Neurons

• Neurons are nerve cells that receive and transmit impulses to and from cells through electrical and chemical signals. There are 100 billion neurons in the brain and 1 billion neurons in the spinal cord. All behaviour is brought about by neural activty as its How the brain and spinal cord interact
• motor neurons start in the central nervous system, they carry impulses from the CNS to other areas of the body and control muscles. when stimulated, the motor neuron releases neurotransmitters that bind to receptors on the muscle and trigger muscle movement. muscle relaxation is caused by the inhibition of the motor neuron. they are multipolar, as they send and receive imoulses from many sources
• relay neurons lie between sensory and motor neurons and connect sensory and motor neurons. they are found solely within the brain and spinal cord. they are multipolar, as they send and receive impulses from many sources
• sensory neurons transmit nerve impulses from sensory receptors to the brain and spinal cord. these impulses begin at sensory receptors. when impulses reach the brain, they are translated into sensations eg : pain. not all sensory information travels as far as the brain, some neurons terminate in the spinal cord allowing reflex action without involving the brain. they are unipolar, they only transmit impulses not receive