THE NERVOUS SYSTEM

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THE NERVOUS SYSTEM
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Divisions of the NS

• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)

Fig. 11.32
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Sensory vs. Motor Nerves

• SENSORY nerves
• Body ? CNS
• MOTOR nerves
• CNS ? Body

Fig. 10.2
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2 Different Types of Motor Nerves

• Somatic NS
• consciously controlled effectors

• Autonomic NS
• involuntary effectors

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Cells of the Nervous System

• NEUROGLIAL CELLS

• NEURONS vs.

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NEUROGLIAL CELLS

• Fill spaces
• Provide structure
• Produce myelin
• Phagocytize bacteria cellular debris
• Outnumber neurons
• Can divide (mitosis)

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Neuron Anatomy Overview

• Dendrites ? Cell body ? Axon ? Synaptic knobs at
  axon terminals ? Effector

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Neuron Anatomy

• Schwann cells
• type of neuroglial cell
• myelin sheath
• Nodes of Ranvier

Fig. 10.3
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Classification of Neurons

• THE DIRECTION

• THEIR SHAPE

Fig. 10.6
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Sensory, Motor, and Interneurons (Direction)

• Sensory neurons
• PNS ? CNS
• Motor neurons
• CNS ? PNS
• Interneurons
• in between sensory
• and motor neurons

Fig. 10.7
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Shapes of Neurons
Fig. 10.6
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Neuron vs. a Nerve

• Neuron a cell
• Nerve bundles of neuron axons, and neuroglial
  cells bound together
• outside brain/spinal cord

Fig. 11.24
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Neuron Physiology

• Sending neuron impulses action potential
• change in electrical charge in cell membrane
• depends on electrolytes
• potassium (K) and sodium (Na)

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First Things First Creating a Resting Potential

• Protein pumps
• open and close
• let ions through
• Active pumps
• against a gradient
• Passive pumps
• with the gradient

Fig. 10.13
Na/K Pump
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Resting Potential
Fig. 10.14
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Action Potential
Fig. 10.15
Action Potential
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A Nerve Impulse- a series of action potentials
Fig. 10.16
Computer activity http//outreach.mcb.harvard.edu/
animations/actionpotential.swf
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Action Potential
Fig. 10.18
Action Potential Zoomed Out
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What happens when the nerve impulse reaches the
end of the axon?

• axon terminals
• next to another neuron (as shown) or a muscle or
  gland
• Gap called a synapse
• Synapse

Fig. 10.11
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The Synapse

• Neurotransmitters
• Synaptic cleft
• Receptors
• Send a message

Fig. 10.12
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Neurotransmitters
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Classification of Neurotransmitters

• EXCITATORY depolarize the next neuron
• It tells the next neuron/muscle/gland to GO

• INHIBITORY hyperpolarize the next neuron
• prevent the nerve impulse from continuing
• It tells the next neuron/muscle/gland to STOP

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Acetylcholine (ACH)

• First neurotransmitter discovered (1921)
• Mostly excitatory
• Skeletal muscle neuromuscular junctions
  synapses between the brain and spinal cord
• Message
• muscles contract or
• continue sending impulses

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Acetylcholine cont.

• Nicotine
• Activates acetylcholine receptors
• Releases dopamine (coming later)
• Alzheimers
• Memory loss, depression, disorientation,
  dementia, hallucinations,death
• Deficient acetylcholine

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Glutamate

• Generally excitatory
• helps send messages in the brain
• Involved in learning and memory
• Alcohol inhibits glutamate receptor function

• Monosodium Glutamate (MSG)
• food additive
• stimulates glutamate receptors in the taste buds

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Serotonin

• Antidepressants (Prozac, Zoloft, Paxil, etc)
• SSRIs or Selective Serotonin Reuptake
  Inhibitors
• Serotonin accumulates in the synapse
• feel more content
• LSD blocks serotonin
• MDMA releases excess serotonin

• Found in the brain
• Primarily inhibitory
• Sleep, mood and temperature regulation
• Insomnia deficient serotonin

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Dopamine

• AKA the brain reward
• Regulates emotions, moods and subconscious
  control of skeletal muscle
• Nicotine
• excess dopamine release
• Cocaine
• blocks reuptake (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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GABA

