A&P Study Guide on the Nervous System and Special Senses

The Brain and Cranial Nerves

• Brain Development and Organization

  • Primary Brain Vesicles: Prosencephalon, Mesencephalon, Rhombencephalon

  • Secondary Brain Vesicles:

  • Telencephalon: Forms the cerebrum

  • Diencephalon: Includes thalamus, hypothalamus, epithalamus

  • Mesencephalon: Midbrain

  • Metencephalon: Forms the pons and cerebellum

  • Myelencephalon: Forms the medulla oblongata

• Brain Orientation Terms:

  • Rostral: Anterior/front

  • Caudal: Posterior/back

  • Dorsal: Superior/top

  • Ventral: Inferior/bottom

• Brain Coverings and Protection:

  • Cranial Meninges (superficial to deep):

  • Dura mater: Dense connective tissue, two layers

  • Arachnoid mater: Web-like structure for cushioning

  • Pia mater: Thin layer following the contours of the brain

  • Dural Septa:

  • Falx cerebri: Separates cerebral hemispheres

  • Tentorium cerebelli: Separates cerebrum from cerebellum

  • Falx cerebelli: Divides cerebellar hemispheres

• Cerebrospinal Fluid (CSF):

  • Production: Choroid plexus

  • Volume: ~130 ml

  • Flow Path: Ventricles → Subarachnoid space → Arachnoid villi → Blood

• Brain Structures:

  • Cerebrum Lobes and Functions:

  • Frontal lobe: Motor control, speech, personality

  • Parietal lobe: Sensory data, spatial awareness

  • Temporal lobe: Hearing, memory, emotion

  • Occipital lobe: Vision processing

  • Cerebral Lateralization:

  • Left Hemisphere: Language, reasoning

  • Right Hemisphere: Creativity, visuospatial skills

  • Diencephalon Structures:

  • Thalamus: Sensory relay center

  • Hypothalamus: Homeostasis, hormonal regulation

• Brainstem:

  • Functions:

  • Midbrain: Visual and auditory reflexes

  • Pons: Sound localization

  • Medulla Oblongata: Vital functions like breathing

• Cranial Nerves:

  • I: Olfactory (smell)

  • II: Optic (vision)

  • III: Oculomotor (eye movement)

  • V: Trigeminal (facial sensation)

  • VII: Facial (expression, taste)

  • VIII: Vestibulocochlear (hearing, balance)

General Sensory Concepts

• Key Terms:

  • Stimulus: Environmental changes detected by receptors

  • Sensation: Awareness of stimuli

  • Adaptation: Sensitivity reduction to continuous stimulus

• Receptor Classification:

  • By Modality:

  • Mechanoreceptors (touch)

  • Chemoreceptors (chemicals)

  • Photoreceptors (light)

  • By Location:

  • Exteroceptors (external environment)

  • Interoceptors (internal organs)

  • Proprioceptors (body position)

• Tactile Receptors:

  • Unencapsulated: Free nerve endings, root hair plexuses

  • Encapsulated: Tactile corpuscles, lamellated corpuscles

Special Senses

Taste (Gustation)

• Taste Papillae: Types include filiform, fungiform, vallate, foliate

• Taste Sensations:

  • Sweet: Sugars

  • Sour: Acids

  • Salty: Metals

  • Bitter: Alkaloids

  • Umami: Amino acids

• Taste Pathway: From primary axons → thalamus → gustatory cortex

Smell (Olfaction)

• Olfactory Epithelium: Composed of receptor cells, supporting cells, basal cells

• Functionality: Direct projection to limbic system influences emotions

Vision

• Eye Structures:

  • Fibrous Tunic: Cornea, sclera

  • Vascular Tunic: Iris, ciliary body, choroid

  • Neural Tunic: Retina (contains rods and cones for light detection)

• Lens Accommodation: Adjustments for near and far vision

• Visual Pathway: From optic nerve to occipital lobe

Hearing and Balance

• Ear Divisions:

  • External: Auricle, ear canal, tympanic membrane

  • Middle: Ossicles and auditory tube

  • Inner: Cochlea and balance organs

• Sound Transmission: Waves → tympanic membrane → ossicles → cochlea

Spinal Cord and Spinal Nerves

• Structure:

  • Length: 16-18 inches; regions (Cervical, Thoracic, Lumbar, Sacral, Coccygeal)

  • Gray Matter: Butterfly-shaped, includes horns for sensory/motor neurons

  • White Matter: Surrounds gray matter, includes funiculi

• Spinal Nerves (31 pairs):

  • Sensory: Afferent fibers from posterior roots

  • Motor: Efferent fibers from anterior roots

• Reflexes:

  • Components: Stimulus → sensory neuron → integration → motor neuron → effector

  • Types: Monosynaptic, polysynaptic (e.g., withdrawal reflex)