neural control of the heart

Question 1

what are the 4 central processing centres

Answer 1

1. medullary cardiovascular centor
2. hypothalamus
3. motor cortex
4. higher centres ie limbic system

Question 2

what can emotional stress do to alter CVS

Answer 2

limbic centre outflow = override reflex

input to both hypothalamus and medulla

Question 3

what is the CVS centre component

Answer 3

1. RVLM: sympathoexcitatory neurons, synapse to preganglionic neuron at IML. tonic activity
2. CVLM: inhibit RVLM neuron, inhibit preganglionic neuron at the spinal cord. no tonic outflow, no direct cvs innervation

Question 4

what is special about the motor cortex

what is the function of the nerve originating here?

Answer 4

origins of sympathetic cholinergic nerve

fight flight: skeletal muscle arteriole and skin overlying it ONLY
- great reduction in TPR

Question 5

where is the vagal outflow and how does it interact with the medullary centre

Answer 5

• dorsal motor vagal nuclei
• reciprocal relationship with the RVLM
• no tonic discharge, activated by afferent

Question 6

what structures do the
parasympathetic
sympathetic innervate

Answer 6

parasympathetic:
NODAL AND ATRIAL only = affects rate not contractility
little blood vessel innervation = no change in TPR

sympathetic: atrial, ventricle ALL blood vessels, nodal tissue
= rate contractility and TPR increases

Question 7

different sympathetic response of 1. arterioles

2. veins

Answer 7

a1 a2 receptors

• concentric VSM arrangement = arterioles = TPR
• longitudinal VSM arrangement = veins = compliance

Question 8

3 ways to alter heart rate

Answer 8

1. steepness of pacemaker potential (K conductance in pacemaker phase)
2. threshold level
3. degree of hyperpolarisation

Question 9

how does sympathetic activity affet CVS (LEFT AND RIGHT)

Answer 9

left: ventricle innervation = contractility
right: nodal innervation: increases heart rate

Question 10

relationship between sympathetic innervation and funny channels

Answer 10

b1 receptor: AC = cAMP
Na funnel channels: hyperpolarisation activated and cAMP gated

= cAMP opens Na channels sooner no need to wat for hyperpolarisation = steep pacemaker potential

Question 11

mechanism of vagal influence on heart rate

Answer 11

increases K conductance in BOTH repolarisation and pacemaker potential phase

• Ach dependent K channels activated, on top of the normal ones
• increase K conductance
  = hyperpolarisation and sooner repolarisation and shallow slope
• increases AV conductance