Principles of muscular system

Question 1

What are muscle cells specialized for?

Answer 1

Muscle cells are specialized for generating motile forces through the interaction of proteins, specifically actin and myosin.

Question 2

What are the components of muscle structure?

Answer 2

Epimysium: Surrounds the entire muscle.
Perimysium: Surrounds muscle bundles.
Endomysium: Surrounds muscle fibers.
Muscle Fascicle: Bundle of muscle fibers.

Question 3

What are the components of muscle cell structure?

Answer 3

Cell Membrane: Surrounds each cell, composed of a lipid bilayer.
Cytoplasm: Internal fluid of the cell, containing various organelles.
Endoplasmic Reticulum: Series of sacs involved in protein and lipid synthesis and transport.

Question 4

What are the muscle-specific terms for cell membrane, cell cytoplasm, endoplasmic reticulum, and functional contractile unit?

Answer 4

Cell membrane: Sarcolemma
Cell cytoplasm: Sarcoplasm
Endoplasmic reticulum: Sarcoplasmic reticulum
Functional contractile unit: Sarcomere

Question 5

What are the three types of muscle?

Answer 5

Skeletal muscle
Cardiac muscle
Smooth muscle

Question 6

What are the characteristics of skeletal muscle?

Answer 6

Parallel bundles with stripes
Majority of muscle in the body
Capable of powerful contractions
Force is proportional to cross-sectional area
Moves bones and provides support for posture
Innervated by somatic and branchial motor nerves
Each skeletal muscle cell forms from fusion of myoblasts
Mature cells are multinucleated with peripheral nuclei

Question 7

What are the characteristics of cardiac muscle?

Answer 7

Striped muscle similar to skeletal muscle
Found in the heart wall (myocardium) and great vessel walls
Branching network of cells linked electrically and mechanically
Contractions are less powerful than skeletal muscle but resistant to fatigue
Innervated by visceral motor nerves (parasympathetic and sympathetic)
Central nucleus, shorter cells than skeletal muscle
Fibers arranged in whorls and spirals
Contains specialized conducting system called Purkinje fibers

Question 8

What are the characteristics of smooth muscle?

Answer 8

Smooth muscle has no stripes.
It consists of elongated spindle-shaped fibers.
Capable of slow and sustained contractions.
Found in various locations, including blood vessel walls, hair follicles, eyeball, and viscera.
Innervated by autonomic secretomotor nerves.

Question 9

What are the types of muscle based on control, appearance, and association?

Answer 9

Skeletal muscle: Voluntary control, striated appearance, associated with the body wall (somatic).
Cardiac muscle: Involuntary control, striated appearance, associated with the heart (visceral).
Smooth muscle: Involuntary control, smooth appearance, associated with organs and blood vessels (visceral).

Question 10

What is the origin attachment in skeletal muscle?

Answer 10

The origin is the proximal attachment, usually the stationary end.

Question 11

What is the insertion attachment in skeletal muscle?

Answer 11

The insertion is the distal attachment, usually the mobile end.

Question 12

What are the types of attachments in skeletal muscle?

Answer 12

There are three types of attachments: anatomically distinct tendons, broad areas of anchorage to a bony surface, and broad areas of anchorage to sheets of fibrocollagenous support tissue (fascia) which run between muscles.

Question 13

What is the structure of tendons?

Answer 13

Tendons are cylindrical structures composed of tightly packed longitudinally running collagen fibers.

Question 14

What is the largest tendon in the body?

Answer 14

The largest tendon in the body is the Achilles tendon, which connects the calf muscles to the calcaneum (heel bone).

Question 15

What is the role of fibrocytes in tendons?

Answer 15

Fibrocytes in tendons have elongated flattened muscle nuclei and are relatively inactive.

Question 16

What is the function of a tendon sheath?

Answer 16

The tendon sheath protects tendons from repeated friction as they traverse over bony surfaces.

Question 17

Which tendons commonly have tendon sheaths?

Answer 17

Long flexor tendons to the fingers commonly have tendon sheaths.

Question 18

What type of nerves innervate skeletal muscles?

Answer 18

Somatic motor nerves innervate skeletal muscles.

Question 19

How do muscles that have the same action on a joint tend to be innervated?

Answer 19

Muscles that have the same action on a joint tend to be innervated by the same nerve.

Question 20

Where does the motor nerve act on the muscle?

Answer 20

The motor nerve acts at the motor endplate, also known as the neuromuscular junction.

Question 21

What are neuromuscular junctions?

Answer 21

Neuromuscular junctions are specialized intercellular connections between a neuron and a skeletal muscle cell.

Question 22

What happens when a neuromuscular junction is stimulated?

Answer 22

Stimulation of a neuromuscular junction causes the myocyte (muscle cell) to contract.

Question 23

What neurotransmitter is released at the neuromuscular junction?

Answer 23

Acetylcholine (ACh) is released at the neuromuscular junction.

Question 24

What happens when acetylcholine is released at the neuromuscular junction?

Answer 24

Acetylcholine opens sodium channels, which elicits an action potential in the muscle cell and causes muscle contraction.

Question 25

Name these muscle morphologies

Answer 25

Question 26

What is the function of an agonist muscle?

Answer 26

The agonist muscle is the prime mover responsible for producing a specific movement.

Question 27

What is the function of an antagonist muscle?

Answer 27

The antagonist muscle opposes the action of the agonist muscle and helps regulate the movement.

Question 28

What is the function of a synergist muscle?

Answer 28

The synergist muscle assists the agonist muscle in producing a movement or helps stabilize the joint.

Question 29

What is the function of a fixator muscle?

Answer 29

The fixator muscle prevents unwanted movement at a joint by stabilizing the bone or joint involved.

Question 30

What happens when a muscle contracts isometrically?

Answer 30

Isometric contraction increases muscle tone but does not produce movement.

Question 31

What is the function of a flexor muscle?

Answer 31

A flexor muscle bends or decreases the angle at a joint.

Question 32

What is the function of an extensor muscle?

Answer 32

An extensor muscle straightens or increases the angle at a joint.

Question 33

What is the function of an abductor muscle?

Answer 33

An abductor muscle moves a body part away from the midline of the body.

Question 34

What is the function of an adductor muscle?

Answer 34

An adductor muscle moves a body part toward the midline of the body.

Question 35

What is the function of a rotator muscle?

Answer 35

A rotator muscle rotates or turns a body part around its axis.

Question 36

What is the difference between hypertrophy and hyperplasia?

Answer 36

Hypertrophy refers to an increase in the size of existing muscle fibers, while hyperplasia refers to an increase in the number of muscle fibers.

Question 37

What is atrophy?

Answer 37

Atrophy refers to the decrease in size or wasting away of muscle tissue, often due to disuse or lack of exercise.

Question 38

How does repair and regeneration differ in cardiac muscle compared to skeletal muscle?

Answer 38

In cardiac muscle, there is no resident stem cell population, so damage to cardiac muscle leads to the formation of collagenous scar tissue. In skeletal muscle, there are satellite cells that can divide and differentiate to form new muscle cells after tissue damage.

Question 39

What are satellite cells?

Answer 39

Satellite cells are myogenic cells located between the sarcolemma (cell membrane) and basement membrane of muscle fibers in skeletal muscle. They have the ability to divide and regenerate muscle tissue after injury.