Muscles Flashcards
to move the body and things within the body –> Contraction
Function of Muscle
Name the 3 types of Muscle
Smooth, Skeletal and Cardiac
One muscle Cell
Fiber
plasma (cell) membrane of muscle cell/fiber
Sarcolemma
cytoplasm of muscle cell/fiber
Sarcoplasm
smooth endoplasmic reticulum of muscle cell, storage area for fiber
Sarcoplasmic reticulum
: prefix for muscle terms (e.g., myocyte = muscle cell)
Myo
Not striated
Cells are spindle shaped
Centrally located nucleus
Regulated by the ANS
Visceral organs
Involuntary: not under conscious control
Found in hollow viscera, eye, attached to hairs (arrector pili)
Smooth Muscle
Found only in the heart
Regulated by ANS
Striations from light and dark bands
Elongated branching cells
Ends of the cells join at intercalated disc
Highly specialized cell membrane –> facilitates transmission of electrical impulse
Cardiac Muscle
Makes up majority of muscle mass in body
Striated
Do not branch, no intercalated disk
Innervated by cranial and spinal nerves
Multinucleated cells
Peripherally located nuclei
Voluntary: usually contracts only under conscious control
Exception: reflexes
Required nerve impulse for stimulation
Skeletal Muscle
least movable attachment, usually proximal and/or medial
Origin
most movable attachment, usually distal and/or lateral
Insertion
___________ of the muscle brings origin and insertion closer together
Contraction
Skeletal muscle types—action
Extensors, Flexors, Adductors, Abductors, Constrictors (sphincters), Dilators, Agonist and Antagonists
extend or increase angle between body parts
Extensors
flex or decrease angle between body parts
flexors
pull limb toward median plane
Adductors
move limb away from median plane
Abductors
surround circular opening, close it when they contract
Constrictors (sphincters)
surround circular area, open it when they contract (uncommon in mammals)
Dilators
muscles that promote a given movement
Agonists
muscles that inhibit a given movement, prevent hyperextension, etc.
Antagonists
More myoglobin (Mb): oxygen storage
More glycogen: glucose storage
More mitochondria: ATP production
Slow twitch: slower to contract but fatigue slowly
Red muscles are used for endurance
Red Muscle Fibers
Fast twitch: contract quickly but fatigue faster
Example: Rabbits have a quick burst of activity, not for endurance.
White Muscle Fibers
Parallel, Pennate, Fleshy, Oblique
Muscle Fibers Arrangements in Muscle
tendon comes off ends of fibers to attach to bone
Example: pectoralis muscle
Parallel Muscle Shape
feather-like with central tendon, wide at the top and converges at the tendon
Example: biceps
Pennate Muscle Shape
appears to attach directly to bone, but has short (microscopic) tendons between muscle fibers and bone
Fleshy Muscle Shape
circular or convergent (abdomen)
Oblique Muscle Shape
Loose C.T. around muscle cells
endomysium
Loose C.T. around muscle bundles (fascicles) of muscle cells
perimysium
Dense irregular to regular C.T. around whole muscle
epimysium
Endomysium, perimysium and epimysium all meet at ends (or center for pennate muscles) to become
Tendons to attach to bones –>transfers movement and energy of contraction to bones
Endomysium, perimysium and epimysium are…..
C.T. harnessing muscle
Muscle cell (fiber) composed of
Myofibrils
These are composed of protein myofilaments
and have Myosin and Actin
Myofibrils
thick filament
Myosin
thin filament
Actin
Arrangement makes units called ______ along myofibril
Banding pattern—striations
sarcomeres
Banding pattern
striations
length of myosin filament, includes overlap with actin, stains dark
Always he same length
A band
actin only, does not include area of overlap with myosin, stains light
Change with contractions and relaxation (length)
I band
myosin only without actin overlap
Change with contractions and relaxation (length)
H band
ends of sarcomere, connects actin filaments
Z line
middle of sarcomere, connects myosin filaments
M line
Protein filament
Individual myosin filaments resemble golf clubs, fit together with heads at ends sticking out all around
No heads in middle of filament
Head is heavy meromyosin (HMM)
Neck is light meromyosin (LMM)
Myosin Filament
Protein myofilament
3 parts
Individual actin molecules are globular (G-actin) and fit together like beads on a string –> 2 strands of G-actins twisted around each other make the actin filament
Groove of actin filament (between actin strands) has a different strand of protein –> tropomyosin
Tropomyosin has a globular protein, troponin, spaced along it
Has binding sites for myosin heads along filament, in relaxation tropomyosin covers these binding sites so that actin and myosin do not interact
Actin Filament
Synapse of a motor neuron on a skeletal muscle fiber
Cell bodies of motor neurons in ventral horns of spinal cord
One motor neuron usually branches to synapse on many skeletal muscle cells
One motor unit: one motor neuron + all skeletal muscle fibers it innervates (synapses with)
Neuromuscular junction or motor endplate
