Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

9. Muscle Tissue

Structure of a Skeletal Muscle

Anatomy & Physiology

9. Muscle Tissue

Structure of a Skeletal Muscle

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3:30 minutes

Problem 24

Textbook Question

How does cardiac muscle tissue contract without neural stimulation?

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Cardiac muscle tissue contracts without neural stimulation due to the presence of specialized cells called pacemaker cells, which are located in the sinoatrial (SA) node of the heart. These cells generate electrical impulses spontaneously.

The pacemaker cells in the SA node have an unstable resting membrane potential, which gradually depolarizes due to the slow influx of sodium ions (Na⁺) through 'funny' channels (If channels). This process is called the pacemaker potential.

Once the pacemaker potential reaches the threshold, voltage-gated calcium channels open, allowing calcium ions (Ca²⁺) to enter the cells. This influx of calcium triggers the action potential, which spreads across the heart tissue.

The action potential travels through the conduction system of the heart, including the atrioventricular (AV) node, bundle of His, and Purkinje fibers, ensuring coordinated contraction of the atria and ventricles.

This intrinsic conduction system allows the heart to contract rhythmically and independently of external neural input, although the autonomic nervous system can modulate the heart rate and strength of contraction as needed.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cardiac Muscle Tissue

Cardiac muscle tissue is a specialized type of muscle found only in the heart. It is striated and involuntary, meaning it contracts without conscious control. Cardiac muscle cells, or cardiomyocytes, are interconnected by intercalated discs, which facilitate synchronized contractions essential for effective heart function.

Automaticity

Automaticity refers to the ability of cardiac muscle cells to generate electrical impulses spontaneously. This property allows the heart to initiate its own contractions without external neural stimulation. The sinoatrial (SA) node, often called the heart's natural pacemaker, plays a crucial role in this process by producing rhythmic electrical signals that trigger heartbeats.

Excitation-Contraction Coupling

Excitation-contraction coupling is the physiological process that links the electrical activity of cardiac muscle cells to their contraction. When an action potential reaches the muscle cell, it triggers the release of calcium ions from the sarcoplasmic reticulum. This increase in calcium concentration initiates the interaction between actin and myosin filaments, leading to muscle contraction.

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Textbook Question

Compartment syndrome can result from all of the following except

(a) Compressing a nerve in the wrist

(b) Compartments swelling with blood due to an injury involving blood vessels

(d) Pulled tendons in the muscles of a given compartment

(e) Torn muscles in a particular compartment

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Textbook Question

Which of the following statements about myofibrils is not correct?

(a) Each skeletal muscle fiber contains hundreds to thousands of myofibrils.

(b) Myofibrils contain repeating units called sarcomeres.

(d) Filaments consist of bundles of myofibrils.

(e) Myofibrils are attached to the plasma membrane at both ends of a muscle fiber.

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Textbook Question

An action potential can travel quickly from one cardiac muscle cell to another because of the presence of

(a) Gap junctions

(b) Tight junctions

(d) Both a and c

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Textbook Question

What three layers of connective tissue are part of each muscle? What functional role does each layer play?

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Textbook Question

Muscle tone keeps muscles healthy. What is muscle tone, and what causes it? What happens to a muscle that loses its tone?

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Textbook Question

Identify the structures in the following figure.

<IMAGE>

a. ___

b. ___

c. ___

d. ___

e. ___

f. ___

g. ___

h. ___

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Textbook Question

Bill broke his leg in a football game, and after six weeks the cast is finally removed. As he steps down from the examination table, he loses his balance and falls. Why?

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Textbook Question

Your ability to lift that heavy couch would be increased by which type of exercise?

a. Aerobic

b. Endurance

c. Resistance

d. Swimming

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