ANAT 321 Lecture Notes - Lecture 10: Franz Nissl, Golgi'S Method, Granule Cell

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carmineminnow41

26 Mar 2020

School

McGill University

Department

Anatomy & Cell Biology

Course

ANAT 321

Professor

David Ragsdale

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Document Summary

The cortex is comprised of 6 distinctive layers, along the white matter where these layers are identified by cell type and referred to by their numbers. Molecular layer: no cells are located here, but you"re able to get axons. External granule layer: the region of the white matter in the cortex that has a large number of small cells (granules) External pyramidal layer: region of triangular shaped cells. Internal granule layer: filled with tons of granule cells (not as many as layer 2) Internal pyramidal layer: where there are tons of large pyramidal cells. Multiform layer: a mishmash of various cell types. Layer iv: internal granule layer packed densely with granules and is the main site of input for the cortex. Afferent axons from the thalamus terminate here because these granule cells are specialized to receive thalamic inputs to go up to the cortex. Layers ii/iii: external granule/pyramidal layers principle outputs of the cortex.

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

Select the statements that correctly represent the theory ofevolution. Select all that apply.

Evolution is partly about inheritance. Evidence of evolution isseen in structures such as wisdom teeth and the tail bone inhumans. These structures are thought to be âleft overâ from ourancestors and no longer appear to have any essential function inmodern humans.

Natural selection means that todayâs organisms are perfectlyadapted after millions of years of fine-tuning. No further changesare necessary because of all the progress that has been made bynatural selection.

We can see evidence of past natural selection in adaptationssuch as the camouflage of moths perched on the bark of their hosttree. We can also see natural selection at work today if we trackhow populations change in rapidly changing environments.

The theory of evolution does not apply to life today. It isstrictly about the history of life: what happened in the past asseen in fossils.

Scientists disagree about the main ideas of evolutionary theorybecause of incomplete or conflicting evidence.

Question 2

Select one answer.

10 points

The ability or tendency of organisms and cells to maintainstable internal conditions is called

metabolism

homeostasis

emergent property

evolution

Question 3

Select one answer.

10 points

Why do organisms maintain fairly steady conditions within theircells and bodies?

They need to keep conditions stable so that they can obtainfood.

Organisms just change along with whatever is happening in theoutside world, which is usually quite steady.

They must maintain stable conditions to keep their enzymesworking and generally to enable the chemical reactions of life.

Unstable conditions will destroy the DNA in cells; this is themost important risk for a cell facing physical or chemicalstress.

Question 4

Select one answer.

10 points

An organism or cell exhibits ____________ when it maintainssteady internal conditions despite changes in the outerenvironment.

homeostasis

evolution

balance

natural selection

Question 5

Select one answer.

10 points

Which type of molecule best illustrates the very strongrelationship between structure and function in biology?

enzymes

oxygen gas

all kinds of organic matter

water

Question 6

Select one answer.

10 points

Which best expresses how nutrients and energy move throughlife?

Nutrients flow from sunlight to organic matter to heat. Energycycles among all life forms.

Nutrients cycle among all life forms. Energy flows from sunlightto chemical energy to heat.

Nutrients and energy both are continually recycled in a greatcircle of life.

Question 7

Select one answer.

10 points

Which of the following is not a recurring theme in biology?

Living organisms maintain homeostasis.

Energy flows through living systems while matter isrecycled.

Evolutionary processes explain both the unity and adaptivediversity of life.

All of these are recurring themes.

Question 8

Select one answer.

10 points

Which statement about evolution is FALSE?

According to evolutionary theory, you are related to abacterium, to a yeast cell, to a snake, and to a whale. In fact,you are related to every species now alive on Earth, and to fossilspecies like dinosaurs as well.

Evolution occurs constantly, without end; there is no endpointin evolution.

Natural selection acts on genetic differences within apopulation to cause evolution. Individuals do not evolve.

Natural selection is about slow but steady progress. Through it,populations constantly get better-adapted. When this process iscompleted for all populations, evolution will come to a stop.

Question 9

Select one answer.

10 points

Imagine you have a peanut butter sandwich in front of you. Thesandwich is an example of _______.

matter

energy

Question 10

Select one answer.

10 points

You provide your gut bacteria with a warm place to live. Theyprovide you with vitamins and other services. This most directlyrepresents an example of...

shared ancestry of all life

natural selection

homeostasis

interdependence of life

ANAT 321 Lecture Notes - Lecture 10: Franz Nissl, Golgi'S Method, Granule Cell

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