The Nervous System

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The Nervous System

• Part II-The Brain

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I. Central Nervous System The Brain

• Cerebrum
• Largest part
• Sensory motor functions
• Higher mental functions (memory, reasoning, etc)
• Brainstem
• Connects the cerebrum to the spinal cord
• Cerebellum
• Coordinates voluntary muscle movements
• Diencephalon
• Processes sensory info

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A. The Cerebrum

• Divided into right and left cerebral hemispheres
• Covered by folds called convolutions and grooves
  called sulci (little groves) and fissures (big
  grooves)
• Connected by the corpus callosum
• It has a cortex an outer covering about 2 mm
  thick
• Gray matter vs. white matter
• The cerebral cortex is divided into LOBES which
  control various functions

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• 1. Frontal Lobe (Brain 1 handout)
• Control of voluntary muscles in the body
• Motor speech (Brocas area)
• Voluntary eye movement
• Concentration, planning, problem solving
• Rational thought, intelligence

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• 2. Parietal Lobe
• touch, taste and other sensory info
• understanding speech, using words (Wernickes)
• 3. Temporal Lobe
• smell and hearing
• interpretation of sensory experiences
• 4. Occipital Lobe
• visual senses
• 5. Motor Area (frontal)
• movement of skeletal muscles

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• 6. Pre-Motor Area (frontal)
• learned motor skills
• 7. Motor Speech Area (Brocas) (frontal)
• controls mouth movement for speech
• 8. Sensory Area (frontal/parietal)
• conscious awareness of sensations
• interpretation of sensory experiences
• 9. Auditory Area (temporal)
• Hearing is processed
• 10. Visual Area (occipital)
• Processes input from optic nerves

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Cerebral Hemispheres

• Hemisphere half of sphere (brain)
• The right side of the brain controls the left
  side of the body and vice versa
• Hemispheres connected by the Corpus callosum

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(use Brain 2 handout)B. The Cerebellum (14)

• Processes sensory information about limbs,
  joints, and other body parts to determine desired
  positions.
• Balance, coordination of skeletal muscle, posture

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C. Brainstem

• Brainstem Connects the cerebrum to the spinal
  cord
• Midbrain visual and auditory reflex center
• Pons(12) transfers nerve impulses from cerebrum
  to cerebellum
• Medulla Oblongata (13) controls heart and
  breathing rates, controls blood pressure, vessel
  changes

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D. Diencephalon

• Thalamus-(7)
• Receives all sensory impulses and relays them to
  the appropriate region of the cerebral cortex
• Produces awareness of sensation
• Hypothalamus (8)
• Links the nervous system to the endocrine system
• Regulates heart rate, blood pressure, body temp,
  hunger, gland secretions, sleep etc.
• Maintains homeostasis-links nervous to endocrine
  system

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• The limbic system is a collection of structures
  involved in emotional behavior and your feelings
• Includes the thalamus, hypothalamus, amygdala and
  hippocampus
• Fear, anger, pleasure, sorrow
• Olfaction travels through the limbic system so
  scent is related to feelings.

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II. Neurotransmitters

• Excitatory neurotransmitters
• 1. Increase postsynaptic membrane permeability
  to Na
• 2. Threshold is reached for message to be sent
• B. Inhibitory neurotransmitters
• 1. Decrease permeability to Na
• 2. Decreases chance nerve impulse will occur.

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Types of Neurotransmitters
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A. Acetylcholine (ACH)

• First neurotransmitter discovered (1921)
• Excitatory
• Used for skeletal muscle contraction at
  neuromuscular junctions synapses between the
  brain and spinal cord
• Message causes muscles to contract or continues
  impulses
• Nicotine inactivates ACH receptors and causes
  brain to create more receptors

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B. Serotonin

• Found in the brain
• Sleep, mood and temperature regulation
• Antidepressants (Prozac, Zoloft, Paxil, etc) work
  by allowing serotonin to accumulate in the
  synapse,
• SSRIs or Selective Serotonin Reuptake
  Inhibitors
• feel more content
• LSD mimics serotonin, and MDMA (aka ecstasy)
  releases excess serotonin

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C. Dopamine

• AKA the brain reward
• Regulates emotions, moods and subconscious
  control of skeletal muscle
• Cocaine
• interferes with the process by which dopamine is
  taken back up (leaves more in the synapse)
• Methamphetamine
• excess dopamine release

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Dopamine - contd

• Dopamine also sends signals that help coordinate
  your skeletal muscle movements
• Parkinsons Disease
• deficient dopamine production
• tremors

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D. Endorphins

• Flood the synaptic cleft during pain or stress
• Usually inhibit neurons from firing, causing an
  analgesic effect
• At lower levels can excite the next neuron
• Reduces pain and makes one feel good
• Opiates (heroin, codeine, morphine, oxycodone,
  hydrocodone, etc)
• bind to endorphin receptors and mimic endorphins

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E. Anandamide

• Involved in working memory, regulation of feeding
  behavior, generation of motivation and pleasure
• Anandamide receptors are called cannabinoid
  receptors
• A lot of cannabinoid receptors in the hippocampus
  (short term memory), cerebellum (coordination)
  and basal ganglia (unconcious muscle movement) of
  brain
• THC (found in marijuana) mimics anandamides and
  binds to cannabinoid receptors