ANS, General Senses, Gustation, Olfaction - Lab Flashcards
Sympathetic Chain Ganglion
- clusters of autonomic motor neuron cell bodies located in a vertical chain on both sides of the spinal column.
- part of the sympathetic division of the autonomic nervous system and serve as relay points where preganglionic neurons from the spinal cord synapse with postganglionic neurons.
- distribute sympathetic signals throughout the body, allowing the sympathetic nervous system to influence organs in the head, thorax, body wall, and limbs.
29 and 30
30 -> white ramus communicans
- lateral branch that carries myelinated preganglionic sympathetic fibers from the spinal nerve to the sympathetic chain ganglion.
29 -> gray ramus communicans
- lateral branch that carries unmyelinated preganglionic sympathetic fibers from the spinal nerve to the sympathetic chain ganglion.
The white ramus communicans is located laterally and more superior, while the gray ramus communicans lies more medially and inferior relative to it.
Define General Sense
Sensory information detected by receptors distributed throughout the body (e.g., touch, pain, pressure, temperature, proprioception).
Define special sense
Senses with specialized organs: vision, hearing, smell, taste, and balance.
1. Vision • Organ: Eye (retina with photoreceptors: rods and cones) 2. Hearing (Audition) • Organ: Cochlea in the inner ear (contains hair cells) 3. Equilibrium (Balance) • Organ: Vestibular apparatus in the inner ear (semicircular canals, utricle, and saccule) 4. Smell (Olfaction) • Organ: Olfactory epithelium in the nasal cavity 5. Taste (Gustation) • Organ: Taste buds on the tongue (especially in papillae)
Define Nociceptor
A sensory receptor that detects pain from tissue damage, chemical irritation, or extreme temperatures.
Nociceptors are free nerve endings
Define Thermoreceptor
A receptor that detects temperature changes, including heat and cold.
Free nerve endings
Define Mechanoreceptor. List three types
Mechanoreceptors: Receptors that respond to physical deformation (e.g., pressure, vibration, stretch).
1 Tactile receptors: Detect touch, pressure, and vibration at the skin surface.
- Baroreceptors: Monitor pressure changes in organs and blood vessels (e.g., blood pressure).
- Proprioceptors: Detect body position and movement by monitoring muscle and joint stretch.
Free Nerve Endings
- sensory receptors consisting of bare, branching dendrites that detec:
1. pain (nociception)
2. temperature (thermoreception)
3. crude touch or pressure.
They are primarily found in the papillary layer of the dermis and extend into the epidermis, including the stratum basale.
Tactile (merkel) discs
- mechanoreceptors that detect fine touch and sustained pressure, especially in areas requiring high tactile resolution (e.g., fingertips)
located in the stratum basale of the epidermis, where Merkel cells synapse with sensory nerve endings.
Hair Root Plexus
- network of free nerve endings that wraps around the base of a hair follicle.
- rapidly adapting mechanoreceptor, detecting movement or displacement of hair (e.g., light touch or vibration).
Tactile (Meissner’s) corpuscles
- encapsulated mechanoreceptors that detect
1. light touch
2. texture
3. low-frequency vibration.
They are rapidly adapting, meaning they respond quickly to changes in stimuli.
They are located in the papillary layer of the dermis, especially in hairless (glabrous) skin such as the fingertips, lips, palms, and soles.
Lamellated (Pacinian) Corpuscles
mechanoreceptors that detect
1. deep pressure
2. high-frequency vibration
3. stretch.
They are located in the deep dermis and hypodermis, as well as in some internal structures like joint capsules, mesenteries, and walls of some viscera
bulbous (Ruffini’s) corpuscles
mechanoreceptors that detect
1. skin stretch
2. contribute to perception of continuous pressure and joint movement.
They are located in the deep dermis, hypodermis, and joint capsules
Muscle spindles
stretch receptors that signal the length and changes in length of muscles
They lie within an independent capsule, parallel to the main muscle. They are therefore stretched when the muscle lengthens but shorten when the muscle contracts
Neurotendinous (Golgi tendon) organ
Neurotendinous (Golgi tendon) organ
proprioceptors that detect tension or force within tendons when a muscle contracts. They help protect muscles and tendons by triggering reflex inhibition of the muscle if excessive tension is detected.
located at the junction between skeletal muscle and tendon.
Joint Capsule receptor
mechanoreceptors and proprioceptors that detect pressure, stretch, and movement within synovial joints. They help monitor joint position and contribute to proprioceptive feedback for coordinated movement.
located within the fibrous capsule of synovial joints. Include Ruffini endings, Pacinian corpuscles, golgi-like receptors, and free nerve endings
Olfactory Epithelium
A specialized pseudostratified columnar epithelium located in the roof of the nasal cavity, responsible for detecting airborne odorants.
Cell types:
- Olfactory receptor cells – bipolar neurons with non-motile cilia that bind odorants; their axons form cranial nerve I
- Supporting cells – columnar epithelial cells that provide structural and metabolic support
- Basal cells – stem cells
- Bowman’s glands (in underlying lamina propria) – secrete mucus to trap and dissolve odorants
Odorants must dissolve in the mucus to bind receptors on olfactory cilia and initiate smell perception.
