Sensory Physiology Flashcards
What do sensory receptors do?
They are transducers: they sense a change in environment and convert it to action potential to relay to the nervous system
What is a modality?
The form information takes
Why are modalities perceived as different from one another?
Because of the CNS pathway they take
What are the different receptors (as classified by stimulus type)?
Chemoreceptors - Chemical
Photoreceptors - Light
Mechanoreceptors - Heat
Nocireceptors - Pain
Propioceptor - Balance & Position
What are the cutaneous/somatic receptors?
Touch & Pressure
-Merkel’s discs in stratum basale: sustained pressure
-Ruffini corpuscles - sustained pressure
-Meissner’s corpuscles - changes in texture, slow vibrations
-Pacinian Corpsucles - Deep pressure, fast vibrations
Heat (Cold in upper, warm in lower)
Pain
What are tonic receptors?
Sensors that respond at a constant rate as long as stimulus is being applied
What are phasic receptors?
Receptors that respond with a burst of AP but quickly stop as they adapt
Ex. Smell, Light touch (clothes on body)
What is sensation?
The state of awareness of an internal or external condition
What is perception?
Conscious recognition of a sensation
What is sensory modality?
The quality or distinct property of a sensation (we have more then 20)
Are we conscious of all sensory modalities?
No, some are unconscious, such as those in the stomach
What is an adequate stimulus?
The type of stimulus to which as receptor is most sensitive
What is the law of specific nerve energies?
The sensation perceived when a receptor responds is always the same, regardless of strength or type
True or False: The stimulation of a sensory fiber evokes only the sensation of its modality
True
True or false: Stimulation of sensory fibers requires no energy.
False. This is why different kinds if energy can activate sensory neurons that don’t respond to that stimulus (ie why getting punched in the eye makes you see light)
True or False: The sensors on a body correspond to that side of the body
False. The left side of the body goes to the right side of the brain and vice versa
Where is the somatosensory pathway for touch and proprioception?
The dorsal columns of the spinal cord
Where are the somatosensory pathways for pain and temperature?
The lateral spinothalmic tract
What increases the sensitivity of receptive fields in the skin?
The density of receptors: the more endings closer together, the more sensitive
What is 2-point discrimination?
If the distance between two points is on the same receptive field it will not be perceived as 2 points
What is tactile acuity?
The minimum distance at which two points can be perceived as separate
What is the olfactory pathway?
Receptor cells synapse with secondary cells in the olfactory bulb called mitral cells, which Amplify, Refine, and Relay to olfactory cortex, hypothalamus, amygdala, and limbic sysem
What kind of messenger system does the olfactory pathway use?
Secondary Messenger System:
Oderants bind to 1 of 350 specific receptors, then cilia in the nasal cavity communicates to receptor neurons
Which sensation is the only one that skips the thalamus and goes directly to its cortex?
Olfactory
What are the receptors in gustation?
Sweet
Sour (H+)
Salty (Na+)
Bitter
Unami (amino acids)
What do we call a modified epithelial cell covered with microvilli?
A taste bud
True or False - Each taste bud responds to one type of taste
False - Each bud responds to all categories of tastants
Which two tastants do not have membrane receptors?
Salty and Sour
What is the 3 Order Sensory Neuron Pathway?
1st Order - Vagus, Facial, and Glossopharugeal nerves all carry sensation to the medulla oblangata
2nd order go to the thalamic nucleus
3rd order go to the sensory cortex
What are the three tunics if the eye?
Exterior - The fibrous (sclera and cornea)
Middle - The vascular (cilliary body)
Interior - The sensory (retina)
What is the path of light?
Cornea to Anterior Chamber if Aqueous Humor past the iris through the pupil through the lens to the posterior chamber of vitreous humor and onto the retina
How does the ANS regulate pupil size?
The Sympathetic controls radial fibers, which dilate the pupil
The Parasympthetic controls circular fibers, which constrict the pupil
What does the ciliary body do?
It supports the lens with suspensory ligaments and constricts or relaxes to control the shape of the lens.
It secretes aqueous humor
What happens as aqueous humor circulates in the eye? What happens if this stops?
It is secreted into posterior chamber, circulates to anterior chamber, and is drained through the canal of Schlemm.
If drainage is blocked it causes an increase in pressure called glaucoma
What is refraction?
The change in direction of a wave passing from one medium to another
What is accommodation?
The “plumping up” of a lens during vision.
When the ciliary muscles tense the lens becomes more convex
What 3 adjustments happen to our eyes during close vision and what muscles control these adjustments?
Accommodation - The ciliary body
Constriction if the Pupil - Circular fibers of iris
Convergence - Medial rectus of the eyes
Why do we lose visual acuity as we age?
The dilator muscles become less efficient, this condition is called Presbyopia
What is emmetropia?
Normal vision
What is used to test for sharpness of vision aka visual acuity?
The Snellen eye chart
What is the most common form of color blindness? Why?
RG Colorblindness. It is most common in males because red and green cones are carried on the X chromosome and males only inherit one from their mothers, while females inherit one from each parent
What is hyperopia?
Far-sightedness - rays focus behind the retina, corrected with a convex lens
What’s myopia?
Near-sightedness - rays focus in front of the retina, a concave lens to correct
What is an astigmatism?
Tays do not focus do to an uneven curvature of the lens
What is the the organization of the retina?
Photoreceptor cones on the macula lutea
Light is focused on the fovea centralis
Axons of neurons gather at optic disc
-This creates a blind spot, which the brain accommodates for
The choroid is a dark layer behind the retina
How do visual pigments respond to light?
Light hits the retina and passes through ganglion cells
Piloral celles send info to bipolar cells, which send info to occipital lobe
What is the difference between retinal, opsin, and rhodopsin?
Retinal is a light-absorbing molecule that combines with opsin (synthesized from Vitamin A) to form visual pigments called Rhodopsin in rod cells
Explain the cis/trans isomer distinction of retinal
When light shines onto pigment molecules rhodopsin changes cis isomers to trans isomers
Trans retinal uses g protein to cayse a chain reaction closing gated channels and the cell hyperpolarizes
When light goes dark enzymes slowly covert all the trans retinal back to cis retinal
How do we perceive color?
RBG cone cells