1. NERVOUS SYSTEM HONORS ANATOMY & PHYSIOLOGY

2. Tissue & Homeostasis Nervous Tissue & Homeostasis excitable characteristic of nervous tissue allows for generation of nerve impulses (action potentials) that provide communication & regulation of most body tissue. together with endocrine system: responsible for maintaining homeostasis

3. Differences in Nervous & Endocrine Control of Homeostasis NERVOUSENDOCRINE rapid responder action potentials slow, prolonged response releases hormones

4. Structures of the Nervous System total mass of 2 kg (~3% of total body mass) Skull Spinal Cord Spinal Nerves Cranial Nerves Ganglia Enteric Plexus Special Senses & other Sensory Receptors

5. Major Structures of the Nervous System

7. Functions of the Nervous System 3 basic functions: 1. Sensory 2. Integrative 3. Motor

8. Sensory Function sensory receptors detect internal & external stimuli sensory (afferent) neurons carry this sensory information to spinal cord & brain thru cranial & spinal nerves

9. Integrative Function integrate: process nervous system takes information from sensory neurons & processes that information, analyzes it, stores some of it & makes decisions for appropriate responses served by interneurons (connect 1 neuron to another neuron Perception : ◦ conscious awareness of sensory stimuli ◦ occurs in brain

10. Motor Function served by motor (efferent) neurons carry info from brain/spinal cord  effectors (muscle or gland) thru cranial or spinal nerves results in muscles contraction or gland secreting

11. Quick Quiz What terms are given to neurons that carry input  spinal cord & brain? What terms are given to neurons that carry output out of the brain & spinal cord?

12. Organization of the Nervous System

13. Histology of the Nerrvous System 2 cell types 1. Neurons 2. Neuroglia

14. Neurons nerve cells that possess electrical excitability : ◦ ability to respond to a stimulus & convert it into an action potential ◦ stimulus: any change in environment that is strong enough to initiate an action potential

15. Direction Action Potential Travels

16. Action Potential electrical signal that propagates along surface of neurolema (membrane) ◦ begins & travels due to movement of ions between interstitial fluid & inside of neuron thru specific ion channels ◦ once begun it travels rapidly @ constant strength

17. Parts of a Neuron

18. Parts of Neuron: Cell Body contains nucleus, cytoplasm, typical organelles, + Nissl bodies clusters of RER ◦ make materials for:  growth of neuron  regenerate damaged axons in PNS

19. Nerve Fiber general term for any neuronal process or extension that emerges from cell body most neurons have 2: 1. Dendrites 2. Axons

20. Dendrites “little trees” input portion of neuron usually, short, tapering, highly branched their cytoplasm contains Nissl bodies, mitochondria

21. Axon propagates action potentials  ◦ another neuron ◦ muscle fiber ◦ gland cell

22. Parts of an Axon joins cell body @ cone-shaped elevation: axon hillock part of axon closest to hillock = initial segment jct of axon hillock & initial segment where action potential arises so is called the trigger zone

24. Parts of an Axon axoplasm: cytoplasm of an axon axolemma: plasma membrane of axon axon collaterals: side branches along length of axon (most @ 90°) axon terminals: axon divides into many fine processes

25. Synapse site of communication between 2 neurons or between a neuron & effector cell synaptic end bulbs: tips of some axon terminals swell into bulb-shaped structures synaptic vesicles: store neurotransmitter ◦ many neurons have >1 neurotransmitter, each with different effects on postsynaptic cell

27. Axonal Transport 2 types: ◦ for moving materials from cell body  axon terminals 1. slow ◦ 1-5 mm/d ◦ replenishes new axoplasm to developing or regenerating axons 2. fast ◦ 200 – 400 mm/d ◦ moves materials to/from cell body  organelles or membranes needed in axon terminal

28. Types of Neurons Functional ClassificationStructural Classification Sensory Interneurons Motor use # processes extending from cell body 1. Multipolar neurons 2. Bipolar neurons 3. Unipolar neurons

29. Multipolar Neurons several dendrites with 1 axon includes most neurons in brain & spinal cord

30. Bipolar Neuron 1 main dendrite & 1 axon retina, inner ear, olfactory area of brain

31. Unipolar Neuron are sensory neurons that begin in embryo as bipolar during development axon & dendrite fuse then divide into 2 branches (both have characteristic structure & function of an axon) 1 branch ends with dendrites (out of CNS) 2 nd branch ends in axon terminal (in CNS) cell bodies of most found in ganglia

32. Unipolar Neuron

33. Purkinje Cells found in cerebellum

34. Pyramidal Cells in cerebral cortex of brain

35. Neuroglia (Glia) ~50% vol of CNS “glue” do not generate or propagate action potentials multiply & divide in mature nervous systems glioma : ◦ brain tumors derived from glial cells ◦ very malignant, grow rapidly

36. Glial Cells of the CNS 1. ASTROCYTES 2. OLIGODENDROCYTES 3. MICROGLIA 4. EPENDYMAL CELLS

37. Astrocytes star-shaped largest & most numerous of glial cells functions: 1. physically support neurons 2. assist in blood-brain-barrier (bbb) 3. in embryo: regulate growth, migration, &interconnections between neurons 4. help maintain appropriate chemical environment for propagation of action potentials

39. Oligodendrocytes “few trees” smaller & fewer branches than astrocytes Functions: 1. form & maintain myelin sheath on axons in CNS 2. 1 oligo. myelinates many axons

40. Microglia small cells with slender processes giving off many spine-like projections function: 1. phagocytes ◦ remove cellular debris made during normal development ◦ remove microbes & damaged nervous tissue

41. Ependymal Cells single layer of cuboidal to columnar cells ciliated & have microvilli function: 1. line ventricles of brain & central canal of spinal cord 2. produce, monitor, & assist in circulation of cerebrospinal fluid (CSF) 3. form bbb

43. Neuroglial Cells of the PNS Schwann cells Satellite cells

44. Schwann Cells functions: 1. myelinate axons in PNS ◦ 1 Schwann cell myelinates 1 axon 2. participate in axon regeneration

45. Satellite Cells flat cells that surround cell bodies of neurons in PNS ganglia functions: 1. structural support 2. regulate exchange of materials between neuronal cell bodies & interstitial fluid

46. Myelination myelin sheath: made up of multilayered lipid & protein (plasma membrane) covering function: 1. electrically insulates axon 2. increases speed of nerve impulses

47. Myelinated & Unmyelinated Axons

48. Nodes of Ranvier gaps in myelin sheath 1 Schwann cell wraps axon between nodes of Ranvier

49. Sheath of Schwann = Neurolemma

50. Myelin amount increases from birth to maturity infant‘s responses slower & less coordinated as older child or adult in part because myelination is a work in progress thru infancy

52. Demyelination loss of myelin sheath see in disorders: ◦ multiple sclerosis ◦ Tay-Sachs ◦ side effect of radiation therapy & chemotherapy

53. Gray Matter of the Nervous System contains: ◦ neuronal cell bodies ◦ dendrites ◦ unmyelinated axons ◦ axon terminals ◦ neuroglia

54. White Matter of the Nervous System composed of: ◦ myelinated axons