VII - Sensory Physiology Flashcards
Provides information to the CNS about the state of the body and/or the immediate environment
Sensation
Specialized epithelial cells or neurons that transduce environmental signals into neural signals
Sensory Receptors
Change in membrane potential produced by the stimulus, triggers action potential trains
Generator/Receptor Potential
Specific sensations, specific receptors
Differential Sensitivity
Specific sensations, specific pathways
Labeled Line Principle
Change in a way a receptor responds to sequential or prolonged stimulation
Adaptation
Slowly-adapting, for continuous stimulus strength, detects steady stimulus
Tonic Receptors
Rapidly-adapting, for detecting change in stimulus strength, detects onset and offset of stimulus, predictive function
Phasic Receptors
Region of the skin where stimuli can change the firing rate of the sensory neurons
Receptive Field
Receptive Field: Smaller with well-defined borders
Type 1
Receptive Field: Wider with poorly-defined borders
Type 2
Free Nerve Endings: Location
skin
Free Nerve Endings: Sensation
touch, pressure, pain
Meissner’s Corpuscles (FA1): Location
non-hairy/glabrous skin. fingertips, lips
Meissner’s Corpuscles (FA1): Sensation
movement of objects, low-frequency vibration
Expanded tip tactile receptor, combine to form Iggo Dome Receptors
Merkel’s Disk (SA1)
Merkel’s Disk (SA1): Sensation
steady-state signals for continuous touch, localizing touch, texture
Hair-end Organ: Location
hair base
Hair-end Organ: Sensation
movement of object
Multi-branched, encapsulated, slowly-adapting receptors
Ruffini’s End Organs (SA2)
Ruffini’s End Organs (SA2): Location
deep skin, internal tissues, joint capsules
Ruffini’s End Organs (SA2): Sensation
heavy, prolonged touch (pressure), degree of joint rotation
Onion-like receptors
Pacinian Corpuscles (FA2)
Pacinian Corpuscles (FA2): Location
skin, deep fasia
Pacinian Corpuscles (FA2): Sensation
high-frequency vibration
Transduces stimulus to electrical signal
Sensory Receptors
Sensory Pathway: Dorsal root or cranial nerve ganglia
First-Order Neurons
Sensory Pathway: Spinal cord or brainstem
Second-Order Neurons
Sensory Pathway: Thalamus
Third-Order Neurons
Sensory Pathway: Sensory cortex
Fourth-Order Neurons
Sensory Pathway: First-Order Neurons
dorsal root or cranial nerve ganglia
Sensory Pathway: Second-Order Neurons
spinal cord or brainstem
Sensory Pathway: Third-Order Neurons
thalamus
Sensory Pathway: Fourth-Order Neurons
sensory cortex
Somatosensory Pathways: Large myelinated fibers (group II), conduction velocity 30-110 m/s
Dorsal Column-Medial Lemniscus Pathway
Somatosensory Pathways: With temporal and spatial fidelity
Dorsal Column-Medial Lemniscus Pathway
Somatosensory Pathways: Crosses near the medulla
Dorsal Column-Medial Lemniscus Pathway
Somatosensory Pathways: Touch sensations requiring high degree of localization and fine gradiation of intensity
Dorsal Column-Medial Lemniscus Pathway
Somatosensory Pathways: Vibration, movement, position sense, fine pressure, two-point discrimination
Dorsal Column-Medial Lemniscus Pathway
Somatosensory Pathways: Smaller myelinated fibers (group III, IV), conduction velocity 8-40 m/s
Antero-Lateral System (Spinothalamic Tract)
Somatosensory Pathways: Less fidelity, less accurate gradiations
Antero-Lateral System (Spinothalamic Tract)
Somatosensory Pathways: Crosses immediately
Antero-Lateral System (Spinothalamic Tract)
Somatosensory Pathways: Pain, temperature, crude touch, pressure, tickle, itch, sexual sensation
Antero-Lateral System (Spinothalamic Tract)
Relay station for sensation except for olfaction
Thalamus
Thalamus: VPL Nuclei
Dorsal Column-Medial Lemniscus
Thalamus: VPN Nuclei
TrigeminoThalamic Pathway
Thalamus: VPI Nuclei
Antero-Lateral System
Somatosensory Cortex: Largest areas for
fingers, hands, face - for precise localization
Associated with detection and perceptions of noxious stimuli
nociception
Pain: Receptors
free-nerve endings in skin, muscle and viscera
Pain: Adaptation
little to none
Pain: Neurotransmitters
glutamate, substance P
Types of Pain: After 0.1 s of stimulus
fast pain
Types of Pain: First, sharp, pricking, acute, alectric
fast pain
Types of Pain: Superficial
fast pain
Types of Pain: Mechanical and thermal stimuli
fast pain
Types of Pain: A-delta fibers (6-30 m/s)
fast pain
Types of Pain: Glutamate
fast pain
Types of Pain: After 1 s of stimulus
slow pain
Types of Pain: Second, slow, burning, aching, throbbing, nauseous, chronic
slow pain
Types of Pain: Tissue destruction
slow pain
Types of Pain: Mechanical, thermal and chemical stimuli
slow pain
Types of Pain: C fibers (0.5-2 m/s)
slow pain
Types of Pain: Substance P
slow pain
Due to sharing of 2nd order neurons in the spinal cord of visceral pain fibers and skin pain fibers
referred pain
Referred pain follows
dermatomes
Opioid-mediated Endogenous Analgesia
Enkephalin, Dynorphine, Beta-Endorphine
Non-Opioid-mediated Endogenous Analgesia
stress
Endogenous Analgesia: Neurotransmitters
Serotonin, Epinephrine, Norepinephrine
The Endogenous Analgesia System blocks the pain signal at its _____ in the _____.
