Heart Rate Flashcards
Exercise chases increase in HR
Describe the role of receptors and nervous system in process
increased muscle activity during exercise
More CO2 produced by respiration
=lowered PH
chemoreceptors detect low ph
Increase impulses sent to medulla
Increase impulses sent to SAN
By sympathetic NS
Increased heart rate
both ventricles contract at the same time, how is this coordinated in the heart after initiation of heartbeat by the SAN?
Electrical activity only through AVN / bundle of His
Wave of electrical activity passes over / through both ventricles at the same time
How are blood pressure controlled by pressure receptors
High bp = pressure receptors transmit more nervous r impulses to centre in medulla oblongata = decrease HR
Centre sends impulses via parasympathetic NS to SAN = decrease rate of HB
Low bp = pressure receptors transmit more impulses to centre of medulla that increases HR - centre sends impulses via sympathetic NS to SAN = increased rate which heart beats
Where are pressure receptors located
Wishing the CAROTID arteries and aorta
Nerve connecting carotid artery’s to medulla is cut. The person does strenuous exercise - what may happen to their
A) heart rate
B) blood CO2 conc
Heart rate remains same as it was before exercise, AFTER EXERCISE, blood pressure rises and CO2 conc in blood rises (ph lowered)
= detected by osmoreceptors and pressure receptors in carotid arteries. No nerve impulses can be sent to centre of medulla that controls HR
Blood co2 con increases be cashed of increased resp in exercise
how does the atrioventricular valve maintain a unidirectional flow of blood
pressure above valve is higher than below the valve / pressure from the left atrium is higher than pressure in left ventricle
= valve opens
when pressure is higher in the left ventricle is higher than in the left atrium then the valve closes
how does caffeine increase heart rate (NS)
more impulses/ action potentials passed long the sympathetic NS
to the SAN = increased heart rate
damage to the myelin sheath of neurones can cause muscular paralysis - how?
-depolarisation occurs along the whole length of the axon (saltatory conduction)
- nerve impulses are slowed/ stopped
- weakens muscles (neuromuscular conjunction)
what is the cause of heart irregularities
fewer impulses along the sympathetic/ parasympathetic pathway
=fewer impulses from the medulla to the SAN
what is the SAN
sinoatrial node
- initial stimulus for contraction
- sends wave of electrical excitement to the atria so they contract
what are changes to the heart rate controlled by
medulla oblongata which has 2 centres:
- centre which increases heart rate (linked to the SAN by the sympathetic NS)
- centre which decreases heart rate (linked to the SAN by the parasympathetic NS)
what is the bundle of His and what is its role
made up by a series of specialised muscle fibres (Purkyne tissue)
- conducts wave of electrical excitement through AV septum to base of the ventricles
