Chapter 11: Nervous System Flashcards
1
Q
what are the 3 divisions of the nervous system?
A
- central (CNS)
- Peripheral (PNS)
- Enteric (ENS)
2
Q
what makes up the CNS?
A
brain and spinal cord
3
Q
what is the function of the CNS?
A
information processing (integrate and process, then coordinate motor and sensory commands)
4
Q
what makes up the PNS?
A
all nervous tissue outside CNS (excluding ENS)
5
Q
what makes up the ENS?
A
nervous tissue in wall of gastrointestinal tract
6
Q
what is the function of the ENS?
A
help control digestive function
7
Q
what are the 2 divisions of the PNS?
A
- sensory afferent division
2. motor efferent division
8
Q
what is the function of the sensory division of PNS?
A
bring info from receptors to CNS
9
Q
where is the sensory division of PNS most prominent?
A
sensory organs (Smell, taste, sight, balance, hearing0
10
Q
what is the function of the motor division of the PNS?
A
carry motor commands form CNS
11
Q
what 2 groups is the motor division of PNS divided into?
A
- somatic (SNS)
2. autonomic (ANS)
12
Q
what is the autonomic nervous system?
A
involuntary, automatically regulates
13
Q
what is the somatic nervous system?
A
voluntary, conscious control of movement
14
Q
receptors
A
detect changes in internl/external environment
15
Q
____ respond to commands of CNS
A
effectors
16
Q
what are the 3 regions of a neuron?
A
- dendrites
- cell body
- axon
17
Q
dendrites
A
receive stimuli from environment/other neurons
18
Q
cell body
A
contains nucleus and other organelles
19
Q
axon
A
carries information towards other cells
20
Q
axon hillock
A
origin of axon form cell body
21
Q
initial segament of axon hillock
A
where AP originates
22
Q
axolemma
A
axon plasmalemma
23
Q
axoplasm
A
axon cytoplasm
24
Q
what is contained in the axoplasm?
A
neurofibrils, neurotubules, vessicles, lysosomes, mitochndria, enxymes
25
synapse
where neuron communicates with another cell
26
neurotransmittors are packaged in ___ in axon terminals
synaptic vessicles
27
____ allow a single neuron to communicate with multiple cells
collateral branches
28
what are the 3 types of synapses?
1. between neurons
2. neuromuscluar
3. neuroglandular
29
most CNS neurons lack ___ and cannot divide
centrioles
30
some neural stem cells exist, but most are ___
inactive
31
neural stem cells are active in which 3 places?
1. olfactory epithelium (smell)
2. retina of eye (vision)
3. hippocampus (memory)
32
what are the 4 anatomical classes of neurons?
1. anaxonic neurons
2. bipolar neurons
3. unipolar neurons
4. multipolar neurons
33
structure of anaxonic neurons
small, dendrites indistinguishable from axon
34
location of anaxonic neurons
brain and special sense organs
35
functions of anaxonic neurons
poorly understood
36
structure of bipolar neurons
branching dendritic process and axon with cell body in middle (small)
37
location of bipolar neurons
special sense organs (rare)
38
structure of unipolar neurons
dendrites and axon continuous (very long, can extend from toes to spine) cell body off to one side
39
initial segment of unipolar neuron
where dendrites converge (rest is axon)
40
location of unipolar neurons
most sensory neurons in PNS
41
structure of multipolar neurons
2/more dendrites and a single axon, can be as long as unipolar neurons
42
location of multipolar neurons
most common neurons in CNS
43
all motor neurons to skeletal muscles are
multipolar neurons
44
what are the 3 functional classes of neurons?
1. sensory
2. interneurons
3. motor neurons
45
which functional class of neuron is most abundant?
interneurons
46
function of sensory receptors
detect stimuli
47
structure of sensory receptors
processes of sensory neurons or cells monitored be sensory neurons
48
what are the 3 types of sensory receptors?
1. interoceptors
2. proprioreceptors
3. exteroceptors
49
interoreceptors monitor ____ and detect ___,___, and ___
internal organs; distension (stretch), deep pressure, pain
50
proprioreceptors monitor __
position/movement of skeletal muscles and joints
51
exteroreceptors monitor __
external environment (touch, temp, pressure, special senses)
52
function of afferent fibers
carry info to CNS
53
ganglion structure
collection of neuron cell bodies in PNS
54
sensory neurons are mostly ___ neurons with cell bodies in ___
unipolar; sensory ganglia
55
somatic sensory neurons monitor ___
outside world and body
56
visceral sensory neurons monitor ___
internal conditions and organs
57
interneurons are located in the ___, usually between ___ and ___ neurons
CNS; sensory and motor
58
function of interneurons
receive information from PNS and CNS; higher functions like learning and memory
59
somatic motor neurons innervate ___ and provide ___ control
skeletal muscles; conscious
60
the cell body of a somatic motor neuron in in the __ and the axon extends within a ___
CNS: peripheral nerve
61
what is a nerve?
