(135) Chapter 2 Flashcards Preview

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Flashcards in (135) Chapter 2 Flashcards Deck (67):
1

Absorption spectrum

What is the plot of the amount of light absorbed versus the wavelength of the light?

2

Action potential

This denotes the signal which lasts about 1 millisecond w/c happens from resting potential at (-70 mV) --> (+40 mV) --> negative again --> resting potential again.

3

Amacrine cells

Other than bipolar and ganglion cells, and receptors, what are the two types of neurons that connect neurons across the retina? (2)
Signals traveling between bipolar and ganglion cells use this.

4

Axial myopia

Eyeball is too long; images of faraway objects are not focused sharply.

5

Axon

_____ is filled with fluid that conducts electrical signals.

6

Bipolar cells

Where do signals generated in the receptors travel to first?

7

Blind spot

This is a spot where there are no receptors (receptors are missing).

8

Cell body

This is the key component of neuron. This contains mechanisms to keep the cell alive.

9

Cone spectral sensitivity curve

What do you call a curve that is produced when an observer looks directly at a test light so that it stimulates only the cones in the fovea?

10

(Neural) Convergence

This occurs when a number of neurons synapse onto a single neuron.

11

Dark adaptation

The process of increasing sensitivity to light in the dark

12

Dark adaptation Curve

A function which relates sensitivity to light to time in the dark, beginning when the lights are extinguished.

13

Dark-adapted sensitivity

"This threshold, the minimum amount
of energy necessary to just barely see the light, is converted to sensitivity; it is measured while the eyes are adapted to the light; 100,000 times greater than the light-adapted sensitivity mea- sured before dark adaptation began"

14

Dendrites

These parts of the neuron branch out from the cell body to receive electrical signals from other neurons

15

Depolarization

Process which shows the inside of the neuron becoming more positive; causes the charge to change in the direction that triggers an action potential; an excitatory response

16

T/F

detachment of retina to pigment epithelium can occur as a result of traumatic injuries of the eye or head, as when a baseball player is hit in the eye by a line drive.

17

Excitatory response

This occurs when the inside of the neuron becomes more positive; one of the two types of responses by the receptor sites.

18

Far point

_____ point is he distance at which light becomes focused on the retina.

19

Fovea

It only contains cones. When we look directly at an object, the object’s image falls on this one.

20

Ganglion cells

Where do signals generated in the receptors travel to after the bipolar cells?

21

Horizontal cells

Other than bipolar and ganglion cells, and receptors, what are the two types of neurons that connect neurons across the retina? (2)
Signals travel between receptors through here.

22

Hyperopia

This condition happens when the focus point for parallel rays of light is located behind the retina, usually because the eyeball is too short.

23

Ions

They are molecules that carry an electrical charge; present in the liquid solution of neurons.

24

Retinal changes shape from being bent to straight and detaches from the opsin.

What happens in isomeization?

25

Lateral geniculate nucleus

These signals (from receptors transported to neurons w/in retina) are transmitted out of the back of the eye in the optic nerve to a group of neurons

26

Lens

20% of the focusing power goes here.

27

Macular degeneration

A condition most common in older people, destroys the cone- rich fovea and a small area that surrounds it. This creates a blind region in central vision, so when a person looks directly at something, he or she loses sight of it

28

Monochromatic light

Light of a single wavelength used when measuring one wavelength at a time and the observer's sensitivity to each wavelength

29

Myopia

An inability to see distant objects clearly. The system of this condition brings parallel rays of light into focus at a point in front of the retina, so the image that reaches the retina is blurred.

30

Near point

This distance at which the lens can no longer accommodate to bring close objects into focus.

31

Nerve fiber

filled with fluid that conducts electrical signals

32

Neural circuits

interconnected groups of neurons

33

Neural convergence

This occurs when one of more neuron synapse into a single neuron.

