Final Review Deck - Lecture III - Smooth Muscle

Question 1

What is the main difference between skeletal and cardiac muscle?

Answer 1

cardiac muscle can get calcium throguh calcium channels not just the SR like skeletal muscle

Question 2

Does smooth muscle have troponin and what kind of force does it generate?

Answer 2

no troponin and has low levels of force continuously

Question 3

What are smooth muscle cells like?

Answer 3

mononuclear cells and they are spindle shaped cells and can contract into little balls from a long spindle shape
-very skinny and elongated

Question 4

Over what range of lengths can smooth muscle contract?

Answer 4

over a very large range of lengths and there are actin thin filaments and myosin thick filaments and tropomyosin

Question 5

Instead of z lines what does smooth muscle have?

Answer 5

dense bodies which anchor the thin actin filaments

Question 6

What are the dense bodies linked to and what do they link together?

Answer 6

-linked to the plasma membrane and link together sarcoemres

Question 7

How are myosin filaments arranged in thick filaments?

Answer 7

there is no longitudinal bundle like in skeletal muscle and in the middle of the thick filament there is no crossbridges

Question 8

In smooth muscle compared to cardiac and skeletal muscle what does the arrangment of myosin in a 45 degree angle with no gaps do?

Answer 8

they can slide over a lot of distance and tehre is not limit in contraction lenght and can become l little ball

Question 9

What is the duration and strength of contraction for smooth muscle?

Answer 9

the duration is always prolonged and weaker contraction more persistent

Question 10

Are there t tubules and troponin in smooth muscel?

Answer 10

no

Question 11

Where does calcium come into smooth muscle?

Answer 11

from the SR and calcium channels like cardiac muscle

Question 12

In the single unit smooth muscle what are the cells joined by?

Answer 12

gap junctions so they behave as one and the aps propagate and calcium propagates and the innervation is through the autonomic nerve

Question 13

Is there a nerve terminal for smooth muscles that are innervated by an autonomic nerve?

Answer 13

no there are just varicosities which release transmitter along the length of the axon and the transmitter release is greater because there is no small synaptic cleft

Question 14

Why is the buildup of force so slow in smooth muscle?

Answer 14

because activation of force is through the diffusion of small molecules from varicosities

Question 15

Smooth muscle in what parts of the body tends to be single unit?

Answer 15

blood vessels, intestines, uterus

Question 16

What helps smooth muscle in uterus go from multi unit to single unit?

Answer 16

estrogen

Question 17

How does multiunit smooth muscle behave?

Answer 17

not connected by gap junctions behave independently

Question 18

What are some places in the body that have multi unit smooth muscle?

Answer 18

iris muscle and they control the pupil of eye and ciliary muscle controls the focal length and the non pregnant uterus

Question 19

Can smooth muscle have no innervation?

Answer 19

yes smooth muscle can have no innervation and can be spontaneously active and have rhythymic APs

Question 20

Can smooth muscle receive autonomic innervation?

Answer 20

yes both sympathetic and parasymathetic or just sympathetic like arterioles

Question 21

What is histamine and where does it come from and what are basophils?

Answer 21

histamine is the main mediator of inflammation
-comes from mast cells
-basophils are in the blood

Question 22

What can histamine and basophils do to vascular smooth muscle?

Answer 22

cause hyperpolarization to increase blood flow to an area

Question 23

What kind of channels do smooth muscle have?

Answer 23

stretch activated channels which can depolarize the cell in response to stretch and the stretching of the smooth muscle causes more calcium entry so flow stays the same via contraction

Question 24

There are receptor activated channels in smooth muscles and what do they bind to and cause?

Answer 24

bind to a transmitter or hormone and let calcium into the smooth muscle cell

Question 25

What does the sodium potassium pump in smooth muscle do?

Answer 25

it is electrogenic and causes the cell to have a expulsion of one positive ion out every round

Question 26

What do voltage gated sodium channels in smooth muscle do?

Answer 26

they allow for the influx of sodium into the cell causing an amplification of the depolarization seen in the muscle cell

Question 27

What do voltage sensitive calcium channels do in smooth muscles?

Answer 27

come in during calcium depletion from SR and depolairzation or stretch activated in arterioles

Question 28

What does the potassium channel do in smooth muscle?

Answer 28

hyperpolarizes the cell

Question 29

How is calcium released from the SR?

Answer 29

there is a transmitter or hormone which binds to a GPCR and this causes PLC to be actuvated and it cleaves PIP2 into DAG and IP3 and IP3 goes to the SR and binds to a receptor there and causes calcium to be released

Question 30

How is calcium removed in smooth muscle?

Answer 30

calcium atpase into the SR
-calcium pump in the membrane to pump into the ecf or a 3 sodium in one calcium out exchanger

Question 31

What is the conductance?

Answer 31

1/R
-the inverse of resistance

Question 32

How many IP3Rs are there in the membrane of a cell and how much calcium do they let in?

Answer 32

only 1 or 2 per cell
let in alot of calcium has a consductance of 200 picosiemens which is 1S = 1A/V

Question 33

There are thousands of membrane Orai1 proteins per cell what does it do and how does STIM1 interact with it?

Answer 33

lets calcium into the cell when activated by the STIM 1 which is in the ER membrane and they have calcium sensors which bind calcium in the ER and when no calcium is present they aggregate and their cytoplasmic side reaches out to Orai1 and causes that channel to open and let calcium in
-Orai1 is store operated calcium channel which only open when calcium is depleted in the smooth ER

Question 34

What is the subunit of myosin in smooth muscle?

Answer 34

it is a dimer with an alpha helical coil - and each myosin molecule contains three chains

Question 35

What are the three chains of a myosin molecule in smooth muscle?

Answer 35

-essential light chain
-regulatory light chain
-heavy chain

Question 36

What are the three domains of the myosin molecule in smooth muscle?

Answer 36

-head, neck, tail

Question 37

What does the head have of the myosin molecule?

Answer 37

atpase and binding actin ability

Question 38

What does the regulatory light chain control control>

Answer 38

cycling it must be phopshorylated to cause a contraction and dephosphorylated to stop it and the state of phosphorylation is regulated by calcium

Question 39

What happens when the regulatory light chain get phosphorylated?

Answer 39

the crossbridge cycle occurs the myosin head goes from unattached to attached

Question 40

Is there troponin and tropomyosin in smooth muscle?

Answer 40

there is no troponin but there is tropomyosin but it dos not block the actin binding site

Question 41

How is the phosphorylation of the myosin light chain dependent on calcium?

Answer 41

the myosin light chain kinase is activated in a calcium clamodulin dependent manner
-when the chain is phosphorlated it is attached when it is unphopshorylated it is unattached by the myosin light chain phosphatase

Question 42

Can the unattached head bind to ATP?

Answer 42

yes but it results in slower cycling