muscular system

All movement requires...?

muscles

What is the muscular system?

the organ system that enables the body to have flexibility and movement.

Name the three types of muscles.

1. skeletal muscle
2. smooth muscle
3. cardiac muscle

skeletal muscle

A muscle that is attached to the bones of the skeleton and provides the force that moves the bones.

smooth muscle

Involuntary muscle found inside many internal organs of the body, (e.g. walls of hollow organs, such as intestines, blood vessels, bladder, and uterus)

cardiac muscle

Found only in the heart, involuntary control, contracts to propel blood into circulatory system.

fascia

A fibrous membrane covering, supporting and separating muscles.

tendon

Attaches muscle to bone.

aponeuroses

Connective tissue that forms broad fibrous sheets which may attach to the covering of adjacent muscles.

epimysium

Connective tissue that closely surrounds a skeletal muscle

perimysium

Layer of connective tissue that extends inward from the epimysium & separates the muscle tissue into small sections.

fascicle

Bundles of skeletal muscle fibers.

endomysium

Connective tissue surrounding a muscle fiber.

deep fascia

Fibrous covering that surrounds deeper organs, even epimysium of muscles.

subcutaneous fascia

Layer of tissue that is under the skin and connects the skin to muscles and underlying tissues

myofibrils

Bundles of protein filaments within the muscle fiber.

myosin

A protein that makes up nearly half of the proteins in muscle cells.

actin

A contractile protein that is part of the thin filaments in muscle fibers.

sarcomeres

Striations the form a repeating pattern of units along each muscle fiber.

sarcoplasmic reticulum

Organelle of the muscle fiber that stores calcium.

transverse tubules

System of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential.

muscle strain

Overstretching, overexertion, or overuse of soft tissue, less severe than a sprain.

Why do skeletal muscles appear striated?

Because muscle cells only contract not extend; skeletal muscles work in pairs. While one muscle contracts the other muscle in the returns to its original state.

synapse

A junction where information is transmitted from one neuron to the next.

neurotransmitters

Chemical messengers that cross the synaptic gaps between neurons.

motor neurons

Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.

neuromuscular junctions

Region where a motor neuron comes into close contact with a skeletal muscle cell.

synaptic cleft

A small gap that separates the membrane of the neuron & the membrane of the muscle fiber.

acetylcholine (ACh)

A neurotransmitter that enables learning and memory and also triggers muscle contraction.

rigor mortis

A fixed muscular contraction after death.

tendonitis

Inflammation of a tendon.

tenosynovitis

Inflammation of the sheath surrounding a tendon.

Poliomyelitis

Acute, contagious viral disease of the central nervous system that can lead to paralysis.

Duchanne Muscular Dystrophy

A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.

The function of skeletal muscle unit is...?

sacromere

Both muscle relaxation and contraction require...?

ATP.

botulism

Rare poisioning caused by toxins produced by Clostridium botulinum bacteria.

myogram

A chart of the timing and strength of a muscle's contraction.

What makes up a motor unit?

A muscle fiber or cell and motor neuron that connect to it.

Myasthenia Gravis

A disease in which acetylcholine receptors on muscle cells are destroyed so that muscles can no longer respond to the acetylcholine signal to contract. Symptoms include muscular weakness and progressively more common bouts of fatigue. The disease's cause is unknown but is more common in females than in males; it usually strikes between the ages of 20 and 50.

Steps of Muscle Contraction & Relaxation

Step 1: A nerve impulse travels down and axon and causes the release of acetylcholine.

Step 2: Acetylecholine causes the impulse to spread across the surface of the sarcolemma.

Step 3: The nerve impulse enters the T Tubules and Sarcoplasmic Reticulum, stimulating the release of calcium ions.

Step 4: Calcium ions combine with Troponin, shifting troponin and exposing the myosin binding sites on the actin.

Step 5: ATP breaks down ADP + P. The released energy activates the myosin cross bridges and results in the sliding of thin actin myofilament past the thick myosin myofilaments.

Step 6: The sliding of the myofilaments draws the Z lines towards each other, the sarcomere shortens, the muscle fibers contract and therefore muscle contracts.

Step 7: ACh is inactivated by Acetylcholinesterase, inhibiting the nerve impulse conduction across the sarcolemma.

Step 8: Nerve impulse is inhibited, calcium ions are actively transported back into the Sarcoplasmic Reticulum, using the energy from the earlier ATP breakdown.

Step 9: The low calcium concentration causes the myosin cross bridges to separate from the think actin myofilaments and the actin myofilaments return to their relaxed position.

Step 10: Sarcomeres return to their resting lengths, muscle fibers relax and the muscle relaxes.

Steps of Muscle Relaxation

1. Ach rapidly decomposes the remaining Ach in the synaspe.
2. Muscle impulses stop.
3. Stimulus to sarcolemma & muscle fiber membrane ceases.
4. Calcium moves back into sarcoplasmic reticulum (SR).
5. Myosin & actin binding prevented.
6. Muscle fiber relaxes.

