NERVOUS

• Function of the Nervous System

  • Maintaining homeostasis
  • Receiving sensory input
  • Integrating information
  • Controlling muscles and glands
  • Establishing and maintaining mental activity
• Main Parts of the Nervous System

  • Brain
  • Spinal cord
  • Nerve cell
• Other Main Parts of the Nervous System

  • Nerve (bundle of axons)
  • Ganglion (collection of neuronal bodies)
  • Plexus (braid of network)
  • Synapse (connection)
• Divisions of the Nervous System

  • Central nervous system - Brain and Spinal cord
  • Peripheral nervous system - Nervous tissue outside the CNS
• Support Cells of the Central Nervous System

  • Ependymal - ventricle of brain and central canal of spinal cord, choroid plexuses (CSF)
  • Microglia - immune cells of CNS
  • Oligodendrocytes - myelin sheath around multiple axons
• Support Cells of the Peripheral Nervous System

  • Schwann cells - myelin sheath around one axon
  • Satellite cells - protects from heavy metal poisoning
• Cranial Nerves


  • Olfactory Nerve (CN I) - Responsible for smell, closest to the front of the head, disorders can affect sense of smell
  • Optic Nerve (CN II) - Involved in vision, conditions can impact vision
  • Oculomotor Nerve (CN III) - Controls most eye movements and pupil constriction, third nerve palsy can cause eyelid drooping and eye movement issues
  • Trochlear Nerve (CN IV) - Controls the superior oblique muscle for eye movement, fourth nerve palsy affects eye alignment
  • Trigeminal Nerve (CN V) - Sensation in the face, chewing muscles, trigeminal neuralgia causes facial pain
  • Abducens Nerve (CN VI) - Controls the lateral rectus muscle for eye abduction, sixth nerve palsy leads to inward eye deviation
  • Facial Nerve (CN VII) - Controls facial expression, taste, and tear production, Bell's palsy causes temporary facial weakness
  • Vestibulocochlear Nerve (CN VIII) - Involved in hearing and balance, hearing loss or vertigo can result
  • Glossopharyngeal Nerve (CN IX) - Sensation in the throat, taste, and swallowing, glossopharyngeal neuralgia causes throat pain
  • Vagus Nerve (CN X) - Controls heart rate, digestion, and other autonomic functions, vagus nerve disorders can affect various organs
  • Accessory Nerve (CN XI) - Innervates the sternocleidomastoid and trapezius muscles, damage can lead to shoulder weakness
  • Hypoglossal Nerve (CN XII) - Controls tongue movement, hypoglossal nerve palsy affects speech and swallowing
• Spinal Nerves


  • 8 cervical nerves
  • 12 thoracic nerves
  • 5 lumbar nerves
  • 5 sacral nerves
  • 1 coccygeal nerve
• Roots of Spinal Nerves

  1. Each spinal nerve has both anterior (ventral) and posterior (dorsal) roots

  2. These roots contain a mixture of motor and sensory fibers

  3. The anterior root carries efferent nerve fibers (motor commands from the CNS to muscles)

  4. The posterior root contains afferent nerve fibers (sensory information from the periphery to the CNS)

  5. The roots unite to form a spinal nerve
• Function of Spinal Nerves

  • Sensory Information: Spinal nerves receive sensory input from the periphery and transmit it to the central nervous system (CNS)
  • Motor Commands: They also carry motor commands from the CNS to the muscles of the periphery
  • Autonomic Fibers: Spinal nerves include autonomic fibers involved in regulating various bodily functions
• Clinical Relevance of Spinal Nerves

  • Spinal nerves can be affected by conditions such as pinched nerves, disk protrusion, disk herniation, and spinal stenosis
  • Understanding spinal nerve anatomy is crucial for diagnosing and treating related issues
• Regions of Spinal Nerves

  • Cervical Spinal Nerves (C1-C8) - Serve various functions related to the neck, shoulders, and upper limbs
  • Thoracic Spinal Nerves (T1-T12) - Innervate the chest, abdominal muscles, and parts of the back
  • Lumbar Spinal Nerves (L1-L5) - Supply the lower abdomen, hips, and legs
  • Sacral Spinal Nerves (S1-S5) - Control functions in the pelvis, buttocks, and lower limbs
  • Coccygeal Nerve (Co1) - Contributes to sensory and motor functions in the tailbone region
• Other Nerves


  • Sciatic Nerve - Largest nerve in the body, responsible for leg movement
  • Phrenic Nerve - Regulates breathing
  • Pudendal Nerve - Provides genital sensation
  • Facial Nerve - Controls facial expression
  • Vestibulocochlear Nerve - Involved in hearing and balance
  • Glossopharyngeal Nerve - Functions in tongue and throat movement
• Reflexes


  • Quick and ready to react
  • For protection and homeostasis
• Types of Reflexes


  • Somatic Reflexes - Involve the somatic nervous system, which deals with skin, muscles, and conscious activities (like limb movement)
  • Autonomic Reflexes - Coordinated by specific parts of the brain and involve the autonomic nervous system, deal with internal processes (e.g., digestion, blood flow)
• Action Potentials


  • Electric signals that travel along a neuron's membrane
  • Graded potentials (varying in size) and action potentials (the major signal sent down the axon)
  • Graded potentials occur at the dendrites and cell body, influencing whether an action potential will be sent or not
  • Purpose: Electrical impulses enable communication between neurons and play a crucial role in processes like reflexes and sensory perception
• Cell to Cell Communication

  • Electrical
  • Chemical
• Diseases


  • Alzheimer's disease
  • Cancer
  • Cerebral palsy
  • Epilepsy
  • Huntington's disease
  • Infection (meningitis)
  • Parkinson's disease
  • Stroke
  • Traumatic brain injury
  • Tourette's syndrome