The Brain

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

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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

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The Brain

• Ventricles

http//www.cerebromente.org.br/n02/fundamentos/ven
triculos_i.htm
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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

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http//www.mscd.edu/biology/2320course/2320images
/Willis.gif
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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
• gt4 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

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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

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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.

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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

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http//www.mhhe.com/socscience/intro/ibank/ibank/0
012lll.jpg
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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

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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

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

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The Cerebrum
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
cerebrum_1.gif
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Corpus Callosum
http//www.disenchanted.com/dis/lookup.html?node1
852
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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

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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

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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

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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
• Parkinsons Disease
• Stroke in this area results in total paralysis of
  opposite side of the body.

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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

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The Limbic System
http//www.mhhe.com/socscience/intro/ibank/ibank/0
014lll.jpg
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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

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

• Neurotransmitters
• Acetylcholine Usually excitatory, skeletal
  neuromuscular junctions
• Dopamine Emotional responses, subconscious
  movements of skeletal muscles
• Parkinsons Disease
• Norepinephrine Neuromuscular and neuroglandular
  junctions
• Related to arousal, dreaming, and mood

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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

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The Brain

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

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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

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Cranial Nerves
http//info.med.yale.edu/caim/cnerves/cn1/cn1_1.ht
ml