Lecture+23+-+General+and+special+senses
General and Special Senses
Learning Outcomes
Compare and contrast the types of general sensory receptors.
Describe the anatomy of the olfactory receptors and the olfactory pathway connecting these receptors to the cerebral cortex.
Describe the anatomy of the taste receptors and the pathway connecting these receptors to the cerebral cortex.
Describe the anatomy of the external ear, middle ear, and internal ear.
Describe the anatomy of the eye.
Classification of Receptors by Stimulus Type
Mechanoreceptors: Respond to mechanical forces.
Types of stimuli include:
Touch
Pressure
Stretch
Vibration
Itch
Baroreceptors: Specifically monitor blood pressure.
Thermoreceptors: Respond to changes in temperature.
Chemoreceptors:
Respond to chemical substances that mediate the senses of taste and smell.
Photoreceptors:
Respond to light.
Location: Found in the eye.
Nociceptors:
Respond to harmful stimuli, which often result in pain.
Classification of Receptors by Structure
General somatosensory receptors:
Divided into two major groups:
Free nerve endings (Non-encapsulated):
Respond to pain and temperature stimuli.
Encapsulated nerve endings:
Mechanoreceptors enclosed in connective tissue, sensitive to:
Touch
Pressure
Vibration
Proprioception
General Sensory Receptors Classified by Structure and Function (1 of 3)
Free Nerve Endings:
Functional Class:
According to Location: Exteroceptors, interoceptors, and proprioceptors.
According to Stimulus Type: Nociceptors (pain), thermoreceptors (heat and cold), mechanoreceptors (pressure), chemoreceptors.
Body Location:
Most body tissues; particularly dense in connective tissues (ligaments, tendons, dermis, joint capsules, periosteum) and epithelia (epidermis, cornea, mucosae, glands).
Modified free nerve endings:
Epithelial tactile complexes (Merkel discs).
Hair Follicle Receptors:
Tactile cells in and surrounding hair follicles.
General Sensory Receptors Classified by Structure and Function (2 of 3)
Encapsulated Receptors:
Tactile (Meissner's) corpuscles:
Location: Dermal papillae of hairless skin (nipples, external genitalia, fingertips, eyelids).
Functional Class: Exteroceptors, mechanoreceptors (light pressure, discriminative touch, vibration of low frequency), rapidly adapting.
Lamellar (Pacinian) corpuscles:
Location: Dermis and hypodermis; abundant in fingers, soles of feet, external genitalia, nipples.
Functional Class: Exteroceptors, interoceptors, some proprioceptors; mechanoreceptors (deep pressure, stretch, vibration of high frequency), rapidly adapting.
Bulbous corpuscle (Ruffini endings):
Location: Deep in dermis, hypodermis, and joint capsules.
Functional Class: Exteroceptors, proprioceptors; mechanoreceptors (deep pressure and stretch), slowly adapting or nonadapting.
Visceral Sensory
Visceral Pain:
Characteristics: Dull and poorly localized.
Causes: Results from chemical irritation or inflammation rather than cutting of the organs.
Referred Pain:
Phenomenon where visceral pain is perceived in regions of the body with the same somatic origin.
Taste—Gustation
Taste Receptors:
Occur in taste buds mainly located on the surface of the tongue, within tongue papillae.
Five Basic Qualities of Taste:
Sweet
Sour
Salty
Bitter
Umami (elicited by glutamate).
Smell (Olfaction)
Olfactory Receptors:
Located in the olfactory epithelium.
Olfactory Cilia:
Act as receptive structures for smell.
Neural Pathway:
Axons of olfactory sensory neurons penetrate the cribriform plate of the ethmoid bone, enter the olfactory bulbs, and synapse with mitral cells.
Mitral cells transmit impulses along the olfactory tract to the primary olfactory cortex in the temporal lobe.
The Eye and Vision
Vision:
Dominant sense in humans.
70% of all sensory receptors are found in the eyes.
40% of the cerebral cortex processes visual information.
Accessory Structures of the Eye (1 of 2)
Eyebrows:
Coarse hairs on the superciliary arches that help direct sounds.
Eyelids (Palpebrae):
Separated by the palpebral fissure.
Tarsal Plates:
Connective tissue within the eyelids.
Tarsal Glands:
Modified sebaceous glands.
