Neuro PPT 2 Flashcards
1
Q
What serves as the integrative area for cord reflexes?
A
Cord Grey matter
2
Q
Where do sensory signals enter the spinal cord?
A
Sensory roots (Posterior or dorsal roots)
3
Q
Sensory signals have Two destinations in the spinal cord. What are they?
A
Local segmental reflexes - this branch terminates in the gray matter for local reflexes
Higher system transmission: this branch sends signals to higher nervous system levels (brain stem, cortex)
4
Q
What are anterior motor neurons?
A
Large neurons located in the anterior horns and directly innervate muscles. Transmit impulses quickly.
Three types:
alpha motor neurons
Gamma motor neurons
Renshaw cells
5
Q
What are interneurons
A
Found in the gray matter, highly excitable and integral to reflex arcs
6
Q
Alpha motor neurons give rise to ________ motor nerve fibers
A
A alpha
7
Q
What do alpha motor neurons do?
A
Stimulates multiple skeletal muscle fibers (ie: motor unit)
8
Q
What do gamma motor neurons innervate?
A
Intrafusal fibers
9
Q
Gamma motor neurons are _______ fibers
A
Small
10
Q
Gamma motor neurons give rise to ______ motor nerve fibers
A
A gamma
11
Q
Stimulation of the intrafusal fibers by gamma motor neurons helps control _______ ________ _______
A
Basic muscle tone
12
Q
Where are interneurons located?
A
Widely distributed throughout the cord gray matter
ie: dorsal horns, intermediate areas, anterior horns
13
Q
Function of interneurons
A
Process and relay signals
Extensive Interconnections responsible for spinal integrative functions: diverging, converging, repetitive-discharge
14
Q
Location of renshaw cells
A
Anterior horn of the gray matter
Closely associated with anterior motor neurons
15
Q
Function of renshaw cells
A
Refines motor control by transmitting INHIBITORY signals from the anterior motor neuron to adjacent motor neurons
Causes lateral inhibition
16
Q
Function of propriospinal fibers
A
Form communications between spinal cord segments to coordinate multi-segmental reflexes, allowing coordination of movement between extremities.
17
Q
Two types of muscle sensory receptors
A
Muscle spindles and golgi tendon organs
18
Q
Function of muscle sensory receptors
A
Provide continuous feedback of sensory information about muscle length and tendon tension
19
Q
Muscle spindles
State location and function
A
Location: muscle belly
Function: senses muscle length and rate of change of length
20
Q
Golgi Tendon Organs
State location and function
A
Location: tendons
Function: senses tendon tension and rate of change of tension
21
Q
Feedback from the muscle sensory receptors is sent to which 3 areas?
A
Spinal cord
Brain stem
Motor areas of cerebral cortex
22
Q
Muscle spindles consist of …
A
3-12 intrafusal fibers that taper at the ends to connect to larger extrafusal muscle fibers
23
Q
T/F: Continuous transmission of nerve signals is
required for function of the cerebral cortex
A
True
24
Q
How much time does direct stimulation effects persist for?
A
Milliseconds or seconds
25
How much time does neurohormonal systems effects persist for?
Minutes or hours
26
Location for the reticular excitatory area:
Pons/mesencephalon
27
Where are facilitatory signals transmitted to?
Spinal cord and cerebral cortex
28
Location of the reticular inhibitory areas:
Medulla
29
_________ releasing nerve fibers from locus ceruleus transmit signals
throughout brain
Primarily excitatory effects, possibly involved in dreaming
Norepinephrine
30
____________ nerve fibers from raphe nuclei (i.e., medulla and pons) transmit
signals to spinal cord, diencephalon, and cerebral cortex
At spinal cord level, it is involved in pain suppression
At diencephalon and cerebral cortex level, it has inhibitory effects,
possibly involved in regulation of sleep
Serotonin
30
_________ nerve fibers from substantia nigra transmit signals to caudate
nucleus, putamen, hypothalamus, and limbic system
Primarily inhibitory effects, possibly some excitatory effects
Dopamine
31
__________ nerve fibers from gigantocellular neurons of reticular excitatory area
transmit signals to spinal cord and higher brain levels
Primarily excitatory effects, possibly involved in wakefulness
Acetylcholine (Cholinergic)
32
What system:
Controls emotional behavior and motivational drive
Reward/Punishment (i.e., pleasant/unpleasant)
Vegetative functions (e.g., control of body temperature,
control of osmolality of body fluids, hunger, thirst)
Limbic System
33
Anatomy of the Limbic System:
SUBCORTICAL STRUCTURES
Hypothalamus- central physiologic function
Septum area, paraolfactory area, anterior nucleus of
thalamus, portions of basal ganglia, hippocampus,
amygdala
LIMBIC CORTEX
Orbitofrontal cortex, subcallosal gyrus,
cingulate gyrus, parahippocampal gyrus
Medial forebrain bundle extends from orbitofrontal
cortex through hypothalamus to brain stem reticular
formation
34
Two-way communication exists between hypothalamus and all levels of limbic system:
1. Transmits signals to brain stem then to
peripheral nerves of ANS
2. Transmits signals to anterior thalamus and other
structures of limbic system
3. Transmits signals to hypothalamic infundibulum to
control secretion from pituitary gland
35
What are the seven functions of the hypothalamus?
1. cardiovascular regulation
2. body temperature regulation
3. body water regulation 4. regulation of uterine contraction and milk
ejection
5. gastrointestinal regulation
6. circadian rhythm
7. pituitary
gland regulation
36
Sensory experiences cause activation of
___________, which sends signals to
anterior thalamus, hypothalamus, and other
structures of limbic system
Hippocampus
37
What are the two functions of the hippocampus?
1. Formation of memories
2. Consolidation of memories
38
Anatomy of the amygdala:
Group of nuclei situated inferiorly to medial
anterior pole of temporal lobe
Two-way communication with cerebral
cortex, hippocampus, septum, thalamus,
and, in particular, the hypothalamus
39
What are the functions of the amygdala?
(Stimulation causes same effects as direct stimulation of the hypothalamus
1. tonic and clonic movements
2. circling
movements
3. movements associated
with olfaction and eating (licking,
chewing, swallowing)
4. Reward/Punishment patterns
5. Activities of reproductive organs
40
Portion of cerebral cortex that
belongs to limbic system, functioning as
transitional zone and functions as the association area for behavioral
control
Limbic Cortex
41
Unconsciousness from which a person
can be aroused by sensory or other stimuli
Sleep
42
25% of sleep,
period of high brain activity during which
dreams occurs
How long does it occur and last?
REM (Rapid Eye Movement)
Occurs every 90 minutes, lasts 5-30 minutes
42
Restful sleep that often occurs during the early stages of sleep:
When does it occur?
NREM (Non-REM)
Occurs during first hour of sleep
43
Unconsciousness from which a
person cannot be aroused
Coma
44
What are six things that occur during REM sleep:
1.Dreams likely to occur
2.Difficulty arousing
3.Depressed muscle tone and irregular
muscle movements
4.Irregular heart rate and respiratory rate
5.Increased brain metabolism (i.e., 20%)
6.EEG demonstrates patterns similar to
wakefulness (i.e., paradoxical sleep)
45
What are three things that occur during NREM Sleep
1.Dreams may occur
2.Decreased BP, RR, and basal metabolic rate
3.EEG demonstrates slow, high-amplitude
waves
46
Theories of Sleep Mechanisms: Early Theory vs. Current Theory
Early Theory: Sleep is the result of
inactivation of the reticular activating
system due to progressive fatigue throughout
the day
vs.
Current Theory: Sleep is the result of active
inhibition of higher brain areas by an area
caudal to the mid-pons
47
What are the three transmitter substances of sleep?
