Neuroscience 9 - Physiology & Pharmacology of ANS Flashcards
List the functions of the parasympathetic system.
- Contracts pupils
- Stimulates flow of saliva
- Constricts bronci
- Slows heartbeat
- Stimulates peristalsis and secretion
- Stimulates bile release
- Contracts bladder
List the functions of the sympathetic system.
- Dilates pupils
- Inhibits salivation
- Relaxes the bronchi
- Accelerates heartbeat
- Inhibits peristalsis and secretion
- Stimulates glucose production and release
- Secretion of adrenaline and noradrenaline
- Inhibits bladder contraction
- Stimulates orgasm
Where do the nerves of the SNS come from?
- Thoracic 1 to lumbar 3
- Form a sympathetic chain
Where do nerves of the PNS come from?
- Cranial nerves III, VII, IX, X
- Sacral splanchnic nerves S2-4
What is the function of the 3rd cranial nerve?
Oculomotor (pupil constriction)
What is the function of the 7th cranial nerve?
Facial (salivation)
What is the function of the 9th cranial nerve?
Glossopharyngeal (salivation)
What is the function of the 10th cranial nerve?
Vagus (bradycardia, gastric motility, digestion)
Where do the parasympathetic nerves synapse?
At the effector organ
Where do the sympathetic nerves synapse?
- Synapse at ganglia outside of the organ, in the sympathetic chain
- Except for at the adrenal gland, where they have no synapse.
What is the pathway of neurones in the SNS?
- Presympathetic neuron in the CNS, to the intermediolateral cell column
- From the intermediolateral column, the nerve enters the ventral horn.
- Preganglionic neurone from spinal cord to sympathetic chain They enter the sympathetic chain via the white ramus communicans, where they meet the ganglion.
- Postganglionic neurone to effector, exiting via the grey ramus communicans.
What are the neurotransmitters used by parasympathetic neurones?
Both pre and post ganglionic use acetylcholine
What neyrotransmitters are used at the presympathetic neurones?
Glutamate
What neurotransmitters are used by preganglionic sympathetic neurons?
Acetylcholine
What neurotransmitters are used by post ganglionic sympathetic neurones?
- Noradrenaline is used at the heart, kidney and vessels
- Acetylcholine is used at the sweat glands
- Dopamine is used at the renal vessels
What neurotransmitters are used in the SNS at the adrenal gland?
- Acetylcholine is used at the adrenal gland
- This results in release of adrenaline or noradrenaline which affects the target organ?
What is noradrenaline?
A neurotransmitter and a hormone
What neurotransmitters are used in the somatic nervous system?
- Glutamate is used at the CNS
- Acetylcholine is used at the effector organ (eg. skeletal muscle)
List the stages of biosynthesis of noradrenaline.
- L-phenylalanine > L-tyrosine > L-DOPA > dopamine (cytoplasm)
- Dopamine > noradrenaline (vesicles)
List the stages of acetylcholine biosynthesis.
Acetate + choline > acetylcholine
- Forwards reaction via choline acetyltransferase
- Reverse reaction via acetylcholinesterase
Which receptors are involved in blood pressure regulation?
- Baroreceptors are present in the heart to detect stretch (mechanoreceptors).
- Aortic baroreceptors communicate via the vagus nerve
- Corotid baroreceptors (2) communicate via the 9th cranial nerve (glossopharyngeal).
What is the response to increased blood pressure in the heart?
- Baroreceptors increase firing
- Vagus nerve firing increases, this reduces the stroke volume, and therefore cardiac output
- Inhibition of the SNS increases the diameter of blood vessels to reduce total peripheral resistance
What is the baroreflex?
- The blood pressure that is viewed as “normal” (the set point) is shifted higher in hypertensive patients
- This means baroreceptors will maintain this higher blood pressure
How is GI function regulated?
- Performed by vagus nerve
- Sight of food, smell of food and the taste of food are enough to result in preparation of the GI tract for food.
What is the cephalic response?
- The response to food before you have even eaten it
- The pancreas releases a small amount of insulin
- Preparing of the stomach for food
Which receptors are present in the stomach?
- Mechanoreceptors detect distention of the stomach wall and tell the brain you’re eating via the vagus nerve, which increases the feeling of fullness.
- Chemoreceptors detect gut hormones
Which gut hormones are involved in satiety?
- GLP 1
- Peptide YY
- Cholecystokinin (CCK)
How does obesity affect feeling of fullness?
More food is required to make people who are obese feel full than is required to make lean people feel full.
Which area of the brain regulates respiration?
