Musclular System Flashcards
What is the Study of Muscles?
Myology
What characteristics make muscles highly specialized?
Excitability, Contractility, Elasticity
Skeletal Muscle
Structure: striated, multinucleated
Function: move and stabalize skeleton
Location: around bones
Control: voluntary
Cardiac Muscles
Structure: striated with intercaliated discs
Function: cirrculate blood
Location: heart
Control: involuntary
Smooth Muscle
Structure: smooth and spindle shaped
function: controls diameter of passageways, and moves food, urine, and reproductive tract secretions.
Location: around blood vessesl and walls of hollow organs
Control: involuntary
Which type of muscle is included in the muscular system?
Skeletal Muscle
What attaches skeletal muscles to bone?
Tendons
Five major functions of skeletal muscle:
- produce body movements
- stabalize body position
- storing and moving substances in the body
- heat production
- store nutrient reserves
Layers of connective tissue:
Epimysium- around whole muscle
Perimysium- around muscle fasical
Endomysium- around muscle fiber
Where are myosteliite cells found and what is their function?
in endomysium, stem cells that repair damages muscle tissue
Muscle fascicle
groups of muscle fibers
What makes a Tendon?
extension of connective tissue layers
Aponeuroses
flat thick tendon
What stem cells fuse to form muscle fibers?
myoblasts
What is the sarcolemma and where is it found?
Cell membrane on outside of cell
What is sarcoplasm
like cytoplasm
Where is the sarcoplasmic reticulum located and what is its function?
the organelle that surrounds myofibril. stores and releases calcium for muscle contraction.
Transverse Tubules and their function
network of tubules in sarcolemma used to convey electrical impulses for muscle contraction.
Myofibril, what is it composed of and how many are in a muscle fiber?
bundles of proteins myofilaments
what are myofilaments and where are they found?
protein filaments responsible for muscle contraction
Actin= thin
myosin= thick
What is a sarcomere?
smallest contractile unit of muscle fiber; basic functional unit of muscle fiber
atrophy vs. hypertrophy
atrophy= muscle wasting
hypertrophy= muscle increase in size
organization of a muscle
epimysium, whole muscle, perimysium, muscle fascicles and fibers, endomysium, sarcolema, muscle fiber, sarcoplasmic reticulum, myofibril, myofilaments
z disc
anchor thin filament
m line
anchor thick filament
a band
contain thick filaments and zone of overlap
I band
contain only thin filaments
troponin
controls tropomyosin and calcium binds to it
tropomyosin
lies in actins groove and acts to block myosin from attaching to actin’s active site
myosin
motor protein with short rods that have globular heads, forms cross-bridges during contraction
Sliding filament mechanism
- action potential leads to the release of calcium by sarcoplasmic reticulum. calcium binds to troponin producing a change in the orientation of the troponin- tropomyosin complex that exposes the active sites on actin
- cross-bridges form when myosin heads bind to active sites
- myosin heads pivots toward the m line actin slides toward m line and sarcomere contracts
- ATP gives myosin head energy to unattach and re-set
Rigor mortis
time period of muscle rigidity following death
Neuromusclular junction
synapse between somatic motor neuron and a skeletal muscle fiber
presynaptic cell
neuron recieve messege
postsynaptic cell
neuron send message
synapse
site of communication between nerve cell and another cell
motor unit
a somatic motor neuron and all the muscle fibers it innervates
motor end plate
region of sarcolemma and opposite of synaptic terminals
synaptic terminal
expanded tip of axon at NMJ
synaptic cleft
space that separates synaptic terminal from motor end plate
physiology at NMJ
- action potential travels down axon to synaptic terminal
- opens calcium channels in synaptic terminal which causes a sudden change in the terminal’s membrane potential
- Ach diffuses into synaptic cleft. Ach inds to receptors on surface of sarcolemma at the motor end plate. This increases the sarcolemma’s pereability to sodium. Sodium rushes into sarcoplasm
- sudden rush of sodium into sarcoplams results in an action potential in the sarcolemma.
What enzyme breaks down acetylcholine?
Acetylcholinesterase
What produces the botulinum toxin and what affect does it have?
caused by bacterium clostridium botulinum. Blocks release of synaptic vesicles at NMJ
affects of nerve gas and insecticides
inhibits AChE and causes potentially fatal paralytic convulsions
affect of cobra toxin and curare
blocks ACh receptors
What three factors are involved in determining how long a muscle contraction will last?
- duration of neural stimulation
- number of free calcium ions in sarcoplasm
- availability of ATP
Three ways skeletal muscle fiber tension can be increased
- changes in sarcomere length
- stimulus frequency
- motor unit recruitment
which sarcomere length provides the maximum ability to generate tension?
Intermediate fiber resting length
What is treppe?
When stimulation occurs immediately after relaxation phase
what is wave summation and tetanus?
when stimulus frequency is greater than duration of single twitch
what is recruitment?
an increase in the number of active motor units
motor unit size and function
size indicates how fine the control of movements will be
What are the three sources of ATP in muscle fibers
- Glycolysis
- Aerobic metabolism
- Creatin phosphate
Which molecule stores most of the glucose in muscle fibers?
glycogen
Which provides the most ATP?
Aerobic metabolism
What does excessive pyruvate get converted into?
lactic acid. decreases pH and causes fatigue
Slow, fast, and intermediate muscle fibers
Slow:
Fatigability= fatugue resistant
contraction speed= slow
diameter size= 1/2 diameter of fast fibers
amount of myoglobin, mitochondria, and blood capillaries= ^
Fast:
Fatigabuility= fatigable
contraction speed= fast
diameter size= large
amount of myoglobin, mitochondria, and blood capillaries= low
why do fast fibers have a white appearance and slow fibers have a red appearance?
slow more blood flow
can you train to increase the effectivness of each fiber?
yes
What is muscular dystrophy and myasthenia gravis?
Dystrophy- congenital diseases that produce progressive muscle weakness and deterioration
MG- progressive muscular weakness due to loss of acetylcholine receptors at motor end plate.
