ANS Flashcards
What is unique about the ANS’s regulation and what does it control?
It is not under conscious control
Controls:
Cardiac muscle (heart)
Smooth muscle
Internal organs
Skin
What nervous system is the ANS a division of?
The peripheral nervous system
What occurs to the pupil under parasympathetic and sympathetic control?
What occurs to heart rate under parasympathetic and sympathetic control?
What occurs to the stomach under parasympathetic and sympathetic control?
+Enteric NS has much more complex effects
Where do ANS visceral motor nuclei originate?
The hypothalamus
Where do ANS visceral motor neurones project to and what occurs there?
Brainstem or spinal cord
-Here they synapse with autonomic neurones(para+symp)
What is the outcome an increased BP detected by baroreceptors
Increased parasympathetic NS action and decreased sympathetic NS action
Outline the difference between the parasympathetic and sympathetic motor portions of the ANS and if there are any exceptions
Both are mainly comprised of 2 neurons-A pre and post ganglionic neuron
Sympathetic:
Short pre-ganglionic
Long post-ganglionic
-Ganglions close to spinal cord
Parasympathetic:
Long pre-ganglionic
Short post-ganglionic
-Ganglions close to effector tissues
Adrenal gland however does not have a ganglion
Which neurotransmitters are used in the effector portion of the ANS?
ACh in the parasympathetic branch
Sympathetic portion:
ACh in ganglion
Noradrenaline in the neurone/effector synapse
What does the adrenal gland secrete with sympathetic activation and why does this not act as a neurotransmitter
Adrenaline+SOME noradrenaline
-Is secreted into the bloodstream, not into a synapse
How are the lungs innervated through the ANS and how is this anomaly gotten around?
The lungs have no sympathetic innervation
-The release of adrenaline from sympathetic activation of the adrenal glands allows for more efficient lung function
What muscle contracts to put pressure on the bladder?
The detrusor muscle
Outline what occurs within the micturition reflex pathway and the innervation of the internal sphincter
Parasympathetic NS contracts the detrusor muscle
Sympathetic NS relaxes the internal sphincter
-Therefore at rest(para is dominant) the bladder will squeeze and the internal sphincter will stay shut, preventing unwanted urination
There is also somatic innervation of the internal sphincter, so peeing is under voluntary control
What type of receptor is present at ANS ganglia and how fast do they operate?
Ion channel receptors
FAST-VERY FAST(msecs)-These mediate all fast excitatory and inhibitory transmission
Where do you find the nicotinic acetylcholine receptors in the ANS?
In the ganglia and the neurone/adrenal gland synapse
What type of receptor is present at post-ganglionic neurone terminals and how fast do they operate?
G-protein coupled receptors
Muscarinic in parasympathetic
Adrenergic in sympathetic
What neurotransmitters are used to activate the g-protein coupled receptors and what are the effectors in this case?
Muscarinic: ACh
Adrenergic: Noradrenaline(From synapse or noradrenaline in blood)
Effectors may be enzymes (adenyl cyclase, phospholipase C, cGMP-PDE) or channels (e.g. Ca2+ or K+)
How are neurotransmitters generally re-uptaken from a synapse?
Either into pre-synaptic terminal or into a glial cell
How is ACh produced to be used in a synapse?
Choline enters the pre-synaptic terminal and combines with acetyl CoA and is converted into ACh by choline acetyl transferase
How is noradrenaline prepared from tyrosine for use in an adrenergic synapse
- Tyrosine converted to DOPA by tyrosine hydroxylase. DOPA converted to dopamine by DOPA decarboxlase
- Dopamine packaged into vesicles with dopamine β hydroxylase. Noradrenaline is the product
How is adrenaline function in an adrenergic synapse different from noradrenaline?
Noradrenaline converted to adrenaline in the cytoplasm by phenylethanol methyl transferase(PEMT)
