Regulation of heart rate and blood pressure Flashcards
Where is the cardiovascular centre located?
In the MO
What is the cadriovascular centre?
What do chemoreceptors monitor?
chemical changes in blood
What are baroreceptors?
monitor stretching of major arteries and veins (blood pressure)
‣ located in arch of aorta and carotid arteries
Where do sympathetic neurones originate?
MO and extend into the spinal cord
Where do cardiac accelerator nerves extend out in the heart?
sympathetic cardiac accelerator nerves extend out to SAN, AVN & most portions of the myocardium
What do impulses in the cardiac accelerator nerves trigger?
Impulses in these nerves trigger the release of adrenaline which binds to β-1 receptors on cardiac muscle fibres
What effects does the binding of adrenaline to β-1 receptors on cardiac muscle fibres have?
In SAN (& AVN) fibres, adrenaline speeds up rate of spontaneous depolarisation 2.
In contractile fibres throughout atria & ventricles, adrenaline enhances Ca2+ entry through the Ca2+ channels, increasing contractility
How do parasympathetic nerve fibres reach the heart?
What do these fibres do in the heart?
Reach heart via left and right vagus (X) nerves ‣ Vagal axons terminate in the SAN, AVN & atrial myocardium
‣ Release acetylcholine
◦ decreases heart rate by slowing the rate of spontaneous depolarisation
Which hormones regulate the heart’s pumping effectiveness and what do they do?
‣ Adrenaline and noradrenaline enhance heart’s pumping effectiveness
◦ increase heart rate
◦ increase contractility
‣ Thyroid hormones
◦ Increase heart rate
◦ Increase cardiac contractility
What effect does elevated K+ or Na+ have on the heart?
Decrease heart rate and contractility
What effect does excess Na+ have on the heart?
blocks Ca2+ inflow during cardiac action potentials decreasing force of contraction
What does excess K+ have on the heart?
Blocks generation of action potentials
What effect does a moderate increase in interstitial Ca2+ have on the heart?
Speeds heart rate and strengthens heartbeat
