8. Autonomic Nervous System Flashcards
How does the parasympathetic nervous system innervate the heart?
parasympathetic preganglionic fibres travel as the vagus nerve to the heart where they will synapse with postganglionic neurons in cardiac plexuses, with their postganglionic fibres passing to the SA and AV nodes only. This will result in a reduction of HR.
How does the sympathetic nervous system innervate the heart?
Sympathetic postganglionic (P.G) fibres arise from the cervical and upper thoracic portions of the sypathetic trunks and this P.G. fibres will pass through the cardiac plexuses and terminate on the SA and AV nodes and also the general myocardium. The activation of the cardio-acceleratory centre results in an increase in heart rate and an increased force of contraction of the cardiac muscle.
What is the function of the parasympathetic nervous system on the heart?
To decrease HR
What is the function of the sympathetic nervous system on the heart?
To increase HR
What is the basic difference between a cholinergic muscarinic receptor and a cholinergic nicotinic receptor?
Nicotinic: work by direct action on ion channels to affect postsynaptic membrane potential. Found on all postganglionic neurons of both the PNS and SNS, the motor-end plate of skeletal muscle and on the chromaffin cells of the adrenal medulla. Muscarinic: Work by altering G-Proteins/secondary messengers within target cells (Therefore indirectly altering (via secondary messengers) the ion channel)
What is the difference between alpha 1 and alpha 2 adrenoreceptors and target cell responses?
Alpha 1 receptors are found on BV’s smooth muscle (skin, gut) and gut sphincters. The mechanism of action involves G-proteins and the activation of phospholipase-C to increase intracellular free calcium. Effect is contraction.
What is the difference between beta1 and beta2 adrenoreceptors and target cell responses?
