Transcript Peripheral Nervous System (PNS)

Control of heart rate
WAL:
An overview of how the heart rate is controlled
What role do chemical and
Some
pressure receptors play in the
process?
How does the autonomic nervous
Most system control heart rate?
All
What is the autonomic nervous system?
Starter – If the hormonal system
and nervous system had a fight who
would win and why?
Today we are covering from the
specification:
Pages 147-149 of your textbook
The Nervous System
Divided into two
systems:
1. The CNS – brain
and spinal cord
2. The Peripheral
Nervous System
(PNS) – pairs of
nerves
Nervous system
Nervous system
Peripheral
Nervous system
Central
Nervous system
Brain
Sensory
system
Spinal cord
Motor system
Voluntary system
Sympathetic
Autonomic system
Parasympathetic
Control of Heart Rate
Autonomic
Sympathetic
Positive stimulation
(speed up activity)
Parasympathetic
Inhibitory
(slows down activity)
Control of heart rate
Heart rate is controlled by the part of the brain
called the medulla oblongata
Has two centres:
1.Increases heart rate linked to the sinoatrial
node by the sympathetic nervous system
2.Decreases heart rate linked to the sinoatrial
node by the parasympathetic nervous system
The centre that is stimulated depends on:
•Chemical changes in the blood
•Pressure changes in the blood
Control by chemoreceptors
Found in the walls of the carotid artery
Sensitive to changes in the pH of the blood that
result from changes in carbon dioxide
concentration. (In solution CO2 forms an acid)
Control by chemoreceptors
1) When the blood has a higher than normal
concentration of CO2, pH decreases.
2) Chemoreceptors in the wall of the carotid
arteries and the aorta detect this and increase
the frequency of nervous impulses to the
centre in the medulla oblongata that increases
heart rate.
3) This centre increases the frequency of
impulses via the sympathetic nervous system to
the sinoatrial node, increasing heart rate.
Control by chemoreceptors
4) The increased blood flow that this causes leads
to more CO2 being removed in the lungs and so
the CO2 levels return to normal
5) As a consequence the pH of the blood rises to
normal and the chemoreceptors in the wall of
the carotid arteries and aorta reduce the
frequency of nerve impulses to the medulla
oblongata.
6) The medulla oblongata reduces the frequency
of impulses to the sinoatrial node, which
therefore decreases the heart rate to normal.
Control by pressure receptors
Pressure receptors occur within the walls of the
carotid arteries and the aorta. They operate as
follows:
When a blood pressure is higher than normal:
1) They transmit a nervous impulse to the
centre of the medulla oblongata that decreases
heart rate.
2) This centre sends impulses via the
parasympathetic nervous system to the sinoatrial
node of the heart, decreasing heart rate.
Control by pressure receptors
Pressure receptors occur within the walls of the
carotid arteries and the aorta. They operate as
follows:
http://www.youtube.com/watch?v=G2nLL_O_U7w
When a blood pressure is lower than normal:
1) They transmit a nervous impulse to the
centre of the medulla oblongata that increases
heart rate.
2) This centre sends impulses via the
sympathetic nervous system to the sinoatrial node
of the heart, increasing heart rate.
Modifying heartbeat
Carotid artery
Chemo receptors
Pressure
receptors
hypothalamus
Sinoatrial node
medulla
Atrioventricular node
Cardioinhibitory centre
Cardioacceleratory centre
Human circulation
Control of heart rate
WAL:
An overview of how the heart rate is controlled
What role do chemical and
Some
pressure receptors play in the
process?
How does the autonomic nervous
Most system control heart rate?
All
What is the autonomic nervous system?
Plenary– Answer the questions on page
149