cardiac control in mammals 9.8

what region of the brain controls the heart

medulla oblongata

The centre that is linked to increasing heart rate is linked t which branch of the autonomic nervous system

sympathetic

The centre that is linked to decreasing heart rate is linked t which branch of the autonomic nervous system

parasympathetic

how does the body know which centre to activate

using chemoreceptors and baroreceptors

these detect the changes in the chemical composition and the pressure of the blood. eg pressure increases and CO2 increases

what do baroreceptors do

These are a more of stretch receptors the more the arteries stretch the higher the blood pressure.

( all we needed to know is that they detect changes in pressure)

what do chemoreceptors

these measure chemical changes in the blood especially change in ph due to increased carbon dioxide levels.

what does myogenic mean

something myogenic means starts in the muscle itself, not from nerves or hormones. in this case contracts start without an impulse from a nerve

what is the equation for cardiac output

cardiac output= heart rate x stroke volume

what is the role of the CNS as it doesn’t initiate heartbeat how not autonomic

it controls both the heart rate and the stroke volume

describe how the heart rate is increased

event ( stressful one) eg running from a lion

stimulus = change in O2 concentration in the blood as well as increase in CO2 levels so change in Ph ( more acidic). This increases blood pressure.

Receptors= This change in pressure and change in chemicals is detected by baroreceptors and chemoreceptors in the aorta and in the carotid arteries.

Coordinator= sensory neurones transmit these signals to the cardiac centre in the medulla in this case the centre that increases heart rate. e

Effector =the signals are transmitted down the sympathetic nervous system to the SAN

response =change in heart rate /increase

describe how the heart rate is decreased

event (calming down again )

stimulus = change in O2 concentration in the blood as well as decrease in CO2 levels so change in Ph (less acidic ). Also a decrease in blood pressure.

Receptors= This change in pressure and change in chemicals is detected by baroreceptors and chemoreceptors in the aorta and in the carotid arteries.

Coordinator= sensory neurones transmit these signals to the cardiac centre in the medulla in this case the centre that decreases heart rate.

Effector =the signals are transmitted down the parasympathetic nervous system to the SAN

response =change in heart rate / decraese

1. sinoatrial node ( pacemaker\0

2. atrioventricular node

3. bundle branches

4. bundle of His

5. Purkinje fibres