The Nervous System

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The Nervous System

• Anatomy

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Nervous System

• Master controlling and communicating system of
  the body

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Structural Divisions of NC

• Central- Brain, spinal cord
• Peripheral- Cranial nerves, spinal nerves
• Sensory- senses
• Motor Division- motor nerves

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Structural Divisions of NC

• Autonomic- involuntary
• Somatic- voluntary
• Sympathetic- responds to emergencies (flight or
  fight)
• Parasympathetic- promotes non-emergency functions

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Central and Peripheral NS
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Neuron Structure
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Neurons

• Cell Body- major center of the neuron
• Neurofibrils- bundles of filaments (maintain
  shape)
• Dendrite- receptive region
• Axon- impulse generating/conducting region)

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Neurons

• Schwann Cell- one node that conducts signal to
  terminal
• Neurilemma- surrounds schwann
• Axon terminals- secretes neurotransmitters
• Myelin sheath- protects/contains electrical
  impulses nerve

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Structural Classification

• Multipolar neurons
• Bipolar neurons
• Unipolar neurons

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Functional Classifications

• Sensory/afferent neurons- transmits from sense
  receptors to CNS
• Motor/efferent neurons- carry impulses away from
  CNS
• Interneurons- between motor and sensory

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Membrane Channels

• When gated ion channels are open, ions diffuse
  across membrane following their electrochemical
  gradientcreates an electrical gradient

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Resting Membrane Potential

• Exists only across a membrane that is neutral
  (the channels being closed)
• Na and Cl- is outside the cell
• K and A- (protein) is inside the cell

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Graded Potential

• Short lived
• Local changes in membrane
• Triggered by neurons environment

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Action Potential

• The principal way neurons communicate is through
  an action potential
• Brief reversal of membrane potential

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Action Potential

• Also called nerve impulse
• Only axons can generate one!
• 1. neuron gets stimulated
• 2. stimulus changes membrane (channels open)

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Phases of Action Potential and Roll of Gated Ion
Channels
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Classify Neurons Functionally

• Sensory (afferent neurons)
• Afferent pathway to CNS
• Motor (efferent) neurons
• CNS to effector
• Interneurons (association)
• Message within CNS

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Synapse

• Junction that mediates information transfer from
  one neuron to the next
• Neuron conducting impulse toward synapse is
  presynaptic neuron
• Neuron transmitting signal away from synapse is
  postsynpatic neuron

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Synapse

• Electrical- less common, ion flow creates and
  electrical impulse
• Chemical- release chemical neurotransmitters
• 1. Ca released from presynpatic cell
• 2. Neurotransmitter released
• 3. Neurotransmitters bind to postsynaptic cell
• 4. Repeat

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Neurotransmitters

• Acetylcholine (ACh)-stimulates skeletal muscles,
  leads to muscle spasms, decreased levels in
  Alzheimers patients, may account for behavioral
  effects of nicotine addicts

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Neurotransmitters

• Dopamine- feeling good chemical, deficient in
  Parkinsons disease, may be involved in
  schizophrenia

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Neurotransmitters

• Norepinephrine- feeling good chemical, reduced
  levels lead to depression

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Neurotransmitters

• Serotonin- may be a roll in sleep, appetite,
  migraine headaches, regulation of mood, drugs
  that inhibit this relieve anxiety and depression

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Neurotransmitters

• Histamine- vasodilator, released during
  inflammation of cells
• Glutamate- important in learning and memory,
  stroke chemical (excessive release causes death
  of neurons)

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Reflex Arch

• Pathway that controls an action reflex

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Diencrphalon

• Centeal core of forebrain
• Thalamus, hypothalmus, epithalalmus

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Thalamus

• Memory processing
• Relay station for messages

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Hypothalamus

• Integration system of involuntary actions
• Body temperature
• Food intake
• Water imbalance
• Biological rhythms
• Hormones

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Epithalamus

• Mediates emotional response
• Memory processing

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Cerebral Hemispheres

• Left and Right
• Interprets sensory input
• Controls voluntary and skilled muscle activity
• Intelligence and emotions

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Lobes of Brain
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Brain Stem

• Produce behaviors necessary for survival, filters
  out repetitive stimuli, alertness, help with
  muscle movements
• Contains midbrain, pons, medulla,

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Brain Stem

• Midbrain- visual, auditory
• Pons- relay information between brain,
  respiratory rate and depth
• Medulla- sensory impulses, heart rate, blood
  vessel diameter, vomiting, coughing, relay system

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Cerebellum

• Process information
• Provides instructions for other cerebral areas
• Balance, posture
• Smooth muscle movements

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EEG

• Electroencephalogram
• Records electrical activity of brain
• Patterns are brain waves
• Each of us have a unique brain wave pattern
• Like our fingerprints

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Brain Waves

• Alpha waves- occur when calm, relaxed
• Beta waves- occur when mentally alert
• Theta waves- abnormal in adults
• Delta waves- occur in deep sleep, if occur in
  awake adults ? indicate brain damage

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Consciousness

• Conscious perception of sensations, voluntary
  initiation, movement, processing (memory, logic,
  judgment, perseverance)

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Stages of Memory

• Memory- storage and retrieval of information
• Long term and short term
• Long- limitless capacity
• Short- working memory, 7-8 chunks of info.

