Skeletal Muscle Physiology Flashcards

Flashcards about Skeletal Muscle Physiology

What are the functions of the muscular system?

Body movement, maintenance of posture, respiration, communication, constriction of organs/vessels, heartbeat, and production of body heat.

What are the four properties of muscle?

Excitability, Contractility, Extensibility, and Elasticity.

List the three types of muscle tissue.

Skeletal muscle, Smooth muscle, and Cardiac muscle.

Where is skeletal muscle found and how is it controlled?

Attached to bones; voluntary, controlled by somatic motor neurons.

Where is smooth muscle found and how is it controlled?

In the walls of hollow organs, blood vessels, eye, glands, uterus, skin; involuntary, controlled by endocrine and autonomic nervous systems.

Where is cardiac muscle found, and how is it controlled?

Heart; autorhythmic; involuntary, controlled by endocrine and autonomic nervous systems.

What are the three connective tissue sheaths associated with skeletal muscle?

Epimysium, Perimysium, and Endomysium.

What is the function of epimysium?

Surrounds the entire muscle, separating it from surrounding tissues and organs.

What is the function of perimysium?

Surrounds a group of muscle fibers called a fascicle; contains blood vessels and nerves.

What is the function of endomysium?

Surrounds individual muscle fibers; also contains blood vessels, nerves, and satellite cells.

What is the sarcolemma?

The cell membrane of a muscle fiber, surrounding the sarcoplasm.

What are T-tubules?

Narrow tubes that extend into the sarcoplasm at right angles to the surface, filled with extracellular fluid.

What are myofibrils?

Cylindrical structures within muscle fiber; bundles of protein filaments (myofilaments).

What are the two types of myofilaments?

Actin filaments (thin filaments) and Myosin filaments (thick filaments).

What is the sarcoplasmic reticulum (SR)?

Elaborate, smooth endoplasmic reticulum that stores Ca++ when muscle is not contracting.

What is a triad?

A single T-tubule and the 2 terminal cisternae of the SR.

Describe myosin myofilaments.

Elongated molecules with heads that can bind to actin, forming cross-bridges; have ATPase activity.

Describe actin myofilaments.

Composed of F actin, tropomyosin, and troponin; contains binding sites for myosin.

Define muscle contraction.

The active process of generating a mechanical force in muscle.

Differentiate between Isotonic and Isometric contraction.

Isotonic contraction consists of approximation of both ends of a muscle under a constant load; Isometric contraction consists of contraction without appreciable decrease in length of the whole muscle.

What is a muscle twitch?

Mechanical response (contraction) to a single action potential.

Name two types of summation in skeletal muscle contraction.

Spatial summation and Temporal summation.

Describe spatial summation.

Stimulation of many nerve fibres causes an increasing number of motor units to be excited.

What is temporal summation?

Separate muscle contractions are caused by single APs when their frequency is low.

What is tetanization?

When contractions fuse together and cannot be distinguished resulting into a tetanic and smooth contraction.

Isometric contractions

Produces no movement and is used in standing, sitting and posture.

Isotonic contractions

Does work because muscle is allowed to shorten which exerts mechanical work.

List the phases of muscle contraction.

Latent period, contraction period, relaxation period, and refractory period.

What happens during muscle contractions at the molecular level?

Actin and myosin slide upon each other, increasing their overlap and bringing Z lines closer together.

What is excitation-contraction coupling?

The sequence of events linking the transmission of an action potential along the sarcolemma to muscle contraction.

What are the steps in muscle relaxation?

Ca2+ ions pumped back into the sarcoplasmic reticulum, release of Ca2+ from troponin, and cessation of interaction between actin and myosin.

Describe the sliding filament model of muscle contraction.

Thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree.

What are actions that stop the contraction of a muscle?

When action potentials cease the muscle stops contracting.

What is muscle fatigue

Lack of oxygen causes ATP deficit. Lactic acid builds up from anaerobic respiration in muscle tissue causing fatigue.

Define atrophy.

Weakening and shrinking of muscle.

Define hypertrophy.

Enlargement of a muscle.