Module 7: The Nervous System Flashcards
(117 cards)
1
Q
What makes up the central nervous system (CNS)?
A
The brain and spinal cord, which are encased in bone.
2
Q
Where is the brain located?
A
The cranial vault of the skull.
3
Q
Where is the spinal cord located?
A
It is encased in the vertebral canal, which is formed by the vertebral bones.
4
Q
What makes up the peripheral nervous system (PNS)?
A
All the parts of the nervous system not in the CNS, such as nerves and ganglia.
5
Q
Nerve
A
A bundle of neuron axons and their coverings which extend from the CNS.
6
Q
Ganglia
A
Collections of neuron cell bodies that are found outside the CNS.
7
Q
What are the two basic kinds of nerves?
A
Spinal nerves and cranial nerves.
8
Q
Spinal nerves
A
Nerves that originate from the spinal cord.
9
Q
Cranial nerves
A
Nerves that originate from the brain.
10
Q
How many total nerves make up the PNS?
A
There are 43 pairs of nerves.
11
Q
How many pairs of cranial nerves make up the PNS?
A
12 pairs.
12
Q
How many pairs of spinal nerves make up the PNS?
A
31 pairs.
13
Q
What two divisions can the neurons of the PNS be separated into?
A
The neurons can be split into the afferent division and the efferent division.
14
Q
Afferent neurons
A
Neurons that transmit action potentials from the sensory organs to the CNS.
15
Q
Efferent neurons
A
Neurons that transmit action potentials from CNS to the effector organs.
16
Q
What does the afferent division (the sensory division) do?
A
It carries signals from the sensory organs, such as the skin, eyes, ears, nose, and tongue toward the CNS. This allows the CNS to process the information collected by the sensory organs. It can also carry signals from the internal organs.
17
Q
What does the efferent division (the motor division) do?
A
It carries signals from the CNS to effector organs, which are the muscles and glands.
18
Q
What two parts can the efferent division of the PNS be divided into?
A
The somatic motor nervous system (SMNS) and the autonomic nervous system (ANS).
19
Q
Somatic motor nervous system
A
PNS neurons that transmit action potentials from the CNS to skeletal muscles.
20
Q
Autonomic nervous system
A
PNS neurons that transmit action potentials from the CNS to smooth muscles, cardiac muscles, and glands.
21
Q
Which part of the nervous system exercises control over the voluntary muscles?
A
The somatic motor nervous system (SMNS).
22
Q
Which part of the nervous system exercises control over involuntary functions?
A
The autonomic nervous system (ANS).
23
Q
What two divisions can the autonomic nervous system (ANS) be divided into?
A
The sympathetic division and the parasympathetic division.
24
Q
Sympathetic division
A
Division of the ANS that generally prepares the body for increased energy expenditure.
25
Parasympathetic division
Division of the ANS that regulates resting and nutrition-related functions such as digestion, defecation, and urination.
26
What is another term that describes the sympathetic division of the ANS?
The fight-or-flight division.
27
Name some functions of the sympathetic division of the ANS.
Increases the rate and strength of the heartbeat, raises blood pressure, and stimulates the liver to release glucose into the blood, which produces quick energy.
28
What is a term that describes the functions of the parasympathetic division of the ANS?
The rest-repose or "housekeeping" division.
29
Name some of the functions of the parasympathetic division of the ANS.
It slows the heart rate and lowers the blood pressure, takes care of nutrition-related activities such as causing the smooth muscles in the stomach to contract during digestion, and causes some glands, such as the salivary glands and lacrimal glands, to secrete.
30
What are the two basic types of cells that make up the nervous system?
Neurons and neuroglia.
31
What are the three basic units of a neuron?
The cell body (soma), axons, and dendrites.
32
What cell organelles are found in the cell body of a neuron?
The nucleus, mitochondria, and Golgi apparatuses.
33
Why are there so many mitochondria in the cell body of a neuron?
Neurons use a lot of energy in the form of ATP, and after 4-8 minutes without oxygen, neurons die.
34
How does a neuron make and transport its neurotransmitters?
Neurons make neurotransmitters in the cell body with the Golgi apparatuses and then send them all the way down the axon where they are secreted from the synaptic vesicles in the presynaptic terminals.
35
What are the two types of processes in a neuron?
Dendrites and axons.
36
What is the difference between a dendrite and an axon?
Dendrites are shorter and bring messages into the cell. The axon sends action potentials away from the cell body.
37
Where does the action potential begin and end in a neuron?
It begins at the axon hillock and travels all the way down to the far end of the axon.
