1. Nervous System Marieb 11.1

2. 29-2 Classification Anatomically  CNS  Brain  Spinal cord  PNS  Peripheral nerves Functionally Somatic nervous system (SNS) Skeletal or voluntary muscles Autonomic nervous system (ANS) Automatic functions

3. Nervous system Computer  Sensory receptors and nerves  Effectors and motor nerves  Spinal cord  Brain and spinal cord  Control mechanisms in lower brain  Input circuit  Output circuit  Simple computers (output directly controlled by input)  Complex computers (input and previous memory)  CPU (sequence of information processing)

4. 29-4 CNS: Brain and Spinal Cord

5. PNS: Cranial Nerves (12) Marieb 13.5a

6. PNS: Spinal Nerves (31) Marieb 13.6  Spinal cord : Slender structure continuous with the brain  Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra  31 spinal segments:  8 cervical segments  12 thoracic segments  5 lumbar segments  5 sacral segments  1 coccygeal segment

7. Martini 13-11

8. Comparison of Somatic and Autonomic Systems Marieb 14.2

9. Freeman 45-20

10. Meninges Marieb 12.24a

11. 29-11 CNS: Brain  Four sections and three levels  Cerebrum (higher brain):Thoughts and memory  Diencephalons (subcortical or lower brain):subconcious activities like arterial pressure, emotions, feeding reflexes  Brain stem (lower and mid brain): respiration, visual and auditory reflexes  Cerebellum (lower brain) :Coordination in movement

12. Space Restriction and Brain Development Marieb 12.3

13. 29-13 CNS: Brain – Cerebrum  Largest section  Two cerebral hemispheres  Connected by a thick bundle of nerve fibers called the corpus callosum  Longitudinal fissure between hemispheres  Sulci – grooves on surface  Gyri or convolutions – bumps of brain matter between sulci

14. Marieb 12.6ab

17. 29-17 Previous slide

18. 29-18  Cortex  Outer layer – gray matter  Contains about 75% of all neurons  Inner layer – white matter  Functions  Interpret sensory information  Initiate body movements  Stores memories and creates emotions  Ventricles  Interconnected cavities within the brain  Filled with CSF CNS: Brain – Cerebrum (cont.)

19. Ventricles of the Brain Marieb 12.5

20. Diencephalon: Thalamus and Hypothalamus Marieb 12.12

21. 29-21  Between the cerebral hemispheres superior to the brain stem  Thalamus  Relay station for sensory information going to the cerebral cortex for interpretation  Hypothalamus  Maintains homeostasis by regulating vital activities CNS: Brain – Diencephalon

22. 29-22  Connects the cerebrum to the spinal cord  Midbrain (mesencephalon, amygdala) Just beneath diencephalon Controls both visual and auditory reflexes, eg.feeding reflexes  Pons Rounded bulge on underside of brain stem Between midbrain and medulla oblongata Regulates respiration  Medulla oblongata  Inferior portion of brain stem  Directly connected to spinal cord  Controls many vital activities, such as heart rate, blood pressure, and breathing CNS: Brain – Brain Stem

23. 29-23  Location  Inferior to the occipital lobes of the cerebrum  Posterior to the pons and medulla oblongata  Coordinates  Complex skeletal muscle contractions that are needed for body movements  Fine movements Brain CNS: Brain – Cerebellum

24. 29-24  Lobes  Frontal  Motor areas for voluntary body movements  Parietal  Somatosensory – interprets sensations  Temporal  Auditory – interprets sounds  Occipital  Interprets what a person sees Frontal Parietal Occipital Temporal CNS: Brain – Cerebrum (cont.)

25. Spinal Cord Marieb 12.29a

26. Gray Matter and Spinal Roots Marieb 12.31b

27. Cross-Sectional Anatomy of the Spinal Cord  Anterior median fissure – separates anterior funiculi  Posterior median sulcus – divides posterior funiculi Marieb 12.31a

28. Gray Matter: Organization Marieb 12.32

29. 18_26_nerve_lymphoc.jpg Alberts 18-26

30. Marieb 11.4

31. 29-31 Neuron Structure (cont.)  White matter – axons with myelin sheath  Schwann cells – neurological cells  Wrap around some axons  Cell membranes contain myelin  Myelin insulates axons and enables axons to send nerve impulses more quickly  Gray matter – axons without myelin sheath Schwann cells Axon Dendrites

32. Marieb 11.3

34. Myelin Sheath and Neurilemma: Formation Marieb 11.5abc

35. Freeman 45-12a

36. Comparison of Structural Classes of Neurons Marieb T11.1.1

37. Martini 12-4

38. Saltatory Conduction Marieb 11.16

39. Dendrites Cell body Nucleus Axon hillock Axon Signal direction Synapse Myelin sheath Axon terminals Presynaptic cell Postsynaptic cell Campbell 48.5

40. Structure of a Nerve Marieb 13.3b

41. 29-41 Nerve Impulse  Impulse travels down axon to synaptic knob  Vesicles or small sacs in synaptic knob  Produce chemicals called neurotransmitters  Neurotransmitters are released by synaptic knob  Allow impulse transmission to postsynaptic structures  Dendrites  Cell bodies  Axons of other neurons

