motor system I&II Pearson Flashcards
neurons that innervate motor units
alpha motor neurons
components of a motor unit
one neuron which innervates several muscle fibers
sow motor untis
generate small forces, think gentle touch. The neurons are smaller, the axons are thinner, less oxidation muscle fibers are innervated. In general, these units make small forces, and fatigue slowly. They are recruited first
fast fatigue resistant
Generate large forces, but fatigue slowly. These are recruited second
Fast fatigue
The big dogs. Strong, fatigue fast, last to be recruited. Hulk status - light weight baby! One fat neuron innervates a small city of fibers.
Why are different fibers recruited in different orders
it allows the amount of force and energy expenditure to be controlled and tuned to meet the demands of a given situation
Why are small neurons depolarized first?
Ohms law. Small neurons depolarize first, where as large neurons take a lot of stimulation to depolarize. This allows the body the activate the small neurons, and small muscle fibers first.
summation of epsp does what?
totals up the signal to activate the big dogs! means the large fibers are activated
what happens when fibers are innervated by other neurons?
The fibers change their role. Slow soft can become fast strong. Transition from white to red, or red to white, or big to small - etc.
effect of endurance training?
increases fatigue resistant fibers
effect of lifting?
get huge. strong forces, but fast fatigue
intrafusal muscle fiber
are contractile muscle fibers, but not enough o generate force. These fibers are the sensory mechanotransduction fibers. These things also receive innervation from gamma motor neurons.
extrafusal muscle fibers
these are the force generating fibers
what happens when muscle is unexpectedly stretched?
the gamma transmit signal to the spinal chord, which uses and interneuron to synapse on the alphas neurons, then the alphas contract the muscle to resist the stretch
stretch reflex?
when a muscle is stretched, it contracts to resist.
tone?
all fibers are constantly stimulated at a basal rate, lading to muscle tone
reciprocal innervation
only the same muscle that is stretched is the muscle that contracts via the stretch reflex. Also, inhibitory interneurons case opposing muscle groups to relax.
what happens when muscle is signaled to contract (think both intrafusal and extrafusal)
both units contract.
reflexive shortening on contraction
look it up
error correction
voluntary contraction contracts both alpha and gamma. the gamma are reortsing back on tone, and the relationship is stable if stretch and contraction are equal. If contraction exceeds stretch, relaxation is noted by the itrafuasal fiber. The slack causes a drop in fiber rate, which decreases the force being applied. Converse is true too, not enough force leads to intrafual stretch, and feedback causes increased contraction.
If have an older brother, you maybe familiar with ways to circumvent this problem and cause your siblings to hit themselves in the face.
1b afferent fibers
stretch neuron in tendon golgi organs
golgi tendon organ
1b afferent neuron located in tendons which lead to inhibition to muscle becoming slack, and tenses the opposing muscle group
compare muscle spindle to golgi tendon organ
golgis: in sries with muscle, preferentially signal muscle tensin, important for stablizing contcations, composed of collagen fibers and capsule, signals via Ib afferent, not cotractile
spindle: in parrallel with muscle. signals muscle stretch, important for muscle tone, composed of muscle fibers, signals via Ia afferents, innervated by gamma motor neurons
crossed extensor-flexor coupling
relaxation of appendage sensing nocioceptive stimuli, while contralateral appendage contracts. Allows flexion of hurt appendage (retraction) while appropriate extension is initiated on the opposite side. In summery, you will not fall over when you step on a tac.
locomoter patterning
means while one leg has activation of extensor, the extenros is inhibited in the opposite leg. This is mediated by collateral neurons in the spinal cord.
central pattern generators
coordination of many locomoter patterns that allows the coordination of gate.
pattering after spinal cord injury?
tots. The central patterning can work after an animal is paralzyed. Means this is coded at the level of the spinal cord.
dopamine or afferent sensory stim can help this process, but this happens without these stimuli, meaning sensory feedback is not important for central patterning.
spinal prep
look it up
deafferented preparation
look it up
decerebrate preparation
look it up
lower motor neuron syndrome
damage to lower motor neuron cell bodies (ie alpha neurons). Paralysis, paresis, loss of reflex, loss of muscle tone, atrophy, spontaneous switches as muscles become deinnervated.
causes of LMNS
syphilis, dorsal root ganglia herniated disk, pinch nerve roots polio/als, motor neuron degeneration guillian barre, demyelination of periferal nerve lambert-eaton, ca channel immune target myesthinea gravis DMD
brainstem control of movement
organization axial musculature
maintain balance
regulate posture
orient gaze
mesencaphilic locomoter center
causes locomotion originating in the brain stem.
reticulospinal tract
vestibulospinal tract
VOR circuitry
reticulospinal tract
riinates around the pons, stops in the medial vetral horn. Used for balance correction. If you torture cats, as they deserve to be tortured, the cats will not have balance.
vestibulospinal tract
originates in the innerear, detects tilt, and then send s the info to the rest of the body. Maintains balance. This is activated in unexpected falls. Vestibulospinal reflex. Fall and put hand down without thinking
Vor circuitry
cant track objects as they move faster. Can organize eye movement.
