Lab 8: Introduction to the Nervous System Flashcards
1
Q
are reflexes inborn or learned
A
can be either
2
Q
describe the difference between sensory neurons and motor neurons
A
- sensory neurons: receptors that detect changes in the environment and send this information to the central nervous system
- motor neurons: send the information from the central nervous system to the effectors that produce a response
3
Q
what is involved in a motor response
A
series of action potentials that produce a muscle contraction
4
Q
define reflexes
A
- response reaction
- can be inborn or learned
5
Q
define learned reflexes
A
result from repetition
6
Q
example of a learned reflex
A
those needed to drive a car where, with practice, the activity is mostly automatic and subconscious
7
Q
define inborn reflexes
A
- rapid, predictable, involuntary, and unlearned motor response to a stimulus
- part of all our neural pathways
8
Q
examples of inborn relfexes
A
- keep us breathing
- maintain posture
- controlling the viscera
- avoiding pain
9
Q
how fast are inborn reflexes to pain
A
can be so rapid that a response in generated before you perceive the pain
10
Q
what are many of the inborn reflexes regulated by
A
the spinal cord and brain stem
11
Q
define myotatic reflex
A
- inborn reflex
- tapping on the tendon under the kneecap produces the knee-jerk reflex
12
Q
what are the 5 parts of all reflex arcs
A
- the receptor that senses the stimulus and initiates the signal
- a sensory neuron that carries afferent nerve impulses to the central nervous system
- an integration center where the signal is processed
- the motor neuron that carries efferent signals to the effector from the integration center
- the effector such as a muscle or a gland which generates a response to the signal
13
Q
define monosynaptic reflex
A
a single synapse between a motor and sensory neuron serves as the integration center
14
Q
define polysynaptic reflex
A
the integration center will include a few synapses and interneurons
15
Q
where is the integration center for most reflexes
A
in the central nervous system
16
Q
define somatic reflex
A
activates skeletal muscle
17
Q
define autonomic reflex
A
controls visceral effectors such as smooth muscle, cardiac muscle, or a gland
18
Q
do spinal reflexes involve higher brain centers for the arc to function
A
no
19
Q
what does distorted, exaggerated, or absent reflexes indicate
A
damage to the nervous system
20
Q
what do stretch and tendon reflexes do
A
help coordinate smooth movements of skeletal muscle groups
21
Q
what do muscle spindles in skeletal muscle do
A
convey information about muscle length or amount of stretch for proper regulation of reflexes
22
Q
what do Golgi tendon organs do
A
convey information about tendon tension for proper regulation of reflexes
23
Q
define propriceptors
A
- receptors that supply information to the central nervous system about the body’s position in space and how much a muscle has or hasn’t moved its insertion
- ex: muscle spindles, Golgi tendon organs
24
Q
how is the myotatic reflex produced
A
single synapses between sensory axons and motor neurons
25
where is the essential circuitry for the myotatic reflex confined to
the spinal cord
26
how many neurons are employed during the myotatic reflex
4
27
describe the process of the myotatic reflex
- striking the patellar ligament stretches the quadriceps muscle
- stimulates sensory muscle spindle receptors
- triggers an impulse in a sensory axon
- sensory axon synapses directly with a motor neuron
- motor neuron conducts the impulse to the quadriceps
- triggers contraction in extrafusal fibers of the stretched muscle
28
where is the cell body of the sensory axon stimulated during the myotatic reflex located
in the dorsal root ganglion in the lumbar region of the spinal cord
29
what does the sensory nerve axon stimulated during the myotatic neurons synapse with
both the motor neuron and an inhibitory interneuron in the spinal cord
30
describe the inhibitory interneuron of the myotatic reflex
- synapses with the sensory neuron to receive information
- synapses with a motor neuron that conducts impulses to the antagonistic muscle (hamstrings)
31
define reciprocal inhibition
- inhibitory interneuron conducts with a motor neuron that conducts impulses in the antagonistic muscle to inhibit contraction
- allows for the contraction of the stretched muscle without impedance form the basal muscle tone of the opposing muscle
32
define ipsilateral
involving motor activity on the same side of the body
33
all stretch reflexes are ______ and ______ in the contracting portion of the pathway
- ipsilateral
- monosynaptic
34
what is one thing that makes the inhibitory portion of the reflex pathway different from the contracting portion of the reflex pathway
- inhibitory portion is polysynaptic
- contracting portion is monosynaptic
35
what is the patellar knee-jerk reflex tested to determine
if motor and sensory connections between the spinal cord and the thigh muscles are functioning
36
what different damage could be indicated by an exaggerated reflex vs an absent reflex
- exaggerated reflex could indicate damage in the brain or spinal cord
- absent reflex would indicate damage of peripheral nerves
37
define stretch reflex
stimulates muscle contraction when muscle length is increased or the muscle is stretched
38
define tendon reflex
- polysynaptic
- causes muscles to relax in circumstances of high tendon tension
39
what happens to the timing of more complex reflexes
- longer delay between stimulus reception and the more complex response
- requires additional cells
40
how many neurons are in the "direct light" or pupillary reflex and what do they connect
- 4 neurons
