The Autonomic Nervous System 1 Flashcards
Two components of the ANS?
Sympathetic NS - fight or flight
Parasympathetic NS - rest and digest
Parasympathetic nervous system features and roles?
Controls a number of functions in non-stressful conditions
Opposes actions of the SNS in many cases
Features of sympathetic nerves?
Arise in thoracic and lumbar regions of spinal cord
Pre-ganglionic fibre SHORT
Post-ganglionic fibre LONG
Ganglia are located in a chain close to vertebral column (paravertebral ganglia) or closer to target tissue (coeliac ganglion)
Features of parasympathetic nerves?
Arise in cranial and sacral regions of spinal cord
Pre-ganglionic fibre LONG
Post-ganglionic fibre SHORT
Ganglia are located in or very close to effector cell/target tissue
What is important about the connections between sympathetic ganglia?
Allows for MASS ACTIVATION
How does the adrenal medulla act as a modified ganglion?
Made up of secretory cells (chromaffin cells) innervated by sympathetic pre-ganglionic fibres
These cells release catecholamines directly into the bloodstream to travel to their target via the circulation
The two effects of sympathetic stimulation of the heart and their overall combined effect?
Inotropic effect - Increased force of contraction
Chronotropic effect - Increased heart rate
Overall effect of increasing cardiac output
Effects and mechanism of sympathetic control of total peripheral resistance?
Increased sympathetic activity increases general vasoconstriction and increased TPR and vice versa
Leads to an increase in mean arterial blood pressure as well
Controllers of vasodilation?
Mainly due to decreased sympathetic tone
Can be caused by sympathetic activity to skeletal muscle blood vessels, localised vasodilators, or increased parasympathetic stimulation to certain blood vessels to discrete glands/organs
Effect of sympathetic and parasympathetic activity on GI tract?
Sympathetic - Inhibits peristalsis - Generally decreases motility and tone - Contraction of sphincters - Inhibits secretory activity Parasympathetic - Stimulates peristalsis - Opposite effects to sympathetic
Sympathetic effects on the lungs?
Dilates bronchi and bronchioles
Sympathetic and parasympathetic effects on penis?
Parasympathetic - erection
Sympathetic - flaccidity and ejaculation
Sympathetic and parasympathetic effects on eye muscles?
Sympathetic - Contracts radial muscles, pupil dilation
Parasympathetic - Contracts papillary sphincter for pupil contraction, contracts ciliary muscle for near vision
What is the smooth muscle called that surrounds the bladder and what is the main influence on it?
Detrussor muscle
Parasympathetic control is main influence
Internal and external sphincters controlled by?
Internal sphincter - sympathetic control
External sphincter - motor nerves/voluntary control
What is the micturition reflex?
Registering of increased pressure in the bladder leading to relaxation of internal and external sphincters and urination
Leads to decreased bladder pressure
Mechanism of micturition reflex control?
Increased pressure in bladder increases afferent activity to spinal cord
Increased parasympathetic activity via pelvic nerve leads to contraction of depressor muscle
Decreased sympathetic activity via the hypogastric nerve relaxes the internal sphincter
Central inhibition of voluntary control via the pudendal nerve relaxes the external sphincter and begins urination leading to drop in pressure in the bladder
The 3 neurotransmitters used by the ANS?
Acetylcholine
Noradrenaline
Adrenaline
Parasympathetic pre- and post-ganglionic fibre neurotransmitter released?
Cholinergic (acetylcholine)
Sympathetic pre- and post-ganglionic fibre neurotransmitter released?
Pre-ganglionic - cholinergic
Post-ganglionic - noradrenergic (noradrenaline)
What are the two sympathetic nervous system exceptions in neurotransmitter release?
Adrenal medulla - innervated by pre-ganglionic cholinergic fibres, acts as its own release site, releases catecholamines into circulation
Sweat glands - innervated by post-ganglionic CHOLINERGIC fibres
What are the two types of acetylcholine receptors?
Nicotinic
Muscarinic
What are the two types of adrenoreceptors? (receptors for both adrenaline and noradrenaline)
Alpha and Beta
What type of receptor is the ganglionic acetylcholine receptor?
Nicotinic receptor
Ligand-gated ion channels
What type of acetylcholine receptor is used at effector organs?
Muscarinic receptor
G-protein coupled receptor
