L12 - ANS Flashcards
What are four characteristics of the ANS?
- autonomous
- unconscious control e.g. digestion, cardiovascular system, glands
- rest: parasympathetic
- activity: sympathetic
Is one branch of the ANS ever at 100% activity while the other branch is at 0% activity or are the branches balanced?
there is a dynamic balance between the autonomic branches
Where do sympathetic neurons originate?
from the spinal cord
Where do parasympathetic neurons originate?
from the brainstem and sacral roots
How close are sympathetic preganglionic neurons to the CNS?
closer to CNS, further from target
How close are parasympathetic preganglionic neurons to the CNS?
further from CNS, closer to target
What is an exception found in the sympathetic nervous system in regards to the location of preganglionic neurons?
travel directly to and are located within adrenal glands (modified PG neurons)
Where is acetylcholine used?
all autonomic preganglionic terminals
parasympathetic postganglionic terminals
Where is noradrenaline used? (= norepinephrine)
sympathetic postganglionic terminals
What is adrenaline (= epinephrine)?
hormone released into general circulation from adrenal glands
Which neurotransmitter is sympathetic and parasympathetic preganglionic?
acetylcholine
Which neurotransmitter is parasympathetic postganglionic?
acetylcholine
Which neurotransmitter is sympathetic postganglionic?
noradrenaline
What are the two types of cholinergic receptors?
nicotinic receptors and muscarinic receptors
Where are nicotinic receptors found?
sympathetic and parasympathetic postganglionic cells
Where are muscarinic receptors found?
parasympathetic target cells
What are four characteristics of adrenal glands?
sit on top of kidneys
neuroendocrine tissue
complex organ
adrenaline (80%) and noradrenaline (20%) is released from the medulla
What stimulates release of adrenaline into the body and what implications does this have?
release is stimulated by sympathetic preganglionic neurons
released into the bloodstream so there is general and non-specific distribution
reaches cells without specific autonomic innervation but cells need to have specific receptors
What are the two types of adrenergic (sympathetic) receptors?
alpha and beta adrenoceptors
Do alpha-1 and beta-1 adrenoceptors result in stimulation or inhibition?
stimulation
Do alpha-2 and beta-2 adrenoceptors result in stimulation or inhibition?
inhibition
What response does activation of alpha-1 adrenoceptor result in? What does it respond to? Is this the most common adrenoceptor?
stimulation of blood vessels and smooth muscle (contraction)
noradrenaline > adrenaline
yes
What response does activation of alpha-2 adrenoceptor result in? What does it respond to?
inhibition of gut and pancreas
noradrenaline > adrenaline
What response does activation of beta-1 adrenoceptor result in? What does it respond to?
stimulation of the heart (contraction)
noradrenaline and adrenaline
What response does activation of beta-2 adrenoceptor result in? What does it respond to?
inhibition of bronchial smooth muscle and blood vessels of heart, liver and skeletal muscles (relaxation)
adrenaline»_space; noradrenaline
What response does activation of beta-2 adrenoceptor result in? What does it respond to?
inhibition of bronchial smooth muscle and blood vessels of heart, liver and skeletal muscles (relaxation)
adrenaline»_space; noradrenaline
How is a wide range of responses able to occur in different parts of the body?
different adrenoceptors are commonly found in different areas of the body where they would be able to take effect if activated by their respective ligand
During exercise will there be activation of alpha-1 adrenergic receptors in blood vessels except for those found at skeletal muscles, heart and liver?
no, because activation of alpha-1 adrenergic receptors will occur in blood vessels including those found at skeletal muscles, heart and liver
You want to create a drug that will decrease blood pressure by decreasing stimulation of the heart, with minimum side-effects. Which of the adrenergic receptors should you try to block?
beta-1 receptors
If you choose a drug that blocks both types of beta receptors, what side-effect might you expect to see?
asthma from narrowing of the bronchioles
What is basal activity?
constant input from both parasympathetic and sympathetic (not all or nothing)
also adrenals are never zero
What does basal activity enable us to do?
deliver a message to a specific tissue using direct nervous innervation or cover a wider range of targets by sending out a more generalised hormonal message but receptor is essential for response (sympathetic)
