s membrane potential.

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13
Q

What does “conductivity” in a neuron refer to?

A

Conductivity refers to the neuron’s ability to propagate electrical signals, with voltage-gated channels opening sequentially along the membrane.

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14
Q

What is “secretion” in the context of a neuron?

A

Secretion is the release of neurotransmitters in response to electrical activity, which then influence target cells.

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15
Q

What does “extreme longevity” mean for neurons?

A

Neurons can live throughout a person’s lifetime

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16
Q

What does “amitotic” mean in relation to neurons?

A

after fetal development, most neurons lose the ability to undergo mitosis and do not replicate.

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17
Q

What is the cell body (soma) of a neuron?

A

The cell body (soma) contains the nucleus, initiates some graded potentials, receives others from dendrites, and conducts these potentials to the axon.

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18
Q

What are dendrites?

A

Dendrites are short, unmyelinated processes that branch off the cell body and receive input to transfer to the cell body.

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18
Q

What is the function of the chromatophilic substance (Nissl bodies) in the neuron?

A

The Nissl bodies are made of ribosomes (free and bound) and are involved in protein synthesis within the neuron.

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19
Q

What is the function of the axon in a neuron?

A

The axon conducts action potentials and releases neurotransmitters at the synaptic knobs to communicate with other neurons, muscle cells, or glands

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20
Q

What is the axon hillock?

A

The axon hillock is the triangular region of the soma where the axon attaches to the cell body

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21
Q

What are axon collaterals

A

Axon collaterals are branches that extend from the main axon

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22
Q

What are telodendria (axon terminals)?

A

Telodendria are the fine branches at the end of the axon, which terminate in synaptic knobs.

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23
Q

What are synaptic knobs (terminal boutons)?

A

Synaptic knobs are the tips of telodendria that house synaptic vesicles containing neurotransmitter.

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24
Q

What are multipolar neurons

A

Multipolar neurons have many dendrites and one axon, and are the most common type of neuron.

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25
Q

What are bipolar neurons?

A

Bipolar neurons have one dendrite and one axon, and are found in limited numbers, such as in the retina of the eye.

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26
Q

What are unipolar (pseudounipolar) neurons?

A

Unipolar neurons have one process that extends from the cell body, which splits into a peripheral process (receptive dendrites) and a central process (leading to synaptic knobs in the CNS).

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27
Q

What are anaxonic neurons?

A

Anaxonic neurons have dendrites but no axons

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28
Q

What are sensory neurons (afferent neurons)

A

Sensory neurons conduct input from somatic and visceral receptors to the CNS, and most are unipolar (a few are bipolar).

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29
Q

What are motor neurons (efferent neurons)?

A

Motor neurons conduct output from the CNS to somatic and visceral effectors, and all are multipolar.

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30
Q

What are interneurons (association neurons)?

A

Interneurons receive, process, and integrate information from many other neurons, communicate between sensory and motor neurons, and are located within the CNS, making up 99% of our neurons. They are generally multipolar.

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31
Q

What is a synapse?

A

A synapse is the place where a neuron connects to another neuron or an effector.

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32
Q

What are the two types of synapses?

A

The two types of synapses are chemical and electrical, with chemical synapses being far more common.

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33
Q

What is an electrical synapse

A

An electrical synapse is where presynaptic and postsynaptic neurons are bound together by gap junctions, allowing for fast signal transmission without synaptic delay

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34
Q

What are the components of a chemical synapse?

A

A chemical synapse consists of a presynaptic neuron’s axon terminal, a synaptic cleft, and a postsynaptic neuron’s receptor.

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35
Q

What happens during synaptic communication?

A

Neurotransmitters are released from synaptic vesicles in the presynaptic neuron, diffuse across the synaptic cleft, and bind to receptors on the postsynaptic neuron, initiating a postsynaptic potential.

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36
Q

What is a synaptic delay?

A

A synaptic delay is the time it takes for neurotransmitter release, diffusion across the synaptic cleft, and receptor binding to occur.

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37
Q

What are glial cells?

A

Glial cells are nonexcitable support cells found in the CNS and PNS that protect and nourish neurons

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38
Q

How do glial cells compare in number to neurons?

A

Glial cells are approximately the same number as neurons in the nervous system.

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39
Q

What percentage of the nervous system’s volume do glial cells account for?

A

Glial cells account for about half of the volume of the nervous system.

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40
Q

What are some general characteristics of glial cells?

A

Glial cells are capable of mitosis, protect and nourish neurons, and provide physical scaffolding for nervous tissue.

