HSC Biology Marathon 2015 (7 Viewers)

[Mr_Kap]

What is an action potential? Explain why not all stimuli result in an action potential

 

[DepressedPenguino]

What is an action potential? Explain why not all stimuli result in an action potential

lol there are over 6 reasons. One of them is that the stimulus must be strong enough so that the threshold is reached. The threshold is the minimum of approximately 15mV depolarisation from the movement of sodium ions across the neurone's membrane. You can talk about the all are nothing concept of how if the threshold is not reached, an action potential will not be generated and hence the size of the stimulus is important .. blah blah.. relate this to not all stimulus resulting in action potential

 

[Mr_Kap]

lol there are over 6 reasons. One of them is that the stimulus must be strong enough so that the threshold is reached. The threshold is the minimum of approximately 15mV depolarisation from the movement of sodium ions across the neurone's membrane. You can talk about the all are nothing concept of how if the threshold is not reached, an action potential will not be generated and hence the size of the stimulus is important .. blah blah.. relate this to not all stimulus resulting in action potential

am i right saying that:

"An action potential is the firing of a neurone. This is either fully fired, or not fired at all; it is never semi-fired. If the stimulus is not strong enough then it does not reach the threshold, and an action potential can not be generated. This can be seen through graph: --> Show a graph of a stimulus not reaching threshold and then show stimulus reaching threshold. The threshold is the minimum of approximately 15mV depolarisation from the movement of sodium ions across the neurone's membrane."
Can an action potential not be generated due to nerve damage?

 

[DepressedPenguino]

am i right saying that:

"An action potential is the firing of a neurone. This is either fully fired, or not fired at all; it is never semi-fired. If the stimulus is not strong enough then it does not reach the threshold, and an action potential can not be generated. This can be seen through graph: --> Show a graph of a stimulus not reaching threshold and then show stimulus reaching threshold. The threshold is the minimum of approximately 15mV depolarisation from the movement of sodium ions across the neurone's membrane."
Can an action potential not be generated due to nerve damage?

Yeah nerve damage e.g. bruising. If you want to draw a graph, draw one that shows consecutive, identical action potentials being generated (you can should label how the first one exceeds the threshold just to reinforce your point)

 

[Mr_Kap]

Outline what renal dialysis is and identify the similarities and differences between kidney functioning and renal dialysis. 5 MARKS

 

[Flop21]

Outline what renal dialysis is and identify the similarities and differences between kidney functioning and renal dialysis. 5 MARKS

Renal dialysis is the artificial process to remove wastes from the blood, and is done when a person's kidney cannot undertake the process itself. It involves the patient's blood being filtered through dialysis fluid. As the blood passes through the dialysis fluid, the wastes diffuse through a semi-permeable membrane, and the clean blood is returned.

Renal dialysis and the normal kidney processes both involve the removal of nitrogenous wastes. They also both involve passive transport. However, normal kidney processes also involve active transport and renal dialysis does not. This means nutrients the body needs cannot be selectively reabsorbed into the blood and are lost through diffusion. Renal dialysis is also thus a much slower and less efficient process.

 

[Flop21]

Describe the differences in structure and distribution of the photoreceptor cells in the retina. (Would probably be 3 marks)

 

[DepressedPenguino]

Renal dialysis is the artificial process to remove wastes from the blood, and is done when a person's kidney cannot undertake the process itself. It involves the patient's blood being filtered through dialysis fluid. As the blood passes through the dialysis fluid, the wastes diffuse through a semi-permeable membrane, and the clean blood is returned.

Renal dialysis and the normal kidney processes both involve the removal of nitrogenous wastes. They also both involve passive transport. However, normal kidney processes also involve active transport and renal dialysis does not. This means nutrients the body needs cannot be selectively reabsorbed into the blood and are lost through diffusion. Renal dialysis is also thus a much slower and less efficient process.

Is that how renal dialysis works? I understood the process differently

 

[BlueGas]

Is that how renal dialysis works? I understood the process differently

How'd you understand it?

