Exam 2- Chapter 10 Flashcards
Sensory receptors _____ different forms of energy in the “real world” into nerve impulses.
Transduce
Different sensory perceptions (sound, light, pressure) arise from differences in ___________.
Neural pathways
If the optic nerve delivers an impulse, the brain interprets it as _____.
light
How are the functional categories of sensory receptors categorized?
Categorized according to the type of signal they transduce
What do chemoreceptors sense?
sense chemicals in the environment (taste, smell) or blood
What do photoreceptors sense?
sense light
What do thermoreceptors sense?
respond to cold or heat
What do mechanoreceptors sense?
stimulated by mechanical deformation of the receptor (touch, hearing)
What do nociceptors sense?
pain receptors
What do proprioceptors sense?
muscle stretch
Where do cutaneous receptors deliver information from? What types of senses do they sense?
- Skin
2. Touch, temperature, and pain
What are he special senses?
- Sight
- Hearing
- Equilibrium
- Taste
- Smell
Are phasic receptors fast or slow adapting?
Fast
Are tonic receptors fast or slow adapting?
Slow
The law of specific nerve energies states that, Information from a given nerve fiber can only be experienced as ____ _____ ____.
one stimulus type
According to the law of specific nerve energies, which stimulus will the brain perceive from a nerve fiber?
The sensation produced by the “adequate” or normal stimulus
According to the law of specific nerve energies, a punch to the eye is perceived as what?
Flash of light
What to receptors behave very similar to?
Neurons
In receptors, what is the depolarization produced by stimuli called?
Generator potentials
Provide an example of generator potentials using the pacinian corpuscle in the skin.
- Light touch on a pacinian corpuscle in the skin produces a small generator potential
- Increasing the pressure increases the magnitude of the generator potential until threshold is met and an action potential occurs.
What is the generator potential in tonic receptors proportional to?
Intensity of the stimulus
In a tonic receptor, what does increased intensity of a stimulus result in?
Results in increased frequency of action potential after threshold is reached.
What is the generator potential in phasic receptors related to, and how? Why is this?
- Pressure
- If pressure is maintained, generator potential is diminished
- This is a function of the structure of the receptor
What is the structure of pain, cold, and heat receptors?
Naked dendrites
What is the structure of touch and pressure receptors?
They have special structures around their dendrites
Are there more cold receptors or heat receptors?
Many more cold receptors
Where are cold receptors located?
Close to the epidermis
What are cold receptors stimulated by? Inhibited? Besides these, what do some cold receptors respond to?
- Cold
- Warm
- Menthol
What type of receptors are nociceptors?
Pain
When do nociceptors depolarize?
When tissues are damaged
What can stimuli for nociceptors include?
- Heat
- Cold
- Pressure
- Chemicals
What are the main neurotransmitters for nociceptors?
Glutamate and substance P
What can perceptions of pain be enhanced by?
emotions and expectations
What does pain reduction depend on?
endogenous opioids
Are nociceptors myelinated or unmyelinated?
Can be ether
What kind of neurons transmit sudden, sharp pain?
Myelinated neurons
What kind of neurons transmit dull, persistent pain?
Unmyelinated neurons
Nociceptors may be activated specifically by what?
chemicals released by damaged tissues, such as ATP
What is the pain experienced by a hot stimulus sensed by?
special nociceptor called a capsaicin receptor
What does capsaicin serve as an ion channel for?
Sodium and calcium
What is the receptor for the chemical found in chili peppers?
Capsaicin
What are the names of the different types of cutaneous receptors?
- Free nerve endings
- Merkel’s discs
- Ruffini corpuscles
- Meissner’s corpuscles
- Pacinian corpuscles
What are the names of the different types of touch receptors?
- Meissner’s corpuscles
- Pacinian corpuscles
- Ruffini corpuscles
- Merkel’s discs
Describe the neural pathway for pressure receptors and proprioceptors.
- Carried by large myelinated fibers that ascend the dorsal columns of the spinal cord on the ipsilateral side
- Synapse in the medulla oblongata
- The second tier of neurons cross sides as they ascend the medial lemniscus to the thalamus, where they synapse.
- Third-order neurons go to the postcentral gyrus.