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Stages of Memory

• Moving short term memory to long term
• 1. Emotional state
• 2. Rehearsal (enhances memory)
• 3. Association (tying new information to old)
• 4. Automatic (not all impressions are consciously
  formeddont remember lecture but remember outfit)

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Meninges

• Three tissue membrane
• Dura mater, Pia mater, Exhnoid mater)
• Cover and protect CNS
• Blood vessels
• Cerebrospinal fluid

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Cerebrospinal Fluid

• Liquid cushion
• Protection
• Nourishment

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Blood-Brain Barrier

• Protective mechanism that helps maintain stable
  environment
• Selective
• Structure is not uniform

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Gross Anatomy-Spinal Cord
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Microscopic Anatomy- Spinal Cord
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CVA

• Strokes
• Blood is blocked to brain and brain tissue dies
  (blood clot)
• Usually paralyzed on one side
• Fewer than 35 will live after 3 yrs

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Alzheimers

• Progressive, degenerative disease
• Results in dementia
• Memory loss, disorientation, confusion,
  hallucinations

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Peripheral NS

• Links from the world outside to our bodies

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Nerve Regeneration

• Mature neurons do not divide
• If cell body remains intact they can regenerate

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12 Cranial Nerves

• Olfactory- smell
• Optic- vision
• Oculomotor- motor nerves to eye (direct eyeball,
  iris, pupil)
• Trochlear- nerves of eye muscles

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12 Cranial Nerves

• Trigeminal- sensory of scalp, eyelid, nose,
  cornea, tongue, chin
• Abducens- muscles of eye
• Facial- nerves of face and mandible
• Vestibulocohlear- senses for balance, ear

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12 Cranial Nerves

• Glossopharyngeal- tongue, swallowing
• Vagus- pharynx and larynx, heart rate, lungs,
  spleen, liver, gallbadder, somtach, kidney,
  intestines
• Accessory- palate, pharynx, larynx
• Hypoglossal- food mixing and manipulation, tongue
  movements for speech

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Nerve Plexuses

• Nerve plexuses- interlacing nerve networks
• Occur in cervical, brachial, lumbar, and sacral
  regions

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Major Nerves
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Autonomic NS

• Internal environment
• Smooth and cardiac muscle
• 2 divisions (parasympathatic and sympathetic)

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Parasympathetic

• Resting and digesting system
• Keeps body energy low

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Sympathetic

• Fight or flight response
• Dilated eyes, pounding heart rate, sweat, heavy
  breathing

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Spina Bifida

• Backbone and spinal canal dont close before
  birth

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Cerebral Palsy

• Damage to motor control centers of the brain
• Can occur during pregnancy, childbirth or after
  birth up to about age three.
• Limits in movement
• Disturbances of sensation, depth perception,
  communication impairments in cognition, epilepsy

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Smell Receptors

• Olfactory receptor cells
• Olfactory cilia- site of molecular reception
• Olfactory nerve- cranial nerve 1 (smell)

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Taste Receptors

• Taste buds
• Fungiform papillae- bumps on tongue (contain
  taste buds)

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Eye

• Conjuctiva- lines eyelids, lubricates eye
• Lacrimal apparatus-
• Lens- contains area of tears and drainage
• Aqueous humor- nutrition, pressure, immune
  response

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Eye

• Iris- controls light levels into the eye
• Cornea- refracts light, clear, covers iris/pupil
• Ciliary body- produces aqueous humor
• Retina- light sensitive, forms image,

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Eye

• Sclera- white outer wall of eye
• Optic nerve
• Optic disc- where nerve cells exit the eye to
  form optic nerve

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Glaucoma

• Damage to optic nerve (from pressure in eye) lead
  to nerve damage and blindness

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Hyperopia

• Farsightedness
• Can see distance perfectly
• Eyeball too short

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Myopia

• Can see close up perfectly
• Eyeball is too long

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Astigmatism

• Unequal curvature in different parts of the lens
• Lead to blurry images

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Color Blindness

• Due to a lack of one or more cone types
• Sex-linked condition

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Ear

• Pinna- outer ear
• Meatus- tube running from outer ear to inner ear
• Cerumen- ear wax, protection
• Tympanic membrane- transmits sound from the air

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Ear

• Oval window- intersection of inner and middle
  ear, noise amplified 20 times here
• Cochlear window- sound vibrations transmitted
  here
• Eustachian tube- drains mucus, equalizes pressure
• Malleus- hammer, transmits sounds vibrations

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Ear

• Incus- transmits sound, only in mammals
• Stapes- smallest/lightest, transmits
• Cochlea- pressure, responds to electrical stimuli
  (brain, nerves)
• Cochlear nerve
• Semicircular canals- fluid, helps with spatial
  orientation, balance

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Sound

• Hair cells in ear are activated by sound waves of
  different frequencies
• As intensity of sound increase the membranes
  vibrate more
• Nerves help us localize sound source

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