Bio Q?

[HannibalLecter]

In contrast to electrical synapses, chemical synapses are:

A) the site of bidirectional communication between neurons
B) the site of unidirectional communication between neurons
C) gap junctions that contain protein channels
D) far more common in embryonic nervous tissue
E) more abundant in cardiac muscle fibers to permit rhythmic excitation

I thought it was A:

Reasoning:

Chemical synapse is bidirectional: When a chemical is released in the synapse, it can act on the post synaptic cell and in some circumstances if is not degraded it can come act on the pre synaptic cell and turn it off from firing any more synaptic vesicles thus starting a new potential.

Electrical synapse is unidirectional: When the neuron is stimulated and goes through an action potential, it has a refractory period where the NA and K channels balance out the membrane potential again. Where it can't fire another one or it cant go the other way because all the action potentials behind it are refracted.

Get what I'm saying or you don't know what the Rock is cooking?

Happy 5th everyone

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[HannibalLecter]

And one more,

Bat wings, bird wings, and bee wings arose through ___________ evolution. They are said to be ________ structures.

A. convergent, homologous
B. convergent, analogous
C. divergent, homologous
D. divergent, analagous
E. homologous, analagous

WTF I thought wings in birds evolved convergent-ly because they are all birds. They would have the same function because they use it to fly. The answer is B to this one but I said C.

And, not trying troll on the previous question but the answer for that was B and I wrote down C.

 

[AlbinoPolarBear]

And one more,

Bat wings, bird wings, and bee wings arose through ___________ evolution. They are said to be ________ structures.

A. convergent, homologous
B. convergent, analogous
C. divergent, homologous
D. divergent, analagous
E. homologous, analagous

WTF I thought wings in birds evolved convergent-ly because they are all birds. They would have the same function because they use it to fly. The answer is B to this one but I said C.

Convergent evolution is when you have structures that originate from different groups of animals, but then evolved to be used for the same purpose. In this case, a mammal (bat), a bird and an insect (bee) have structures that require it to fly. 3 different sources of origin, but performs the same function. And of course, these are analogous structures because of the same reasoning.

 

[Polk]

In contrast to electrical synapses, chemical synapses are:

A) the site of bidirectional communication between neurons
B) the site of unidirectional communication between neurons
C) gap junctions that contain protein channels
D) far more common in embryonic nervous tissue
E) more abundant in cardiac muscle fibers to permit rhythmic excitation

I thought it was A:

Reasoning:

Chemical synapse is bidirectional: When a chemical is released in the synapse, it can act on the post synaptic cell and in some circumstances if is not degraded it can come act on the pre synaptic cell and turn it off from firing any more synaptic vesicles thus starting a new potential.

Electrical synapse is unidirectional: When the neuron is stimulated and goes through an action potential, it has a refractory period where the NA and K channels balance out the membrane potential again. Where it can't fire another one or it cant go the other way because all the action potentials behind it are refracted.

Get what I'm saying or you don't know what the Rock is cooking?

Happy 5th everyone

I believe it is B because the post synaptic cell does not act on the presynaptic. The transmitter acting on the pre to stop production is just a feedback mechanism.

 

[LetsGo2DSchool]

And one more,

Bat wings, bird wings, and bee wings arose through ___________ evolution. They are said to be ________ structures.

A. convergent, homologous
B. convergent, analogous
C. divergent, homologous
D. divergent, analagous
E. homologous, analagous

WTF I thought wings in birds evolved convergent-ly because they are all birds. They would have the same function because they use it to fly. The answer is B to this one but I said C.

And, not trying troll on the previous question but the answer for that was B and I wrote down C.

I used to get these mixed up too by using common sense and logic (i.e. a bat/bird/bees wings are very similar so they must be homologous -- from the same ancestor). But then I started to think like a sneaky test maker and realized these c*cksuckers wouldn't be asking questions that could easily be answered with common sense logic or everyone would get them correct.

Thus, if you see very similar structures such as a bird/insect/mammal wings, it's always analogous structure from different ancestors, which means it has to be convergent evolution.

On the other hand, if the structures are remotely similar (i.e. whale's flipper, animal's arm) then they are analogous from the same ancestor, which means it has to be divergent evolution.

In sum, group the opposites together:

analogous (different ancestors) & convergent (to same one)

homologous (same ancestors) & divergent (to different ones)

If you use this "opposite" rule of thumb, you will get this answer question correct every time.

 

[HannibalLecter]

In this case, a mammal (bat), a bird and an insect (bee) have structures that require it to fly.

HAHAHA thats just a slap in the face if I didn't remember that. Oh wow my reasoning was way off. Good job albino that was a very good explanation and understand it well now

I believe it is B because the post synaptic cell does not act on the presynaptic. The transmitter acting on the pre to stop production is just a feedback mechanism.

I guess I understand the unidirectionality of chemical synapses but my next question would be why is the electrical synapse labeled as a bidirectional form of movement?

And thanks D school your input was cool too

 

[BerrF12]

Where are these questions from?

