Anatomy Muscle Vocab

A band

Either side of the H-zone of a muscle sarcomere, that is the area where contraction and relaxation of muscle occurs. Srcomeres overlap during movements (compress)

Involuntary muscle

Muscle that contracts without conscious control, such as cardiac and smooth muscle.

Transverse (T) tubule

Extension of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells

Fascicle

A bundle of muscle fibers.

Tropomyosin-troponin complex

Proteins that block myosin-binding sites on actin when calcium is absent.

Acetylcholine (ACh)

Neurotransmitter that carries signals from nerves to muscles.

Isometric contraction

Muscle contraction without a change in muscle length or visible movement. No motion and used to stabilize joint.

Sarcolemma

Transparent tubular sheath that envelopes fibers of skeletal muscles. Barrier between extra & intracellular compartments, defining individual muscle fibers from surroundings

Acetylcholine receptor

Membrane protein that receives and binds acetylcholine.

Isotonic contraction

Muscle contraction where the muscle changes length while maintaining tension.

Sarcomere

The basic contractile unit of a muscle fiber.

Acetylcholinesterase

Enzyme that breaks down acetylcholine and stops the nerve signal.

Latent period

Short delay between muscle stimulation and the beginning of tension.

Sarcoplasm

The cytoplasm of striated muscle cells

Actin

Thin protein filament involved in muscle contraction.

Length-tension relationship

Relationship between muscle length and the amount of tension it can produce.

Sarcoplasmic reticulum

Specialized smooth ER that is important in transmitting the electrical impulses as well as in the storage of calcium ions.

Aerobic metabolism

Production of ATP using oxygen.

Motor end plate

Specialized area of the muscle membrane that synapses between the terminal of motor neuron and the muscle ( triggers contraction)

Sliding filament theory

Theory that actin slides past myosin, shortening the sarcomere during contraction.

Anaerobic metabolism

Production of ATP without using oxygen.

Motor neuron

cell body is located in the motor cortex, brainstem, or spinal cord, and whose axon projects to the spinal corf or outside of the spinal cord to control muscles and glands.

Skeletal muscle

Voluntary, striated muscle attached to bones that produces movement, controls body temperature, and stabilizes joints.

Aponeurosis

Wide, flat sheet of connective tissue that attaches muscle to another structure.

Motor unit

One motor neuron and all the muscle fibers it controls.

Spatial summation

Signals coming from multiple simultanious inputs

Asynchronous firing of motor units

Motor units take turns contracting to help maintain muscle activity and reduce fatigue.

Multiunit smooth muscle

Smooth muscle whose cells contract independently and are individually controlled.

Striations

Alternating light and dark stripes found in skeletal and cardiac muscle.

Muscle fiber

A single muscle cell.

Synaptic cleft

Tiny gap between axon terminal of the presynaptic neuron and membrane of postsynaptic cell

Cardiac muscle

Involuntary, striated muscle found only in the heart.

Muscle tone (tonus)

Constant, slight muscle contraction present even when resting.

Synaptic knob

(Bouton) is relay point at the tip of a transmitting neuron in the brain

Glycogen

Stored form of glucose used by muscles for energy.

Twitch contraction

One quick muscle contraction in response to one stimulus.

Glycogen-lactic acid system

Energy system that breaks down glucose without oxygen to produce ATP and lactate.

Visceral (single-unit) smooth muscle

Smooth muscle that produces slow, steady contractions that allow substances, like food in digestive tract, to move through body.

I band

Light band of a sarcomere containing only thin actin filaments.

Recruitment

measure of how many motor neurons are activated in a particular muscle. Higher = stronger muscle contraction

Voluntary muscle

Muscle that is consciously controlled.

Incomplete tetany

Rapid repeated muscle contractions with partial relaxation between contractions.

Innervation

Nerve supply to a muscle.

Refractory period

Short period after stimulation when a muscle cell cannot respond normally to another stimulus.

Wave summation

Increased muscle tension when repeated stimuli occur before the muscle fully relaxes. Faster than it can relax

Intercalated discs

Special connections between cardiac muscle cells that help them communicate and contract together.

Relaxation Phase Z line

Z-lines are closer during contraction because actin and myosin interaction generates cross-bridges, which slide the myofilaments over each other. During relaxation, myosin and actin detach and the z-lines slide back apart.

Agonist (prime mover)

Main muscle responsible for producing a particular movement.

Gracilis

Long, thin muscle on the inner thigh that helps bring the leg inward and bend the knee.