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41
Q

What role do glial cells play during neural development?

A

Glial cells guide migrating neurons during development.

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42
Q

Why are glial cells critical for synapse function?

A

Glial cells are critical for normal function at neural synapses.

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43
Q

What shape are astrocytes, and where do their processes end?

A

Astrocytes are star-shaped cells, and their processes end in perivascular feet.

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44
Q

What is the most abundant glial cell in the CNS?

A

Astrocytes are the most abundant glial cell in the CNS.

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45
Q

How do astrocytes help form the blood-brain barrier?

A

Astrocytes wrap their feet around brain capillaries to help form the blood-brain barrier.

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46
Q

What do astrocytes regulate in the brain?

A

Astrocytes regulate tissue fluid composition, such as potassium concentration around neurons.

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47
Q

What structural role do astrocytes play in the CNS?

A

Astrocytes provide structural support for nearby neurons.

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48
Q

How do astrocytes assist in neuronal development?

A

Astrocytes assist in neuronal development and influence synaptic activity.

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49
Q

What happens to astrocytes when neurons die?

A

Astrocytes occupy the space of dying neurons.

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50
Q

Where are ependymal cells located, and what is their function?

A

Ependymal cells line cavities in the brain and spinal cord and are part of the choroid plexus, which produces cerebrospinal fluid.

51
Q

What is the role of microglia in the CNS?

A

Microglia are phagocytic cells that wander the CNS, replicate in infection, and remove debris.

52
Q

What do oligodendrocytes do in the CNS?

A

Oligodendrocytes have extensions that wrap around axons of neurons, forming the myelin sheath.

53
Q

What is the function of satellite cells in the PNS?

A

Satellite cells surround neuronal cell bodies in ganglia, electrically insulate them, and regulate the exchange of nutrients and wastes.

54
Q

What do neurolemmocytes (Schwann cells) do in the PNS?

A

Neurolemmocytes (Schwann cells) enclose PNS axons with myelin, allowing for faster action potential propagation.

55
Q

What is myelination and what is its purpose?

A

Myelination is the process of wrapping an axon with myelin, which insulates the axon and increases the speed of action potential propagation.

56
Q

What type of glial cells are responsible for myelination in the PNS?

A

Neurolemmocytes (Schwann cells) are responsible for myelination in the PNS.

57
Q

What are neurofibril nodes (nodes of Ranvier)?

A

Neurofibril nodes (nodes of Ranvier) are the gaps between neurolemmocytes that allow for faster signal transmission along the axon.

58
Q

When can PNS axons regenerate after traumatic injury?

A

PNS axons can regenerate if the neuron cell body is intact and enough neurilemma remains.

59
Q

What factors make PNS axon regeneration more likely to be successful?

A

Regeneration is more successful if the damage is less extensive and the distance between the injury site and the structure it innervates is shorter.

60
Q

What is the first step in axon regeneration after trauma?

A

The axon is severed by trauma.

61
Q

What happens to the axon proximal and distal to the injury site during axon regeneration?

A

Proximal to the cut, the axon seals off and swells; distal to the cut, the axon and sheath degenerate, but the neurilemma survives.

61
Q

What forms the regeneration tube during axon regeneration?

A

The neurilemma and endoneurium form a regeneration tube.

62
Q

How does the axon regenerate after injury?

A

The axon regenerates guided by nerve growth factors released by neurolemmocytes.

63
Q

What is the final step in axon regeneration?

A

The axon reinnervates the original effector or sensory receptor.

64
Q

Why is CNS axon regeneration extremely limited?

A

Oligodendrocytes secrete growth-inhibiting molecules instead of growth factors.

65
Q

What obstructs regrowth of axons in the CNS?

A

Large numbers of axons crowd the CNS, and scars from astrocytes and connective tissue obstruct regrowth

66
Q

What is the function of pumps in neurons?

A

Pumps maintain a concentration gradient by moving substances against their concentration gradient, requiring cellular energy

67
Q

Which pumps are found in the membranes of neurons?

A

Neurons have sodium-potassium pumps and calcium pumps.

68
Q

What is the function of channels in neurons?

A

Channels allow ions to m

69
Q

What are leak channels

A

Leak (passive) channels are always open, allowing continuous diffusion of ions.

70
Q

What are chemically gated channels?

A

Chemically gated channels are normally closed but open when a neurotransmitter binds.

71
Q

What are voltage-gated channels?

A

Voltage-gated channels are normally closed but open when the membrane charge changes.

72
Q

What is unique about voltage-gated Na+ channels?

