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The Nervous systemExplain how a boy is able to react when he comes into contact with a hot object

1ObjectivesThis presentation seeks to:

Define the nervous systemDistinguish between the two parts of the nervous systemUnderstand how the body detects and responds to stimuliUnderstand the pathway for detecting and responding to stimuli

2The nervous system is a system of organs that coordinates voluntary and involuntary actions and transmits signals in response to stimuli

1) Central nervous system2)peripheral nervous system

3The Central Nervous System (CNS)

made up of the brain and spinal cord and functions to send orders to other parts of the body in order to execute specific functions

4Peripheral nervous system (PNS)Detects stimuli and sends impulses to the CNS using cranial and spinal nerves

Consists of the nerves and ganglia outside the brain and spinal cord5

A change in the environment is called a stimulus.Actions taken by the body in order to co-operate with a stimulus are called responses.The body detects stimuli by other parts called receptors and respond to it through effectors.

6Reflexes are the bodys rapid automatic responses to a stimulus which is not under the voluntary control of the brain; an involuntary action.

The simplest nervous pathway taken by nerve impulses in a reflex action is called a reflex arc.

7

Reflexes usually have five (and always four) separate parts:A sensor;A sensory nerve that carries the message from the sensor to the spinal cord;An interneuron-a relay nerve (Some reflexes bypass the interneuron; others go via three or four interneurons.);A motor nerve that carries the message from the spinal cord to the muscle;A muscle fibre that contracts.

Nocireceptors (pain receptors) in the boys dermis or epidermis are activated by tissue damage and detect the heat stimulus after he touches the hot object.

The pain receptor synapses with a sensory neuron which carries the impulse to the CNS which synapses with an interneuron.The interneuron synapses with a motor neuron which carries the nerve impulse to the effector, the arm muscles.

Reference

BooksRamesar, Myda. Biology Unit 2 for CAPE, Cambridge University Press, 2011

Online Sourceshttp://www.asu.edu/courses/pgs461/Reflexes%20Arcs_PGS%20461.pdf http://www.positivehealth.com/article/chiropractic/reflex-reactions-our-body-s-rapid-defence-mechanism http://capebiologyashes.weebly.com/unit-two.html http://www.mydr.com.au/pain/pain-and-how-you-sense-it