L8- ANS Flashcards
A) What is the Autonomic nervous system a division of?
b) What does the ANS do?
a) Peripheral nervous system
b) - works automatically to regulate/control all involuntary functions
- Functions: Blood pressure, heart rate, breathing rate, body temp, digestion, metabolism, h20 balance etc
a) What are the divisions of the ANS ?
b) What are each divisions function?
a) Sympathetic nervous system and peripheral nervous system (sometimes enteric)
b)
1. Sympathetic: responds to stressful situations; fight or flight
- increase HR, Force of contraction (inotropy), BP, dilation of bronchi, dilation of pupils, inhibits saliva secretion
- Parasympathetic: responds to ordinary situations; rest and digest
- lower HR, BP, contraction of bronchi, increased saliva secretion
What are the two main neurotransmitters found in the ANS?
- Acetylcholine (ACh)
2. Noradrenaline (NA)= Norepinephrine
What are the 5 anatomical divisions of the brainstem/spinal cord?
- Medullary
- Cranial
- Thoracic
- Lumbar
- Sacral
a) What type of neurons make up the ANS?
b) Cxtics of these in each division of the ANS
a) Motor neurones that are made up of preganglionic myelinated neurones and post ganglionic unmyelinated neurones
- Pre ganglionic celll bodies in CNS
- post ganglionic cell bodies in autonomic ganglia in PNS
b)
- Sympathetic:
- Short preganglionic and long post ganglionic - Parasympathetic:
- Long preganglionic and short post ganglionic
a) Where do the neurones of each division originate?
b) Where are the ganglia of each found?
a)
- Sympathetic:
- preganglionic short myelinated fibres originate in the: lateral horn in T1–> L2 cord segments (lumbar and thoracic cord) - Parasympathetic:
- preganglionic long myelinated fibres originate in the: lateral horn of medulla and s2-s4 sacral cord segments
b)
- paravertebral chain (sympathetic chain)
- Innervated tissues
Compare the Pre and Post ganglionic neurone neurotransmitter release in
a) Sympathetic neurones
b) Parasympathetic neurones
ALL PREGANGLIONIC NEURONES ARE CHOLINERGIC= use ACh as neurotransmitter therefore:
a) Sympathetic
1. Preganglionic neurones:
- release ACh, act on NACh (nicotinic ACh receptors) on post ganglion
2. Post ganglionic neurones: noradrenergic
- release noradrenaline, acts on alpha or beta adrenoceptors in target (effector) tissue (some are cholinergic tho)
b) Parasympathetic:
1. Preganglionic neurones:
- release ACh, act on NACh (nicotinic ACh receptors) on post ganglion
2. Post ganglionic neurones: cholinergic
- release ACh which acts on mACh (muscarinic) receptors in target (effector) tissue
Which sympathetic post ganglionic neurones arent noradrenergic?
- Specialised ones e.g. those innervating sweat glands, hair follicles
- they are cholinergic
What are some examples of other transmitters found in the ANS?
- Non-adrenergic, non-cholinergic (NANC) transmitters:
- ATP, Nitric oxide (NO), Serotonin
What does the enteric nervous system do?
Control the GI system independently of the CNS
How are adrenal glands different in their neurotransmission?
- They are sympathetic
- Their preganglionic neurone releases ACh, acts on NACHr on post ganglionic neurones
- The postganglionic neurones are different!!!
- They differentiate to form neurosecretory chromaffin cells
- They are present in the adrenal medulla
- they release adrenaline (epinephrine) directly into the blood stream
What are the names of the postganglionic sympathetic neurones in the adrenal medulla
Chromaffin cells- secrete adrenaline
Outline the result of parasympathetic release of ACh in the following: (where u can name specific receptors)
a) Eyes
b) Lacrimal glands
c) Salivary glands
d) Heart
e) Lungs
f) Liver
a) Constrict pupils
b) M1, M3: increased secretion
c) M1,M3: Stimulates salivation
d) M2 Muscarinic: decrease heart rate
e) M3: contract/constrict bronchi smooth muscle
f) Stimulates bile release
Outline the result of sympathetic release of Noradenaline in the following: (where u can name specific receptors)
a) Eyes
b) Salivary glands
c) Heart
d) Lungs
e) Stomach
f) Liver
g) Arterioles
h) Adrenal glands
a) Dilate pupils
b) Inhibit salivation
c) B1-adrenoceptors: increase heart rate
d) B2-adrenoceptors: bronchioles dilation
e) B2-adrenoceptors: dilation of intestines
f) Glucose release
g) Alpha1 adrenoceptors: contraction
h) secrete adrenaline
What is the differing roles in pre-synaptic and post-synaptic receptors?