bundle of axons in the PNS
62
visceral motor neurons are part of the __ nervous system
autonomic
63
visceral motor neurons innervate ____, including ___ (4)
all other effectors; smooth, cardiac, glands, adipose tissue
64
visceral motor neurons are located in the ___ nervous system(s)
CNS/PNS
65
autonomic ganglia
location of cell bodies for visceral motor neurons going to peripheral receptors
66
function of efferent fibers
carry info from CNS to effectors
67
what are somatic effectors?
skeletal muslces
68
what are visceral effectors?
cardiac/smooth muscle, glands
69
function of neuroglia
support/protect neurons
70
____ comprise half of the total volume of nervous system
neuroglia
71
4 types of CNS glial cells
1. ependymal cells
2. microglia
3. astrocytes
4. oligodendrocytes
72
location of ependymal cells
lining central canal (spine) and ventricles (brain)
73
function of ependymal cells
produce, circulate, monitor cerebrospinal fluid (CSF)
74
structure of microglia
mobile phagocytic cells
75
function of microglia
remove cellular debris, waste, and pathogens
76
5 functions of astrocytes
1. maintain blood-brain barrier
2. structural support
3. regulate ion, nutrient, and gas concentration around neurons
4. absorb/recycle neurotransmitters
5. make scar tissue
77
2 functions of oligodendrocytes
1. provide CNS framework by stabalizing axons
| 2. produce myelin
78
how do oligodendrocytes produce the myelin sheath?
cell process wraps axon in layers of myelin and PM
79
function of myelin sheath
speeds up nerve conduction
80
myelinated axons appear __ because of the __ content of the myelin
white; lipid
81
parts of axon with myelin are called
internodes
82
parts of axon without myelin are called
nodes of Ranvier
83
parts of CNS that are unmyelinated appear _-
grey
84
2 types of neuroglia in PNS
1. schwaan cells
| 2. satellite cells
85
location of schwaan cells
cover peripheral axons
86
function of schwaan cells
participate in axon repair
87
location of satellite cells
surround peripheral cell bodies
88
function of satellite cells
regulate environment around neurons
89
the function of satellite cells in the PNS is similar to ___ in CNS
astrocytes
90
myelinated axons in the PNS are made by
myelinating outer surface of schwaan cells (neurilemma)
91
each myelinated schwaan cells represents
1 internode
92
in unmyelinated axons, schwaan cells surround ___ that lie in __
segments of a group of axons; membrane folds
93
function of membrane folds in unmyelinated schwaan cells
stabalize axons and protect them from chemicals
94
in unmyelinated axons, there are no __ between schwaan cells
nodes
95
axon regeneration in CNS is limited because (3)
1. many more axons are involved
2. astrocytes making scar tissue, block axon growth
3. astrocytes release chemicals that block axon regrowth
96
membrane potential
potential difference across a membrane due to unequal charge distribution
97
inside membrane is slightly __ compared to outside
negative
98
the slightly negative internal charge is due to __-
different permeability of PM to ions and from active transport
99
resting membrane potential (definition)
membrane potential of undisturbed cell; starting point
100
graded potential (definition)
temorary, localized change in resting potential
101
what produces a graded potential?
typical stimulus
102
the graded potential ___ with distance form stimulus
decreases
103
action potential (definition)
electrical event that involves one location on the axon membrane, but the spreads along axon towards terminals
104
action potential is triggered by __
sufficiently large graded potential
105
presynaptic cell releases __-
neurotransmitters
106
neurotransmitters bind to __ on ___ cell membrane, which changes ____ and produces ___
receptors; postsynaptic; permeability; graded potential in post. membrane
107
response of postsynaptic cell depends on ___ and ___
action of stimulated receptors and other stimuli acting at the same time
108
the simplest form of information processing in the nervous system is __-
synaptic activity
109
what are 4 contributors to resting membrane potential?
1. ECF has high [na, cl]
2. cytosol has high [k+, Pr-]
3. na and k are main factors influencing mp
4. proteins and ions cant freely move across membrane
110
the resting membrane potential is a form of ___ energy
potential
111
resting membrane potential in body cells ranges from
-5mV to -100 mV
112
resting membrane potential of a neuron is near
-70mV
113
maintaining the resting membrane potential involves ____ forces and ____ process
passive; active
114
maintance of the resting potential by passive forces is done by __ channels
leak
115
diffusion of Na/K+ ions through leak channels is driven by
chemical and electrical gradients
116
what is the active process in maintaining the resting membrane potential?
Na/K pumps
117
what are leak channels?
passive membrane channels that are always open
118
__, __, and __ determine which ions can diffuse through leak channels
size, shape, structure
119
the pump kicks out __(#) __(ion) and brings in __(#) __ (ion)
3 Na; 2K
120
gated ion channels change the ___ of the plasma membrane in response to stimuli
permeability
121
what are the 3 types of gated ion channels?
1. chemically gated
2. voltage gated
3. mechanically gated
122
chemically gated ion channels are also called
ligand gated ion channels
123
chemically gated ion channels open when
specific chemicals bind to them
124
where are chemically gated ion channels most abundant in the body?
dendrites and cell body of a neuron, where synaptic communication happens
125
voltage gated channels open/close in response to _-
changes in membrane potential
126
voltage gated channels are characteristic of ___ membranes, which generate/spread __
excitable; action potentials
127
what are the 2 gates in a Na voltage gated channel?
