*Nervous system

• Definition of the Nervous System

  Complex network of nerve cells that carry messages to and from the CNS to the body
• The CNS is made of the brain and spinal cord. It's function is to receive sensory information and control bodily responses.
• The Brain is divided into separate areas which have different functions. They range from higher level functions like controlling thought, decision making, speech control and balance.
• The Spinal Cord's function is to relay information between the brain and body
• The Peripheral NS is the nerves outside the CNS and has two main divisions: Somatic and Autonomic NS. It's function is to relay nerve impulses between the CNS and body
• The Somatic NS's function is to receive input from sense organs, send output to control voluntary muscle movement. It is comprised of sensory and motor neurons. It connects the CNS and sense organs
• The Autonomic NS's function is control internal organs and glands. It controls involuntary functions and only uses motor pathways. It has two separate divisions the Sympathetic and Parasympathetic NS
• The sympathetic branch has an arousing effect on the body and is responsible for preparing the body for fight or flight.
• The parasympathetic branch has a calming effect on the body and restores it back to homeostasis after a period of excitation.
• Sensory Neuron: Structure

  Long dendrites, short axons. Unipolar - only transmits information
• Sensory Neuron: Function

  Afferent nerve cell. Function is to carry sensory impulses from sense organs to the CNS
• Relay Neuron: Structure

  Short Dendrites, short axons. Multipolar - sends and receives information
• Relay Neuron: Function

  To connect with other neurons. It is only found in the CNS. It analyses the sensation and decides how to respond
• Motor Neuron: Structure

  Short dendrites, long axons. Multipolar - send and receives information.
• Motor neuron: Function

  Efferent nerve cell. Transmits nerve impulses from the CNS to muscles or glands
• The difference between NTs and Hormones

  NTs are produced within neurons and pass very quickly from one neuron, across the synaptic cleft to another nearby neuron whereas hormones are secreted by glands and travel less quickly through the bloodstream to often quite distant target organs