Smooth muscle

Question 1

Muscle contracts two ways. What are those ways?

Answer 1

Isotonically: same strength
-Force generated is sufficient to move load
Isometrically: same length
-Force generated is insufficient to move weight placed on muscle

Question 2

What is preload and afterload?

Answer 2

Preload is stretch

Aferload is how much you have to lift

Question 3

Length tension relationship?

Answer 3

As you increase muscle length you get more force generated. Actin myosin have better connection.

Question 4

How is skeletal muscle preload set?

Answer 4

Skeletal muscle is already set close to the optimal preload length.

Question 5

What is the force-velocity relationship.

Answer 5

Preload is set afterload is changed

• Velocity of shortening is measured at variety of afterloads
• Load increases, speed decreases
• Slower contraction gives more cross bridges more time to form

Question 6

Innervation of smooth muscle can happen in 2 ways: what are they?

Answer 6

Single unit: GI, bladder, uterus
-Cells linked together by gap junctions
-little innervation
Multi-unit: Iris, vas deferens
-each cell has its own innervation
-function as distinct muscle cels

Question 7

This is smaller than skeletal muscle and spindle shaped.

Answer 7

Smooth muscle

Question 8

3 different ways calcium gets into cell.

Answer 8

Gq mediated system: doesn’t change membrane polarity, goes to SR and dumps Calcium there.
Depolarization: spread through gap junctions
Ligand gated channels: hormones or neurotransmitters open channels and let calcium in

Question 9

All calcium for smooth muscle contraction comes from the __.

Answer 9

SR

Question 10

How is calcium release unique in smooth muscle?

Answer 10

Calcium induced calcium release.

Question 11

What is difference between tonic and phasic contraction?

Answer 11

Phasic contractions have single spike like skeletal muscle

Tonic contracitons single spike but maintain force because of “latch state” of smooth muscle myosin

Question 12

For myosin to let go it has to bind ______.

Answer 12

ATP

Question 13

Unphosphorylated myosin has ____ affinity for ATP.

Answer 13

low

Question 14

Some differences between smooth and striated muscle?

Answer 14

Non-striated, no sarcomere
Cycling of cross bridges is much slower in smooth muscle
Longer contractions
Can latch
Much lower metabolic demand
CICR
Can have gap-junction
Activated by circulating hormones

Question 15

Very hard to over stretch smooth muscle. Why is this important?

Answer 15

Generates same maximal force. It will generate maximal force at any length.

Question 16

What is the force-velocity relationship?

Answer 16

Velocity of contraction increases with % of myosin phosphorylated. Increased load increases Ca2+ flux, increases MLCK activation.

Question 17

Calcium has very little affect on resting membrane potential. But has big affect on what?

Answer 17

Has big impact on action potentials.

Question 18

This increases threshold but is less excitable?

Answer 18

Hypercalcemia

stronger contractions

Question 19

This threshold is less negative.

Answer 19

Hypocalcemia

weaker contractions

Question 20

What are big chunky Y shaped cells?

Answer 20

Cardiac muscle

Question 21

There are a lot of gap junctions at _____________.

Answer 21

intercalated disk

Question 22

What cardiac refractory period. No conducted potential can generate an AP (AP will fire but nor go anywhere)

Answer 22

Effective Refractory Period

Question 23

What cardiac refractory period. AP can fire if a greater than normal stimulus is provided
Will have a shortened plateau

Answer 23

Relative Refractory Period (RRP)

Question 24

What cardiac refractory period. Cell is MORE excitable than normal. Has not yet reached full RMP.

Answer 24

Supranormal Period (SNP)

Question 25

True/False. Length tension relationship a lot more important in cardiac muscle than smooth.

Answer 25

True, if you stretch smooth muscle it will adapt and keep same output. Heart will be much stronger.

Question 26

Electrical conduction system to set heart rate. SA node is primary. No SR. Have an unstable RMP.

Answer 26

Cardiac Pacemakers

Question 27

Changing Increase flow through funny current. Na moves in and depolarize. Then IcaT opens and more depolarization.

Answer 27

This is how you change your heart rate.