Sensory Physiology Flashcards by Ron Esquillo

An Afferent System that provides info to CNS about the state of body and/or the immediate environment

Sensation

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Starting point of Afferent System; Specialized epithelial cells or neurons that transduce environmental signals into neural signals

Sensory Receptors

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End point of Afferent System

Sensory Cortex

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Change in membrane potential produced by the stimulus; Trigger action potential trains

Generator Potential/Receptor Potential

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Touch Receptors

Mechanoreceptors

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Temperature Receptors

Thermoreceptors

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Pain Receptors

Nociceptors

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Light Receptors

Electromagnetic Receptors

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O2 or CO2 Receptors

Chemoreceptors

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“Specific sensation, specific receptors”

Differential Sensitivity

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“Specific sensations, specific pathways”

Labeled Line Principle

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Change in a way a receptor responds to sequential or prolonged stimulation

Adaptation

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For continuous stimulus strength; Detects steady stimulus (eg: muscle spindle, golgi tendon, slow pain receptor, baroreceptor, chemoreceptor)

Slowly-adapting Receptors (Tonic Receptors)

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For detecting change in stimulus strength; Detects onset and offset of stimulus; Has predictive function (eg: Pacinian corpuscle)

Rapidly-adapting Receptors (Phasic Receptors)

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Region of skin where stimuli can change the firing rate of sensory neurons

Receptive Field

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Smaller receptive field with well-defined border

Type 1 Receptive Field

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Wider receptive field with poorly-defined borders

Type 2 Receptive Field

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Tactile Receptor: In the skin; For Touch and Pressure

Free Nerve Endings

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Tactile Receptor: In non-hairy skin (eg: fingertips and lips); For Movement of objects and low-frequency vibration

Meissner’s Corpuscles (FA1)

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Tactile Receptor: Combine to form Iggo Dome Receptors; Expanded tip Tactile Receptor; Gives steady-state signals for continuous touch; Localizing touch sensation and to determine texture

Merkel’s Disc (SA1)

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Tactile Receptor: In hair base; For Movement of objects on the skin

Hair-end organ

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Tactile Receptor: In deep skin, internal tissues and joint capsules; Multi-branched, encapsulated; Slow-adapting; Heavy and prolonged touch (pressure) and to signal degree of joint rotation

Ruffini’s end organs (SA2)

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Tactile Receptor: Onion-like structure in skin and deep fascia; Detects high frequency vibration

Pacinian Corpuscles (FA2)

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Cell Body: Dorsal Root or Cranial Nerve Ganglia

First-Order Neurons

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Cell Body: Spinal Cord or Brainstem

Second-Order Neurons

Cell Body: Thalamus

Third-Order Neurons

Cell Body: Sensory Cortex

Fourth-Order Neurons

Somatosensory pathway that uses large myelinated fibers (Group II); 30-110m/s; With temporal & spatial fidelity; Crosses near the medulla; Vibration, sensations against the skin, position sense & fine pressure, 2-point discrimination

Dorsal Column-Medial Lemniscus Pathway

Somatosensory pathway that uses smaller myelinated fibers (Group III & IV); 8-40m/s; With less fidelity; Less accurate gradations; Crosses immediately; Pain, temperature sensation, crude touch & pressure sensation, tickle and itch sensation; sexual sensation

Antero-Lateral System (Spinothalamic Tract)

Relay station for sensation

Thalamus

Dorsal Column-Medial Lemniscus

VPL Nuclei

Trigemino Thalamic Pathway

VPM Nuclei

Anterolateral System

VPI Nuclei

Somatotropic organization of Primary (S1) & Secondary (S2) Somatosensory Area; Largest area are for the fingers, hands & face for precise localization

Sensory Homunculus

Neurotransmitters for Pain

GlutamateSubstance P

Type of Pain: after 0.1 sec; aka 1st/sharp/pricking/acute/electric pain; Superficial; Stimulated: mechanical or thermal stimuli; Type A-delta fibers; NT: Glutamate

Fast Pain

Type of Pain: after 1 sec; aka 2nd/slow/burning/aching/throbbing/nauseous/chronic pain; Associated with tissue destruction; Stimulated: mechanical or thermal or chemical stimuli; Type C fibers; NT: Substance P

Slow Pain

Due to sharing of 2nd Order neurons in the spinal cord of Visceral pain fibers & Skin pain fibers; Follows Dermatome Rule

Referred Pain

Pain Killer System of the body; NT: Serotonin, Epinephrine, Norepinephrine

Endogenous Analgesia System

Thermal Receptors: Free nerve endings & Type C fibers

Warmth Receptors

Thermal Receptors: Type A-delta fibers & some Type C

Cold Receptors

Thermal Receptors: For Temperature 43 deg C

Pain Receptors

Detects and interprets electromagnetic waves between 400-750nm long; Can detect brightness (luminance) and wavelength (color)

The Visual System

Light from a visual target is focused sharply on the retina by the cornea and lens by refracting/bending light

Vision

Ability to bend light; Measured in Diopters (Reciprocal of focal distance in meters)