initial point of entry, spinal cord
Stimulated tactile receptors can inhibit pain transmission in the spinal cord.
Lateral Inhibition - rubbing, liniments, acupuncture
Warmth Receptors
free nerve endings, C fibers
Cold Receptors
A-delta fibers, some C fibers
Temp for Pain Receptors
< 15°C or > 43°C
The eyes can interpret electromagnetic waves between
400-750 nm
Eye: Outer Layer
fibrous
Eye: Middle Layer
vascular
Eye: Inner Layer
neural
Ability to bend light
Refractive Power
Refractive power is measured in
diopters
Refractive Power: Eye
58 diopters
Refractive Power: Cornea
40 diopters (2/3 of the eye)
Refractive Power: Lens
1/3 of the eye, variable
When ciliary muscles are relaxed, there is _____ tension from suspensory ligaments and the lens becomes _____.
increased tension, flat - for distant objects
When ciliary muscles are contracted, there is _____ tension from suspensory ligaments and the lens becomes _____.
decreased tension, spherical - for nearby objects
Automatic adjustment in the focal length of the lens to permit retinal focus of images at varying distances
accomodation
Accomodation provides an additional __ diopters for the lens.
14 diopters
Maintains the shape of the eye
intraocular fluid
Watery intraocular fluid, produced by ciliary bodies, free-flowing, main determinant of IOP
aqueous humor
Gelatinous intraocular fluid with little flow
vitreous humor
Flow of Aqueous humor
ciliary body → posterior chamber → pupil → anterior chamber → trabecular meshwork → anterior chamber angle → canal of Schlemm → uveoscleral veins
Light-sensitive portion of the eye which contains the photoreceptors
retina
Light causes _____ of the photoreceptors.
hyperpolarization
Retina: Area of central vision with slight thickening and pale color
macula lutea
Retina: Depression in the macula with the highest visual resolution (highest cone density)
fovea
Retina: Where image from fixation point is focused
fovea
Retina: Lacks photoreceptors (anatomic blind spot)
optic disk
Retina: Last part of the optic nerve
papilledema
Retina: Absorbs stray light preventing light from scattering
pigment epithelium
Degradation of pigment epithelium
Macular Degeneration
Pigment epithelium lacks melanin in
Albinism
Rods and cones are absent in the
optic disk
Retina: Interneuron that connects rods and cones with ganglion cells
bipolar cells
Retina: Contrast Detectors
bipolar cells
Retina: Interneurons that form local circuits with bipolar cells
amacrine/horizontal cells
Retina: Glial cells, maitains geometry of the retina
Mueller cells
Retina: Output cells, initiates action potential, axons form optic nerve
ganglion cells
Ganglion Cells of the Retina: Color, form, fine details
P cells
Ganglion Cells of the Retina: Illumination, movement
M cells
Ganglion Cells of the Retina: Uknown function
W cells
Photoreceptors: Night
rods
Photoreceptors: Narrower, longer
rods
Photoreceptors: 1 type of photopigment - Rhodopsin
rods
Photoreceptors: Greater amount of photopigment, better signal amplification, more numerous
rods
Photoreceptors: 30-300x more sensitive
rods
Photoreceptors: Adapts 4x slower but can last for minutes to hours
rods
Photoreceptors: Lower visual acuity
rods
Photoreceptors: Not present in the fovea
rods
Photoreceptors: Daylight
cones
Photoreceptors: Wider, shorter
cones
Photoreceptors: Contains 3 photochemicals (blue, red green)
cones
Photoreceptors: Less amount of photopigment, less signal amplification, fewer in number
cones
Photoreceptors: Adapts 4x faster but only lasts for a few seconds
cones
Photoreceptors: Higher visual acuity
cones
Photoreceptors: Abundant in the fovea
cones
Light rays converge in front of the retina (long eyeball)
myopia - biconcave lenses
Light rays converge behind the retina (short eyeball)
hyperopia - convex lenses
Irregular curvature of the cornea
astigmatism - cylindrical lenses
Age-related loss of accomodatin
presbyopia - convex lenses
First sign of vitamin A deficiency
nyctalopia
Ptosis, meiosis, anhydrosis
Horner’s Syndrome
Produced by compression and decompression waves transmitted in air or other elastic media such as water
Sound
Sound: Speed
335 m/s in air
Sound: Frequency
Hertz (Hz) - pitch
Sound: Pressure
Decibel (dB) - volume
Unwanted sound
Noise
The human ear can detect _____ cycles per second but this also depends on loudness.
