LECTURE SEVENTEEN

THE NERVOUS SYSTEM INTEGRATES AND CONTROLS
BODY FUNCTIONS OVER SHORT PERIODS OF TIME
AND BY VERY SPECIFIC MECHANISMS



CILIATED PROTOZOANS HAVE NEUROFIBRILS THAT
MAKE UP AN INTERCILIARY NETWORK



COELENTERATES HAVE A NERVE NET WHICH IS A
TRUE NERVOUS SYSTEM BUT IT IS NON-POLAR

THE LACK OF POLARITY IS A FUNCTION OF THE
SYNAPSES



HIGHER ANIMALS HAVE POLAR NERVOUS SYSTEMS

THE POLARIZATION OF THE NERVOUS SYSTEM IN
ANIMALS PARALLELS THE DEVELOPMENT OF THE
BRAIN AND SPINAL CORD



THE HUMAN NERVOUS SYSTEM IS MADE UP OF
NEUROGLIA OR GLIAL CELLS AND NEURONS

A NEURON CONSISTS OF A CELL BODY, AXON AND
DENDRITES



ALL NEURONS ARE COVERED WITH MYELIN

A NODE OF RANVIER OCCURS AT BREAKS IN
THE MYELIN COAT ON A NEURON



A RESTING NEURON IS POLARIZED AND SHOWS THE
  RESTING MEMBRANE POTENTIAL



THE NEURON MAINTAINS THE RESTING MEMBRANE
POTENTIAL DUE TO THE PERMEABILITY OF THE
MEMBRANE AND ACTIVE TRANSPORT




A NERVE IMPULSE IS A DEPOLARIZATION FOLLOWED
BY A REPOLARIZATION OF THE MEMBRANE
WHICH IS CALLED AN ACTION POTENTIAL




AN ACTION POTENTIAL IS CAUSED BY A MOMENTARY
CHANGE IN THE PERMEABILITY OF THE MEMBRANE
OF THE NEURON
ACTIVE TRANSPORT THEN RESTORES THE MEMBRANE
TO ITS RESTING POTENTIAL



ANOTHER IMPULSE CAN NOT BE INDUCED DURING THE REFRACTORY PERIOD

AT THE END OF THE AXON IS THE SYNAPTIC KNOB
THE AREA OF THE NEXT NEURON BELOW THE
SYNAPTIC KNOB IS THE SUBSYNAPTIC MEMBRANE
BETWEEN THE SYNAPTIC KNOB AND SUBSYNAPTIC
MEMBRANE IS THE SYNAPTIC CLEFT

WITHIN THE SNYAPTIC KNOB ARE VESICLES THAT
CONTAIN NEUROTRANSMITTERS