Smooth Muscle

Question 1

Respiratory conditions

Answer 1

Asthma;

Pulmonary hypertension

Question 2

Circulatory

Answer 2

Hypertension;

Sepsis (Low BP due to infection

Question 3

GI tract problem

Answer 3

IBS

Question 4

Male reproductory tract

Answer 4

Impotence;

Urine retention

Question 5

Female reproduction tract

Answer 5

Parturition

Question 6

Smooth muscles are modulated by?

Answer 6

Autonomic nerves and circulating hormones

Question 7

Sphincter smooth muscle

Answer 7

Found in the esophagus, anus and urethra;
High level of intrinsic contractile activity (myogenic);
Can be reduced by the release of inhibitory neurotransmitters from autonomic nerves which allows the movement of solid matter or fluid;

Question 8

Lymphatic vessel comprise of?

Answer 8

Smooth muscle;

Intrinsic ability to contract in phases so able to move fluid;

Question 9

Where all are smooth muscle found?

Answer 9

Sphincters;
Blood vessels;
Airways;
Stomach;
Intestines;
Esophagus;
Urinary bladder;

Question 10

Smooth muscle structure

Answer 10

No striations; not banded;
Has actin and myosin;
Net-like structure to alter shape;
Supported by and contains CT;
Unlike skeletal muscle doesn’t act on structures like bones and tendons;
Within an organ, lost of different smooth muscles that perform different functions;

Question 11

How is smooth muscle structurally organised?

Answer 11

Single sheets-
Arterioles, airways;
Circular;
Maintains diameter and pressure;
Varys diameter, controls flow and pressure;

Multiple sheets -
Two sheets perpendicular to each other;
Circular and longitudinal layers;
Vary diameter and length - peristalsis

Question 12

2 types of smooth muscle

Answer 12

Single unit -
Arterioles, lymph vessels, GI tract, uterus;
Myogenic;
Regulated by circulating hormones, autonomic nerves and plexus;
Initiated by stretching;
Electrically coupled to one another by gap junctions;
Action potential propagate between cells;
Fibres act in unison - synchronised contraction and relaxation;
Non-selective channels allow intracellular communication;
Behaves as a functional syncitium

Multi-unit -
Bronchi, large arteries
Neurogenic - normally quiescent;
Excited by ANS;
Muscle fibres are structurally independent - not electrically coupled with gap junctions;
Each unit stimulated separately;
Similar to SKM - fine control, graded contraction;
No NMJ but diffuse distribution of NT receptors;

Question 13

Varicosity

Answer 13

The point of the nerve that makes contact with SM

Question 14

Why smooth muscle and not skeletal muscle

Answer 14

Smooth muscle is more versatile;

Can stretch more and has more length;

Question 15

Which inorganic ion is responsible for contraction

Answer 15

Calcium ion

Question 16

Calcium enters into smooth muscle by?

Answer 16

Calcium voltage gated channels

Intracellular release:
Alpha-adrenoreceptors - allows non adrenaline
Muscrinic receptors - acetylcholine

Question 17

Ca2+ source differs to that of SKM

Answer 17

No T tubule;

Small enough for Ca to diffuse quickly about;

Question 18

Contraction by sliding filament theory

Answer 18

Influx of Ca through the membrane - increased cellular calcium;
Calcium binds to calmodulin which activated myosin light chain kinase;
MCLK phosphorylates myosin light chain;
Frees myosin;