A&P -Muscular System

3 functions of muscles

movement, heat production, posture

4 characteristics of muscle tissue

1. Excitability

2. Contractility

3. Extensibility

4. Elasticity

excitability

ability to receive and respond to stimuli

contractility

ability to shorten forcibly when stimulated

extensibility

the ability to be stretched or extended

elasticity

the ability to bounce back after being stretched or shortened

peristalsis

the process of wave-like contractions of smooth

3 types of muscle tissue

skeletal, cardiac, smooth

endomysium

Surrounds individual muscle fibers

fascicle

bundle of muscle fibers

perimysium

surrounds fascicles

epimysium

surrounds entire muscle

fascia

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle

sarcolemma

membrane of a muscle fiber/cell

sarcoplasm

cytoplasm of a muscle fiber/cell

T tubules

transverse tubules, network of channels through cell to activate contraction

sarcoplasmic reticulum

specialized endoplasmic reticulum of muscle cells, stores calcium

sarcomere

contractile unit of a muscle fiber

myosin

thick filament

actin

thin filaments

myosin and actin

contractile and motor proteins in sarcomere

Z line

A dark thin protein band to which actin filaments are attached, marks the boundaries between sarcomeres

Flexors

decrease angle of joint

Extensor

increases joint angle

Abductor

moves bone away from midline

Adductor

Moves bone closer to midline

Rotator

contracts to provide stability, allowing rotation

Scapular Stabilizer

controls movement of scapula to stabilize shoulder joint

Evertor

turns the sole of the foot outward away from midline

Invertor

turns the sole of the foot inward toward midline

ligament

Connects bone to bone

tendon

Connects muscle to bone

sliding filament model

states that the thick and thin filaments slide past each other so that their degree of overlap increases

motor unit

a single motor neuron and all the muscle fibers it innervates (supplies), the more motor units stimulated - the stronger the contraction

all-or-none response

a neuron's reaction of either firing (with a full-strength response) or not firing

recruitment

increased intensity of stimulation can activate other surrounding motor units

Why to rub a muscle cramp

1. break cross bridges

2. increase blood flow

3. decrease pain sensitivity

4. disperse lactic acid

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle fiber

synaptic cleft

the narrow gap that separates the neuron from the muscle cell.

Acetylcholine

neurotransmitter that triggers muscle contraction

cross bridges

myosin fiber head, which connects to the thin actin filaments during a contraction, acting like oars to pull actin inward

troponin and tropomyosin

Contraction Inhibiting Proteins that are attached to actin

twitch muscle contraction

single, quick cycle of contraction and relaxation

sustained muscle contraction, tetanus

a long muscular contraction resulting from a rapid series of nerve impulses

repeated stimulation contraction, treppe

Phenomenon in which each successive twitch contracts more forcefully than the previous one

tonus

natural and continuous, slight contraction of a muscle; especially in smooth muscle

3 periods of muscle contraction

latent, contraction, relaxation

latent period

time between stimulus and contraction

contraction period

time between the beginning of muscle shortening and the development of peak tension

refractory period

the time following contraction when a new stimulus cannot be initiated