BIO 360 - Exam 2 - Chapter 10 Sensory Processing SP 2023 PowerPoint Flashcards
The post-synaptic neuron can integrate the input of many
presynaptic neurons. Concepts of ______ and ______ summation.
spatial / temporal
The combination of several nearly simultaneous graded potentials is called spatial summation. The word spatial {spatium, space} refers to the fact that the graded potentials originate at different locations (spaces) on the neuron.
Summation that occurs from graded potentials overlapping in time is called temporal summation {tempus, time}.
Coded by number of receptors activated and frequency
of action potentials is called ______?
Coded by duration of a train of action potentials is called ______? - Some receptors can adapt or cease to respond.
intensity / duration
Fig. 10.6 Coding for stimulus intensity and duration
For individual sensory neurons, intensity discrimination begins at the receptor. If a stimulus is below threshold, the primary sensory neuron does not respond. Once stimulus intensity exceeds threshold, the primary sensory neuron begins to fire action potentials. As stimulus intensity increases, the receptor potential amplitude (strength) increases in proportion, and the frequency of action potentials in the primary sensory neuron increases, up to a maximum rate.
Figure 8-27a & Figure 8-27b
Figure 8-28a, 8-28b
What is the difference between no summation and summation causing an action potential?
No summation: two graded potentials will not cause an action potential if they are apart in time.
Summation causing an action potential: if two sub-threshold potentials arrive at the trigger zone within a short period of time, they may sum and create an action potential.
Figure 8-29a
What is presynaptic inhibition?
a modulatory neuron synapses on one collateral of the presynaptic neuron and selectively inhibits one target.
Table 10.1 Information processing by the sensory division
Somatic stimuli and visceral stimuli.
Somatic stimuli: muscle length & tension, proprioception.
Visceral stimuli: blood pressure,
Table 10.2 Types of Sensory Receptors
Chemoreceptors: Oxygen, pH, various organic molecules such as (glucose).
Mechanoreceptors: Pressure (baroreceptors), cell stretch (osmoreceptors), Vibration, acceleration, sounds
Thermoreceptors: Varying degrees of heat
Photoreceptors: Photons of light
Sensory Pathways
Stimulus as physical energy –> sensory receptor acts as a ______.
transducer
Sensory Transduction
- Stimulus energy converted into information processed by CNS.
- Ion channels or second messengers initiate membrane
potential change - ______ ______: Preferred form of stimulus
- ______ : Minimum stimulus
- ______ ______: Change in sensory receptor membrane potential.
Adequate stimulus / Threshold / Receptor potential
Fig. 10.1 Simple, complex, and nonneural sensory receptors
S______ r______ are neurons with free nerve endings.
Most s______ s______ r______ are cells that release neurotransmitter onto sensory neurons, initiating an action potential.
Simple receptors / special senses receptors
Receptive fields are different in different sensory ______!
Vision/photoreceptors – L______ / W______.
Audition/mechanoreceptors – F________ of Pr______ Wa______ . Olfaction/chemoreceptors – range of molecules.
modalities
light wavelength; frequency of pressure waves; range of molecules
Fig. 10.2 Receptive fields of sensory neurons: Two-Point Discrimination
Convergence – multiple primary to single 2nd sensory neuron = NO 2pt convergence
1:1 primary to secondary sensory neurons - two separate touches = 2pt convergence
In addition, sensory neurons of neighboring receptive fields may exhibit convergence, in which multiple presynaptic neurons provide input to a smaller number of postsynaptic neurons (Fig. 10.2). Convergence allows multiple simultaneous subthreshold stimuli to sum at the postsynaptic (secondary) neuron.
When multiple primary sensory neurons converge on a single secondary sensory neuron, their individual receptive fields merge into a single, large secondary receptive field, as shown in Figure 10.2a. There is no two-point convergence - one signal goes to the brain.
In contrast, more sensitive areas of skin, such as the fingertips, have smaller receptive fields, with as little as a 1:1 relationship between primary and secondary sensory neurons (Fig. 10.2b). In these regions, two pins separated by as little as 2 mm can be perceived as two separate touches.There is two-point discrimination - two signals go to the brain.
Fig. 10.5 Lateral inhibition
What is Lateral inhibition?
Lateral inhibition: capacity of excited neurons to reduce the activity of their neighbors.
The response of the primary sensory neurons A, B, and C are proportional to the intensity of the stimulus in each receptor field. Secondary sensory neurons inhibit secondary neurons A and C, creating greater contrast between B and its neighbors.
Fig. 10.15 Anatomy Summary . . . The ear
Hair Cells - What is positive and negative mechanical deformation?
Positive mechanical deformation: toward the kinocilium opens K+ channels in the stereocilia (depolarization). Ca2+ enters the cell, allowing vesicle fusion and the release of a neurotransmitter.
Negative mechanical deformation: away from the kinocilium closes K+ channels in the stereocilia (hyperpolarization).
