anatomy unit 5: muscular system notes (w/o major muscles)

muscle

Soft Tissue that contains protein filaments that slide past one another, producing a contraction that changes both the length and the shape of the cell.

functions of muscular system

Producing Force and Movement

Maintaining Posture

Stabilizing Joints

Generating Heat

cardiac muscle

muscle that has striations, One nucleus, Branching cell shape, and Intercalated Disks

Functions: Involuntary Movement of Heart

smooth muscle

Found in Walls of Hollow Organs. No striations, One nucleus, Spindle-shaped cells

Function: Involuntary movement (propels substances along a pathway)

skeletal muscle

Found attached to the skeleton

Features: Striations, Many nuclei, Long cylindrical cells

Functions: Voluntary movement

tendon

dense regular connective tissue that attaches a muscle to bone

Epimysium

connective tissue layer that surrounds an entire muscle

Muscle Bundle

a collection of muscle fibers

Perimysium

connective tissue layer that surrounds a muscle bundle

Muscle Fiber

muscle cell

Endomysium

connective tissue layer that surrounds a muscle cell/fiber

Sarcolemma

the plasma membrane of a muscle cell.

myofibril

Long ribbon-like organelles, which nearly fill the entire cell. Responsible for contractions.

Sarcomeres

a section of the myofibril. Tiny contractile units, which are lined up and make up the myofibril.

Myofilaments

Thin threadlike proteins within the sarcomere.

Thick filaments

or myosin filaments, are made mostly of bundled molecules of the protein myosin.

Myosin

one of the principal contractile proteins.

Cross bridges

Small projections or myosin heads. (On thick filaments) Also called myosin heads.

Thin filaments

composed of actin.

Actin

one of the principal contractile proteins.

Z-disk

structural element, fiber that holds the sarcomere together

H-zone

space in the middle of the sarcomere where thin filaments are absent, this disappears during a contraction

A-Band

dark region on the electron micrograph

I-band

lighter region on the electron micrograph

Sarcoplasmic reticulum (SR)

a specialized smooth endoplasmic reticulum.

The interconnecting tubules and sacs of the SR surround each and every myofibril.

The major role: to store calcium and to release it on demand when the muscle fiber is stimulated to contract. (Calcium provides the final "go" signal for contraction.)

The Sliding Filament Theory

theory that actin filaments slide toward each other during muscle contraction, while the myosin filaments are still

steps:

1. Muscle fibers are activated by the nervous system, and an action potential begins.

2. Calcium ions are released from the SR.

3. Calcium ions bind to the regulatory proteins on the thin filaments, exposing the binding site to the Myosin Heads.

4. The Myosin Heads (cross bridges) attach to the myosin binding sites on the thin filaments.

5. Energized by ATP, each Myosin Head attaches and detaches several times during a contraction.

6. When the action potential ends, the calcium ions are reabsorbed by the SR and the Myosin Heads can no longer attach to the binding sites; everything slides back into place.

nerve impulses

electrical signals transmitted by neurons that are required for skeletal muscles to contract

Motor Unit

One neuron and all of muscle cells it stimulates.

Neuromuscular junction

the region where a motor neuron comes into close contact with a skeletal muscle.

Synaptic cleft

the fluid-filled space at a synapse between neurons

Neurotransmitter

chemical released by neurons that may, upon binding to receptors stimulate or inhibit them.

Acetylcholine

a chemical transmitter (signal) released by nerve endings that enables muscle action

Action potential

an electrical event occurring when a stimulus of sufficient intensity is applied to a neuron or muscle cell.

Aerobic/endurance exercise

exercise that will result in stronger, more flexible muscles with greater resistance to fatigue. Does not cause muscles to increase in size.

Resistance/isometric

exercise that will result in larger muscle cells, also increases the amount of connective tissue that reinforces the muscle. Muscles increase in size.

muscle atrophy

lack of muscle activity; reduces muscle size, tone, and power

aerobic exercise effect on the body

Blood supply increases to muscles

Individual muscle cells form more mitochondria

Muscle cells store more oxygen

Overall body metabolism becomes more efficient

Digestion improves

Neuromuscular coordination increases

Skeleton become stronger

Heart enlarges

Fat deposits are cleared from blood vessels

Lungs become more efficient

resistance/isometric effect on body

Increases muscle cell size

Muscle cells make more contractile filaments

Increases amount of connective tissue around muscle

Muscle fatigue

is the decline in ability of a muscle to generate force.

neural fatigue

a reduced ability to generate force caused by a diminished signal from the nervous system to the muscle

metabolic fatigue

fatigue when there is reduced ability of the muscle fiber to contract; thought to happen due to insufficient oxygen that leads to lactic acid, but evidence now suggests its from insufficient amounts of ions in the immediate area, so the muscles run low on their supply of ions.

Abduction

moving limb away from midline

Adduction

moving limb towards midline

Circumduction

moving a limb in a circular motion

Flexion-

decreasing the angle of a limb (bending)

Extension

increasing the angle of a limb (straightening)

Eversion

twisting limb laterally (away from midline)

Inversion

twisting limb medially (towards midline)

Pronation

a limb is turned down (palms faced down; weight on foot is turned inwards)

Supination

a limb is turned up (palms faced up; weight on foot is turned outwards)

Rotation

twisting a limb around a pivot point (similar to circumduction, but it does not have to be a full circle)

Plantar flexion

movement of the foot when it is bent at the ankle away from the body (point toes)

Dorsiflexion

raising the foot upwards towards the shin (flex toes)

Amyotrophic Lateral Sclerosis (ALS)

aka Lou Gehrig's disease; is a progressive neurodegenerative disease. The spinal cord and brain harden/ scar, motor neurons stop working and the muscle wastes away. The cause is unknown.

Multiple Sclerosis (MS)

autoimmune disease, where the immune system is attacking the protective coating around neurons leading to harden/scarring of the neurons. Motor neurons stop working and the muscle wastes away.

Muscular Dystrophy

a genetic disorder, symptoms appear during childhood. Abnormal genes lead to muscular deterioration.

Myasthenia gravis

autoimmune disease, where the immune system attacks the acetylcholine receptor sites. This makes is hard to for the nervous system to properly communicate with the muscles, leading to poor control over muscle function.

Myopathy

a genetic disorder and a group of diseases where the muscle fibers do not contract as they should. this can affect any muscle type: smooth, cardiac, or skeletal.