Muscle Functions
This function of muscle tissue helps maintain upright posture and stabilizes joints.
Posture (stabilizing body positions).
This characteristic is the ability of muscle tissue to return to its resting length after being stretched.
Elasticity.
Which muscle type is striated, voluntary, and attached to bones by tendons?
Skeletal
During contraction myosin heads attach to active sites on this thin filament protein.
Actin.
The muscle that is the prime mover for forearm flexion (anterior upper arm) is the ____.
Biceps brachii.
Name the muscle function responsible for producing heat to help maintain body temperature.
Thermogenesis (heat production).
The ability of muscle tissue to respond to a stimulus (such as a nerve impulse) is called what?
Excitability (irritability).
Name the muscle type found in the walls of hollow internal organs that is non-striated and involuntary.
smooth
Name the two regulatory proteins associated with actin that control cross-bridge formation
Tropomyosin and troponin.
Identify the muscle that plantar flexes the foot (posterior lower leg).
Gastrocnemius.
Which muscle tissue function moves the skeletal levers of the body to produce locomotion and other movements?
Motion/movement by moving skeletal levers.
This property describes a muscle's ability to be elongated or stretched.
Extensibility.
This muscle type forms the myocardium, has branching fibers and intercalated disks. Name it.
Cardiac
At the neuromuscular junction, this neurotransmitter is released from synaptic vesicles to depolarize the muscle membrane.
Acetylcholine (ACh).
Which muscle abducts the arm and covers the shoulder?
Deltoid.
Muscles that control the volume of hollow organs (like the bladder or stomach) perform this function.
Regulation of organ volume
The characteristic that allows muscle fibers to actively shorten and thicken to produce movement is called ____.
Contractility.
Give two microscopic differences between skeletal and smooth muscle.
Skeletal = striated, multinucleated; Smooth = non-striated, single central nucleus, tapered fibers.
Put these steps in order (write numbers 1–5): A. Ca++ binds to troponin; B. Action potential travels down T-tubules; C. Myosin heads perform power stroke; D. Acetylcholine is released into synaptic cleft; E. Sarcoplasmic reticulum releases Ca++.
D (ACh release), B (AP down T-tubules), E (SR releases Ca++), A (Ca++ binds troponin), C (power stroke).
Define agonist and antagonist and give an example pair from the list (biceps brachii and triceps brachii).
Agonist = prime mover (biceps in elbow flexion); Antagonist = performs opposite action (triceps during elbow flexion).
List two ways skeletal muscles protect internal organs.
skeletal muscles absorb shock for internal organs (abdominal wall, thoracic muscles) and provide a tough layer over organs (e.g., abdominal muscles and gluteus) — accept two reasonable protective roles.
Provide a one-sentence example that shows how excitability and contractility work together during a voluntary movement
A motor neuron sends a nerve impulse (excitability) to a muscle fiber, which then shortens and produces movement (contractility)
For each muscle type (skeletal, smooth, cardiac), list its primary control (voluntary/involuntary) and one unique structural feature.
Skeletal: voluntary, multinucleated/striated; Smooth: involuntary, non-striated/tapered single nucleus; Cardiac: involuntary, striated, branching fibers, intercalated disks.
Explain (2–3 sentences, 10th-grade level) why ATP is necessary for both the power stroke and for detachment of myosin heads from actin.
ATP provides the energy that myosin needs to produce the power stroke (by being split into ADP + P); then a new ATP molecule binds to myosin so it can detach from actin and reset for another cycle.
For the following muscles, write their primary action (one-liners): pectoralis major, latissimus dorsi, diaphragm, gluteus maximus, sternocleidomastoid.
pectoralis major — adducts the arm; latissimus dorsi — extends/adducts the arm (pulls shoulder down/back); diaphragm — contracts to increase thoracic volume for inhalation; gluteus maximus — extends/hyperextends the thigh; sternocleidomastoid — flexes/rotates the head and neck.