Test 3 bio

Skeletal Muscles

Over 600 skeletal muscles in the body, accounting for 40-50% of body weight.

Functions of Muscles

Breathing, posture, movement, urination, laughing, etc.

Preferred energy source for muscles

Lipids (fatty acids).

Lipoprotein Lipase (LPL)

An enzyme on cell membranes that stores fatty acids in fat cells and helps muscle cells burn fatty acids for energy.

Hormone-Sensitive Lipase (HSL)

An enzyme inside fat cells that breaks down stored fat and releases fatty acids into circulation.

Effect of high insulin levels on LPL

Increases LPL in fat cells (fat storage) and decreases LPL in muscle cells (less fat usage).

Effect of high insulin levels on HSL

Reduces HSL, leading to less fat breakdown.

Thick & Thin filaments

Components of myofibrils in muscle cells.

Muscle cell (fiber)

Made of myofibrils which contain thick and thin filaments.

Fascicle

A bundle of muscle fibers.

Endomysium

Covers muscle fibers.

Perimysium

Covers fascicles.

Epimysium

Covers muscle organs.

Fascia

Covers epimysium and reduces friction.

Tendon

A connective tissue cord that attaches muscle to bone.

Aponeurosis

A broad, flat connective tissue sheet.

Tendon Sheaths

Tube-like structures that enclose tendons.

Origin of a muscle

Fixed attachment that does not move.

Insertion of a muscle

The attachment that moves toward the origin.

Prime Mover (Agonist)

The muscle that directly performs an action.

Antagonist

The muscle that opposes the Prime Mover.

Synergist

A muscle that assists the Prime Mover.

Fixator

A muscle that stabilizes joints.

Lever in the body

Bone, with a fulcrum at the joint and load as the body part being moved.

Class I Lever

Fulcrum is in the middle, e.g., tilting head back.

Class II Lever

Load is in the middle, e.g., standing on toes.

Class III Lever

Effort is applied in the middle, e.g., flexing the forearm.

Muscle Naming - Shape

Named based on shape, e.g., Trapezius (trapezoid).

Muscle Naming - Location

Named based on body location, e.g., Gluteus (buttocks).

Muscle Naming - Size

Named according to size, e.g., Maximus (largest), Minimus (smallest).

Muscle Naming - Action

Named for the action they perform, e.g., Flexor, Extensor.

Muscle Naming - Attachment

Named for attachment points, e.g., Sternocleidomastoid.

Muscle Naming - Number of Heads

Named according to number of heads, e.g., Biceps (2 heads).

Muscle Naming - Fiber Direction

Describes fiber orientation, e.g., Rectus (straight), Oblique (diagonal).

Buccinator

Muscle in the cheeks responsible for smiling, blowing, and sucking.

Masseter

Muscle in the jaw that closes the jaw.

Sternocleidomastoid

Muscle in the neck responsible for head flexion and rotation.

Trapezius

Muscle in the shoulder/upper back that extends the head and shrugs shoulders.

Pectoralis Major

Muscle in the chest known as the hug muscle or for arm adduction.

Latissimus Dorsi

Muscle in the back responsible for posterior arm adduction.

Deltoid

Shoulder muscle responsible for arm abduction/lifting.

Biceps Brachii

Upper arm muscle responsible for forearm flexion.

Triceps Brachii

Upper arm muscle responsible for forearm extension.

Gluteus Maximus

Buttocks muscle responsible for thigh extension and rotation.

Quadriceps Group

Muscles in the thigh responsible for leg extension and kicking.

Hamstring Group

Muscles in the thigh responsible for leg flexion and bending.

Tibialis Anterior

Muscle in the front lower leg responsible for dorsiflexion (foot up).

Gastrocnemius

Muscle in the back lower leg responsible for plantar flexion (pointed toes).

Muscle Functions

Include movement, heat production, and maintaining posture.

Excitable muscle fibers

Muscle fibers that respond to stimuli.

Contractile muscle fibers

Muscle fibers that can shorten.

Extensible muscle fibers

Muscle fibers that can stretch.

Sarcolemma

Cell membrane of muscle fibers.

T-Tubules

Structures that transport nerve impulse into muscle fibers.

Sarcoplasmic Reticulum (SR)

Structure that stores calcium in muscle fibers.

Myofibrils

Structures that contain sarcomeres, the functional unit of contraction.

Sarcomere

Segment of myofibril between Z-lines.

Thick Myofilament

Consists of myosin and forms cross-bridges.

Thin Myofilaments

Include actin, troponin, and tropomyosin.

Sliding Filament Theory

Describes the process of muscle contraction.

Rigor Mortis

Stiff muscles after death due to calcium flooding and no ATP to release myosin-actin bonds.

Muscle Atrophy

Loss of muscle size or strength.

Muscle Tone

Constant slight contraction of muscles for posture.

Muscle Flaccidity

Absence of muscle contraction, often due to nerve damage.

Myalgia

Muscle pain, commonly associated with statin drugs.

Myopathy

A muscle disease characterized by pain, weakness, and wasting.