42. 29-42 Nerve Impulse  Functions of neurotransmitters  Cause muscles to contract or relax  Cause glands to secrete products  Activate or inhibit neurons

43. 29-43 Nerve Impulse  Membrane potential  Neuron cell membrane at rest is in a polarized state  Inside of cell membrane is negative (-90 mV)  Outside of cell membrane is positive due to more Na + and K +  As Na + and K + move into the cell, the membrane becomes depolarized  Inside becomes more positive (+ 45 mV)  Action potential (nerve impulse) is created  Repolarization occurs when K + and later Na + move to the outside of the cell membrane  Return of the cell to polarized (resting) state

44. Synaptic Cleft: Information Transfer Marieb 11.18

45. Type of Synapses  Chemical, Electrical  In electrical synapses, ionic current spreads directly from one cell to another through tubular structures called connexons. A cluster of 100 or so connexons forms a pathway (connection) called a GAP JUNCTION between adjacent cells. Gap junctions are common between cardiac muscle cells (shown below, left) and between smooth muscle cells  Excitatory, inhibitory  GABA, glycine- inhibitory, to lower anxiety  Acetyl choline, serotonin, glutamine- Excitatory  Epenepherin, Norepinepherin, dopamine are both excitatory and inhibitory

46. Postsynaptic neuron Synaptic terminals of presynaptic neurons 5 µm Campbell 48.16

47. Freeman 45-17a

48. CSF  Cerebrospinal fluid (CSF) is a clear, colorless body fluid found in the brain and spine. It is produced in the choroid plexuses of the ventricles of the brain. It acts as a cushion or buffer for the brain's cortex, providing basic mechanical and immunological protection to the brain inside the skull. The CSF also serves a vital function in cerebral autoregulation of cerebral blood flow.  The CSF occupies the subarachnoid space (between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It constitutes the content of the ventricles, cisterns, and sulci of the brain, as well as the central canal of the spinal cord.

50. The CSF has two major pumps that help to establish healthy flow. The pump at the top of the spine is the occiput bone which makes up the lower portion of the skull. Flexion and extension motions of the occipital bone upon the atlas help to pump CSF through the brain and spinal cord The other pump is at the bottom of the spine in the sacrum. Flexion and extension of the sacrum is also critical to help pump the CSF

52. 1. Lateral ventricle 2. Interventricular foramen 3. Third ventricle 4. Cerebral aqueduct 5. Fourth ventricle 6a. Median aperture6b. Lateral aperture6c. Central canal (spinal cord) 7. Subarachnoid space 8. Arachnoid villi 9. Dural sinuses Marieb 12.26b

54. Composition  CSF composition is similar to serum composition, besides protein, calcium and protein concentrations which are lower  CSF is normally as clear as water and does not contain any blood cell (leukocytes, aka white blood cells and erythrocytes, aka red blood cells).  However, in infections such as meningitis, leukocytes may pass into the CSF and after hemorrhage, red blood cells may be found in CSF.  Protein concentration in the CSF, usually very low, is increased in case of infection and if CSF reabsorption at the level of the arachnoïd villi is impaired.  In a reverse way, glucose concentration is decreased in some pathological conditions (tumor, acute bacterial infection, fungal infections...)

55. SubstanceCerebrospinal FluidSerum Water Content (%)9993 Protein (mg/dL)357000 Glucose (mg/dL)6090 Osmolarity (mOsm/L) 295 SodiumSodium (mEq/L)138 PotassiumPotassium (mEq/L)2.84.5 CalciumCalcium (mEq/L)2.14.8 MagnesiumMagnesium (mEq/ L) 0.31.7 ChlorideChloride (mEq/L)119102 pH7.337.41 Comparison of Average Serum and Cerebrospinal Fluid [7] [7]

56. Function of CSF  Buoyancy: The actual mass of the human brain is about 1400 grams; however, the net weight of the brain suspended in the CSF is equivalent to a mass of 25 grams. [18] The brain therefore exists in neutral buoyancy, which allows the brain to maintain itsdensity without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF. [19]masshuman brainweight [18]neutral buoyancydensityneurons [19]  Protection: CSF protects the brain tissue from injury when jolted or hit. In certain situations such as auto accidents or sportsinjuries, the CSF cannot protect the brain from forced contact with the skull case, causing hemorrhaging, brain damage, and sometimes death.auto accidentssportsskullhemorrhagingbrain damage  Chemical stability: CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood–brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness andsyncope.[19]

57. Blood Brain Barrier  Because the brain is so specialized many of the chemicals found in the blood are actually toxic to the neurons in the brain. With such a specialized job one would think that the brain itself should actually have its own separate circulatory system.  Unlike other parts of the body where the arteries and veins and capillaries bring nutrients to cells and move waste out of cells, the neurons in the brain are created with specialized capillaries made of protein fibers called “astrocytes”. These specialized capillaries essentially filter out harmful toxins and only allow through to the specialized brain cells healthy nutrients the brain needs.  Alcohol too passes the Blood Brain Barrier as easily as water and that can be very bad for brain tissue. Prescription drugs however, because they are mostly synthetic have great difficulty in passing through this Blood Brain Barrier. The body recognizes the synthetic material as foreign and won’t let it pass through.

59. C) Myelination process D) Unmelinated neuron