CNS, Neurotransmitters & Synaptic Transmissions

CNS is made up of brain & spinal cord. The NS is brain, spinal cord and network of neurons. It is responsible for sending, receiving & interpreting info from all over the body.

The NS monitors & co-ordinates internal organ functions & responses to external enviro. Brain processes & interprets sensory info (eyes, ears, nose etc) sent from spinal cord via sensory neurons & output in form of behaviour (via motor neurons) Nerves send info via spinal cord.

As info hits the brain, the messages pass via electrical impulses. Neurons receive & transmit messages cell by cell in response to info.  Nerve impulses are electrical signals passed from neuron to neuron across synapses. Brain processes info to react, remember, think, plan & sends messages back to body through spinal cord.

Structure & role of Neuron:

Cell body – contains cell nucleus (housing genetic material). Cell body contains other materials to allow cell functioning (mitochondria)

Dendrites – Attached to the cell body that receive messages from other neurons in order to trigger action potential in cell.

Axon – an extensive cell body that passes electrical impulses towards axon terminal. Axon Hillock attaches Axon to cell body where impulse begins.

Myelin Sheath – is fatty deposit around the outside of axon that provides insulating layer which speeds up rate of message transference. Breaks in-between the Myelin Sheath called nodes of Ranvier.

At the end is the Axon terminal with terminal buttons on the ends. Axon terminal pass nerve impulse from cell body to parts of the body they control of activate. (neuron, muscle or gland) the button contains tiny vesicles that store neurotransmitters ready for synapse.

Action Potential:  is an electrical impulse which passes down the axon of the neuron which stimulates vesicles releasing NT.  This is a tiny electrical impulse that is triggered by a change in electrical potential of the Neuron.

Neurons have resting membrane potential (a slight negative charge) where positive atoms are outside neuron. When waves of + particles enter the neuron, this causes an action potential as it stimulated the neuron, forcing the – ones out. This gives impulse across myelin sheath. Eventually – neurons re-enter pushing proton out.