Smooth muscle Flashcards
(30 cards)
What is muscular tissue derived from
Mesoderm
What is muscular tissue composed of
Cells (multinucleate syncytia) whose cytoplasm contains filaments made of proteins (actin, myosin)
DO smooth muscles have striations
no
What is smooth muscle supported by and contains?
Connective tissue
What is smooth muscle structurally organized as
sheets
Examples of single sheeted muscles
Arterioles and airways
What are single sheeted muscles orientated like
-what does it do
Circularly orientated
- tonically maintains vessel diameter and pressure
- vary diameter and so control flow and pressure
Examples of multiple sheeted muscles
Ileum
What are multiple sheeted muscles orientated like?
- What do they do
- Why do they have two layers
Two sheets perpendicular to each other
- longitudinal and circular layers
- vary diameter and length (peristalsis)
- Have two layers so they can move things along
Difference between smooth muscle and skm
SM often associated with other tissue types e.g. secretory epithelia
What are the types of smooth muscle
Single unit
Multi unit
What are single unit muscles like
All cells are ‘touching’ as they have gap junctions to allow action potentials to travel between cells so all the muscle works as a single unit
What do varicosities do
Interact with cells as they release neurotransmitters
What are multiunit muscles like
Cells don’t communicate with each other (allows for finer control)
-Each unit has to be stimulated separately
What do single unit smooth muscle behave as
Functional syncitium (have gap junctions)
Difference between Multiunit muscles and single unit
Single unit- myogenic
Multi unit- neurogenic
Why is smooth muscle needed instead of skeletal muscle sometimes
There is a stretch-relaxation response of single-unit smooth muscle.
-SMOOTH MUSCLE HAS CONNECTIVE TISSUE WHICH PREVENTS OVER-STRETCHING UNLIKE SKELETAL MUSCLE WHICH IS ELASTIC
What is unique to smooth muscle
Stretch-relaxation response (e.g. in bladder)
Which inorganic ion is responsible for the contraction of smooth muscle?
-How does it come into cell
Ca2+
-via voltage gated ca2+ channels
What does noradrenaline bind to and where is this found?
Alpha1 adrenoceptors on vascular smooth muscle contraction
What does acetylcholine bind to and where is this found?
Muscarinic receptors found on bladder smooth muscle contraction
What happens when noradrenaline binds to adrenoceptor
1) Increase in activity of G protein
2) Release of inositol triphosphate (IP3)
3) Interacts with receptor in sarcoplasmic reticulum which releases Ca2+
What happens when acetylcholine binds to muscarinic receptor
1) Increase in activity of G protein
2) Release of inositol triphosphate (IP3)
3) Interacts with receptor in sarcoplasmic reticulum which releases Ca2+
What causes the increase in activity of G protein
Binding of acetylcholine/noradrenaline to metabotropic receptors
