Psychology 2220A/B Chapter Notes - Chapter 11, 12: Embryonic Stem Cell, Cell Potency, Proprioception
2 May 2018
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LECTURE 11: SENSES
• Totipotent – cells can become any type of cell in body or placenta
• Pluripotent – cells can become any type of cell in the body (but not placenta)
– e.g., embryonic stem cells
• Multipotent – cells can become more than one, but not any, type of cell
– e.g., stem cells in the bone marrow can become red blood cells, white
blood cells or platelets, but not other types of cells
General Principles of the Senses:
Function of Sensory System:
- Converting senses (modality) into a language the brain understands action
potentials and synapses
Sensory Systems in Other Species:
- Echolocation
- Magnetroception
- Vision for other wavelengths of energy
- Infrared
- Ultraviolet
- Electrocutions
Sensory Organs:
Eye:
• All senses have specialized organs with specialized receptors
• The eye is like a camera
• Light
• Goes through pupil
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• Like the camera aperture
• Focused by cornea & lens
• Like the camera lens
• Focused on retina
• Like the film
• The retinal image is flipped
Dualism:
• dualism
– body/brain = physical stuff
– mind = mental stuff, soul?
– brain ≠ mind
• monism
– The mind is what the brain does
– Rene Descartes, Philosopher, 1596-1650
Phosphenes:
Why when you push one part of your retina, the phosphine location is 180 degrees
displaced?
- When you touch your eye, the cells are stimulated by pressure instead of
light
- You see them in the opposite corner because our optic construction flips
everything, left/right and up/down
- Whenever the photoreceptor is stimulated (top right) there is something
going on in the bottom left
Evolution of the Eye:
Euglena – relies on photosynthesis, needs light. eyespot enables it to move
toward/away from light, single cell organism
- has developed a visual system, can tell if the enviro is light or dark, the light
receptor is close to the tail (motor system) to propel the euglena through the
environment
- Eye is a good example of anatomy that people have used to argue that
evolution cant be right
- But can be explained with evolution
Flat Worm:
- Gagnlia are at the head location, eyes are in the head
- 1. Concavity has developed (bottom right picture)
- You can tell which direction the ligh is coming from
- 2. Nautilus pinhole eye leads to crisp images
- Main drawback, everything is dim
- 3. Hole opens up, development of lens
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- Something that is in eye chamber that has a different denisty of
material around it
- Light is bent by lens, can be focused and light
- 4. Flexible Lens
- Rounder or flatter
- Can see depths better
- Another evolutionary strategy:
- Insects have convexity not concavity
- Eologated cells called ommatidiium
- Each cell has a lens and photo receptors
Pinhole Cameras:
Pinhole
• Very simple focusing mechanism
• Flips image up-down, left-right
• Tradeoffs
• Small pinhole – clear image, great depth of field, dim image
• The simplest focusing mechanism
• Because it is so tiny, each spot on the film/eye can only get stimulated by
light coming from one point in the world and therefore the mapping is simple
and the picture/image is clear
• Pupils are like pinholes
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