Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SF3 - Test 1 > 2 - Smooth Muscle > Flashcards

2 - Smooth Muscle Flashcards

1
Q

Type of Smooth Muscle

A

Non-striated muscle found mostly in hollow organs and tubes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do contractions compare to skeletal muscles?

Arrangement

Purpose

Contraction Time

A

Arrangement - Contractile fibers not arranged in sarcomeres

Purpose - Alters dimension of the organ (tube, etc.)

Time - Contractions last much longer than in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Types of Smooth Muscle: Unitary/Visceral

Organization

Connections

A

Org: Large sheets

Connected: Gap Junctions, in syncytial fashion–stimulation leads to stimulation of adjacent cells resulting in wave of contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Types of Smooth Muscle: Multi-Unit

Organization/Connection

A

Cells not electrically connected–each cell must be individually stimulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Actin and Myosin in smooth muscle cells?

A

Filaments longer than in skeletal muscle

Arranged around periphery of cells

Less myosin than in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do actin thin filaments contain in smooth muscle cells?

A

Tropomyosin, but not troponin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is unique about the myosin in smooth muscle cells?

A

Myosin isoform different from skeletal muscle–slower ATPase activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Sarcoplasmic Reticulum in smooth muscles?

A

Present, but not T-tubules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Role of Ca2+ in Smooth Muscle:

Increase of intracellular Ca2+

How does it enter into the cell?

How is it released?

Why is it important to have these methods?

A

Initiates contraction

Enters via voltage-gatedandligand-gated Ca2+ channels

IP3 Channel - activated by IP3 generated from GPCRs; also released from Sarcoplasmic Reticulum (SR)

- - -

Sustained contraction requires extracellular Ca2+ –calcium in = contract, calcium out = relax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Smooth Muscle Actin-Myosin Interactions and Differences w/Skeletal Muscle

(Steps to Drive Contraction)

A
  1. Calcium binds to Calmodulin
  2. Ca-Calmodulin Complex activates myosin light chain kinase (MLCK)

3. MLCK phosphorylates regulatory Light Chains of Myosin (MLC)

  1. Increases Myosin ATPase activity and binding to actin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Ryanodine Receptor (RYR3) in Smooth Muscle

A

Present in Smooth Muscle SR

Increase in intracellular Ca2+ activates RYR3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Mechanism of Cross Bridge cycling for smooth muscle?

A

Same as skeletal muscle

  1. ATPase on Globilar head of myosin hydrolyzes ATP to ADP and Pi
  2. Myosin head binds to actin
  3. Release of ADP and Pi causes myosin head ratchet movement
  4. ATP binds myosin, actin released
  5. Will continue as long as MLC phosphorylated and [Ca2+] is high enough
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does kinetics cycling compare to skeletal muscle?

How does max force compare?

A

Much slower

Maximum forces generated in greater in smooth muscle than in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is Smooth Muscle regulated compred to skeletal muscle?

A

Smooth - Thick Filament

Skeletal - Thin Filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Relaxation of Smooth Muscle?

A

Removal of Ca2+

  1. SR Ca2+ ATPASE (SERCA) Pumps Ca2+ back into SR (same as skeletal)
  2. Ca2+ pump in plasma membrane
  3. Na-Ca Exchanger in Plasma Membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the removal of calcium lead to in smooth muscle?

A

Dephosphorylation of MLC by Myosin Light Chain Phosphatase (MLCP)

Myosin can no longer bind to actin–no cross bridge cycling

= Relaxation of muscle

17
Q

What determines level of tension in smooth muscle?

A

Ca2+ Levels

18
Q

Phasic vs Tonic Contractions

A

Phasic - Contracts rhythmically or intermittently; quick influx of Ca2+, cross-bridge phosphorylation, force peak, then return to baseline

Tonic - Contracts continuously; Same intracellular Ca2+, cross-bridge phosphorylation, but does not return to baseline

19
Q

Tonic Contractions: Force Generation

Latch State?

A

Force slowly increases and sustained at high level (sphincters example)

- - -

  1. Cross bridge cycling rates much slower
  2. Force maintained w/low MLC phosphorylation
  3. Myosin stays attached to actin and force continues to be generated
  4. Ca2+ stays above baseline (calcium fluxes)
  5. Tension quires low [ATP]
20
Q

Smooth Muscle Contraction Regulation: Unitary Muscle

A

Membrane potentials are unstable

Continuous, irregular contractions independent of nerve supply–leads to different type of potentials

21
Q

Smooth Muscle Potential Types:

Slow Wave

Pacemaker

Pharmacomechanical

A

Slow Wave: Rhythmic changes, when cross threshold get contractions

Pacemaker: Regular depolarizations, regular rhythms of contractions

Pharmacomechanical: Change in tension without change in potential

22
Q

(Regulation) Control Systems in Smooth Muscle:

Contraction

A

Increase Activity of Ca2+ Channels

Increase release of Ca2+ from SR

Inhibit MLC Phosphatase

23
Q

(Regulation) Control Systems in Smooth Muscle:

Relaxation

A

Block Ca2+ Channels

Open K+ channels–cell hyperpolarizes, reduces Ca2+ influx through Voltage-Gated Ca2+ channels

24
Q

(Regulation) Control Systems in Smooth Muscle:

cGMP Levels

A

Increase = Relaxation

Activation of Autonomic NS, hormones, drugs

Nitric Oxide (NO) produced by nerves and vascular endothelial cells–activates kinases; these activate MLCP and reduce intracellular Ca2+ ​

25
Q

(Regulation) Control Systems of Smooth Muscle:

cAMP Levels

A

Increase = Relaxation

Stimulation of B-adrenergic or adenosine receptors (pharma agonists activate these)

cAMP-dependent kinases phosphorylates MLCK

Reduces intracellular Ca2+

26
Q

Autonomic Nervous System effect on smooth muscle?

Effect Depends on Muscle!

Intestinal Smooth Muscle

A

Para - Membrane potential = less negative, leads to more contractions

Symp - Membrane potential = more negative, leads to less contractions

27
Q

Autonomic Nervous System effect on smooth muscle?

Effect Depends on Muscle!

Bronchial (Lung) Smooth Muscle

A

Para - Increase in contractions

Symp - Acts on B-Adrenergic Receptors to cause relaxation

28
Q

Autonomic Nervous System effect on smooth muscle?

Effect Depends on Muscle!

Blood Vessel

A

Symp - Acts on a-Adrenergic receptors to cause constriction

29
Q

Biophysical Properties of Smooth Muscle?

Length-Tension

A

Maximal tension generated over wide range of lengths

(big goldilocks zone vs skeletal muscle)

Cause: Smooth Muscle only partially activated, cross-bridge kinetics slower, more shortening/lengthening than skeletal muscle

30
Q

Biophysical Properties of Smooth Muscle?

Force-Velocity Relationship

A

Contraction velocities slowerin smooth muscles, but also depends onload

Smooth muscle velocity affected by phosphorylation of MLC

Depends on Calcium–more = phosphorylation of MLC

31
Q
A

SF3 - Test 1 (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions