Skeletal Muscle Physiology Flashcards
Name some of the overall physiological functions of skeletal muscle
Maintaining posture
Purposeful movement
Respiratory movement
Heat production
What are the three types of muscles in the body?
Skeletal
Cardiac
Smooth
Which types of muscle are striated?
Skeletal
Cardiac
Skeletal muscle is innervated by the somatic/autonomic nervous system and is subject to voluntary/involuntary control.
Somatic
Voluntary
Skeletal muscle has neurogenic/myogenic initiation of contraction
Neurogenic
What is the neurogenic transmitter?
ACh
What are skeletal muscle fibres organised into?
Motor units
Define a motor unit
A single alpha motor neuron and all the skeletal muscle fibres it innervates
Muscles serving precise movements have many muscle fibres per motor unit. True/false?
False - have few muscle fibres per motor units
Give some examples of muscles with few fibres per motor unit
Intrinsic hand muscles
Extra-ocular muscles
What is the overall organisation of skeletal muscle?
Muscle -> muscle fibre -> myofibril -> sarcomere
What is the functional unit of muscle?
Sarcomere
Actin and myocin are arranged into sarcomeres. True/false?
True
What produces muscle tension?
Actin sliding on myosin
What is required for contraction and relaxation of muscle?
ATP
What switches on cross-bridge formation between actin and myosin?
Calcium
Calcium binds to what in switching on cross bridge formation?
Troponin
What occurs when there is no ATP to contract or relax skeletal muscle?
Rigor complex
What are the two main factors in the gradation of skeletal muscle tension?
Number of muscle fibres contracting
Tension developed by each contracting fibre
What effect does a shorter action potential than the duration of twitch have on muscle contraction?
It means repeated stimulation can bring about stronger and eventually tetanic contraction
Tetanic contraction of cardiac muscle is normal. True/false?
False
What is the optimum length of the muscle fibre for contraction?
Its normal resting length
What is isotonic contraction of muscle?
When muscle tension remains constant but muscle fibre length changes
When do isotonic contractions occur?
Body movements
Moving objects
What is isometric contraction of muscle?
When muscle fibre length remains constant but muscle tension changes
When do isometric contractions occur?
Supporting objects in fixed positions
Maintaining body posture
What are the main differences between types of skeletal muscle fibres?
Pathway for ATP synthesis
Resistance to fatigue
Activity of myosin ATPase
Each motor unit usually contains only one type of fibre. True/false?
True
What are the metabolic pathways supplying ATP in muscle fibre?
Creatine phosphate
Oxidative phosphorylation
Glycolysis
Name the three types of skeletal muscle fibres.
Type I (slow-oxidative) Type IIa (fast-oxidative) Type IIx (fast glycolytic)
Why are type I fibres slow?
Low myosin ATPase activity
What is the main difference between type IIa and IIx muscle fibres?
IIa have high oxidative phosphorylation capacity
IIx have low
What are type I fibres used for?
Prolonged low work aerobic activities (walking)
What are type IIa fibres used for?
Prolonged moderate work activities (jogging)
What are type IIx fibres used for?
Short-term high intensity activities (jumping)
What occurs in the stretch reflex?
Stretching of muscle spindle increases afferent neuron firing which synapse in the spinal cord with the alpha motor neurons resulting in contraction of stretched muscle
The knee jerk assesses which peripheral nerve?
Femoral
Give some causes of myopathy
Congenital
Muscular dystrophy
Inflammation
Toxicity
Give some symptoms of myopathy
Muscle weakness
Myalgia
Muscle stiffness
