FORM & FUNCTION (Skeletal Muscle Physiology) Flashcards
Endomysium:
-more delicate connective tissue surrounding each muscle fiber
-blood vessels and nerve endings penetrate the muscle within it’s connective tissue
Fascicle:
-bundles of muscle fibers
Perimysium:
-connective tissue surrounding each fascicle
Epimysium:
-external sheath of dense connective tissues
Muscle spindles:
-are stretch receptors
-intrafusal fibers
-detect changes in length of the surrounding striated muscle fibers
Golgi tendon organ:
-detect changes in tension within tendons produced by muscle contraction
-inhibit motor nerve activity if tension becomes excessive
Afferent nerve fibers:
-Ex. muscle spindles and Golgi tendon organ
-relay information to the CNS and regulate muscular contractions
Motor unit:
-a motor neuron and all the muscle fibers it innervates
*a functional contractile unit
Motor nerve:
-a bundle of many motor neurons
-innervates many motor units
Size of motor units:
-small: muscles that control fine movements (fingers, eyes)
-large: large-weight bearing muscles (things, hips)
Series-elastic component:
-non-contractile tendons, connective tissue and structural proteins within sarcomeres have elasticity
*absorb tension as the muscle contracts
*need to stretch out before they will actually move something (time lag/latent period)
Graded muscle responses are:
-variations in the degree of muscle contraction
-required for proper control of skeletal muscle
*possible by changing the frequency or strength of stimulation
Muscle twitch:
-response of a muscle to a single stimulus
Periods of muscle twitch:
- Latent period
- Period of contraction
- Period of relaxation
Latent period:
-due to AP travelling down T-tubule, pulling the proteins, Ca2+ release and the elastic component coupling (stretching)
Period of contraction:
-cross bridges form
>muscle shortens
Period of relaxation:
-Ca2+ reabsorbed
>muscle tension goes to zero
Facilitation/wave summation: different effects/stages
-muscle response
-wave summation
-incomplete tetanus
-complete tetanus
Muscle response:
-a single stimulus leads to one muscle twitch
Wave summation:
-when stimuli are frequent and muscles cannot relax=force of contraction increases
Incomplete tetanus:
-very rapid stimuli result in stronger but incomplete tetanus
Complete tetanus:
-sustained contraction occurs when twitches are fused together due to high-frequency stimuli
Skeletal muscle physiological responses of one motor unit:
- Threshold
- Facilitation
- Tetanic contraction
- Refractory period
Threshold:
-minimum stimulus need to trigger a twitch
Facilitation:
-happens when a new stimulation arrives after a twitch, but before the muscle has fully relaxed or its elastic components have fully recoiled
Tetanic contraction:
-results from frequent stimuli leading to sustained muscle force
-individual twitches no longer evident
Refractory period:
-duration when muscle cannot respond to a second stimulus
Recruitment:
-activation of additional motor units in response to increased stimulus
Threshold stimulus: recruitment
-minimum stimulus required for muscle contraction
Stimulus and response: recruitment:
-muscle contracts with greater force as the stimulus intensifies
Maximum contraction:
-achieved when all motor units are recruited and fully activated
2 types of muscle contraction:
- Isotonic
- Isometric
Isotonic contraction:
-generate tension by shortening the muscle
Isometric contraction:
-muscle length remains constant
Ex. yoga
Length-tension (LT) relationship:
-relationship between muscle length and the force it can produce
LT: optimal length
-at a specific length, muscle fibers overlap perfectly for maximum force
LT: stretched muscle
-reduced overlap of actin-myosin
-decreased force
LT: compressed muscle
-too much overlap
-decreased force
Force-velocity (FV) relationship:
-relationship between the force a muscle produces and the velocity of its contraction
FV inverse relationship:
-as load (or force) on a muscle increases, the velocity of a contraction decrease
Maximum velocity: FV
-achieved during no-load conditions
*property of muscle fiber type
>related to the rate of ATP hydrolysis of the myosin head
Maximum force: FV
-seen at zero velocity (isometric contraction)
Metabolic demands of skeletal muscle:
-largest consumer of ATP in the body
-metabolic flexibility to match energy supply with demand
-adapts to different types and durations of exercise
