| What are the 2 divisions of the autonomic nervous system | Sympathetic --> flight or fight response
Parasympathetic --> eating, sexual arousal , urination , digestion etc. |
| What are ganglia | Cell bodies of neurons in the autonomic nervous system |
| What are some features of the parasympathetic ganglia and fibres | Generally the ganglia of the parasympathetic system are located close to, or sometimes within the structures controlled by the systems
The preganglionic fibres tend to be long and postganglionic fibres tend to be short
Also have cranio-sacral outflow |
| What are some features of the sympathetic ganglia and fibres | Preganglionic fibres of the sympathetic branch leave the CNS from the thoracic and lumbar regions - so called thoraco-lumbar outflow
Synapses between pre - and postganglionic neurons are mostly located in ganglia close to the spinal cord
So preganglionic fibres are short and post-ganglionic fibres long |
| What neurotransmitter, do preganglionic neurons release | Acetylcholine which acts on nicotinic ACh receptors on the postganglionic neurons which have ion channels |
| What transmitter is used in postganglionic neurons at sympathetic | Noradrengenic so they use noradrenaline except sweat glands that use ACh |
| What transmitter is used in postganglionic neurons in parasympathetic | Postganglionic parasympathetic neurons are usually cholinergic --> ACh |
| What is the function of chromaffin cells | Adrenal chromaffin cells release adrenaline which circulates in the bloodstream |
| What does the ANS do in the CVS | Heart rate
Force of contraction of the heart
Peripheral resistance of blood vessels
DOES NOT initiate the electrical activity in the heart |
| Where is the CVS control centre located | Medulla oblongata --> located in the brain stem |
| What are some inputs of the parasympathetic system to the heart | synapse with postganglionic cells on epicardial surface or within walls of heart at SA and AV node
Releases ACh
Acts on M2 receptors
Decreases heart rate
Decreased AV node conduction velocity |
| What are some inputs of the sympathetic system to the heart | Innervate SA node , AV node and myocardium
Releases noradrenaline
Acts on B1 adrenoreceptors
Increases heart rate
Increases force of contraction |
| Effect of sympathetic on pacemaker potentials | Increases the slope
Mediated by B1 receptors
G-protein coupled receptors (Gs ) Increase cAMP → ligand to HCN channel
Leads to the speeding up of pacemaker potentials |
| Effect of parasympathetic on pacemaker potentials | Decreases slope
mediated by M2 receptors
G-protein coupled receptors (Gi ) Increase K+ conductance and decrease cAMP |
| What is the simplified baroreceptor reflex | Baroreceptor → Afferent → medulla → efferent → effector ( heart and blood vessels ) |
| What happens to blood vessels when a1 adrenoreceptors are activated | Vasoconstriction --> due to increased Ca2+ By PKA which leads to contraction |
| What happens to blood vessel when B2 adrenoreceptors are activated | Activating β2 adrenoceptors causes vasodilation |