• Found in the brain
• Generally inhibitory
• Prevents the receptor nerve from being
  overstimulated
• When it accumulates it has a sedative effect

• Valium, Xanax and Ativan work by allowing GABA to
  accumulate
• Huntingtons Disease deficient GABA

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Norepinephrine

• Found in the brain
• Alertness, regulation of moods
• Ritalin Adderall- increase level of norepi and
  dopamine
• Strattera- increase only norepi
• Clinical depression low norepi

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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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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

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Peripheral Nervous System

• 12 pairs cranial nerves

• 31 pairs spinal nerves

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PNS Flow Chart

• Peripheral Nervous System
• Motor Sensory
• nerves nerves
• Somatic Autonomic
• nerves nerves
• Sympathetic Parasympathetic
• nerves
  nerves

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PNS cont.

• Motor nerves are divided into
• Somatic n.s.- conscious activities
• Autonomic n.s. unconscious activities
• Autonomic n.s is divided into
• sympathetic and
• parasympathetic divisions.

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PNS cont.

• SYMPATHETIC
• fight or flight responses
• speeds up heart rate, breathing and other
  functions vital to survival
• Digestion and other less essential functions will
  be slowed for awhile.

• PARASYMPATHETIC
• when the body is not mobilized and active in
  fight or flight.
• speeds up digestion and other essential functions
  
• When the body is in this mode, heart rate and
  breathing are calm.

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The Central Nervous System

• The Brain

• The Spinal Cord

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Central Nervous System - Spinal Cord
Figs11.5, 11.6, 11.7
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Reflexes
Fig. 11.8
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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

Fig. 11.15
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The Cerebrum

• Divided into right and left cerebral hemispheres
• Covered by folds called convolutions/gyri 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

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The Cerebrum cont.

• The cerebral cortex is divided into LOBES which
  control various functions
• FPOT

Fig. 11.16 11.17
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The Cerebrum cont.

• FRONTAL LOBE
• Primary Motor Area
• controls voluntary muscles
• Brocas Area
• motor speech
• usually L hemisphere
• Voluntary eye movement
• Concentration, planning, problem solving, analysis

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The Cerebrum cont.

• PARIETAL LOBE
• Sensory info touch, taste, pressure, pain
• interpretation of sensory info, awareness of
  body
• Wernickes Area
• sensory speech, understanding written spoken
  language
• usually L hemisphere

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The Cerebrum cont.

• OCCIPITAL LOBE
• visual senses
• analyzing visual patterns, combining visual
  images with other info (i.e. recognizing a
  person)
• TEMPORAL LOBE
• sensory smell and hearing
• interpretation of sensory experiences
  (understanding speech, reading)

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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
• Corpus callosum

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The Cerebellum

• Integrates sensory info
• Balance, coordination of skeletal muscle, posture

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Brainstem

• Brainstem Connects the cerebrum to the spinal
  cord
• Midbrain visual and auditory reflex center
• Pons transfer nerve impulses
• Medulla Oblongata
• Cardiac center- heart rate
• Vasomotor center- smooth muscle in blood
  vessels/blood pressure
• Respiratory center- breathing rate
• Coughing, sneezing, swallowing and vomiting
  reflexes

Fig. 11.21
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Diencephalon

• Thalamus-
• - Receives all sensory impulses (except smell)
  and relays them to the appropriate region of the
  cerebral cortex
• 2. Hypothalamus
• Maintain homeostasis
• Links the nervous system to the endocrine system
• 3. Pituitary pineal glands

Fig. 11.19
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Diencephalon cont.

• The limbic system is a collection of structures
  involved in emotional behavior and your feelings
• Includes the amygdala and hippocampus

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MEMORY

• Primarily occurs in the cerebrum and the
  hippocampus (in the diencephalon)
• 3 main types of memory
• Sensory memory lasts momentarily and involves
  input from senses
• Short term memory lasts from a few seconds or
  minutes to hours (varies)

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Memory cont.

• 3. Long term memory the neurons actually change
  shape (dendrites extend, more are made, etc) and
  connect with other neurons. Lasts days to years
  (varies).