Muscular Flashcards
3 types of muscle
-skeletal
-cardiac
-smooth
What do all muscles do?
Generate force
What 4 things do all muscles have in common?
1) excite (react to stimuli)
2) contract (shorten)
3) extend (stretch)
4) elastic (go back to original shape)
What are functions of skeletal muscle?
1) Maintain posture
2) stabilize joints
3) provide movement
4) generate heat
Are skeletal muscles voluntary or involuntary?
Voluntary
What do skeletal muscles attach to?
Bone or skin (face)
What is a muscle cell called?
Myocyte (fiber)
What is a fascicle?
Bundled muscle fibers (myocytes)
What covers fascicle?
Perimysium
What membrane covers groups of fascicles to form muscle belly
Epimysium
What membrane covers bundles of myocytes?
Endomysium
All connective tissue extends beyond the muscle belly to form what?
Tendons
What is a muscle origin
Attachment to non-moving bone
What is muscle insertion?
Tendon that attaches to bone that moves
3 features of a skeletal myocyte
1) Long cylinder
2) Multiple nuclei
3) striated
What is the myocyte membrane called
Sarcolemma
What is the cytoplasms of a myocyte
Sarcoplasm
What is sarcoplasmic reticulum?
Smooth endoplasmic reticulum that stores calcium
What are T tubules?
Transverse tubules that run from the sarcolemma to center of muscle and transport ions
What are myofibrils?
Stacks of long fibers/filaments in sarcoplasm
What do myofibrils contain?
Actin and myosin
What are sarcomeres?
Short bundles of actin and myosin
True/False:
Each myocyte contains 100s of sarcomeres
True
What part of the brain controls muscle movement?
Primary motor cortex
What part of brain contains primary motor cortex?
Cerebral cortex
What starts a muscle contraction?
Action potential
Where is upper motor neuron
Brain and spinal cord
Where is lower motor neuron?
Anterior horn of spinal cord
Where does signal go after the lower motor neuron?
Down the axon
What are the branches of the axon called?
Axon terminals
What do axon terminals connect to?
Muscle fibrils
What is the place where axon terminals meet myofibrils called?
Neuro-muscular junction
Where one lower motor neuron branches at axon and meets multiple muscle fibers is called?
Single motor unit
On average, how many muscle fibers does one lower motor neuron innervate?
150
How many fibers does one lower motor neuron innervate for precise movement? Small motor unit
10-15
How many fibers does one lower motor neuron innervate for less precise movement? Large motor unit
<2000
4 features of cardiac muscle
1) striated
2) shorter than skeletal
3) 1-2 nuclei
4) involuntary
What is a cardiac muscle cell called?
Cardiomyocyte
What covers cardiomyocyte?
Endomysium (no perimysium or epimysium)
What structures do cardiomyocytes have?
1) t tubules
2) sarcomeres
3) sarcoplasmic reticulum
What binds cardiomyocytes to each other?
Intercalated disks.
What is function of intercalated disks?
1) anchor to keep cells together during contraction
2) gap junctions allow flow of ions between cardiomyocytes
3) allows heart to work as a unit
What are pacemaker cells?
They control cardiac muscle
Where are pacemaker cells found?
In heart muscle walls
How do pacemaker cells generate action potential?
Rapid shifts in ions through intercalated disks.
What do pacemaker cells demonstrate?
Automaticity (able to generate action potential)
What 2 things control pacemaker cells?
1) nerves
2) hormones
What shape are smooth muscle cells?
Spindle shaped (fusiform)
How many nuclei do smooth muscle cells have?
One
Does smooth muscle have actin and myosin?
Yes
Does smooth muscle have sarcomeres?
No
What membrane surrounds groups of smooth muscle cells?
Endomysium
What does smooth muscle have instead of t-tubules?
Invaginations called caveolae
Does smooth muscle have sarcoplasmic reticulum?
Yes, but less extensive than skeletal and cardiac
What 3 things can trigger smooth muscle?
1) Nerves
2) hormones
3) local factors (muscle wall stretch)
3 parts of neuromuscular junction
1) presynaptic membrane (axon terminal membrane)
2) postsynaptic membrane (muscle membrane)
3) synaptic cleft (gap between)
Another name for post synaptic membrane?
Motor end plate
What starts an action potential?
Sodium travels thru nerve and opens Voltage Gated Ca+ channels in axon
How man ACH molecules bind to 1 nicotinic receptor?
2
When ACH binds to nicotinic receptors, what happens?
Channels open in the post synaptic membrane and Na+ ions flood in to make it less negative (from -100 to -60)
What is depolarization in muscle called?
