Autonomic System Flashcards
What is the function of ANS?
Regulates involuntary body functions such as heart rate, digestion , respiratory rate, blood pressure
Allows pull and push signalling at targets such as muscle contractions and relaxation
Contains sympathetic and parasympathetic
Sympathetic nervous system
Activated during stress
Mass discharge signalling
Parasympathetic nervous system
Activated during rest
Discrete reflexes
What is the main transmitter in SNS?
Noradrenaline
Main transmitter in PNS?
Acetylcholine
Name the cranial nerve responsible for carrying parasympathetic fibres to the majority of thoracic and abdominal visceral?
Vagus nerve carries parasymapathetic fibres
What is the role of the parasympathetic nervous system in the body’s homeostasis?
The parasympathetic nervous system is responsible for promoting “rest and digest” activities. It conserves energy, slows heart rate, stimulates digestion, and promotes relaxation.
explain the “fight or flight” response and its physiological effects.
response is a physiological reaction triggered by the sympathetic nervous system in response to stress or perceived threats
Autonomic baroreceptor reflex:
Standing up after lying down - responsible for keeping your balance
Carotid artery blood pressure falls due to gravity- blood travels from aorta to feet
Vagal parasympathetic tone reduced
THEN…
Heart rate increases due to activation SNS
Systemic blood pressure rises
Bran oxygenation maintained
Target tissues in ANS?
Smooth muscle- vascular, visceral
Exocrine glands- sweat and salivary
Heart- rate and force of contraction
Liver- glucose usage
Explain synaptic transmission.
Action potential arrives at pre synaptic cleft. Action potential has to be above threshold to cause depolarisation. Sodium channels open one by one and the influx of sodium stimulates opening of calcium Channels, increased levels of calcium triggers the vesicle release and neurotransmitter diffuses across synaptic cleft to post synaptic cleft.
Neurotransmitter (ACh and noradrenaline ) depolarises membrane and post synaptic potential triggers a new action potential.
What is involved in cholinergic transmission ?
Process where neurotransmitter ACh released by pre synaptic neurons and produces a response
Nicotonic and muscarinic receptors
Ganglionic transmission- sites of drug action
Neuroeffector transmission- sites of drug action
What are the 2 acetylcholine receptors ?
Muscarinic and nicotinic receptors
What are the target proteins of muscarinic receptors ?
Adenylate cyclase
Phospholipase C
Ion channels
Drugs acting on muscarinic receptors - agonists
Agonists change receptor activity to produce response
Muscarinic agonists- acetylcholine, muscarine, carbachol
Effects- bradycardia and vasodilation- fall in blood pressure
Contraction of visceral smooth muscle
Exocrine secretion- pupillary constriction and decrease in pressure
