1. Nervous System Academic Anatomy & Physiology

2. The Function To act as the master controlling and communicating system for the body Subdivided into CNS & PNS http://www.agen.ufl.edu/~c hyn/age2062/lect/lect_20/n ervsys.gif

3. Cells of the Nervous System 1. Neuroglia Acts to support neurons Makes up ~ 90% of brain and spinal cord (s.c.) There are 5 different types of neuroglial cells

4. Types of Neuroglia A. Astrocytes B. Oligodendrocytes C. Microglial cell D. Ependymal Cells E. Schwann Cells

5. Assignment Using page 225 in your text, draw the different types of neuroglia and list their location and function within the nervous system below each drawing DO NOT draw Schwann cells but do list its location and function

6. Cells of the Nervous System 2. Neurons The conducting nerve cell Senses changes in environment, integrates information, carries out motor responses Structure: each neuron varies in shape and size, but all have 3 main parts (dendrite, axon and cell body)

7. Neuron

8. Neuron Anatomy A. Dendrite: a process off of the cell body; receives impulses from adjacent neurons & conducts electrical impulses TOWARD the cell body; ~1000/neuron

9. Neuron Anatomy B. Axon: aka nerve fiber; acts to transmit impulses AWAY from the cell body; 1 axon/neuron C. Cell Body: contains the nucleus and metabolic center of the cell

10. Neuron Anatomy D. Myelin sheath: made by schwann cells in PNS and oligodendrocytes in CNS; encloses the axon & speeds up the rate of nervous conduction i. Gray matter: non-myelinated nerve fiber ii. White matter: myelinated nerve fiber

11. Neuron Anatomy E. Nodes of Ranvier: gaps in myelin sheath @ regular intervals; aids in increasing speed of nervous conduction

12. 3 Types of Neurons 1. Afferent (sensory) Neurons: transmit impulses from PNS to CNS i.e. pain receptors and proprioceptors 2. Efferent (motor) Neurons: transmit impulses from CNS to muscles or glands

13. Motor Neuron

14. 3 Types of Neurons 3. Interneurons (association neurons): located within CNS and conducts impulses between sensory and motor neurons

15. Nerve Conduction: Distribution of Ions More Na + on outside than inside a neuron More K + on inside than outside + negatively charged particles K + ions permeate through lipid bi-layer more easily than Na + ions do

16. Nerve Conduction: Resting Potential Describes a polarized, resting nerve K + and Na + follow laws of diffusion Na + /K + pump maintains the unequal distribution of these ions across membrane Cell uses energy to keep Na + out and K + in despite natural diffusion Inside of cell is more negative than outside

18. Nerve Conduction: Depolarization An activated nerve cell; has been stimulated Na + specific channels in the membrane open and Na + floods into the cell The charge on the inside of the cell is now LESS negative (more positive)

19. Nerve Conduction: Repolarization Returning to a resting state K + specific channels in the membrane open and K + floods the outside of the cell This returns the inside of the cell to a MORE negative (less positive) state Depolarization + Repolarization of a nerve cell = An Action Potential

20. Impulse Conduction A wave of bioelectric action potentials travels the length of a neuron, stimulating adjacent neurons as it goes Unmyelinated neurons slower than myelinated Impulses on myelinated neurons seem to jump from one node of Ranvier to the next

21. The Synapse An action potential is electrical across the neuron and chemical once it reaches the synaptic cleft Presynaptic Neurons Have synaptic knobs sensitive to Ca + When Ca + is present allow synaptic vesicles within them to release neurotransmitters

22. The Synapse Neurotransmitters cross the synaptic cleft and bind to postsynaptic neurons Excitatory Neurotransmitters: triggers action potential to continue in postsynaptic neuron Inhibitory Neurotransmitters: lessens the chance of a continuing neurotransmitter

23. Impaired Conduction The following block nervous impulses by reducing the membrane permeability to sodium ions Alcohol Sedatives Anesthetics Cold and pressure (slows, does not impair)

24. Structural Classifications of Nervous System Central Nervous System (CNS) Includes brain and spinal cord Acts as integrating and command center Peripheral Nervous System (PNS) Includes nerves outside of CNS Spinal nerves Cranial nerves Links all parts of body by carrying impulses

25. Subdivisions of PNS 1.) Somatic system: voluntary nervous system Contains sensory and motor nerves Makes you aware of the world around you & allows you conscious control

26. Subdivisions of PNS 2.) Autonomic System: involuntary nervous system Consists of motor nerves that carry impulses to organs, blood vessels and glands The unconscious or “automatic control”

27. Subdivisions of Autonomic System A. Sympathetic division Active during stress heart rate, respiratory rate and rate of ATP breakdown B. Parasympa- thetic Division Active during conditions of normal organ functioning These 2 divisions often work antagonistically to one another

