A&P- Muscular System

Function of muscles

Function of muscles

Movement

Maintain posture

Stabilize joints

Generate heat

Fascia

Covers the outside of the epimysium

Epimysium

Covers entire skeletal muscle

Perimysium

Covers a fascicle (bundle) of fiber

Endomysium

Covers a single muscle fiber

Tendon

Cord of tough, fibrous tissue that connects a muscle with its bony attachment

Aponeurosis

Sheet like fibrous membrane, resembling a flattening tendon, that binds muscles together or as a means of connection muscle to bone.

Order of muscle structures (big to small)

Muscle→fascicle→muscle cell→myofibril

Parallel

Ex: Parallel muscle

Convergent

Ex: Pectoralis muscle

Pennate

Ex: Extensor digitorum muscle

Bipennate

Ex: Rectus femoris muscle

Sphincter

Orbicularis oris muscle

Origin

Point are which the muscle attaches to a relatively stable part of the skeleton

Insertion

Point at which the muscle attaches to the skeletal part which is moved when it contracts

Prime mover (Agonist)

Muscle with the major responsibility for a certain movement

Antagonist

Muscle that opposes or reverses a prime mover

Synergist

Fixator

Stabilizes the origin of a prime mover. They serve to maintain posture or balance during contraction of prime movers acting on joints in the arms & legs

1st Class lever

Resistance (top) fulcrum(bottom) applied force (bottom)

Example of 1st class lever

Turning head down

2nd Class lever

Fulcrum(bottom) resistance(top) applied force (top)

Example of 2nd class lever

Raising the body up unto the toes

3rd class lever

Fulcrum (bottom) applied force (top) resistance (top)

3rd class lever example

Contraction of the biceps muscle

Excitability (Irritability)

Ability to receive and respond to a stimulus

Contractility

Ability to shorten when an adequate stimulus is received

Extensibility

Ability to lengthen when relaxed and not being stimulated

Sarcolemma

Specialized plasma membrane

I band

Light band, segment that includes the Z line ant the ends of the thin filaments that do not overlap.

A band

Dark band, segment that runs the entire length of thick filaments

Sarcomere

Contractile unit of a muscle cell, extends from one Z line (disc) to the next Z line (disc)

Thick filaments

Composed almost entirely of the protein myosin. Myosin head contains ATP binding site and ATPase.

Thin filaments

Composed primarily of the protein actin. Other proteins are tropomyosin and troponin.

Elastic filaments

Titin & Dystrophin

Titin

Anchors thick filaments to the Z disk

Dystrophin

Protein that holds the thin filaments to the sarcolemma; helps to anchor the muscle fiber to surrounding matrix so that the muscle doesn’t break when it contracts

H zone

Middle region of the thick filaments where they do not overlap the thin filaments

M line

Made up of protein molecules that stabilize the thick filaments.

T Tubules

System of transverse tubules formed by inward extensions of the sarcolemma. These tubules allow impulses traveling along the sarcolemma to move deeper into the cell

Motor unit

One motor neuron, stimulates muscle cells

Neuromuscular junction

Association site of neuron and muscle cell

Synaptic cleft

Gap between neuron/ muscle cell

Interstitial fluid

What fills the area between the neuron and muscle

What determines amount of tension produced by a whole muscle

Frequency of stimulation & number of cells stimulated

Effects of exercise on muscles

Muscle fiber mass increases

Increase in muscle strength

Increase in muscle efficiency

Muscle become more fatigue resistant

Latent period

Time required for the release of Ca² are returned to the sarcoplasmic reticulum by active transport

Contraction period

Time during actual muscle contraction

Relaxation period

Time during which Ca² are returned to the sarcoplasmic reticulum by active transport

Refractory period

Time immediately following a stimulus

Myogram

What tracks a muscle contraction

Tonic contraction

Maintains muscle tone and posture; a sustained partial contraction in response to stretch receptors

Isotonic Contraction

Same tension; changing length

Isometric Contraction

Same length; changing tension

Myalgia

Muscle pain due to strain/ tearing of muscle fibers; symptom of an immune response with a fever

Myositis

Inflammation of muscle tissue due to injury or disease

Charley Horse (fibromyositis)

Inflammation of muscle tissue and the tendons associated with that muscle due to injury (tear or severe bruising- contusion)

Cramps

Painful, involuntary muscle spasms

Cerebral Palsy

Paralysis and/ or weakened muscle due to loss of muscle tone.

Cerebral Palsy Pathophysiology

Lack of oxygen to the motor region of the cerebrum

Cerebral Palsy cause

Complication during birth

Poliomyelitis (Polio)

Viral infection which affects the motor neurons that control skeletal muscles

Muscular Dystrophy

Series of genetic disorder characterized of wasting away of skeletal muscle. Normal dystrophin is missing.

Duchenne Muscular Dystrophy

Primarily affects males. The muscle tissue creaks down and is replaced by fat and fibrous tissue. Death usually occurs around 21 because of respiratory failure.

Myasthenia Gravis

Autoimmune disease: causes progressive damage/ deactivation of the neuromuscular junction (ACh receptors). Causes fatigue and muscle weakness.

Myasthenia Gravis Pathophysiology

Production of IgG antibodies against ACh receptors

Intradermal

Within the skin (allergy, TB)

Subcutaneous

Under the skin (insulin)

Intramuscular

-within the muscle

- absorption rate favorable, not too irritating, accepts large doses

Intravenous

Within a vein (fast action)

Intraspinal

Within the spinal cord (quick CNS access)

Intraosseus

-within a bone (dental and brain surgery)

Sites for IM injections

- gluteus medius

-deltoid

-lateral thigh