control of heart rate Flashcards
What 2 systems is the nervous system divided into?
The Central Nervous System (CNS) - brain and spinal cord
The Peripheral Nervous System (PNS) - pairs of nerves
What part of the system controls heart rate? [5]
Nervous System
Peripheral Nervous System
Motor System
Autonomic System
Sympathetic OR Parasympathetic Nervous System
What three structures control the heart rate?
SAN - sinoatrial node
AVN - atrioventricular node
Bundle of His & Purkinje fibres - fibres that carry the impulse
Bundle of His
Nerve fibres stretch from atrioventricular node to Purkinje fibres, carrying and impulse
Purkinje Fibres
Muscle fibres in the ventricular wall, carrying an impulse and causing muscle contraction
How does the heart contract? [4]
- SAN sends a nerve impulse across the
atria of the heart, causing them to contract - An insulating layer lies across the atria and ventricles
- Meaning the impulse can only pass through the AVN and down the Purkyne
tissue (through the septum of the heart) - This carries the impulse to the bottom of the ventricles and causes contraction upwards
How is the heart rate controlled?
Sympathetic Nervous System - Positive stimulation (speed up activity - Fight or flight)
Parasympathetic Nervous System - Inhibitory (slows down activity)
What part of the brain is the heart rate controlled by?
medulla oblongata
What are the names of the two cardiovascular centres in the medulla oblongata?
The cardioaccelaratory centre
The cardioinhibitory centre
Role of the Cardioacceleratory Centre [3]
- Increases heart
rate - By increasing frequency of impulses to the sinoatrial node by the sympathetic nervous system
- via the accelerator nerve
Role of the Cardioinhibitory Centre [3]
- Decreases heart rate
- By increasing frequency of nerve impulses to the sinoatrial node by the parasympathetic nervous
system - via the vagus nerve
How does the body know to alter the heart?
Stimuli detected by:
- chemoreceptors
- pressure receptors
Control by Chemoreceptors [7]
Stimulus = Decrease in blood pH caused by increased release of CO2 in respiration
- Found in the walls of the aorta and the carotid artery
- Chemoreceptors detect stimulus and sends impulses to the cardioacceleratory centre
- Via the sympathetic nervous system
- The frequency of nerve impulses to the SAN
increases
- The SAN increases the heart rate
- Causing more CO2 to be removed from the blood, so the
stimulus is removed
- The chemoreceptors send less impulses
to the SAN
Control by Pressure Receptors [5]
Pressure receptors occur within the walls of the carotid arteries and the aorta
Stimulus = blood pressure is higher than normal
- Pressure receptors transmit more nerve impulses to the cardioinhibitory centre
- The parasympathetic nervous system sends more impulses to the SAN to slow the heart rate
Stimulus = blood pressure is lower than normal
- Pressure receptors transmit more nerve impulses to the cardioacceleratory centre
- The sympathetic nervous system sends more impulses to the SAN to speed up the
heart rate
Suggest the effects of intense exercise on control of heart rate [5]
- Blood carbon dioxide levels increase
- Blood pH decreases
- Chemoreceptors transmit more impulses to
cardioacceleratory centre - Sympathetic NS sends more impulses to SAN
- Heart rate increases