- connect the retina to the midbrain and then convey information back to the pupillary sphincter muscles
41
define consensual light reflex
as the pupillary sphincter of one eye constricts due to increased light, the pupillary sphincter on the other eye will also constrict
42
define miosis
- pupillary constriction
- from Greek meiosis = diminution
43
define mydriasis
pupillary dilation
44
how are superficial reflexes stimulated
gentle stroking of the skin in specific location
45
what are superficial reflexes used to test
spinal-cord level reflex arcs and upper motor pathways
46
how is the plantar reflex elicited
running a blunt object down the lateral aspect of the sole of the foot
47
what happens as a response to the plantar reflex
the toes should flex
48
what does the plantar reflex indiretly indicate
the functionality of the corticospinal tracts
49
what does the plantar reflex directly indicate
spinal cord integrity from L4 to S2
50
describe Babinski's sign
- abnormal reflex displayed when the corticospinal tract or primary motor cortex is impaired
- the great toe dorsiflexes and the other toes laterally fan out
51
what abnormal reflex do infants display
Babinski's sign
52
why do infants display Babinski's sign until they are 1 year old
the nervous system is not yet completely myelinated
53
how are the abdominal reflexes elicited
by stroking the lateral skin of the abdomen on any side of the umbilicus
54
describe the effects of the abdominal reflexes
produces an abdomen contraction which moves the umbilicus into the direction of the stimulus
55
what does testing the abdominal reflexes indicate
spinal cord integrity from T8 to T12
56
what does an absence of abdominal reflexes indicate
corticospinal tract lesion
57
which are more complicated: voluntary reactions to a cue OR reflexes
voluntary reactions to a cue
58
what do voluntary reactions to a cue require in contrast to reflexes
voluntary reactions require brain functions rather than relying exclusively on neuronal circuitry of the spinal cord in the case of relfexes
59
define simple reaction time
only one stimulus and one corresponding response
60
where does the major in reaction time occur
at the synapses between the different neurons involved
61
what is the mean reaction time for college-aged individuals for light (photonic) stimuli
190 ms
62
what is the mean reaction time for college-aged individuals for sound stimuli
150 ms
63
what is the mean reaction time for college-aged individuals for touch stimuli
155 ms
64
how long does it take an auditory stimulus to reach the brain
8-10 ms
65
how long does it take a visual stimulus to reach the brain
20-40 ms
66
list factors that may affect an individual's reaction time
- age
- arousal
- distraction
- gender
- practice
- errors
- fatigue
- drugs
- warnings
67
what is the effect (positive or negative) of age on reaction time
can be either positive or negative
68
what is the effect (positive or negative) of arousal on reaction time
can be either positive or negative
69
what is the effect (positive or negative) of distraction on reaction time
positive
70
what is the effect (positive or negative) of gender on reaction time
can be either positive or negative
71
what is the effect (positive or negative) of practice on reaction time
negative
72
what is the effect (positive or negative) of errors on reaction time
positive
73
what is the effect (positive or negative) of fatigue on reaction time
positive
74
what is the effect (positive or negative) of drugs on reaction time
can be either positive or negative
75
what is the effect (positive or negative) of warnings on reaction time
negative
76
describe how age effects reaction time
- reaction time shortens from infancy to 20s
- reaction time increases slowly from 20s to 50/60s
- reaction time lengthens faster as a person gets into their 70s and beyond
77
describe how arousal effects reaction time
- reaction time is fastest with an intermediate level or arousal
- reaction time deteriorates when the subject is either too relaxed or too tense
78
describe how distraction effects reaction time
distractions increase reaction time significantly, especially in younger individuals
79
describe how practice effects reaction time
practice at a task decreases reaction time
80
describe how errors effect reaction time
when a volunteer makes an error, subsequent reaction times are slower due to the subject being more cautious
81
describe how fatigue effects reaction time
- reaction time due to fatigue deteriorates more in complicated tasks than simple tasks
- mental fatigue, especially sleepiness, has the greatest effect
82
describe how drugs effect reaction time
- stimulants tend to decrease reaction times to a point (too much will increase)
- depressants increase reaction times
83
describe how warnings effect reaction time
reaction times are faster when the subject has been warned that a stimulus will arrive soon
84
what are the two groups of nerves in the peripheral nervous system
- cranial nerves
- spinal nerves
85
how are nerves in the peripheral nervous system categorized into either cranial or spinal nerves
based on the part of the CNS with which they communicate
86
how are nerves classified
- sensory
- motor
- sensory and motor
87
describe why motor neurons also have a small sensory somponents
due to proprioception (the sense of self-movement, force, and body position)
88
define epineurium
outer covering of a whole nerve
89
define perineurium
- beneath epineurium
- separates axons into bundles called fascicles
90
define endoneurium
- beneath perineurium
- surrounds each axon inside a fascicle to separate it from neighboring axons
91
what is the myelin sheath composed of in axons in nerves of the PNS