End plate potential
What is slow twitch muscle fiber?
Slow, oxidative
2 subcategories of Fast Twitch muscle
1) fast oxidative
2) fast glycolitic
What determines which type of fast twitch muscle is activated?
1) speed of contraction
2) metabolic pathways used to make ATP
True/False: most muscles have both types of fibers?
True
What does the myosin head contain?
ATPase
What does the release of ATPase from the myosin head do?
Breaks ATP down into ADP+P which releases energy
How does the release of energy from the breakdown of ATP affect myosin head?
Causes it to pop up and bind to G-Actin
What happens when myosin head binds to g-actin?
Releases energy and catapults actin at binding site; creates “power stroke”
What does a power stroke do?
Slides actin over myosin and causes a contraction
What determines the speed of contraction?
How quickly ATPase enzyme breaks down ATP
What kind of ATPase is in slow twitch muscle?
ATPase that hydrolyzes ATP slowly
Does ATPase in fast twitch muscle hydrolyze ATP quickly or slowly?
Hydrolyzes ATP quickly
What is the main source of ATP?
Glucose (stored as glycogen)
What process stores glucose as glycogen in muscles?
Glycogenesis
What is Glycogenolysis?
Breakdown of glycogen to glucose in muscle
What process makes glucose into ATP?
Glycolysis
What does glycolysis produce when it breaks down glucose?
2 ATP and 2 pyruvate
What process does pyruvate go thru if mitochondria and oxygen are available?
Aerobic respiration
What is pyruvate converted to during aerobic respiration?
Acetyl-COA
What happens to acetyl-COA when it enters the mitochondria?
Makes NADH via “citric acid cycle”
What process does NADH drive in the mitochondria?
Oxidative phosphorylation
What does oxidative phosphorylation in the mitochondria yield?
38 ATP per glucose molecule
What is anaerobic respiration?
Absence of oxygen and mitochondria
What is another name for anaerobic respiration?
Anaerobic glycolysis
What does anaerobic glycolysis produce from glucose?
Pyruvate + 2 ATP
What happens to excess pyruvate after anaerobic glycolysis?
Converts to lactic acid and transferred to liver via blood
What does the liver do with lactic acid?
Recycles to pyruvate
What does liver do with pyruvate after breaking down lactic acid?
Combines it with 6 ATP to make glucose
Where does liver send glucose that it made from pyruvate and ATP?
Muscles and organs
What is another name for slow oxidative fibers?
Slow twitch or type I
3 Features of slow twitch
1) small
2) hydrolyzes ATP slowly
3) aerobic
What is myoglobin?
Red pigment that binds and stores oxygen
Qualities of slow twitch
1) weak contraction/low # sarcomeres
2) high myoglobin (Slow Red)
3) low glycogen storage
4) makes 38 ATP
Another name for fast oxidative fibers
Type IIa
Fast oxidative are large and strong, true/false
True
Fast oxidative are also called Fast Red Muscle
True
What two ways do fast oxidative fibers make ATP?
1) Oxidative phosphorylation
2) anaerobic glycolysis
Another name for Fast Glycolytic fibers
Type IIx or White Muscle Fibers
What is muscle tone?
Force of muscles applied at rest
What is muscle tension
Force thru fibers during action
What is M line?
Center line where myosin attach
What are z bands
Outsides borders of sarcomere where actin fibers attach
What are z bands made of?
Alpha actin proteins
What is I band?
Where actin doesn’t overlap myosin (light)
What is A band?
Length of myosin including overlap with actin
What is H zone?
Where myosin doesn’t overlap actin (not as dark)
What 2 bands shorten during muscle contraction?
H band and I band
What is it called when myosin head attaches to g-actin?
Cross bridge formation
What 5 things determine force of contraction?
1) size of muscle fiber
2) # of active muscle fibers
3) frequency of stimulation
4) length of sarcomeres
5) force (speed of contraction)
What does fast speed of contraction produce?
Low force
What is isotonic contraction?
Muscle length changes but tension stays same; builds strength
What is isometric?
Tension changes but length stays the same; builds power
Longest muscle in the body?
Sartoreus
How many muscles in body?
~600
What does infraspinatus muscle do?
Rotator cuff
Teres major does??
Rotate humerus and assist lats
Tibialis
Front of calf
Serratus
Connects at ribs 1-8
Are slow twitch strong or weak?
Weak
Do slow twitch have high or low concentration of myoglobin?
High
Do slow twitch muscle fibers have high or low storage of glycogen?
Low
Do slow twitch fibers have a large number of sarcomeres?
No; low # of sarcomeres
How many ATP molecules do slow twitch make?
38 ATP
