Untitled Flashcard Set

Muscles have at least _ attachments and cross at least one joint.

Two

Muscles always _ and get shorter to make movement.

Pull

Muscle fiber striations point to their __ and show direction of pull.

Attachments

A single muscle cell is referred to as a __.

Muscle fiber

A bundle of muscle fibers wrapped in perimysium is called a __.

Fascicle

___ is the connective tissue sheath around a fascicle.

Perimysium

The bundle of fascicles wrapped in epimysium is known as the __.

Muscle belly

___ is the connective tissue sheath around the whole muscle belly.

Epimysium

A __ attaches muscle to bone and is made of tough extensions of perimysium/epimysium.

Tendon

The fixed attachment point that remains stationary during movement is called the __.

Origin

The movable attachment that moves toward the origin is known as the __.

Insertion

The __ is the functional unit of muscle contraction.

Sarcomere

The H-zone is the center region that __ during contraction.

Narrows

The A band (myosin region) does not __ during contraction.

Change length

Myosin heads are known as the __ parts of thick filaments.

Grabber

Myosin pulls the __ filament to shorten the sarcomere.

Actin

A single bead of actin is called __.

G-actin

A strand made by linking many G-actins is referred to as __.

F-actin

Two F-actin strands twisted together form the __.

Actin double helix

The supportive scaffold on actin that blocks myosin-binding sites is called __.

Tropomyosin

The proteins that move tropomyosin to uncover binding sites when bound by Ca²⁺ are referred to as __.

Troponin complex

___ is the trigger that binds troponin and exposes actin sites.

Calcium (Ca²⁺)

The connection formed when a myosin head binds to exposed actin is called a __.

Cross-bridge

The __ is a calcium reservoir wrapped around the myofibrils.

Sarcoplasmic reticulum (SR)

Voltage change causes the SR to release Ca²⁺, initiating __.

Contraction

The __ is when the SR pulls calcium back in, reversing contraction steps.

Ca²⁺ reuptake

Resting membrane potential refers to the outside of the fiber being more positive; inside is relatively __.

Negative

The Na⁺/K⁺ pump sends 3 Na⁺ out and brings 2 K⁺ in to maintain __.

Resting gradients

Sodium (Na⁺) is kept high __ the cell by Na⁺/K⁺ pumps.

Outside

Potassium (K⁺) is kept higher __ the cell by Na⁺/K⁺ pumps.

Inside

The muscle fiber’s cell membrane is known as the __.

Sarcolemma

___ are tunnels in the sarcolemma that carry the electrical signal to the SR.

T-tubules

The nerve cell that stimulates the muscle fiber is referred to as a __.

Motor neuron

The main neurotransmitter released by the motor neuron at the neuromuscular junction is __.

Acetylcholine (ACh)

ACh receptors are ligand-gated Na⁺ channels that open when __ binds.

ACh

___ occurs when the inside of the fiber becomes more positive than the outside.

Depolarization

The wave of depolarization traveling down T-tubules is known as an __.

Action potential

The enzyme that breaks down ACh so the signal stops is called __.

Acetylcholinesterase (AChE)

Repolarization restores the normal Na⁺/K⁺ balance and returns __ to the SR.

Ca²⁺

With binding sites open, myosin pulls actin, causing __ and muscle contraction.

Sarcomeres to shorten

Tendon fibers are interwoven with muscle sheaths, resulting in very __ attachment.

Strong

The orientation of striations indicates the __ of a muscle when it shortens.

Direction of pull

The contraction control summary includes nerve ACh, Na⁺ influx, T-tubule signal, and __.

SR Ca²⁺ release.