Sensory Systems

Question 1

What is ionotropic sensory detection?

Answer 1

the receptor protein itself is part of the ion channel and opens or closes the channel pore by changing its conformation

Question 2

What is metabotropic sensory detection?

Answer 2

the receptor protein is linked to a G protein that activates a cascade of events that eventually open or close ion channels

Question 3

Receptor potential

Answer 3

a change in the membrane potential of a sensory cell in response to a stimulus

Question 4

Stretch receptor pathway

Answer 4

1. stretching the muscle = stimulus (that opens ion channels in dendrites)
2. depolarization spreads to the cell body > receptor potential
3. RP spreads to the hillock (if strong enough to reach threshold > action potential triggered)

Question 5

Mechanoreceptors

Answer 5

receptors that are sensitive to mechanical forces, involved in many sensory systems

Question 6

What causes ion channels to open for sensory systems?

Answer 6

physical distortion of mechanoreceptor’s plasma membrane

Question 7

Surface level mechanoreceptors

Answer 7

Merkel’s disks and Meissner’s corpuscles

Question 8

Merkel’s disks

Answer 8

surface mechanoreceptors that adapt slowly and provide continuous information

Question 9

Meissner’s corpuscles

Answer 9

surface mechanoreceptors that adapt rapidly and are very sensitive

Question 10

Deeper mechanoreceptors

Answer 10

Ruffini corpuscles and Pacinian corpuscles

Question 11

Ruffini corpuscles

Answer 11

deeper mechanoreceptors that adapt slowly and sense low frequency vibrations

Question 12

Pacinian corpuscles

Answer 12

deeper mechanoreceptors that adapt quickly and sense high frequency vibrations

Question 13

What is special about hair cells?

Answer 13

They are a special kind of mechanoreceptor found in the cochlea of the ear that respond to the vibration induced by sound

Question 14

What are rhodopsins?

Answer 14

a family of photoreceptors that are composed of a pigment (retinal) bound to a protein (opsin)

Question 15

What are channelrhodopsins and why are they important?

Answer 15

a new “optogenic” tool for stimulating neurons developed by single-called plants

Question 16

Evolution of eyes

Answer 16

shows progression of complexity

Question 17

What is an example of de-evolution?

Answer 17

Eastern American mole: vestigial eyes
-they don’t need to create images underground, just differentiate between light and dark

Question 18

What are ommatidia?

Answer 18

compound eyes consisting of many optical units in arthropods; each ommatidium has a lens that directs light onto photoreceptor cells (retinula cells)

Question 19

What are retinula cells?

Answer 19

they contain rhodopsin and their axons communicate w/ the nervous system

Question 20

What kind of view do ommatidia give?

Answer 20

broken-up images

Question 21

What does insect vision look like?

Answer 21

Mottled impressionist paintings: spots of paint are integrated by our brain into coherent images (Pointillism)

Question 22

Veretebrae eyes have ___ and ____

Answer 22

rods and cones

Question 23

What is a rod cell?

Answer 23

A modified neuron that has an outer segment, an inner segment, and a synaptic terminal

Question 24

What does the inner segment have?

Answer 24

nucleus and many mitochondria

Question 25

What does the outer segment have?

Answer 25

a stack of membrane-bound discs that are densely packed w/ rhodopsin

Question 26

What is the role of the discs in the outer segment of vertebrae eyes?

Answer 26

Capture photons

Question 27

What does light do to a rod cell?

Answer 27

Hyperpolarize

Question 28

Membrane potential of a rod cell (in the dark/light)

Answer 28

1. Rod cell = depolarized resting potential (Na+ channels are partially open) 2. cGMP keeps Na+ channels open 3. When light is absorbed by rhodopsin, cell becomes photoexcited and activates a G protein called transducin 4. Activated transducin activates cGMP phosphodiesterase that converts to cGMP to GMP, causing cGMP levels to fall 5. Na+ channels close completely 6. Rod cells hyperpolarizes

Question 29

Organization of the retina

Answer 29

Photoreceptors (rods and cones) synapse onto bipolar cells Bipolar cells (input from PRs, output to ganglion cells) Ganglion cells (axons project thru the optic nerve to the brain)

Question 30

Dark response

Answer 30

depolarized cells release glutamate continuously onto bipolar cells

Question 31

Light response

Answer 31

hyperpolarized photoreceptor cells stop releasing glutamate

Question 32

What are Type 2 bipolar cells?

Answer 32

They have metabotropic receptors for Cl- channels.

Question 33

How do Type 2 bipolar cells function?

Answer 33

When glutamate is released, the Cl- channel in the bipolar cell is open and hyperpolarized (darkness). When glutamate is not released, the metabotropic receptor turns off, closing the Cl- channel. This causes the bipolar cell to depolarize to threshold and fire an action potential

Question 34

Pathway after depolarization

Answer 34

1. Depolarized bipolar cells fire an action potential 2. Releases neurotransmitter onto ganglion cells 3. Fires an action potential that goes down the optic nerve to the brain

Question 35

What are the important parts of the eye?

Answer 35

cornea, aqueous humor, iris, pupil, lens, vitreous humor, retina

Question 36

What is the blind spot on the retina?

Answer 36

An area on the back of the eye where blood vessels and the optic nerve pass through the back of the eye; there are NO photoreceptors

Question 37

What does the lens do?

Answer 37

Makes fine adjustments in the focus of images on the photosensitive retina at the back of the eye; mammals and birds alter lens shape to focus

Question 38

What is the most sensitive area of the retina?

Answer 38

the fovea

Question 39

What causes near-sightedness (myopia) and far-sightedness (hyperopia)?

Answer 39

Changes in the shape of the eyeball that put the focal length outside of the range in which the lens is able to focus

Question 40

What happens to lenses as we age?

Answer 40

they become less elastic and we lost the ability to focus on objects close at hand (presbyopia)

Question 41

Rods vs. cones

Answer 41

rods: more sensitive to very low intensities of light (provide high sensitivity B&W vision) cones: respond to diff wavelengths of light for color vision, provide sharpest vision (fovea only has cone cells)

Question 42

What kinds of cone cells do humans have?

Answer 42

1. one that absorbs violet and blue wavelengths 2. one that absorbs green 3. one that absorbs yellow and red

Question 43

What wavelengths can humans not see?

Answer 43

ultraviolet or infrared

Question 44

Why do squids and octpi might have a more logical eye design?

Answer 44

photoreceptors are the first thing the light hits > less light scattering > NO blind spot

Question 45

What do sensory systems represent?

Answer 45

What is important for survival and fitness; perception of changes or differences in the environment are emphasized