20-20,000 cycles per second
___-frequency sounds are more damaging to the Organ of Corti.
Low-frequency
Each unit increase in decibels is ___ louder
1.26 x
The higher the loudness, the _____ the frequency that we can hear.
higher
Age-related progressive sensorineural hearing loss
presbycusis
Occupational hearing loss occurs after > 10 years of exposure to ___ dB.
> 85 dB
What sound pressure will cause pain and possible permanent damage?
> 120 dB
External structure that allows sound localization and colection
pinna
Outer Ear
pinna, external acoustic meatus/auditory canal
The auditory ossicles add ___ dB.
+30-40 dB
Auditory Ossicles
malleus, incus, stapes
he stapes inserts into to ___ window.
oval window
Middle Ear
tympanic membrane, auditory ossicles
The middle ear converts low pressure, high displacement vibrations in the air into high pressure, low displacement vibrations suitable for driving cochlear fluids.
Impedance Matching
Inner Ear: Bony Labyrinth
semicircular canals, cochlea, vestibule
The cochlea subtracts ___ dB.
-30-40 dB
Inner Ear: Series of ducts
membranous labyrinth
Inner Ear: Scala media, high in __
endolymph (ICF), K
Inner Ear: Scala vestibuli and scala tympani, high in __
perilymph (ECF), Na
Two muscles found in the ear
tensor tympani - malleus, stapedius - stapes
Cennection between the outer & middle ear
Eustachian Tube - equalizes pressure differences
The base of the cochlea detects ___ frequencies.
higher
The apex of the cochlea detects ___ frequencies.
lower
Protects the cochlea from loud (damaging) sounds, masks background noise
Attenuation Reflex
Frequency analyzer, distributes stimulus along the Organ of Corti according to frequency
basilar membrane
Vestibular Apparatus: Utricle & Saccule
Otolith Organs
Vestibular Apparatus: Uses macula as its sensory organ, has stataconia and hair cells
Otolith Organs
Vestibular Apparatus: Detects head orientation with respect to gravity
Otolith Organs
Vestibular Apparatus: For linear acceleration and sometime angular acceleration
Otolith Organs
Vestibular Apparatus: Anterior, Posterior & Lateral canals
Semicircular Canals
Vestibular Apparatus: Uses crista ampullaris with cupula and hair cells
Semicircular Canals
Vestibular Apparatus: Detects changes in the rate and direction of rotation of the head
Semicircular Canals
Vestibular Apparatus: For angular acceleration alone, also has a predictive function in the maintenance of equilibrium
Semicircular Canals
Contributors to Taste
taste buds, smell, texture, pain receptors (pepper)
The tongue has _____ chemoreceptor cells.
50-150 taste buds
Taste buds last for __ days, are _____ replenished and are ___ neurons.
10 days, continuouslt replenished, not true neurons
Taste: Caused by various organic chemicals like sugars (mainly sucrose), glycols and amides
sweet
Taste: Caused by ionized salts (mainly Na)
salty
Taste: Caused by acids like HCl (directly proportional to amount)
sour
Taste: Proteinaceous meaty flavor from MSG (glutamate)
umami
Taste: Caused by organic substances like quinine (alkaloid) and long-chain nitrogen containing organic substances
bitter
Taste: Most important for survival, most sensitive
bitter
Detection of the presence of odors
smell
The nose has ___ olfactory chemoreceptors.
10 million
Olfactory chemoreceptors last __ days, are _____ replaced and are ___ neurons.
60 days, continuously replaced, true neurons
Olfactory chemoreceptors use _____ fibers.
unmyelinated C fibers
At the superior part of the nostrils, also innervated by CN V to detect noxious/painful stimuli (ammonia)
olfactory membrane
Olfaction is at the level of the ___.
CNS
Olfaction adaptation happens _____ but be almost _____ when done.
slowly, complete
