4 - Smooth Muscle

Question 1

All smooth muscles lack the […] banding pattern found in cardiac and skeletal fibers.

Answer 1

Striated

Question 2

The nerves to all smooth muscle are derived from the […].

Answer 2

Autonomic nervous system (ANS)

Question 3

General description of a smooth muscle cell.

Answer 3

Spindle-shaped, sinle nucleus, smaller/shorter than skeletal muscle

Question 4

True/False: Unlike skeletal muscle smooth muscle can divide.

Answer 4

True

Question 5

Smooth muscle does have tropomyosin but lacks […].

Answer 5

Troponin

Question 6

Why is smooth muscle not striated?

Answer 6

Thick and thin filaments are not organized into myofibrils therefore there are no aligned sarcomeres.

Question 7

Anchor the thin (actin) filaments to the cell’s plasma membrane or to structures in the cytoplasm.

Answer 7

Dense bodies (i.e. analogous to Z discs)

Question 8

Smooth muscle type, an entire group of muscle fibers responds to stimulation as a single unit (i.e. electrical and contractile activity is synchronous in all cells)

Answer 8

Single-unit (i.e. unitary or visceral); occurs because all cells are connected to adjacent cells via gap junctions

Question 9

A common method single-unit smooth muscle contraction can be induced.

Answer 9

Stretching (i.e. smooth muscles of the stomach and intestines)

Question 10

Smooth muscle type, contain few or no gap junctions, and each cell thus responds independently

Answer 10

Multi-unit

Question 11

Method of single-unit (i.e. smooth muscle type) regulation.

Answer 11

Regulated via frequency pacemaker fires

Question 12

Method of multi-unit (i.e. smooth muscle) contraction.

Answer 12

Number of fibers activated and frequency of activation

Question 13

The following are examples of what type of smooth muscle? Eyes, large airways, larger arteries, and attached to the hairs in the skin.

Answer 13

Multi-unit

Question 14

Forms the head of a myosin molecule.

Answer 14

Two light chains plus one heavy chain

Question 15

Smooth muscle cells lack […]. therefore tropomyosin never blocks myosin’s access to actin.

Answer 15

Troponin

Question 16

How is cross bridge binding regulated in smooth muscle?

Answer 16

Regulation of calicum activation via myosin light chain kinase

Question 17

Methods by which calcium ion concentration in the cell’s cytoplasm is increased.

Answer 17

Opening membrane channels (i.e. influx of extracellular calcium) or stimulation of the cell;s sarcoplasmic reticulum (i.e. released stored calcium)

Question 18

Protein that calcium binds to within the cell to activate the myosin light chain kinase.

Answer 18

Calmodulin

Question 19

Function of myosin light chain kinase.

Answer 19

Phosphorylates one of the light chains of each myosin head.

Question 20

In order to relax smooth muscle myosin must be […] to remove it from actin.

Answer 20

Dephosphorylated

Question 21

How is calcium removed from smooth muscle back to the ECF or sarcoplasmic reticulum?

Answer 21

Via ATP-requiring pump

Question 22

Enzyme, always active in smooth muscle, dephosphorylates myosin light chain.

Answer 22

Myosin light chain phosphatase (i.e. when outpaces MLCK muscle relaxes)

Question 23

The rate of ATP splitting and cross bridge cycling during contraction in smooth muscle are [>/=] skeletal muscle.

Answer 23

< (i.e. less than or slower)

Question 24

The velocity of smooth muscle shortening is […] than skeletal muscle.

Answer 24

Slower

Question 25

True/False: Smooth muscle and skeletal muscle both undergo fatigue during long periods of activity.

Answer 25

False; smooth muscle does not

Question 26

State of a smooth muscle, can last for hours, occurs when a full contraction occurs and is maintained near full level despite declines in levels of energy consumption.

Answer 26

Latch state

Question 27

Inputs to smooth muscle that increase the cell's cytosolic calcium levels and therefore regulate contractions.

Answer 27

Transmitters via ANS, hormones, local factors (i.e. acidity, osmolarity, etc.), stretch of the fiber, spontaneous electrical activity in the fiber's plasma membrane.

Question 28

True/False: A membrane potential change is required for a smooth muscle cell to contract.

Answer 28

False

Question 29

Due to some smooth muscle cells producing [...] they are able to generate an AP in the absence of neural, hormonal, or local inputs.

Answer 29

Pacemaker potentials (i.e. resting membrane potential depolarizes slowly to threshold)

Question 30

[...] are produced in smooth muscles with pacemakers that have a membrane potentail that drifts up and down (i.e. possibly due to regular variation in ion flux across the membrane)

Answer 30

Slow waves

Question 31

Slow waves are typically found in [...] smooth muscle therefore an AP causes the entire group of cells to contract.

Answer 31

Single-unit

Question 32

Smooth muscles [...] have a motor end-plate region.

Answer 32

Do not

Question 33

Swollen regions found on the branches of postganglionic neurons, filled with transmitter contain vesicles.

Answer 33

Varicosity

Question 34

True/False: A given transmitter can increase tension in one smooth muscle while decreasing tension in another.

Answer 34

True

Question 35

Hormones that have receptors on smooth muscle.

Answer 35

Epinephrine, cholecytokini, angiotensin II, vasopressin