Describe the neural pathway for heat, cold, and pain receptors
- Carried into spinal cord by thin myelinated and unmyelinated neurons
- Synapse within spinal cord onto second-order neuron.
- Cross sides and ascend lateral spinothalamic tract
- Synapse on third-order neurons in thalamus and continue to the postcentral gyrus
What is a receptive field?
The receptive field is the area of skin that, when stimulated, changes the firing rate of a neuron
What does the size of a receptive field depend on?
the density of receptors in that region of skin
There are few receptors in the back and legs so their receptive fields are ________.
Large
There are many receptors in the fingertips, so the receptive fields are _______.
Small
Does a smaller receptive field have greater or lesser tactile acuity?
Greater tactile acuity
How can receptive fields be measured?
Two-point Touch Threshold: seeing at what distance a person can perceive two separate points of touch
What does lateral inhibition mean?
Receptors that are most strongly stimulated inhibit those around them
What does lateral inhibition allow us to do?
To perceive well-defined sensations at a single location
What are two types of chemoreceptors?
- Interoceptors
2. Exteroceptors
What do interoceptors detect?
detect chemical changes within the body
What do exteroceptors include?
include taste and smell
How do exteroceptors deal with taste?
taste responds to chemicals dissolved in food and drink
How do exteroceptors deal with smell?
smell responds to chemical molecules in the air.
What is another name for taste?
Gustation
What are the receptors for gustation (taste called)?
Taste buds
What type of cells are taste buds composed of?
Specialized epithelial cells
What do the specialized epithelial cells that make up taste buds behave like?
neurons
Generally how do taste buds sense taste?
- Depolarize and produce action potentials
- Cells release neurotransmitters onto sensory neurons
- Microvilli come into contact with chemicals
Each taste bud has taste cells sensitive to _______________.
each category of tastes
What are the four different types of taste?
- Salty
- Sour
- Sweet and Umami
- Bitter
How does salty taste work?
Na+ enters taste cell and depolarizes it
How does sour taste work?
H+ enters cell and depolarizes it
How does sweet/umami taste work?
Sugar or glutamate binds to receptor and activates G-proteins/ 2nd messengers to close K+ channels
How does bitter taste work?
Quinine binds to receptor, activates G-protein/2nd messenger to release Ca2+ into the cell.
What is another name for smell?
olfaction
Where are olfactory receptors located?
in the olfactory epithelium of the nasal cavity
What oxidizes hydrophobic volatile odors?
Sustentacular cells
What cells replace receptors damaged by the environment?
Basal stem cells
What is the structure of olfactory receptors?
bipolar neurons with ciliated dendrites projecting into the nasal cavity
When discussing olfactory receptors, what binds to odors?
Proteins in the cilia bind to odors
_____ genes code for _______ different olfactory receptors.
- ~350
2. ~350
What provides a sense of equilibrium?
Vestibular Apparatus
Where is the Vestibular Apparatus located?
inner ear
What does the Vestibular Apparatus consist of?
- Otolith organs
- Utricle and saccule - Semicircular canals
What is the structure of the inner ear?
Consists of a bony labyrinth surrounding a membranous labyrinth
What is in-between the bony labyrinth and membranous labyrinth?
Perilymph (fluid)
What is within the membranous labyrinth?
fluid called endolymph
What is unusual about the concentration of endolymph?
Has an unusually high K+ concentration
What is the function of the Utricle and Saccule?
Provide information about linear acceleration
Does the utricle provide horizontal or vertical information?
Horizontal
Does the saccule provide horizontal or vertical information?
Vertical
What is the name of the specialized epithelium that houses hair cells in the otolith organs?
macula
What are stereocilia embedded in, in the otolith organs?
a gelatinous otolithic membrane
What is the structure of sensory hair cells in the otolith organs?
Modified epithelial cells with 20−50 hairlike extensions called stereocilia (not true cilia) and one kinocilium (true cilium)
Which is true cilium, stereocilia or kinocilium?
kinocilium
What happens when stereocilia bend toward the kinocilium? Then what happens?
- K+ channels open, and K+ rushes into the cell
2. Cells release a neurotransmitter that depolarizes sensory dendrites in the vestibulocochlear nerve
What happens when stereocilia bend away from the kinocilium?
