Chapter 12 Flashcards
1
Q
brain
A
part of the CNS that is located in the skull
2
Q
cranial nerves
A
nerves that emerge from the brain and spinal cord (12 pairs)
3
Q
nerve
A
bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord
4
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spinal cord
A
part of the CNS; connected to the brain; contains 100 million neurons
5
Q
spinal nerves
A
nerves that emerge from the spinal cord (31 pairs)
6
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ganglia
A
small masses of nerves tissue (consisting primarily of neutron cell bodies) that are located outside the brain and spinal cord
7
Q
enteric plexus
A
extensive networks of neutrons located in the walls of organs of the GI tract; help regulate the digestive system
8
Q
sensory receptor
A
a structure of the nervous system that monitors change in the external or internal environment (i.e. touch receptors in the skin)
9
Q
sensory function of nervous system
A
sensory receptors detect internal stimuli (i.e. increase in BP) or external stimuli (i.e. something touching your arm)
10
Q
integrative function of nervous system
A
nervous system processes sensory info by analyzing it and making decisions for appropriate responses
11
Q
motor function of nervous system
A
once sensory info is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves. Stimulation of the effectors causes muscles to contract and glands to secrete
12
Q
Effector
A
muscles and glands
13
Q
electrical excitability
A
the ability to respond to a stimulus and covert it into an action potential
14
Q
action potential/ nerve impulse
A
electrical signal that propagates along the surface of the membrane of a neuron
15
Q
neuron
A
nerve cell
16
Q
cell body (perikaryon or soma) of a neuron
A
contains a nucleus surrounded by cytoplasm that includes typical cellular organelles i.e. lysosomes, mitochondria and and Golgi Complex
17
Q
Nissl bodies
A
prominent clusters of rough endoplasmic reticulum within the cell body; used to replace cellular components, and to regenerated damaged axons in the PNS
18
Q
dendrite
A
receiving/input portion of a neuron; contain receptor sites for binding chemical messengers from other cells
19
Q
axon
A
propagates nerve impulses toward another neuron, muscle fibre or gland cell; long, thin, cylindrical projection; contains mitochondria, microtubules and neurofibrils but NO rough ER so protein synthesis does NOT occur here
20
Q
axon hillock
A
the cone shaped elevation where the axon meets the cell body
21
Q
initial segment
A
the part of the axon closes to the axon hillock
22
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trigger zone
A
junction of the axon hillock and the initial segment; most nerve impulses arise here
23
Q
axon collateral
A
side branches of the axon
24
Q
axon terminal
A
fine processes that the axon and its collaterals end by dividing into
25
synapse
the site of communication between two neurons or between a neuron and an effector cell
26
synaptic end bulb
bulb shaped structures that the tips of some axon terminals swell into
27
synaptic vesicle
tiny membrane enclosed sacs that store neurotransmitters
28
neurotransmitter
chemical that excites or inhibits another neuron
29
structural diversity of neurons
neurons display diversity in size and shape
30
multipolar neuron
have several dendrites and one axon; i.e. brain and spinal cord and motor neurons
31
bipolar neuron
one main dendrite and one axon i.e. retina of eye, inner ear and olfactory parts of the brain
32
unipolar neuron
have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body
33
neuroglia or glia
don't propagate action potentials but they can divide and multiply in the mature nervous system
34
astrocytes
star shaped neuroglia, largest and most numerous neuroglia
35
oligodendrocytes
small neuroglia, responsible for forming and maintaining the myelin sheath around CNS axons
36
myelin sheath
multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction
37
myelinated
axons that are covered in myelin sheath
38
microglia
neuroglia cells that function as phagocytes to remove cellular debris formed during normal development of nervous system
39
ependymal cells
cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia; line ventricles of the brain and central canal of the spinal cord; produce and assist the circulation of cerebrospinal fluid
40
Schwann cells
cells that encircle PNS axons; each cell myelinated a single axon
41
satellite cells
flat cells that surround the cell bodies of neurons of PNS ganglia; provide structural support and regulates exchanges of materials between neuronal cell bodies and interstitial fluid
42
nodes of ranvier
gaps in the myelin sheath at intervals along the axon
43
white matter
composed primarily of myelinated axons (myelin is white)
44
gray matter
contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia
45
nucleus
a cluster of neuronal cell bodies located in the CNS
46
Central Nervous System (CNS)
consists of the brain and spinal cord
47
brain and spinal cord connection
spinal cord is connected to the brain through the foramen magnum of the occipital bone and is encircled by the bones of the vertebral column
48
Peripheral Nervous System (PNS)
consists of all nervous tissue outside the CNS. Components include nerves, ganglia, enteric plexuses and sensory receptors
49
somatic nervous system (SNS)
