Chapter 16 - Senses Flashcards
– in neuroscience, this term can refer either to a protein that binds and responds to
chemical messenger or it can refer to a cell or structure that converts one kind of energy into
an electrical signal within a cell
Receptors
used for vision
Photoreceptors
used for hearing; touch; proprioception; respond to
stretch or bending of part of a cell
Mechanoreceptors
used for sensing taste (tongue), smell (olfactory), osmolarity
(hypothalamus), O2, CO2 (in hypothalamus and near heart) & H+ (in brainstem)
Chemoreceptors
create a sensation of pain; work by binding chemicals released
during inflammation and tissue injury; technically, they are chemoreceptors
Nociceptors
– pressure (actually a type of mechanoreceptor); found in walls
of major blood vessels and in the lungs to monitor lung expansion and stretch
Baroreceptors
provide information about position, stretch or force of
contraction of muscles, tendons & ligaments in the body. These allow you to
know the position of body parts relative to each other.
Proprioceptors
– the energy that activates the receptor
Stimulus
– process of changing stimulus into a change in membrane potential
Transduction
graded potential generated by sensory receptor; due to
opening/closing of gated channel
Receptor potential
– the type of energy sensed (e.g. light or sound)
Modality
strength of stimulation (e.g. how bright or how loud)
Intensity
– one afferent neuron and all the receptors that send it signals
Sensory unit –
the sensory area covered by one afferent neuron; one sensory unit
defines a receptive field
Receptive field
– precision of the sensation; often related to ability to localize stimulus
(generated by size of receptive fields
Acuity
decreased receptor response with continued stimulation; enhances
ability to detect change & ignore background
Adaptation
something that happens both at the level of the individual receptor and in the CNS.
Adaptation
are receptors that adapt very slowly and generate steady nerve
impulses.
Tonic receptors
c receptors generate a burst of action potentials when first stimulated
(on/off type response); they adapt quickly
Phasic receptors
– respond to chemicals produced by damage to tissues
Nociceptors
Bradykinin (most potent)
Prostaglandins
Serotonin
Histamine
most important and common stimulators of somatic pain.
- Pain can be a sharp, stabbing sensation that occurs very rapidly.
pain conducted via myelinated fibers
Fast
pain can be a longer-lasting, dull, diffuse
sensation. pain conducted unmyelinated fibers
slow
pain comes from
stimulation of skin or proprioceptors
Somatic
pain due to injury to internal organs
visceral
The location that feels pain has somatosensory
fibers coming in along the same dorsal root as visceral sensory fibers from the
affected organ.
Referred Pain
mechanisms for inhibiting nerve signals along pain pathways using enkephalin neurotransmitters (endogenous opiates) as well as pre-synaptic inhibition.
, spinal gating
chemoreceptors for external sensing
Olfaction (smell) & Gustation (taste)
Much of sense of taste
olfaction.
smell
oflaction
taste
Gustation
taste that detects compounds like quinine; GPCR
Bitter –
taste that detects H+ ions; open channels in membrane for H+
Sour/acid
n distinguish between something like 2000-4000
different chemicals; it does this using about 400 different odorant
receptors.
The olfactory system
Structures used for detecting orientation to gravity, as well as movement and
acceleration, key to balance, are
the vestibule & semicircular canals.
detects compression waves of molecules in air
hearing
(X axis =
time
y axis =
pressure
The height of a peak (trough to peak measure) is its
amplitude
The number of waves that pass the measuring point in a second is the
frequency
measured in decibels (dB), the wave generates the volume of the sound.
amplitude
, a logarithmic scale of the energy in the sound.
decibels (dB)
of the compression waves generates the pitch of the sound. is measured in cycles per second passing a point in space. This is called
Hertz (Hz).
frequency
Humans hear from
200-10,000 Hz
Sound over ___can cause permanent hearing loss if exposed to it for very long
90db
Sound causes pain around
120db
sound waves are collected and directed by the outer structures towards the eardrum or ___
Tympanic membrane
vibration of the eardrum is translated into movement of the ____
occicles
a membrane covering an opening into the vestibule
oval window
can tighten the eardrum to reduce the force of
pressure waves in the scala in the cochlea
Tensor tympani
can reduce stapes movement, also reducing the pressure (volume) of a wave in the scala of the
cochlea.