Cross Bridge Cycling

1. Myosin head attaches to actin binding sites, forming cross-bridges
2. Myosin cross-bridge pulls thin filament.
3. ADP & phosphate released from myosin.
4. New ATP binds to myosin.
5. Linkage between actin & mysin cross-bridge break.
6. ATP splits.
7. Myosin cross-bridge goes back to original position.

creatine phosphate

An energy storage molecule used by muscle tissue; can be removed and attached to an ADP to generate ATP quickly.

Muscle cells are a major source of...?

heat

oxygen debt

The amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose.

thick myofilments

Composed of myosin protein; forms cross bridges.

thin myofilaments

Composed of actin protein; associated with troponin & tropomyosin proteins.

myoglobin

Oxygen storing pigment in muscle tissue.

lactic acid threshold

The value of exercise intensity at which lactic acid production increases.

threshold stimulus

Stimulation level that must be reached to elicit an action potential in a neuron or muscle fiber.

muscle fatigue

Inability of a muscle to maintain its strengh of contraction or tension. Caused by: decreased blood flow, ion inbalances, & accumulation of lactic acid.

cramp

A painful and involuntary muscle contraction.

refractory period

Period of time during which the neuron cannot generate another action potential.

all or none response

When a muscle fiber responds completely or not at all to a stimulus.

twitch

A single quick, jerky muscular contraction from a single nerve impulse followed by relaxation.

muscle tone

Normal state of balanced muscle tension.

summation

Increase force of contraction by a skeletal muscle fiber when a twitch occurs before the previous twitch relaxes.

tetanic contraction

A sustained contraction that lacks partial relaxation.

recruitment

An increase in the number of motor units being activated.

isotonic concentric

When skeletal muscles develop tension and shortens when an external force is applied.

eccentric contraction

Lengthening of the muscle.

isometric contraction

When a skeletal muscle develops tension but does not shorten.

Type I fibers

Dark muscle fibers. Fibers for long sustained or continued contractions (e.g. posture maintaining muscles). Prevalent in endurance athletes. Suited for higher levels of continuous metabolic activity and are associated with aerobic metabolism.

Type IIa fibers

Fibers characterized as inefficient and fatiguable and having low aerobic power, rapid force development, high actomyosin myofibrillar ATPase activity, and high anaerobic power.

Type IIb fibers

White, fast twitch, rapid contraction, anaerobic glycolysis, fatigue rapidly, fine movement muscles such as fingers and eyelids.

visceral smooth muscle

A smooth muscle tissue that forms sheets or layers in the walls of visceral organs.

rhythmicity

Spontaneous repeated contractions.

peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.

Two major types of smooth muscle...?

Multiunit smooth muscle and visceral smooth muscle

multiunit smooth muscle

Muscle fibers that are less well organized and function as separate units, independently of neighboring cells. Found in irises of the eyes & in the walls of large blood vessels.

Cardiac muscle is similar to skeletal muscle...?

via intercalated disks (gap junctions)

What is the function of intercalated discs?

To protect the brain and spinal cord from trauma (buoyancy) and provide a fluid for diffusion (electrolytes, nutrients and metabolic products)

origin

less movable end of a muscle

insertion

more movable end of a muscle

agonist

A muscle that causes an action.

synergist

A muscle functioning in cooperation with another muscle.

prime mover

Muscle responsible for a particular body movement.

antagonist

Chemicals that block the action of a particular neurotransmitter.

smooth muscle contraction

Lack troponin; use calmodulin to bind calcium; slower to contract & relax; affected by hormone by lowering the degree of response to neurotransmitters; can change length without changing tauntness.

cardiac muscle contraction

Only in the heart; composed of striated cells, forming fibers that are interconnected in branching, three-dimensional networks; can contract longer than skeletal muscle fibers.

skeletal muscle contractions

Generate a great variety of body movements; bones and msucles act as levers.

Four Basic Components of a Lever System

1. rigid bar
2. fulcrum
3. resistance
4. force

first-class lever system

Parts are arranged
1. resistance
2. fulcrum
3. force

Examples of First-Class Lever System

seesaws & scissors

second-class lever system

Parts are arranged
1. fulcrum
2. resistance
3. force

Examples of Second-Class Lever System

wheelbarrow

third-class lever system

Parts are arranged
1. resistance
2. force
3. fulcrum

Example of Third-Class Lever System

tweezers

pectoralis major

A muscle of large size (major) in the pectoral region (chest).

deltoid

Shaped like a delta or triangle.

extensor digitorum

Extends digits (fingers) .

extensor digitorum

Extends digits (toes).

biceps brachii

A muscle with two heads (biceps), or points of origin, in the brachium (arm).

sternocleidomastoid

Attached to the sternum, clavicle, & mastoid process.

external oblique

Located near the outside, with fibers that run obliquely or in a slanting direction.

epicranius

Covers the upper part of the cranium & consists of two muscular parts: the frontalis & occipitalis.

orbicularis oculi

A ring-like band of muscle, called a sphincter muscle, that surrounds the eye.

orbicularis oris

A sphincter muscle that encircles the mouth; closes and protrudes lips; used in whistling and forming many letters during speech; the "kissing muscle".

buccinator

Located in the wall of the cheek on the outer surface of maxilla and mandible; helps hold food in contact with teeth when a person is chewing; also aides in blowing air out of the mouth.