Hyperpolarizes sensory dendrites
When stereocilia bend toward the kinocilium and cause depolarization and vice versa this makes a code for ____ ____ ____.
Detection of direction
Semicircular canals project along three planes to detect _______.
rotation
Each semicircular canal contains a duct filled with ______.
endolymph
At the base of each semicircular DUCT is what? What is contained within here?
- An enlarged area called the ampulla
2. Hair cells are embedded in the crista ampullaris, with stereocilia stuck into a gelatinous cupula
In semicircular canals, what does rotation do?
Rotation makes the endolymph circulate, pushing the cupula and bending the hair cells
What is the neural pathway for rotation?
- The vestibulocochlear nerve synapses in the medulla
- The medulla sends neurons to the oculomotor area of the brain stem to control eye movements and down the spinal cord to adjust body movements
What is nystagmus?
The jerky eye movement that is produced after spinning
- When a person’s body is spinning, eye movements are toward the ______ ______ of the spin to maintain a fixation point.
When the body comes to a stop, the_____ is bent by fluid inertia and eye movements are still affected.
The jerky eye movement produced is called ______.
- Opposite Direction
- Cupula
- Nystagmus
Nystagmus can cause a loss of equilibrium called what?
vertigo
What can vertigo be accompanied by?
dizziness, pallor, sweating, nausea, and vomiting
What are sound waves characterized by?
- Frequency (Hz)
2. Intensity or loudness (dB)
What is the relationship of frequency and pitch?
Higher frequency = higher pitches
What is the human range for frequency?
20-20,000Hz
How do sound waves travel through the outer ear?
Sound waves are funneled by the pinna (auricle) into—-> the external auditory meatus which channels them into___> the tympanic membrane
Where is the middle ear located?
Cavity between the tympanic membrane and cochlea
What are the names in order of the 3 ossicles?
- Malleus
- Incus
- Stapes
What is the function of the ossicles?
Vibrations are transmitted and amplified along the bones
What is the stapes attached to?
Oval window
What is the function of the oval window?
Transfer vibrations into the inner ear
Nickname for the cochlea:
Bony Labyrinth
What is the hearing part of the inner ear?
Cochlea
How many chambers does the cochlea have?
3
Name the 3 chambers of the cochlea in order from top t o bottom?
- Scala vestibuli (upper chamber)
- Scala media/cochlear duct (middle chamber)
- Scala tympani (lower chamber)
Of the 3 chambers of the cochlea, which are part of the bony labyrinth?
Scala vestibuli (upper chamber) & Scala tympani (lower chamber)
Of the 3 chambers of the cochlea, which are part of the membranous labyrinth?
Scala media/cochlear duct (middle chamber)
Of the 3 chambers of the cochlea, which are filled with perilymph?
Scala vestibuli (upper chamber) & Scala tympani (lower chamber)
Of the 3 chambers of the cochlea, which are filled with endolymph?
Scala media/cochlear duct (middle chamber)
Describe the path of sound transmission from the middle ear onward (not neural path/ think: vibrations)
- Vibrations from the oval window of the middle ear displace perilymph in the scala vestibuli
- Vibrations pass into the cochlear duct through the endolymph
- Next, vibrations pass into the perilymph of the scala tympani
- Vibrations leave the inner ear via the round window
Where along the cochlear duct the sound waves are transmitted depends on what?
Frequency of the sound
Does high or low frequency sounds travel further down the spiral of the cochlea?
Low-frequency sounds
What is another name for the organ of corti?
Spiral organ
Where are sensory hair cells located in the spiral organ (organ or corti?
On the basilar membrane of the scala media
How are inner hair cells arranged? How many sensory neurons innervate each inner hair cell? (spiral organ/organ of corti)
- One row that runs the length of the basilar membrane
2. Each is innervated by 10−20 sensory neurons
How are outer hair cells arranged? Are outer hair cells innervated by sensory or motor neurons? What happens when depolarized? What happens when hyper polarized?