Stapedius
protect the ear from loud noises.
tympanic reflex
used for balance , filled with endolymph
semicircular canals
full of fluid, perilymph, which flows through the scala vestibuli to the helicotrema
the Vestibule
are part of the coiled cochlea, which detects sound
scala
vestibuli & scala tympani
used for balance, are also connected to the vestibule
semicircular canals (ducts),
In both the cochlea and semicircular canals, there is an additional inner
membranous tunnel or canal filled with
endolymph.
The movement of the stapes on the oval window sets up a
pressure/compression wave in the perilymph in the
Cochlea
The vibration of the
basilar membrane will lead to the bending of
stereocilia on the surface of the hair
cells in the organ of Corti.
The basilar
membrane is stiffer near the
round window
The basilar
membrane is less stiff near the
helicotrema.
Light will travel through the
cornea, aqueous humor (anterior chamber), lens, vitreous body (posterior chamber) and the first 4 layers of the retina
the fluid in the anterior chamber of the eye. produced by
the ciliary body and reabsorbed into the blood by the scleral venous sinus.
Aqueous humor
It is a common cause of blindness in the elderly.
glaucoma.
Light is photons traveling in waves and is part of the
electromagnetic spectrum
Light & Vision:
Different wavelengths of light are perceived as different colors when they excite the color photoreceptors called
cones
For ___, light is reflected by the colors (pigments) of the objects you look at.
vision
The excited photopigments activate, ____ protein
G
the world has to shrink to the size of the fovea or
macula for phototopic (daytime) vision. Light rays are bent to make this happen;
it’s called
refraction
occurs when light rays hit something with a
different density
refraction
- where optic nerve leaves eyeball; medial to macula; its
presence creates the “blind spot” in the visual field
retina
center of focus for retina when you look directly
at something;
Macula lutea or macula
– center of macula; all cones; highest density
fovea
create black & white vision in dim light creating scotopic (nighttime)
vision; only create a perception of light or no light; they do not help in
perception of color
rods
– create color vision in bright light creating phototopic (daytime)
vision
cones
– Refraction at the cornea and the filtering of the pupil combine
with the lens to form a small, focused image on the retina, usually on the fovea
when looking at something. upside down and backwards
Image Formation
normal, relaxed vision, focused about 20 ft away.
Emmetropia
– vision focused on a near object. This requires contraction of
muscles attached to the eyeball to rotate both eyes medially so that reflected light
from the near object can strike the fovea of both eyes at the same time
Convergence
adjusting for near or far vision;includes
convergence, pupil constriction and rounding/thickening the lens for near vision
Accommodation
hold the lens in place in the eyeball.
Suspensory ligaments
is a circular muscle within the suspensory ligaments that hold the lens
ciliary
muscle
when tthe suspensory ligaments stretch out the lens
making it thinner.
ciliary muscle relaxes
it stretches the suspensory ligaments taking tension off the lens. This
lets the lens get rounder and thicker for near vision
When the ciliary muscle contracts
is regulated by reflex arcs that can be
stimulated by the amount of light.
Pupil size
is the overriding
signal except in stress.
Light stimulation
fibers stimulate pupil constriction, which aids
near vision
Parasympathetic fibers
fibers stimulate pupil dilation, which can aid
distance vision.
Sympathetic fibers
; requires bright light to stimulate cones
cones
exciting red and green cones at the same time can create a
sensation of
yellow
most of cones are in or near the
macula of the retina
scotopic vision in dim light.are more densely packed at
the edges of retina, and fewer of them are found near the macula.
Rods
fuzzy without color, but it does cover a wider field of vision than phototopic
vision.
Scotopic vision
When the 2
differing images from each retina are brought together in the cortex, your brain
perceives those subtle differences in image positioning on the retinas as distance
or depth.
Stereoscopic vision
