A reflex arc: the story of a pin prick Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. Using the cards, arrange them to explain how a stimulus is detected and a response caused by the nervous system.

The Autonomic Nervous System Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. The autonomic nervous system is a division that is ‘self governing’. It controls the activities and responses of internal muscles and glands. This includes the heart. 1.Sympathetic Nervous System (stimulates effectors, increase HR, expends energy) 2.Parasympathetic Nervous System (inhibits effectors, decrease HR, conserves energy) These are antagonistic, they work against each other. When one is working, the other isn’t.

Stimulus and Response How do organisms produce a response against stimuli? StimulusResponse Receptors Coordinator Effector Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate.

Receptors for controlling Heart rate Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. Heart rate control is initiated by 2 types of stimuli: 1. Chemical changes in the blood (carbon dioxide levels) ◦ This is detected by Chemoreceptors When would you expect Carbon dioxide levels to increase? How would this effect the blood? 2. Pressure changes in the blood (high/low pressure) ◦ This is detected by baroreceptors When would you expect blood pressure to increase/decrease? What would be the response if blood pressure becomes high?

Co-ordinator: Medulla Oblongata: In the brain Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. This is a region of the brain that co-ordinates the response of increase/decrease in heart rate to a response. This has 2 centres: - a centre that increases heart rate controlled by the sympathetic system A centre that decreases heart rate controlled by the parasympathetic system

Effector: Sinoatrial node and heart muscle Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. The Sinoatrial node detects the impulses sent by the Medulla Oblongata. The sinoatrial node will respond by either decreasing or increasing the frequency of impulses along the heart muscle walls leading to a decrease or increase in heart rate.

Control by Chemoreceptors Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. 1.Chemoreceptors are found in the carotid arteries and aorta and they detect a low blood pH (High CO 2 ). 2.The chemoreceptors send impulses along the sensory neurone to the medulla oblongata. 3.The medulla oblongata so-ordinates a response by activating the centre that increases heart rate. 4.The centre increases the frequency of impulses along the sympathetic nervous system to the SA node in the heart. 5.This increases the Heart rate. 6.CO2 is removed faster in the lungs and blood pH returns to normal. 7.The chemoreceptors detect this once more and signal the Medulla again. 8.The centre that lowers HR is activated 9.Impulses are sent along the parasympathetic which once more reduces HR.

Control by Baroreceptors Learning Outcomes: Explain the roles of sensory neurones, motor neurones, the CNS, intermediate neurones, synapses in a reflex arc. Discuss the importance of reflex arcs to animals. Describe the role of the autonomic nervous system Explain the role of chemoreceptors and baroreceptors in controlling the heart rate. Baroreceptors are found in the carotid arteries and aorta and they detect a low/high blood pressure. When blood pressure is high: 1.The baroreceptors send impulses along the sensory neurone to the medulla oblongata. 2.The medulla oblongata co-ordinates a response by activating the centre that decreases heart rate. 3.The centre increases the frequency of impulses along the parasympathetic nervous system to the SA node in the heart. 4.This decreases the Heart rate. If blood pressure is low: 1.The baroreceptors detect this once more and signal the Medulla. 2.The centre that increases HR is activated 3.Impulses are sent along the sympathetic which increases HR.