Nervous System II

Question 1

Why do small fish have rapid responses to local water disturbances? What species exploits this response and how? What experiment was done to test this? Where does Tinbergen Lorenz behavior parts play a part?

Answer 1

1. 2 large neurons on either side of body that detect disturbance –> turning of opposite side of body
2. Tentacled snake - sets up a C shape in middle of its body so fish turns away from C into the jaws
3. Have snake on top of glass with fish, turns out they elicit the behavior without ever learning it, so it doesn’t need to be learned.
4. Sign stimulus - fish presence, FA - vibrations and striking, IRM - vibration by neural patterns

Question 2

What is an example of how prey distinguish between predators and conspecifics? Elaborate. How is this behavior shown? What neural mechanism causes this behavior?

Answer 2

1. Crickets - attracted to songs around 5kHz, repulsed by louder sounds
2. 5kHz = tilt butt towards the sound, 40 kHz = tilt butt away and lift legs (leads to further veering)
3. Interneurons

Question 3

What is a central pattern generator? What is an example? What are the two pathways that drive this behavior?

Answer 3

1. A system that will work by itself so long as it is on (breathing/swimming/walking) that can be manipulated by sensory input
2. Sea slugs swimming away from starfish -
3. DSI smells starfish –> C2 act. –> Dorsal flexion –> off

C2 –> Ventral SI –> VFN –> off –> C2

Question 4

What is an example of a central pattern generator in humans? Where is this turned on? Loggerhead turtles?

Answer 4

1. Swallowing (25 muscles)
2. medulla oblongata (brainstem because we think about when we want to swallow)
3. “swim” if suspended in the air

Question 5

What is umwelt? What is an example of magnetic sense? Two examples of UV vision? What is polarized light? What is an example of umwelt for this?

Answer 5

1. representation of the world is different between organisms because they’re perceiving the world in different ways that are efficient for them
2. Reed warblers - magnetic sense (broad map using magnetic poles, so location isn’t exact, but magnetic field is pretty close)
3. Sticklebacks - use UV on males for mating (take away UV she’s no longer attracted to him), Monarch butterflies - Use UV light from the sun to determine location when migrating (because one butterflies never completes one cycle, they die).
4. Atmosphere polarizes light (more on one side than another). polarization filters out photons travelling at certain angles (1 photon = 1 direction, many = 360 degrees)
5. Monarch butterflies

Question 6

Why can humans not detect polarized light? How does the system work to detect polarized light in a body?

Answer 6

1. All animals have single cell rhodopsin (rods/cones) (ciliary photoR’s) AND this rhodopsin has no orientation (sits in a random direction) so there is no specific orientation to polarize light in our eyes
2. Invertebrates use narrow tubes called rhabdomeric photoreceptors that orient the pigments so that way they are in a single direction –> sensitivity to polarized light

Question 7

What are the three properties of a magnetic field at a single location?

Answer 7

1. Declination - horizontal angle from north
2. Inclination - vertical angle
3. Intensity - how strong the field is