The Central Nervous System: Part 3 –CSF, BBB, CVA

1. 12 The CentralNervous System:Part 3 –CSF, BBB, CVA

2. Brain Video • Neurotransmitters – Noradrenalin, serotonin, dopamine and endorphins

3. Cerebrospinal Fluid (CSF) • Composition • Watery solution formed from blood plasma • Less protein and different ion concentrations than plasma • Constant volume MDufilho

4. Cerebrospinal Fluid (CSF) • Functions • Gives buoyancy to CNS structures • Reduces weight by 97% • Protects CNS from blows and other trauma • Nourishes brain and carries chemical signals MDufilho

5. Choroid Plexuses • Hang from roof of each ventricle; produce CSF at constant rate; keep in motion • Clusters of capillaries enclosed by pia mater and layer of ependymal cells • Ependymal cells use ion pumps to control composition of CSF and help cleanse CSF by removing wastes • Normal volume ~ 150 ml; replaced every 8 hours MDufilho

6. Figure 12.24b Formation, location, and circulation of CSF. Ependymal cells Capillary Section of choroid plexus Connective tissue of pia mater Wastes and unnecessary solutes absorbed CSF forms as a filtrate containing glucose, oxygen, vitamins, and ions (Na+, Cl–, Mg2+, etc.) Cavity of ventricle CSF formation by choroid plexuses MDufilho

7. Figure 12.24a Formation, location, and circulation of CSF. Slide 1 4 Superior sagittal sinus Arachnoid villus Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle 1 The choroid plexus of each Ventricle produces CSF. 2 Median aperture 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Central canal of spinal cord 3 CSF flows through the subarachnoid space. (a) CSF circulation 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. MDufilho

8. Figure 12.25 Hydrocephalus in a newborn. MDufilho

9. Blood Brain Barrier • Helps maintain stable environment for brain • Separates neurons from some bloodborne substances • Composition • Continuous endothelium of capillary walls • Thick basal lamina around capillaries • Feet of astrocytes • Provide signal to endothelium for formation of tight junctions MDufilho

10. Figure 11.3a Neuroglia. Capillary Neuron Astrocyte Astrocytes are the most abundant CNS neuroglia. MDufilho

11. Blood Brain Barrier: Functions • Selective barrier • Allows nutrients to move by facilitated diffusion • Metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, K+ denied • Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics • Absent in some areas, e.g., vomiting center and hypothalamus, where necessary to monitor chemical composition of blood MDufilho

12. Homeostatic Imbalances of the Brain • Traumatic brain injuries • Concussion—temporary alteration in function • Contusion—permanent damage • Subdural or subarachnoidhemorrhage—may force brain stem through foramen magnum, resulting in death • Cerebral edema—swelling of brain associated with traumatic head injury MDufilho

13. Blood Flow to the Brain • Brain requires more blood flow and oxygen • Receives 15 – 20% of body’s blood flow • Uses 15 – 20% of body’s oxygen Mickey Dufilho

14. Figure 19.22b Arteries of the head, neck, and brain. Ophthalmic artery Branches of the external carotid artery Basilar artery Vertebral artery • Superficial temporal artery • Maxillary artery • Occipital artery • Facial artery • Lingual artery • Superior thyroid artery Internal carotid artery External carotid artery Common carotid artery Thyrocervical trunk Larynx Costocervical trunk Thyroid gland (overlying trachea) Subclavian artery Clavicle (cut) Brachiocephalic trunk Axillary artery Internal thoracic artery (b) Arteries of the head and neck, right aspect

15. Figure 19.22d Arteries of the head, neck, and brain. Anterior Cerebral arterial circle (circle of Willis) Frontal lobe Optic chiasma • Anterior communicating artery Middle cerebral artery • Anterior cerebral artery Internal carotid artery • Posterior communicating artery Mammillary body • Posterior cerebral artery Basilar artery Temporal lobe Vertebral artery Pons Occipital lobe Cerebellum Posterior (d) Major arteries serving the brain (inferior view, right side of cerebellum and part of right temporal lobe removed)

16. Figure 19.22c Arteries of the head, neck, and brain.

17. Homeostatic Imbalances of the Brain • Cerebrovascular accidents (CVAs or strokes) • Ischemia • Tissue deprived of blood supply; brain tissue dies, e.g., blockage of cerebral artery by blood clot • Hypoxia • condition in which inadequate oxygen is available to tissues • Hemiplegia (paralysis on one side), or sensory and speech deficits • Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia • Tissue plasminogen activator (TPA) is only approved treatment for stroke MDufilho

18. Homeostatic Imbalances of the Brain • Degenerative brain disorders • Alzheimer's disease (AD): a progressive degenerative disease of brain that results in dementia • Memory loss, short attention span, disorientation, eventual language loss, irritable, moody, confused, hallucinations • Plaques of beta-amyloid peptide form in brain • Toxic effects may involve prion proteins • Neurofibrillary tangles inside neurons kill them • Brain shrinks MDufilho

19. Homeostatic Imbalances of the Brain • Parkinson's disease • Degeneration of dopamine-releasing neurons of substantia nigra • Basal nuclei deprived of dopamine become overactive  tremors at rest • Cause unknown • Mitochondrial abnormalities or protein degradation pathways? • Treatment with L-dopa; deep brain stimulation; gene therapy; research into stem cell transplants promising MDufilho

20. Homeostatic Imbalances of the Brain • Huntington's disease • Fatal hereditary disorder • Caused by accumulation of protein huntingtin • Leads to degeneration of basal nuclei and cerebral cortex • Initial symptoms wild, jerky "flapping" movements • Later marked mental deterioration • Treated with drugs that block dopamine effects • Stem cell implant research promising MDufilho

21. Brain Video • Shows effects of stroke and repair • Formation of new synapses Mickey Dufilho

22. Physiology of Addiction • Definition • Psychological or Physiological? • Kinds of addictions? MDufilho

23. Day in the Life of Nicotine Junkie • 1 st Cigarette/chew of the day • Nicotine = ACh • Stimulates release of hormones Epi and NE • Lasts 30 min • 2nd, 3rd, 4th cig/chew • Stimulates release of hormone cortisol • Then NT dopamine and glutamate • Lasts 30 min MDufilho

24. Why is Nicotine Addictive? • ↓ ACh • ↑ # Nicotinic of Receptors • So what? MDufilho

25. Physiology of Depression • Definition • Psychological or Physiological? • Causes? • Environmental and neurotransmitters MDufilho

26. Physiology of Depression • ↓ in NE and/or Serotonin • Due to????? • Treatment – dual approaches • MAO Inhibitors (monoamine oxidase) • Tricyclic antidepressants • SSRI (serotonin specific reuptake inhibitors) MDufilho

27. What about anxiety? • What system creates anxiety? • Treatment • Valium (diazepam), Ativan (lorazepan), Xanax • Rohypnol – date rape drug is in the same family of drugs as Valium, Ativan • Barbiturates (penobarbital) bind to GABA receptor – opens chloride channels which cause hyperpolarization MDufilho