1. Nervous System Function
Neurons and Neurotransmitters

2. Nervous System - Pathways
Sensory Nerves
Brain and Spinal Cord
Sensory Receptors
Somatic Nerves
(muscles)
Motor Nerves
Autonomic Nerves
(glands/organs)

3. Nervous System - Pathways
Sensory Nerve
Interneuron
Motor
Nerve

4. Supporting Cells (not neurons)
Microglial – phagocytize bacterial cells + debris
Oligodendrocytes – produce myelin sheath
Astrocytes – link blood and neurons helping in metabolism
Ependymal cells – cover inside of the ventricles

5. Neurons – Basic Structure
Nervous cells that conduct nerve/electrical impulses
Neuron Structures
Dendrite = receptive region conducts impulse to cell body
Axon = conducts impulse away from cell body
Myelin sheath = cells that insulate nerve impulse increasing its velocity
Node of Ranvier = narrow gap between cells of myelin sheath
Synapse = empty space/junction between neurons

6. Types of Neurons
Multipolar = many dendrites + one axon; found in CNS and motor neurons
Bipolar = one dendrite and one axon; found in eye and nose
Unipolar = single process extending from cell body; found in sensory neurons

7. Resting Membrane Potential
Neuron is polarized at rest
Interior is negative/Exterior is positive
Na+/K+ pump maintains polarity by moving Na+ out and K+ in
K+ can leave but Na+ can’t enter

8. Action Potential
Neuron depolarizes to send an electrical nerve impulse
Neuron becomes positive inside and negative outside as a result of ions moving
The momentary depolarization is quickly reversed and the neuron becomes re-polarized
The depolarization is called an action potential

9. Action Potential Action Potential is caused by movement of ions
Depolarization = Steps 1 + 2
Action Potential = Step 3
Repolarization = Steps 4, 5, 6

10. Action Potential
The resting membrane potential is negative and cell is polarized.
Stimulus causes Na+ and then K+ gates to open, inside of cell becomes positive and is depolarized.
Na+ gates close and K+ gates open, inside becomes repolarized as K+ leaves cell.

11. Action Potential to Nerve Impulse
Action potential produces a local current
This causes depolarization on adjacent membrane
The wave of action potentials travels down the neuron producing a nerve impulse

12. Action Potentials and Myelinated Neurons
Myelinated neurons allow action potentials to ‘jump’ between unmyelinated gaps (Node of Ranvier) along the neuron
Action potential and nerve impulse are faster
Myelin sheath acts as insulation prevents depolarization
Nodes of Ranvier are not insulated and can depolarize as a result

13. Neurotransmitters
Neurotransmitters are chemicals produced by the neuron and stored in sacs at axon terminal
Action potential stimulates release of neurotransmitters into the synapse (gap between neurons)
Neurotransmitters bind to receptor sites on adjacent neuron

14. Neurotransmitters
Neurotransmitters change the shape of receptors allowing movement of ions into neuron
Movement of positive ions (Na+) causes depolarization and an action potential
Neurotransmitters that allow this are called stimulatory

15. Neurotransmitters
Neurotransmitters can change the shape of receptors preventing movement of ions into neuron
Causes the interior of neuron to become more negative, preventing an action potential
Neurotransmitters that do this are called inhibitory

16. Neurotransmitters