Muscular System Contraction Lecture Notes

These flashcards cover various aspects of the muscular system, including muscle types, contractions, neuromuscular junctions, and the biochemical mechanisms behind muscle movements.

Skeletal muscle

Type of muscle tissue attached to bones that allows movement.

Cardiac muscle

Involuntary muscle found only in the heart.

Smooth muscle

Involuntary muscle found in walls of hollow organs.

Excitability

Ability of muscle to receive stimuli and respond.

Contractility

Muscles shorten when they receive a stimulus.

Extensibility

Muscles can be stretched beyond their resting length.

Elasticity

Muscles recoil and resume their resting length after being stretched.

Isotonic contraction

Muscle length changes to a load.

Concentric contraction

Muscle shortens during contraction.

Eccentric contraction

Muscle lengthens during contraction.

Isometric contraction

Tension is produced but the length does not change.

Epimysium

Connective tissue that covers the whole muscle.

Perimysium

Connective tissue that wraps around fascicles of muscle.

Endomysium

Connective tissue that wraps around individual muscle fibers.

Direct attachment

Muscle fuses straight onto periosteum.

Indirect attachment

Tendon attaches muscle to bone.

Arteriole supply

Supplies blood to the muscles.

Venous return

Process of taking blood away from the muscles.

Sarcolemma

Membrane that wraps the muscle cell.

Sarcoplasm

Fluid inside the sarcolemma containing O2 and nutrients.

Myofibrils

Long threads running inside a muscle fiber.

Sarcomeres

Contractile units inside myofibrils.

Sarcoplasmic reticulum

Stores and regulates calcium in muscle fibers.

T-Tubules

Disperse electrical signals evenly to muscle fibres.

Myosin

Thick filament rich in muscle cells.

Actin

Thin filament rich in muscle cells.

Titin

Elastic filament that ties myosin to the Z disc.

Z disc

End of a sarcomere where actin attaches.

M line

The middle of the sarcomere where myosin is located.

Power stroke

The process where myosin pulls actin towards the M line.

Cross bridge formation

When myosin heads bind to actin.

Detachment

When a new ATP molecule allows myosin to detach from actin.

Cocking of the myosin head

Action of the myosin head returning to a starting position after detaching.

Rigor mortis

Stiffness of muscles after death due to depletion of ATP.

Creatine

Substance that helps convert ADP back to ATP for energy.

Myogram

Recording of muscle contractile activity.

Muscle twitch phases

1. Latent: cross bridges start; 2. Contraction: tension changes; 3. Relaxation: cross bridges let go.

Twitch summation

Increased tension due to frequency of stimuli.

Unfused tetanus

More calcium released due to successive stimuli before relaxation.

Fused tetanus

Maximum possible tension produced in muscle.

Motor unit recruitment

Increasing the force of muscle contraction by activating more motor units.

Neuromuscular junction

The connection between a motor neuron and muscle fiber.

ACh (Acetylcholine)

Neurotransmitter that triggers muscle contractions.

Synaptic cleft

Gap between the neuron and muscle fiber.

Troponin

Protein that binds to actin and tropomyosin.

Tropomyosin

Protein that covers active binding sites on actin.

Calcium release

Triggers muscle fibers to contract.

Myomesin

Protein that makes up the M line of sarcomeres.

Calcium

Essential for muscle contraction as it binds to troponin.

ATP (Adenosine Triphosphate)

Energy currency of the cell used in muscle contraction.

ADP (Adenosine Diphosphate)

Byproduct formed when ATP is used for energy.

Capillaries

Tiny blood vessels that transfer oxygen and nutrients to muscle fibers.

Motor neuron

Neurons that innervate muscle fibers and control their contractions.

Muscle fibres

Individual muscle cells also known as myocytes.

Sarcomere arrangement

Orderly arrangement of thick and thin filaments.

Excitation contraction coupling

Process of converting an electrical stimulus to a mechanical response.

Action potential (AP)

Electrical signal that travels along the sarcolemma.

Calcium channels

Allow calcium to flow into the muscle cell during contraction.

Calcium binding

Calcium binds to troponin to initiate muscle contraction.

Electrical signal

Signal that triggers the release of neurotransmitters at the NMJ.

Chemical signal

Neurotransmitters that facilitate muscle contraction.

Twitch

A single contraction-relaxation cycle in muscle.

Fine motor control

Precise movements performed by small motor units.

Spastic paralysis

Muscle rigidity caused by overactive contractions.

Lockjaw (Tetanus)

Condition caused by Clostridium tetani that leads to muscle spasms.

Contractile elements

Myosin and actin within the sarcomeres responsible for contractions.

Functional unit of muscle

The sarcomere, which contains all necessary components for contraction.

Muscle fatigue

Reduced ability of muscles to generate force.

Muscle tone

Sustained muscle contraction that helps maintain posture.

Muscle hypertrophy

Increase in muscle size due to exercise.

Muscle atrophy

Decrease in muscle size due to lack of use.

Aerobic exercise

Exercise that improves oxygen consumption and muscular endurance.

Anaerobic exercise

High-intensity activity that does not require oxygen directly.

Muscle memory

The ability of the brain and muscles to remember movements.

ATPase

Enzyme that catalyzes the breakdown of ATP in muscle fibers.

Intracellular calcium stores

Calcium stored in the sarcoplasmic reticulum for muscle contraction.

Dynamic tension

Variation of muscle tension during contraction.

Robust muscle contractions

Strong, sustained muscle contractions generated by extensive motor unit recruitment.

Motor unit

A group of muscle fibers that are innervated by a single motor neuron.