313 FINAL 1 Flashcards
1
Q
Afferents =
A
AP going into the NS
2
Q
Motor neurons exit from the _ horn via _ root - these are efferent axons. _ root carries _ or _ axons.
A
Motor neurons exit from the anterior horn via ventral root - these are efferent axons. Dorsal root carries sensory or afferent axons.
3
Q
Afferent neuron always comes in thru _ root. Send axons out thru _ root.
A
Afferent neuron always comes in thru dorsal root. Send axons out thru ventral root.
4
Q
Motor neuron pool =
A
all the motor neurons innervating a particular muscle
5
Q
motor unit =
A
the cell body and dendrites of a motor neuron, the multiple branches of its axon, and the muscle fibers that it innervates.
6
Q
Muscle unit =
A
all the muscle fibers belonging to a motor unit
7
Q
Innervation ratio =
A
the number of muscle fibers innervated by a single motor neuron
8
Q
Innervation ratio changes with aging =
A
of MUs declines, but size increases (# of fibers per unit increases).
9
Q
3 types of skeletal muscle fiber:
A
- slow oxidative (SO), 2. Fast oxidative-glycolytic (FOG), 3. Fast glycolytic (FG)
10
Q
Distribution of muscle fibers of a motor unit
A
S motorneurons innervate SO type muscle fibers forming S type motor units. FR motorneurons innervate FOG type muscle fibers forming FR type motor units. FF type motorneurons innervate FG muscle fibers forming FF type motor units.
11
Q
Large motorneurons supply primarily _-twitch muscle fibers, small to _-twitch
A
Large motorneurons supply primarily fast-twitch muscle fibers, small to slow-twitch
12
Q
small motor neurons have _ input resistance
A
high
13
Q
rheobase=
is it low in _ motorneurons.
A
direct measure of the current that has to be put into a neuron to get it to fire
low in small motorneurons.
14
Q
Afterhyperpolarization is _ in large MNs
A
Shorter
15
Q
Twitch =
A
A twitch is the physiological, quantal response of a MN to stimulation
and
sarcomere shortening and lengthening.
16
Q
Large motorneurons (large dendritic trees) have (low/high) resistance. Higher resistance → (faster or slower) to fire
A
Large motorneurons (large dendritic trees) have low resistance. Higher resistance → slower to fire.
17
Q
Motor neuron types and characteristics
A
- Slow contracting, fatigue resistant (type S) small, slow, less innervation ratio.
- Fast contracting, fatigue resistant (type FR) get to peak force much sooner, and half relax sooner but peak is not that much bigger than slow oxidative.
- Fast contracting, fast to fatigue (type FF) big cross section of muscle. Quick rise to peak for, quick decline to half, peak force is gigantic. Bad blood supply, glycogen gets used up.
18
Q
what happens if you re-attach a slow MN to fast muscle fibers?
A
it will change behavior - however the changes are not dramatic, and you dont see a complete transition in behavior, just a minor one
19
Q
methods for recording single motor units
A
fine wires and metal micro electrodes
20
Q
proprioceptors receive info about
A
relative position of limbs in space
21
Q
henneman size principle
A
smaller MUs w/ smaller MNs are recruited first and get off last
22
Q
MU recruitment continues until about _ of max
A
85%
23
Q
Ia afferents are sensitive to the __/__ and ___ of the muscle stretch
A
velocity/speed and length
24
Q
II afferents are sensitive to the __ of change
A
length
25
bag and chain fibers =
1. defined based on distribution of the nuclei
2. bag fibers are longer than chain, and divided into bag1 and bag2
2. usually 2-3 bag and 3+ chain per spindle
26
orderly recruitment - why? pro and con
increments of increased work have an effect on net force
pro: brain doesnt have to contend with 445 switches, just control of the level of input to motor pool
con: inability to selectively activate MUs out of order
27
conduction velocity of afferents depends on...
diameter - larger = faster
28
synaptic potential =
how a presynaptic neuron influences a postsynaptic neurons susceptibiity to generate an AP
29
bag and chain fibers are _____ fibers
intrafusal
30
MN pool is in the ___, MU is in the _____
spinal cord, muscle
31
types of sensory afferent innervation:
1. primary/Ia afferents: spiral around the central area of bag1, bag2 and all chain fibers
2. secondary/II afferents: innervate bag2 and chain fibers, never bag1 afferents
32
performance of a particular movement is always accomplished by...
the activation of MUs in orderly recruitment, increasing force by adding more units
33
efferent axons exit from the ___ horn via the ___ root
anterior horn, ventral root
34
2 ways to control muscle force
more MUs or firing more frequently
35
type S motor units:
small, slow contracting, fatigue resistance, small innervation ratio
36
FF motoneurons innervate __ type fibers, forming __ type MUs
FG, FF
37
afferents are labeled based on
cross sectional diameter
38
each motor unit produces a ___ _____ _____
partially fused tetanus
39
partially fused tetanus =
when the muscle fibers do not completely relax before the next stimulus because they are being stimulated at a fast rate; however there is a partial relaxation of the muscle fibers between the twitches.
