Musculoskeletal Flashcards
t-tubules of skeletal muscle are extensions of what?
the sarcolemma
an ‘a’ band within a skeletal muscle fiber contains what?
actin and myosin filaments
what role does calcium play in muscle contraction?
it binds to troponin allowing exposure of the actin binding sites
compared to skeletal muscle cells, cardiac muscle cells are?
autonomic
what are the characteristics of muscle?
excitability, contractibility, extensibility, and elasticity
what are the primary functions of muscle?
provide motion, maintain posture, and generate heat
what are the types of muscle?
skeletal, cardiac and smooth
multiple nuclei and long fiber like shape; very long and very thin
skeletal muscle - voluntary, ambulation of skeleton
one nuclei, tapered ends and spindle shaped
smooth muscle - involuntary, based on needs of the body
one nuclei with a branching network of cells and intercalated disks connecting cells
cardiac muscle - involuntary
well-defined group of cells surrounded by fibrous connective sheath
epimysium
attach to bones by fibrous tissue bands
tendons
attach to bones or muscles by broad sheets of fibrous tissue
aponeuroses
the most prominent aponeuroses that runs lengthwise between the muscles on an animal’s ventral midline
linea alba
more stable site, does not move when muscle contracts
origin of muscle attachement
site that undergoes the most movement when a muscle contracts
insertion site of muscle attachement
why are origin/insertion sites important?
to determine if either is the cause of an immobile of painful joint, and they are used as a guide in surgery, cutting, retraction or used in closure or can be affected by the procedure
types of skeletal muscle actions
- agonist
- antagonist
- synergist
- fixator
directly produces a desired movement
agonist aka prime mover
directly opposes the action of the agonist
antagonist
contracts at the same time as agonist to assist its action
synergist
stabilizes joint to allow other movements
fixator
hold components of muscle fibers together, contain blood vessels and nerves, and are continuous with tendons or aponeuroses
connective tissue layers
order of muscle structure
outside in:
- epimysium
- perimysium
- endomysium
- fascicles
- muscle fiber
- myofibril
fibrous outside layer composed of tough collagen fibers that enclose everything else
epimysium
composed of reticular fibers and thick collagen fibers; separates groups of fascicles
perimysium
composed of fine, reticular fibers; separates individual fascicles within their groups
endomysium
groups of muscle fibers
fascicles
composed of myofibrils; multinucleate
muscle fibers
form interior muscle fibers; made up of many protein filaments; many sacromeres lined up end to end equals one
myofibrils
muscle cell membrane
sarcolemma
a storage organelle for calcium ions
sarcoplasmic reticulum
the basic contracting unit of skeletal muscle
sarcomere
what are the two primary protein filaments responsible for contraction?
thick, dark myosin and thin, light actin
a disc on each end of a sarcomere; discs can be shared among sarcomeres
z line/disc
light colored bands of a sarcomere made up of thin actin filaments
i bands
where the thick myosin filaments and thin actin filaments overlap
a bands
the light colored area located in the middle of the a band, made up of only myosin filaments with no overlapping actin
h bands
where the terminal portion of a motor neuron axon meets a muscle cell membrane, separated by a synaptic cleft
neuromuscular junction
what neurotransmitter is contained in the synaptic vesicles at the end of nerve fibers?
acetylcholine
one nerve fiber and all the muscle fibers it innervates
motor unit
if its a small, delicate movement of muscles
its a few muscle fibers per motor unit
if its a large, powerful movement of muscles
its a huge number of muscle fibers per motor unit
shortening of all sarcomeres in a muscle fiber
muscle contraction
when stimulated, individual muscle fibers contract completely or not at all
all or nothing principle
a single muscle fiber contraction; contractions out of sync with each other
twitch contraction
ATP provides energy to allow sliding of actin and myosin filaments, ATP converts to ADP and back to ATP, catabolism of glucose and oxygen help produce ATP and CP
chemistry of muscle contraction
creatinine phosphate; helps convert ADP back to ATP
CP
when ATP has one phosphate group split off
ADP - adenosine diphosphate
glucose stored in muscle
glycogen
oxygen stored in muscle attached to large protein molecules; red in color and can release oxygen to resupply the muscle fiber when needed
myoglobin
spasmodic muscle contractions that increase heat production
shivering
mechanisms to eliminate excess heat
panting or sweating
a system of communication that fasten cardiac muscle cells together
intercalated disks
cardiac muscle contractions
rapid and wavelike; contract with no external stimulation
part of the cardiac conduction system; located in the wall of the right atrium; generates impulse to start each heartbeat
sinoatrial node aka SA node
nerve supply to cardiac muscle
does not need to initiate contractions
sympathetic nervous system to cardiac muscle
stimulates heart in fight or flight response when an animal feels threatened
parasympathetic nervous system to cardiac muscle
inhibits cardiac function, making the heart beat slower when it is at rest
smooth muscle main forms
- visceral
- multi-unit
visceral smooth muscle
large sheets of cells in walls of some hollow organs like the bladder or gi tract; contracts in large waves and without external stimulation
multi-unit smooth muscle
small, discrete groups of cells found where small delicate contractions are needed like iris, blood vessels, lungs; contraction requires impulses from autonomic nervous system
actin and myosin filaments arranged as small contractile units that crisscross the cell
smooth muscle anatomy
sympathetic nervous system to smooth muscle
decreases activity to move blood to heart and skeletal muscles and away from urinary and gi tract for intense physical activity
parasympathetic nervous system to smooth muscle
increases activity when animal is relaxed and resting to help supply nutrients
atp use in the muscle cell is required to what?
- energize the power stroke of the myosin cross bridge
- disconnect the myosin cross bridge from the binding site on acting after the power stroke
- provide energy to the calcium ion pump to restore calcium in the cisternae of the sarcoplasmic reticulum
composed of adenine nucleotide with two additional phosphate groups attached by a high energy bond
atp
a considerable release of energy from atp, occurs when a terminal high-energy bond is broken by a hydrolytic enzyme produces adp and phosphate
atp hydrolysis
occurs via hydrolysis of creatine phosphate (cp)
atp synthesis
what is used for energy by a muscle cell and also used in the production of atp?
glucose
what are the end products when glucose is broken down by glycolysis?
- 2 atp and 2 molecules nadh that produce 4 atp molecules
- 2 pyruvic acid molecules
pyruvic acid, with the help of electrons carrying enzyme nadh, convert pyruvic acid to lactic acid by adding a phosphate molecule to glucose
anaerobic metabolism
oxygen for this process is available directly from the blood or from myoglobin
aerobic metabolism
enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules.; regions within the muscle cell store calcium in turn increase the capacity of the sarcoplasmic reticulum to release calcium
terminal cisternae
deep cavity of the sarcolemma, which allow depolarization of the membrane to quickly penetrate to the interior of the cell
t-tubules
latent twitch, contraction, and relaxation
muscle twitch phases
