control of heart rate

what makes up the peripheral nervous system?

sensory and motor nervous system

what makes up the motor nervous system?

voluntary and autonomic nervous system

what does it mean if the cardiac muscle is myogenic?

contracts without receiving electrical impulses from nerves

but rate of contraction is controlled

SAN?

sinoatrial node

cluster of cells that acts a pacemaker

right atrium

AVN?

atrioventricular node

in atria near border of right + left ventricle

bundle of His? 

transmits impulses from AVN down septum to bottom of ventricles 

runs along septum 

purkyne fibre location?

ventricle walls

how is the heart stimulated to transmit a wave of electrical activity/contract?

• SAN acts as pacemaker - releases regular waves of electrical activity/depolarisation across atria

• atria contracts

• non-conducting tissue between atria/ventricles prevents impulse passing directly to ventricles, preventing immediate ventricle contraction

• depolarisation reaches AVN, which delays impulse, allowing atria to fully contract + empty

• AVN sends wave of electrical activity down bundle of His, conducting wave between ventricles to apex, where it branches into purkyne tissue

• ventricle contract from base up

where are chemo + pressure receptors located? 

in aorta and carotid arteries 

what happens when baroreceptors detect fall in blood pressure/chemoreceptors detect fall in blood pH/CO2 conc?

• impulses sent to medulla/control centre

• which sends more frequent impulses to sympathetic neurones

• so more frequent impulses sent from SAN and to/from AVN

• heart contracts more frequently, increasing heart rate

what happens when baroreceptors detect rise in blood pressure/chemoreceptors detect rise in blood pH/CO2 conc?

• impulses sent to medulla/control centre

• which send more frequent impulses to SAN via parasympathetic neurones

• less frequent impulses sent from SAN and to/from AVN

• so heart contract less, lowering heart rate

issues with high blood pressure?

may damage artery walls

issues with low blood pressure?

may cause insufficient removal of waste + supply of oxygenated blood to respiring cells

how may blood pH be lowered?

increased respiration increases CO2/lactic acid conc. in blood

excess acid may denature enzymes so has to be removed

how does the body respond to exercise? 

• increased metabolic activity = more respiration so more CO2/lactic acid produced, lowering blood pH 

• chemoreceptors undergo process to increase heart rate

• increasing blood flow to remove CO2/lactic acid faster