**Conj
General and Special Senses
Learning Outcomes
Compare and contrast the types of general sensory receptors.
Describe the anatomy of the olfactory receptors and the olfactory pathway connecting these receptors to the cerebral cortex.
Describe the anatomy of the taste receptors and the pathway connecting these receptors to the cerebral cortex.
Describe the anatomy of the external ear, middle ear, and internal ear.
Describe the anatomy of the eye.
Classification of Receptors by Stimulus Type
Mechanoreceptors: Respond to mechanical forces.
Types of stimuli include:
Touch
Pressure
Stretch
Vibration
Itch
Baroreceptors: Specifically monitor blood pressure.
Thermoreceptors: Respond to changes in temperature.
Chemoreceptors:
Respond to chemical substances that mediate the senses of taste and smell.
Photoreceptors:
Respond to light.
Location: Found in the eye.
Nociceptors:
Respond to harmful stimuli, which often result in pain.
Classification of Receptors by Structure
General somatosensory receptors:
Divided into two major groups:
Free nerve endings (Non-encapsulated):
Respond to pain and temperature stimuli.
Encapsulated nerve endings:
Mechanoreceptors enclosed in connective tissue, sensitive to:
Touch
Pressure
Vibration
Proprioception
General Sensory Receptors Classified by Structure and Function (1 of 3)
Free Nerve Endings:
Functional Class:
According to Location: Exteroceptors, interoceptors, and proprioceptors.
According to Stimulus Type: Nociceptors (pain), thermoreceptors (heat and cold), mechanoreceptors (pressure), chemoreceptors.
Body Location:
Most body tissues; particularly dense in connective tissues (ligaments, tendons, dermis, joint capsules, periosteum) and epithelia (epidermis, cornea, mucosae, glands).
Modified free nerve endings:
Epithelial tactile complexes (Merkel discs).
Hair Follicle Receptors:
Tactile cells in and surrounding hair follicles.
General Sensory Receptors Classified by Structure and Function (2 of 3)
Encapsulated Receptors:
Tactile (Meissner's) corpuscles:
Location: Dermal papillae of hairless skin (nipples, external genitalia, fingertips, eyelids).
Functional Class: Exteroceptors, mechanoreceptors (light pressure, discriminative touch, vibration of low frequency), rapidly adapting.
Lamellar (Pacinian) corpuscles:
Location: Dermis and hypodermis; abundant in fingers, soles of feet, external genitalia, nipples.
Functional Class: Exteroceptors, interoceptors, some proprioceptors; mechanoreceptors (deep pressure, stretch, vibration of high frequency), rapidly adapting.
Bulbous corpuscle (Ruffini endings):
Location: Deep in dermis, hypodermis, and joint capsules.
Functional Class: Exteroceptors, proprioceptors; mechanoreceptors (deep pressure and stretch), slowly adapting or nonadapting.
Visceral Sensory
Visceral Pain:
Characteristics: Dull and poorly localized.
Causes: Results from chemical irritation or inflammation rather than cutting of the organs.
Referred Pain:
Phenomenon where visceral pain is perceived in regions of the body with the same somatic origin.
Taste—Gustation
Taste Receptors:
Occur in taste buds mainly located on the surface of the tongue, within tongue papillae.
Five Basic Qualities of Taste:
Sweet
Sour
Salty
Bitter
Umami (elicited by glutamate).
Smell (Olfaction)
Olfactory Receptors:
Located in the olfactory epithelium.
Olfactory Cilia:
Act as receptive structures for smell.
Neural Pathway:
Axons of olfactory sensory neurons penetrate the cribriform plate of the ethmoid bone, enter the olfactory bulbs, and synapse with mitral cells.
Mitral cells transmit impulses along the olfactory tract to the primary olfactory cortex in the temporal lobe.
The Eye and Vision
Vision:
Dominant sense in humans.
70% of all sensory receptors are found in the eyes.
40% of the cerebral cortex processes visual information.
Accessory Structures of the Eye (1 of 2)
Eyebrows:
Coarse hairs on the superciliary arches that help direct sounds.
Eyelids (Palpebrae):
Separated by the palpebral fissure.
Tarsal Plates:
Connective tissue within the eyelids.
Tarsal Glands:
Modified sebaceous glands.
Conjunctiva:
Transparent mucous membrane that lines the eyelids and covers the anterior surface of the eyeball, excluding the cornea.