Josive
Badges: 10
Rep:
?
#1
Report Thread starter 1 year ago
#1
How does norepinephrine as a hormone get from the bloodstream to alpha and beta receptors in the smooth muscle
0
reply
macpatgh-Sheldon
Badges: 20
Rep:
?
#2
Report 1 year ago
#2
Norepinephrine [NE], although it can be classified under the broad umbrella of hormones, has a greater role to play as a neurotransmitter - so, as far as muscle is concerned, it is released from the adrenergic [sympathetic] nerve supply to the smooth muscle in the arterioles. When an impulse travels down the postganglionic neurone [this would start off after a synapse in the paravertebtral sympathetic chain either side of the spinal column, where the neurotransmitter is acetylcholine] and reaches the end of this [second] neurone, at this synapse, which lies on the arteriolar smooth muscle, NE is released and acts on the alpha adrenergic receptors to cause contraction of this [circular] smooth muscle, so that the arterioles constrict.

Action of NE on beta-2 receptors on the smooth muscle on muscular arterioles [i.e. arterioles that supply skeletal [striated] muscle], causes this smooth muscle to relax, causing dilatation, in order to increase blood flow [e.g. if a lion jumps in through your window, and you need to quickly make a move lol - it has been known to happen where I was brought up = Kenya!]

Having said that, depending what level you are studying at [not necessary to know at A level], beta-1 receptors are found mainly in the heart [mediate increased heart rate and force of contraction] and other important beta-2 receptors in the bronchiolar smooth muscle in the lungs [stimulation leads to bronchodilatation]

Hope this helps!
M.
2
reply
Josive
Badges: 10
Rep:
?
#3
Report Thread starter 1 year ago
#3
(Original post by macpatgh-Sheldon)
Norepinephrine [NE], although it can be classified under the broad umbrella of hormones, has a greater role to play as a neurotransmitter - so, as far as muscle is concerned, it is released from the adrenergic [sympathetic] nerve supply to the smooth muscle in the arterioles. When an impulse travels down the postganglionic neurone [this would start off after a synapse in the paravertebtral sympathetic chain either side of the spinal column, where the neurotransmitter is acetylcholine] and reaches the end of this [second] neurone, at this synapse, which lies on the arteriolar smooth muscle, NE is released and acts on the alpha adrenergic receptors to cause contraction of this [circular] smooth muscle, so that the arterioles constrict.

Action of NE on beta-2 receptors on the smooth muscle on muscular arterioles [i.e. arterioles that supply skeletal [striated] muscle], causes this smooth muscle to relax, causing dilatation, in order to increase blood flow [e.g. if a lion jumps in through your window, and you need to quickly make a move lol - it has been known to happen where I was brought up = Kenya!]

Having said that, depending what level you are studying at [not necessary to know at A level], beta-1 receptors are found mainly in the heart [mediate increased heart rate and force of contraction] and other important beta-2 receptors in the bronchiolar smooth muscle in the lungs [stimulation leads to bronchodilatation]

Hope this helps!
M.
Thanks so much! I understand it's role as a neurotransmitter what I was wondering is how norepinephrine from the adrenal glands that goes straight into the blood stream gets to these receptors When it doesn't have a synapse to do so
0
reply
HarisMalik98
Badges: 12
Rep:
?
#4
Report 1 year ago
#4
Not really my area of expertise, but the adrenal glands and the areas that norepinephrine acts on will have rich blood supplies (considering it acts on cardiac and smooth muscle). Therefore, the adrenal gland can release it directly into the bloodstream and it can directly act upon the alpha/beta receptors?
Last edited by HarisMalik98; 1 year ago
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How are you feeling about starting university this autumn?

Really excited (55)
22.36%
Excited but a bit nervous (112)
45.53%
Not bothered either way (33)
13.41%
I'm really nervous (46)
18.7%

Watched Threads

View All