sensory system Flashcards
flow of information in the nervous system
Sensory neuron brings in information we have an interneuron that brings about an action
Not every sensory input needs a response
All stimuli represent___
forms of energy
what is necessary to convert stimulus energy into a change in the membrane potential in the nervous system
sensory receptor
all sensory pathways have four basic functions in common
Sensory reception
Transduction
Transmission
Perception
Sensory reception
Capture the energy of sensory signal → sense it
receptor
Transduction
Puts the sensory signal into the language of the nervous system
Changes in membrane potential
transmission
Send sensory signal to our brain
Perception
Become aware of input so that you can respond to it
Types of sensory receptors
Ionotropic sensory receptors
Metabotropic sensory receptors
Ionotropic sensory receptors
A pressure receptor
Transmembrane protein that responds to pressure by changing conformation
Push→ opens→ lets ions in (+ charges)
Metabotropic sensory receptors
Channel that open and close
Chemoreceptor and photoreceptor
Have different receiving molecules
Taste molecules & light molecules
process of smelling steps overview
Step 1: sensory reception
Step 2: transduction
Step 3: transmission
Step 4: perception
Step 1: sensory reception
There are only a few dozen taste receptor genes
Odorants enter nose
There are different chemoreceptors for different odorants
Odorant receptors are largest gene family in the genome of mammals
Odorant receptors are sensitive to specific odorants
Step 2: transduction
Odorants bind to odor receptors
Causes change in resting potential
If it changes membrane potential enough the active potential occurs
Step 3: transmission
Get signal to brain to become aware of it
Olfactory receptor cell travels to brain → olfactory bulb of brain
Step 4: perception
We perceive that smell
Weak vs strong smell
Weak smell is a lower frequency of action potentials per receptor but a strong smell is a higher frequency of action potentials per receptor
More of the molecules you are smelling are coming into your nose→ more of the odor receptors will bind to molecule and you will more frequently set off action potentials
how do we sense heat
Heat is sensed by an ion channel called TRPV1
why do we snese heat when we eat peppers
Peppers have Capsaicin which binds to TRP channel and you get the sensation of hot from hot peppers
Messing with your head
Nothing is actually hot
:
Both olfaction(taste/smell) and vision(light) use
whta kind of receptors
metabotropic receptors
when we perceive vision what are we doing
Turning light into electrical signals
Objects in our environment will emit light or reflect light at different wavelengths
This gives us information on
the chemical composition of the object → what we call color
Specialized cells called photoreceptors are modified ___ that can detect ____. they turn light into ___
neurons
that can detect light
Turning light into electrical signals
human eye composition
Just inside the choroid(thin layer that nourishes the neurons) are the interneurons and photoreceptors of the retina
The lens is a transparent disk of protein
In front of the lens is the clear and watery aqueous humor and behind it is the jellylike vitreous humor
The iris is a muscular structure that controls the diameter of the pupil and thus how much light enters the eye
Visual information leaves the eye and goes to the brain via the optic nerve
The cells that are detecting light and turning light into neural signals is t
the rods and cones
Light passes through ___before reaching the ____cells
interneurons
light detecting
difference between rods and cones
Rods are more sensitive to light but don’t distinguish colors
Low light vision
Cones provide color vision
Different sensitivity to different colors
Photoreceptors synapse onto:
which then synapse onto
Bipolar cells → these then synapse onto ganglion cells (link ganglion cells w photoreceptor cells)
It is the axons of the ganglion cells that make up
the optic nerve(bundle of axons)
Horizontal cells
involved in processing the visual image even before it goes to the brain
They sharpen edges through lateral inhibition
Amacrine cells
have varied roles in visual processing such as detecting the direction of motion
Amacrine cells help detect motion
How does the retina convert light into membrane potential that your brain can use
It uses light receptor molecules called rhodopsin
Rhodopsin
transmembrane proteins that undergo changes in conformation as they absorb light
This sets off an event that leads to a membrane potential
consist of a protein called opsin and a light-absorbing group, 11-cis-retinal
11-cis-retinal
is covalently bound in the center of the opsin molecule
When 11-cis-retinal absorbs a photon, it changes to all-trans-retinal, which changes the conformation of the opsin
This change detects light
In rods and cones there are disks of membrane components (disks have lipid bilayer component on the outside and an internal compartments)
The transmembrane proteins that span the disks are the
opsin
Retinal absorbs light and goes from ___ to ___ configuration
cis
trans
Put retinal back to ___configuration so that your eye can detect light again
Enzymes in your eye do this
cis
Retinal is derived from ___
vitamin A
why does Consuming more vitamin A not make your eyes better
Once all your opsin have retinol in it it’s as good as it gets
How do we convert light into membrane potential
Photoreceptor in the dark has a membrane potential of about -40
Partially depolarized in the dark
To have the membrane potential go from the more typical -70 to -40 we have a sodium current going into the cell
This channel opens and closes depending on the presence of cyclic GMP (cGMP)
in the dark what process occurs
cGMP is produced and it binds to the sodium channel allowing sodium to come in
Releases glutamate
Signals to bipolar cells
in the light what occurs
It activates the rhodopsin by conversion of the cis-retinal to trans-retinal
This activated the molecule transducin which activates an enzyme called phosphodiesterase
what does phosphodiesterase do
This enzyme breaks cGMP to GMP
GMP doesn’t bind to the sodium channel
Closes sodium channel
Hyperpolarizes
Becomes more negative
When we absorb light our rods and cones become more negative
No glutamate released
In signal transduction in the eye, cyclic GMP:
Binds to a Na+ channel and opens it
