Anatomy B/C

[darkdeserthighway]

Sucks, doesn't it?
Which system is next? I think respiratory.

From what I've heard, the systems for Anatomy rotate every two years. Nervous system has been here for last year (2013) and this year (2014), so I doubt it will serve again next year.
I hope I'm wrong though. Nervous system is the best.

Unbelievable.. I hope you're wrong, too.

[Flavorflav]

I'm pretty sure respiratory just went out a couple of years ago. I think next should be circulatory.
IIRC, it's gone circulatory, skeletal, muscular, endocrine, respiratory, digestive, excretory, nervous, immune and integumentary, in that order. Sometimes two new ones come in together.

[Mortem_Haedo]

I'm pretty sure respiratory just went out a couple of years ago. I think next should be circulatory.
IIRC, it's gone circulatory, skeletal, muscular, endocrine, respiratory, digestive, excretory, nervous, immune and integumentary, in that order. Sometimes two new ones come in together.

Thanks! I've been looking all over for what I should prepare for next year ^_^

[emescferrall]

Nervous is always there, isn't it??

[mej710]

No, I'm pretty sure the nervous system was new when I started doing the Anatomy event two years ago.

[Unome]

Nothing is always there, I saw the listings for the past few years. I know in Div B they rotate after 2 years (I'm hoping for Muscular next year ).

[fanjiatian]

Could you guys help explain how a impulse works, with the Na+ and K+ transfer? I don't get it

Basically, when a neuron is at resting membrane potential, there is a higher concentration of Na+ ions outside the cell and a higher concentration of K+ ions inside the cell. However, there are fewer ions inside making it less positive or more negative. This means the cell is polarized when it is more negative inside. The action potential is the electrical current that travels through the neuron when it is stimulated. The minimum stimulus needed to achieve action potential is called the threshold stimulus. When a stimulus is received by the neuron, the Na+ gates open and because it is less negative on the inside of the cell and more positive on the outside, the Na+ ions come rushing into the cell. This is called depolarization because it makes the inside of the cell more positive than the outside. Then, the K+ gates open and K+ rushes out of the cell. This is called repolarization. At this point, the neuron is back to being more negative on the inside and more positive on the outside. However, Na+ is concentrated inside the cell and K+ is concentrated outside, which is the opposite of where they were concentrated when the cell was at resting membrane potential. So the Na+/K+ pump, with the help of ATP, pumps 3 Na+ ions out of the cell for every 2 K+ pumped in until the ion concentration on the inside and outside are back to normal.

That was a really good summary! I get that the pump restores the resting concentration of ions, but how does the potential beome less negative after hyperpolarization? If you remove 3 Na+ and add 2K+, the net effect is the loss of one positive charge on the inside right? That's the only thing I'm confused about

[fanjiatian]

I saw a question on a test that asked for the reason for gray hair.

I thought it was accumulation of air bubbles, but the answer key said decreased melanocyte activity. Which has a greater effect?

[mej710]

Could you guys help explain how a impulse works, with the Na+ and K+ transfer? I don't get it

Basically, when a neuron is at resting membrane potential, there is a higher concentration of Na+ ions outside the cell and a higher concentration of K+ ions inside the cell. However, there are fewer ions inside making it less positive or more negative. This means the cell is polarized when it is more negative inside. The action potential is the electrical current that travels through the neuron when it is stimulated. The minimum stimulus needed to achieve action potential is called the threshold stimulus. When a stimulus is received by the neuron, the Na+ gates open and because it is less negative on the inside of the cell and more positive on the outside, the Na+ ions come rushing into the cell. This is called depolarization because it makes the inside of the cell more positive than the outside. Then, the K+ gates open and K+ rushes out of the cell. This is called repolarization. At this point, the neuron is back to being more negative on the inside and more positive on the outside. However, Na+ is concentrated inside the cell and K+ is concentrated outside, which is the opposite of where they were concentrated when the cell was at resting membrane potential. So the Na+/K+ pump, with the help of ATP, pumps 3 Na+ ions out of the cell for every 2 K+ pumped in until the ion concentration on the inside and outside are back to normal.

That was a really good summary! I get that the pump restores the resting concentration of ions, but how does the potential beome less negative after hyperpolarization? If you remove 3 Na+ and add 2K+, the net effect is the loss of one positive charge on the inside right? That's the only thing I'm confused about

I think it becomes less negative after hyperpolarization because the K+ channels are still open, so there are some additional positive ions coming in. I know hyperpolarization creates a charge of about -90mV so maybe at that point, the Na+/K+ pump stops and the K+ channels close after the charge is back down to -70mV.

[mej710]

I saw a question on a test that asked for the reason for gray hair.

I thought it was accumulation of air bubbles, but the answer key said decreased melanocyte activity. Which has a greater effect?

When melanocyte activity is decreased, there is less melanin being produced, so less pigment. The melanin is just replaced by air bubbles so when there is less melanin, there are more bubbles.