ANS control of CVS

Question 1

what are the 2 divisions of the ANS?

Answer 1

sympathetic = fight or flight
parasympathetic = digestion and relaxation

Question 2

what is sympathetic innervation of the heart?

Answer 2

1. cardioacceleratory centre found in medulla controls heart rate
2. sympathetic nerve fibres send signal down spinal cord and hits T1-T4
3. signal sent to paravertebral ganglia
4. signals are then sent towards heart down a sympathetic nerve fibre
5. innervates SAN, AVN, ventricular myocardium
6. noradrenaline released and binds to beta-1 adrenoreceptors
7. in the SAN and AVN there is an increase in Na+ and Ca2+ influx allowing for increased depolarisation and increased HR
8. in the ventricular myocytes there is increased Ca2+ influx which increases contractility of heart

Question 3

what are the affects of sympathetic innervation on CVS?

Answer 3

increases HR
increases contractility

Question 4

what is parasympathetic innervation of heart?

Answer 4

1. cardioinhibitory centre in medulla activates sympathetic neurones which synapse with and activate the parasympathetic nervous system in the dorsal medulla
2. fires down the vagus nerve which innervates the SAN and AVN
3. acetylcholine is released and binds to muscarinic receptors
4. in the cells of the SAN + AVN there is efflux of K+ so takes longer for depolarisation to be reached so slows the HR

Question 5

what are the affect of sympathetic innervation of CVS?

Answer 5

decreased HR