Muscles

Question 1

What are the Basic Types of Muscle Tissue?

Answer 1

Skeletal muscle, cardiac muscle, and smooth muscle.

Question 2

How is muscle tissue organised hierarchically

Answer 2

Muscle tissue is organized into muscle fascicles, composed of muscle fibers, which, in turn, are made up of myofibrils containing sarcomeres.

Question 3

What is the detailed structure of skeletal muscle fibers?

Answer 3

Skeletal muscle fibers are long, multinucleated cells containing myofibrils responsible for muscle contraction.

Question 4

What is the functional unit of muscle contraction, and what composes it?

Answer 4

The sarcomere is the functional unit, consisting of thick myosin filaments and thin actin filaments.

Question 5

What are actin and myosin, and where are they found in muscle cells?

Answer 5

Actin and myosin are protein filaments found in myofibrils of muscle cells, playing crucial roles in the contraction process.

Question 6

How are actin and myosin arranged in striated muscles during contraction?

Answer 6

Actin and myosin filaments overlap in a sliding mechanism, resulting in muscle shortening and striations.

Question 7

What characterises cardiac tissue?

Answer 7

Cardiac tissue is striated and involuntary, forming the heart walls and composed of interconnected, branching cells called cardiomyocytes.

Question 8

What unique feature contributes to coordinated contraction in cardiac tissue?

Answer 8

Intercalated discs, containing gap junctions, facilitate rapid electrical signaling and synchronized contraction among cardiac muscle cells.

Question 9

How does cardiac tissue differ from skeletal muscle in terms of contractions?

Answer 9

Unlike skeletal muscle, cardiac muscle exhibits rhythmic and involuntary contractions, crucial for pumping blood throughout the circulatory system.

Question 10

What characterises smooth muscle tissue?

Answer 10

Smooth muscle tissue lacks striations
Short (~100mm)
Slow contractions (seconds/minutes) that are myogenic.
Involuntary
Found in various organs - digestive tract, blood vessels, and respiratory passages.

Question 11

How do smooth muscle cells differ in shape compared to skeletal muscle cells?

Answer 11

Smooth muscle cells are spindle-shaped, with a single nucleus, contrasting with the multinucleated, elongated shape of skeletal muscle cells.

Question 12

What allows smooth muscle tissue to adapt to stretching and distension?

Answer 12

The ability of smooth muscle tissue to contract in response to stretching, known as plasticity, enables it to accommodate changes in organ volume and function.

Question 13

What defines skeletal muscle tissue?

Answer 13

Skeletal muscle is a type of striated muscle under voluntary control, responsible for body movement, and attached to bones by tendons.

Question 14

How are skeletal muscles organised within the body?

Answer 14

Skeletal muscles are organised in antagonistic pairs, contracting and relaxing to produce coordinated movement around joints.

Question 15

How is skeletal muscle innervated, and what controls its contraction?

Answer 15

Skeletal muscles are innervated by motor neurons, and contraction is controlled by the release of acetylcholine at neuromuscular junctions, triggering an action potential in the muscle fibres.

Question 16

Describe cardiac contraction

Answer 16

Contraction is myogenic (self-generated by the muscle cells) – cells are autorhythmic (they generate their own rhythmic contractions without any external input or control).

Moderate speed of contraction.

Question 17

What influences the contraction of the heart?

Answer 17

Rhythm of contraction influenced by pacemaker region of the heart - the Sino-Atrial Node (SA Node)

SA Node can be influenced by Autonomic Nervous System (sympathetic and parasympathetic nervous systems) and hormones (eg Adrenaline) to increase or decrease rate and force of contraction

Question 18

What can happen is cardiac cells become uncoupled?

Answer 18

Arrhythmias or fibrillation

Question 19

What structural changes occur in sarcomeres during muscle contraction?

Answer 19

Sarcomeres shorten as actin filaments slide over myosin filaments, causing the muscle to contract.

Question 20

Describe the formation of crossbridges between myosin and actin during muscle contraction.

Answer 20

Myosin heads bind to actin, forming crossbridges, initiating the contraction process.

Question 21

What is the crossbridge cycle in muscle contraction?

Answer 21

The cycle involves myosin binding to actin, power stroke generation, release, and resetting for the next contraction.

Question 22

How is ATP utilised during the crossbridge cycle?

Answer 22

ATP hydrolysis provides energy for myosin to detach from actin, allowing muscle relaxation.

Question 23

Explain the sliding filament theory of muscle contraction.

Answer 23

Actin filaments slide over myosin filaments, causing sarcomeres to shorten and muscle contraction.

Question 24

What roles do Troponin and Tropomyosin play in muscle contraction?

Answer 24

Troponin and Tropomyosin regulate the exposure of binding sites on actin, controlling the interaction with myosin.

Question 25

How do calcium ions contribute to muscle contraction?

Answer 25

Calcium ions released from the sarcoplasmic reticulum bind to Troponin, leading to the exposure of myosin-binding sites on actin, initiating muscle contraction.

Question 26

How does Troponin differ from Tropomyosin in muscle physiology?

Answer 26

Troponin is a regulatory protein that binds calcium and facilitates muscle contraction

Tropomyosin blocks myosin-binding sites on actin, preventing contraction in the absence of calcium.

Question 27

Are there any structural differences between Troponin and Tropomyosin?

Answer 27

Yes!

Troponin is a complex of three subunits

Tropomyosin is a long, filamentous protein that winds along the actin filament.

Question 28

What is the role of transverse tubules (t-tubules) in muscle contraction?

Answer 28

T-tubules transmit action potentials deep into muscle fibers, ensuring synchronous calcium release and uniform muscle contraction.

Question 29

Describe the changes in muscle force (tension) during a single muscle twitch.

Answer 29

Muscle force rises rapidly during the contraction phase, peaks during the twitch, and then declines during relaxation.

Question 30

How do repeated stimuli affect muscle force (tension)?

Answer 30

Repeated stimuli result in summation, leading to increased muscle force, with consecutive twitches merging into a sustained contraction.

Question 31

Differentiate between fused and unfused tetanic contractions.

Answer 31

Fused tetanic contractions are continuous, with no relaxation between stimuli

Unfused tetanic contractions involve partial relaxation.

Question 32

Explain the length-tension relationship in muscle physiology.

Answer 32

The length-tension relationship describes how muscle force varies with the length of sarcomeres, optimising force production at an optimal length.

Question 33

What is the arrangement of sarcomeres that underpins the length-tension relationship?

Answer 33

Sarcomeres aligned at an optimal length maximise the overlap of actin and myosin filaments, enhancing cross-bridge formation and muscle force production.