Control of heart rate Flashcards
heart must meet
changing demands of tissues
changing demands of tissues
exercise
metabolic demands of tissues
3 ways for heart to accomodate changing demands
change heart rate
changing force of contractions
changing stroke volume(volume of blood pumped for heart)
cardiac muscle is found in
heart
cardiac muscle is
myogenic
myogenic
can initiate own contraction at regular intervals
atria has higher myogenic rate than
ventricles(contract faster than ventricles)
sa node sends wave of
exertion throughout atria
sa node exertion causes
atria to contract
electric impulse SA node sent out would
reach band of insulating tissue between atria and ventricle
all the force
and exertion passes through the septum and AVN which is also located in the septum
electrical impulse then travel down to
apex of heart through perkinje fibres
after perkinje fibres exertion would eventually spread upwards from
apex to ventricles making them to contract
cardiac muscle responds
directly to adrenaline(increases heart rate)
At Rest
No adrenalin in heart
Just SAN control heart rate
fires 60-80 bpm
firing maybe altered by cardiovascular centre in the medulla
SAN
Internal pacemaker
medulla-SAN
Accelarans nerve
vagus nerve
Accelerans nerve
sympathetic nervous system
responsible for increasing heart rate
fight or flight response
Vagus nerve
Parasympathetic
decreases heart rate
which two muscles are antaganostic
accalarans
vagus
control comes from increasing firing of these
two nerves
if one fires it does not mean the other stops firing
it just mean its firing slower than the other nerve
cardiovascular centre stimuli
muscle stretch receptor
chemoreceptor
muscle receptor in the wall of carotid sinus
muscle stretch receptor
when exercising,
muscle will be moving
movt will be detected by stretch receptor
which will communicate to CVC
if stretchings a lot CVC will increase firing rate
Chemoreceptors can be found in:-
Carotid Arteries
Aorta
Brain
chemoreceptor monitors
PH of blood.Once CO2 gets in blood it forms carbonic acid with the h2o.it later dissasociates into hydrogen carbonate and hydrogen ions then will affect PH,exercising more will have low PH
Barroreceptor
muscle receptor in wall of carotid sinus.It monitors bp.If bp too high it can be dangerous to the organs and increase the risk of diseases like CVD.It tells CVC to start increasing rate of vagus nerve
if all the 3 responses fails
then people may need artificial pacemaker
artificial pacemaker
connected directly to SA nerve or ventricular muscle.Takes over the role of SAN and delivers impulse to the heart muscle/
artificial pacemaker is
usually implanted under skin and fat of chest or sometimes within the cavity of chest
explain how atmosphere near volcano can lead to an increasing in breathing rate
conc of blood in the lung is high.
due to co2 conc ph becomes low and is detected by chemoreceptors carotid bodies,Aorta
brain.It communicates to cvc in medulla which sends impact through neurons for intercostal muscles and diaphragm.
suggest how an increase in breathing rate can help to reduce the conc of co2 in a person walking away from the volcano
inhaled air has low co2 . the co2 in blood is higher than in lungs so co2 moving down conc gradient
tissue that controls resting heart
SAN
what is measured by ECG
Electrical volume
describe how heart rate can be measured by nervous system
low ph is detected by chemoreceptor in caortic bodies
it communicates to medulla which activates accelerator nerve
give 1 diff and 1 sim between hormonal and nervous system
sim both involuntary diff hormonal is slower hormonal lasts longer
morphine reduces sensitivity of co2 in the blood.this affects breathing rate and can be cause death.suggest why high dose of morphine can cause death
co2 will not be removed from blood
carbonic acid increases,ph decreases
change not detected by chemoreceptor
so medulla not stimulated
