MEDICAL PHYSIOLOGY
MED 112 2025 QUESTION AND ANSWER STUDY GUIDE
What is "excitation" in the context of muscle physiology?
The process where an action potential in a nerve fiber leads to one in a muscle fiber
The presynaptic side of the NMJ ends in what structure?
Synaptic knob
What neurotransmitter is released at the NMJ?
Acetylcholine (ACh)
When the nerve action potential reaches the axon terminal, which channels
open?
Voltage-gated calcium channels
How many ACh molecules are released into the synaptic cleft per signal?
About 10,000
What is the small gap between the neuron and muscle fiber called?
Synaptic cleft
What type of receptor does ACh bind to on the muscle membrane?
Ligand-gated ACh receptor
What ions move when the ACh receptor opens?
Na⁺ enters and K⁺ exits the muscle fiber
What happens to the muscle membrane when Na⁺ enters?
It depolarizes
What is the definition of excitation-contraction coupling?
The link between the action potential and myofilament activation
The action potential travels along the muscle fiber membrane called the:
Sarcolemma
What structure carries the action potential deep into the muscle fiber?
Transverse (T) tubules
What does the sarcoplasmic reticulum (SR) release in response to the action
potential?
Calcium ions (Ca²⁺)
What does calcium bind to in the thin filament?
Troponin-C
What happens when calcium binds to troponin-C?
Tropomyosin shifts to expose myosin-binding sites on actin
, According to the sliding filament theory, what happens during contraction?
Filaments slide past one another
What must a myosin head bind to in order to start a contraction cycle?
ATP
What enzyme in the myosin head hydrolyzes ATP?
Myosin ATPase
When ATP is hydrolyzed, what happens to the myosin head?
It "cocks" into a high-energy position
What forms when myosin binds to actin?
Cross-bridge
What is the "power stroke"?
The pivoting of the myosin head pulling actin toward the center
What happens when a new ATP binds to the myosin head?
The head detaches from actin and resets
Which of the following correctly lists the steps of the contraction cycle?
Cross-bridge forms → Power stroke → ATP binds → Myosin resets
In the sliding filament analogy, myosin heads are compared to:
People pulling the rope
In the same analogy, ATP represents:
The fuel for pulling
You can also click the terms or definitions to blur or reveal them
Review with
What is "excitation" in the context of muscle physiology?
The process where an action potential in a nerve fiber leads to one in a muscle fiber
The presynaptic side of the NMJ ends in what structure?
Synaptic knob
What neurotransmitter is released at the NMJ?
Acetylcholine (ACh)
When the nerve action potential reaches the axon terminal, which channels
open?
Voltage-gated calcium channels
How many ACh molecules are released into the synaptic cleft per signal?
About 10,000
What is the small gap between the neuron and muscle fiber called?
Synaptic cleft
MED 112 2025 QUESTION AND ANSWER STUDY GUIDE
What is "excitation" in the context of muscle physiology?
The process where an action potential in a nerve fiber leads to one in a muscle fiber
The presynaptic side of the NMJ ends in what structure?
Synaptic knob
What neurotransmitter is released at the NMJ?
Acetylcholine (ACh)
When the nerve action potential reaches the axon terminal, which channels
open?
Voltage-gated calcium channels
How many ACh molecules are released into the synaptic cleft per signal?
About 10,000
What is the small gap between the neuron and muscle fiber called?
Synaptic cleft
What type of receptor does ACh bind to on the muscle membrane?
Ligand-gated ACh receptor
What ions move when the ACh receptor opens?
Na⁺ enters and K⁺ exits the muscle fiber
What happens to the muscle membrane when Na⁺ enters?
It depolarizes
What is the definition of excitation-contraction coupling?
The link between the action potential and myofilament activation
The action potential travels along the muscle fiber membrane called the:
Sarcolemma
What structure carries the action potential deep into the muscle fiber?
Transverse (T) tubules
What does the sarcoplasmic reticulum (SR) release in response to the action
potential?
Calcium ions (Ca²⁺)
What does calcium bind to in the thin filament?
Troponin-C
What happens when calcium binds to troponin-C?
Tropomyosin shifts to expose myosin-binding sites on actin
, According to the sliding filament theory, what happens during contraction?
Filaments slide past one another
What must a myosin head bind to in order to start a contraction cycle?
ATP
What enzyme in the myosin head hydrolyzes ATP?
Myosin ATPase
When ATP is hydrolyzed, what happens to the myosin head?
It "cocks" into a high-energy position
What forms when myosin binds to actin?
Cross-bridge
What is the "power stroke"?
The pivoting of the myosin head pulling actin toward the center
What happens when a new ATP binds to the myosin head?
The head detaches from actin and resets
Which of the following correctly lists the steps of the contraction cycle?
Cross-bridge forms → Power stroke → ATP binds → Myosin resets
In the sliding filament analogy, myosin heads are compared to:
People pulling the rope
In the same analogy, ATP represents:
The fuel for pulling
You can also click the terms or definitions to blur or reveal them
Review with
What is "excitation" in the context of muscle physiology?
The process where an action potential in a nerve fiber leads to one in a muscle fiber
The presynaptic side of the NMJ ends in what structure?
Synaptic knob
What neurotransmitter is released at the NMJ?
Acetylcholine (ACh)
When the nerve action potential reaches the axon terminal, which channels
open?
Voltage-gated calcium channels
How many ACh molecules are released into the synaptic cleft per signal?
About 10,000
What is the small gap between the neuron and muscle fiber called?
Synaptic cleft
