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Neuromuscular Func.
Neuromuscular Function PowerPoint Slides
| Question | Answer |
|---|---|
| Neuromuscular Junction | point where nerve and muscle communicate; product of communication will be a muscle twitch rather than AP |
| Motor Unit | consists of a motor neuron, its axon, and the muscle fibers it innervates; terminal (motor) endplate: end of the axon |
| Acetylcholine (Ach) | the only neurotransmitter dumped into the active zone (cleft) of the neuromuscular junction |
| Miniature Endplate Potential (MEPP) | if there are sufficient MEPPs, a muscle AP will be generated; takes many activated regions to excited a muscle fiber; many muscle fibers must be activated to actually move a muscle and do work |
| striated (skeletal) muscles | long, ropelike structure made up of strands of muscle fiber; each muscle fiber is made up of myofibrils; each myofibril is composed of either thick or thin myofilaments |
| myofibril | comprise muscle fiber; composed of either thick or thin myofilaments |
| myofilaments | comprise myofibril, which comprises muscle fibers |
| muscle fiber contraction | occurs as a result of complex chemical reactions |
| neuromotor innervation | each muscle fiber is innervated by one motor neuron, but each motor neuron may innervate a large number of muscle fibers |
| Multiple Motor Unit Summation | use of many motor neurons to activate a muscle; the more motor neurons that are activated, the greater number of fibers that will contract |
| two types of muscle fibers | 1. slow twitch, 2. fast twitch |
| slow twitch muscle fibers | take a longer time to move; remain contracted five times longer than fast twitch fibers; typically found in muscles the must contract for long periods of time (e.g. antigravity, trunk) |
| Fast Twitch fibers | capable of much more rapid movement; remain contracted for a much shorter period of time; found in muscles used to meet rapid contraction requirements (e.g. articulators, hands, eyes) |
| How many slow twitch fibers can one motor neuron innervate? | thousands |
| How many fast twitch fibers can one motor neuron innervate? | 10 - 20 |
| Neuronal Circuitry for a Spinal Reflex | reflex motor response: stereotyped movement to sensory stimulation; includes muscles spindles, afferent fibers, alpha motor neurons, neuromuscular junction, and muscle tissue (does NOT involve brain) |
| two types of specialized receptors | 1. muscle spindles, 2. golgi tendon organs |
| Muscle Spindles | detect the degree and rate of change in muscle length; help maintain muscle tone; complex small sensorimotor organ; consists of 3 - 5 specialized extrafusal fibers; lies parallel to surrounding extrafusal fibers |
| Extrafusal fibers | make up large mass of the skeletal muscle; attached to bone by fibrous tissue extensions; controlled by alpha motor neurons; composed of myosin filaments; responsible for contractability of a muscle |
| intrafusal muscles | contain muscle spindles; attached to extrafusal fiber; controlled by gamma-motor neurons; both ends contract but central region does not |
| Annulospiral (primary) sensory endings | central region of intrafusal fiber is wrapped by these sensory endings; fast conducting |
| two types of intrafusal fibers | 1. nuclear bag fibers, 2. nuclear chain fibers |
| Golgi tendon organ | innervate the tough tissues that attach the muscles to bone; regulate muscle tension; prevent damage from excessive muscle contraction; excessive contraction stimulates intervening inhibitory interneurons of spinal cord |
| Knee Jerk Reflex- 1 | simplest kind of myotactic reflex: 1. tap the patellar tendon of quadriceps muscle |
| Knee Jerk Reflex- 2 | 2. leads to a brief stretch of the muscle, which stimulates the sensory nerve endings of the spindles |
| Knee Jerk Reflex- 3 | 3. sends a volley of impulses to alpha motor neurons |
| Knee Jerk Reflex- 4 | 4. activation of alpha-motor neurons causes a quick contraction (muscle jerk) of the same muscle |
| Stretch reflexes | stretched muscle contracts after a very brief delay |
Created by:
sullivancl
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