Muscle Lecture Notes Flashcards

In the context of muscles, __________ connect muscles to bones.

tendons

A __________ is a fluid-filled sac that reduces friction between tissues, such as between tendons and bone.

bursa

The __________ is the attachment point of a muscle to the bone that moves during contraction.

insertion

The __________ is the attachment point of a muscle to the bone that does not move.

origin

The __________ is the thick part of the muscle where the muscle fibers are located.

belly

The __________ is muscle that contributes the most effort in a movement.

agonist/prime mover

A muscle that works in opposition to the agonist is called an __________.

antagonist

The __________ consists of a nerve and the muscle fibers it innervates.

motor unit

During muscle contraction, calcium binds to __________ to expose binding sites on actin.

troponin

The __________ potential is initiated when sodium ions enter the muscle cell, leading to depolarization.

End plate

The __________ period is the time between the stimulus and the actual contraction of the muscle fiber.

Latent

Twitch contraction does not lead to a fully contracted state when stimuli are __________.

Infrequent

The __________ system is anaerobic and provides energy for short bursts of high-intensity activity.

Phosphagen

The __________ fibers are specialized for sustained aerobic activity and are resistant to fatigue.

Slow twitch (Type I)

Fast twitch fibers (Type II) are optimized for __________ and produce quick bursts of power.

Anaerobic bursts

In smooth muscle, __________ contraction is controlled by autonomic nerve fibers.

Involuntary

In the neuromuscular junction, __________ is released from the synaptic knob to stimulate muscle contraction.

Acetylcholine (ACh)

The __________ surrounds the entire muscle.

epimysium

The __________ surrounds individual muscle fascicles.

perimysium

The __________ surrounds each muscle fiber.

endomysium

In muscle movement, a __________ assists the agonist by adding extra force or reducing unnecessary movement.

synergist

A __________ stabilizes the origin of the agonist, allowing for more effective movement by fixing a joint in place.

fixator

The basic contractile unit of a muscle is called a __________.

sarcomere

The __________ is the section within a sarcomere that contains only thin filaments (actin).

I band

The __________ is the portion of the sarcomere where thick filaments (myosin) are present.

A band

The __________ line serves as the central anchor point for thick filaments in the sarcomere.

M line

The __________ are the structural proteins that link neighboring sarcomeres together.

Z discs

During muscle contraction, __________ are pulled closer together by thick filaments, leading to sarcomere shortening.

thin filaments, or actin

During muscle contraction, the heads of __________ grab onto the actin and pull them closer together, leading to sarcomere shortening.

thick filaments, or myosin

__________ is a protein that wraps around actin and blocks myosin binding sites.

tropomyosin

__________ is a protein on actin where calcium binds, which then changes the shape of tropomyosin to expose myosin binding sites.

troponin

The __________ is the junction between a motor neuron and a skeletal muscle fiber.

neuromuscular junction (NMJ)

At the neuromuscular junction, __________ is released from the motor neuron to initiate muscle contraction.

acetylcholine (ACh)

When acetylcholine binds to its receptors, it causes __________ of the muscle fiber membrane.

depolarization

The __________ is the gap between the motor neuron and the muscle fiber at the NMJ.

synaptic cleft

The area of the muscle fiber membrane containing ACh receptors is known as the __________.

motor end plate

Repeated stimulation of the neuromuscular junction may lead to __________ in muscle contraction strength until a threshold is reached.

increased release of ACh

What is the first step of muscle contraction?

The motor neuron releases acetylcholine (ACh) at the neuromuscular junction.

What happens after acetylcholine binds to the muscle fiber membrane?

It causes depolarization of the muscle fiber membrane.

What is released from the sarcoplasmic reticulum during muscle contraction?

Calcium ions (Ca²⁺)

What role does calcium play in muscle contraction?

Calcium binds to troponin, causing a shape change in tropomyosin that exposes myosin binding sites on actin.

What is the result of repeated cycles of myosin binding and pulling?

It leads to sarcomere shortening, resulting in muscle contraction.

What must occur for muscle contraction to stop?

Calcium ions has to be pumped back into the sarcoplasmic reticulum and acetylcholine must be broken down.

When muscle contraction is not occuring, calcium is stored in the __________

sacroplasmic reticulum