Nervous System and special ssnses

• Central Nervous System consists of the Brain and Spinal Cord, acting as the command center that interprets and issues commands
• Peripheral Nervous System includes nerves that act as communication lines
• Sensory (afferent) neurons carry information, while Motor (efferent) neurons carry impulses away
• Motor neurons have two subdivisions:

  • Somatic = voluntary
  • Autonomic = involuntary, further divided into sympathetic (fight or flight) and parasympathetic (rest and digest)
• Neuroglia are support cells in the CNS that support, insulate, and protect
• CNS glial cells include:

  • Astrocytes: abundant cells that control the chemical environment of the brain
  • Microglia: spiderlike cells that monitor health and dispose of debris
  • Ependymal cells: line cavities and have cilia to assist with the circulation of cerebrospinal fluid
  • Oligodendrocytes: wrap around and produce myelin sheaths
• PNS glial cells include:

  • Schwann Cells: form myelin sheath
  • Satellite Cells: protect and cushion
• Neurons, or nerve cells, transmit messages (nerve impulses) and consist of a cell body and processes
• Cell body is the metabolic center of the neuron, containing Nissl bodies (RER) and neurofibrils that maintain cell shape
• Processes of neurons include:

  • Dendrites: conduct impulses towards the cell body
  • Axons: conduct impulses away from the cell body
  • Synaptic cleft: the gap between neurons
  • Synapse: the junction between neurons
• Myelin is a fatty material covering axons, and myelin sheaths are produced by Schwann cells in the PNS and Oligodendrocytes in the CNS
• Functional properties of neurons include irritability (response) and conductivity (transmission)
• Reflex arcs are where reflexes occur and consist of sensory receptors, sensory neurons, integration center (CNS), motor neurons, and effector organs
• Brain regions include:

  • Cerebral hemispheres
  • Diencephalon
  • Brain stem
  • Cerebellum
• Cerebral hemispheres make up half of the brain mass and consist of the cortex (surface gray matter), white matter, and basal nuclei (deep pockets of gray matter)
• Cerebral cortex includes the primary somatic sensory area and areas for vision, auditory, olfactory, and motor functions
• Basal Nuclei are islands of gray matter under white matter that regulate voluntary motor functions
• Diencephalon includes the thalamus (relay station), hypothalamus (regulates body temperature and autonomic nervous system), and epithalamus (forms the roof)
• Brain stem attaches to the spinal cord and consists of the midbrain, pons, medulla oblongata, and reticular formation with the reticular activating system (RAS)
• Cerebellum controls balance and coordination of body movement
• Protection of the CNS includes the meninges, cerebrospinal fluid, and the blood-brain barrier
• Traumatic brain injuries can result in concussion, contusion, or death, affecting nervous tissue and functions
• Brain dysfunctions like Cerebrovascular accidents (strokes) and Transient Ischemic Attacks (TIAs) can lead to paralysis, speech impairments, and other issues
• Spinal Cord extends from the foramen magnum to the lumbar vertebrae, with functions in two-way conduction and housing 31 pairs of spinal nerves
• PNS consists of nerves and ganglia outside the CNS, with nerves being bundles of neurons and having connective tissue sheaths
• Cranial nerves are 12 pairs of nerves, with most being mixed nerves and serving sensory and motor functions
• Cranial nerves consist of 12 pairs, with most being mixed nerves, but three are sensory only: Optic, Olfactory, and Vestibulocochlear
• Cranial nerves can be remembered using the mnemonic:

  • Oh - olfactory = smell
  • Oh - optic = vision
  • Oh - oculomotor = control of eyeball/pupils
  • To - trochlear = one external eye muscle
  • Touch - trigeminal = skin
  • And - abducens = rolls the eye laterally
  • Feel - facial = facial expression / taste
  • Very - vestibulocochlear = hearing
  • Green - glossopharyngeal = throat
  • Vegetables - vagus = digestive and heart activity
  • A - accessory = sternocleidomastoid and trapezius muscles
  • H - hypoglossal = tongue
• Spinal nerves consist of 31 pairs
• Ramus is a branch of a spinal nerve, with Dorsal rami serving the skin and muscles, and Ventral rami (T1-T2) serving as intercostal nerves
• Ventral rami (except T1-T2) form a complex network
• Plexus refers to networks of nerves for limbs
• There are four plexuses:

  1. Cranial = respiratory paralysis

  2. Bronchial = inability to flex hands

  3. Lumbar = legs

  4. Sacral = hip, flex knee
• Preganglionic neurons originate in the brain or spinal cord, while postganglionic neurons innervate organs
• The Craniosacral division is the parasympathetic division, while the Thoracolumbar division is the sympathetic division
• Parasympathetic division uses acetylcholine, while the sympathetic division uses norepinephrine
• Sympathetic division is known as the "fight or flight" response, while the parasympathetic division is associated with "rest and digest"
• Parkinson's Disease is a progressive degenerative disorder characterized by shaking palsy
• Parkinsonism involves degenerative changes in basal ganglia function
• Pathophysiology of Parkinson's includes the loss of neurons, presence of Lewy bodies, nigrostriatal and dopamine loss, and reduced activation of dopamine-1 and 2