A

Voltage-gated Na+ channels have activation and inactivation gates

73
Q

What types of channels are found in the receptive segment of a neuron?

A

The receptive segment contains chemically gated channels, such as chemically gated Cl– channels.

74
Q

What channels are found in the initial segment of a neuron?

A

The initial segment (axon hillock) has voltage-gated Na+ channels and voltage-gated K+ channels.

75
Q

What channels are found in the conductive segment of a neuron?

A

The conductive segment (axon and branches) has voltage-gated Na+ channels and voltage-gated K+ channels.

76
Q

What channels are found in the transmissive segment of a neuron?

A

The transmissive segment (synaptic knobs) has voltage-gated Ca2+ channels and Ca2+ pumps.

77
Q

What happens in the receptive segment (dendrites and cell body) of a neuron?

A

The receptive segment receives signals through chemically gated channels, generating graded potentials when neurotransmitters bind to receptors.

78
Q

What channels are involved in the receptive segment of a neuron?

A

Chemically gated channels (e.g., Cl– channels) that open when neurotransmitters bind to receptors.

79
Q

What occurs in the initial segment (axon hillock) of a neuron?

A

If the graded potential reaches threshold, voltage-gated Na+ channels open, leading to depolarization and initiating an action potential.

80
Q

What channels are involved in the initial segment (axon hillock)?

A

Voltage-gated Na+ channels and voltage-gated K+ channels.

81
Q

What happens in the conductive segment (axon and branches) of a neuron?

A

The action potential is propagated along the axon by sequential opening of voltage-gated Na+ and K+ channels, leading to depolarization and repolarization of the membrane.

82
Q

What channels are involved in the conductive segment of a neuron?

A

Voltage-gated Na+ channels and voltage-gated K+ channels.

83
Q

What occurs in the transmissive segment (synaptic knobs) of a neuron?

A

The action potential reaches the synaptic knobs, opening voltage-gated Ca2+ channels, causing neurotransmitter release into the synaptic cleft.

84
Q

What channels are involved in the transmissive segment (synaptic knobs)?

A

Voltage-gated Ca2+ channels and Ca2+ pumps.

85
Q

What triggers the release of neurotransmitters at the transmissive segment?

A

The influx of Ca2+ through voltage-gated Ca2+ channels at the synaptic knobs

86
Q

What are graded potentials?

A

Graded potentials are small, short-lived changes in the resting membrane potential (RMP).

87
Q

Where are graded potentials established in a neuron?

A

Graded potentials are established in the receptive segment of the neuron (dendrites and cell body) by the opening of chemically gated ion channels

88
Q

How long do graded potentials last?

A

Graded potentials are short-lived, typically lasting only a few milliseconds or less.

89
Q

Do graded potentials vary in size?

A

es, graded potentials vary in degree of change and direction of the resting membrane potential (RMP).

90
Q

Can graded potentials cause depolarization or hyperpolarization?

A

Yes, graded potentials can cause either depolarization (less negative) or hyperpolarization (more negative) of the membrane.

91
Q

Are graded potentials always the same size?

A

No, graded potentials can be large or small depending on the strength of the stimulus

92
Q

What are postsynaptic potentials

A

Postsynaptic potentials are graded potentials in a postsynaptic neuron, resulting from neurotransmitter binding.

93
Q

What is an excitatory postsynaptic potential (EPSP)?

A

An EPSP is a postsynaptic potential that results in depolarization of the postsynaptic neuron.

94
Q

What is an inhibitory postsynaptic potential (IPSP)?

A

An IPSP is a postsynaptic potential that results in hyperpolarization of the postsynaptic neuron.

95
Q

Can a postsynaptic neuron generate multiple postsynaptic potentials?

A

Yes, a postsynaptic neuron can generate multiple postsynaptic potentials because it can bind many neurotransmitter molecules simultaneously.

96
Q

What causes excitatory postsynaptic potentials (EPSPs)?

A

EPSPs are depolarizations caused by the entry of Na+ ions into the postsynaptic neuron.

97
Q

What causes inhibitory postsynaptic potentials (IPSPs)?

A

IPSPs are hyperpolarizations caused by K+ exit or Cl− entry into the postsynaptic neuron.

98
Q

Where does the summation of EPSPs and IPSPs occur, and what happens if the threshold is reached?

A

The summation occurs at the axon hillock; if the threshold (typically -55 mV) is reached, voltage-gated channels open, and an action potential is generated.

99
Q

threshold membrane
potential s

A

the minimum voltage change required

100
Q

What happens during depolarization of an action potential?

