1. C h a p t e r 12
Neural Tissue
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings

2. Nervous System Overview
Provides swift, brief responses to stimuli
Endocrine system
Adjusts metabolic operations and directs long-term changes
Nervous system includes
All the neural tissue of the body
Basic unit = neuron

3. Divisions of the Nervous system
CNS (Central Nervous system)
Brain and spinal cord
PNS (Peripheral Nervous system)
Neural tissue outside CNS
Afferent division brings sensory information from receptors
Efferent division carries motor commands to effectors
Efferent division includes somatic nervous system and autonomic nervous system

4. Figure 11.1 Functional Overview of the Nervous System

5. Neuron structure Perikaryon Neurofilaments, neurotubules, neurofibrils
Axon hillock
Soma
Axon
Collaterals with telodendria

6. Figure 11.2 The Anatomy of a Multipolar Neuron
Figure 11.2b

7. Synapse Site of intercellular communication
Neurotransmitters released from synaptic knob of presynaptic neuron

8. Figure 11.3 The Structure of a Typical Synapse

9. Neuron classification
Anatomical
Anaxonic
Unipolar
Bipolar
Multipolar

10. Figure 11.4 A Structural Classification of Neurons

11. Functional Sensory neurons
Deliver information from exteroceptors, interoceptors, or proprioceptors
Motor neurons
Form the efferent division of the PNS
Interneurons (association neurons)
Located entirely within the CNS
Distribute sensory input and coordinate motor output

12. Figure 11.5 A Functional Classification of Neurons

13. Neuroglia of the Central Nervous System
Four types of neuroglia in the CNS
Ependymal cells
Related to cerebrospinal fluid
Astrocytes
Largest and most numerous
Oligodendrocytes
Myelination of CNS axons
Microglia
Phagocytic cells

14. Figure 11.6 An Introduction to Neuroglia

15. Figure 11.7 Neuroglia in the CNS
Figure 11.7a

16. Figure 11.7 Neuroglia in the CNS
Figure 11.7b

17. Neuroglia of the Peripheral Nervous System
Two types of neuroglia in the PNS
Satellite cells
Surround neuron cell bodies within ganglia
Schwann cells
Ensheath axons in the PNS
PLAY
Animation: Nervous system anatomy review

18. The transmembrane potential
Electrochemical gradient
Sum of all chemical and electrical forces acting across the cell membrane
Sodium-potassium exchange pump stabilizes resting potential at ~70 mV

19. Figure 11.11 An Introduction to the Resting Potential

20. Figure 11.12 Electrochemical Gradients

21. Changes in the transmembrane potential
Membrane contains
Passive (leak) channels that are always open
Active (gated) channels that open and close in response to stimuli

22. Figure Gated Channels
Figure 11.13

23. Three types of active channels
Chemically regulated channels
Voltage-regulated channels
Mechanically regulated channels

24. Graded potential A change in potential that decreases with distance
Localized depolarization or hyperpolarization

25. Figure 11.14 Graded Potentials

26. Figure 11.14 Graded Potentials

27. Figure 11.15 Depolarization and Hyperpolarization

28. Action Potential
Appears when region of excitable membrane depolarizes to threshold
Steps involved
Membrane depolarization and sodium channel activation
Sodium channel inactivation
Potassium channel activation
Return to normal permeability

29. Figure 11.16 The Generation of an Action Potential

30. Characteristics of action potentials
Generation of action potential follows all-or-none principle
Refractory period lasts from time action potential begins until normal resting potential returns
Continuous propagation
spread of action potential across entire membrane in series of small steps
Salutatory propagation
action potential spreads from node to node, skipping internodal membrane

31. Figure 11.17 Propagation of an Action Potential along an Unmyelinated Axon

32. Figure 11.18 Saltatory Propagation along a Myelinated Axon

33. Figure 11.18 Saltatory Propagation along a Myelinated Axon

34. Axon classification Type A fibers Type B fibers Type C fibers
Based on diameter, myelination and propagation speed

35. Muscle action potential versus neural action potential
Muscle tissue has higher resting potential
Muscle tissue action potentials are longer lasting
Muscle tissue has slower propagation of action potentials
PLAY
Animation: The action potential

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

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

38. 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

39. 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

40. Overview of a Cholinergic Synapse
PLAY
Animation: Overview of a cholinergic synapse

41. Figure 11.19 The Function of a Cholinergic Synapse

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

43. 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

44. Figure 11.21 Neurotransmitter Functions
Figure 11.21a

45. Figure 11.21 Neurotransmitter Functions
Figure 11.21b

46. Figure 11.21 Neurotransmitter Functions
Figure 11.21c

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

48. 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

49. Figure 11.22 Temporal and Spatial Summation

50. Figure 11.23 EPSP – IPSP Interactions

51. 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

52. 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

53. 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.

54. 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.