Muscle Histology III Flashcards
What is rigor mortis?
Hardening of the muscles and stiffening of the body
At a cellular level, what happens during rigor?
No More ATP is being produced you you cannot get Ca2+ out of the sarcoplasm back into the terminal cisternae of the SR. Cross bridging is promoted, but no ATP is produced to release the heads of the myosin from the F actin active sites.
When does rigor set in? When does it abate?
3-4 hours post mortem
48-60 hours with the beginning of decomp
What kind of paralysis does curare cause?
Flaccid
What is the mechanism of curare?
Binds to ACh receptors
Mimics ACh, so ACh itself cannot bind to receptors
What is the mechanism of botulism?
Prevents release of ACh at neuromuscular junction
Botulin toxin
No ACh in synaptic gap
What kind of paralysis does botulism cause?
Flaccid paralysis
What is the mechanism of tetanospasmin?
Blocks glycine release (inhibiting)
What kind of paralysis does tetanus cause?
Spastic
What is the mechanism of organophosphates?
Inhibits AChE by binding to AChE
Muscles cannot relax
What kind of paralysis is caused by pesticides?
Spastic
What is the mechanism of myasthenia graves?
An autoimmune disease
Antibodies bind to ACh receptors, damaging them
What kind of paralysis is caused by myasthenia graves?
Flaccid paralysis
What is the mechanism of polio?
A virus destroys motor neurons in brainstem and ventral horn of the spinal cord
What kind of paralysis comes from polio?
Flaccid
Muscles cannot turn all of the energy they consume into________ work, so they produce _____.
Mechanical
Heat
Most body heat is due to the ________ of skeletal muscle
contractions
When the body temperature falls, the _________ makes us shiver to increase heat up to _____%.
Hypothalamus
400%
In muscle histology, in what 3 places is ATP needed?
1- To bind myosin head to actin
2- To release myosin head from actin
3- To reconcentrate Ca2+ in the terminal cisternae
For muscle contraction, what must be bound to myosin?
An ATP
How is the ATP used by the myosin head?
An enzyme is present in the head ( myosin ATPase) hydrolyzes this ATP
Energy released by this process activates the head which shifts into an extended high energy position
For a muscle to relax, _____ breaks down any remaining ACh.
AChE
What is calsequestrin?
A protein that binds to Ca++ for storage.
What is muscle tone?
The CNS continually monitors and adjusts the length of the resting muscles, maintaining a state of partial contraction
In which three areas is an O2 debt repaid?
1- O2 bound to myoglobin
2- O2 bound to hemoglobin
3- O2 dissolved in blood plasma
What is aerobic cell respiration?
Requires O2, yields 38 ATP
What is anaerobic cell respiration?
Doesn’t require O2, yields 2 ATP
What generates lactic acid?
Anaerobic cell respiration
What are the two types of skeletal muscle fibers?
SO (slow oxidative) or slow-twitch or red fibers and
FG (fast glycolic) or fast twitch or white fibers
Which muscle fiber is well adapted for aerobic respiration and have abundant mitochondria, many surrounding blood vessels?
SO
______ fibers have lots of myoglobin and _____ fibers have little myoglobin/
SO
FG
What are some examples of SO muscles?
Postural muscles, respiration muscles, muscles for mastication
What kind of person has a greater % of SO muscles?
Distance runners
FG muscles are adapted for anaerobic respiration, they have high _____ reserves
glycine
FG muscles contract more ________, and produce ________ as a byproduct.
Rapidly
Lactic acid
What kind of person has more FG fibers?
Basketball players and sprinters
What is an isotonic contraction?
Contraction with a change in length, but not tension
What are the two types of isotonic contraction?
Concentric Isotonic
Eccentric Isotonic
What is isotonic concentric contraction? An example?
A muscle shortens as it maintains tension
Ex: “Lift up baby”
What is isotonic eccentric contraction? An example?
A muscle lengthens as it maintains tension
Ex: “Put down baby”
What is isometric muscle contraction?
Contraction without a change in length
“Tension building up to allow you to lift something”
What kinds of muscles have isometric contraction?
Found in postural muscles- “keeping us from sinking to the floor”
Which tissues have myocytes in them?
Cardiac and smooth muscle, only
Which muscle types contain sarcomeres?
Skeletal and cardiac
How do cardiac cells communicate with the cell next door?
Thru gap junctions and intercalated discs
Describe the SR of the cardiac cell
Sarcoplasmic reticulum is less developed and the T tubules are larger
Larger T tubules allow cardiac muscle to….
Admit more Ca++ from the ECF
What is the pacemaker of the heart?
The SA node
The heart uses ________ respiration and is rich in _______ and glycogen.
Aerobic
myoglobin
In cardiac cells this body takes up approximated 25% of the interior volume
Mitochondria
The heart is highly resistant to fatigue, and does not do __________.
Recruitment
Where is smooth muscle found?
Found as circular and longitudinal layers in GI, urinary, and reproductive
Why doesn’t smooth muscle have sarcomeres?
Thick and thin filaments are present, but they are not aligned with each other, so they do not produce visible striations or sarcomeres
How does smooth muscle get Ca++?
From the ECF. There are no T tubules.
Which muscle type is capable of mitosis hyperplasia?
Smooth
Why is mitosis and hyperplasia advantageous to smooth muscle?
An organ like the pregnant uterus can grow by adding more myocytes;
Smooth muscle heals well
How much can smooth muscle stretch?
A lot.
Uterus: 8x
Bladder: 2.5x
How is smooth muscle innervated?
Some smooth muscle does not have a nerve supply, and instead contracts due to ANS, temperature, hormones, or as a response to its own stretching