(spiral organ/organ of corti)
- Arranged in rows
- Motor
- Shorten
- Elongate
What are stereocilia embedded in? (spiral organ/organ of corti)
Gelatinous tectorial membrane
What happens when sound waves enter the scala media?
the tectorial membrane vibrates, bending stereocilia:
- Opens K+ channels
- K+ rushes in, depolarizing the cell
- Releases glutamate onto sensory neurons
Which hair cells are stimulated more often? What magnifies this affect? This magnification allows us to do what? (spiral organ/organ of corti)
- Hair cells located closest to where the vibrations are displaced into the scala media are stimulated more often
- Outer hair cells magnify this effect, which allows us to differentiate between very similar pitches
What is the neural pathway for sound?
Vestibulocochlear nerve ---> Medulla oblongata ----> Inferior colliculus of midbrain ----> Thalamus -----> Auditory cortex of temporal lobe
The auditory cortex of temporal lobe is said to be tonotopic, what does this mean?
Different areas represent different sound frequencies
What are the two types of hearing impairment?
- Conduction deafness
2. Sensorineural/perceptive deafness
What is conduction deafness?
Sound waves are not conducted from the outer to the inner ear
What can be potential causes to conduction deafness?
- May be due to a buildup of earwax
- Too much fluid in the middle ear
- Damage to the eardrum
- Overgrowth of bone in the middle ear
What frequencies does conduction deafness impair?
Impairs hearing of all sound frequencies
What can conduction deafness be corrected by?
Can be helped by hearing aids
What is sensorineural/perceptive deafness?
Nerve impulses are not conducted from the cochlea to the auditory cortex
What can be a cause of sensorineural/perceptive deafness?
May be due to damaged hair cells (from loud noises)
Does sensorineural/perceptive deafness also impair all sound frequencies?
May only impair hearing of particular sound frequencies and not others
What can sensorineural/perceptive deafness be corrected by?
Cochlear implants
What is the function of the eyes?
Transduce light energy into nerve impulses
Can the entire electromagnetic spectrum excite photoreceptors?
Only a limited part of the electromagnetic spectrum can excite photoreceptors
Describe the path light takes into the eye.
- Light passes through the cornea and into the anterior chamber of the eye.
- Next, it passes through the pupil, which can change shape to allow more or less light in.
- Then it passes through the lens, which can change shape to focus the image.
- Finally, it hits the retina, where photoreceptors are found.
What can can increase or decrease the diameter of the pupil?
Iris
When talking about the pupil, and iris define constriction?
contraction of circular muscles via parasympathetic stimulation
When talking about the pupil, and iris define dilation?
contraction of radial muscles via sympathetic stimulation
When light passes from one medium to another, it ____. This is called ____ ____.
- Bends
2. Light refraction
______ at the point of refraction can also bend light
Curvature
Changing the curvature of the ____ allows fine control of focus.
Lens
In what process is the image flipped upside down?
Light refraction
What are visual fields?
The part of the external world projected onto the retina
The right side of the visual field is projected to what side of the retina?
Left
The left side of the visual field is projected to what side of the retina?
Right
What is the lens suspended from, and what are those attached to?
- Suspensory ligaments
2. Ciliary body muscles
What is lens accommodation?
Accommodation is the ability of the lens to keep an object focused on the retina as the distance between the eye and the object moves
Contraction of the ciliary muscle does what? This is good for what?
- Allows the suspensory ligaments to relax and the lens to thicken (rounder)
- Close vision
Relaxation of the ciliary muscle does what? This is good for what?
- Relaxation of the ciliary muscle pulls on the suspensory ligaments, causing the lens to thin
- Distant vision
What is myopia?
Nearsightedness
Where are distant images focused with myopia?
Distant images are brought to a point of focus in front of the retina
In myopia, is the eyeball elongated or shortened? What type of lenses can correct myopia?
- Elongated
2. Concave
What is hyperopia?
Farsightedness
Where are distant images focused with hyperopia?
Distant images are brought to a point of focus behind the retina
In hyperopia, is the eyeball elongated or shortened? What type of lenses can correct hyperopia?
- Short
2. Convex
Astigmatism is asymmetry between what? What is going on with the rays?
- Cornea and lens
2. Rays do not focus
What type of lenses is an astigmatism corrected by?
Cylindrical lenses
Neuron axons in the retina are gathered at a point called the ________.
Optic disc (blind spot)
Besides neurons/nerves what also enters at the blind spot?
Blood vessels
What are the layers of the retina from outer to inner?
