Chapter 6: The Peripheral Nervous System: Afferent Division; Special Senses Flashcards
1
Q
Stimulus
A
- change detectable by the body
- afferent neurons have sensory receptors at their peripheral endings
- responds to stimuli in both the external world and the internal environment
- stimuli bring about receptor potentials in the receptor
- sensory transduction
2
Q
Types of receptors
A
- photoreceptors
- mechanoreceptors
- thermoreceptors
- osmoreceptors
- chemoreceptors
- nociceptors
3
Q
Receptor Potential
A
- stimulus alters the receptor’s permeability
- receptor potentials may initiate action potentials in the afferent neuron
- large receptor potential triggers opening of voltage-gated Na+ channels
4
Q
Types of receptors according to their speed of adaption
A
- tonic and phasic receptors
5
Q
Tactile Receptors
A
- mechanoreceptors
- hair receptors, Merkel’s disc, Pacinian corpuscle, Ruffini endings, and Meissner’s corpuscle
- mechanism of adaption in Pacinian corpuscle
- receptor ending consisting of concentric layers of connective tissue wrapped around the peripheral terminal of an afferent neuron
6
Q
Somatosensory Pathways
A
- visceral afferents carry subconscious input
- sensory afferents carry conscious input
- each somatosensory pathway is labelled according to modality and location
Labelled Lines: first-order, second-order, and third-order sensory neurons
Phantom Pain: may arise from extensive remodeling of the brain region that originally handled sensation
7
Q
Acuity and Perception
A
Acuity: influenced by receptive field size and lateral inhibition
Receptive Field- region of the skin surface surrounding the somesthetic sensory neuron
Lateral inhibition- each activated signal pathway inhibits the pathways next to it
Perception: conscious awareness of surroundings
- derived from interpretation of sensory input
8
Q
Pain
A
- primarily a protective mechanism triggered on stimulation of danger-sensing nociceptors
- brings to conscious awareness tissue damage that is occurring or about to occur
- storage of painful experiences in memory helps us avoid potentially harmful events in the future
9
Q
Pain and Nociceptors
A
- stimulation of nociceptors elicits the perception of pain, and motivational and emotional responses
- categories of pain receptors: mechanical, thermal, and polymodal
- fast and slow afferent pain fibers: delta fibers and C fibers
- higher-level processing of pain input: substance P and glutamate
10
Q
The brain has a build-in analgesic system
A
- suppress transmission in the pain pathways as they enter the spinal cord
- endorphins released during exercise
- stress-induced analgesia
- acupuncture analgesia
11
Q
Eye: Vision
A
- eyes capture patterns of illumination in the environment as an optical picture on a layer of light-sensitive cells, the retina
- coded image on the retina is transmitted through the steps of visual processing until it is finally consciously perceived
12
Q
Eye: Protective Mechanisms and Layers
A
- protective mechanisms help prevent eye injuries
- eyelids and eyelashes
- tears and lacrimal gland
- the eye is a fluid-filled sphere enclosed by three specialized tissue layers
- sclera/cornea
- choroid/ciliary body/iris
- retina
13
Q
Eye: processing Light
A
- the amount of light entering the eyes is controlled by the iris
- thin, pigmented, smooth muscle
- form a visible ringlike structure within the aqueous humor
- the eye refracts entering light to focus the image on the retina
- process of refraction
- the eye’s refractive structures
14
Q
Eye: Accomodation
A
- increases the strength of the lens for near vision
- strength of the lens depends on its shape
- regulated by the ciliary muscle
- light must pass through several retinal layers before reaching the photoreceptors
15
Q
Eye: Phototransduction
A
- by retinal cells converts light stimuli into neural signals
- photoreceptors consists of an outer/inner segment and synaptic terminal
- rod and cone cells
16
Q
Eye: Rods and Cone
A
- rods provide indistinct gray vision at night
- cones provide sharp color vision during the day
- rods have high sensitivity; cones have lower sensitivity
- cone vision has high acuity; rod vision has low acuity
- cones provide color vision; rods provide vision in shades of gray
17
Q
Eye: Color and Adaption
A
- color vision depends on the ratios of stimulation of the three cone types
- each cone type is most effectively activated by a particular wavelength of light in the range of color indicated by its name
- trichromatic theory and opponent-process theory
- the sensitivity of the eyes can vary markedly through dark and light adaption
18
Q
Eye: Visual Information Processing
A