38
The axon hillock
The area that marks the end of the cell body and the beginning of the axon.
39
Myelin sheath
A fatty wrapping that speeds up the conduction of the action potential down the axon.
40
What produces the myelin sheath that surrounds an axon?
The neuroglia, which have extensions that surround portions of the axon.
41
When a neuron is in the PNS, what are the myelin-sheath-producing neuroglia called?
Schwann cells.
42
When a neuron is in the CNS, what are its myelin-sheath-producing neuroglia cells called?
Oligodendrocytes.
43
Nodes of Ranvier
Gaps in the myelin sheath of an axon.
44
What are some other names for presynaptic terminals in an axon?
Terminal boutons or axon terminals.
45
How are neurons classified?
By their number of processes.
46
Unipolar
A neuron with only one process, and the cell body is suspended from that process.
47
What type of neurons are usually unipolar?
Afferent neurons (neurons that carry signals from the sensory receptors to the CNS).
48
Bipolar neuron
A neuron with two processes: one axon and one single dendrite split into many branches.
49
What type of neurons are usually bipolar?
Specialized afferent neurons, such as the ones that send information from the eyes to the brain.
50
Multipolar neurons
Neurons with many processes, several dendrites, but only one axon.
51
What type of neurons are usually multipolar?
Motor neurons or association neurons.
52
Association neuron
A neuron that conducts action potentials from one neuron to another neuron within the CNS.
53
What part of the nervous system to motor neurons belong to?
The efferent division of the PNS because they send signals to effector cells such as muscle cells.
54
What part of the of the nervous system do association neurons belong to?
They are part of the CNS.
55
What type of cell is like the connective tissue of the nervous system?
The neuroglia.
56
Describe the basic composition of neuroglia and neurons in the brain.
There are about nine neuroglia for every neuron, but because neuroglia are smaller than neurons, they only make up a little over half of the brain's mass.
57
What is the job of an oligodendrocyte?
They bind neurons together and insulate the axons in the CNS.
58
What is the job of a Schwann cell?
Schwann cells insulate axons in the PNS.
59
What is the difference between an oligodendrocyte and a Schwann cell?
The oligodendrocyte is in the CNS, and the Schwann cell is in the PNS. Also, while oligodendrocytes wrap around several axons, Schwann cells wrap around only a portion of one axon.
60
What is the job of microglia?
They engage in phagocytosis to fight infections.
61
What is the job of astrocytes?
They form the blood-brain barrier.
62
Why can't blood vessels reach the brain?
Many of the substances in the blood which other parts of the body need are toxic to neurons.
63
What is the function of non-ciliated ependymal cells?
They secrete cerebrospinal fluid.
64
What is the function of ciliated ependymal cells?
They move the cerebrospinal fluid around in the brain and spinal cord.
65
What is the purpose of cerebrospinal fluid?
It bathes brain and spinal cord tissue and provides a protective cushion around the CNS.
66
Why do nerves look white?
They are wrapped in the epineurium.
67
Epineurium
A collagen layer/connective tissue covering on the top of a nerve.
68
Describe the structure of a nerve.
The epineurium encases several bundles of axons, and each bundle, called a fascicle, is wrapped together in the perineurium, which wraps the smaller bundle. Each axon of the bundle is wrapped, not only in its Schwann cells, but in the endoneurium.
69
What are the three classifications of nerves?
Sensory, motor, and mixed.
70
Sensory nerve
A nerve made purely of sensory neurons that send signals from a sensory organ to the CNS.
71
Motor nerve
A nerve made purely of motor neurons which send signals from the CNS out to the effector muscle or organ.
72
Mixed nerve
A nerve made of both sensory and motor neurons.
73
What are the three conditions that must be fulfilled for a nerve to heal?
1) The nerve's cells must be alive. 2) The two parts of the severed nerve must be lined up. 3) Schwann cells must cover the axons of the nerve.
74
How do Schwann cells aid in the healing process of a nerve?
When an axon in the PNS gets severed, the part still attached to the cell body begins branching to try to find the other end. Schwann cells form a tube-like path that guides the branching axon.
75
Why can't oligodendrocytes aid in healing an axon?
The process of guiding the axon to its target takes many cells, but oligodendrocytes each surround and insulate several axons, so they cannot form a track.
76
Excitability
The ability to undergo an action potential in response to a stimulus.
77
What are the two types of excitable cells in the body?
Muscle cells and neurons.
78
Potential difference
A measure of the charge difference across the cell membrane.
