Anatomy Digestive/Muscle

Fascicle

A number of muscle fibers together.

Muscle

A number of fascicles bound together.

Myofibrils

Individual muscle fibers can be broken down into these.

Sarcomeres

Myofibrils can be further broken down into these.

Myofilaments

Sarcomeres can in turn be broken down into these.

Actin

The thin protein within myofilaments.

Myosin

The thick protein within myofilaments.

Z-line

The zigzag line that runs down the actin chains.

Muscle contraction

Muscles can only contract or relax.

Functions of muscles

Movement, stability, heat production, and control of body openings.

Insertion

The attachment to the more movable bone.

Skeletal muscle

Striated, tires easily, voluntary; found attached to bones.

Cardiac muscle

Striated, tireless, involuntary; found in the heart.

Smooth muscle

Non-striated, tireless, involuntary; found in walls of hollow organs.

Tendons

Connect bone to muscles.

Motor unit

One neuron and all of the skeletal muscle cells it stimulates.

Neuromuscular junction

The spot where a nerve inserts into the muscle.

Acetylcholine (ACh)

The neurotransmitter released at the neuromuscular junction.

Action potential

The electrical pulse that flows through a muscle.

Calcium and sodium ions

The ions that are most important in muscle contraction.

Muscle fatigue

When a muscle is unable to contract even though being stimulated.

Isotonic contraction

Type of contraction where muscle filaments slide and the muscle shortens.

Isometric contraction

Type of contraction where muscles don’t shorten.

Muscle tone

Continuous partial contraction of the body.

Muscle spasticity

Continuous contraction of the muscles.

Exercise regime components

Should contain aerobic, anaerobic, and flexibility activities.

Aerobic exercises

Examples include jogging, biking, swimming.

Orbicularis oris

An example of a circular muscle.

Pennate muscle

A muscle that feathers.

Muscle pairs

Muscles always work in pairs.

Agonist

The muscle in a pair with the major responsibility.

Antagonist

The opposite muscle to the agonist.

Flexion

Decreases the angle of a joint.

Extension

Increases the angle of a joint.

Abduction

Moving away from the midline.

Adduction

Moving towards the midline.

Dorsiflexion

Bringing the foot up to the shin.

Plantar flexion

Pointing toes down.

Rotation

Movement around the longitudinal axis.

Inversion

Soles of feet face medially.

Eversion

Soles of feet face laterally.

Quickening

The first movements of the fetus that the mother can feel.

Atrophy

The withering away of muscles.

Lactic acid build-up

Causes muscle cells to become stiff.

Steroids

Derivatives of testosterone or cholesterol.

Muscular dystrophy

A genetic disease characterized by muscle tears that will not heal.

Rigor mortis

Occurs when actin and myosin don’t let go after sliding together.

Strained muscle

When a muscle is overstretched and becomes swollen.

Torn muscle

A worse version of a strained muscle.

Shin splints

Caused by either a stress fracture or tendonitis.

Cramps

A spasm in a muscle.

Tension headaches

Sustained contractions of the head and neck muscles may lead to these.

3rd-degree sprain

The worst type of sprain or strain.

Muscle naming criteria

Can include number of heads, shape, function, and attachment points.

Blood vessels constrict

When muscles are cold, causing less oxygen to reach the muscles.

Superior

Anatomy term meaning toward the head.

Proximal

Anatomy term meaning closer to the point of attachment.

Gross

Refers to large structures in anatomy.