Neuromuscular System & Exercise Flashcards
What is a brain neurotransmitter
- chemical messenger that diffuse across the synapse to combine with a targeted receptor molecule on the postsynaptic membrane to facilitate depolarization or hyperpolarization
What does the peripheral nervous system include
- afferent nerves that relay sensory information from muscles, joints, skin, & bones toward the brain
- efferent nerves that transmit information away from the brain to glands & muscles
- somatic & autonomic nervous systems
What does the somatic nervous system do
- innervates skeletal muscle
- somatic efferent nerve firing excites muscle activation
What does the autonomic nervous system do
- innervates smooth muscle in intestines, sweat & salivary glands, myocardium, & some endocrine glands
- includes the sympathetic & parasympathetic nervous systems
- sympathetic nerve fibers mediate excitation
- parasympathetic activation inhibits excitation
What does the sympathetic nervous system supply & do
- supplies the heart, smooth muscle, sweat glands, & viscera
- excitation occurs during fight-or-flight situations that require whole body arousal for emergencies
- accelerates breathing & heart rate, pupils dilate, & blood flows from the skin to deeper tissues
What does the parasympathetic nervous system supply & do
- supplies the thorax, abdomen, & pelvic regions
- releases acetylcholine
- the postganglionic parasympathetic nerve fibers produce effects opposite of sympathetic fibers
What does a motor unit consist of
- cell body houses the control center
- axon extends from the cord & delivers an impulse to the muscle fibers it innervates
- dendrites receive impulses through spinal cord connections & conduct them toward the cell body
What allows for higher transmission velocity in a motor unit
- nodes of ranvier
What encases the bare axon of a motor unit
- Schwann cells in the peripheral nervous system encase the bare axon & then spiral around it
Describe the roles of the neuromuscular junction/motor end plate
- provides interface b/w the end of a myelinated motoneuron & a muscle fiber
- functions to transmit nerve impulses to muscle fibers
- presynaptic terminals lie close to with the sarcolemma
- synaptic cleft is the region where neural impulse transmission occurs
- excitation occurs at the neuromuscular junction
What is the all-or-none principle
- if a stimulus triggers an action potential in the motoneuron then all of the accompanying muscle fibers contract synchronously
- once the neuron fires & the impulse reaches the neuromuscular junction, the muscle cells always contract to the fullest extent
What is gradation of force principle
- the force of muscle action varies from slight to maximal in one of two mechanisms
- increasing the number of motor units recruited
- increasing the frequency of motor unit discharge (to create a summation of muscle contraction)
What is motor unit recruitment & size principle
Motor unit recruitment: the process of adding motor units to increase muscle force
Size principle: motoneurons with larger axons become recruited as muscle force increases
What provides the mechanism to produce the desired coordinated response
- selective recruitment & firing pattern of the fast-twitch & slow-twitch motor units that control movement
Define neuromuscular fatigability
- the decline in muscle tension or force capacity with repeated stimulation during a given time period
