Smooth Muscle Physiology

Question 1

Dense body are analogous to..

Answer 1

Z - Line

Question 2

Dense Area are

Answer 2

Cell to Cell connection sites

Question 3

Match Layer w/Function and Example

1) Circular
2) Circular & Longitudinal
3) Rectangular

Answer 3

1. Maintain Pressure - Blood Vessels
2. Propel Content - Intestine
3. Regulate Internal Flow - Bladder, Rectum

Question 4

Name 3 feature of smooth muscle not found in C, or SK.

Answer 4

Dense body - Z- Line
Dense Area - cell to cell connection
Intermediate Filaments

Question 5

Name 2 feature of C, or SK muscle not found in smooth muscle

Answer 5

Troponin

T-tubules

Question 6

Classification: Single Unit vs Multi Unit Smooth Muscle

Name the one organ that transitions ___ why?

Answer 6

Single - gaps present (syncytium)

Multi- no GJ, more varicosities,

Uterus *needs to function a contractile unit

Question 7

Smooth Muscle Contraction Types, and associated tissues

Answer 7

1) Tonic - Continuous partial contraction - blood vessel, airway of lungs - No AP
2) Phasic - Rhythmic/intermittent contraction - Gastrointestinal tract, urinary = AP needed

Question 8

Smooth muscle contraction req. Ca++ from ______ & _______. What are the channels are involved in bringing Ca++ into the cell?

Answer 8

Extracellular Space & SR

1. Calcium induced Ca Release - DHPR / RyR
   (AP needed)
2. G- Protein Inositol 3 - Phosphate Receptor
   (No AP needed)

other channels include stretch activated, ligand gated Ca++ channels

Question 9

Calmodulin is a ________ protein that binds with _______ then ______ and activates it.
______ binds ________ hydrolyzing it, and _______/_______ the myosin head.

Answer 9

common cytosolic
Ca++
Myosin Light Chain Kinase (MLCK) (twice)
ATP, 
Phosphorylating/Activating

Question 10

The Myosin head has a binding site for _____. , the ATP is hydrolyzed bringing the myosin head to the _______ position. Once the myosin is _______, by ______ the myosin, binding and _______ occur. ______ is needed for detachment.

Answer 10

ATP
Cocked 
Activated
MLCK
cross bridge cycling
ATP

Question 11

T/F

Cross bridge cycling in smooth muscle is slower than in cardiac and skeletal?

Forces generated b/w these tissues not about the same

Answer 11

T

F

Question 12

What enzyme is activated in smooth muscles when there is decreasing levels of Ca+

Answer 12

Myosin Light Chain Phosphatase - de-phosphorylate myosin.

Question 13

How is Relaxation induced. What channels are involved at the

SR Level
SL Level

Answer 13

• Reduce intracellular Ca++

Serca (Ca –> SR)
Ca++ Pump, Na+ / Ca++ Exchanger

Question 14

Nitric Oxide, aCH, Epinephrine - Relaxation.. EXPLAIN

Answer 14

PNS releases NO - activates PKA -
PNS releases aCH –> Activates endothelial cell –> activates PKG

SNS releases EP - activates PKG

both phosphorylate MLCK (inactivating it)
NOTE* Calmodulin (w/bound Ca++) activates MLCK by binding, not phosphorylation.

Question 15

T/F:

While some smooth muscle need an action potential to contract, other types are self excitable

Answer 15

T

Question 16

What are the two types of Self Excitable Cells

NOTE* - This is Electrical Activity

*mV never passes 0 mV

Answer 16

Pacemaker Potential - basically same as Pacemaker AP. shorter duration (thin hill), Na+ brings to threshold.

Slow Wave Potential (mm–> stimulus–> MM (reach threshold) CA++ channels open –> burst of AP on slow waves - III (summation occurs)

Question 17

Na+ are responsible for..

Ca++ are responsible for..

Answer 17

Bringing to threshold

creating action potential

Think of graph for Pacemaker P, and Slow Wave P.

Question 18

Name 4*mechanisms of producing contraction in SM

Answer 18

Electrical Activity (summation occurs) (& stretch)
Hormones
Autonomic Nerves
Drugs - No changes in mV of membrane p.

Question 19

In smooth muscle, _______ doesn’t usually cause contraction, but can modify _____, and _____

Answer 19

Nerve innervation
Rate of activity
Strength of contraction

Question 20

There is no ________ in smooth mm, instead nerves run across SM cells with bundles on neurotransmitters called _______, ____, ____ receptors are all over SM cells and respond accordingly to autonomic stimulation changing ______, & _______

Answer 20

NMJ
Varicosities 
Adrenergic (B1) & Cholinergic (muscarinic)
Rate of activity 
Strength of contraction