- The central respiratory centre in the brain stem.
- Pontine respiratory centre coordinates pattern of breathing
- Ventral group coordinates rhythmicity
- Dorsal group coordinates inspiration and control of the diaphragm
- Ventral + dorsal group makes medullary respiratory centre
What type of receptors are present in the lung?
- Mechanoreceptors in the lung (vagus nerve)
- Baroreceptors in the aorta or carotid baroreceptors in the heart (respond to decrease in oxygen, pH and an increase in CO2)
- Central chemoreceptors in the brainstem detect a drop in pH or a rise in CO2
Which spinal nerves are involved in regulation of respiration?
- C1 to C3 control the accessory muscles
- C3 to C5 control the viaphragm via the phrenic nerve
- T1 to T11 control the intercostal muscles
- T6 to L1 control the abdominal muscles
Describe the general structure of the bladder.
- External wall is the detrusor muscle
- There is an internal sphincter and an external sphincter
How is the bladder innervated?
- Detrusor muscle by S2-S4
- T10-T12 innervates the internal sphincter
- S2-S4 innervates the external sphincter (voluntary)
- Afferent innervation from S2-S4
What are the roles of the PNS and SNS in micturition?
- Activation of the PNS when the bladder is full causes the detrusor muscle to contract, and inhibits the SNS so the internal sphincter relaxes
- SNS causes internal sphincter to contract
- PNS contracts detrusor muscle
How does central regulation of autonomic function occur?
- NTS (nucleus tractus solitarius) is innervated by the vagus nerve (10) and glossopharyngeal nerve (9)
- Sends a signal to the hypothalamus, which coordinates the information and sends it back down to the dorsal motor nucleus of the vagus (DMNX)
- Some information goes directly to the intermediolateral cell column of the spinal cord.
- Information from higher brain areas can also control aspects like breathing voluntarily
What are the types of sympathetic receptors?
- All adrenoreceptors
- a1 (A, B, D)
- a2 (A, B, C)
- beta 1, beta 2
What are the types of parasympathetic receptors?
- Cholinoceptors
- Can be nicotinic or muscarinic
What are the types of channels present in the ANS?
G protein coupled receptors, and ion channels
Where are the nicotinic receptors present?
Nicotinic receptors are found:
- At neuromuscular junctions
- All autonomic ganglia
Where are the muscarinic receptors found?
- All postganglionic PNS neurons
- Stimulated by SNS at selected sites
What cholinergic drugs are there?
- Tubocurarine is a nicotinic receptor antagonist
- Atropine is a muscarinic receptor antagonist
What type of receptor are nicotinic receptors?
Ionotropic receptors
What type of receptors are muscarinic receptors?
G protein coupled receptors
What type of receptors are adrenergic receptors?
G protein coupled receptors
Where are a1, a2, B1 and B2 adrenergic receptors found?
- a1 causes smooth muscle contraction
- a2 presynaptic membrane
- B1 at the heart
- B2 causes smooth muscle relaxation
List some adrenergic drugs.
- Medetomidine is an a2 antagonist, so decrease noradrenaline release
- Doxazosin is an a1 antagonist (smooth muscle dilation)
- Atenolol is a B1 antagonist
- Salbutamol is a B2 antagonist (relaxes smooth muscle)
What is shy-drager syndrome?
- Synucleopathy with parkinsons disease and dementia
- Loss of intermediolateral cell bodies
What are the symptoms of shy-drager syndrome?
- Orthostatic hypotension
- Impotence (sexual dysfunction)
- Hypohidrosis (sweating)
- Dry mouth
- Incontinence
- Urinary retention
What is another name for shy-drager syndrome?
Multiple system atrophy
What causes primary hypertension?
Exaggerated sympathetic nerve activity to blood vessels and renal bed
What causes heart failure?
Increased sympathetic nerve activity to the renal bed, making the heart unableto pump sufficient blood to meet oxygen demand
What is the early sign of parkinsons disease?
Autonomic dysfunction - orthostatic hypotension and constipation
What is throacolumbar outflow.
The preganglionic fibres of the sympathetic system are found in the thoracic (T1-12) and upper lumbar (L1-3) spinal nerves
What is craniosacral outflow.
The preganglionic fibres of the parasympathetic system are found in cranial nerves and sacral spinal nerves
What is the sympathetic trunk?
- A chain of ganglia and connecting fibres lying next to the vertebrae for the entire length of the vertebral column.
- This arrangement allows dispersion of the sympathetic outflow from a small region of the spinal cord (T1-L3) to peripheral regions via all spinal nerves
