Lecture 7 Test 3 Flashcards
Skeletal muscle force generation
works when you have a muscle stretched to its natural state and a contraction force is measured after an action potential.
It won’t work if the muscle is over stretched or under stretched
(heart) Load/contraction velocity
increased load = decreased muscle contraction speed
What is quantal summation?
Number of motor units activated to produce more force of contraction
What is temporal summation?
When you reach max Force generation compared to rate stimulation. Ex. 40 Hz caused a continuous contraction (tetany)
What is tetany?
Ex. 40 Hz (supra maximal voltage)
When the AP aren’t able to go back to resting potential and Ca++ aren’t able to fully return into the SR. Causing another AP while previous Ca++ are still in the cytoplasm, resulting with continued contraction without rest.
What is atrophy?
When muscles get smaller after no use.
Which part of the muscles are affected by atrophy first?
Microfibrils
Can heart muscles replace dead muscles?
Yes and we don’t know this is happening
What happens to vascular beds when you workout?
When you have big healthy muscles, vascular beds get big as well.
How much skeletal muscles are there in a body?
40% of body mass
How many smooth muscles are there in a body?
10% of BW
Where can you find smooth muscles?
ex. airway, intestines, eyes, blood vessels
Compare the cross bridge process of skeletal muscles to smooth muscles.
in smooth muscles, slower pace, causing “latching” d/t the myosin head takes a longer time to release from the actin
T/F: Smooth muscles are a lot stronger than skeletal muscles.
True
smooth muscle strength is similar to what animal?
Boa constrictor strength with the continuous contraction
Smooth muscles are connected to their neighbors by
Gap junctions
Ratio for smooth muscle
Actin: Myosin
20:1
Skeletal muscle ratio
Actin:Myosin
2:1
(Skeletal muscle) actin filament anchor via
Z disk
(Smooth muscle) actin filament anchor via
Dense bodies
Skeletal muscles have huge stores of?
Calcium in the SR
How are smooth muscles depolarized?
It has very leaky channels for calcium and sodium
V-G Ca ch
Ligand gated Ca ch
Some under developed SR
What happens if your Ca++ is 0??
No BP, No Ca++ induced heart beat, Smooth muscles won’t contract, no tone.
What is a visceral smooth muscle?
Unitary smooth muscle = functions as a unit spreading calcium amongst each cell via gap junctions
Ex. of visceral smooth muscle
Intestines
What is a multi unit smooth muscle and what is it used for?
Used for fine tune movements. Not dependent on gap junctions but is dependent on a neurotransmitter
Ex. of multi unit smooth muscle?
Ciliary muscles, Iris
Ex. of a hybrid of skeletal and visceral smooth muscle?
Esophagus
Anatomy of a small artery (unitary smooth muscle)
Endothelium lined on the inside.Smooth muscle on the inside and connective tissue on the outside (Adventitia) structural support.
What’s the difference in anatomy between blood vessel and capillary?
Capillary only has endothelium. no smooth muscles.
3 layers of blood vessel
Tunica intima
Tunica media
Tunica externa.adventitia
Difference between smooth muscle and skeletal muscle contraction
skeletal muscles can shorten a little. and smooth muscles can shorten a lot. M line is empty.
How does ACh work in different receptors?
varies per receptor
Vascular beds = relaxation
Small Intestines = contraction
How are actin sites found in smooth muscles?
It is always exposed
Does myosin do anything in smooth muscles?
Nothing, it’s just there
Explain smooth muscle contraction process
highly dependent on Ca++ influx
Ca++ influx (leak, V-G, SR) > binds to calmodulin > Ca++ calmodulin complex > CAM kinase phosphorylate MLC > activates MLCK > contracts > Ca++ efflux > Myosin phosphatase removes phos > relaxation
What other ways can you relax the smooth muscle?
Ca++ put back in SR
PMCA- plasma membrane calcium atp-ase
Na+/Ca++ exchanger (3:1)
How else can you reduce MLCK activity?
- Nitrates > cGMP > PK-G > phosphorylate MLCK > reduce activity
- PK-G > phosphorylate Ca++ ch > inactive
How does ACh or bradykinin cause vascular relaxation?
ACh/bradykinin binds to a receptor > Ca++ release from ER > binds to calmodulin > eNOs > binds to Arginine > NO > binds to cGMP > PK-G > phosphorylate Ca entry channels > closes gate > vascular relaxation
What does PDE-5 (sildenafil) do to vascular smooth muscle?
increase cGMP > increase PK-G > vascular relaxation
What was PDE-5 previously used for?
treatment for Pulm HTN resulted with new treatment plan
signal transduction cascade with A1, serotonin
A1 agonist > PIP-C > IP3, DAG (increase activity PK-C) > Ca++ from SR > binds calmodulin > activate
Special fact about serotonin
constrict brain blood vessel
Brain blood vessels only respond to one thing and not catecholamines
serotonin
T/F: Calcium leakage can cause smooth muscle contraction without AP
True
some smooth muscles can generate rhythmic motions in order to…
to produce some type of contraction
Heart contraction process
Na+ influx > AP > (20%) Ca influx L-ype (T-type faster) > Ca induced Ca release from SR (80%) > contraction > 80% via SERCA > 20% via Na+/Ca++ exchanger 3:1 and Ca++ atpase
What is calsequestrin?
A protein that helps the SERCA pack Ca++ into a container and remove it from the solution.
Found in any muscle with an SR.
What is phospholamban?
Inhibitor for the SERCA to allow ca+ to stay longer in the heart for a longer contraction.
B1 receptor process
B1 agonist > activates Adenylyl cyclase > activates cAMP > PK-A > contraction
ACh receptor process
ACh binds m-ACH-R > inhibit adenylyl cyclase > reduce cAMP > relaxation
