heart rate control

Question 1

what is the importance of the role of pumping blood around the circulatory system

Answer 1

• transport of oxygen and nutrients such as glucose, fatty acids and amino acids to the tissues
• removal of waste products such as carbon dioxide from the tissues to prevent accumulation that can become toxic
• transport of urea to the kidneys
• distribute heat around the body or deliver it to the skin to be radiated away

Question 2

how can heart rate action be modified

Answer 2

• raising or lowering the heart rate, this is the number of beats per minute
• altering the force of the contractions of ventricular walls
• altering the stroke volumne

Question 3

what does adrenaline do to the heart rate

Answer 3

increases teh heart rate

Question 4

the atrial muscle has a….

Answer 4

higher myogenic rate than the ventricular msucle

- two chambers contract in a coordinated fashion or the heart rate will be ineffective

Question 5

control of the heart rate by the cardiovascular centre

Answer 5

• frequency of excitation from the SAN can be altered by the output from the cardiovascular centre in the medulla oblongata
• nerves from the cardiovascular centre in the medulla oblongata of the SAN, they are from the autonomic system
• action potentials sent down the sympathetic nerve cause the release of the neurotransmitter noradrenaline at the SAN this increases the heart rat e
• action potentials sent down the vagus nerve release the neurotransmitter acetylcholine which reduces the heart rate

Question 6

environmental factors that can influence the heart rate

Answer 6

sensory input to the cardiovascular centre include

• stretch receptors in the muscles detect movement of the limbs, these send impulses to the cardiovascular centre, informing it that extra oxygen may soon be needed leading to the increase in heart rate
• chemoreceptors in the carotid arties, the aorta and the brain monitor the ph of the blood - muscles produce more co2 when we exercise and sme of this reacts with the water in the blood plasma to produce a weak acid - affects the transport of oxygen
• concentration of carbon dioxide in the blood, when we stop exercising the concentration of carbon dioxide in the blood falls and this reduces the activity of the accelerator pathway thereofre it decreases the heart rate
• stretch receptors in the walls of the carotid sinus monitor blood pressure - increase in blood pressure is detected by stretch recepotrs and if blood pressure rises too hihg then the stretch receptors send a action potentail to the cardiovascular centre reducing heart rate

Question 7

artificial control

Answer 7

• PACEMAKER fitted
• delivers and electrical impulse to the heart muscle, implanted under the skin and fat on the chest
• artificial pacemaker may be connected to the SAN or directly to the ventricle muscle