BIO 365S Lecture Notes - Lecture 11: Receptive Field, Sensory System, Parietal Lobe

19 views5 pages

azureshark475

16 May 2018

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Large vs. Small receptive fields: Convergence

Sensitive vs. insensitive parts – convergence.

Big converge = lots of receptors on skin, but signal conduction when

converges (only one neuron processes the 3 different receptors). High

resolution = low/no convergence.

More sensitive = different neurons activating separate pathways to the

brain.

Have limited amount of neuron, cannot afford to make every body part

so sensitive, so certain body parts have convergence and some have

low sensitivity.

Perception of something is based on neuronal activity. For

convergence, no matter which colored area you touh, it does’t

matter (pro = save neuron for areas you care about; cons = low

resolutio), so you feel like it’s all oig i fro the sae area.

Divergence = one receptive field, one neuron responsible for it. When

activate, brain will know exactly which area specifically. High resolution,

BUT uses a lot of neuron for this area.

CNS must distinguish 4 properties of a stimulus:

1.Nature/modality

2.Location

3.Intensity

4.duration

5 senses = transfer stimulus into action potential. All the action

potetial are the sae eause they’re the sae size, so they all eed

to be able to code the 4 properties/information above.

1.If action potential comes from 1st/2nd/etc. senses, each is responsible

for a different physical stimulus.

3. Taste, touch, smell = already have location defined because of the

find more resources at oneclass.com

Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in

one area that you concentrate the sensory info at.

All 5 senses = can tell location.

2. Where signal comes from; for visual system, not too difficult; for

auditory it’s harder eause sound coming from left or right goes

through both ears (brain must be able to resolve this because you

yourself knows where the sound came from = sound coming from left

goes to left first, and going to the right will take 1 ms slower to create

an action potential, so brain catches the time difference; if sound

traels as fast as light the this o’t ork)

FYI: Interaural time differences for

different positions around the head

Center part = more pressure than peripheral.

Brai ats to e % sure, do’t at to guess = through euro

find more resources at oneclass.com

Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Big converge = lots of receptors on skin, but signal conduction when converges (only one neuron processes the 3 different receptors). More sensitive = different neurons activating separate pathways to the brain. Have limited amount of neuron, cannot afford to make every body part so sensitive, so certain body parts have convergence and some have low sensitivity. Perception of something is based on neuronal activity. For convergence, no matter which colored area you tou(cid:272)h, it does(cid:374)"t matter (pro = save neuron for areas you care about; cons = low resolutio(cid:374)), so you feel like it"s all (cid:272)o(cid:373)i(cid:374)g i(cid:374) fro(cid:373) the sa(cid:373)e area. Divergence = one receptive field, one neuron responsible for it. When activate, brain will know exactly which area specifically. But uses a lot of neuron for this area. Cns must distinguish 4 properties of a stimulus: 5 senses = transfer stimulus into action potential.

Related Questions

Exercise #5: The Nervous system and Perception

Task #1: Color vision

Introduction

In the human retina, there are two kinds of light-sensitive cells: rods and cones. These cells are located on the outside of the retina, away from the vitreous humor and against the choroid layer, and are covered by a later of bipolar and ganglion cells as well as neurons. Light enters the posterior chamber through the lens and must pass through several cell layers before it is absorbed by the rods and cones.

Cones are involved in color vision at daylight intensities. Generator potentials in a cone excite one neuron, giving high-level resolution vision. Cones will not cause neural firing at low light intensities and are, therefore, nonfunctional at night.

Rods provoke black-and-white vision at low light intensities. A bipolar cell associates with several rods, so that generator potentials sum in their effect. This assures neuronal firing at low light intensities and provides a highly sensitive vision but with less resolution.

Receptor convergence. A ganglion cell, which receives input from a number of rods, spread out over the retina, cannot pinpoint the source of a light stimulus as well as a ganglion cell, which is stimulated by a single photoreceptor. In the case of a ganglion cell receiving the added input of several rods, light hitting any one of the rods can cause a neural spike in the ganglion cell, but the brain has no way to know which rod was excited. It is therefore harder to pinpoint the location of light stimuli on the retina when the stimulus is detected by rods (as compared to cones). The result is that our ability to see detail, or our resolving power, is considerably lower under dim light conditions than under bright light conditions.

Dark adaptation. If you go from a lighted area to a very dark room, you will not be able to see. After about ten minutes, however, you begin to be able to see again. This occurs because the rhodopsin pigment, which gets broken down when it absorbs light, is continually re-synthesized in the rods. When there is very little light, very little rhodopsin gets broken down and the amount of rhodopsin gradually builds up, making the rod much more sensitive to dim light.

When light strikes a receptor cell, it triggers a photo-chemical reaction that leads to neuronal firing. If a rod or cone receives high-intensity light, the visual pigments will be temporarily bleached and will not absorb any more light. Within a matter of a few seconds, enzyme systems in the cells will restore the visual pigment to its light-absorbing form. This can be easily demonstrated. If, after viewing a bright light, the eye is quickly shut or turned to a dark wall, the bright image will persist as a positive afterimage because the high generator potential causes the continued firing of neurons. If the eye is cast on a lighter background after a few seconds, a negative afterimage, or a dark image of the object will appear. This is because the still bleached cells are not receptive to the light coming from the light background.

According to the Young-Helmholtz theory of color vision, there are three types of cone cells, which respond respectively to red, green, and blue light.

All other colors are perceived as the brain interprets impulses coming from a mix of these receptors. If an object of one color is viewed for a long period of time at high light intensity, the cones for that color will become bleached. The afterimage of the object will be seen in the complementary color.

The Exercise 6 PowerPoint will demonstrate afterimages to you. Use the slide show option to project the square of red light on your entire screen in a dark room. After staring intensely at the square for 30 seconds or so, without shifting your gaze, click enter to change the slide to a soft white. Continue staring at the screen as the change is made. What do you see? What was the color of the afterimage?

Repeat this experiment using a blue square. Before doing the experiment, hypothesize what color the afterimage will be according to the Young-Helmholtz theory.

Hypothesis to be tested: (2 pts)

What did you see when the experiment was conducted? (2 pts)

Was you hypotheses accepted or rejected? (1 pt)

Explain the colors seen in these afterimages using the Young-Helmholtz theory. (5 pts)

ambersnail873

BIO 365S Lecture Notes - Lecture 11: Receptive Field, Sensory System, Parietal Lobe

Document Summary

Get access

Related textbook solutions

Molecular Cell Biology

Biology: Science for Life with Physiology

Concepts of Biology

Biology

Essentials of Biology

Related Documents

BIOC32H3 Lecture Notes - Lecture 10: Olfactory Receptor, Cochlear Duct, Vestibular Duct

PGY 300 Lecture Notes - Lecture 7: Retina, Helicotrema, Taste Receptor

PGY 300 Lecture Notes - Lecture 7: Rhodopsin, Basilar Membrane, Tectorial Membrane

Related Questions