2.85 describe the structure and functioning of a simple reflex arc illustrated by the withdrawalof a finger from a hot object

2.85 describe the structure and functioning of a simple reflex arc illustrated by the withdrawalof a finger from a hot object

The stimulus (the finger touching the hot object) is detected by temperature or pain receptors in the skin. these generate impulses in sensory neurones. the impulses enter the central nervous system through a part of the spinal cord called the dorsal root. in the spinal cord the sensory neurones connect by synapses with short relay nerones, which in turn connect with motor neurones. the motor neurones emerge from the spinal cord through the ventral root, and send impulses back out to the muscles of the arm. these muscles then contract pulling the arm and therefor the finger away from the harmful stimulus. 

2.84 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

2.84 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses


the impulses that travel along a neuron are not an electrical current they are a result of the movement of ions out an in of the neurone. these impulses can travel at speeds between 10 and 100 m/s which is fast enough to produce a rapid response. 

2.83 recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

The central nervous system consists of the brain and the spinal cord.
The central nervous system or CNS is a intricate network of nerve cells and nerve fibers throughout the body. Its function is to interpret, store, and respond to information received from inside the body and outside the body. The CNS is responsible for processing information gathered from the rest of the nerves and transmitting instructions to the body. Messages to and from the CNS are carried by the nerves of the nervous system.

2.82 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

2.77b Thermoregulation

2.77a Thermoregulation

2.76 Sensitivity