The Muscular System and Muscle Physiology

Vocabulary and concepts regarding muscle types, connective tissues, nerve control, and physiological theories of contraction based on the lecture transcript.

Muscular System Functions

The body contains over $600$ muscles which serve three major functions: body movement, posture, and essential body functions (stable core temperature, heat generation, blood flow, and movement of food/substances).

Skeletal Muscle

External muscles attached to bones that are responsible for all voluntary movements.

Smooth Muscle

Involuntary muscles found in the digestive system and the walls of vital organs like the stomach.

Cardiac Muscle

Involuntary muscles that make up the wall of the heart.

Cartilage

Smooth and elastic tissue used for protection and shock absorption; examples include hyaline cartilage at the end of bones, discs between vertebrae, and attachments between ribs and the sternum.

Tendons

Inelastic but very strong connective tissue that attaches muscle to bone.

Ligaments

Slightly elastic straps that attach bone to bone; their main function is to provide stability to a joint and prevent dislocation.

Achilles tendon

A well-known tendon that attaches the gastrocnemius to the calcaneus, or heel.

Anterior cruciate

A ligament of the knee that, when ruptured, typically requires reconstruction because the joint becomes too unstable.

Muscle Structure Layers

The hierarchy of muscle structure includes the Epimysium (outer layer), Perimysium, Fascicle, Endomysium, and individual Muscle fiber.

Cell body

The part of a motor neuron that controls activity in the cell.

Axon

The part of a motor neuron that conducts impulses away from the cell body.

Dendrites

The parts of a motor neuron acting as receptors from other neurons.

Origin

The point where the muscle tendon attaches to the non-moving bone closest to the centre of the body.

Insertion

The muscle attachment to the bone that moves most when the muscle contracts; for example, the Radius for the Biceps muscle.

Sliding Filament Theory

A theory describing muscle contraction involving the sarcomere, thick filaments (myosin), and thin filaments (actin).

Reciprocal Inhibition

A process where the muscle on one side of the body contracts (agonist) while the muscle on the opposite side relaxes (antagonist).

Agonist

The contracting muscle in a reciprocal inhibition pair; for example, the biceps during the upward phase of a bicep curl.

Antagonist

The relaxing muscle in a reciprocal inhibition pair; for example, the triceps during the upward phase of a bicep curl.

Isotonic Contraction

A common contraction where the length of the muscle changes, such as when kicking a football.

Isometric Contraction

A contraction where the muscle length stays the same, such as when pushing against a wall.

Isokinetic Contraction

A contraction where the force created throughout all angles is maximal, which can only occur using a machine.

Slow Twitch Muscle Fibre

Suited for endurance events (e.g., Marathon); characterized by slow contraction speed, low fatigability, and smaller size.

Fast Twitch Muscle Fibre

Suited for high intensity power events (e.g., Long jump); characterized by fast contraction speed, high fatigability, and larger size.

Muscle Fibre Proportions (Examples)

Individual athlete profiles show varying fibre percentages: Marathoners ($82\%$ ST), Sprinters ($73\%$ FT), and Swimmers ($74\%$ ST).