Exam 3 Review: Special Senses and Autonomic Nervous System

Chapter 17 – Special Senses

General Overview of Special Senses

The special senses include olfaction (smell), gustation (taste), vision, hearing, and equilibrium. Each sense has a distinct anatomical structure and physiological function that allows the body to perceive and respond to environmental stimuli.

• Olfaction (Smell):

  • General Function: Olfaction allows detection of airborne chemicals, which are interpreted as odors.

  • Tissue Layers in Nasal Cavity:

    • Mucous layer: Traps odorant molecules.

    • Basal stem cells: Regenerate olfactory receptor cells.

    • Epithelial cells, bipolar cells, Bowman's glands: Support and nourish olfactory neurons.

    • Connective tissue: Provides structural support.

    • Cribriform plate: Separates nasal cavity from brain; olfactory nerves pass through.

    • Olfactory bulb: Receives input from olfactory receptor cells.

  • Neurons in Nasal Cavity: Bipolar neurons are the primary olfactory sensory cells.

  • Innervation: Olfactory nerve (Cranial Nerve I) innervates the nasal cavity.

  • Steps of Smelling:

    1. Odorant binds to receptor on olfactory cell.

    2. Action potential is generated and transmitted to the olfactory bulb.

    3. Information is relayed to the olfactory cortex for perception.

  • Receptor Types: Olfactory receptors are G-protein coupled receptors located on cilia of olfactory cells.

  • Pathway: Olfactory information is ultimately processed in the cerebral cortex.

• Gustation (Taste):

  • General Function: Gustation detects dissolved chemicals (tastants) in the oral cavity.

  • Tongue Papillae Types:

    • Circumvallate

    • Fungiform

    • Filiform

    • Foliate

  • Taste Buds:

    • Located on papillae except filiform.

    • Composed of gustatory cells and supporting cells.

  • Taste Pathways:

    • Sweet, Bitter, Umami: Involve G-protein coupled receptors; neurotransmitter release upon tastant binding.

    • Salty, Sour: Involve ion channels; sodium or hydrogen ions trigger neurotransmitter release.

• Visual Sensation:

  • General Function: Vision detects and interprets light stimuli.

  • Layers of the Eye:

    • Sclera: Outer protective layer.

    • Choroid: Vascular layer.

    • Retina: Contains photoreceptors (rods and cones).

  • Cornea and Sclera Conditions:

    • Astigmatism: Irregular curvature affects vision.

    • Myopia: Nearsightedness.

    • Hyperopia: Farsightedness.

  • Iris Structure:

    • Controls pupil size; contains melanocytes affecting eye color.

  • Pupillary Muscles:

    • Dilation: Pupillary dilator muscle contracts.

    • Constriction: Pupillary sphincter muscle contracts.

  • Photoreceptors:

    • Rods: Detect dim light.

    • Cones: Detect color and detail.

  • Phototransduction: Conversion of light into electrical signals.

  • Wavelength Detection:

    • Blue cones detect short wavelengths.

    • Green and red cones detect longer wavelengths.

• Hearing and Equilibrium:

  • General Function: Hearing detects sound waves; equilibrium senses head position and movement.

  • Receptors:

    • Hair cells: Mechanoreceptors in ear structures.

  • Ear Regions:

    • Outer ear: Collects sound.

    • Middle ear: Transmits vibrations.

    • Inner ear: Contains cochlea (hearing) and vestibular apparatus (equilibrium).

  • Labyrinths:

    • Bony labyrinth: Surrounds membranous labyrinth.

    • Membranous labyrinth: Contains endolymph and sensory cells.

  • Cochlea:

    • Organ of Corti: Main hearing organ; contains hair cells.

    • Stereocilia vs. Kinocilium: Stereocilia are shorter; kinocilium is a single, longer cilium.

  • Sound Characteristics:

    • Pitch, volume, and tone are determined by frequency and amplitude of sound waves.

  • Vestibule and Semicircular Canals:

    • Detect head position and rotation.

    • Hair cells clustered in specific regions (maculae, cristae ampullaris).

Autonomic Nervous System (ANS)

General Overview

The autonomic nervous system regulates involuntary physiological functions, including heart rate, digestion, respiratory rate, and glandular activity. It is divided into sympathetic and parasympathetic divisions, each with distinct anatomical and functional characteristics.

• Motor Neurons:

  • Somatic vs. Autonomic: Somatic motor neurons control voluntary muscles; autonomic motor neurons regulate involuntary effectors.

  • Pre- and Postganglionic Neurons:

    • Preganglionic: Cell body in CNS; axon projects to ganglion.

    • Postganglionic: Cell body in ganglion; axon projects to effector organ.

• Sympathetic Division:

  • General Function: Prepares body for 'fight or flight' responses.

  • Ganglia Types:

    • Sympathetic Chain Ganglia

    • Collateral Ganglia

    • Adrenal Medulla

  • Neurotransmitters:

    • Preganglionic: Acetylcholine

    • Postganglionic: Norepinephrine (main), some acetylcholine

  • Receptors:

    • Adrenergic (respond to norepinephrine)

    • Cholinergic (respond to acetylcholine)

• Parasympathetic Division:

  • General Function: Promotes 'rest and digest' activities.

  • Ganglia Types:

    • Terminal ganglia: Near or within target organs.

    • Intramural ganglia: Embedded in organ walls.

  • Neurotransmitters:

    • Both pre- and postganglionic neurons release acetylcholine.

  • Receptors:

    • Muscarinic and nicotinic cholinergic receptors.

  • Major Effects:

    • Decreased heart rate

    • Increased digestive activity

    • Constriction of pupils

  • Cranial Nerve X (Vagus): Provides majority of parasympathetic outflow.

• Dual Innervation:

  • Some organs receive input from both sympathetic and parasympathetic divisions, allowing fine-tuned regulation.

Key Terms and Definitions

• Action Potential: Electrical signal generated by neurons.

• Phototransduction: Conversion of light into neural signals in the retina.

• Adrenergic Receptor: Receptor for norepinephrine/epinephrine.

• Cholinergic Receptor: Receptor for acetylcholine.

Example Table: Types of Papillae and Their Functions

Papilla Type	Location	Function
Circumvallate	Back of tongue	Contains taste buds; detects bitter flavors
Fungiform	Tip and sides of tongue	Contains taste buds; detects sweet and salty flavors
Filiform	Throughout tongue	No taste buds; provides texture
Foliate	Sides of tongue	Contains taste buds; detects sour flavors

Key Equations

• Action Potential Generation: $I = g(V - E)$ Where I is current, g is conductance, V is membrane potential, and E is equilibrium potential.

• Frequency of Sound: $f = \frac{v}{\lambda}$ Where f is frequency, v is velocity of sound, and λ is wavelength.

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table and equations are inferred from standard Anatomy & Physiology curriculum.