1. Chapter 12, part 3
Neural tissue

2. SECTION 12-5 Synaptic Activity

3. Nerve impulse Action potential travels along an axon
Information passes from presynaptic neuron to postsynaptic cell

4. General properties of synapses
Electrical
Rare
Pre- and postsynaptic cells are bound by interlocking membrane proteins

5. General properties of synapses
Chemical synapses
More common
Excitatory neurotransmitters cause depolarization and promote action potential generation
Inhibitory neurotransmitters cause hyperpolarization and suppress action potentials

6. Cholinergic synapses Release acetylcholine (ACh)
Information flows across synaptic cleft
Synaptic delay occurs as calcium influx and neurotransmitter release take appreciable amounts of time
ACh broken down
Choline reabsorbed by presynaptic neurons and recycled
Synaptic fatigue occurs when stores of ACh are exhausted

7. Figure 12.19 The Function of a Cholinergic Synapse
PLAY
Animation: Overview of a cholinergic synapse
Figure

8. Figure 12.19 The Function of a Cholinergic Synapse

9. Other neurotransmitters
Adrenergic synapses release norepinephrine (NE)
Other important neurotransmitters include
Dopamine
Serotonin
GABA (gamma aminobutyric acid)

10. Neuromodulators
Influence post-synaptic cells response to neurotransmitter
Neurotransmitters can have direct or indirect effect on membrane potential
Can exert influence via lipid-soluble gases
PLAY
Animation: Synaptic potentials, cellular integration, and synaptic transmission

11. Figure 12.21 Neurotransmitter Functions
Figure 12.21a

12. Figure 12.21 Neurotransmitter Functions
Figure 12.21b

13. Figure 12.21 Neurotransmitter Functions
Figure 12.21c

14. SECTION 12-6 Information Processing

15. Information processing
Simplest level of information processing occurs at the cellular level
Excitatory and inhibitory potentials are integrated through interactions between postsynaptic potentials

16. Postsynaptic potentials
EPSP (excitatory postsynaptic potential) = depolarization
EPSP can combine through summation
Temporal summation
Spatial summation
IPSP (inhibitory postsynaptic potential) = hyperpolarization
Most important determinants of neural activity are EPSP / IPSP interactions

17. Figure 12.22 Temporal and Spatial Summation
Figure 12.22a

18. Figure 12.22 Temporal and Spatial Summation
Figure 12.22b

19. Figure 12.23 EPSP – IPSP Interactions

20. Presynaptic inhibition
GABA release at axoaxonal synapse inhibits opening calcium channels in synaptic knob
Reduces amount of neurotransmitter released when action potential arrives

21. Figure 12.24 Presynaptic Inhibition and Facilitation

22. Presynaptic facilitation
Activity at axoaxonal synapse increases amount of neurotransmitter released when action potential arrives
Enhances and prolongs the effect of the neurotransmitter

23. Figure 12.24 Presynaptic Inhibition and Facilitation

24. Rate of generation of action potentials
Neurotransmitters are either excitatory or inhibitory
Effect on initial membrane segment reflects an integration of all activity at that time
Neuromodulators alter the rate of release of neurotransmitters

25. Rate of generation of action potentials
Can be facilitated or inhibited by other extracellular chemicals
Effect of presynaptic neuron may be altered by other neurons
Degree of depolarization determines frequency of action potential generation

26. You should now be familiar with:
The two major divisions of the nervous system and their characteristics.
The structures/ functions of a typical neuron.
The location and function of neuroglia.
How resting potential is created and maintained.

27. You should now be familiar with:
The events in the generation and propagation of an action potential.
The structure / function of a synapse.
The major types of neurotransmitters and neuromodulators.
The processing of information in neural tissue.