34

Neuron

Electrical signals occur in structures

35

Neurotransmitter

These are chemicals released at the end of the neuron

36

Peripheral retina

This contains both rods and cones and all of the retina outside of the fovea.

37

Permeability

The ease with which a molecule can pass through the membrane; can be seen through the opening of channels (i.e. Na) and can be highly selective to a specific type of molecule.

38

Pigment epithelium

a layer that contains enzymes necessary for pigment regeneration.

39

Presbyopia

The increasing of distance of the near point as a person gets older.

40

Propagated response

This is an important property of action potential; once the response is triggered, it travels all the way down the axon without decreasing in size.

41

Pupil

A hole in the iris from which light passes through. Controls dilation or constriction of the pupil.

42

Purkinje shift (p. 33)

Enhanced perception of short wavelengths during dark adaptation

43

Receptor sites (p. 39)

These are small areas on the receiving neuron after the synapse; specific to neurotransmitters.

44

Refractive myopia (p. 25)

A condition in which the cornea and/or the lens bends the light too much; images of faraway objects are not focused sharply

45

Refractory period (p. 37)

The interval between the time one nerve impulse occurs and the next one can be generated in the axon.

46

Resting potential (p. 36)

______ potential is when the axon or nerve fiber is at rest and the difference in potential between the tips of two electrodes is -70 mV, which stays the same as long as there are no signals in the neuron.

47

Retinitis pigmentosa (p. 29)


This condition first attacks the peripheral rod receptors and results in poor vision in the peripheral visual field; it is also generational.

48

Rod monochromat (p. 31)

A condition wherein there are no cones due to a rare genetic defect.

49

Rod adaptation

A process where cones are more sensitive to light at the beginning of dark adaptation, they control our vision during the early stages of adaptation, so we can’t see what the rods are doing.

50

Rod spectral sensitivity curve (p. 33)

To measure this curve, we measure the sensitivity after the eye is dark adapted (so the rods control vision because they are the most sensitive receptors) and present test ashes in the peripheral retina.

51

Rod–cone break (p. 31)


The place where the rods begin to determine the dark adaptation curve.

52

Sensitivity

This can be measured by getting 1/threshold. High threshold (i.e. takes a high amt of light to be at the lower level of sensitivity).

53

Sensory receptor (p. 35)


neurons specialized to respond to environmental stimuli

54

Spectral sensitivity (p. 32)


eye’s sensitivity to light as a function of the light’s wavelength.

55

Spectral sensitivity curve (p. 32)


relationship between wavelength and sensitivity; to see diff wavelengths in the visible spectrum

56

Spontaneous activity (p. 38)

action potentials that occur in absence of stimuli from environment

57

Synapse (p. 39)

very small space between neurons

58

Threshold

minimum amount of energy necessary to just barely see the light

59

Transduction (p. 26)


transformation of one form of energy into another form of energy; transformation of light energy into electrical energy—occurs in the receptors for vision: the rods and cones

60

Visual acuity (p. 43)


Ability to see details clearly.

61

Visual pigment (p. 23)


These are molecules which absorb light and found in the outer segments of visual receptors.

62

Visual pigment bleaching (p. 31)

A process w/c accounts for change in shape and separation from the opsin causing the molecule to become lighter.

63

Visual pigment regeneration (p. 32)

A process which occurs more rapidly in the cones than in the rods; rods take about 20 to 30 minutes to reach their maximum sensitivity (point R on the curve), compared to only 3 to 4 minutes for the cones (point C) because of this.

64

excitatory and inhibitory responses

what are the two types of responses that occur at the receptor sites?

65

type of transmitter released and nature of receptor site in the receiving neuron

When electrical signal reaches the synapse, it triggers a chemical process that causes a new electrical signal in the receiving neuron. Where do the nature of these signals depend on?

66

Excitation

What increases the chance that a neuron will generate action potentials and is associated with increasing rates of nerve firing?

67

Inhibition

What decreases the chance that a neuron will generate action potentials and is associated with lowering rates of nerve firing?