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The Brain

The Brain. Poudre High School By: Ben Kirk. The Brain. General: Part of the Central Nervous System Large, mushroom shaped organ Approximately 3 lbs. In adults 4 major components Cerebrum, Cerebellum, Diencephalon, Brain Stem. The Brain.

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The Brain

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  1. The Brain Poudre High School By: Ben Kirk

  2. The Brain • General: • Part of the Central Nervous System • Large, mushroom shaped organ • Approximately 3 lbs. In adults • 4 major components • Cerebrum, Cerebellum, Diencephalon, Brain Stem

  3. The Brain • Cerebrospinal Fluid (CSF): Circulates throughout the subarachnoid space surrounding the spinal cord and brain, and within the ventricles of the brain • Ventricles: cavities within the brain that communicate with one another • 2 lateral ventricles • 1, 3rd ventricle • 1 4th ventricle • 80-150 ml CSF • Produce about 500 ml CSF per day (Total replacement of CSF every 8 hours) • Made of glucose, urea, proteins, and salt • Functions as a shock absorber and circulatory medium • Nutrients, waste, chemical messengers

  4. The Brain • Ventricles http://www.cerebromente.org.br/n02/fundamentos/ventriculos_i.htm

  5. The Brain • Blood Supply: • The brain is a highly active organ, thus needing extensive vascularization (O2 and nutrients) • Arterial Blood: Delivered via internal carotids and vertebral arteries • Circle of Willis • Venous Return: Delivered via internal jugular veins

  6. http://www.mscd.edu/~biology/2320course/2320images/Willis.gifhttp://www.mscd.edu/~biology/2320course/2320images/Willis.gif

  7. The Brain • Blood Supply: • Interruptions: • Brief blockage or interruption = faint • Karate chop to neck: Internal carotids • Blow to jaw: Vertebral and brain stem • 1-2 minute blockage = weakened cells • >4 minutes of blockage = Permanent damage to cells due to lysosomal enzyme attack • Cerebrovascular accident (CVS)/Stroke: Neurons die in localized areas • Only specific functions impaired • Neurons in CNS cannot regenerate • Localized takeover by neighboring neurons

  8. The Brain • Blood-Brain Barrier (BBB): • Regulates what can and cannot enter cerebral circulation • Made of tightly packed endothelial cells lining the capillaries of the CNS • Can enter: CO2, O2, ammonia, lipids (steroids, alcohols) • Cannot enter: antibiotics, H20, Ions

  9. The Brain • Parts of the Brain • Brain Stem: Lower extension of the brain where it connects to the spinal cord • Medulla Oblongata: Continuation of the spinal cord that contains ALL ascending and descending tracts • White matter only (myelinated axons) • All communication between brain and spinal cord passes through the Medulla Oblongata • Both pyramidal tracts cross over in the Medulla • Decussation of pyramids: one side of brain controls the other side of the body • Severe blow to jaw twists this region of the brain stem resulting in knockout • Contains nuclei that control rate and force of heartbeat and breathing rhythm.

  10. The Brain • Brain Stem: • Pons: Structure just above the medulla • Consists of nuclei and white matter • Connects spinal cord to brain and brain parts together • Helps regulate breathing, consciousness and sleep • Midbrain: Between the Pons and the lower portion of the diencephalon • Contains motor fibers connecting the cerebral cortex to the spinal cord • Regulates most occulomotor responses (eye movement, pupil dilation, responses to sight), hearing and body movement

  11. http://www.mhhe.com/socscience/intro/ibank/ibank/0012lll.jpg

  12. The Brain • Diencephalon: • Integrates conscious and unconscious sensory information and motor commands • Thalamus (Gray Matter): Relay station for all ascending sensory information. • Interprets impulses such as pain, heat, pressure and light touch • Hypothalamus: Contains homeostatic mechanisms primarily • Autonomic Nervous System: (heart rate, gastrovascular movement, bladder contractions • Body Temperature • Rage and Aggression • Food intake/hunger • Thirst center • Consciousness and Sleep patterns

  13. The Brain • Reticular Activating System (RAS): Center of arousal and activation • Cardiac Rhythm: 24 hour sleep and wake patterns • Consciousness results from RAS activation • Sleep results from RAS inactivation • Feedback causes increased activation and arousal • Altered by cocaine, alcohol. Anesthetics, meditation, and amphetamines • Faulty RAS • ADHD: Increased RAS activation, leads to abnormal stimulation • Coma: semi permanent sleep caused by faulty or injured RAS