Division of PNS that consists of sensory neurons that convey info from somatic receptors in the head, body wall, and limbs and from receptors for the special senses of vision, hearing, taste and smell to the CNS and motor neurons that conduct impulses from the CNS to the skeletal muscles only. VOLUNTARY ACTIONS
50
Autonomic Nervous System (ANS)
division of PNS; consists of sensory neurons that convey info from autonomic sensory receptors (located mostly in visceral organs i.e. stomach and lungs) to the CNS and motor neurons that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle and glands; INVOLUNTARY ACTIONS
51
sympathetic division
division of ANS; fight or flight responses (support exercise and emergency actions)
52
parasympathetic division
division of ANS; rest and digest activities
53
Enteric Nervous System (ENS)
operation of the brain and gut; sensory neurons of ENS monitor chemical changes within the GI tract as well as the stretching of the walls; enteric motor neurons govern contraction of GI tract smooth muscle to propel food through the GI tract, secretion of the GI tract organs (i.e. acid from the stomach) and activity of GI tract endocrine cells (secrete hormones)
54
electrochemical gradient
a concentration (chemical) difference plus an electrical difference
55
leak channel
gates randomly alternate between open and closed positions
56
gated channel
ion channels open and close due to the presence of gates; the gate is part of the channel protein that can seal the channel pore shut or move aside to open the pore
57
ligand-gated channel
opens and closes in the response to the binding of a ligand (chemical) stimulus- including neurotransmitters, hormones and particular ions
58
mechanically gated channel
opens or closes in response to mechanical stimulation in the form of vibration (i.e. sound waves), touch, pressure, or tissue stretching; the force distorts the channel from its resting position, opening the gate
59
voltage gated channel
opens in response to a change in membrane potential (voltage); participate in generation and conduction of action potentials in the axons of all types of neurons
60
polarized
a cell that exhibits a membrane potential
61
graded potential
a small deviation from the membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative)
62
hyperpolarizing graded potential
when the response makes the membrane more polarized (inside more negative)
63
depolarizing graded potential
when the response makes the membrane less polarized (less negative)
64
decremental conduction
the mode of travel by which graded potentials die out as the spread along the membrane
65
summation
the process by which graded potentials add together (i.e. two depolarizing potentials = a larger depolarizing graded potential)
66
action potential (AP)
a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state
67
threshold
an action potential occurs in the membrane of the axon of a neutron when depolarization reaches a certain potential (around -55mV for most neurons)
68
all or none principle
an action potential either occurs completely or it does not occur at all
69
depolarizing phase
when membrane potentials of axon reaches threshold, Na+ channel activation gates open. As Na+ ions move through these channels into neuron, buildup of positive charges form along inside surface of membrane and membrane becomes depolarized
70
repolarizing phase
Na+ channel inactivation gates close and K+ channels open. Membrane starts to become depolarized as some K+ ions leave the neuron and few negative charges begin to build up along inside surface of membrane. K+ outflow continues. As more K+ ions leave neuron, more negative charges build up along inside surface of membrane. K+ outflow eventually restores resting membrane potential. Na+ channel inactivation gates open. Return to resting state occurs when K+ gates close
71
after hyper polarizing phase
while K+ channels are open, outflow of K+ may be large enough to cause this phase; the voltage gated K+ channels remain open and the membrane potential becomes even more negative (around -90mV)
72
refractory period
the period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus
73
absolute refractory period
period of time after an action potential begins where even a very strong stimulus cannot initiate a second action potential
74
relative refractory period
the period of time during which a second action potential can be initiated , but only by a larger than normal stimulus
75
nerve impulse propagation
an action potential keeps it's strength as it spreads along the membrane
76
continuous conduction
step by step depolarization and depolarization of each adjacent segment of the plasma membrane; occurs in unmyelinated axons and muscle fibres
77
saltatory conduction
special mode of action potential propagation that occurs along myelinated axons; occurs because of uneven distribution of voltage cared channels
78
effect of axon diameter on propagation speed
larger diameter axons propagate action potentials faster than smaller ones due to larger surface area
79
encoding of stimulus intensity
frequency of action potentials and number of sensory neurons recruited (activated) by the stimulus
80
comparison of electrical signals produced by excitable cells (action potential vs. graded potential)
action potential permits communication over long distances; graded potential only short distances since they aren't propagated. (table on page 472)
81
presynaptic neuron
