Muscle Tissue and Function

What are the three types of muscle tissue?

Skeletal, cardiac, smooth

Which muscle tissue is voluntary?

Skeletal

Which muscle tissues are involuntary?

Cardiac and smooth

Which muscle tissue is striated?

Skeletal and cardiac

Which muscle tissue is nonstriated?

Smooth

Which muscle tissue has intercalated discs?

Cardiac

Which muscle tissue is spindle-shaped?

Smooth

What is the main function of muscle tissue?

Produce movement

What are other functions of muscle?

Maintain posture and generate heat

What is thermogenesis?

Heat production by muscle activity

What does excitability mean in muscle tissue?

Respond to stimuli

What does contractility mean in muscle tissue?

Shorten forcibly

What does extensibility mean in muscle tissue?

Stretch

What does elasticity mean in muscle tissue?

Recoil after stretch

What is a muscle fiber?

A muscle cell

Are skeletal muscle fibers multinucleated?

Yes

Where are nuclei located in skeletal muscle?

Peripheral

What is the typical location of cardiac muscle nuclei?

Usually one central nucleus

What is the typical location of smooth muscle nuclei?

Single central nucleus

What is the sarcolemma?

Cell membrane of muscle fiber

What is sarcoplasm?

Cytoplasm

What is myoglobin?

Oxygen-binding protein in muscle

Why is myoglobin important?

Stores oxygen for contraction

What are myofibrils?

Contractile rods in muscle cell

What are myofilaments?

Actin and myosin filaments

What is a thin filament?

Actin

What is a thick filament?

Myosin

What is a sarcomere?

Functional unit of contraction

What are the boundaries of a sarcomere?

Z discs

What does the Z disc do?

Anchors thin filaments

What is the I band?

Thin filaments only

What is the A band?

Length of thick filaments

What is the H zone?

Thick only region

What is the M line?

Middle of sarcomere

What happens to the sarcomere during contraction?

Shortens

What happens to the I band during contraction?

Shortens

What happens to the H zone during contraction?

Disappears

What happens to the A band during contraction?

No change

What is the sliding filament theory?

Actin slides over myosin

What shortens during contraction?

Sarcomere, not filaments

What is a cross bridge?

Myosin head binds actin

What is a power stroke?

Myosin pulls actin inward

What causes detachment of myosin?

ATP binding

What re-***** the myosin head?

ATP hydrolysis

What blocks actin binding sites?

Tropomyosin

What exposes binding sites on actin?

Calcium binds troponin

What is the role of calcium in contraction?

Allows cross-bridge formation

What is the neuromuscular junction?

Connection between neuron and muscle

What neurotransmitter is at the NMJ?

Acetylcholine (ACh)

What does ACh bind to?

Receptors on sarcolemma

What happens after ACh binds?

Depolarization → contraction

What enzyme removes ACh?

Acetylcholinesterase

What happens if ACh is not broken down?

Continuous contraction

What is a motor unit?

One neuron + muscle fibers

What is a small motor unit?

Precise movement

What is a large motor unit?

Powerful movement

What is a muscle twitch?

Single contraction response

What are the phases of a twitch?

Latent, contraction, relaxation

What is the latent period?

Delay before contraction

What happens during the contraction phase?

Muscle shortens

What happens during the relaxation phase?

Muscle returns to rest

What is summation?

Increased force with repeated stimuli

What is tetanus?

Sustained contraction without relaxation

What is incomplete tetanus?

Partial relaxation between stimuli

What is complete tetanus?

No relaxation

What is muscle tone?

Constant low-level contraction

What is fatigue?

Loss of contraction ability

What are the causes of fatigue?

Lack of ATP, ion imbalance, lactic acid

What is the immediate energy source for muscles?

Stored ATP

What is short-term energy for muscles?

Creatine phosphate

What is long-term energy for muscles?

Aerobic respiration

What does creatine phosphate do?

Regenerates ATP quickly

What is oxygen debt?

Oxygen needed after exercise

What causes burning in muscles?

Lactic acid buildup

What is hypertrophy?

Increase in muscle size

What is atrophy?

Decrease in muscle size

What causes hypertrophy?

Exercise

What causes atrophy?

Disuse

Where is smooth muscle located?

Organs and vessels

What is the function of smooth muscle?

Moves substances

What is the contraction of smooth muscle like?

Slow and sustained

Where is cardiac muscle located?

Heart

What is the function of cardiac muscle?

Pump blood

What is cardiac contraction like?

Rhythmic and involuntary

What prevents cardiac fatigue?

Continuous oxygen supply

What are intercalated discs?

Cell junctions in cardiac muscle

What is the function of intercalated discs?

Coordinate contraction

What is rigor mortis?

Stiffening after death

What causes rigor mortis?

No ATP → cannot detach cross bridges

What would happen without calcium?

No contraction

What would happen without ATP?

Muscle stays contracted

Which band disappears first in strong contraction?

H zone

Which band never changes length?

A band

If calcium levels drop, what happens?

Contraction stops

If ATP increases, what happens?

More cross-bridge cycling

Why are skeletal muscles striated?

Organized sarcomeres

Why is smooth muscle not striated?

No sarcomere arrangement

Which muscle type can regenerate best?

Smooth muscle

Which muscle type has the least regeneration?

Cardiac

True or False: Muscle fibers divide frequently.

False