Refractive Power

Refractive Power of the Eye

59 Diopters (2/3 by Cornea & 1/3 by Lens)

Ciliary muscles: Relaxed; Lens: Flat

Increased tension from Suspensory Ligaments

Ciliary muscles: Contracted; Lens: Spherical

Decreased tension from Suspensory Ligaments

Automatic adjustment in the focal length of the lens of the eye to permit retinal focus of image of objects at varying distances; Provides an additional 14 Diopters for the lens

Accommodation

Maintains shape of the eye

Intraocular Fluid

Produced by ciliary body; Exits into Canal of Schlemm; Free-flowing; Main determinant of IOP

Aqueous Humor

Gelatinous with little flow

Vitreous Humor

Light sensitive portion of the eye which contains photoreceptors Rods and Cones (Light causes Hyperpolarization of the photoreceptors)

Retina

Area of Central vision with slight thickening and pale color

Macula Lutea

Depression in macula lutea with the highest visual resolution (highest cone density) where image from fixation point is focused

Fovea

Anatomic Blind Spot; Lacks Photoreceptors

Optic Disc

What do you call the protrusion of the optic disc into the vitreous space due to increased ICP?

Papilledema

Absorb stray light and preventing light from scattering

Pigment epithelium

Deterioration of Pigment epithelium

Macular Degeneration

Pigment epithelium lacks melanin

Albinism

Absent in Optic Disc

Rods and Cones

Interneuron that connects Rods and Cones with Ganglion Cells; Contrast Detectors

Bipolar cells

Interneurons that form local circuits with bipolar cells

Amacrine Cells, Horizontal Cells

Retinal Glial Cell; Maintains internal geometry of the retina; Ganglion Cell; Its axon form the Optic Nerve

Mueller Cells

Output Cells of Retina: For color, form, fine details

P Cells

Output Cells of Retina: For illumination and movement

M Cells

Output Cells of Retina: With unknown function

W Cells

For Night Vision; Narrower & Longer; Contains 1 Type of Photopigment (Rhodopsin); Greater amount of photopigment, better signal amplification, more numerous; 30-300x more sensitive; Adapts 4x less rapidly but can last for minutes to hours; Lower visual acuity; Not present in Fovea

Rods

For Daylight Vision; Wider & Shorter; Contains 3 types of color photochemicals (blue, green, red); Less amount of photopigment, less signal amplification, less numerous; 30-300x less sensitive; Adapts 4x more rapidly but only for a dew seconds; Higher visual acuity; Present in Fovea

Cones

Changes in concentration of Rhodopsin (reduced) and Photochemicals: Sudden brightness; Reduced photosensitivity

Light Adaptation

Changes in concentration of Rhodopsin and Photochemicals: Sudden darkness; Rods adapt slowly but increased photosensitivity

Dark Adaptation

Light rays converge in front of the retina (long eyeball)

Myopia (Biconcave Lens)

Light rays converge behind of the retina (short eyeball)

Hyperopia (Convex Lens)

Irregular curvature of the cornea

Astigmatism (Cylindrical Lens)

Age-related loss of Accommodation

Presbyopia (Convex Lens)

1st sign of Vit 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; Speed: 335m/sec in air

Sound

Measured in cycles per second or Hertz (Hz)

Sound Frequency

Measured in Decibels (dB)

Sound Pressure

How many cycles/second can a human ear detect?

20-20,000 cycles/second (depends on loudness)

More damaging to the Organ of Corti

Low-frequency sounds

What is the age-related progressive sensorineural hearing loss?

Presbycusis

Occupational Hearing Loss (OHL) occurs after >10 years exposure to which sound pressure?

>85 Decibels

What sound pressure will cause pain and possible permanent damage?

>120 Decibels

What is the function of the pinna?

Sound Localization

What are the 2 muscles found in the middle ear?

Tensor Tympani (Malleus)Stapedius (Stapes)

What is the connection between outer & middle ear?

Eustachian Tube (Equalizes pressure differences)

What is the function of the middle ear?

Impedance Matching

What is the function of the attenutation refle?

Protects cochlea from loud (damaging) sounds; Masks background noise

What is the function of the basilar membrane?

Frequency analyzer: distributes stimulus along the Organ of Corti according to frequency

Vestibular Apparatus: Utricle & Saccule; Uses Macule as sensory organ (has Stataconia & Hair cells); Detects head orientation with respect to gravity; For linear acceleration & sometimes angular acceleration

Otolith Organs

Vestibular Apparatus: Anterior, Posterior, Lateral Canals; Uses Crista Ampullaris with Cupula and Hair cells; Detects changes in the rate an direction of rotation of the head; For angular acceleration alone; Also has a predictive function in the maintenance of equilibrium

Semicircular Canals

Number of Taste Receptors (Chemoreceptors) Cells

50-150 (Lasts 10 days and continuously replaced) NOT true neurons

Found on the Anterior and Lateral Part of the Tongue

Fungiform & Foliate papillae

Found on the base of the Tongue

Circumvallate papillae

Proteinaceous meaty flavor cause by MSG

Umami

More sensitive than other tastes; Caused by organic substances like Quinine

Bitter Taste

Number of Olfactory Chemoreceptors

10 million (Lasts for 60 days, continuously replaced) TRUE Neurons

Uses unmyelinated Type C fibers; No relay station in the Thalamus

Smell

At the superior part of the nostril; Also innervated by CN V that detects noxious/painful stimuli

Olfactory membrane