a nerve cell that caries a nerve impulse towards a synapse
82
postsynaptic neuron
a nerve cell that carries a nerve impulse away from a synapse or an effector cell that responds to the impulse at the synapse
83
electrical synapse
action potentials (impulses) conduct directly between the plasma membranes of adjacent neurons
84
gap junction
action potentials conduct directly between the plasma membranes of adjacent neurons through a gap junction
85
chemical synapse
action potentials conduct over the synaptic cleft using neurotransmitters that diffuse across the synaptic cleft
86
synaptic cleft
a space between the presynaptic and postsynaptic neurons; filled with interstitial fluid
87
postsynaptic potential
a type of graded potential produced when the postsynaptic neuron receives the chemical signal
88
Excitatory Postsynaptic Potential (EPSP)
a depolarizing postsynaptic potential
89
Inhibitory Postsynaptic Potential (IPSP)
a hyperpolarizing postsynaptic potential
90
Neurotransmitters are removed from the synaptic cleft in 3 ways:
1. Diffusion: diffuse away from the synaptic cleft
2. Enzymatic Degradation: inactivated by enzyme
3. Uptake by cells: actively transported back into the neuron that released them (reuptake)
91
spatial summation
summation of postsynaptic potentials in response to stimuli that occur at different locations
92
temporal summation
summation of postsynaptic potentials in response to stimuli that occur at the same location in the membrane of the postsynaptic cell but at different times
93
summation of EPSP
if the total excitatory effects are greater than the total inhibitory effects but less than the threshold level of stimulation= an EPSP that does not reach threshold
94
summation of nerve impulses
if the total excitatory effects are greater than the total inhibitory effects and threshold is reached, one or more nerve impulses will be triggered (will continue as long as EPSP is at or above threshold level)
95
summation of IPSP
if the total inhibitory effects are greater than the excitatory effects, the membrane hyperpolarizes (IPSP) = the inhibition of the postsynaptic neuron and an inability to generate a nerve impulse
96
acetylcholine
small molecule neurotransmitter; excitatory where binding to receptors opens cation channels; inhibitory when binding opens K+ channels; CNS and PNS
97
amino acids
neurotransmitters in the CNS; i.e. Glutamate, Aspartate,
98
glutamate
small molecule neurotransmitter; excitatory
99
glycine
small molecule neurotransmitter; inhibitory
100
biogenic amines
modified amino acid and decarboxylated (carboxyl group removed); norepinephrine, epinephrine, dopamine and serotonin
101
norepinephrine
biogenic amine; plays role in arousal (awakening), dreaming and regulating mood
102
epinephrine
aka adrenaline; biogenic amine; plays role in arousal; smaller number of neurons in the brain use epinephrine over norepinephrine
103
dopamine
biogenic amine; emotional responses, addictive behaviours, pleasurable experiences
104
catecholamines
chemical classification of norepinephrine, dopamine and epinephrine; include an amino group (NH2) and a catechol ring composed of 6 C and two adjacent hydroxyl (OH) groups
105
serotonin
small molecule neurotransmitter; biogenic amine; involved in sensory perception, temperature regulation, control of mood, appetite and induction of sleep
106
Nitric oxide
small molecule neurotransmitter; excitatory neurotransmitter in the brain, spinal cord and adrenal glands and nerves to the penis; widespread effects throughout the body
107
neuropeptides
neurotransmitters consisting of 3-40 amino acids linked by peptide bonds; numerous and widespread in CNS and PNS
108
neural circuit
networks of neurons in the CNS that process specific types of info
109
simple series
presynaptic neuron stimulates a single postsynaptic neuron, the second neuron stimulates another and so on
110
diverging circuit
the nerve impulses from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit; amplifies the signal
111
converging circuit
the postsynaptic neuron receives nerve impulses from several different sources
112
reverberating circuit
the stimulation of the presynaptic cell causes the postsynaptic cell to transmit a series of nerve impulses; the incoming impulse stimulates the first neuron, which stimulates the second which stimulates the third and so on. Branches from later neurons synapse with earlier ones
113
parallel after-discharge circuit
a single presynaptic cell stimulates a group of neurons, each of which synapses with a common postsynaptic cell. A differing number of synapses between first and last neurons imposes varying synaptic delays so that the last neuron exhibits multiple EPSPs or IPSPs. If input is excitatory, the postsynaptic neuron then can send out a stream of impulses in quick succession
114
plasticity
the capability to change based on experience; changes include sprouting of new dendrites, synthesis of new proteins and changes in synaptic contacts with other neurons
115
neurogenesis
the birth of new neurons from undifferentiated stem cells
116
damage and repair in the PNS
meylinated axons in the peripheral nervous system may be repaired if the cell body remains intact and if Schwann cells remain active
117
multiple sclerosis (MS)
disease causes a progressive destruction of myelin sheaths surrounding neurons of the CNS
118
epilepsy
short, recurrent attacks of motor, sensory or psychological malfunctions