1. activation gate
| 2. inactivation gate
128
role of activation gate
opens on stimulation to let sodium in
129
role of inactivation gate
closes to block entry of sodium ions
130
mechanically gated channels open in response to
physical distortion of membrane srface
131
location of mechanically gated channels in body
sensory receptors for stretch, pressure, vibration, sense of touch and hearing
132
where on a neuron are volatge-gates Na/K+ channels found?
along axon
133
where on a neuron are voltage gated ca2+ channels found?
axon terminals
134
what are graded potentials?
changes in membrane potential that cannot spread far from site of stimulation
135
what causes graded potentials?
stimuli that open gated ion channels
136
what is the first step in a graded potential?
membrane exposed to chemical that opens the chemically gated sodium channels, leading to depolarization
137
what happens to Na ions once entered the cell in graded potential?
move away from channels, attracted to negative surface of membrane (local current)
138
degree of depolarization in graded potential ___ with distance from stimuli and __ with size of stimuli
decreases; increases
139
what is the 2nd step in a graded potential?
Na is moved out of cell and repolarization occurs to bring back normal resting potential
140
graded potentials, whether depolarizing or hyperpolarizing, share what 4 characteristics?
1. effect of stimulus decreases with distance
2. effect spreads passively through local currents
3. the change in membrane potential reflects whether + charges enter or exit area
4. stronger stimulus results in more area affected and greater change in membrane potential
141
definition of an action potential
propagated changes in the membrane potential that affect the entire excitable membrane
142
a neuron receives graded potentials at its __
dendrites or cell body
143
action potentials at axon terminals release __
neurotransmitters
144
action potentials allow ____ between cell body and axon terminals
long-range communication
145
resting membrane potential depends on ___ channels
leak
146
graded potentials depend on ___ channels
chemically gated ion
147
action potentials depend on __ channels
voltage gated
148
first step in action potential generation
resting membrane potential: volatge gated NA/K channels closed
149
second step in action potential generation
depolarization to threshold: initial stimulus, sodium channels open and rapid depolarization occurs
150
definition of threshold
membrane potential at which channels open
151
different stimuli that bring membrane to threshold result in ___ action potentials
identical
152
third step in action potential generation
inactivation of Na channels, activation of K channels: K leaves cell and potential shifts back to resting (repolarization)
153
Na channels shift from inactivated to __ as membrane potential returns to near threshold
closed, but capable of opening
154
absolute refractory period
time where membrane cannot respond to more stimulation
155
relative refractory period
time where membrane can respond, but only to a stimulus thats stronger than normal
156
action potentials are generated at __ segment of axon
initial
157
what are the 2 types of propagation?
1. continuous propagation
| 2. saltatory propagation
158
describe movement of action potential by continuous propagation
action potential appears to move step by step through entire axon
159
where does continuous propagation occur?
unmylenated axons
160
describe movement of action potential by saltatory propagation
depolarizes only at nodes, skips internodes
161
why does the AP skip internodes?
ions cant cross membrane where there is myelin
162
is continuous or saltatory propagation faster? why?
saltatory; larger diameter has less resistance to ion movement
163
synapse definition
location where information is transferred from a neuron to another, or to an effector cell
164
what are the 2 types of synapses?
1. chemical
| 2. electrical
165
what is the most abundant type of synapse?
chemical
166
what types of synapses are chemical?
all synapses between neurons and other cell types and most interneuron synapses
167
chemical synapses depend on release of ___
neurotransmitters
168
synapses that release ACh are called
cholinergic synapses
169
1st step at cholinergic synapse
axon terminal depolarized by arriving action potential
170
2nd step at cholinergic synapse
depolarization opens voltage gated Ca channels, ca triggers ACh release into cleft
171
3rd step at cholinergic synapse
Ach binds receptors on chemically gated Na channels, which opens channels for Na to rush in and rapid depolarization
172
4th step at cholinergic synapse
AChe breaks down bound ACh and other Ach diffuse away from binding sites
173
what causes synaptic fatigue
neurotransmitter not keeping up with demand
174
what is synaptic delay?
time lag between arrival of AP at axon terminal and effect on postsynaptic membrane
175
how do electrical synapses work?
changes is membrane potential of one cell produce local currents in adjacent cell, as if sharing common membrane
176
what are the 2 types of postsynaptic potentials?
1. excitatory postsynaptic potential (EPSP)
| 2. inhibitory postsynaptic potential (IPSP)
177
EPSP is graded ___
depolarization
178
EPSP brings membrane potential ___ threshold
closer to
179
in EPSP, the membrane is ___, meaning less stimulus needed to trigger AP
facilitated
180
IPSP is graded __
hyperpolarization
181
IPSP shifts membrane ___ threshold
further from
182
in IPSP, the mebrane is __, meaning larger than normal stimulus required to trigger action potential
inhibited