79
What causes the electrochemical phenomenon of an action potential?
Movements of ions cause the electrical signal.
80
What does the term "at rest" mean with reference to an axon?
It means that there are no action potentials running down the axon at that point.
81
Describe the charges of an axon inside and outside the plasma membrane during the resting potential.
The outside of the axon has a positive charge, and the inside of the axon has a negative charge.
82
Sodium-potassium exchange pump
The active transport process that brings K+ through the plasma membrane into the axon and Na+ out of the plasma membrane.
83
Summarize the state of axon during resting potential.
Sodium and potassium channels are closed. Na+ are concentrated outside the cell; K+ are concentrated inside the cell.
84
Describe the state of an axon during depolarization.
Sodium channels open in response to a stimulus. Na+ rush into the cell according to the dictates of diffusion.
85
Describe the state of an axon during repolarization.
Na+ channels close, and K+ channels open. K+ rush out of the cell according to the dictates of diffusion.
86
Describe the state of an axon while resting conditions are reestablished.
Na+ and K+ channels are closed. Sodium-potassium exchange pump moves Na+ out and K+ in.
87
What is the potential difference during resting potential?
-85mV.
88
What is the potential difference at the end of depolarization?
+30mV.
89
What is the potential difference at the end of repolarization?
Slightly below -85mV.
90
What is the potential difference once resting conditions are reestablished in an axon?
-85mV.
91
Local potential
A local potential is a small change in the potential difference that dies out because the stimulus that produced it was subthreshold.
92
What does the intensity of a feeling depend upon: the frequency of an action potential or the size of the action potential?
The frequency.
93
What direction does an action potential travel in an axon?
It travels from the axon hillock down to the end of the axon.
94
Refractory period
The time when no action potential can be generated on the neuron because one is already in progress.
95
What is the difference between the absolute refractory period and the relative refractory period?
The absolute period, no matter how strong the stimulus, cannot generate another action potential. However, the relative period is not really ready to generate another action potential, but it can if the stimulus is strong enough.
96
What is the difference between a myelinated and unmyelinated axon?
Myelinated: Many Schwann cells thickly encase one axon.
Unmyelinated: Schwann cells thinly encase several axon.
97
What type of conduction occurs on an unmyelinated axon?
Continuous conduction
98
How does the action potential travel on an axon with continuous conduction?
The action potential must travel across the entire axon, each action potential stimulating the response of the next little section of the axon.
99
What type of conduction is used on a myelinated axon?
Saltatory conduction.
100
How does the action potential travel with saltatory conduction?
The action potential leaps from one node of Ranvier to another, and it does not need to travel through the portions of the axon that are covered with the Schwann cells.
101
How does the width of an axon affect the speed at which the action potential can travel?
Larger diameter axons conduct action potential faster because they offer less electrical resistance.
102
Inhibitory synapses
Synapses that stop information from passing to the next neuron.
103
What are the two basic kinds of neuron-to-neuron chemical synapses?
Excitatory synapses and inhibitory synapses.
104
What type of response does an excitatory synapse create?
An excitatory postsynaptic potential.
105
What type of response does an inhibitory synapse create?
An inhibitory postsynaptic potential.
106
What are the two ways an action potential can be stimulated on the postsynaptic neuron of an excitatory synapse?
Through temporal summation or spatial summation.
107
Where do the subthreshold stimuli come from in temporal summation?
The stimuli are all produced by one presynaptic neuron in a small window of time.
108
Where do the subthreshold stimuli come from in spatial summation?
The stimuli come from several different axons which carry an action potential to the same neuron all at once.
109
Why is the synapse called a gatekeeper?
It facilitates the transmission of action potentials and regulates what stimuli make it to the nervous system. This allows the nervous system to process the important information and ignore the rest.
110
Hyperpolarization
A change that takes the neuron farther away from producing an action potential. It is the opposite of depolarization.
111
If a neurotransmitter-receptor interaction opens K+ channels, what type of synapse is it?
It is an inhibitory synapse.
112
If a neurotransmitter-receptor interaction opens Na+ channels, what type of synapse is it?
It is an excitatory synapse.
113
Neural circuit
A neural arrangement in the nervous system.
114
Describe the input and output of a converging circuit.
Many inputs are reduced to a limited output.
115
Describe the input and output of a diverging circuit.
There is one input and many outputs.
116
Describe the input and output of an oscillating circuit.
A neuron sends a signal that returns to itself.
117
After-discharge response
A single stimulus that is regenerate within a neural circuit over and over to prolong the stimulus's effect.
