Smooth muscle Flashcards
1
Q
Where is smooth muscle present?(and roles?)
A
- Vascular system-(e.g-capilliaries, arteries and veins)(Hypertension)
- Airways-(Trachea, bronchioles)(Asthma)
- GI tract-(Stomach,sphincters)(Gastric spasticity)
- Urinogenital tract-(bladder,uterus,vas deferens)(Infertility & incontinence)
- Eye-(Iris & cilary body)
2
Q
Why do you target smooth mucle for hypertension?
A
- Reduce vasoconstriction
- Current targets are receptors and target mech of contraction
3
Q
Why do you target smooth mucle for angina?
A
- Relaxation of coronary artery
- Current targets inc rec and signalling
- e.g K+ channels, NO
4
Q
Why do you target smooth mucle for asthma?
A
- Stimulation of B-adrenoreceptors-relax smooth muscle
- Inhibit msucarinic contraction
5
Q
Why do you target smooth mucle for Constipation?
A
- Stimulation of GI smooth muscle
6
Q
Why do you target smooth mucle for Diarrhoea?
A
- Inhibition of GI smooth muscle contraction
7
Q
What conditions involve treatment of Smooth muscle?
A
- Hypertension
- Angina
- Asthma
- Constipation
- Diarrhoea
8
Q
What are the functional roles of Smooth muscle?
A
- Regulate flow by varying tube diameter (e.g blood vessels during excercise)(Constriction & Dilation)
- Control flow by occluding tube(e.g Sphincters)
- Walls of storage organ (e.g bladder)(expand and expel)
- Movt of large bulk (e.g. Oesophagus,intestine) (swallowing-peristalsis)
9
Q
What is the structure of smooth muscle?
A
- Supported by and contains connective tissue. -SM does not act on structures e.g. bone(No tendons)
- Groups of small cells arranged in sheets
- Single sheet e.g. arterioles&airways (circularly orientated, controls blood flow)
- Multiple sheets e.g ileum
1.2 sheets perpendicular to each other
2. Longitudinal & Circular layers
3. Vary diameter & length: peristalsis
(See slides for diagram)
10
Q
What is peristalsis?
A
- Cyclical contraction & relaxation of sheets of smooth muscle that line tubular tissue
1.Lumen cavity constricts & dilates alternately
2.Synch and wavelike
3.Unidirectional movt of lumen contents - Nerve plexus btw 2 layers of muscle
1.E.g. myenteric plexus
2.Nerve network
3.Co-ordinates contr-relaxation cycle at local level
11
Q
How does smooth muscle contract?
A
- Actin & Myosin filament present
1.Actin filaments anchored to “dense bodies”
2.No troponin or troponin C
3.Sliding filament theory of contraction - Intracellular cytoskeleton harnesses pull
1.Contracts inward, bulges
2.Intracellular conncetions harness pull betw cels
12
Q
Explain sliding filament theory.
A
13
Q
What are varicosities?
A
- no specific junction between neurone and smooth muscle – more general release of neurotransmitters onto receptors over the surface of the muscle
14
Q
What is a single unit muscle?
A
- Electrically coupled to one another by gap junctions
1.Non-selective
2.e.g. calcium
3.fibres act in unison:synch contract & relaxation - 4.e.g. uniform,co-ord contraction of uterus during labour
15
Q
What are the contractile properties of a single-unit SM?
A
- Stretch-relaxation response
1.When SM is suddenly stretched it initially inc tension, then relaxes, but at a new longer length.
2.Allows hollow organs to accommodate variable amounts of contents without inc in pressure. Prev uncontrolled expulsion - 3.e.g.bladder, uterus