1. Serotonin: Secreted by nerve endings of fibers from the raphe
nuclei, blockade of serotonin production leads to prolonged
wakefulness
2. Muramyl peptide: Low-molecular-weight peptide that
accumulates in CSF during prolonged periods of wakefulness
3. Delta sleep-inducing peptide: Nonapeptide present in CSF after
electrical stimulation of thalamus
48
Spontaneous activity of
reticular activating nuclei excites cerebral
cortex and peripheral nervous system, which
send excitatory signals to reticular activating
nuclei in a positive feedback loop
Wakefulness
49
(Sleep-Wake Cycle) What substance is produced by hypothalamic
neurons that provide excitatory input to
other areas of the brain
Orexin
50
Fatigue of neurons in the reticular
activating nuclei disrupts positive feedback
loop, allowing centers to actively
inhibit the cerebral cortex
Sleep
51
What are the six physiological functions of sleep?
(Divided into nervous system and other functional systems)
Nervous System
1. Cognition
2. Neural maturation
3. Facilitation of learning and memory
4. Targeted erasure of synapses (i.e.,
“forgetting”)
Other Functional Systems:
5. Conservation of metabolic energy
6. Clearance of metabolic waste
products
52
Electrical recordings from surface of
brain or scalp that reflect level of
excitation throughout the brain
Brain waves
Vary markedly between
wakefulness, sleep, and coma
53
2 different nuclear structures of muscle spindles
Nuclear bag - multiple muscle fiber nuclei congregate in bags, which excites only primary afferent endings
Nuclear chain - multiple muscle fiber nuclei are aligned in a chain, which excites BOTH primary AND secondary afferent endings
54
What are ranges of intensity and frequency of brain waves?
Intensity: 0-200 µV
Frequency: <1 – >50
55
Explain the difference between synchronous and nonsynchronous brain waves
Synchronous: Concurrent firing of
neurons in synchrony with each other will
produce waves with higher voltage
Nonsynchronous: Concurrent firing of
neurons in opposite directions results in
opposing polarities and produces waves
with lower voltage
56
What are the four types of brain waves?
1. Alpha
2. Beta
3. Theta
4. Delta
57
What brain wave is present during
focused mental
activity, found in
frontal and parietal
areas?
What is the frequency of this type of wave?
Beta Waves
>14 Hz
58
What brain wave appears
during quiet
wakefulness,
primarily in the
occipital lobe?
What is the frquency and intensity?
Alpha Waves
8-13 Hz
~50 µV
59
What brain wave is common in
children, linked to
emotional stress and
degenerative brain
states in adults?
What is the frequency?
Theta Waves
4-7 Hz
60
What brain wave occurs in deep sleep, often
high amplitude?
What is the frequency?
Delta Waves
<3.5 Hz
61
Two types of waves are involved in wakefulness:
Occurs during increased mental activty: _________
Occurs during decreased mental activity: ________
Increased mental activity: beta waves
Decreased mental activity: alpha waves
62
Name the stages of NREM sleep and name the brain wave associated with the stage:
Stage 1: low-voltage with
intermittent ‘sleep
spindles’
Stage 2-3: theta waves
Stage 4: delta waves
63
What brain waves occur during REM sleep?
Beta waves
64
Muscle spindles with nuclei in “bags” excites which afferent endings?
Primary only
65
Muscle spindles with nuclei in chains excite which afferent nerve endings?
Primary and secondary
66
Primary afferent nerve endings are type _______ fibers that _________ the central portion of the muscle spindle
Ia
Encircles
67
Secondary afferent endings are type ______ fibers that innervate areas ________ to primary afferent nerve endings
II
Lateral
68
What type of motor nerve fibers innervate the ends of intramural fibers to control muscle tone?
Gamma motor nerve fibers
69
What characterizes the dynamic responses of muscle spindles?
It is a rapid, short-lived response to changes in muscle LENGTH
Via primary afferent endings
70
What characterizes the static response of muscle spindles?
Slow stretching of muscle spindles via primary AND secondary afferent endings for several minutes
71
The static response of muscle spindles ensures smooth muscle movement over prolonged periods of stretch
True or false
True
72
The dynamic response involves both primary and secondary afferent endings? true or false?
