Neuro A

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Neuro AP Review
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Nervous System

• CNS
• Brain
• Spinal cord
• PNS
• Cranial Nerves
• Spinal Nerves
• Afferent (sensory) pathways
• Efferent (effector/motor) pathways

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Peripheral Nervous System

• Functionally
• Somatic system
• Autonomic system
• Sympathetic
• Parasympathetic

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Nervous Tissue

• Neuron
• Supporting Cells
• Astrocytes (multiple roles)
• Oligodendria (form myelin in CNS)
• Schwann cells (form myelin in PNS)
• Microglia (CNS macrophage)
• Ependymal (lines ventricles forms CSF)

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Neuron
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(No Transcript)
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Tracing the Neural Pathway

• http//www.pfizer.com/brain/dlgame.html
• Dendrite receives stimuli
• Initiates depolarization at cell body
• Electrical impulse jumps from node to node on
  axon
• At end of axon, reaches axon terminal
• Terminal releases neurotransmitters.

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Initiation of Neural Impulse

• A single neuron may synapse with 50,000 other
  neurons
• Each secretes a neurotransmitter or neuropeptide
• Hundreds of possible chemicals
• Some excitatory
• Some inhibitory
• Varying strength
• Neuron must interpret this cacophony and
  decide...
• To depolarize or not to polarize... that is the
  question

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Nerve Injury and Regeneration

• Axon is severed
• Distal to injury
• Axon disintegrates
• Myelin sheath unwinds into Schwann cells and line
  path
• Proximal
• Disintegration to the next node of Ranvier
• Cell body swells
• Begins to grow from stump of axon down Schwann
  path
• Limited by scar tissue

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Brain

• Cerebral cortex (rind) gray matter
• Frontal
• Parietal
• Temporal
• Occipital
• Wernickes area receptive aphasia
• Brocas area expressive aphasia

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Brain

• Basal ganglia motor function
• Thalamus relay station
• Hypothalamus HR, BP, sleep, etc.
• Cerebellum motor coordination
• Brain stem
• Midbrain
• Pons
• Medulla respiration, heart, GI function, CN 8 -
  12

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Meninges

• 3 membranes surrounding brain and spinal cord
• Dura mater 2 layers
• Periosteum (next to cranium) (epidural space)
• Inner dura (meningeal layer)
• Subdural space between dura mater and next layer
• Arachnoid membrane
• Follows contours of brain but not sulci
• Subarachnoid space between arachnoid and next
  layer
• Pia Mater
• Delicate, follows sulci and fissures

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CSF and Ventricles

• Similar to plasma
• Circulates in ventricles and subarachnoid space
  (125 150 ml) at any one time
• Brain floats in it
• Cushions against jarring and jolting
• Prevents pulling on meninges and blood vessels

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Blood Supply

• Brain receives 20 of cardiac output
• Collateral circulation
• Internal carotid
• Vertebral arteries
• Join in circle of Willis
• Venous drainage
• Does not parallel arterial supply
• Venous plexuses and dural sinuses drain into
  internal jugular vein

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Neurotransmitters

• Multipurpose
• Depends on post-synaptic neuron and receptor type
• Acetylcholine multipurpose
• Crosses neuromuscular junction of motor neurons
• Released by both preganglionic sym parasympa
• Released by postganglionic parasympathetic fibers
• Cholinergic fibers

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Neurotransmitters

• Norepinephrine
• Released by posganglionic sympathetic fibers
• Adrenergic fibers
• Released by adrenal glands
• Function of catecholamines varies by receptor and
  tissue of receptor
• a1 receptor most common
• a2 receptor cause inhibition/relaxation
• ß1 heart and kidney
• ß1 all other beta receptors

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Functions of Autonomic System

• Generally
• Sympathetic stimulation promotes protection of
  host
• Increase BP, HR, glucose
• Increase muscle blood flow and stimulation
• Decrease renal flow and digestion
• Parasympathetic stimulation promotes rest,
  tranquility and maintenance functions
• Digestion
• Secretion of enzymes
• Action is often antagonistic

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Aging

• Extremely complex
• How much is aging, and how much is disease?
• Brain
• Decreased weight and size
• Increased adherence of dura mater to skull
• Fibrosis of meninges
• Widened sulci
• Enlarged ventricles

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Cellular Changes with Age

• Decrease in number of neurons
• Not consistent with cognitive loss
• Implications and reason are unknown
• Cellular changes
• Dendrite changes
• Lipofuscin deposition (Fatty deposits)
• Neurofibrillary tangles (abnormal proteins)
• Senile plaques (nerve degeneration)
• Last two are accelerated in Alzeimer's
• Changes is neurotransmitter function

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Tests of Nervous Function

• X-ray primarily for bony structures
• CT 2-D recreation from multiple X-rays
• Structures, tumors, hemorrhage (with or without
  contrast)
• MRI magnetic field soft tissue analysis
• MRA (angiography) visualization of blood vessels
  (stroke and TIA)
• PET injection of radioactive substances detects
  positrons indicates physiologic processes

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Tests of Nervous Function

• Brain scan uptake of radioactive isotopes
• Cerebral angiography
• Myelography x-ray with subarachnoid dye
• Echoencephalography (ultrasound)
• Electroencephalography (EEG) seizures
• Evoked potentials
• CSF analysis protein, blood, organisms

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Spinal Cord

• Nerve cell bodies arranged in horns
• Nerve pathways cross in the spinal cord
• Eg. Sensation of the left side of the body enters
  the left dorsal horn, and crosses to the right
  ventral horn and travels to right hemisphere
• Sensation
• Spinothalamic tract pain, temperature, crude and
  light touch
• Posterior columms does not cross sides
  position, vibration, finely localized touch