- visual information is modified and separated before reaching the visual cortex
Visual Field: field of view that can be seen without moving the head - the thalamus and visual cortex elaborate the visual message
- depth perception
-hierarchy of visual cortical processing
19
Q
Eye: Other Sensory Processing
A
- visual input goes to other areas of the brain not involved in vision perception
- non-sight activities depend on input from the rods and cones
- some sensory input may be detected by multiple sensory-processing areas in the brain
- brain regions devoted almost exclusively to a certain sense actually receive a variety of sensory signals
20
Q
Ear: Hearing and Equilibrium
A
- ear consists of 3 parts
- external, the middle, and inner ear
- sound waves consist of alternate regions of compression and rarefaction of air molecules
Hearing: neural perception of sound energy
Sound Waves: traveling vibrations of hair
Sound Characteristics: pitch (tone), intensity (loudness), and timbre (quality)
21
Q
Ear: External Ear
A
- plays a role in sound localization
- consists of the pinna (ear), external auditory meatus (ear canal), and tympanic membrane (eardrum)
- tympanic membrane vibrated in unison with sound waves in the external ear
- stretched across the entrance to the middle
- vibrates when struck by sound waves
22
Q
Ear: Middle Ear
A
- middle ear bones convert tympanic membrane vibrations into fluid movements in the inner ear
- facilitated by a moveable chain of three small bones, or ossicles
Malleus
Incus
Stapes
23
Q
Ear: Cochlea and Organ of Corti
A
- contains the organ of corti, the sense organ for hearing
Cochlea: pea-sized, snail-shaped, hearing portion of the inner ear - hair cells in the organ of the corti transduce fluid movements into neural signals
- role of the inner/outer hair cells
24
Q
Ear: Discrimination
A
- pitch discrimination depends on the region of the basilar membrane that vibrates
- ability to distinguish among various frequencies of incoming sound waves
- loudness discrimination
- depends on the amplitude of vibration
- the auditory cortex is mapped according to tone
- tonotopically organized
25
Q
Ear: Loss of Hearing and Equilibrium
A
- deafness is caused by defect in either conduction or neural processing of sound waves
- loss of hearing
- the vestibular apparatus is important for equilibrium by detecting head position and motion
- role of the semicircular canals and the otolith organs
26
Q
Chemical Senses: Taste and Smell
A
Chemoreceptors: receptors for taste and smell
- generate neural signals on binding with particular chemicals in their environment
Sensations of taste and smell associated with food intake
- influence flow of digestive juices and affect appetite
- induces pleasurable or objectionable sensations: seek or avoid
27
Q
Chemical Senses: Taste
A
- taste receptor cells are located primarily within tongue taste buds
- bud consists of about 50 long, spindle-shaped taste receptor cells
- packaged with supporting cells in an arrangement like slices of an orange
- taste discrimination is coded by patterns of activity in various taste bud receptors
- salty, sour, sweet, bitter, and umami tastes
28
Q
Chemical Senses: Other Areas of Taste
A
- the gut and airways taste
- cells in the stomach and intestine have same GPCRs and gustducin-activated pathways for tasting
- the olfactory receptors in the nose are specialized endings of renewable afferent neurons
- olfactory receptor cells, supporting cells, and basal cells
29
Q
Chemical Senses: Smell
A
- various parts of an odor are detected by different olfactory receptors and sorted into smell files
- separate components of an odor are sorted into different glomeruli
- one component per file
- odor discrimination is coded by patterns of activity in the olfactory bulb glomeruli
- each odorant activates multiple receptors and glomeruli in response to odor components
30
Q
Chemical Senses: Adaptation
A
- olfactory system adapts quickly and odorants are rapidly cleared
- sensitive, highly discriminating and quickly adaptive
- the vomeronasal organ detects pheromones
- nonvolatile chemical signals passed subconsciously between individuals of the same species
31
Q
On a very hot day in July, you buy a nice, cold canned diet drink containing an artificial sweetener. Upon drinking the beverage you experience a bitter taste instead of the normal sweet taste. How would you explain this?
A
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32
Q
A patient complains of severe dizziness when riding the elevator to her job on the 15th floor. Explain how she could solve this problem without walking up the stairs.
A
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