- Ganglion cells
- Bipolar cells
- Photoreceptors (rods and cones)
The rods and cones consist of what segments?
- Outer segment
2. Inner segment
Describe the outer segment of rods and cones
full of flattened discs with photopigment molecules
When talking about the 3 layers of the retina, how do the cells of each layer synapse?
From bottom up (Photoreceptors—> bipolar cells—> ganglion cells)
Where is the retinal pigment epithelium located?
under the rods and cones
How does the retinal pigment epithelium help vision?
- Phagocytizing shed outer discs
- Absorbing scattered light
- Delivering nutrients to rods and cones
- Suppressing immune attack in retina
- Participating in visual cycle of retina
- Stabilizing ionic concentrations in area
What do rods allow for?
Allow for black and white vision in low light
What pigment do rods cells contain? What type of light does this absorb the best?
- Rhodopsin
2. Green light
Absorption causes rhodopsin to dissociate into what?
retinaldehyde and opsin
What is another name for retinaldehyde?
retinal
What is retinaldehyde derived from?
Vitamin A
Absorption causes rhodopsin to dissociate into retinaldehyde and opsin. What is this called?
Bleaching reaction
When a person enters a dark room after being in the light, there are ____ (1) ______ in the rods and cones. After about __(2)__ minutes, more visual pigments are produced, and the person’s eyes adapt to the dark
- fewer photopigments
2. 20 minutes
Dark current: In the dark, photoreceptors inhibit (hyperpolarize) what cells?
Bipolar cells
In a dark current, what is always open and what are they depolarizing? What does this allow?
- Na+ channels in rods and cones are always open, depolarizing the photoreceptor
- To release inhibiting neurotransmitter in the dark
What happens when light hits photoreceptors? What happens as a result?
Photoreceptors are hyperpolarized, and inhibition on bipolar cells is lifted…. Bipolar cells can now stimulate ganglion cells
What do cone cells allow for and what are they less sensitive to?
Cones are less sensitive to light, but allow color vision and greater visual acuity
______ _____ involves three types of cones.
Trichromatic vision
What color are S (short) wavelengths?
Blue
What color are M (medium) wavelengths?
Green
What color are L (long) wavelengths?
Red
Instead of opsins, what do photopigments have?
Photopsins
Do photopsins vary in each type of cone?
YES
Vision is best at one point in the retina, called the what?
fovea centralis
In the fovea centralis why is vision so clear?
Other layers of the retina are pushed aside, so light falls directly on a group of cones
What is the ratio between cones and ganglion cells in the fovea centralis? What is it in the other places of the eye?
- 1:1
2. 105:1
The fovea centralis only works in _____ ___.
Good light
______ of lots of rods onto a single ganglion cell increases light sensitivity.
Convergence
What is control of eye movement produced by?
Produced by contraction of extrinsic eye muscles
What are the 3 types of eye movement?
- Saccadic eye movement
- Smooth pursuit movements
- Vergence movements
Describe saccadic eye movement.
high-velocity movements that keep the image focused on the fovea centralis (good when reading)
Describe smooth pursuit movements.
match the speed of a moving object
Describe vergence movements.
allow both eyes to converge so image is at the fovea of both eyes
What is the photopigment of ganglion cells?
melanopsin
What does the photopigment of ganglion cells (melanopsin) do?
- Sends information about illumination (brightness of light)
- Helps control pupillary reflex (constriction in bright light)
- Sets circadian rhythms in suprachiasmatic nucleus of hypothalamus
What are ganglion receptive fields? What do they allow for?
- Area of the retina with photoreceptors that send input to that ganglion cell
- Enhancement of edges, improving visual clarity
Some ganglion cells have on-center fields. What does a light in the center of a field do?
A light in the center of the receptive field stimulates the ganglion cell strongly.
Some ganglion cells have on-center fields. What does a light toward the edge of a field do?
A light toward the edge of the receptive field inhibits the ganglion cell
Some ganglion cells have off-center fields. What does a light in the center of a field do?
A light in the center of the receptive field inhibits the ganglion cell
Some ganglion cells have off-center fields. What does a light toward the edge of a field do?
A light toward the edge of the receptive field stimulates the ganglion cel
