BIOL 1412 - SKELETAL MUSCLE
PHYSIOLOGY EXAM QUESTIONS WITH
100% CORRECT ANSWERS LATEST
VERSION 2025/2026.
Muscle Characteristics - ANS - Excitable (respond to stimuli by producing action potentials)
- Contractile (can shorten, thicken)
- Extensible (stretch when pulled)
- Elastic (return to original shape after contraction or extension)
Muscle Functions - ANS - Movement (walking, breathing)
- Posture, facial expression - Heat production (to get to 37C)
- Protection of viscera (body wall)
Neuromuscular Junction - ANS - Each muscle fibre (cell) innervated by only 1 neuron.
- Axon of motor neuron branches to innervate several muscle fibres (1 neuron = ~150 fibres
within the same whole muscle)
- A single motor neuron and ALL the muscle fibres it innervates = a motor unit
Neuromuscular Junction Structure - ANS - Presynaptic cell (neuron) with ACh (nt) in vesicles
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, - Postsynaptic cell (muscle) membrane (sarcolemma) = specialized region with ACh receptors
(motor end plate)
- Two membranes separated by synaptic cleft.
Neuromuscular Junction Function - ANS - 1) AP reaches axon terminal and synaptic end bulb
of neuron.
- 2) Ca++ enters via voltage gates, causes exocytosis of ACh
- 3) ACh binds to ACh receptors on motor end plate
- 4) Chemical gates open and Na+ enters causes End Plate Potential (EPP = a
depolarizing GP)
- 5) EPP causes opening of Na+ voltage gates on adjacent sarcolemma which causes AP
(AP has same properties/channels as on a neuron) this propagates along sarcolemma
Molecular Basis of a relaxed muscle - ANS - Tropomyosin covers myosin binding sites on the
actin
- The myosin head is activated
Myosin Head Activation - ANS - ATP breaks down into ADP, Pi, and releases energy
- Once binding sites on actin are exposed, myosin binds
Sliding Filament Mechanism - ANS - Sarcomeres shorten: H zone, I band shorten, A band =
same length
- Myofibrils shorten, therefore muscle shortens
- Thin (actin) and thick (myosin) myofilaments remain the same length
Step 1: Excitation of muscle fibre (electrical event) - ANS - 1) Sarcolemma depolarized - EPP
produces AP
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
PHYSIOLOGY EXAM QUESTIONS WITH
100% CORRECT ANSWERS LATEST
VERSION 2025/2026.
Muscle Characteristics - ANS - Excitable (respond to stimuli by producing action potentials)
- Contractile (can shorten, thicken)
- Extensible (stretch when pulled)
- Elastic (return to original shape after contraction or extension)
Muscle Functions - ANS - Movement (walking, breathing)
- Posture, facial expression - Heat production (to get to 37C)
- Protection of viscera (body wall)
Neuromuscular Junction - ANS - Each muscle fibre (cell) innervated by only 1 neuron.
- Axon of motor neuron branches to innervate several muscle fibres (1 neuron = ~150 fibres
within the same whole muscle)
- A single motor neuron and ALL the muscle fibres it innervates = a motor unit
Neuromuscular Junction Structure - ANS - Presynaptic cell (neuron) with ACh (nt) in vesicles
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, - Postsynaptic cell (muscle) membrane (sarcolemma) = specialized region with ACh receptors
(motor end plate)
- Two membranes separated by synaptic cleft.
Neuromuscular Junction Function - ANS - 1) AP reaches axon terminal and synaptic end bulb
of neuron.
- 2) Ca++ enters via voltage gates, causes exocytosis of ACh
- 3) ACh binds to ACh receptors on motor end plate
- 4) Chemical gates open and Na+ enters causes End Plate Potential (EPP = a
depolarizing GP)
- 5) EPP causes opening of Na+ voltage gates on adjacent sarcolemma which causes AP
(AP has same properties/channels as on a neuron) this propagates along sarcolemma
Molecular Basis of a relaxed muscle - ANS - Tropomyosin covers myosin binding sites on the
actin
- The myosin head is activated
Myosin Head Activation - ANS - ATP breaks down into ADP, Pi, and releases energy
- Once binding sites on actin are exposed, myosin binds
Sliding Filament Mechanism - ANS - Sarcomeres shorten: H zone, I band shorten, A band =
same length
- Myofibrils shorten, therefore muscle shortens
- Thin (actin) and thick (myosin) myofilaments remain the same length
Step 1: Excitation of muscle fibre (electrical event) - ANS - 1) Sarcolemma depolarized - EPP
produces AP
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
