Flashcards in Physiology Deck (47)
What is the largest tissue type in the body?
All muscle in the body is striated. True/False?
Smooth muscle is not striated
Which division of the nervous system - autonomic or somatic - innervates skeletal muscle?
Skeletal muscle fibres are organised into motor units. What are motor units?
Motor neuron + all the muscle fibres innervated by that single motor neuron
What determines the number of muscle fibres per motor unit?
The function of the muscle (whether it is concerned with powerful or precise movement)
Give examples of muscles that have few muscle fibres per motor unit
External eye muscles
Muscles of facial expression
Intrinsic hand muscles
What is contained within a muscle fibre?
Myofibrils and sarcomeres
Skeletal muscle contraction is brought about by myogenic initiation. True/False?
Neurogenic (nerve stimulated first)
Are there gap junctions between muscle fibres?
Which substance is released in response to action potential generation + presence in the T-tubule of the muscle fibre?
What does calcium release by the sarcoplasmic reticulum cause?
Calcium binds to troponin, causing conformational change in tropomyosin complex to expose myosin-binding-site on actin to allow cross-bridge formation between actin and myosin
List the 4 zones of a sarcomere
What does the A-band consist of?
Myosin + portion of actin that overlaps with myosin
Where is the H-zone?
Lighter area within A-band where actin doesn't reach
Where is the M-line?
Extends vertically down the middle of the A-band within the centre of the H-zone
What does the I-band consist of?
Remaining portion of actin that is not part of the A-band
What 2 primary factors determine gradation of skeletal muscle tension?
Number of muscle fibres contracting within the muscle
Tension developed by each muscle fibre
What is meant by "motor unit recruitment"?
Stimulating numerous motor units to contract elicits stronger contraction
Tetanic contractions of skeletal muscle are not possible. True/False?
How is tetanic contraction of skeletal muscle brought about?
Generation of numerous action potentials one after the other amplify the contraction/skeletal muscle twitch
When can maximum tetanic contraction of skeletal muscle be achieved?
At rest (optimal length of muscle at this point)
Name the 2 main types of skeletal muscle contraction
What is isotonic skeletal muscle contraction used for?
Muscle length changes in isotonic skeletal muscle contraction. True/False?
Muscle tension remains constant
What is isometric skeletal muscle contraction used for?
Maintaining fixed positions
Muscle length changes in isometric skeletal muscle contraction. True/False?
Muscle length is constant to allow tension to develop
Velocity of muscle length shortening increases/decreases with increasing load
What is the stretch reflex?
Negative feedback mechanism that resists passive change to muscle length by contracting the muscle
Once a muscle is stretched, how does the stretch reflex elicit contraction?
Afferent fibres fire and synapse with alpha motor neurons which, when stimulated, contract the stretched muscle