CLASSIFICATIONS
What type of receptor detects temperature changes (hot/cold)?
Thermoreceptors
What are the receptors that detect painful stimuli called?
Nociceptors
Which cranial nerve carries smell signals to the brain?
CN I — Olfactory nerve
Name the two locations where baroreceptors are found.
Carotid sinus and Aortic arch
What is the process of converting stimulus energy into an electrical signal called?
Sensory transduction
What are receptors called that are located at or near the body surface, responding to external stimuli?
Exteroceptors
Which fiber type carries fast, sharp "first pain" and at what speed?
Aδ (A-delta) fibers — 5–30 m/s, myelinated
Name the five basic taste qualities.
Sweet, Salty, Sour, Bitter, Umami
What happens to heart rate when blood pressure suddenly rises? (baroreceptor reflex)
↑BP → ↑baroreceptor firing → ↑parasympathetic tone → ↓HR (bradycardia) + vasodilation → BP normalizes
What minimum membrane potential must a generator potential reach to trigger an action potential?
Threshold potential — approximately −55 mV
Which encapsulated receptor detects deep pressure and vibration?
Pacinian corpuscles
Name the three endogenous opioids that modulate pain.
Endorphins, enkephalins, and dynorphins
What makes the olfactory pathway unique compared to all other sensory systems?
It is the ONLY sensory system that bypasses the thalamus — directly connects to the limbic system (piriform cortex)
Where are central chemoreceptors located and what is their primary stimulus?
Ventral medulla oblongata; primary stimulus is ↑CO₂ → ↑H⁺ in CSF
How does the nervous system encode stimulus intensity?
Frequency coding — stronger stimulus = higher rate (frequency) of action potentials per second
What is the structural difference between free nerve endings and encapsulated receptors?
Free nerve endings have NO connective tissue capsule; encapsulated receptors are surrounded by a connective tissue capsule
List the full ascending pain pathway from stimulus to cortex. ✅ Noxious stimulus → Aδ/C fibers → dorsal horn (laminae I, II, V) → spinothalamic tract → VPL thalamus → somatosensory cortex (SI/SII) + anterior cingulate + insula
Noxious stimulus → Aδ/C fibers → dorsal horn (laminae I, II, V) → spinothalamic tract → VPL thalamus → somatosensory cortex (SI/SII) + anterior cingulate + insula
Describe the signal transduction cascade for sour (acid) taste detection.
H⁺ ions block K⁺ channels → reduced K⁺ efflux → membrane depolarization → neurotransmitter release
Why can't central chemoreceptors detect low oxygen levels directly?
Because O₂ does not significantly cross the blood-brain barrier to change CSF pH — only CO₂ crosses freely. Peripheral chemoreceptors (carotid bodies) detect ↓PaO₂
A patient touches a hot surface and feels sharp pain immediately, then a deep aching burn seconds later. Explain using fiber types.
Sharp immediate pain = Aδ fibers (myelinated, fast: 5–30 m/s). Delayed aching pain = C fibers (unmyelinated, slow: 0.5–2 m/s) — the delay is due to much slower conduction velocity
Name all three classification systems used to categorize sensory receptors.
By stimulus type (mechano/thermo/noci/photo/chemo/baro), by location (extero/intero/proprio), and by structure (free/encapsulated)
What is the difference between primary and secondary hyperalgesia in terms of mechanism and location?
Primary hyperalgesia = peripheral sensitization at injury site (PGE₂, bradykinin, histamine). Secondary hyperalgesia = central sensitization in the dorsal horn (wind-up phenomenon), occurring in surrounding uninjured tissue
Name the three cranial nerves that carry taste signals, their specific tongue regions, and the brainstem nucleus where they first synapse.
CN VII (anterior 2/3 of tongue), CN IX (posterior 1/3), CN X (epiglottis/pharynx) → all synapse in the Nucleus Tractus Solitarius (NTS) in the medulla
Explain baroreceptor resetting and its clinical significance in chronic hypertension.
Baroreceptors adapt (reset) to sustained high pressure over days, treating the elevated BP as the new "normal." In chronic hypertension this means the reflex operates around an elevated set-point, contributing to maintained hypertension
Compare phasic vs tonic receptors: definition, what each encodes, and give two named examples of each.
Phasic (fast-adapting): fire at stimulus onset then stop → encode CHANGE; e.g. Pacinian corpuscles, Meissner's corpuscles. Tonic (slow-adapting): fire continuously during stimulus → encode DURATION & intensity; e.g. Merkel's discs, Ruffini endings, muscle spindles, nociceptors