B6

Organisms with many cells need to be able to send messages between cells in parts of the body. As multicellualar orgainsims evolve so did the communcation system. There are two types of them and each carry different messages. 

The nervous system is where it send messages using neurons and are specialised organs called the brain and the spinal cord. Neurons are used for fast repsonses when a change needs to happen quickly. ex. dropping a hot object

The other communication system is producing hormones  which are long lasting. Hormones are chemicals and their effect is slower than nuerons but the long lasting response is much more useful than the neurons which last a short period of time. ex. teenagers going through puberty. 

Neurons conduct electricity and there are sensory and motor neurons and relay or intermediate neurons

Sensory neurons connect to the receptors and detect change in the environment such as heat or pressure with the brain and the spinal cord in the central nervous system.

Motor neurons connect the brain and the effector cells such as a gland or muscle to create the response such as movement.

The central nervous system is the CNS and is made up of the brain and the spinal cord. They make the decisions for the rest of the body. In this is the processing centre where information is recieved and processed by the receptors and then coordinates a response. The pheripheral system is the PNS and it is made of sensory and motor neurons. The CNS is connected to all parts of the body via the PNS.

Sensory neurone is the neurones taht carry impulses from the receptors to the CNS.

Motor neurons carry impulses from the CNS to the effectors.

Effectors are the muscles and glands which respond to the nervous impulses. ex. ADH hormone or pitutary gland. 

Receptors are the cells that detect the stimuli and ex retina in the light receptor cells or sound and taste receptors.

Hormones are produced by the glands. Insulin is a hormone made in the pancreas and targets the liver and muscles to store glucose. 

STIMULUS ---> RECEPTOR ---> SENSORY NEURONE ---> CNS ---> MOTOR NEURONE ---> EFFECTOR ---> RESPONSE

Nerouons are never cells and they connect up the nervous system and link the receptor cellsto the effector cells. They have three main parts:

• The cell body is where the cell nucleus is kept and contols what is going in and out of it and dendrites wich have branched fibres that detect the change in the environment called stimuli that start the electrical signal in the cell. 
• The axon is a long extension of the cell which carries the electrical impulse and its surrounded by fatty myelin sheath. 
• Motor and end plates in a muslce allow the connection of another cell which could be another neuron or cell creating the effector for a response 

The infotmation is transmitted around the body by electrical impulses.

1) The electrical impulse pass along the axon of the…