Unit 6 Muscular System

connect muscle to bone and aid in body movement

skeletal muscle

Heart muscles only, enervated by autonomic nervous system

cardiac muscle

Located in vessels/organs, enervated by autonomic nervous, affected by hormones and neurotransmitters

Smooth muscle

Five key functions of muscle tissue

• provides movement of the body

• Stabilize body position/posture

• Regulate volume in organs

• Moving substances within body

• Production of heat

Four properties of muscle tissue

• electrical excitability

• Contractually

• Extensibility

• Elasticity

Steps of neuromuscular junction

• Brain sends an action potential towards a muscle

• Impulse passes through multiple neurons until it arrives at the muscle

• Synaptic vesicles filled with ACH arrive at axon terminals

• Vesicles release chemicals via exocytosis

• Chemicals will travel across synaptic draft

• Receive at motor end plate

• Chemicals travel down sarcolemma to the t-tubules

• Calcium travels to actin and frees myosin head binding sites

• Myosin attaches to troponin to form a cross bridge

• Myosin performs a power stroke

• Myosin head releases from troponin after contraction

what are the 3 sources of ATP

• creatine phosphate

• Anaerobic cellular respiration

• Aerobic cellular respiration

Smallest in diameter, fewest myofibrils, least powerful of muscle fibers, dark red in appearance (heavy in myoglobin), heavy on mitochondria/ATP

Slow oxidative fibers

Intermediate in diameter, large amounts of myoglobin (pink in appearance), generates ATP through aerobic respiration, more power contractions

Fast oxidative fibers

Largest in diameter, white in appearance, most myofibrils, low myoglobin, most powerful contractions, fatigues most quickly, uses glucose to produce ATP

Fast glycolytic fibers

Groups of muscle fibers that allow stimulation of multiple muscles

Motor units

Total tension a muscle fiber can produce depends on

Frequency of stimulation

Activation of voluntary motor units, brings blood flow to muscle, generates an impulse but lingers

Muscle tone

Oxygen storage for muscle tissue, fibers are redder if there is more myoglobin

Myoglobin

The attachment site where the muscle fibers connect to a fixed/less moveable bone

Origin

The point where the muscle attaches to a bone/structure that moves when the muscle contracts

Insertion

How are muscles named

Location, shape, relative size, function, direction of fibers, number of origins, location of attachments

Study of muscles

Myology

Muscle tension without shortening the muscle

Isometric contraction

Muscle tension is constant and also shortens

Isotonic contraction

Flat connective tissue that functions as a tendon

Aponeurosis

Stimulates skeletal muscle

Somatic motor neurons

Branch out to enervate different muscle fibers, where the nerve and muscle meet to exchange the signal at neuromuscular junction

Axon terminal

Contractile proteins

Actin and myosin

Membrane of the muscle fiber

Sarcolemma

Plasma of a muscle cell that stores ATP/energy

Sarcoplasm

Contains/transports calcium within cell

Sarcoplasmic reticulum

Thick filament

Myosin

Thin filament

Actin

Action only portion of a sarcomere that gets smaller with contraction

I band

Midline of a sarcomere, myosin only crosses this line

M line

Area of myosin only that gets smaller with contraction

H zone

Area of overlap between actin and myosin that gets bigger during contraction

A band

Gap where the neuron meets the muscle

Synapse

Divides the two cells from each other

Synaptic cleft

Chamber that contains the neurotransmitter

Synaptic vesicle

Most easily seen contraction, 20-30x a second

Unfused tetanus

80-100 stimuli per second

Fused tetanus

Muscle shortens pulling on another structure to produce movement

Concentric isotonic contractions

Length of the muscle is increasing during contraction, controlled movement against tension

Eccentric isotonic contraction

Muscle in charge of the major force in the movement

Prime mover

Opposing muscle working in reverse

Antagonist

Supporting muscles that aid prime movers and help add force

Synergists

Specific synergists to support origin site of the muscle for stabilization

Fixator

sternocleidomastoid

tenses skin of neck

platysma

closes and protrudes lips

orbicularis oris

compresses cheek, holds food between teeth during chewing

buccinator

Closes eyelids; used in blinking, winking, and squinting

orbicular oculi

retracts and elevates corner of mouth

zygomaticus

Elevates and retracts mandible; assists in side to side movement of mandible

temporalis

elevates mandible and closes jaw

masseter

elevates and adducts scapula

levator scapulae

pulls scapula anteriorly and downward

serratus anterior

chest muscle

pectoralis major

insertion: coracoid process of scapula

pectoralis minor

extends, adducts, and medially rotates arm

latissimus dorsi

shoulder

deltoid

• origin: scapula

• action: flexes forearm at elbow

biceps brachii

• origin: humerus

• insertion: radius

• action: flexes forearm at elbow

brachioradialis

• origin: humerus

• insertion: ulna

• action: extends forearm at elbow

triceps brachii

gluteus medius

gluteus maximus

gluteus minimus

back of knee/calf muscle

gastrocnemius

• origin: tibia

• insertion: tarsal bone

• action: dorsiflexion

tibialis anterior

• origin: pubic bone

• insertion: femur

• action: adducts

adductor longus

gracilis

bicep femoris

semitendinosus

semimembranosus

rectus femoris

vastus lateralis

vastus medialus

action: plantar flexion

fibularis longus

sartorius