Autonomic Nervous System Flashcards
Neuroeffector sites/cells innervated by ANS
Smooth muscle
Cardiac muscle
Exocrine glands
2 important neurotransmitters in the ANS
Acetylcholine
Noradrenaline
ANS neurotransmitters
Nicotinic
Muscarinic
Adrenergic=sympathetic
Cholinergic= parasympathetic
Homeostasis
The tendency towards a relatively stable equilibrium between interdependent elements
Sympathetic ANS
Tends to activate organ
Parasympathetic ANS
Tends to inactivate organ
Both systems help maintain homeostasis in:
Adjustment to stress
Preparation for combat
Defecation
Urination
Digestion
Salivation
Adjustment to temperature changes
Protection of eyes against bright light
Respiration
Accommodation of near vision
Maintenance of blood pressure at optimal level
Parasympathetic: rest and digest
Decrease HR, B.P, Eyes adjust for light
Emptying of bowel, bladder
Airways constrict
Sympathetic: fight or flight
Increase HR, B.P, eyes adjust for dark
Digestion slowed
Airways opened
Neurotransmitter
A chemical substance which is released at the end of a nerve fibre by the arrival of a nerve impulse and, by diffusing across the synapse or junction, effects the transfer of the impulse to another nerve fibre, a muscle fibre or some structure
PARASYMPATHETIC NERVOUS SYSTEM
Has one neurotransmitter
>acetylcholine
Ach is responsible for the transmission of nerve impulses to effector cells od pns
Ach is easily destroyed by enzyme acetylcholinesterase(AchE)
Important neurotransmitters of the ANS
Acetylcholine and noradrenaline
The synapses of the neurotransmitters
Cholinergic
Adrenergic synapses
Acetylcholine receptors
Nicotinic receptors
Muscarinic receptors
Acetylcholine sites
All autonomic ganglia
Parasympathetic postganglionic terminals
Antagonists
Antagonists possess affinity but lack efficacy
They block receptor activation by agonists
Antagonists and agonists
Agonists: nicotine and muscarine
Antagonists: curare and atropine
IN THAT ORDER
Receptors: nicotinic receptor and muscarinic receptor
Curare
It is a poison and it can paralyse a person
Indirect acting cholinomimetics
Drug and biological toxins
Excessive release of Ach- latrodectism
Blocks release of Ach- botulism
Inhibit acetylcholinesterase enzyme
Latrotoxin( a toxin from the black widow spider)
Produces an explosive release of Ach, causing muscular spasm
Botulinum toxin
Prevents Ach release
It is very rarely responsible for serious food poisoning
No antivenom in SA
Causes paralysis
Get rid of wrinkles
Botulinum toxin indications
Hyperhidrosis of the axillae and palms- not permanent(sweat)
Type A toxin is used in the treatment blepharospasm (spasmodic eye closure) and hemi-facial spasms
Enzymatic degradation of Ach
- Synthesis of Ach
- Uptake into storage vesicles
- Release of neurotransmitters
- Binding to the receptor
5.Degradation of Ach
> Ach is rapidly hydrolysed by AchE
6.Recycling of choline
Drugs used to increase Ach conc.
Physostigmine
Neostigmine
Insecticides that inhibit AchE
Carbamates
Organophosphates
> they can cause poisoning
Muscarinic features (DUMBELS)
Diarrhoea
Urination
Miosis
Bronchospasm
Emesis
Lachrymation
Salivation
Muscarinic blockers
Ipratropium
Scopolamine
Atropine> the most known
Side effects of blockade of Ach at Muscarinic receptors
Dry mouth
Constipation
Tachycardia
Decreased sweating
Blurred vision
Confusion
Decreased urination
