Muscles And Vessels - Lowrie Lecture

Question 1

Locations of smooth muscle

Answer 1

Visceral structures (except the heart)

Blood vessels and arrector pili muscles

tunica media of blood vessels

In the visceral structures - forms an inner circular and outer longitudinal layer

Question 2

Individual cells with smooth muscle characteristics include….?

Answer 2

Myoepithelial cells and myoid cells

Near the BM and have contractile function

Sometimes in mucus areas - squeeze juices into lumen

Question 3

Smooth muscle cells also secrete extracellular matrix (collagen, elastin). They also divide

Answer 3

….

Question 4

Smooth muscle cells are filled with what filaments?

Answer 4

Mostly thin filaments, some thick filaments, and desmin and vimentin (intermediate filaments)

Question 5

What do dense bodies do for smooth muscle cells?

Answer 5

They anchor the thin filaments in smooth muscle cells!

Located mostly at the the PM

Question 6

Gap Junctions electrically connect smooth muscle…. Sacroplasmic reticulum stores Ca2+ for SM…

Answer 6

….

Question 7

What do both SM and endothelial cells have?

Answer 7

Pinocytotic vesicles!

Question 8

SM is made of mostly thin filaments… actin!

Answer 8

…

Question 9

Gap junctions have what type of appearance?

Answer 9

Curvy appearance

Question 10

Basal lamina surrounds muscle cells

Answer 10

…

Question 11

Thin filaments (actin) for SM are anchored to dense bodies by…

Answer 11

Alpha-actinin

Question 12

Contraction of SM involves thick filaments (myosin) with pivoting heads.

Heads are oriented in opposite directions

Answer 12

….

Question 13

SM contraction…

Intracellular Ca2+ increases due to neural stimulation or hormonal signals

Ca2+ via calmodulin activates myosin light chain kinase (MLCK)

Myosin light chain kinase phosphorylates the light chains on myosin, activating them

Myosin light chain phosphatase removes the phosphate from LC to inactivate it

Answer 13

…

Question 14

In activate state of myosin light chains are coiled.. calcium activates them and uncoils them.

Answer 14

…

Question 15

Voltage gated Ca2+ channel in membrane opens when SM is stimulated - this leads to an increase in intracellular Ca2+, which opens ligand gated Ca2+ channel in the sacroplasmic reticulum.

hormones (oxytocin) can bind to receptors, and through G-proteins and Ip3, cause ca2+ channel to open in the sacroplasmic reticulum

Answer 15

…

Question 16

There are also mechanically gated ion channels that stimulate smooth muscle when stretched.

Answer 16

..

Question 17

After SM stimulation ceases, ATPase pumps remove Ca2+ from the sacroplasm

Answer 17

…

Question 18

Smooth muscle cells twist when contracted. Smooth muscle cells contract slowly, and use less energy (than skeletal and cardiac muscle).

Myosin heads can lock onto actin filaments, allowing muscle to maintain contracted state… this is called?

Answer 18

Latch-state!

Question 19

Contraction tension for smooth muscle is not….

Answer 19

Length dependent!

So smooth muscle can contract even when stretched (actually, stretching stimulates reflex contraction) - this is important for the uterus that is very stretch when pregant

Question 20

In multisubunit smooth muscle…

Answer 20

Each cell receives a synapse

This provides fine control (e.g. The iris)

Question 21

In unitary (visceral) smooth muscle…

Answer 21

Only a few receive synapses and adjacent cells are excited through gap junctions or neurotransmitter baths smooth muscle cells.

This provides larger functional unit (bladder, intestine)

Question 22

Two circulatory systems.. those are?

Answer 22

Vascular and lymphatic

Question 23

Blood vessels have three components…

Answer 23

Tunica intima (TI) - which is endothelial cells and loose CT

Tunica media (TM) - mostly smooth muscle

Tunica Adventitia (TA) - dense irregular CT

Question 24

Tunica media has smooth muscle and in between is elastic CT!

Answer 24

..

Question 25

Look at EM of blood vessels

Answer 25

…

Question 26

Vasodilation occurs via relaxation of smooth muscles

Answer 26

..

Question 27

Vasoconstriction occurs via contraction of smooth muscles

Answer 27

…

Question 28

SM is blood vessels is always somewhat contracted….

Nitric oxide causes vasodilation

Clotting factors (thromboxane) causes contraction of blood vessels

Answer 28

..

Question 29

Capillaries are everywhere, forming an _______ network

Answer 29

Anastomosing

Question 30

Capillaries are composed of

Answer 30

Endothelial and basement membrane

Question 31

Endothelial cells oriented longitudinally in capillaries - nucleus bulges - so it looks irregular

Answer 31

…

Question 32

Continuous capillaries

Answer 32

Least permeable, endothelial cells have tight junctions with no fenestrae

Question 33

Fenestrated capillaries

Answer 33

More permeable, endothelial cells have tight junctions but have fenestrae within the cells!!!

Find this in endocrine organs and intestinal tract

Question 34

Capillaries have pinocytotic vesicles

Answer 34

…

Question 35

Von Willebrand Factor is released from the endothelium and binds to platelet receptors causing adhesion of the platelets to exposed collagen fibers. As the platelets adhere to the collagen fibers on the damaged vessel wall, they become activated and release ADP and TXA2. The ADP and TXA2 attract additional platelets and lead to their aggregation

Answer 35

…

Question 36

Activated platelets have protrusions that enmesh them together

Answer 36

…

Question 37

What is the goal of the coagulation cascade?

Answer 37

Create fibrin glue to support plug until the endothelium and extracellular matrix remodel