ANP College Course Study Guide: Muscle, Bone, and Endocrine Physiology

Q1. Define and describe the following connective tissue layers of muscle: endomysium, perimysium, and epimysium.

Background

Topic: Skeletal Muscle Structure

This question tests your understanding of the organization of skeletal muscle at the tissue level, specifically the connective tissue layers that surround different parts of the muscle.

Key Terms:

• Endomysium: Thin connective tissue surrounding each muscle fiber.

• Perimysium: Connective tissue that surrounds bundles of muscle fibers (fascicles).

• Epimysium: Dense connective tissue that surrounds the entire muscle.

Step-by-Step Guidance

1. Start by identifying the hierarchical organization of skeletal muscle: muscle → fascicle → muscle fiber.

2. Describe which connective tissue layer is associated with each level (fiber, fascicle, whole muscle).

3. Explain the function of each layer (e.g., protection, support, transmission of force).

4. Consider how these layers contribute to the overall function and structure of skeletal muscle.

Try describing each layer and its function before checking the answer!

Q2. Differentiate between myosin and actin. Which proteins are present in each?

Background

Topic: Muscle Fiber Proteins

This question assesses your knowledge of the main contractile proteins in muscle and their associated proteins.

Key Terms:

• Myosin: Thick filament protein with heads that bind to actin.

• Actin: Thin filament protein that interacts with myosin for contraction.

• Associated proteins: tropomyosin, troponin (on thin filaments).

Step-by-Step Guidance

1. Define myosin and actin, noting their roles in muscle contraction.

2. List the proteins that are part of the thick filament (myosin) and those that are part of the thin filament (actin, tropomyosin, troponin).

3. Explain how these proteins interact during muscle contraction.

Try listing the proteins for each filament before checking the answer!

Q3. Draw and label a muscle fiber showing the I band, A band, M line, Z disc, and H zone.

Background

Topic: Sarcomere Structure

This question tests your ability to identify and label the structural components of a sarcomere, the functional unit of muscle contraction.

Key Terms:

• I band: Region with only thin filaments.

• A band: Length of thick filaments (may overlap with thin filaments).

• M line: Center of the A band, where thick filaments are linked.

• Z disc: Boundary of the sarcomere, anchors thin filaments.

• H zone: Central region of A band with only thick filaments.

Step-by-Step Guidance

1. Start by sketching a sarcomere (rectangle with vertical lines for Z discs).

2. Label the Z discs at each end.

3. Mark the A band (entire length of thick filaments) and I band (region with only thin filaments).

4. Identify the M line in the center and the H zone (area with only thick filaments).

Try drawing and labeling the sarcomere before checking the answer!

Q4. Describe the sliding filament mechanism. What happens to the thin and thick filaments, and to the I band, A band, M line, Z disc, and H zone during contraction?

Background

Topic: Muscle Contraction Mechanism

This question examines your understanding of how muscle fibers contract at the molecular level.

Key Concepts:

• Sliding Filament Theory: Thin filaments slide past thick filaments, shortening the sarcomere.

• Changes in band and zone lengths during contraction.

Step-by-Step Guidance

1. Describe the interaction between actin (thin) and myosin (thick) filaments during contraction.

2. Explain which bands/zones shorten (I band, H zone) and which remain the same (A band).

3. Discuss the movement of Z discs and the role of the M line.

4. Summarize the overall effect on sarcomere length.

Try explaining the changes during contraction before checking the answer!

Q5. What is the synapse of a motor neuron?

Background

Topic: Neuromuscular Junction

This question tests your knowledge of the site where a motor neuron communicates with a muscle fiber.

Key Terms:

• Synapse: Junction between two cells for communication.

• Neuromuscular Junction (NMJ): Synapse between a motor neuron and a muscle fiber.

Step-by-Step Guidance

1. Define what a synapse is in general terms.

2. Describe the specific structure and function of the neuromuscular junction.

3. Identify the components: axon terminal, synaptic cleft, motor end plate.

Try defining the NMJ and its components before checking the answer!

Q6. Describe the events of muscle excitation starting with the arrival of an action potential at the axon terminal until the entry of Na+ ions in the muscle fiber.

Background

Topic: Muscle Excitation

This question assesses your understanding of the sequence of events that lead to muscle fiber depolarization.

Key Steps:

• Action potential arrival

• Neurotransmitter release (acetylcholine)

• Binding to receptors

• Opening of ion channels

• Na+ influx

Step-by-Step Guidance

1. Describe what happens when the action potential reaches the axon terminal.

2. Explain the release of acetylcholine into the synaptic cleft.

3. Discuss how acetylcholine binds to receptors on the motor end plate.

4. Describe the opening of ligand-gated Na+ channels and the resulting influx of Na+ ions.

Try outlining the sequence before checking the answer!

Q7. What is the required ion for excitation-contraction coupling to occur?

Background

Topic: Excitation-Contraction Coupling

This question tests your knowledge of the key ion involved in linking muscle excitation to contraction.

Key Term:

• Calcium (Ca2+): Essential for triggering contraction.

Step-by-Step Guidance

1. Recall the process of excitation-contraction coupling.

2. Identify the ion that binds to troponin, causing conformational changes in the thin filament.

3. Explain how this ion's presence leads to cross-bridge formation.

Try identifying the ion and its role before checking the answer!

Q8. Which organelle of muscle fibers stores calcium? When is calcium released into the cytosol?

Background

Topic: Muscle Fiber Organelles

This question examines your understanding of calcium storage and release in muscle contraction.

Key Terms:

• Sarcoplasmic Reticulum (SR): Organelle that stores Ca2+.

• Calcium Release: Triggered by action potential.

Step-by-Step Guidance

1. Identify the organelle responsible for calcium storage in muscle fibers.

2. Describe the signal that causes calcium release from the SR.

3. Explain the importance of calcium release for muscle contraction.

Try explaining the process before checking the answer!

Q9. What is a power stroke? Describe what happens to myosin and actin. What is the role of calcium? What is the role of ATP?

Background

Topic: Cross-Bridge Cycle

This question tests your understanding of the molecular events during muscle contraction.

Key Concepts:

• Power Stroke: Movement of myosin head pulling actin filament.

• Calcium: Binds to troponin, exposing binding sites.

• ATP: Required for detachment and re-cocking of myosin head.

Step-by-Step Guidance

1. Describe the binding of myosin to actin after calcium exposes binding sites.

2. Explain the conformational change (power stroke) that moves actin.

3. Discuss the role of ATP in detaching myosin and resetting the head.

4. Summarize the cycle's dependence on calcium and ATP.

Try outlining the steps of the power stroke before checking the answer!

Q10. Differentiate between isotonic and isometric contractions.

Background

Topic: Types of Muscle Contraction

This question assesses your understanding of the differences between muscle contractions that change length versus those that do not.

Key Terms:

• Isotonic Contraction: Muscle changes length (shortens or lengthens) while tension remains constant.

• Isometric Contraction: Muscle tension increases, but length does not change.

Step-by-Step Guidance

1. Define isotonic and isometric contractions.

2. Provide examples of each type (e.g., lifting a weight vs. holding a weight steady).

3. Explain the physiological significance of each type.

Try defining and giving examples before checking the answer!