Muscular Unit

functions of muscle tissue

movement facilitation

functions of muscle tissue

postural support

functions of muscle tissue

regulation of organ volume

functions of muscle tissue

thermogenesis

functions of muscle tissue

protection of internal organs

elasticity

the ability of muscle tissue to return to its normal resting length after it has been stretched or contracted

excitability

the ability of muscle tissue to receive and respond to a stimulus like nerve impulses

extensibility

the ability of muscle tissue to be elongated or stretched

contractility

the ability of muscle tissue to become short and thick while producing movement

skeletal muscle

* attached to bones
* striated
* voluntary control
* multinucleated
* movement, thermogenesis, posture, protection of internal organs

smooth muscle

* hollow organs (stomach, bladder, blood vessels, etc.)
* non-striated
* involuntary control
* control diameter of blood vessels, peristalsis: propels food and waste through digestive system

cardiac muscle

* myocardium (heart wall)
* striated
* involuntary
* intercalated disks
* contractions of the heart, pumps blood

actin

* thin, light-colored myofilaments (protein fibers)
* anchored to the z-lines of sarcomeres


* contain two regulatory proteins:

tropomyosin

troponin

tropomyosin

-blocks muscle contraction
-thread-like intertwined protein molecules
-blocks actin's active sites preventing cross-bridge formation with myosin while the sarcomere is relaxed

troponin

-promotes muscle contraction
-globular proteins composed of three subunits
-one subunit binds to actin, one to tropomyosin, and the last binds to Ca+

myosin

-thick, dark-colored myofilaments
-found in the center of the sarcomere
-forms cross-bridges with actin molecules during muscle contraction
-alternate with actin myofilaments to form striations
-golf club shaped (long, thick protein molecule with a globular head)

threshold stimulus

the weakest stimulus from a neuron that stimulates muscle contraction

all or nothing principle

the threshold stimulus contacts the motor unit, causes innervated muscle fibers to contract to their fullest potential

motor neuron

a nerve carrying nerve impulses from the brain and stimulates muscles to contract

neuromuscular junction

-also called the synaptic cleft
-the end of the axon terminal where it attaches to the muscle fiber

synaptic vesicles

-the synaptic end bulb, also called the axon terminal, store neurotransmitters

motor end plate

part of the muscle fiber at the end of the axon terminal

acetylcholine (Ach)

the neurotransmitter released from the synaptic vesicles that initiates an action potential in muscle fibers

the sliding filament theory

During muscle contraction, the globular heads of the myosin attach to the active sites of the actin myofilament and "ratchet" or swivel pulling the actin towards the center of the sarcomere (unit of contraction). This causes the actin myofilaments to slide past one another resulting in a shortening of a sarcomere. The sarcomere shortens and the muscle contracts.

cholinesterase

the enzyme that destroys acetylcholine

origin

-body segment with the most mass
-more proximally located
-large surface area of attachment
-immovable end of muscle

insertion

-body segment with the least mass
-more distally located
-smaller surface area of attachment
-movable end of muscle

gaster (belly)

the fleshy portion of a muscle between the origin and insertion

agonist

the muscle responsible for the majority of force during movement

antagonist

the muscle that performs the opposite movement of the agonist

synergist

a muscle that assists the agonist by providing additional force or directing the force of the agonist

fixator (stabilizer)

a muscle that stabilizes a point of body position

biceps brachii

anterior upper arm muscle, flexes the forearm

biceps femoris

long muscle in the posterior aspect in the thigh responsible for hip and knee joint movement, part of the hamstring muscle group

triceps brachii

posterior upper arm muscle, extends the forearm

sternocleidomastoid

anterior aspect of the neck (sternum --> clavicle --> mastoid process)
flexes the head and neck

trapezius

posterior aspect of the neck, extends the head and neck

deltoid

covers the shoulder, abducts the arm

pectoralis major

chest, adducts the arm

latissimus dorsi

superficial muscle of the thoracic and lumbar region of the back, internal rotation, flexes or extends the arm

diaphragm

internal muscle separating the thoracic and abdominal cavities, increases and decreases volume of thoracic cavity (breathing muscle)

gastrocnemius

posterior aspect of the lower leg, plantar flexion

hamstring muscle group

posterior aspect of the thigh, flexes the lower leg

biceps femoris, semimembranosus, semitendinosus

quadriceps muscle group

anterior aspect of the thigh, extends the lower leg

vastus femoris, vastus medialis+intermedialis+lateralis

gluteus maximus

buttocks region, extends a flexed thigh or hyperextends the thigh from anatomical position

rectus femoris

anterior aspect of the thigh, part of the quadriceps muscle group, extends the lower leg at the knee

vastus lateralis + intermedialis + medialis

anterior compartment of the thigh, makes up the quadriceps muscle group

buccanator

cheek muscle, active role in mastication, swallowing, blowing, and sucking

masseter

runs from the cheek bone to either side of the lower jaw, main muscle in mastication

fibromyalgia

a widespread musculoskeletal pain and fatigue disorder with an unknown cause. pain in the muscles, tendons, and ligaments

muscular dystrophy

* Genetic diseases characterized by muscular atrophy of skeletal muscle tissue.
The most common form of muscular dystrophy is Duchenne's Muscular Dystrophy where the skeletal muscle is replaced by fat and fibrous tissue

shin splints

soreness and pain in the front of the lower leg due to excessive strain of the tibialis posterior, which pulls the periosteum away from the bone affecting the tibialis anterior.

muscle strain

* muscle pain
1st degree: microtears
2nd degree: partial tear
3rd degree: complete rupture