32.1 - Neural extrinsic regulation of Cardiac Performance- Sympathetic and parasympathetic effects. Humeral factors affecting cardiac performance.

sections

neural extrinsic regulation of cardiac performance - sympathetic

neural extrinsic regulation of cardiac performance - parasympathetic

parasympathetic nerves

sympathetic effects

humoral factors affecting cardiac performance

neural extrinsic regulation of cardiac performance - sympathetic

Sympathetic nerves liberate norepinephrine which stimulates the heart increasing its rate and sense of contraction

Both sets of nerve supply the SAN and AVN and affect the heart rate by their influence in the sinoatrial node (pacemaker)

neural extrinsic regulation of cardiac performance - parasympathetic

Parasympathetic nerves- liberate acetylcholine which inhibits the heart- slowing down its rate.

Both sets of nerve supply the SAN and AVN and affect the heart rate by their influence in the sinoatrial node (pacemaker)

parasympathetic nerves

• The vagus nerve is the parasympathetic nerve that innervates the SAN.

• It secretes neurotransmitter acetylcholine which then binds to muscorinic receptors in the SA-node cells.

• Parasympathetic- atria

• Activation of SNS -atria and ventricle

• Heart (Beta) The ANS has 5 effects on the heart:

  • Inotropic: strength of contraction

  • Bathmotropic: excitation of cardiomyocyte

  • Chronotropic: frequency of contraction

  • Dromotropic: conduction of impulses through cardiomyocytes

  • Tonotropic: tone of cardiomyocyte

Parasympathetic effect: All the above five effects decrease

during exercise emotional stress dehydration causes vasoconstriction of arteries and veins mediated by alpha adrenoreceptors and increase heart rate contractile rate of relaxation and conduction velocity by beta 1 adrenoreceptors.

sympathetic effects

• Heart (Beta) The ANS has 5 effects on the heart:

  • Inotropic: strength of contraction

  • Bathmotropic: excitation of cardiomyocyte

  • Chronotropic: frequency of contraction

  • Dromotropic: conduction of impulses through cardiomyocytes

  • Tonotropic: tone of cardiomyocyte

Sympathetic effect: All the above five effects increase

during exercise emotional stress dehydration causes vasoconstriction of arteries and veins mediated by alpha adrenoreceptors and increase heart rate contractile rate of relaxation and conduction velocity by beta 1 adrenoreceptors.

humoral factors affecting cardiac performance

• Hormones which increase the heart rate include thyroxine – T4, triiodothyrine-T3 which are secreted by the thyroid gland

• nerve stimulation leads to the release of epinephrine- adrenaline which binds to receptors on the SAN resulting in an increase in the heart rate