Neurology and Sensory Organs

Posted on May 7, 2024 in Biology

Neuroglia

Types of Neuroglia

  • Astrocytes: Branched cells that form the supporting framework of the central nervous system (CNS).
  • Oligodendrocytes: Form the myelin sheath in the CNS.
  • Microglia: Phagocytize cellular debris.
  • Ependymal Cells: Line the ventricles and central canal of the CNS.

Meninges

The meninges are three layers of protective membranes that surround the brain and spinal cord.

Layers of the Meninges

  • Dura Mater: The outermost and toughest layer, separated from the bone by the epidural space.
  • Arachnoid Mater: A vascular layer located beneath the dura mater, with the subarachnoid space containing cerebrospinal fluid (CSF).
  • Pia Mater: The innermost layer, adhering directly to the brain and spinal cord.

Cranial Nerves

There are 12 pairs of cranial nerves that emerge from the brainstem and innervate various structures in the head and neck.

Cranial Nerves and Their Functions

  1. Olfactory Nerve: Sense of smell
  2. Optic Nerve: Vision
  3. Oculomotor Nerve: Eye movements, pupil constriction, and accommodation
  4. Trochlear Nerve: Eye movements
  5. Trigeminal Nerve: Facial sensations and chewing muscles
  6. Abducens Nerve: Eye movements
  7. Facial Nerve: Facial expressions, tear and salivary gland secretions
  8. Vestibulocochlear Nerve: Hearing and balance
  9. Glossopharyngeal Nerve: Swallowing and taste sensation
  10. Vagus Nerve: Innervates various organs, including the pharynx, larynx, and heart
  11. Spinal Accessory Nerve: Innervates the sternocleidomastoid and trapezius muscles
  12. Hypoglossal Nerve: Tongue movements

Autonomic Nervous System

The autonomic nervous system regulates involuntary bodily functions.

Divisions of the Autonomic Nervous System

  • Sympathetic Nervous System: Prepares the body for fight-or-flight responses, using norepinephrine as its neurotransmitter.
  • Parasympathetic Nervous System: Promotes rest and digestion, using acetylcholine as its neurotransmitter.

Acute Neurological Conditions

  • Facial Paralysis: Weakness or paralysis of facial muscles
  • Hemiplegia/Hemiparesis: Paralysis or weakness on one side of the body
  • Dysarthria: Difficulty speaking
  • Aphasia: Impairment of language abilities
  • Altered Level of Consciousness: Confusion, stupor, or coma
  • Memory Impairment: Amnesia
  • Seizures: Abnormal electrical activity in the brain

Meningitis

Inflammation of the meninges, often caused by infection.

Symptoms of Meningitis

  • High fever
  • Severe headache
  • Neck stiffness
  • Vomiting
  • Confusion or delirium
  • Seizures

Complications of Meningitis

  • Paralysis
  • Deafness
  • Blindness
  • Mental retardation
  • Waterhouse-Friderichsen syndrome

Epilepsy

A neurological disorder characterized by recurrent seizures.

Types of Epilepsy

  • Generalized Epilepsy: Seizures that affect the entire brain, such as tonic-clonic seizures.
  • Partial Epilepsy: Seizures that originate in a specific area of the brain, such as Jacksonian seizures.
  • Febrile Seizures: Seizures triggered by high fever in children.

Dementia

A progressive decline in cognitive function that interferes with daily life.

Types of Dementia

  • Alzheimer’s Disease: The most common type, characterized by diffuse brain atrophy.
  • Pick’s Disease: A rare type with localized brain atrophy.
  • Vascular Dementia: Caused by impaired blood flow to the brain.
  • Senile Dementia: Dementia associated with aging.

Symptoms of Dementia

  • Memory loss
  • Mood changes
  • Impaired coordination
  • Difficulty with language

Parkinson’s Disease

A neurodegenerative disorder characterized by tremors, rigidity, slow movements, and facial inexpressiveness.

Cause of Parkinson’s Disease

Deficiency of the neurotransmitter dopamine.

Eye Anatomy

Layers of the Eye

  • Outer Layer (Fibrous Tunic):
    • Sclera: The white, protective outer layer of the eye.
    • Cornea: The transparent front part of the eye.
  • Middle Layer (Uvea):
    • Choroid: The vascular layer that nourishes the retina.
    • Iris: The colored part of the eye that controls pupil size.
    • Ciliary Body: Produces aqueous humor and controls lens shape.
  • Inner Layer (Retina): The light-sensitive layer that converts light into nerve impulses.

Chambers of the Eye

  • Anterior Chamber: Located between the cornea and iris.
  • Posterior Chamber: Located between the iris and lens.
  • Vitreous Chamber: Filled with vitreous humor, a gel-like substance.

Vision Disorders

  • Presbyopia: Age-related farsightedness due to decreased lens elasticity.
  • Strabismus: Misalignment of the eyes, such as esotropia (crossed eyes) or exotropia (wall-eyed).
  • Glaucoma: Increased intraocular pressure that can damage the optic nerve.
  • Cataracts: Clouding of the lens.
  • Retinal Detachment: Separation of the retina from the underlying choroid.

Ear Anatomy

External Ear

  • Auricle (Pinna): The visible, cartilaginous part of the ear.
  • External Auditory Canal: The passage leading to the eardrum.

Middle Ear

  • Tympanic Membrane (Eardrum): Vibrates in response to sound waves.
  • Ossicles: Three small bones (malleus, incus, and stapes) that transmit vibrations to the inner ear.
  • Eustachian Tube: Equalizes pressure between the middle ear and the atmosphere.

Inner Ear

  • Cochlea: The spiral-shaped organ of hearing.
  • Vestibule: Contains the saccule and utricle, which are involved in balance.
  • Semicircular Canals: Three fluid-filled canals that detect rotational movements.

Hearing Disorders

  • Myringoplasty: Surgical repair of a perforated eardrum.
  • Anosmia: Loss of sense of smell.
  • Parosmia: Distorted sense of smell.
  • Hyperosmia: Increased sensitivity to smells.

Sensory Disorders

  • Hypoesthesia: Decreased sensitivity to stimuli.
  • Paresthesia: Abnormal sensations, such as tingling or numbness.
  • Myringitis: Inflammation of the eardrum.