Anatomy & Physiology I Unit Seven

1. Anatomy & Physiology I Unit Seven

2. Nervous System Function The general purpose of the nervous system is to coordinate the function of all body cells and maintain homeostasis using electrical and chemical means

3. Nervous System Function Integrating Center Sensor Effectors Stimulus Response

4. Anatomy of the Human Nervous System

5. Anatomy of the Human Nervous System

6. Anatomy of the Human Nervous System Neuron – a nerve cell Nerve – a bundle of neuron axons wrapped in fibrous connective tissue Ganglion – a mass of neuron cell bodies found in the PNS

7. Anatomy of the Human Nervous System

8. Neuron Properties and Classes Neuron properties: ~ excitability – respond to stimuli ~ conductivity – sending electrical impulses ~ secretion – release of neurotransmitters

9. Neuron Properties and Classes Neuron classes: ~ afferent (sensory) neurons * detect a variety of stimuli and send messages to the CNS

10. Neuron Properties and Classes Neuron classes: ~ interneurons * found only in the CNS * receive signals from afferent neurons * carry out integrative functions * approximately 90% of all neurons

11. Neuron Properties and Classes Neuron classes: ~ efferent (motor) neurons * send messages from CNS to effectors (muscles or glands) in response to stimuli

12. Neuron Properties and Classes

13. Neuron Structure

14. Neuron Structure

15. Neuron Structure

16. Neuroglia Neuroglia - support cells that aid in the functions of neurons > four types are found in the CNS * astrocytes * oligodendrocytes * microglia * ependymal cells

17. Neuroglia

18. Neuroglia Neuroglia - support cells that aid in the functions of neurons > two types are found in the PNS * Schwann cells * satellite cells

19. Action Potentials • Resting membrane potential: • + polarization of neuron due to • differences in external & internal • ion concentrations • + typical RMP is -70mV (more • anions on the inside than outside)

20. Action Potentials

21. Action Potentials Action potential: + a nerve (electrical) impulse + generated by chemically mediated channels + propagated by charge mediated channels

22. Action Potentials

23. Action Potentials

24. Action Potentials

25. Action Potential Propagation

26. Refractory Period and Action Potential Conduction

27. Action Potential Propagation Saltatory conduction

28. Action Potential Generation

29. The Neural Synapse A synapse is junction at the end of a neuron axon where it stimulates another cell by way of chemical messengers called neurotransmitters

30. The Neural Synapse The most common synapse types are: ~ neural synapse – junction between one neuron and another ~ myoneural synapse – junction between a neuron and a muscle cell

31. The Neural Synapse

32. The Neural Synapse Presynaptic membrane Synaptic cleft Postsynaptic membrane

33. The Neural Synapse Neurotransmitters are chemical messengers that are released by an axon presynaptic membrane Some neurotransmitters will excite postsynaptic membranes while others will inhibit them

34. Neurotransmitters Neurotransmitter classes: + acetylcholine + amino acids + monoamines + neuropeptides

35. Neurotransmitters Acetylcholine: + released in myoneural synapses & in most ANS synapses + excites skeletal muscle + inhibits cardiac muscle + excites & inhibits smooth muscle and glands depending on location

36. Neurotransmitters Amino acids: + four types that excite or inhibit activity in the CNS + excitatory – glutamate & aspartate + inhibitory – glycine & GABA (gamma aminobutyric acid)

37. Neurotransmitters Amino acids: + glutamate is the principle excitatory neurotransmitter of the brain, while aspartate is the principle one in the spinal cord

38. Neurotransmitters Amino acids: + GABA is the most common inhibitory neurotransmitter in the brain, while glycine is the most common in the spinal cord

39. Neurotransmitters Monoamines: + found mainly in the brain, but also in the spinal cord and ANS + can exhibit excitatory or inhibitory effects depending on location

40. Neurotransmitters Monoamines: + catecholamines are a group of commonly known monoamines ~ norepinephrine is found in the brain, spinal cord & ANS causing excitation & inhibition

41. Neurotransmitters Monoamines: + catecholamines are a group of commonly known monoamines ~ epinephrine is found in the brain & spinal cord causing excitation & inhibition

42. Neurotransmitters Monoamines: + serotonin is found in the CNS and is secreted by platelets + its effects are usually excitatory

43. Neurotransmitters Monoamines: + histamine is found in the brain and is secreted by basophils + its effects are as a potent vasodilator

44. Neurotransmitters Neuropeptides: + found mainly in the CNS, but also in the digestive tract + they are mainly inhibitory in nature, playing major roles in pain suppression and digestion

45. Neurotransmitters Neuropeptides: + beta endorphin suppresses pain and fatigue + cholecystokinin (CCK) suppresses appetite and aids in digestion

46. The Neural Synapse Cholinergic receptors

47. The Neural Synapse Adrenergic receptors

48. Postsynaptic Response As has been noted, postsynaptic responses can be excitatory or inhibitory Neurotransmitters that elicit an excitatory response do so by producing excitatory postsynaptic potentials (EPSPs)

49. Postsynaptic Response Neurotransmitters that elicit an inhibitory response do so by producing inhibitory postsynaptic potentials (IPSPs) Both EPSPs and IPSPs are necessary for proper function in the nervous system

50. Postsynaptic Response