 

[Flop21]

Is that how renal dialysis works? I understood the process differently

It was a rough answer off the top of my head, but yes that is roughly how it works. There are two types of renal dialysis though. How did you think it works?

Looking at my notes, the correct terminology is - the blood passes through "dialysis tubing made of semi-permeable material". So my answer was unclear how the blood passes through the dialysis fluid, it is in tubing which is made of semi-permeable material.

Wastes diffuse out into the fluid.

 

[Queenroot]

am i right saying that:

"An action potential is the firing of a neurone. This is either fully fired, or not fired at all; it is never semi-fired. If the stimulus is not strong enough then it does not reach the threshold, and an action potential can not be generated. This can be seen through graph: --> Show a graph of a stimulus not reaching threshold and then show stimulus reaching threshold. The threshold is the minimum of approximately 15mV depolarisation from the movement of sodium ions across the neurone's membrane."
Can an action potential not be generated due to nerve damage?

You could word it differently. Semi-fired sounds kinda fucked tbh.

And usually if there's damage to a neuron, its threshold increases, so essentially you need a stronger stimulus to set one off.

 

[Loudvicuna]

An all or nothing phenomenon

 

[Mr_Kap]

Describe the differences in structure and distribution of the photoreceptor cells in the retina. (Would probably be 3 marks)

The two main types of photoreceptor cells in the retina are Rods (black and white) and Cones (colour). There are around 6 million cones in the eye, and are concentrated in the fovea where the image is detected in high resolution in colour, however there are a few around the periphery of the retina. Rods however are found in much greater numbers in the eye to cones, with around 125 million rods in the eye. They are also largely concentrated around the surface of the whole retina, and absent from the fovea. This is a direct opposite to the cones. Although their structures are very similar there is however one difference. This is the shape of the outer segment. In rods, this is rod shaped, while in cones it is cone shape.

 

[Queenroot]

The two main types of photoreceptor cells in the retina are Rods (colour) and Cones (black and white). There are around 6 million cones in the eye, and are concentrated in the fovea where the image is detected in high resolution in colour, however there are a few around the periphery of the retina. Rods however are found in much greater numbers in the eye to cones, with around 125 million rods in the eye. They are also largely concentrated around the surface of the whole retina, and absent from the fovea. This is a direct opposite to the cones. Although their structures are very similar there is however one difference. This is the shape of the outer segment. In rods, this is rod shaped, while in cones it is cone shape.

RIP

 

[Squar3root]

name all the organs in human body (15 marks)

 

[Mr_Kap]

RIP

SHIT.. it was a typo i swear. as you can see in the next sentence i say that cones are focused in the fovea where image is detected in high resolution in colour.

 

[Mr_Kap]

Shit. Just realised that something on the ear is asked EVERY YEAR in communication. AND hearing aids needed to be mentioned in HSC 2003 - 2006 and 2008-2013.
AND also cochlear implants appears as answers quite a lot

 

[BlueGas]

Explain why co-dominance does not produce simple Mendellian results. (2 marks)

 

[tfw english]

Explain why co-dominance does not produce simple Mendellian results. (2 marks)

Co-dominance is an incomplete dominance in which both alleles are expressed in the heterozygous form.
In co-dominance the hybrid showing a different phenotype means there are 3 possible phenotypes and Mendel’s 3:1 does not account for a third phenotype.

Is this alright? I'm not 100%

 

[BlueGas]

Co-dominance is an incomplete dominance in which both alleles are expressed in the heterozygous form.
In co-dominance the hybrid showing a different phenotype means there are 3 possible phenotypes and Mendel’s 3:1 does not account for a third phenotype.

Is this alright? I'm not 100%

Maybe not the full 2 marks, but what you gotta mention is that in dominant-recessive cases, the hetrozygous animal gives the dominant trait, whereas in co-dominance this is not the case, as the "hetrozygous" roan cow (RW) gives the "roan" colour.