40
units fire ____ with each other, causing a smooth net force
asynchronously
41
FR motoneurons innervate __ type fibers, forming __ type MUs
FOG, FR
42
interoceptors =
transduce info from within the body (pain temp gut bladder)
43
receptor behavior - rapid vs slow adapting: what do they provide?
rapidly adapting: provides dynamic info about stimulus - info about to change
slowly adapting: provides stating inco about stimulus - info about persistence. can also code fro rate of application of probe
44
compartment =
unique population of MUs being confined to a certain region of the muscle - several groups of MN being controlled at the same time,
45
types of PSP -
excitatory and inhibitory
46
interplay between types of PSPs determines...
if the neuron will fire an AP
47
EPSP characteristics
1. local and graded (not all or none) - magnitude of EPSP determines amount of neurotransmitter released
2. can summate - not followed by refractory period
48
proximal muscles and distal muscles have a ___ and ___ density of muscle spindles, respectively
lower and higher
49
derecruitment =
sequential inactivation
50
FR type motor unit characteristics
fast contracting, fatigure resistant, reach peak force sooner (not bigger peak than SO by much)
51
type I afferent categories
Ia and Ib
52
FF type MU characteristics
fast contracting, fast to fatigue, quick rise to peak, quick decline to half, large peak force. bad blood supply, glycogen gets used up
53
divergence vs convergence
divergence = a single neuron synapses on multiple neurons
convergence = multiple neurons converge on fewer neurons
54
the _ root carries sensory/afferent axons
dorsal root
55
central receptors project to __ structures
superior
56
cell bodies are located in the ___ ___ ___
dorsal root ganglion
57
why arent APs fired from spatial summation?
- two excitatory potentials diminished by summation with an inhibitory potential
- summed potentials are below threshold
- enough negativity at the same time to prevent AP
58
muscle spindle =
1 cm, middle region covered by a connective tissue capsule, polar regions have myofilament contractile components
59
receptors in the ___ project ___ to the SC
periphery, centrally
60
the bulk of connections of neurons are _____
interneurons
61
characteristics of muscle spindle receptors
found in most skeletal muscle
lie ine parallel w large force producing muscle (extrafusal)
62
density =
number of muscle spindles
63
spatial summation steps
1. 3 excitatory neurons fire. their graded potentials are all below threshold. each cause a small dimple but not enough to shift membrane
2. graded potentials arrive at trigger zone together and create a suprathreshold signal
3. AP is generated
64
spatial vs temporal summation
spatial = EPs from many diff presynaptic neurons cause post synap neuron to fire
temporal = a single pre synaptic neuron fires many times in succession, causing neuron to fire
65
Ix afferents go to __
Ia primary endings go to __ ___
Ib afferents go to ___
muscle
specific receptors
diff muscle parts (eg GTO)
66
the motor unit =
cell body and dendrites of a MN + multiple branches of axon + the muscle fibers it innervates
67
receptors can be stimulated by __or ___ stimuli
mechanical or chemical
68
exteroreceptors =
transduce info from environment, such as cones and rods in retina picking up light
69
rheobase =
current that has to be put into a neuron to get it to fire - low in small MNs, also slow conduction velocity
70
the afterhyperpolarization is ___ in large MNs
shorter
71
fused tetanus =
when there is no relaxation of the muscle fibers between stimuli and it occurs during a high rate of stimulation. when tetanized, the contracting tension in the muscle remains constant in a steady state
72
the force that muscle exerts during contraction depends on 2 things:
the number of MNs that are activated and the rates at which they discharge APs
73
conduction velocity =
the speed at which APs are propagates along the axon, which varies w axon diameter
74
further increase in force is accomplished by ____ _____ of activated MUs
discharge rate
75
absolute force is greater for __ twitch MUs
fast
76
double discharge =
adding an extra impulse --> force production goes up and stays there, even tho its still firing at the same rate. if it misses an impulse, force production goes down and stays there
77
synchrony =
two MUs firing togheter --> ev avoiding failing last rep by lowering weight in. achoppy movmeney
78
muscle spindle receptors run ___ to main muscle fibers (called ___ ____)
parallel, extrafusal fibers
79
the spindle consists of:
several differentiated muscle fibers (intrafusal fibers) enclosed in a spindle shaped connective tissue sac
80
the ends of the intrafusal fibers are ___, but the central portion is non-____ and innervated by ___ ___