28. CNS: The Brain 4 major portions: Cerebrum: largest; sensory & motor function, higher thought, memory & reasoning Cerebellum: coordination of skeletal muscles Diencephalon: sensory information Brain stem: connects parts of nervous system; controls visceral activities

30. CNS: Cerebrum Cerebral Hemispheres Cerebral Cortex Corpus Callosum Gyri Sulci Fissures

32. CNS: Cerebral Lobes Frontal Lobe: anterior portion Primary motor area Concentration, planning, problem solving Broca’s Area: motor speech Temporal Lobe: lateral lobe Interpretation of sensory impulses, memory, visual & auditory patterns Auditory area Olfactory area

34. CNS: Cerebral Lobes Parietal Lobe: superior, lateral lobe Sensory area Understanding speech; using words Occipital Lobe: posterior lobe Vision Combining visual images; visual recognition

35. CNS: Hemisphere Dominance Equal participation in receiving and analyzing sensory information, controlling skeletal muscles and storing memory Dominant Hemisphere: ability to understand language 90% of people dominant left side Nondominant Hemisphere: nonverbal functions, orientation in space, musical patterns, nonverbal visual experiences

36. CNS: Cerebellum Located inferior to occipital lobes and posterior to brain stem Functions in: positioning of limbs, coordinating skeletal movements, maintanance of posture

37. CNS: Diencephalon Located between cerebral hemispheres; superior to midbrain Thalamus: central relay center for sensory impulses; allows awareness of pain, touch & temperature Hypothalamus: regulates visceral activities; links nervous and endocrine systems Also holds: optic chiasma, posterior pituitary gland, pineal gland, infundibulum

39. CNS: Brainstem Connects cerebrum to spinal cord Midbrain: b/n diencephalon and pons Visual, auditory reflex centers; head movement for hearing Pons: rounded bulge b/n midbrain and medulla Relays sensory impulses; helps regulate breathing

40. CNS: Brainstem Medulla Oblongata: from pons to spinal cord Cardiac center, vasomotor center, respiratory center

41. CNS: Spinal Cord A continuation of the brain running from base of brain to 1 st or 2 nd lumbar vertebrae Is enclosed within spinal column Is ~ size of thumb except at enlarged cervical and lumbar plexuses (spinal nerve distribution to upper and lower limbs)

42. CNS: Spinal Cord Provides a 2-way pathway to and from the brain Serves as a reflex center Has 31 linear segments giving way to 31 spinal nerves (relay info. from PNS to CNS and vice versa) Cauda Equina: collection of spinal nerves at the inferior end of the vertebral column

44. Spinal Cord in Column http://www.latrobe.edu.au/podiatry/Images/1%20Biomech%20pics/SPINALMECHpics/Spinal%20cord%20diag.GIF

45. Spinal Cord Cross Section http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/CNS_Histology/ Spinal_Cord/sp_cd_jpgs/Spinal_Cord_PC271478md.JPG

46. Spinal Cord Cross-Section Gray Matter: unmyelinated Located in center of cord forming an “H”: divided into horns Each horn runs a different fiber tract Posterior Horn: sensory neurons Anterior Horn: motor neurons Lateral Horn: motor neurons in autonomic system

47. Spinal Cord Cross-Section White Matter: myelinated fibers Surrounds central gray matter Divided into anterior, posterior and lateral columns Each column holds longitudinal nerve tracts Ascending tracts: carry sensory info to brain Descending tracts: carry motor info. away from brain

48. Reflex Center Reflex: an extremely rapid response to an emergency situation Occurs in spinal cord or lower brain; does not require thinking The Reflex Arc: Receptor: at end of sensory neuron; can generate an action potential to CNS Association neurons: receive info. from sensory neuron and routes response to motor neuron Motor neurons: conduct impulses to effectors

49. Reflex Arc

50. Protections of CNS Bone: skull and vertebral column Cerebrospinal Fluid (CSF): Made from the blood Forms a watery cushion that protects tissue from trauma Changes in composition indicates brain pathology

51. Protections of CNS Meninges: connective tissue membranes A. Dura mater: tough outer covering of brain and s.c. B. Arachnoid mater: middle layer C. Pia mater: inner surface which clings tightly to surface of brain and s.c. Subarachnoid space: separates the arachnoid and pia maters; filled with CSF

53. Protections of CNS Blood-Brain Barrier Composed of least permeable capillaries in body Brain depends on a very constant internal environment Allows: water, glucose, and essential amino acids Disallows: urea, protein and most drugs Cannot block: fats, respiratory gases and fat soluble molecules (alcohol, nicotine and anesthetics)