control of heart rate

what causes heart to contract?

SAN produces electrical impulses that cause the heart to contract

what’s the control centre for heart rate?

cardiovascular centre in the medulla oblongata

heart rate is controlled to respond to internal stimuli, using receptors. what are the receptors involved in controlling heart rate?

baroreceptors

-detect changes in blood pressure

chemoreceptors

-detect changes in blood pH, CO₂ and O₂ levels

where are the receptors found?

-carotid arteries

-Aorta

what is the pH when CO₂ levels increases and decreases in blood. explain why?

increase

-pH decreases as more carbonic acid is formed

decrease

-pH increases as less carbonic acid is formed

control of heart rate in response to high and low blood pressure

HIGH PRESSURE

-baroreceptors detect high blood pressure

-Baroreceptors send impulses to the cardiovascular centre in the medulla oblongata

-the medulla oblongata sends nerve impulses along the parasympathetic neurones to the SAN

-the SAN sends less waves of electrical excitation

-this decreases heart rate

-blood pressure returns to normal

LOW PRESSURE

-baroreceptors detect low blood pressure

-Baroreceptors send impulses to the cardiovascular centre in the medulla oblongata

-the medulla oblongata sends nerve impulses along the sympathetic neurones to the SAN

-the SAN sends more waves of electrical excitation

-this increases heart rate

-blood pressure returns to normal

control of heart rate in response to high and low carbon dioxide concentration

HIGH CO₂ CONCENTRATION

-blood pH decreases

-chemoreceptors detect decreased pH

-chemoreceptors send impulses to the cardiovascular centre in the medulla oblongata

-the medulla oblongata sends nerve impulses along the sympathetic neurones to the SAN

-the SAN sends more waves of electrical excitation

-this increases heart rate

-this increases blood flow to the lungs which helps remove CO₂ quickly

-oxygen, carbon dioxide and pH levels return to normal

LOW CO₂ CONCENTRATION

-blood pH increases

-chemoreceptors detect increased pH

-chemoreceptors send impulses to the cardiovascular centre in the medulla oblongata

-the medulla oblongata sends nerve impulses along the parasympathetic neurones to the SAN

-the SAN sends less waves of electrical excitation

-this decreases heart rate

-oxygen, carbon dioxide and pH levels return to normal

how is heart rate controlled during intense exercise?

-respiration rate in muscles increase

-More CO2 is produced, increasing CO2 concentration in the blood

…. [same points of high CO2 conc]

control of heart rate by hormonal system

-adrenal glands release adrenaline

-increases heart rate