Olfactory Nerves
Function:
- Transmit sensory information about smell from the nasal cavity to the olfactory bulb
- From the bulb, signals are relayed via the olfactory tract to the olfactory cortex, limbic system, and hypothalamus for odor perception and emotional response
Location:
- Originate from olfactory receptor neurons in the olfactory epithelium (roof of nasal cavity)
- Their axons bundle to form olfactory nerve fibers
- Pass through the cribriform plate of the ethmoid bone
- Synapse in the olfactory bulb just above the nasal cavity
Olfactory Tract
Location:
- Extends from the olfactory bulb along the inferior surface of the frontal lobe
- Continues posteriorly to reach the olfactory cortex, amygdala, and hypothalamus
Function:
- Carries secondary sensory signals from the olfactory bulb to higher brain regions
- Involved in conscious perception of odors, as well as emotional and behavioral responses to smells via connections to the limbic system
Olfactory Bulb
Function:
- Acts as the first processing center for olfactory signals
- Olfactory receptor neuron axons synapse here with mitral and tufted cells in structures called glomeruli
- Refines, amplifies, and relays odor signals to the olfactory tract, which sends them to the olfactory cortex and limbic system
Location:
- Sits just above the cribriform plate of the ethmoid bone, on the inferior surface of the frontal lobe
- Receives input from olfactory nerve fibers (cranial nerve I) that pass through the cribriform plate
Cribriform plate with olfactory foramina
Function:
- Contains numerous small holes called olfactory foramina
- Allows olfactory nerve fibers (axons of receptor neurons from the nasal cavity) to pass through the bone and reach the olfactory bulb above
- Serves as a critical structural pathway linking the peripheral and central components of the olfactory system
Location:
- A horizontal, perforated portion of the ethmoid bone
- Forms the roof of the nasal cavity and part of the floor of the anterior cranial fossa
Vallate (Circumvallate) Papillae
Location:
- Found in a V-shaped row near the posterior third of the tongue
- Each papilla is large and surrounded by a deep circular trench
Function:
- Contain numerous taste buds along the sides of the trench walls
- Specialized for detecting bitter tastes
- Associated with von Ebner’s glands, which secrete fluid to flush the trench and help clear chemicals for new taste detection
Foliate Papillae
Location:
- Located on the lateral edges of the posterior tongue
- Appear as vertical folds or ridges on the sides of the tongue
Function:
- Contain taste buds (especially in children; fewer in adults)
- Involved in detecting sour tastes
- Less prominent with age and may degenerate in adulthood
Filiform Papillae
Location:
- Cover most of the anterior two-thirds of the tongue
- Found between and around the fungiform papillae
Function:
- Do not contain taste buds
- Provide friction and texture to help manipulate food during chewing and speech
- Have a keratinized tip, giving the tongue its rough surface
Fungiform Papillae
Location:
- Scattered across the anterior two-thirds of the tongue
- Most numerous near the tip and lateral edges
- Appear as small, mushroom-shaped projections interspersed among filiform papillae
Function:
- Contain taste buds (primarily on the top surface)
- Involved in detecting sweet, salty, and umami tastes
- Also have a rich blood supply, giving them a red appearance
Vallate (Circumvallate) Papillae
Location:
- Found in a V-shaped row near the posterior third of the tongue
- Each papilla is large and surrounded by a deep circular trench
Function:
- Contain numerous taste buds along the sides of the trench walls
- Specialized for detecting bitter tastes
- Associated with von Ebner’s glands, which secrete fluid to flush the trench and help clear chemicals for new taste detection
Taste Pore
Location:
- A small opening on the surface of the epithelium of taste buds
- Found within the trenches or walls of certain papillae (especially vallate and foliate papillae)
Function:
- Serves as the entry point for dissolved chemicals (tastants) to reach the gustatory receptor cells
- Allows tastants in saliva to interact with microvilli on gustatory cells, initiating taste signal transduction
Gustatory Receptor Cell
Location:
- Found inside the taste bud, deep to the taste pore
- Their microvilli (taste hairs) extend up through the taste pore to reach the surface of the tongue epithelium
Function:
- Detect dissolved tastants that enter through the taste pore
- Convert chemical signals into neural signals by releasing neurotransmitters to associated sensory neurons
- Continuously regenerated by nearby basal cells
Taste Hairs (Microvilli)
Location:
- Extend from the apical end of gustatory receptor cells
- Project through the taste pore to the surface of the tongue epithelium
Function:
- Serve as the sensory interface between tastants in saliva and the gustatory receptor cells
- Contain membrane receptors that bind dissolved chemicals (tastants)
- Initiate the taste transduction process, leading to neurotransmitter release and activation of sensory neurons
Describe the 5 Primary Tastants
There are five primary taste modalities, each associated with specific types of receptors and distinct physiological roles:
-
Sweet
- Detected by: G-protein-coupled receptors (GPCRs)
- Signals presence of energy-rich nutrients (e.g., sugars)
-
Salty
- Detected by: Na⁺ ion channels
- Indicates presence of sodium and other electrolytes
-
Sour
- Detected by: H⁺ ions (acidity) through proton-sensitive ion channels
- Reflects pH balance and possible spoiled or unripe food
-
Bitter
- Detected by: GPCRs tuned to various compounds
- Often signals potential toxins or poisons; highly sensitive even at low concentrations
-
Umami
- Detected by: GPCRs that bind glutamate and other amino acids
- Indicates presence of proteins; associated with savory flavor (e.g., meats, broths)
Each tastant stimulates gustatory receptor cells, which activate sensory neurons leading to the gustatory cortex via cranial nerves VII, IX, and X.
