Please enable JavaScript.
Coggle requires JavaScript to display documents.
The special senses and integrative functions of the nervous system -…
The special senses and integrative functions of the nervous system
Medinna Rasha - 2506557816
Anatomy and Histology of Special and General Sensory Organs
Eyes: Composed of outer fibrous tunic, vascular tunic, and retina. Retina layers process light signals, transmitted via optic nerve (CN II).
Ears (Hearing): Cochlea contains organ of Corti with hair cells acting as mechanoreceptors converting vibrations to nerve impulses. Outer, middle, and inner ear structures facilitate sound transmission.
Ears (Balance): Vestibular apparatus (semicircular canals, utricle, saccule) with hair cells detect head position and movement; signals travel via vestibular nerve (CN VIII).
Nose (Smell): Olfactory epithelium houses bipolar olfactory receptor neurons detecting odor molecules; signals travel via olfactory nerve (CN I).
Tongue (Tasting): Taste buds on papillae contain gustatory receptor cells sensitive to five basic tastes; signals carried by facial (CN VII), glossopharyngeal (CN IX), and vagus nerves (CN X).
Somatosensory: General sense receptors in skin, muscles, joints detect touch, pain, temperature, pressure, and body position; afferent nerves convey signals to CNS.
Functions of the Nervous System
Sensation: Detection of external or internal stimuli by sensory receptors.
Integration: CNS processes and interprets sensory input to make decisions.
Response: Motor neurons send commands to muscles or glands to produce voluntary or reflexive actions.
Types of Sensory Receptors
Mechanoreceptors: Detect mechanical forces like pressure, vibration, stretch.
Thermoreceptors: Respond to temperature changes.
Nociceptors: Detect pain from tissue damage.
Photoreceptors: Respond to light (rods and cones in retina).
Chemoreceptors: Detect chemicals (olfactory and gustatory receptors).
Osmoreceptors: Monitor osmotic pressure of body fluids.
Sensory Receptor–Motor Response Pathway
Stimulus activates sensory receptor.
Transduction: receptor converts stimulus to electrical signal.
Sensory neuron transmits signal to CNS.
CNS integrates and processes the information.
Motor neuron carries command from CNS to effector.
Effector (muscle or gland) produces response.
Major Modalities of Somatosensory Information and Corresponding Pathways
Modalities: Fine touch, vibration, proprioception (body position), pain, temperature.
Dorsal Column-Medial Lemniscal Pathway: Conveys fine touch, vibration, proprioception; crosses over in medulla; terminates in primary somatosensory cortex.
Spinothalamic Pathway: Conveys crude touch, pain, temperature; crosses spinal cord; also terminates in somatosensory cortex.
Body Regions and Categories of Somatosensory System Divisions
Exteroceptive: Skin and external structures; detects external stimuli like touch, temperature, pain.
Proprioceptive: Muscles, tendons, joints, inner ear; monitors body position and movement.
Enteroceptive (Interoceptive): Internal organs and viscera; senses internal conditions like stretch, pain, chemical changes.
Structures Responsible for Special Senses
Taste: Taste buds with gustatory cells on tongue papillae.
Smell: Olfactory epithelium with receptor neurons in nasal cavity.
Hearing: Cochlear hair cells in organ of Corti convert sound to signals.
Balance: Hair cells in semicircular canals, utricle, and saccule detect head movements.
Vision: Eye structures (cornea, lens, retina) detect and process light.
How Different Tastes Are Transduced
Salty and sour tastes: Ion channels allow Na+ or H+ influx causing depolarization.
Sweet, bitter, umami: G-protein coupled receptors activate intracellular signaling cascades.
Resulting neurotransmitter release activates sensory neurons transmitting taste signals to CNS.
Mechanoreception for Hearing and Balance
Hearing: Sound waves vibrate tympanic membrane → ossicles → cochlear fluid → organ of Corti hair cells bend → ion channels open → neurotransmitter release → auditory nerve activation.
Balance: Head movements shift fluid in semicircular canals or otoliths in utricle/saccule → hair cells bend → nerve impulses sent via vestibular nerve.
Structures Around the Eye and Eyeball Structure
Eyelids, eyelashes, eyebrows: Protect and lubricate the eye.
Lacrimal apparatus: Produces and drains tears for eye cleanliness and protection.
Extrinsic eye muscles (cranial nerves III, IV, VI): Control eye movement.
Eyeball layers
Fibrous tunic: sclera (white, protective), cornea (transparent, light refraction).
Vascular tunic: choroid (blood supply), ciliary body (lens shape control), iris (controls pupil size).
Retina: photoreceptors process light signals.
Vitreous humor fills eyeball cavity maintaining shape.