5 - Control of heart rate

Question 1

What is the Peripheral Nervous System (PNS) made up of?

Answer 1

The neurones that connect the CNS to the rest of the body

Question 2

What are the two different systems the PNS is made up of?

Answer 2

• The Somatic Nervous System

- The Autonomic Nervous System

Question 3

What does the Somatic Nervous system control?

Answer 3

Conscious activities

Question 4

What does the Autonomic Nervous System control?

Answer 4

Unconscious activities

Question 5

What are the two different systems the Autonomic Nervous System is made up of?

Answer 5

• The Sympathetic Nervous System

- The parasympathetic Nervous System

Question 6

What does the Parasympathetic Nervous System do?

Answer 6

It is the ‘rest and digest’ system that calms the body down

Question 7

What does the Sympathetic Nervous System do?

Answer 7

It is the ‘fight or flight’ system that gets the body ready for action

Question 8

What is myogenic contraction?

Answer 8

When muscle cells are able to contract and relax without receiving signals from nerves

Question 9

What is the SAN (Sino-atrial node)

Answer 9

A group of cells in the wall of the right atrium that set the rhythm of the heartbeat by sending out regular waves of electrical energy to the atrial wall

Question 10

What is the AVN (Atrioventricular node)

Answer 10

A group of cells in the heart wall that is responsible for passing waves of electrical activity from the SAN on to the bundle of His

Question 11

What is the bundle of His?

Answer 11

A group of muscle fibres in the heart, responsible for conducting waves of electrical activity from the AVN to the Purkyne fibres

Question 12

What is Purkyne fibres?

Answer 12

Fine muscle fibres in the heart that carry waves of electrical activity into the muscular walls of the right and left ventricles

Question 13

What is the medulla?

Answer 13

A part of the brain that controls heart rate

Question 14

Which receptors detect internal stimuli in order to alter heart rate?

Answer 14

• Pressure Receptors

- Chemical receptors

Question 15

Name the pressure receptor found in the heart. Where Is it specifically found and what are they stimulated by?

Answer 15

• Baroreceptors
• Found in the aorta and carotid arteries
• Stimulated by high and low blood pressure

Question 16

Name the chemical receptor found in the heart. In which parts of the heart is it found and what is its function?

Answer 16

• Chemoreceptor
• Found in the aorta, carotid arteries and the medulla
• They measure the oxygen levels in the blood and also carbon dioxide and PH (which are indicators of oxygen level)

Question 17

How is the heart rate controlled in response to. high blood pressure?

Answer 17

• Baroreceptors detect high blood pressure
• They send impulses along sensory neurones to the medulla
• Which then send impulses along parasympathetic neurones
• These secrete acetylcholine, which binds receptors to the SAN
• This causes the heart rate to slow down in order to reduce blood pressure

Question 18

How is the heart rate controlled in response to low blood pressure?

Answer 18

• Baroreceptors detect low blood pressure
• They sens impulses along the sensory neurone to the medulla
• Which sends impulses along sympathetic neurones
• These secrete noradrenaline which binds to receptors on the SAN
• This causes the heart rate to speed up in order to increase blood pressure

Question 19

How is the heart rate controlled in response to high blood Oxygen levels? (Low Carbon dioxide or high blood PH levels)

Answer 19

• Chemoreceptors detect chemical changes in the blood
• They send impulses along sensory neurones to the medulla
• These send impulses along parasympathetic neurones
• These secrete acetylcholine which binds to receptors on the SAN
• This causes the heart rate to decrease in order to return oxygen (or other levels) back to normal

Question 20

How is the heart rate controlled in response to low blood Oxygen levels? (High Carbon dioxide or low blood PH levels)

Answer 20

• Chemoreceptors detect chemical changes in the blood
• They send impulses along sensory neurones to the medulla
• These send impulses along sympathetic neurones
• These secrete noradrenaline which binds to receptors on the SAN
• This causes the heart rate to increase in order to return oxygen (or other levels) back to normal