contractive, non contractile, gamma MNs
81
two types of intrafusal fibers:
bag and chain
82
bag fiber characteristics
- where are the nuclei
- what do they innervate
- what do they measure
dynamic, 1 per spindle, has many nuclei concentrated in bags, cause excitation of primary sensory fibers
2 types: Bag 1- smaller, bag2 - largest, swell to enclose nuclei, no striations
they sense dynamic length of the muscle, sensitive to length and velocity
83
chain fiber characteristics
- where are the nuclei
- what do they innervate
- what do they measure
static, nuclei are arranged in a chain, excite the secondary nerve which measures stress and strain placed. onthe muscle, innervated by sensory afferents and motor efferents
84
afferent innervation - happens via which fibers, and where do they project to
via type Ia and type II sensory fibers - these project to the dorsal horn
85
efferent innervation - happens via which neurons, what happens
via static gamma MNs. stimulation causes the nuclear chain to shorten along with the extrafusal fibers. shortening allows chain fibers to be sensitive to changes in length while its corresponding muscle is concentrated
86
which afferents are primary and secondary endings
primary = groups Ia afferents
secondary = type II afferents
87
gamma motor neuron afferents innervate...
contractile regions
88
AP firing rate increases as..
extrafusal fibers are lengthenes
89
when contracting, type Ia afferents...
how to overcome the effect
go limp and cant notice further contractions
overcome by alpha-gamma coactivation. intrafusal fibers keep ends taut to they. arestill sensitive
90
alpha gamma coactivation =
when the CNS instructs a muscle to contract, it not only sends the appropriate signals to the alpha motor neurons, it also instructs gamma motor neurons to contract the intrafusal fibers appropriately;
91
dynamic gamma motor neurons respond to _____ and _______
respond to dynamic stretch, innervate bag1 fibers
92
static gamma motor neurons respond to _____ and _______
respond to steady state length, innervate bag2 + chain mix
93
_____ ____ keep the spindles taut
gamma MNs
94
___ ___ innervate extrafusal fuvers and are responsible for initiating contraction
alpha motor neurons
95
Many Ia afferents branch in order to...
connect a number of different muscle spindles
96
mechanoreceptors =
somatosensory receptors that relay extracellular stimulus to intracellular transduction through mechanically gates ion channels, usually in the form of touch/pressure/stretching
97
graded potential =
movement of ions and a membrane potential change
98
Ia's are sensitive to...
II's are sensitive to...
speed
length change
99
what does turning on the gamma system do?
prevents the spindle from becoming unloaded during shortening contractions, keeping it sensitive to stretch,
100
spindles sensitive to velocity are ____, and more sensitive to length are ____
dynamic, static
101
fusimotor activity is...
scaled to the task at hand to make. the spindle more sensitive when needed
102
rapidly adapting receptor behavior provides...
dynamic info about stimulus = info about change. if there is a bigger push, there will be a higher frequency but it never stops/adapts
103
slowly adapting receptor behavior provides...
static info about the stimulus = info about persistence. it will eventually adapt/stop firing
104
dynamic index =
it is related to the...
difference between peak and steady state as o.5 sec after the stretch. it is related to the velocity of the stretch
105
in spindle is turned on when....
it will have a high firing rate when...
told to be aware of movement
recognizing movement
106
medial lemniscus system =
relays info for discriminative aspects of sensation (perception of body position and movement) and tactile recognition of texture/change in stimuli position
107
in the MLS, first order neurons enter the SC in ____________ of _______. they run ____ and ascend in ____ _____.
do they synapse ?
dorsal roots of spinal nerves
they run rostrally and ascend in the dorsal column.
they do not synapse in the SC
108
spinothalamic system =
relays info for conscious perception of pain, temp, less discriminative tactile sensation (light touch, pressure)
109
rate modulation =
neuron speeds up and firres faster
110
primary receptors are good at __ code
secondary receptors are better at __ code
velocity, length
111
the medial lemniscus pathway carries _______ at the _______, which is used for ________
all sensory information ot the cortex in 3 neuron loop, used for properioception
112
Spindle plays 2 roles:
a reflex role and sends information about conscious perception
113
the GTO is sensitive to ____ tension
internal
114
how is the hoffman reflex created?
1a afferents are activated first, then large diameter motor neurons are activated
