Lecture 19 - Sensory Systems 2

Question 1

Different types of eyes (3)

Answer 1

Pigment spot ocellus, compound eyes, simple eyes

Question 2

Pigment spot ocellus (4)

Answer 2

Simplest eye form and typically include pigmented cells, no lens and can detect light, cannot form images, animals with ‘eyespots’ exhibit positive or negative phototaxis

Question 3

Phototaxis

Answer 3

Movement of an organism in response to light

Question 4

Pigment spot ocelli can be found in (4)

Answer 4

Tardigrades, jellyfish, sea stars, flatworms

Question 5

Simple eyes (3)

Answer 5

Single lens, focuses light onto a layer of many receptor cells, some are relatively simple and some are very complex

Question 6

Insect simple eyes (3)

Answer 6

Cannot form images, can detect light, used to navigate during flight

Question 7

Cephalopod and vertebrate simple eyes (3)

Answer 7

Includes things like octopuses and gorillas. considered simple because they have a single lens but are however very complex, can form high resolution images

Question 8

Compound eyes (5)

Answer 8

Includes things like flies, found in insects and some other arthropods, composed of hundreds of thousands of ommatidia with each ommatidium containing receptor cells that send axons to the CNS, image forming eyes however resolution is far lower than resolution of human eyes, a compound eye will have to be 36 feet wide in order to have the resolving power of a human eye

Question 9

Ommatidium

Answer 9

Light- collecting column

Question 10

Iris

Answer 10

Pigmented muscle in vertebrate eyes that controls the size of the pupil

Question 11

Lens

Answer 11

In vertebrate eyes, focuses light onto the retina

Question 12

Vertebrate eyes (4)

Answer 12

Photoreceptors (rods and cones) react to light, photoreceptor cells synapse with bipolar cells, bipolar cells synapse with ganglion cells, ganglion cell axons connect to the brain via the optic nerve

Question 13

Vertebrate eyes pt 2 (6)

Answer 13

rods and cones contain stacks of membranes, opsin proteins found in membrane stacks, opsin contain retinal pigment molecule, opsin/retinal complex is referred to as rhodopsin in rods, retinal is in an inactive state in the dark and rhodopsin is inactive, cGMP - gated Na+ channels are open

Question 14

Vertebrate eyes pt 3 (7)

Answer 14

The Na+ depolarizes the membrane, inhibitory neurotransmitters released at synapse within bipolar cells, retinal changes conformation when it absorbs light, this activates rhodopsin (or just opsin in cone cells), rhodopsin activates transducin, transducin activates pDE and pDE breaks down cGMP, cGMP gated Na+ channels close

Question 15

Vertebrate eyes pt 4 (6)

Answer 15

Rod and cone membranes hyperpolarize, neurotransmitters are not released, in the absence of inhibitory neurotransmitters bipolar cells fire an action potential, excitatory neurotransmitters are released at the synapse between bipolar and ganglion cells, ganglion cells fire an action potential, action potential propagated to the brain along the optic nerve

Question 16

Color vision (3)

Answer 16

Different cones have different opsins, different opsins detect different wavelengths of light (color), mutations in opsin genes result in color blindness

Question 17

Rods (2)

Answer 17

sensitive to dim light, cannot distinguish wavelengths (color)

Question 18

Cones (2)

Answer 18

less sensitive to dim light, responds to different wavelengths (colors)