nervous system

• • Enable the rapid transmission of electrochemical impulses to specific locations in the body
• • The nervous system consists of specialised cells called neurons (nerve cells)
• • Central nervous system (CNS), brain and spinal cord (interneurons)
• • Peripheral nervous system (PNS) – nerves which link the CNS to the body’s receptors and effectors (sensory and motor neurons)
• • Neurons are classified according to their function and the direction in which nerve impulses are carried
• • Sensory (or afferent)-- transmits information from sensory receptors to the CNS
• • Motor (or efferent)-- transmits information from the CNS to effectors (muscles or glands) 
• • A nerve impulse only travels in 1 direction: dendrite→ axon terminal
• • Neurons are separated by a small junction called a synapse. When a nerve impulse reaches a neuron's axon terminal, it triggers neurotransmitter release. These are chemical molecules that travel across the synapse, bind to receptors on the dendrite of the next neuron and stimulate a nerve impulse
• • Neural pathways are excited by the stimulation of sensory receptors. When these receptors are triggered, they pass the signal onto neurons, which then pass the signal onto effectors. Effectors work to counteract the detected change, therefore maintaining homeostasis within the organism