 

[HannibalLecter]

Barrons DAT Book

 

[jwnichols21]

I used to get these mixed up too by using common sense and logic (i.e. a bat/bird/bees wings are very similar so they must be homologous -- from the same ancestor). But then I started to think like a sneaky test maker and realized these c*cksuckers wouldn't be asking questions that could easily be answered with common sense logic or everyone would get them correct.

Thus, if you see very similar structures such as a bird/insect/mammal wings, it's always analogous structure from different ancestors, which means it has to be convergent evolution.

On the other hand, if the structures are remotely similar (i.e. whale's flipper, animal's arm) then they are analogous from the same ancestor, which means it has to be divergent evolution.

In sum, group the opposites together:

analogous (different ancestors) & convergent (to same one)

homologous (same ancestors) & divergent (to different ones)

If you use this "opposite" rule of thumb, you will get this answer question correct every time.

Thank you for this. Was confused on this concept but your little trick is now enframed in my brain. Or at least let's hope so.

 

[jmukid]

Ok i might sound dumb but the human arm and bat wing are divergent structures and homologous ancesters right?

 

[LetsGo2DSchool]

Ok i might sound dumb but the human arm and bat wing are divergent structures and homologous ancesters right?

Here's a fool-proof 2-step approach which works every time for me:

1. Divergent or convergent evolution? (divergent = from same ancestor, or convergent = different ancestors)
2. If divergent, then it's homologous structures (think homologous = same ancestor). If convergent, then it's analogous structures (think analogous = different ancestors).

Examples:
A bee wing, bat wing, bird wing. Convergent evolution. Different ancestors. Must be analogous structures.

A human arm, bat wing, whale flipper. Divergent evolution. Same ancestor. Must be homologous structures.

 

[TheDentist16]

Where are these questions from?

I also came across these same questions in DAT Destroyer bio section.

 

[jmukid]

Here's a fool-proof 2-step approach which works every time for me:

1. Divergent or convergent evolution? (divergent = from same ancestor, or convergent = different ancestors)
2. If divergent, then it's homologous structures (think homologous = same ancestor). If convergent, then it's analogous structures (think analogous = different ancestors).

Examples:
A bee wing, bat wing, bird wing. Convergent evolution. Different ancestors. Must be analogous structures.

A human arm, bat wing, whale flipper. Divergent evolution. Same ancestor. Must be homologous structures.

oh alright gotcha, thanks

 

[jwnichols21]

Here's a fool-proof 2-step approach which works every time for me:

1. Divergent or convergent evolution? (divergent = from same ancestor, or convergent = different ancestors)
2. If divergent, then it's homologous structures (think homologous = same ancestor). If convergent, then it's analogous structures (think analogous = different ancestors).

Examples:
A bee wing, bat wing, bird wing. Convergent evolution. Different ancestors. Must be analogous structures.

A human arm, bat wing, whale flipper. Divergent evolution. Same ancestor. Must be homologous structures.

This makes sense, but now I'm having trouble determining if the organisms they give us are from the same ancestor or not; is this a taxonomy thing where we must know which animals come from the same ancestor? Or is there a trick, because they could throw some obscure organism our way and we may not know if it has a common ancestor with the one it's listed with.

 

[AlbinoPolarBear]

This makes sense, but now I'm having trouble determining if the organisms they give us are from the same ancestor or not; is this a taxonomy thing where we must know which animals come from the same ancestor? Or is there a trick, because they could throw some obscure organism our way and we may not know if it has a common ancestor with the one it's listed with.

Well, at the very least, you should which organisms are insects, amphibians, reptiles, birds or mammals.

Same purpose, different ancestors:
Bee wing = insect's wing
Bat wing = mammal's wing
Bird wing = bird's wing


Different purpose, same ancestors:
Human arm = mammal's arm
Bat wing = mammal's wing
Whale flipper = mammal's flippers

 

[GeneralChowFun]

HAHAHA thats just a slap in the face if I didn't remember that. Oh wow my reasoning was way off. Good job albino that was a very good explanation and understand it well now



I guess I understand the unidirectionality of chemical synapses but my next question would be why is the electrical synapse labeled as a bidirectional form of movement?

And thanks D school your input was cool too

Electrical synapses only exist in one place in the body, cardiac muscle cells. They are essentially gap junctions between the two muscle cells. Gap junctions allow small ions to travel via diffusion between cells. The reason it is considered bidirectional is because positive ions (part of a wave of depolarization) can go through either side of the gap junction because it is basically a big hole with diffusion driving the directionality.
Chemical synapse involve a pre-synaptic cell releasing/secreting neurotransmitter which binds a receptor on the surface of the post-synaptic cell. Depending on the type of neurotransmitter, it can have a stimulatory or inhibitory effect on the post-synaptic cell.
The reason this is considered unidirectional is because the impulse travels from the axon terminus of the pre-syn. cell to dendrites/soma/cell body of the post-syn. cell. It can never go backwards i.e. you can never have the impulse travel from the dendrites/soma/cell body of the post-syn. cell to the axon terminus of the pre-syn. cell. However, with gap junctions being ion-specific holes, the movement of ions can go in either direction depending on the driving "force" of diffusion.
Cool question. Hope that helps. Best of luck.