Heart Flashcards
(14 cards)
Myogenic
When a muscle (cardiac
muscle) can contract and relax
without receiving signals from
nerves
Sinoatrial
node
Located in right atrium and is known as the pacemaker
releases wave of depolarisation
across the atria, causing
muscles to contract
Atrioventricular
node
Located near the border of the
right/left ventricles within the
atria
releases another wave of
depolarisation after a short delay
when it detects the first wave
from the SAN
Bundle of His
A group of specialised muscle fibres in
the heart
located in the septum between the
ventricles
conducts the wave of depolarisation
from the AV node down the septum
→ passes the impulse to the Purkyne
fibres, causing ventricles to contract
from the base upwards
Purkyne fibres
Specialised conducting fibres in the
walls of the ventricles
receive the wave of depolarisation from
the Bundle of His
spread the impulse through the
ventricular muscle, causing it to
contract from the base upwards
→ ensures efficient pumping of blood
out of the heart
Role of non-
conductive
tissue
Found between the atria and
ventricles
Prevents the wave of depolarisation
from passing directly from atria to
ventricles
Forces the impulse to travel through
the AV node and Bundle of His
→ Creates a short delay, allowing the
atria to fully contract and fill the
ventricles before they contract
Importance of short
delay between SAN
and AVN waves of
depolarisation
Ensures enough time for atria to
pump all blood into ventricles
before the ventricles contract
Role of the
medulla
oblongata
Controls heart rate via the
autonomic nervous system
uses sympathetic and
parasympathetic nervous
system to control SAN rhythm
Chemoreceptors
Located in carotid artery and
aorta
responds to pH / CO2 conc.
changes
Baroreceptors
Located in carotid artery and
aorta
responds to pressure changes
Response to high
blood pressure
Baroreceptors in the aorta and
carotid arteries detect high pressure
Send more impulses to the medulla
oblongata
Medulla increases impulses along
parasympathetic neurones to the SAN
Acetylcholine is released → slows
SAN activity
→ Heart rate decreases, reducing
blood pressure
Response to low
blood pressure
Baroreceptors in the aorta and carotid
arteries detect low pressure
Send more impulses to the medulla
oblongata
Medulla increases impulses along
sympathetic neurones to the SAN
Noradrenaline is released → increases
SAN activity
→ Heart rate increases, raising blood
pressure
Response to
low blood pH
Chemoreceptors in the aorta and carotid
arteries detect high CO2 levels (low pH)
Send more impulses to the medulla
oblongata
Medulla increases impulses along
sympathetic neurones to the SAN
Noradrenaline is released → increases SAN
activity
→ Heart rate increases, removing more CO2
via the lungs and returning pH to normal
Response to
high blood pH
Chemoreceptors in the aorta and carotid
arteries detect low CO2 levels (high pH)
Send more impulses to the medulla
oblongata
Medulla increases impulses along
parasympathetic neurones to the SAN
Acetylcholine is released → slows SAN
activity
→ Heart rate decreases, allowing CO2 to
accumulate and pH to return to normal
