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Special Senses & Nervous System Integration - Coggle Diagram
Special Senses & Nervous System Integration
Anatomy & Histology of Sensory Organs
Eye: Three layers (fibrous sclera/cornea, vascular choroid/ciliary body/iris, neural retina).
Nose: Olfactory epithelium with bipolar receptor neurons, supporting cells, and basal stem cells.
Tongue: Papillae (filiform, fungiform, vallate, foliate) containing taste buds with gustatory receptor cells.
Ear: External, middle (ossicles), and inner ear (cochlea for hearing, vestibule & semicircular canals for balance).
Somatosensory: Cutaneous receptors like Meissner's and Pacinian corpuscles embedded in skin layers.
Major Functions of the Nervous System
Sensation: Detecting environmental or internal changes via receptors and transmitting signals via afferent pathways to the CNS.
Integration: Processing and interpreting sensory input in the CNS, combining it with memory, emotion, and context.
Response: Executing motor commands via efferent neurons to somatic (skeletal muscle) or autonomic (smooth/cardiac muscle, glands) effectors.
Types of Sensory Receptors
Mechanoreceptors: Respond to physical forces like touch, pressure, vibration, and sound.
Thermoreceptors: Detect temperature changes (heat and cold).
Nociceptors: Detect pain and harmful conditions signaling potential injury.
Photoreceptors: Detect light in the retina (rods for low-light, cones for color vision).
Chemoreceptors: Detect chemical signals vital for taste and smell.
Sensory-Motor Response Pathway (Reflex Arc)
Step 1: Stimulus activates a peripheral sensory receptor.
Step 2: Receptor generates graded potential, triggering an action potential in the afferent neuron.
Step 3: Afferent neuron carries impulse toward the CNS.
Step 4 & 5: CNS processes input and integrates information (synapsing with interneurons).
Step 6 & 7: Motor command travels via efferent neuron to an effector (muscle/gland) to carry out the response.
Somatosensory Modalities & Pathways
Discriminative Touch & Proprioception: Handled by the Dorsal Column-Medial Lemniscal Pathway (decussates in the medulla, synapses in VPL thalamus, reaches S1 cortex).
Pain & Temperature: Handled by the Anterolateral / Spinothalamic Pathway (decussates immediately in spinal cord, ascends to thalamus and S1).
Crude Touch & Pressure: Carried primarily via the anterolateral pathway.
Divisions of the Somatosensory System
Exteroceptive Division: Arises from external environmental stimuli on cutaneous surfaces and mucous membranes (mechanoreception, thermoreception, nociception).
Proprioceptive Division: Conveys body position and movement from skeletal muscles (spindles), tendons (Golgi organs), and joint capsules.
Enteroceptive (Viscerocceptive) Division: Monitors internal physiological states from thoracic/abdominal viscera and blood vessels (distension, pH, O2O2/CO2CO2).
Structures of Special Senses
Taste: Papillae and taste buds on the tongue connected via cranial nerves VII, IX, and X.
Smell: Olfactory sensory neurons in the upper nasal cavity forming Cranial Nerve I and synapsing in the olfactory bulb.
Hearing & Balance: Inner ear structures including the cochlea, semicircular canals, utricle, and saccule connected via CN VIII.
Vision: Eyeball structures, chambers, and retinal layers focusing light onto photoreceptors.
Taste Transduction Mechanisms
Ion Channels (Salty & Sour): Direct influx of Na+Na+ (ENaCENaC) or H+H+ ions causing direct cell depolarization.
GPCRs (Sweet, Umami, Bitter): Tastants bind to G-protein coupled receptors (TAS2RTAS2R, TAS1RTAS1R), triggering intracellular second messengers and Ca2+Ca2+ release.
Gustatory Pathway: Signals travel via CN VII, IX, and X to the medulla, thalamus (VPM), and primary gustatory cortex.
Mechanoreception for Hearing & Balance
Hearing (Cochlea): Sound waves vibrate the tympanic membrane and ossicles, moving perilymph and basilar membrane; hair cells bend against the tectorial membrane, opening K+K+ channels for depolarization.
Balance (Otolith Organs): Utricle and saccule detect linear movements via otoliths shifting over hair cells.
Balance (Semicircular Canals): Detect rotational motion as endolymph movement displaces the cupula and bends hair cells.
Supporting Structures & Anatomy of the Eyeball
Supporting Structures: Eyelids, eyelashes, eyebrows, conjunctiva, lacrimal apparatus, and six extrinsic eye muscles.
Fibrous Tunic: Tough protective outer layer consisting of the white sclera and transparent cornea.
Vascular Tunic: Middle pigmented layer containing the choroid, ciliary body, and iris.
Retina: Innermost neural coat containing photoreceptors (rods and cones), bipolar cells, and ganglion cells forming the optic nerve.
Chaidir Akbar Nugroho
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