A

During depolarization, Na+ enters the neuron through voltage-gated Na+ channels, causing the membrane potential to become more positive.

101
Q

What is repolarization in an action potential?

A

Repolarization is the return of the membrane potential to a negative value as K+ exits the neuron through voltage-gated K+ channels.

102
Q

How is an action potential propagated down the axon?

A

An action potential is propagated by sequential opening of voltage-gated channels along the axolemma, generating a nerve signal or nerve impulse.

103
Q

What is the term for the propagation of action potentials along the axon?

A

The propagation of action potentials along the axon is called a nerve signal or nerve impulse.

104
Q

What ion movement is responsible for depolarization?

A

Depolarization is caused by the entry of Na+ into the neuron through voltage-gated Na+ channels.

105
Q

What ion movement is responsible for repolarization?

A

Repolarization is caused by the exit of K+ from the neuron through voltage-gated K+ channels.

106
Q

What happens during depolarization when Na+ enters from an adjacent region?

A

Voltage-gated Na+ channels open, allowing Na+ to enter the axon, causing the membrane potential to become positive.

107
Q

What causes the membrane to become positively charged during depolarization?

A

he entry of Na+ into the axon through voltage-gated Na+ channels causes the membrane to become more positive.

108
Q

What role do voltage-gated Na+ channels play in depolarization?

A

Voltage-gated Na+ channels open to allow Na+ to enter the axon, which leads to a positive shift in membrane potential.

109
Q

What triggers the opening of voltage-gated Na+ channels during depolarization?

A

The entry of Na+ from an adjacent region triggers the opening of voltage-gated Na+ channels, initiating further depolarization.

110
Q

What happens to Na+ channels during the inactivation state?

A

Na+ channels close and become inactive, meaning they are temporarily unable to open.

111
Q

How does the action potential continue to propagate after Na+ channels become inactive?

A

Steps 1 and 2 (Na+ entry and depolarization) repeat in adjacent regions, allowing the action potential to move toward the synaptic knob.

112
Q

What causes the action potential to move toward the synaptic knob?

A

The sequential opening of voltage-gated Na+ channels and the depolarization of adjacent regions cause the action potential to propagate toward the synaptic knob.

113
Q

What is the role of Na+ channel inactivation in the propagation of the action potential?

A

Na+ channel inactivation ensures the unidirectional flow of the action potential by preventing backward movement.

114
Q

What happens during the depolarization phase of an action potential?

A

Depolarization opens Na+ channels, causing Na+ to enter the cell and the membrane potential to become more positive.

115
Q

What occurs when K+ channels open during repolarization?

A

K+ ions diffuse out of the cell, causing the membrane potential to become more negative (repolarization).

116
Q

What causes hyperpolarization during the action potential?

A

K+ channels remain open longer than needed, allowing more K+ to exit, making the membrane potential more negative than the resting membrane potential.

117
Q

How is the resting membrane potential (RMP) reestablished after hyperpolarization?

A

K+ channels close, and the Na+/K+ pump restores the RMP by pumping Na+ out and K+ back into the cell.

118
Q

How does repolarization propagate the action potential?

A

Steps 3-5 (K+ exit and membrane potential changes) repeat in adjacent regions, propagating the action potential toward the synaptic knob.

119
Q

What is the role of K+ channels in action potential propagation?

A

K+ channels help repolarize the membrane by allowing K+ to exit, returning the cell to a negative potential and enabling the action potential to move forward

120
Q

What happens when an action potential reaches the synaptic knob?

A

It opens voltage-gated Ca2+ channels, allowing Ca2+ to diffuse into the synaptic knob.

121
Q

What is the role of Ca2+ in neurotransmitter release?

A

Ca2+ binds to proteins associated with synaptic vesicles, triggering exocytosis of neurotransmitters.

122
Q

What occurs during exocytosis at the synaptic knob?

A

Synaptic vesicles fuse with the membrane, releasing neurotransmitters into the synaptic cleft

123
Q

How do neurotransmitters affect the postsynaptic cell?

A

Neurotransmitters bind to ligand-gated receptors on the postsynaptic cell, initiating a response.

124
Q

Can a neuron release multiple types of neurotransmitters?

A

Yes, neurons can synthesize more than one neurotransmitter, but only one type is released at a time, depending on the action potential frequency.

125
Q

How does the frequency of action potentials affect neurotransmitter release?

A

The frequency of action potentials influences how much neurotransmitter is released, as higher frequencies lead to more vesicles being released.

anatomy and physiology (17 decks)

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