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Neuromotor system organization central
nervous system (CNS)
brainspinal cord TERM 2
Neuromotor system peripheral nervous
system (PNS)
DEFINITION 2 12 cranial nerves31 pairs of spinal nerves TERM 3
neurotransmitters
DEFINITION 3 chemical messengers: diffuse across a synapse to combine with targeted receptor molecule on postsynaptic membrane to facilitate depolarization or hyperpolarization TERM 4
Peripheral nervous system
DEFINITION 4 31 pairs of spinal nerves- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccgeal 12 pairs of cranial nerves- afferent nerves: relay sensory info, from muscles, joints, skin, bones toward brain. Efferent nerves: transmit info away from brain to glands and muscles somatic and autonomic nervous system TERM 5
components of PNS somatic
DEFINITION 5 innervates skeletal muscle somatic efferent nerve firing excites muscle activation
autonomic reflex arc:
patellar reflex* TERM 7
complex reflexes:
DEFINITION 7 crossed- extensor reflex * TERM 8
Nerve supply to muscle
DEFINITION 8 about 420,000 motor nerves exist; a single nerve usually supplies numerous individual muscle fibers. ratio of muscle fibers to nerves relates to muscle's particular movements basic rule: less complex movements have a higher ratio of muscle fibers to motor nerves. Complex eye and hand movements requiring more specialized movements have a considerably lower ratio TERM 9
motor units
DEFINITION 9 skeletal muscle fibers and their corresponding innervating anterior (alpha) motor neuron: represents movements functional unit whole muscle contains many motor units, each with a single motoneuron and its composite muscle fibers TERM 10
motor unit anatomy
DEFINITION 10 cell body houses control center axon extends from cord and delivers impulse to muscle fibers it nnervates dendrites receive impulses through spinal cord connections and conduct them toward the cell body nerve cells conduct impulses in one direction only-- down axon away from stimulation point all of a motor units muscle fibers disperse over subregions of muscles with other motor unit fibers
fiber types
fast fatigable (FF) force production- high. Contraction speed- fast. Fatigue resistance- low. muscle fiber type- fast glycolytic. SAG- yes fast fatigue-resistance (FR)- force production- moderate. speed- fast. resistance- moderate. SAG-yes. type- fast- oxidative- glycolutic (FOG) slow (S)- force production- low. speed-slow. resistance- high. SAG- No. type- Slow-oxidative (SO) TERM 17
three physiologic and mechanical motor unit
and muscle properties of innervation
DEFINITION 17 twitch ( speed of contraction) characteristics tension-generating (force) characteristics neuromuscular fatigability TERM 18
all of none principle
DEFINITION 18 all accompanying muscle fibers act synchronously if stimulus triggers a motoneuron's action potential. single motor unit cannot generate strong and weak contractions- an impulse either elicits an action or it does not once the neuron fires and the impulse reaches the neuromuscular junction. muscles cells always act to their fullest extent TERM 19
gradution of force principle
DEFINITION 19 force of muscle action varies from slight to max in one of two ways: increasing number of recruited motor units increasing frequency of motor unit discharge TERM 20
motor unit
recruitment
DEFINITION 20 process of adding motor units to increase force size principle: motoneurons with progressively larger axons become recruited as muscle force increases selective recruitment and firing pattern of fast-twitch and slow- twitch motor units that control movement serve as the mechanism to produce the desired, coordinated response relative to intensity
neuromuscular fatigability
decline in muscle tension or force capacity with repeated stimulation four factors decrease force-generating capacity: PA induced alterations in levels of neurotransmitters reduced glycogen content in active muscle fibers occurs during prolonged PA increased levels of blood and muscle lactate fatigue occurs at the neuromuscular junction TERM 22
proprioceptors
DEFINITION 22 specialized sensory receptors sensitve to stretch, tension, and pressure in muscle, joints, tendons relay critical information about: muscular dynamics, limb position, kinesthesia, proprioception to conscious and subconscious portions of the CNS allow continual monitoring of progress of any movement or sequence of movements and provide the framework for modifying subsequent motor actions TERM 23
muscle spindles
DEFINITION 23 provide mechanosensory info. about changes in muscle fiber length and tension respond to muscle stretch through reflex action by initiating a stronger muscle action to counteract the stretch more spindles exist in muscles that routinely perform complex movements TERM 24
stretch reflex
DEFINITION 24 stretch reflex consists of three parts muscle spindles: responds to stretch afferent nerve fibers: carries sensory impulse from spindle to spinal cord efferent spinal cord motor neuron: activates stretched muscle fibers TERM 25
gogi tendon organs
DEFINITION 25 connect in series to extrafusal fibers and also located in joint ligaments to detect differences in muscle tension than length when activated by muscle tension or stretch, golgi receptors immediately transmit signals to cause reflex inhibition protect muscle and its connective tissue harness from injury by sudden excessive load or stretch
