Central Nervous System - Brain and Spinal Cord
Peripheral Nervous System - Peripheral nerves and AUTONOMIC
INFORMATION GOING TO THE CNS IS CARRIED IN SENSORY OF EFFERENT NERVES
INFORMATION EXITING FROM THE CNS IS CARRIED IN MOTOR OR EFFERENT NERVES
Some neurons are specialised, but all neurons recieve and transmit information as Nerve Impulses
DENDRITES recieve information from other cells
AXONS generate impulses
Information is transmitted to other cells at the AXON TERMINAL
Myelin Sheath is used for Insulation
Neurons may need to be very long and protected so they are packaged into nerves alongside blood vessels and wrapped in connective tissue
NERVE TRUNKS are packageing for the nerve and may contain MIXED NERVES
Transmission of Information
Neurons are excitable tissues and their impulses generate Action Potentials.
When they are not generating impulses they are said to be in resting state.
During resting state the fluid inside the cell is different from the outside of cell and there is a difference of charge =MEMBRANE POTENTIAL
INTRACELLULAR fluid is more negative than EXTRACELLULAR fluid
Sodium/potassium ATPase pump maintains difference in charge.
Information transfer only generated when sufficient stimulus is recieved = THRESHOLD STIMULUS
All or nothing response followed by ABSOLUTE REFRACTORY PERIOD = NO STIMULUS WILL INITIATE
RELATIVE REFRACTORY PERIOD = MORE STIMULUS NEEDED.
Action Potential occurs when the resting membrane potential becomes more positive = Permeability of cell membrane changes to certain ions = CONDUCTION CHANGES
Sequence of events during an Action Potential
Increased membrane permeability to Sodium
Sodium moves into cell = DEPOLARISATION
Membrane potential increase potassium out = REPOLARISATION
Membrane potential below normal value = HYPERPOLARISATION
Action Potential starts at one end of axon down to axon terminal.
Adjacent sections depolarise die to current flow
speed = depend on neuron (myelinated or not)
Action Potentials only occur at weak points of the myelid called node of Ranvier. Not all axon depolarised.
Saltotory conduction jump.