  14. Reticular Activating System http://www.colorado.edu/epob/epob3730rlynch/image/figure5-29.jpg

  15. The Brain • Cerebrum: Bulk of the Brain • Cerebral Cortex: Thin layer of gray matter making up the outer covering of the cerebrum • 6 layers of cell bodies • Development: The brain increases in size, with gray matter increasing in size faster than white matter • Causes folds (fissures) to form • Longitudinal Fissure: Separates right an left hemispheres • Corpus Callosum: White matter that connects the right and left hemispheres • Larger in females

  16. The Cerebrum http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif

  17. Corpus Callosum http://www.disenchanted.com/dis/lookup.html?node=1852

  18. The Brain • Cerebrum: • Lobes: • Each hemisphere has 4 lobes divided by sulci (shallow) or fissures (deep) • Frontal, parietal, occipital, and temporal • Functions: • Frontal (primary Motor Cortex): Voluntary control of skeletal muscles • Parietal (primary Sensory Cortex): Conscious perception of pain, temperature, taste, pressure, and vibration • Occipital (Visual Cortex): Conscious perception of visual stimuli • Temporal (Auditory and Olfactory Cortex): Conscious perception of auditory and olfactory (smell) stimuli

  19. The Brain • Cerebrum: • Also has a function in memory • Brain Lateralization: • Left handed: parietal and occipital lobes of right hemispheres are narrower and frontal lobe of left hemisphere is narrower. • Left hemisphere: right handed control, written and spoken language, numerical and scientific skills, and reasoning • Right Hemisphere: Random, intuition, subjectivity, synthesizing, and artistic

  20. The Brain • Cerebrum: • White Matter: Myelinated Axons – 3 types • Association Fibers: Transmit impulses between gyri (bumps or elevated areas) of the same hemisphere • Commissural Fibers: Communicate one side of the brain with the other (corpus callosum) • Projection Fibers: Transmit impulses from cerebrum to other parts of the brain

  21. The Brain • Cerebrum: • Basal Ganglia: Paired masses of gray matter within the white matter of each hemisphere • Controls subconscious movement (ex. Swinging of arms while walking) • Does not initiate movement, but provides pattern for repeated movements (walking, chewing, etc..) • If damaged, uncontrolled shaking results • Parkinson’s Disease • Stroke in this area results in total paralysis of opposite side of the body.

  22. The Brain • Limbic System • Wishbone shaped group of structures encircling the brain stem (between the cerebrum and the diencephalon • Controls emotions of pain, pressure, anger, rage, fear, sorrow, sexual feelings and affection

  23. The Limbic System http://www.mhhe.com/socscience/intro/ibank/ibank/0014lll.jpg

  24. The Brain • Cerebellum: • 2nd largest part of the brain • Behind the medulla and pons, and bellow the occipital lobes • Cortex (outer covering) consists of gray matter • White matter resembles tree branches • Controls subconscious skeletal muscle movements • Balance, posture, coordination • Ataxia: lack of coordination

  25. The Cerebellum http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif

  26. The Brain • Neurotransmitters: • Acetylcholine: Usually excitatory, skeletal neuromuscular junctions • Dopamine: Emotional responses, subconscious movements of skeletal muscles • Parkinson’s Disease • Norepinephrine: Neuromuscular and neuroglandular junctions • Related to arousal, dreaming, and mood

  27. The Brain • Neurotransmitters: • Serotonin: Inhibitory, induces sleep, sensory reception, temperature regulation and mood • Gamma Aminobuteric Acid: Inhibitory, Target of anti-anxiety drugs like Valium • Substance P: Associated with pain • Stimulates perception of pain • Opposite of Endorphins • Eukephalins: Suppresses substance P

  28. The Brain • Neurotransmitters: • Endorphins: Inhibits substance P • Also have a role in memory, learning, and sexual activity • Have been linked to depression and schizophrenia

  29. The Brain • Cranial Nerves • 12 pairs of nerves • 10 pair originating from the brain stem • Designated by roman numerals. • Part of the Somatic Nervous System • Some are sensory only, while others are mixed

  30. Cranial Nerves http://info.med.yale.edu/caim/cnerves/cn1/cn1_1.html

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