Pre-synaptic receptors can control the release of neurotransmitter into the synapse, post synaptic receptors control the response in target tissues
How is Acetylcholine
a) synthesised
b) Degraded?
a) acetyl CoA + choline —> ACh + coenzyme A
- Catalysed by: choline acetyl transferase (CAT)
b) ACh –> acetate + choline
- catalysed by acetyl choline esterase
What are the 3 fates of ACh?
- Recycled
- Degraded by AChE
- Attached to post synaptic receptors
What are the two ways in which we can pharmacologically intervene to alter ANS activity?
- Manipulate cholinergic function
2. Manipulate adrenergic function
Major drug classes that affect Cholinergic transmission?
- Ganglion-blocking drugs at nACHrs: trimethaphan, used to control hypotension
- Cholinesterase inhibitors: decrease ACh degradation e.g. pyridostigmine to treat myasthensia gravis (allows more Ach to bind) and donepezil to treat alzhemiers
- Muscarinic ACh receptor agonists: pilocarpine (treat glaucoma, intraocular pressure) and bethanechol (stimulate bladder emptying)
- Muscarinic ACh receptor antagonists; Ipratropium and tiotropium to treat some forms of asthma and COPD
What is the problem with a lack of selectivity of cholinergic drugs?
Unwanted side effects occur
a) What is “SLUDGE”?
b) Spell it out
a) - Pathological effects of massive discharge of the parasympathetic nervous system
- due to chronic over stimulation of muscarinic ACh receptors
- irreversible deactivation of AChE, raises ACh levels
b)
- Salivation: stimulation of salivary glands
- Lacrimation: stimulation of lacrimal glands
- Urination: relaxation of urethral internal muscle and detrusor muscle contraction
- Defecation
- GI upset: smooth muscle tone changes- diarrhoea
- Emesis; vomiting
a) When would you see sludge syndrome?
b) How could it be treated?
a) - drug overdose
- ingestion of magic mushrooms
- exposure to organophosphorus insectisides
b) - Atropine, pralidoxime or other anti-cholinergic agents
a) How is noradrenaline synthesised?
b) Where do adrenoceptors in the ANS occur?
c) What is the structure of them related to function?
a) Tyrosine –> Dopa –> dopamine –> noradrenaline
b) Post-ganglionic sympathetic nerves
c) - highly branching axonal network with numerous varicosities, each a specialised site for calcium depdendant noradrenaline release
What is the fate of released noradrenaline?
- NA diffuses across synapse and interacts with adrenoceptors on post synaptic memb
- NA interacts with presynaptic receptors to regualte processes in nerve terminal
- Metabolism: taken up into vesicles and metabolised
What are the 2 enzymes that can metabolise noradrenaline
- monoamine oxidase (MAO)
2. Catechol-O-methyltransferase (COMT)
What are the major drug classes that are used to affect adrenergic transmission?
- B-2-adrenoceptor-selective agonists e.g. salbutamol: used in asthma to reverse/oppose bronchoconstriction
- A-2-adrenoceptor selective antagonists (e.g. doxazosin) and B-1- adrenoceptor-selective antagonists (e.g. atenolol) used to treat hypertension
What are the main categories of drugs that are used to treat asthma and why?
- M3- Muscarinic antagonists e.g. ipratropium
- Block muscarinic receptors in the airways so that ACh cannot bind, prevents innervation of these, hence prevent constriction of bronchi - B2-adrenoceptor agonists: e.g. Salbutamol
- bind to b2-adrenoceptors in the airways, stimulate sympathetic innervation of airways and hence dilates bronchioles to allow more airway in and out
a) What is thyrotoxicosis?
b) What are the symptoms
c) Drugs?
a) Excess thyroid hormone in body
b) - Increased heart rate
- increased sweating
- muscle aches
- anxiety
c) Beta blockers to lower heart rate e.g. propanolol and atenolol
What are the main categories of drugs that are used to treat hypertension and why?
Hypertension = high blood pressure
- A-1 adrenoceptor selective antagonists (e.g. doxazosin)- block adrenaline from binding hence block innervation of arterioles hence prevent arteriole contraction to lower BP
(found in arterioles) - B-1- adrenoceptor- selective antagonists (e.g. atenolol)
- these receptors are found in the heart
- hence these drugs bind to them and block adrenaline from binding
- prevent heart rate from increasing hence lower bP
