Muscles 9

Question 1

Smooth muscle must operate

Answer 1

Over a range of lengths

Question 2

Smooth muscle layers run

Answer 2

In many directions

Question 3

Smooth muscles contract and relax

Answer 3

slowly compared to skeletal muscle

Question 4

Smooth muscle use less energy than skeletal to:

Answer 4

Generate and maintain force

Question 5

Smooth muscle can sustain

Answer 5

Contraction without fatigue

Question 6

Smooth muscle contraction is initiated

Answer 6

Electrically or chemically

Question 7

Smooth muscle is controlled by

Answer 7

The autonomic nervous system

Question 8

Smooth muscle gets Ca2+ from

Answer 8

The extracellular space and/ or the SR

Question 9

Smooth muscle Ca2+ initiates cascade which

Answer 9

Which turns on myosin ATPase

Question 10

Smooth muscle characteristics

Answer 10

Spindle shaped
Uninucleated
Troponin and t-tubules absent
Non contractile filaments
Dense bodies (similar to z-lines of skeletal)
Thin filaments anchored to cell membrane or dense bodies

Question 11

6 locations of Smooth Muscle in humans

Answer 11

1. vascular -blood vessel walls
2. Gastrointestinal -walls of digestive tract and associated organs (gallbladder)
3. Urinary -wall of bladder and ureters
4. respiratory -airway passages
5. Reproductive -uterus (female) and more
6. Ocular -iris and ciliary body

Question 12

Smooth muscle 4 contraction patterns:

Answer 12

1. Physic smooth muscle is relaxed -esophagus
2. Physic smooth muscle cycles between contraction and relaxation -intestine
3. Tonic smooth muscle usually contracted -sphincter that relaxes to allow passage
4. Tonic smooth muscle whose contraction varies -vascular smooth muscle

Question 13

Smooth muscle Communication with Neighbouring cells: 2 parts

Answer 13

Unitary (single unit) smooth muscle
Multi unit smooth muscle

Question 14

Unitary (single unit) smooth muscle:

Answer 14

Contains gap junctions similar to cardiac muscle cell
-allows coordinated contraction of many cels causing muscle to contract as a single unit
-makes up walls of most visceral organs
AKA Visceral Smooth Muscle

Question 15

Multi unit Smooth Muscle

Answer 15

Not electrically coupled
-iris and cilliary body of eye
-in male reproductive tract and uterus except just prior to delivery

Question 16

Smooth muscle may contract in response to

Answer 16

Synaptic transmission or electrical coupling

Question 17

Smooth muscle is usually innervated by

Answer 17

The autonomic nervous system
-sympathetic and parasympathetic
-by multiple neurons capable of releasing different neurotransmitters

Question 18

Alpha adrenergic vs Beta adrenergic in smooth muscle

Answer 18

Alpha: Gi vessel constriction
Beta: airway dilation

Question 19

Other factors that can alter smooth muscle tension: (5)

Answer 19

Circulating hormones
Stretch and local factors (including paracrine signals)
Acidity
O2 and CO2 concentration
Osmolarity

Question 20

Action potentials of smooth muscle can be initiated by what stimulations? (3)

Answer 20

Neural, hormonal, or mechanical stimulation

Question 21

Smooth muscle APs are similar to

Answer 21

Skeletal in the way the upstroke is slower because Ca2+ channels propagate the AP instead of Na+
-repolarizatio also slower because Ca2+ channels inactive slowly -delayed activation of voltage gated K+ and some Ca2+ activated K+ channels

Question 22

As in smooth muscle usually don’t happen in which unit:

Answer 22

Multi unit smooth muscle

Question 23

Smooth muscle cells produce a wide range of

Answer 23

Membrane potentials
-some oscillations can lead to tonic contractions in absence of AP

Question 24

Single Unit smooth muscle APs:

Answer 24

Autonomic AP initiation: spikes or plateaus
Spontaneous AP: slow wave, pacemaker

Question 25

Multi unit smooth muscle APs:

Answer 25

Graded potentials
=contraction due t electrical signaling
Electromechanical Coupling

Question 26

Extracellular entry and Intracellular release of Ca2+ activate contraction and cytosolic is increased by three different mechanisms:

Answer 26

1. Ca2+ entry through voltage gated or ligand gated ion channels
2. Ca2+ release from SR
   =Ca2+ induced release from ryanodine receptor
   -IP3 CA2+ release from IP3R
3. Ca2+ entry through voltage independent channels -store Ca2+ and stretch activated channels