Topic 6—A: Stimuli and Responses- 5. Control of heart rate Flashcards
What two different systems is the nervous system split into?
- The central nervous system.
- Peripheral nervous system.
What is the central nervous system made up of?
- It is made up of the brain and spinal cord
What is the peripheral nervous system made up of?
- It is made up of the neurones that connect the central nervous system to the rest of the body
What are the two different systems in the peripheral nervous system?
- Somatic.
- Autonomic.
What is the somatic nervous system?
- It controls conscious activities
Example- running, playing video games
What is the autonomic nervous system?
- Controls unconscious activities
Example- digestion
What is the autonomic nervous system split into?
- Sympathetic nervous system.
- Parasympathetic nervous system.
Sympathetic nervous system
- ‘fight or flight’ system
- Gets the body ready for action
Parasympathetic nervous system
- ‘rest and digest’ system
- Calms the body down
What is cardiac (heart) muscle?
Myogenic
Definition of myogenic
- It can contract and relax without receiving signals from nerves
- Pattern of contractions controls the regular heartbeat
Control of heart beat
- process starts in the sinoatrial node which is a small mass of tissue in the wall of the right atrium
- SAN initiates a wave of excitation that spreads across the atria making them contract (systole)
- there is a layer of non-conductive tissue that prevents the impulse spreading to the ventricles
- Instead, these waves of electrical activity are transferred from the SAN to the Atrio ventricular node (AVN)
- the AVN initiates a second nervous impulse that spreads down the bundle of his and then around the purkinje fires at the base of the ventricles
- This makes the ventricles contract (systole)
Sympathetic
- Accelerates heart
- Stimulates glucose release by liver
- Relaxes bronchi
- Heart rate quickens
Parasympathetic
- Inhibits heart
- Construct bronchi
- constrict bladder
- slows down heart rate
Medulla oblongata
- region of brain with a centre to increase and a centre to decrease heart rate
Pressure receptors
- They are called Baroreceptors
- They are located in aorta and carotid arteries
- The stimulated by high/low blood pressure
Chemical receptors
- They are called chemo receptors
- they are located in the aorta carotid arteries and in the Medulla
- they detect changes in pH
What happens when electrical impulses from receptors are sent to the medulla along sensory neurones?
- the Medulla processes the information and sends impulses to the SAN along sympathetic or parasympathetic neurones
High blood pressure
- baroreceptors detect high blood pressure
- Stimulates baroreceptors to increase the frequency of electrical impulses to the centre of the medulla
- heart rate decreases as the Medulla increases frequency of impulses along the parasympathetic nervous system
- when the impulse reaches the end of the para-sympathetic nervous system acetyl choline diffuses across the synapse to the SAN by binding to receptors which decreases the frequency of electrical impulses
- This lowers the heart rate
Low blood pressure
- Baro receptors detect low blood pressure
- Stimulates baro receptors to increase the frequency of electrical impulses to the centre of the Medulla
- heart rate increases as the medulla increases the frequency of impulses along the sympathetic nervous system
- when the impulse reaches the end of the sympathetic nervous system, nor adrenaline diffuses across the synapse to the SAN which increases the frequency of electrical impulses
- This increases heart rate
High blood pH level
- Chemo receptors detect chemical changes in the blood
- stimulates chemoreceptors to increase the frequency of electrical impulses to the centre of the medulla.
- Heart rate decreases as the medulla increases the frequency of impulses along the parasympathetic nervous system.
- When the impulse reaches the end of the parasympathetic nervous system, acetylene choline diffuses across the synapse to the SAN by binding to receptors which decreases the frequency of electrical impulses
- This lowers the heart rate
Low blood ph levels
- Chemoreceptors detect chemical changes in the blood
- Stimulates chemoreceptors to increase the frequency of electrical impulses to the centre of the medulla
- Heart rate increases as the medulla increases the frequency of impulses along the sympathetic nervous system
- When the impulse reaches the end of the sympathetic nervous system, nor adrenaline diffuses across the synapse to the SAN which increases