False
Only primary
73
Define muscle stretch reflex
Excitation of muscle spindle causes reflex contraction of extrafusal skeletal muscle fibers, ensures smooth movement of muscles and prevents jerky movements
74
Muscle stretch reflex is a _________ pathway formed between type ____ fiber from muscle sprinkles and anterior motor neuron which minimizes time delay for reflex action to occur
Monosynaptic
Ia
75
Describe dynamic stretch reflex
Type Ia fibers rapidly but briefly transmit signals to oppose changes in muscle length
76
Describe static stretch reflex
Type Ia and II fibers transmit signals to maintain constant degree of muscle contraction
77
Describe Golgi tendon organ
Encapsulated sensory receptor that surrounds muscle tendon fibers
78
Sensory and motor innervation of golgi tendon organ
Sensory: type Ib sensory afferent nerve fibers —> inhibitory interneurons —> anterior motor neurons —> prevents activation of anterior motor neurons
79
The dynamic response of the Golgi tendon organ has intense reaction to ___________ _________ in tension
Sudden increases
80
Static response of the Golgi tendon organ is a ______-______ firing that is proportional to to muscle tension
Steady-state
81
What is the function of the Golgi tendon reflex
inhibitory reflex that prevents excessive muscle tension
Ex: someone throws a 50pound weight at you
82
Type _____ fibers from Golgi tendon organ synapse with inhibitory ________ in dorsal horn which synapses with anterior motor neuron
Ib
Interneuron
83
Explain the flexor reflex pathway and function
Sensory afferent nerve fibers transmit stimuli (nociceptive) to the interneuron pool in the dorsal horn which synapses with anterior motor neurons
Flexor muscles contract in response to sensory stimulus to coordinate flexión and abduction of the limb (withdrawal of the limb)
84
Explain the 3 interneuron pools of the flexor reflex:
Diverging circuits
Reciprocal inhibition
Afterdischarge
Diverging: activate complimentary muscles
Reciprocal inhibition: inhibits antagonistic muscles
Afterdischarge: extends duration of reflex response
85
Describe the pathway and function of the crossed extensor reflex
Sensory afferent nerve fibers transmits stimuli to the interneuron pool which synapses with anterior motor neuron on the contra lateral side of the spinal cord
Function: extensor muscles on the contra lateral side contract in response to sensory stimulus to coordinate muscle extension to maintain balance
86
Describe the interneuron pool of crossed extensor reflex:
Afterdischarge
Extends duration of the reflex response
87
Explain reciprocal inhibition and innervation
Reflex excitation of one muscle results in simultaneous inhibition of antagonistic muscles, ensures smoothness and efficient movements
Ex: flexor reflex and crossed extensor reflex
88
3 reflexes of posture
Positive supportive reaction
Magnet reaction
Cord righting reflex
89
Explain positive supportive reaction
Pressure on the footpad causes extension of the limb
90
Explain the Magnet reaction
Pressure on one side of the footpad causes extension in that direction, preventing the animal from falling to that side
91
Explain the cord righting reflex
Spinal animals laid on their side produce uncoordinated movements in attempt to raise the animal to standing position
92
List 4 reflexes of locomotion
Stepping movements
Stumble reflex
Reciprocal stepping
Mark time reflex
93
explain stepping movements reflex
Oscillation between reciprocal inhibition circuits controlling agonist and antagonistic movements cause rhythmical stepping of the limbs
94
Explain the stumble reflex
Obstruction on top of foot will cause foot to stop, lift higher, and proceed forward
95
Explain reciprocal stepping reflex
Forward movement of one limb causes backward movement of the opposite limb
96
Explain mark time reflex
Diagonal stepping between all limbs occurs when animal is suspended and limbs dangle
ex: holding doggy over pool
97
Explain scratch reflex
Initiated by itch/tickle —> position sense locates the point of irritation —> produces to-and-fro scratching (oscillatory movement)
98
Muscle spasms result from _______ impulses
Pain
99
mass reflex —> Strong pain or organ distensión produces sudden and profound activation of spinal cord
What 4 effects?
Flexor muscle spasm
Bladder/bowel evacuation
Increased arterial pressure
Profuse sweating
100
3 possible causes for muscle cramping
Local irritation/metabolic abnormalities (severe cold, over exercise)
Broken bones - sharp edges produce pain —? Muscle spasm
Peritonitis —> abdominal muscle contraction
