3 - Muscle and Movement

Question 1

What are the four major tissue types in the body

Answer 1

Muscle tissue

Connective tissue

Epithelial tissue

Nervous tissue

Question 2

What are the three types of muscle tissue

Answer 2

Skeletal

Cardiac

Smooth muscle

Question 3

Where is skeletal muscle found

Answer 3

Attached to bones and some facial muscles connected to the skin

Question 4

Where is cardiac muscle found

Answer 4

In the walls of the heart

Question 5

Where is smooth muscle found

Answer 5

In the walls of hollow visceral organs (excluding the heart), and in multiunit muscle such as the intrinsic eye muscles, airways, and large arteries

Question 6

What is the structure of skeletal muscle cells

Answer 6

Long, cylindrical, multinucleated cells with visible striations

Question 7

What is the structure of cardiac muscle cells

Answer 7

Branching chains of cells, usually uni- or binucleated, with striations

Question 8

What is the structure of smooth muscle cells

Answer 8

Spindle-shaped (fusiform), uninucleate, and lack striations

Question 9

Do skeletal muscle cells have gap junctions

Answer 9

No

Question 10

Do cardiac muscle cells have gap junction

Answer 10

Yes, located at intercalated discs

Question 11

Do smooth muscle cells have gap junctions

Answer 11

Yes, in single unit smooth muscle

Question 12

Do skeletal muscle cells have individual neuromuscular junctions

Answer 12

Yes

Question 13

Do cardiac muscle cells have individual neuromuscular junctions

Answer 13

No

Question 14

Do smooth muscle cells have neuromuscular junctions

Answer 14

No, in single unit smooth muscle

Yes, in multiunit smooth muscle

Question 15

How is skeletal muscle contraction regulated

Answer 15

Voluntarily controlled via axon terminals of the somatic nervous system

Question 16

How is cardiac muscle contraction regulated

Answer 16

Involuntarily regulated by an intrinsic conduction system, autonomic nervous system, hormones, and stretch

Question 17

How is smooth muscle contraction regulated

Answer 17

Involuntarily regulated by autonomic nerves, hormones, local chemical signals, and stretch

Question 18

What are the three main ways to classify muscle types

Answer 18

By striations, control (voluntary/involuntary), and location (situation)

Question 19

What is the function of cardiac muscle

Answer 19

Found in the heart, responsible for rhythmic, repeated contractions to pump blood

Question 20

How is smooth muscle controlled

Answer 20

Phasic smooth muscle: via action potentials (e.g. peristalsis in the GI tract)

Tonic smooth muscle: via electrical, chemical, or mechanical signals (e.g. in blood vessels)

Question 21

What is peristalsis and which muscle type performs it

Answer 21

Wave-like contractions in the digestive tract using phasic smooth muscle

Question 22

What controls skeletal muscle contraction

Answer 22

Motor units—groups of motor neurons and the muscle fibres they innervate

Question 23

What are slow-twitch muscle fibres

Answer 23

Use oxygen for fuel, fire slowly, support endurance activities like long-distance running

Question 24

What are fast-twitch muscle fibres

Answer 24

Use anaerobic metabolism, fire rapidly, suited for short bursts of strength or speed, but fatigue quickly

Question 25

What are skeletal muscle cells also called

Answer 25

Myocytes or muscle fibres—long, cylindrical cells with actin and myosin filament

Question 26

How are myocytes structurally arranged

Answer 26

Aligned along a single axis for contraction

Question 27

Neuromuscular Transmission (Steps)

Answer 27

1. Arrival of action potential 2. Depolarisation of presynaptic membrane and opening of Ca2+ voltage gated channels 3. Increase intracellular Ca2+ leads to release of Ach from synaptic vesicles 4. Binding of Ach to its receptors on ligand-gated cation channels 5. Activation of Ach gated ion channels in the end plate membrane 6. Increase of Na+ and k+ conductance via ligand gated non-selective cation channels leads to the generation of end plate potential (EPP) 7. Generation of the EPP leads to generation of action potential of electrically excitable skeletal sarcolemma

Question 28

Sliding Filament Theory

Answer 28

1. Rise of intracellular Ca2+ 2. Binding of Ca2+ to troponin moves tropomyosin away from myosin binding sites on actin 3. Cross bridge formation 4. Power stroke 5. Cross bridge detachment 6. Reactivation of myosin head 7. Repositioning of energised myosin head

Question 29

Name the main contractile proteins in muscle

Answer 29

Myosin (thick filaments) and actin (thin filaments)

Question 30

What do the regulatory proteins tropomyosin and troponin do

Answer 30

Tropomyosin: Blocks myosin binding sites in the absence of Ca²⁺ Troponin: Binds Ca²⁺ and shifts tropomyosin to expose binding sites

Question 31

What are the key structural proteins in skeletal muscle

Answer 31

Titin (elasticity), nebulin, dystrophin, and desmin

Question 32

What processes require ATP in skeletal muscle

Answer 32

Myosin cross-bridge cycling, Ca²⁺ pumping into the SER, Na⁺/K⁺ pump

Question 33

What are the sources of ATP for muscle contraction (and durations)

Answer 33

1. Preformed ATP (1–2 seconds) 2. Phosphocreatine (4–6 seconds) 3. Glycolysis (approx. 1 minute) 4. Oxidative phosphorylation (long term, 95% of ATP)

Question 34

What is an isometric contraction

Answer 34

Muscle tension increases, but fibre length stays the same (no movement)

Question 35

What is an isotonic contraction

Answer 35

Muscle tension remains constant, but fibre length changes (movement occurs)

Question 36

How is force transferred in the musculoskeletal system

Answer 36

Muscles act through tendons and work in antagonistic pairs—one contracts, the other relaxes

Question 37

Smooth Muscle Contraction Mechnism

Answer 37

1. Intraceilar Ca2+ comes in 2. Ca2+ binds to calmodullin 3. Ca2+ calmodulin complex binds to myosin light-chain kinase 4. Myosin light-chain kinase uses ATP to phosphorus ate myosin cross bridges 5. Phosphorylated cross bridges bind to action filaments 6. Cross-bridge cycle produces tension and shortening