PHYSIOLOGY

1. PHYSIOLOGY Nervous System

3. Types of Neurons • Afferent • Sensory • Efferent • Motor • Interneurons also known as association neurons • Between neuron

6. Classes of Sensory Receptors also known as NeuronsMechano-receptors:  mechanical forces- stretching alters membrane permeability                 (1)   haircells*  (deflection = depolarization = AP's)                        ie. lateral line of fish(mechanoreceptor= neuromasts detect water movement, etc) (2)   stretch receptors of muscles(3)   equilibrium receptor of inner ear(4)   receptors of skin (touch, pain, cold, heat).Chemo-receptors:  chemicals sense solutes in solvents, taste, smellOsmo-receptors:  of hypothalamus which monitors blood osmotic pressurePhoto-receptors:  light - eye, eyespots, infrared receptors of snakes, etc.Thermo-receptors:  radiant (heat) energyPhono-receptors:  sound wavesElectro-receptors:  detect electric currents... electric eels, etc..Nociceptors:  pain receptors... naked dendrites of skin (epidermis)

7. Bipolar Neuron • Two processes • An axon and a dendrite • They extend in opposite directions • Used for sensory organs • Olfactory neurons • Retina

8. Unipolar Neurons • Presence of only a single axon, branching at the terminal end. • True unipolar neurons not found in adult human; common in human embryos and invertebrates

9. Neuroglial Cells of the CNS

10. Astrocytes • In the CNS only • Most abundant Neuroglial Cell • Formation of Synapses • Plays a role in making exchanges between capillaries and neurons • Helps to form the Blood Brain Barrier • The BBB protects the brain from intruders

11. Microglial Cells • Macrophage • Scavenges apoptotic cells • May go bad causing Alzheimer’s Disease • Excessive secretion of Interleukin-1 • Helps to maintain homeostasis in the brain

12. Ependymal Cells of the CNS

13. Ependymal Cells • Lines ventricles in the brain and the central cavity of the spinal cord • Cells have cilia • Used to circulate the cerebrospinal fluid

14. Oligodendrocyte Cells of the CNS

15. Oligodendrocyte • Oligodendrocytes • Production of myelin in the CNS • Can cover as many as 60 neurons with myelin

17. Schwann/Satellite Cells • Schwann Cells • Production of myelin in the PNS • Not able to cover one neuron, must use multiple Schwann Cells • Formation of the Nodes of Ranvier • Produces Neuronal Growth Factor • Satellite Cells • Function unknown

20. Myelin Sheath • Myelin • Insulates the axon for rapid conduction of action potentials • Nodes of Ranvier • Gray v. White matter in the brain • Multiple Sclerosis is an autoimmune disease

22. The afferent and efferent axons together form the • Central nervous system • Autonomic division of the nervous system • Somatic motor division of the nervous system • Peripheral nervous system • Visceral nervous system

23. The afferent and efferent axons together form the • Central nervous system • Autonomic division of the nervous system • Somatic motor division of the nervous system • Peripheral nervous system • Visceral nervous system

24. Autonomic neurons are further subdivided into the • Visceral and somatic divisions • Sympathetic and parasympathetic divisions • Central and peripheral divisions • Visceral and enteric divisions • Somatic and enteric divisions

25. Autonomic neurons are further subdivided into the • Visceral and somatic divisions • Sympathetic and parasympathetic divisions • Central and peripheral divisions • Visceral and enteric divisions • Somatic and enteric divisions

26. Processes or appendages that are part of neurons include • Axons • Dendrites • Neuroglia • A and B • A, B and C

27. Processes or appendages that are part of neurons include • Axons • Dendrites • Neuroglia • A and B • A, B and C

28. Functional categories of neurons include • Afferent neurons • Sensory neurons • Interneurons • Efferent neurons • All of these are included as functional categories of neurons

29. Functional categories of neurons include • Afferent neurons • Sensory neurons • Interneurons • Efferent neurons • All of these are included as functional categories of neurons

31. Neuron • Receptive Zone • Where the Graded Response occurs • Cell Body • Same information as a regular cell but no centrioles • Amitotic • Contains ligand regulated gates • Dendrites • Projections to help form synapses • Contains ligand regulated gates

33. Neuron • Conducting Zone • Axon Hillock • Begins action potentials • Accumulation of K+ ions • Contains voltage regulated gates for Na+/K+ • Axon • Propagation of action potentials • Contains voltage regulated gates for Na+/K+ • Anterograde vs. Retrograde and Polio

35. Secretory Zone • Terminal Boutons • Contains voltage regulated gates for Ca+2 • Contains vesicles filled with Neurotransmitter

37. Resting Membrane Potential • -70 mV • Membrane is said to be polarized • Voltage generated by ionic movement through the membrane • Creates a current • Current = Voltage/ Resistance • Current generates a Kinetic Energy • More Na+ on the outside of the cell • More K+ on the inside of the cell • Diffusion down their electrochemical gradient

38. Resting Membrane Potential • Maintained by the Na+/K+ATPase pumps • Will not allow the neuron to reach equilibrium across the membrane • Actively transports 3Na+ out of the cell and 2K+ into the cell

41. Graded Response • Short lived • Localized changes in membrane potential • Can depolarize or hyperpolarize the membrane • Dependent on IPSP or EPSP • The magnitude of the graded potential varies directly with the stimulus strength • The stronger stimulus causes greater voltage change and the current flows farther • The current dies out within a few millimeters of its origin • Graded response only signals over a very short distance

42. Graded Response • Ligand sensitive Na+ gates will open with a stimulus • Na+ diffuses into the cell down its electrochemical gradient • Depolarization of the membrane • K+ is repelled down the membrane towards the axon hillock • K+ can diffuse out of the cell because the plasma membrane is very “leaky”

43. Graded potentials • Produce an effect that increases with distance from the point of stimulation • Produce an effect that spreads actively across the entire membrane surface • May involve either depolarization or hyperpolarization • Are all-or-none • All of the above

44. Graded potentials • Produce an effect that increases with distance from the point of stimulation • Produce an effect that spreads actively across the entire membrane surface • May involve either depolarization or hyperpolarization • Are all-or-none • All of the above

45. Action Potentials • Begins at the axon hillock • Voltage regulated Na+ and K+ gates • Along with Na+/K+ATPase pumps along the entire membrane • All or nothing response

46. Action Potentials • Depolarization • -50mV due to the accumulation of K+ at the axon hillock triggers an action potential • At -50mV Na+ voltage regulated gates open • Na+ diffuses into the cell down its electrochemical gradient • Na+ repels K+ down the membrane • Positive Feedback “on” • The more positive the voltage, due to Na+ diffusing into the cell, the more Na+ gates open. This creates a more positive voltage and more Na+ gates open • Positive Feedback “off” • +30mV

49. Action Potential • Repolarization • At +30mV • All Na+ gates close quickly • All K+ gates open • K+ diffuses out of the cell down its electrochemical gradient • K+ gates close slowly at -70mV • K+ continues to diffuse out of the cell until it reaches -90mV • All K+ gates are closed