Muscle Tissue Types, Structure, and Function: A Comprehensive Overview

What is muscle tissue?

Alternating contraction and relaxation of cells; chemical energy changed into mechanical energy

What are the 3 types of muscle?

Skeletal, cardiac, smooth

Which muscle is primarily focused on?

Skeletal muscle

What are the functions of skeletal muscle?

Movement (reflex and voluntary), posture, support soft tissues, guard entrances and exits, maintain body temperature, store nutrient reserves

What is muscle tone?

Low levels of contractile activity

How do muscles maintain body temperature?

Produce heat by catabolism and shivering

What do muscles store?

Amino acids

What is the origin of a muscle?

Bone that does not move (usually proximal)

What is the insertion of a muscle?

Movable bone

What is the belly of a muscle?

Fleshy portion between attachment sites

What is a prime mover (agonist)?

Contracts to cause the desired action

What is an antagonist?

Stretches and yields to the prime mover

What is a synergist?

Stabilizes nearby joints

What is a fixator?

Stabilizes the origin of the prime mover

How are muscles named?

Direction, size, shape, action, number of origins, location

What does orbicularis oculi do?

Closes the eye

What does orbicularis oris do?

Puckers the mouth

What do masseter and temporalis do?

Elevate the mandible

What does sternocleidomastoid do?

Flexes neck and rotates head

What is epimysium?

Surrounds the whole muscle

What is perimysium?

Surrounds fascicles

What is endomysium?

Surrounds individual muscle fibers

What is a tendon?

Connects muscle to bone

What is an aponeurosis?

Connects muscle to muscle

What are muscle fibers?

Specialized skeletal muscle cells

Why are muscle fibers multinucleated?

Formed from fusion of myoblasts

Can muscle cells divide?

No

How do muscles grow?

Enlargement (hypertrophy)

What is the sarcolemma?

Plasma membrane

What is the sarcoplasm?

Cytoplasm

What are T tubules?

Carry impulses into the cell

What is the sarcoplasmic reticulum?

Stores calcium

What is a triad?

T tubule and two sarcoplasmic reticulum sacs

What are thin filaments made of?

Actin, troponin, tropomyosin

What are thick filaments made of?

Myosin

What are cross bridges?

Myosin heads

What is a sarcomere?

Functional unit of muscle

What is the I band?

Thin filaments only

What is the A band?

Thick and thin overlap

What is the H zone?

Thick filaments only

What is the Z disc?

Boundary of sarcomere

What is a motor unit?

Motor neuron and the muscle fibers it stimulates

What neurotransmitter is used for muscle contraction?

Acetylcholine

What is the all-or-none principle?

Muscle fiber contracts fully or not at all

What starts muscle contraction?

Nerve impulse releases acetylcholine

What ion is released for muscle contraction?

Calcium (Ca2+)

What does calcium bind to during contraction?

Troponin

What model explains muscle contraction?

Sliding filament model

What are the 4 steps of muscle contraction?

ATP hydrolysis, crossbridge formation, power stroke, detachment

What stops muscle contraction?

Acetylcholine breakdown and calcium pumped back into SR

What is rigor mortis?

Muscle rigidity after death due to no ATP

What is isotonic contraction?

Muscle changes length

What is concentric contraction?

Muscle shortens

What is eccentric contraction?

Muscle lengthens

What is isometric contraction?

Muscle does not change length

What is the immediate energy source for muscles?

ATP

What is the short-term energy source for muscles?

Creatine phosphate

What is anaerobic energy?

Glycolysis producing lactic acid

What is long-term energy for muscles?

Aerobic respiration

What is muscle fatigue?

Inability to contract

What causes muscle fatigue?

Low ATP, glycogen depletion, lactic acid buildup

What are slow-twitch fibers?

Red, endurance, fatigue resistant

What are fast-twitch A fibers?

Intermediate, fast and somewhat fatigue resistant

What are fast-twitch B fibers?

White, powerful, fatigue quickly

What is atrophy?

Muscle wasting

What is hypertrophy?

Increase in muscle size

What are cardiac muscle characteristics?

Striated, involuntary, single nucleus, intercalated discs

What is special about cardiac muscle?

Autorhythmic

What are smooth muscle characteristics?

Non-striated, involuntary, spindle-shaped

What protein regulates smooth muscle?

Calmodulin

What is a spasm?

Involuntary contraction

What is a cramp?

Painful spasm

What is paralysis?

Loss of movement