T3 gpt

Skeletal Muscles

There are over 600 skeletal muscles in the human body, accounting for 40-50% of body weight.

Preferred Energy Source

Lipids (fatty acids) are the preferred energy source for muscle.

LPL (Lipoprotein Lipase)

An enzyme that brings fatty acids into muscle cells for fuel.

HSL (Hormone Sensitive Lipase)

An enzyme that breaks down stored fat into fatty acids.

High Insulin Effects

Increases LPL activity in fat cells, decreases LPL activity in muscle cells, and decreases HSL activity.

Levels of Muscle Organization

1. Myofilaments → 2. Myofibrils → 3. Muscle fibers (cells) → 4. Fascicles → 5. Muscle organ.

Endomysium

Connective tissue that covers individual muscle fibers (cells).

Perimysium

Connective tissue that covers bundles of muscle fibers called fascicles.

Epimysium

Connective tissue that covers the entire muscle organ.

Fascia

Connective tissue that covers the epimysium.

Tendon

A cord-like structure that connects muscle to bone.

Aponeurosis

A broad, flat sheet of connective tissue connecting muscle to bone.

Tendon Sheaths

Structures that reduce friction by enclosing tendons.

Prime Mover (Agonist)

The muscle that directly performs an action.

Antagonist

The muscle that opposes the action of the prime mover.

Synergist

A muscle that assists the prime mover.

Fixator

A muscle that stabilizes a joint.

Forearm Flexion Example

Prime mover: Biceps brachii; Antagonist: Triceps brachii; Synergist: Brachioradialis; Fixator: Shoulder muscles.

Class I Lever

Fulcrum is in the middle, like a seesaw (e.g., tilting head back).

Class II Lever

Load is in the middle, like a wheelbarrow (e.g., standing on toes).

Class III Lever

Effort is in the middle, which is the most common type (e.g., flexing forearm at the elbow).

Muscle Naming by Shape

Examples include Trapezius, Deltoid, and Rhomboid.

Muscle Naming by Location

Examples include Gluteus and Tibialis anterior.

Muscle Naming by Size

Descriptive terms include Maximus, Medius, Minimus, Major, Minor.

Muscle Action Nomenclature

Muscles may be named based on their action, such as Flexor or Extensor.

Sternocleidomastoid

Example of a muscle named based on attachment points.

Muscle Naming by Number of Heads

Examples include Biceps, Triceps, and Quadriceps.

Fiber Direction Naming

Terms like Rectus (straight) and Oblique (angled) describe fiber direction.

Main Functions of Muscles

1. Movement; 2. Heat production; 3. Posture maintenance.

Muscle Fiber Components

1. Sarcolemma; 2. T-tubules; 3. Sarcoplasmic Reticulum; 4. Myofibrils; 5. Sarcomeres; 6. Myofilaments.

Sarcolemma

The cell membrane of a muscle fiber.

T-tubules

Structures that transport nerve impulses into muscle fibers.

Sarcoplasmic Reticulum (SR)

Organelle that stores calcium in muscle cells.

Myofibrils

Structures in muscle fibers that contain sarcomeres.

Sarcomeres

The functional contractile unit of muscle fibers.

Myofilaments

Structures that include thick (Myosin) and thin (Actin, Troponin, Tropomyosin) filaments.

Rigor Mortis

Stiffening of muscles after death due to lack of ATP.

Myasthenia Gravis

An autoimmune disease that destroys acetylcholine receptors, causing muscle weakness.

Botulism

Condition that blocks excitatory acetylcholine receptors, causing flaccid paralysis.

Tetanus

Condition that blocks inhibitory acetylcholine receptors, causing spastic paralysis.

ATP/CP System

Provides energy for 2-4 seconds through creatine phosphate regeneration of ATP.

Anaerobic Respiration

Energy system that uses glucose without O2; lasts ~30-40 seconds and produces lactic acid.

Aerobic Respiration

Energy system that uses glucose and O2; lasts indefinitely and produces 34 ATP per glucose.

Muscle Fiber Types

1. Slow-Twitch (Red) for endurance; 2. Fast-Twitch (White) for explosive movements; 3. Intermediate (Pink) for mixed activity.

Motor Unit

A motor neuron and all the muscle fibers it controls.

Small Motor Units

Provide fine motor control, such as in hands and eyes (~100 muscle fibers).

Large Motor Units

Provide gross motor control, such as in legs (~2000 muscle fibers).

Muscle Fatigue

Occurs when a muscle runs out of ATP or O2, leading to weakness and lactic acid buildup.

 Over 600 (40-50% of body weight)

How many skeletal muscles are in the human body?