Chapter 10.3 - Smooth Muscles

Size of Smooth Muscles

smaller than skeletal m.

Shape of Smooth Muscles

spindle shape

Smooth M. Arrangement

2 layers

Inner Layer of Smooth M.

circular layer

Outer Layer of Smooth M.

longitudinal layer

Neural Wiring of Smooth M.

diffuse junctions where autonomic nervous system have varicosities that release neurotransmitters

Varicosities

bumps in nerves to smooth m. that allow for diffusion of Ach out instead of axon ends

Missing Organelles & Proteins from Smooth M.

no T-tubules, no troponin, small SR

Smooth M. connection between filaments and cell membrane

dense bodies

Smooth M. Filaments

contractile filaments

Synchronous Contraction due to...

gap junctions (activity spreads quickly)

Smooth M. Contraction gets calcium from...

outside the cell

Smooth M. calcium activates...

calmodulin (lock for calcium and myosin)

What pulls actin in smooth m. contraction?

phosphorylates (activated) myosin

Smooth M. Contraction Energy Usage

less ATP, tends to be slower but lasts longer

Norepi. smooth m. reaction in skin vessels...

excites

Norepi. smooth m. reaction in airways...

inhibits

Examples of hormones that influence smooth muscle activity...

epinephrine

Examples of local factors that influence smooth muscle activity...

pH, oxygen, carbon dioxide

Types of Smooth M.

single-unit & multiunit

Single-Unit Smooth M. Contractions

synchronous due to gap junction presence

Single-Unit Smooth M. Example

GI tract

Which type of smooth m. is more common?

single-unit smooth muscle

Multiunit Smooth M. Contraction

units can be recruited for more gradations

Multiunit Smooth M. Example

iris of eye