schwann cells
92
what are the two types of cells in the nervous system
- neurons
- glial cells
93
what is the overall function of glial cells
- supportive role in protecting and maintaining nerve tissue
- protect, support, and anchor neurons in place
94
define neuron
- communication cells of the nervous system
- capable of propagating and transmitting electrical impulses
95
define neuroglia
network composed of glial cells
96
what is the function of glial cells in the CNS
production and circulation of cerebrospinal fluid that circulates in the ventricles in the brain and in the central canal of the spinal cord
97
what is the function of glial cells in both the CNS and PNS
isolate and support neurons with myelin to increase conduction velocity
98
what are the four types of glial cells in the CNS
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
99
what are the two types of glial cells in the PNS
- satellite cells
- shwann cells
100
what are the most abundant and versatile glial cells
astrocytes
101
function of astrocytes
- making exchanges between capillaries and neurons
- helping to determine capillary permeability
- guiding the migration of young neurons
- synapse formation
102
what part of an astrocyte is in contact with blood vessels and the neuronal surfaces
perivascular feet
103
describe the structure of microglia
- small
- oval-shaped
- relatively long "thorny" processes
104
function of microglia
- thorny processes touch nearby neurons to monitor their health
- if they sense that certain neurons are injured, they migrate towards them
105
where are ependymal cells located
- CNS
- lining the central cavities of the brain and the spinal cord
106
function of ependymal cells
cilia help to circulate cerebrospinal fluid that cushions the brain and spinal cord
107
function of oligodendrocytes
-wrap around thicker neuron fibers in the CNS to produce insulating myelin sheaths
108
where are satellite cells found
- in the PNS
- surrounding neuron cell bodies
109
function of satellite cells
- thought to have many of the same functions in the PNS as astrocytes in the CNS
- exchanges between capillaries, guiding young neurons, synapse formation
110
function of schwann cells
- surround and form myelin sheaths around larger nerve fibers in the PNS
- vital to regeneration of damaged peripheral nerve fibers
- increase speed of transmission or nerve impulses
111
what are the most abundant cell type in the nervous system
glial cells
112
what are the 3 main parts of neurons
- dendrites
- cell body (soma)
- axon
113
define dendrites
- main receptors or input regions of neurons
- provide enormous surface area for receiving signals from other neurons
114
where do dendrites convey messages to
towards the cell body (soma)
115
what signals are the messages conveyed by dendrites to the cell body
- NOT action potentials
- graded potentials
116
define cell body (soma)
part of neuron that surrounds the nucleus and contains organelles
117
define Nissl bodies
rough endoplasmic reticulum granules in the cell body of neurons that stains darkly in histological sections
118
where are most neuron somas located
in the CNS
119
what are clusters of somas in the CNS termed
nuclei
120
what are clusters of somas in the PNS termed
ganglia
121
how many axons are in a single neuron
one
122
where do axons convey messages to
from the cell body to other neurons
123
define the initial segment of the axon
the first part of the axon of a neuron that extends from the axon hillock
124
define axon hillock
area of the neuron where the cell body and axon connect
125
define collateral branches of the axon
initial divisions of the axon
126
define telodendria
further divisions of the collateral branches of the axon
127
define synaptic terminal
- distal tip of each telodendrion
- has synaptic vesicles containing neurotransmitters
128
which nerve fibers are usually protected by a myelin sheath
usually those that are long or large in diameter
129
what does the myelin in the myelin sheath do
- protects and electrically insulates fibers
- increases to speed of transmission of nerve impulses
130
are dendrites ever myelinated
no
131
define multipolar neurons
neurons with more than two dendrites
132
what percent of neurons in the nervous system are multipolar
99%
133
when do chemically (ligand)-gated ion channels open
when the appropriate neurotransmitter binds to the receptor, allowing simultaneous movement of Na and K
134
when do voltage-gated ion channels open
in response to changes in membrane voltage
135
define membrane ion channels
- large proteins
- selectively allow certain ions to pass through the membrane
136
define gated channel proteins
have a "gate" that opens and closes in order to allow an ion to pass
137
when do mechanically gated channels open
open in response to physical deformation of the receptor
138
describe ion movement chemically
move from an area of higher concentration to an area of lower concentration
139
describe ion movement electriaclly
move toward an area of opposite electrical charge
140
describe the voltage decay in a bare plasma membrane of an axon
voltage decays because current leak across the membrane
141
describe the voltage decay in an unmyelinated axon
- voltage-gated Na and K channels regenerate action potential at each point along teh axon so voltage does not decay
- conduction is slow because movements of ions and gates of channel protein takes time and must occur before voltage regeneration occurs
142
describe voltage decay in a myelinated axon
- myelin keeps current in axons and voltage does not decay much
- action potentials are generated only in teh nodes of Ranvier and appear to jump rapidly from node to node
