Nervous system

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Nervous system

• Functions
• Receives relays information about activities
  within the body
• Monitors responds to internal external
  changes
• Types of Neurons
• Neuron (nerve cell)- functional unit of the
  nervous system
• Sensory-from body to brain (afferent)
• Motor-from brain to body (efferent)
• Interneurons-between motor and sensory neurons

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Neurons
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Parts of a neuron

• Dendrite-many
• Receives impulses from axons
• Axon-only 1
• Sends impulses out to dendrites
• Cell body- contains organelles
• between axon dendrites
• Myelin sheath- fatty coat that allows impulses to
  travel faster b/c they jump from node to node
• myelin is made in Schwann cells
• Nodes of Ranvier- spaces in myelin sheaths along
  axons
• Synapse-space between axon and dendrite where
  neurotransmitters carry message from cell to cell
• Neurotransmitters-chemicals that cross the
  synapse to continue the nerve impulse
• site of drug action on nervous system (dopamine,
  seratonin, adrenaline)

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Neurotransmitters at the synapse
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Nerve Impulse

• Neurons have an electric potential (voltage)
  across their cell membranes due to a difference
  in ion concentration (Na and K) outside and
  inside the cell
• The inside of the cell usually has a negative
  charge (polarized), which is called the resting
  potential
• The neuron stays this way until it is stimulated
  by an impulse
• When an impulse reaches a neuron, the cell
  membrane allows Na ions into the cell
• Now, the inside of the membrane is more positive
  than the outside (depolarized)
• As the impulse passes, K ions flow out of the
  cell the membrane becomes repolarized, which is
  called the action potential

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Nervous System 2 Main Branches
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Central Nervous System

• Brain-100 billion neurons!!!!!!!!!!!
• Meninges- connective tissue that protects the
  brain
• pia mater- inner layer of protective tissue
• dura mater- outer layer of protective tissue
• cerebrospinal fluid-protective fluid between the
  mater layers
• Cerebrum- grey matter
• 2 hemispheres
• corpus callosum -layer of cells between the two
  hemispheres that connect the cerebrum
• largest part of the brain
• controls conscious activity, intelligence
  judgement
• Cerebellum-coordinates balance muscle activity
• Cerebral cortex- convolutions of grey matter
• interprets sensory information coordinates
  motor responses

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The Brain
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More parts
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Central Nervous System cont

• Brain stem- connects brain and spinal cord
• Upper brain stem
• diencephalon-thalamus and hypothalamus (master
  gland)
• directs incoming impulses
• Lower brain stem
• midbrain-vision and hearing center
• pons- relay area between cerebrum and cerebellum
• medulla oblongata-center for heart and
  respiratory rate
• Spinal cord
• grey matter and white matter
• connects brain to body
• reflexes save time by only travelling to the
  spinal cord back to the body part (not all the
  way to the brain)

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Peripheral Nervous System

• Sensory-acquire information from environment
  take messages to CNS
• Motor- reactions to the sensory message sent to
  the body from the brain
• somatic-to skeletal muscles
• conscious control reflexes
• autonomic-to glands, smooth and cardiac muscle
• involuntary actions
• 1.parasympathetic-turn things off after fight or
  flight response
• 2. sympathetic-turn things on in fight or flight
  response

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Fight or Flight Response
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Senses

• Vision- locations functions of
• pupil, iris, cornea, lens, retina, optic nerve
• Hearing balance- locations functions of
• anvil, hammer, stirrup, eardrum, cochlea,
  eustachian tube, semicircular canal
• Smell Taste- locations and functions of
• taste buds, amygdala

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Parts of the Ear

• 1. External ear
• 2. Auditory canal
• 3. Tympanic membrane (eardrum)
• 4. Stirrup-Stapes
• 5. Oval window
• 6. Eustachian tube
• 7. Cochlea
• 8. Semicircular canals
• 9. Anvil-Incus
• 10. Hammer-Malleus

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Taste and Smell

• The sense of taste is closely related to the
  sense of smell
• This is why you cannot taste food well when your
  nose is stuffed!
• Most of the 10,000 taste buds are embedded
  between bumps on the tongue called papillae
• Your taste buds can perceive salty, sweet,
  bitter, sour

A Taste Bud
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Parts of the Eye

• 1. Cornea
• 2. Iris
• 3. Ligament
• 4. Sclera
• 5. Muscles
• 6. Optic nerve
• 7. Vitreous humor
• 8. Lens
• 9. Aqueous humor
• 10. Pupil
• 11. Retina

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Electromagnetic Spectrum