Receptors to change heart rate Flashcards
Describe the sympathetic control of heart rate.
The sympathetic cardiac nerve releases noradrenaline which binds to the β1-adrenergic receptors on the pacemaker cells in the SA node.
When noradrenaline binds to the β1-adrenergic receptors on the pacemaker cells in the SA node, what happens? (what process is this part of?)
This is to increase the heart rate.
Binding to this receptor causes a rise in cyclic AMP which is a secondary signalling molecule. This directly increases funny Na+ current so more Na+ enters the cell, and activates protein kinase A
When noradrenaline binds to the β1-adrenergic receptors on the pacemaker cells in the SA node and PKA is activated, what does PKA phosphorylate?
(what process is this part of?)
This is to increase the heart rate
PKA phosphorylates late-phase T-type Ca2+ channels which means that more Ca2+ enters the cell.
PKA also phosphorylates K+ channels which increases the repolarising current which shortens the duration of the AP as repolarisation occurs faster.
What is the overall effect of the sympathetic stimulation affecting the heart rate?
By increasing the amount of Na+ and Ca2+ in the cell, we can start from a less negative potential and depolarise more quickly. This means we increase the slope of the pre-potential which means that action potentials are more likely to occur, and they occur more quickly which increases the heart rate
What is an increase in the heart rate called?
Tachycardia
Describe the parasympathetic control of heart rate.
Acetylcholine is released from the vagus nerve onto muscarinic receptors on the pacemaker cells in the SA node
When ACh binds to the muscarinic receptors on the pacemaker cells in the SA node, what happens? (what process is this part of?)
This is to decrease heart rate.
This causes a fall in cyclic AMP which means that there is less PKA activity and reduced funny Na+ current
When ACh binds to the muscarinic receptors on the pacemaker cells in the SA node and PKA is not-activated, what happens?
(what process is this part of?)
This is to decrease heart rate.
Because there is less funny Na+ current, there is less Na+ entering the cell, there is going to be less activation of T-type Ca2+ channels and K+ channels which means that there is less Ca2+ entering the cells and less K+ leaving from these receptors
As well a reducing funny Na+ current, T-type Ca2+ current and K+ current through specific channels, what else does the binding of ACh to the muscarinic receptor on the pacemaker cells in the SA node do and what is the effect of this? What process is this part of?
This is to decrease heart rate.
As well as doing these things, it also activates ACh-sensitive K+ channels. This means that there is hyperpolarisation in the cell
What is the overall effect of the parasympathetic stimulation affecting the heart rate?
By decreasing the amount of Na+ and Ca2+ entering, and increasing the amount of K+ leaving the cell, we can start from a more negative potential and so depolarisation occurs more slowly. This means we decrease the slope of the pre-potential which means that action potentials are less likely to occur, and they occur more slowly which decreases the heart rate
What is a decrease in heart rate called?
Bradycardia
What is a hormone what can increase the heart rate?
adrenaline
What is a hormone that can decrease the heart rate?
acetylcholine
Adrenaline acts hormonally the same was as the _________ nervous system
sympathetic
Acetylcholine acts hormonally the same way as the __________ nervous system
parasympathetic