The ______ is an ______ organ designed to enhance the capture of odor molecules and provides support and protection for
sensory cells.
nose / accessory
In mammals, ______ increase surface area for sensory cells that express odorant receptors and also direct air flow.
turbinates
Loss of the sense of ______ is one of the first signs of
______ disorders. One of the earliest manifestations of plaques and neurofibrillary tangles associated with Parkinson’s
and Alzheimer’s dementias is in the olfactory bulb.
smell / neurodegenerative
The olfactory signaling pathway via…
G-protein coupled receptors
Population Based Combinatorial Coding
Instead of dedicating an individual OR to a specific odor, the
olfactory system uses ______ ______ ______ ______ to
greatly reduce the number of receptors required to convey a
broad range of odors.
- A single receptor can recognize multiple odorants,
indicating that the system is NOT based on a strict
specificity “one odorant = one receptor.” - A single odorant is typically recognized by multiple
receptors. - Different odorants are recognized by unique combinations
of activated receptors.
combinations of receptor types
LATERAL INHIBITION IN THE OLFACTORY BULB
- Olfactory stimuli activate multiple classes of ______ ______ ______ that each express a single receptor protein subtype.
- Because receptor proteins are ______ ______,
even simple olfactory stimuli activate many different classes of receptor cells (red, blue and green). - This organization is continued at the next processing step, in which one receptor subtype (for example, red) activates antennal lobe projection neurons (PNs) with dendrites
that innervate the ‘red’ glomerular input station. - ______ ______ ______ attenuates signal transfer from receptor
cell to PN, resulting in _______________________ (bottom row of
simulated recordings) than in the ______ ______ (top row) that originate olfactory signals. - The magnitude of presynaptic inhibition reflects the overall
afferent drive to the antennal lobe, allowing this local circuitry to regulate gain and to prevent input saturation when animals are exposed to strong stimuli.
olfactory receptor neurons (ORNs) / broadly tuned / Presynaptic lateral inhibition / less firing in
downstream PNs / receptor cells
______ is a better predictor (by far) than cough, fever, shortness of breath if you have Covid.
- …ACE2 is expressed in support cells, stem cells,
and perivascular cells, rather than in neurons. - ACE2 protein in dorsally located olfactory epithelial
sustentacular cells and olfactory bulb pericytes in
the mouse. These findings suggest that CoV-2 infection
of non-neuronal cell types leads to anosmia.
Anosmia
Vertebrate and invertebrate eye development is
controlled by what gene?
PAX-6 gene – Controls transcription of DNA
What is the pathway for the eye and vision?
(1) Light enters the eye
* Focused on retina by the lens
(2) Photoreceptors transduce light energy
* Electrical signal
(3) Electrical signal
* Processed through neural pathways
Fig. 10.25 Anatomy Summary . . . The Eye
Pupil:
Lens:
Fovea:
Retina:
Optic disk:
Macula:
Central retinal artery and vein emerge from the ______ of the optic disk.
Pupil: changes the amount of light entering the eye.
Lens: bends light to focus on the retina.
Fovea: region of sharpest vision.
Retina: contains photoreceptors
Optic disk (blind spot): region where the optic nerve and blood vessels leave the eye.
Macula: the center of the visual field.
center.
COLOR vs NIGHT VISION
What is Achromatic?
RODS
NIGHT VISION
HIGH SENSITIVITY: one photon can change Vm
LOW TEMPORAL RESOLUTION CONVERGENCE: lots of rod cells converge on bioplar cell in next layer.
ACHROMATIC: we can’t discriminate colors at low light levels
COLOR vs DAY VISION
CONES
DAY VISION
LOWER SENSITIVITY
HIGH TEMPORAL RESOLUTION CHROMATIC: three types of cones with photo pigments that absorb light best in
different regions of the spectrum blue (short), green
(intermediate) and red (long).
Fig. 10.31 Light absorption by visual pigments
The visual pigments of cones are excited by different wavelengths of light, allowing us to see in color. White light is a combination of colors, as demonstrated when you separate white light by passing it through a prism. The eye contains cones for red, green, and blue light. Each cone type is stimulated by a range of light wavelengths but is most sensitive to a particular wavelength (Fig. 10.31). Red, green, and blue are the three primary colors that make the colors of visible light, just as red, blue, and yellow are the three primary colors that make different colors of paint.
What causes the spectral sensitivity of the different types of cones?
Sensitivity of rods and cones to different parts of the visual spectrum
Use monochromatic light to determine threshold at different wavelengths.
Threshold for light is lowest in the middle of the spectrum.
1/threshold = sensitivity, which produces the spectral sensitivity curve
Difference is due to absorption spectra of visual pigments.
Rod pigment absorbs best at 500 nm.
Cone pigments absorb best at 419nm, 531nm, and 558nm.
Absorption of all cones equals the peak of 560nm in the spectral sensitivity curve
Colored circles represent ______ ______ ______.
Open circles represent ______ ______ ______.
______ represents rod photo pigment.
amino acid substitutions /identical amino acids / Rhodopsin
Fig. 10.32 Phototransduction in rods
When a rod is in darkness and rhodopsin is not active, cyclic GMP (cGMP) levels in the rod are high, and both CNG and K+
channels are open (Fig. 10.32 1).
