Nervous System

1. Nervous System • What allows you to perceive the world around you, to recognize the incoming stimuli and to react to the environment • Sensory systems • Motor systems • Memory/learning

2. Nervous System • Central Nervous System (CNS) • Brain and Spinal Cord • Peripheral Nervous System (PNS) • All nervous tissue outside the CNS • Somatic Nervous System (SNS)---voluntary • Sensory and motor neurons to skeletal muscle • Autonomic Nervous System (ANS)---Involuntary • Sensory and motor neurons to viscera • Sympathetic Division (increase heart rate) • Parasympathetic Division (decrease heart rate)

3. Nervous System Neurons (=nerve cells) general characteristics: - can be very long---6 feet or more - conduct nervous impulses---communication - long lived---entire life span - high metabolic rate; high O2 and glucose needs---brain accounts for less than 10% of body mass, yet gets over 25% of body’s energy

4. Types of Neurons (functional classification) • Motor Neurons--- • carry info from brain to body • Sensory Neurons--- • carry info from body to brain • Interneurons--- • carry info within the Central Nervous System (CNS). These account for 90% of the neurons in the body • Neuroglia---support cells • Oligodendrocytes---CNS • Schwann cells---PNS

5. Types of Neurons (structural classification) • Multipolar---many processes located in CNS • Bipolar---2 processes located in sensory organs (eye, ear & nose) • Unipolar--1 process these are sensory neurons. The axon and dendrite fuse into one process. • Interneurons---Named based on looks or after the person who first described them (fig. 12.5) • Purkinje cells, Pyramidal cells

7. Anatomy of a `typical’ motor neuron nucleus

8. Anatomy of a `typical’ motor neuron nucleus cell body = soma = perikaryon

9. Anatomy of a `typical’ motor neuron nucleus Nissl bodies = rough endoplamic reticulum cell body = soma = perikaryon

10. Anatomy of a `typical’ motor neuron nucleus Nissl bodies cell body = soma = perikaryon Golgi apparatus

11. Anatomy of a `typical’ motor neuron other organelles: mitochondria lysosomes neurofilaments nucleus Nissl bodies cell body = soma = perikaryon Golgi apparatus

12. Anatomy of a `typical’ motor neuron neural processes: axon = nerve fiber dendrites

13. Anatomy of a `typical’ motor neuron Flow of Information: axon dendrites

14. Anatomy of a `typical’ motor neuron axon hillock (trigger zone) axon dendrites

15. Anatomy of a `typical’ motor neuron terminal branches= telodendria axon hillock axon dendrites

16. Anatomy of a `typical’ motor neuron terminal branches axon hillock axon axonal terminals = synaptic knobs = synaptic boutons dendrites

17. Anatomy of a `typical’ motor neuron terminal branches axon hillock axon axonal terminals = synaptic knobs = synaptic boutons dendrites

18. Anatomy of a `typical’ motor neuron axonal terminals = synaptic knobs = synaptic boutons

19. Anatomy of a `typical’ motor neuron synaptic vesicles with neurotransmitters

20. Anatomy of a `typical’ motor neuron

21. Anatomy of a `typical’ motor neuron

22. Anatomy of a `typical’ motor neuron

23. Anatomy of a `typical’ motor neuron

24. Anatomy of a `typical’ motor neuron

25. Anatomy of a `typical’ motor neuron

26. Anatomy of a `typical’ motor neuron

27. Anatomy of a `typical’ motor neuron

28. Anatomy of a `typical’ motor neuron

29. Anatomy of a `typical’ motor neuron

30. Anatomy of a `typical’ motor neuron

31. Anatomy of a `typical’ motor neuron

32. Myelin Sheath • Some Axons are myelinated • Myelin Sheath (schwann cell in PNS and oligodendrocyte in CNS) axon • Multiple layers wrapped around = myelin • Cell body and cytoplasm (outer most layer) = Neurolemma

33. Anatomy of a `typical’ motor neuron myelination:

34. Anatomy of a `typical’ motor neuron myelination: Special Glial cells -- make up the myelin sheath

35. Anatomy of a ‘typical’ motor neuron Myelin

36. Anatomy of a `typical’ motor neuron nodes of Ranvier

37. Resting Membrane Potential • Voltage across the membrane • Electric potential energy • Due to separation of ions • All cells have a resting membrane potential

38. - + + + + - - + + - - - Resting Membrane Potential - + + + + - - + + - - -

39. Resting Membrane Potential + - + - - + - - - + + +

40. Amplifier Electrode 0 mV Oscilloscope Resting Membrane Potential

41. Amplifier Electrode -70 mV Oscilloscope Resting Membrane Potential

42. Resting Membrane Key Players • Sodium-Potassium (Na+/K+) Pump • Moves Sodium and Potassium against their concentration gradients • Moves 3 Na+ out of the cell and 2 K+ into the cell

43. Resting Membrane Potential Key Players: Na+/ K+ Pump: 3 Na+ out Cell exterior cell membrane ATP Cell interior 2 K+ in

44. Resting Membrane Potential Key Players: Leaky Channels Na+ K+ Cell exterior cell membrane K+ Cell interior Na+ • Many K+ “leak” channels • Few Na+ “leak” channels

45. ATP ATP _ + _ + _ + ATP _ + _ _ + _ _ + + + K+ 2 K+ K+ K+ 2 K+ Pumps 3 Na+ Leak Channels K+ 2 K+ K+ K+ 3 Na+ Na+ Together creates -70 mV Resting Membrane Potential 3 Na+ 2 K+ Na+ Leak Channels Na+

46. Resting Membrane Potential • Voltage across the membrane • Electric potential energy • Due to separation of ions • All cells have a resting membrane potential

47. Electrical Signaling Through Changes in Membrane Potential • Describing Changes in Membrane Potential • Graded Potentials • Action Potentials • Propagation of Action Potentials

48. 0 mV -70 mV -90 mV 0 mV -70 mV -90 mV Two Types of Change: • Depolarizing • reduce membrane potential • make inside less negative • Na+ move into cell • Hyperpolarizing • increase membrane potential • make inside more negative • K+ move out of cell

49. Signals produced by a change in membrane potential • Graded potentials • Short lived • Local Signaling • Either depolarizing or hyperpolarizing

50. Graded Potentials • typical of dendrites and cell body (NOT axons) • are the first step in neuronal communication • are essential in initiating action potentials