Anatomy & Physiology Muscle Study Flashcards
Three Types of Muscles
- Smooth
- Cardiac
- Skeletal
Smooth Muscle
Located- digestive tract, blood vessels, bladder, airways, uterus.
Non-striated
Involuntary (contracts naturally)
Cardiac Muscle
Located- Only in the heart
Involuntary (contracts naturally)
Skeletal Muscle
Attaches to bone & causes movement in body.
Appears stripped under a microscope.
Voluntary ( contrast at will)
Muscle Fibers
- Long, thread-like appearence.
- Muscle cells in these fibers contain MULTIPLE NUCLEI pressed against side of plasma membranes.
Muscle Fibers contain ______ Structures:
Sarcolemma - cell membrane
Myofibrils - fundamental role in muscle contraction
Sarcoplasmic Reticulum ( endoplasmic reticulum) - activates muscle contraction mechanism when a muscle fiber is stimulated.
Myofilaments - proteins that for light & dark bands that makes muscle appear striated.
Transverse tubules - opens to the outside of muscle fiber & contain extracellular fluid, activates the muscle contraction mechanism when muscle fiber is stimulated.
Muscle Attachment
Skeletal muscle may appear in 1 of 2 ways
Direct Attachment
Muscle Fibers merge w/ the periosteum of bone to form a strong attachment.
Indirect Attachment
Epimyosium extends past the muscle as a tendon, which merges w/ the periosteum.
Muscle Movement
- Prime movement
- Synergists
- Antagonists
Prime mover
Main muscle triggering the movement
Synergists
Muscles that assist the Prime Mover.
Antagonists
Muscles that oppose that action of the Prime Mover. Typically works to moderate speed/ range of movement to prevent injury.
How Muscles and Movement Work Together
- When the Prime Mover contracts, the Antagonist must relax to give the Prime Mover control.
-Prime Mover for one movement = Antagonist for opposite movement.
Hypertrophy
Enlarging muscles ( ex. weight lifting).
Atrophy
Shrinking muscles (from lack of use).
Aerobic
Endurance (endurance exercise) stimulates the growth of blood vessels in the muscle. ( increases supply of oxygen & glucose for ATP production)
Slow Twitch (Type 1)
a slower reaction to stimuli.
- contains a lot of mitochondria & rich blood supply for efficiency at using oxygen to generate ATP of energy
- responds slower but fires for a longer time before becoming fatigued.
Fast Twitch (Type 2)
Better @ generating short bursts of speed/strength.
- Smaller amts of mitochondria & a poorer supply of blood, but can absorb/release calcium quickly.
- fatigues quicker than twitch fibers.
Muscle Fatigue
Muscle loses ability to contract during strenuous exercise = fatigue.
- arises usually from electrolyte imbalances & decreased ATP levels
- muscle cramps are due to lack of ATP required to return calcium ions back to the Sarcoplasmic reticulum so muscle fibers can relax.
Muscles are named according to:
- Size
- Shape
- Location
- Number of origins
-Direction of muscle fibers
-Action/Function
Size of Muscles:
MAXIMUS- largest
MINIMUS- smallest
MAJOR- large
MINOR- small
LONGUS- longest
BREVIS- shortest
Shape of Muscles
DELTOID- triangular
RHOMBOID- diamond shaped
SERRATUS- sawtoothed
TRAPEZIUS- trapezoidal
Pectoralis
Chest
Brachio
Upper arm
Gluteus
Buttock
Fermoris
Femur
Sterno
Sternum
Cleido
clavicle
Mastoid
mastoid process
Digiti
finger or toe
Pollicis
thumb
Number of Origins
Biceps- 2 origins
Triceps- 3 origins
Quadriceps- 4 origins
Direction of Muscles
Rectus- straight
Transverse- across
Oblique- diagonal
Action of Muscles
Adductor- adducts
Abductor- abducts
Flexor- flexes
Extensor- extends
Leviator- elevates
Muscle Contraction
1) impulse reaches end of motor neuron, causing small vesticles to fuse w/ cell membrane & release a neurotransmitter: ACETYLCHOLINE (ACh) into the synaptic cleft.
2) ACh quickly diffuses across synaptic cleft, stimulating receptors in the sarcolemma, sending an electrical impulse over the sarcolemma & inward along the T-Tubules.
- causes the sacs in the sarcoplasmic reticulum to release calcium.
3) Calcuim binds with the tropin on the actin filament to expose attachment points.
- in response, the myosin heads of thick filaments grab onto thin filaments and muscle contraction occurs.
Muscle Relaxation
1) when nerve impulses stop arriving @ neuromuscular junction, ACh is no longer released.
2) An enzyme breaks down any remaining ACh while calcium ions are pumped back into the sarcoplasmic reticulum.
2) w/ calcium removed, troponin and tropomyosin again prevent the myosin heads from hooking onto thin filaments & muscle fiber relaxes.
Calcium & ATP
*calcium in required to prevent tropmyosin & tropin ( 2 protein molecules entwined in actin filament) from blocking the sites where the myosin head attaches.
*ATP provides energy which allow myosin heads to release their grip on actin filaments. The ATP splits, giving the myosin fuel to form new cross bridges.
Strength of contraction
The nervous system controls strength of a contraction by:
Altering the FREQUENCY of the stimulus & altering the INTENSITY of the stimulus.
Stimulus Frequency
- When a muscle contracts several times in a row, the last contraction will be stronger than the first.
(the sarcoplasmic reticulum doesn’t have time to completely reabsorb the calcium) - When the impulse releases the muscle fibers even faster. the fibers don’t have a chance to completely relax before the next impulse arrives.
( as a result, each subsequent contraction builds on the previous one.)
Stimulus Intensity
A strong stimulus may stimulate all fibers in a motor nerve, causing nerve fibers to call on their accompanying muscle fibers to contract.
In contrast, a weak stimulus stimulates only a few nerve fibers, which creates a weaker response.
