HSC Biology Question Thread

[Diala]

Hi, I'm still finding it so confusing to differentiate between prevention and control. Different sites say different things... I was hoping to clear it all up. Do you have any suggestions as to how to remember the difference?

[Opengangs]

Hi, I'm still finding it so confusing to differentiate between prevention and control. Different sites say different things... I was hoping to clear it all up. Do you have any suggestions as to how to remember the difference?

Hey there!

Prevention and controlling disease are very similar by nature, but they're also very distinguishing aspects of disease! But the distinguishable aspect comes from its definition.

Preventing disease means that we stop the spread of disease. In the case of malaria, a preventative measure is that we wear long sleeves to avoid exposure from the Anopheles female mosquitoes. Prevention is usually done individually, so what can you do to avoid catching the disease?
Controlling, on the other hand, means that we regulate the spread of disease. This is usually done in favour of more than one person, so in order to regulate the spread of malaria (as our case study), we drain the mosquito breeding sites.

In summary: the main difference is that controlling includes prevention, but it covers a lot more than simply prevention. Prevention is just the personal protection side of controlling disease.

[Daniyahasan]

can someone please explain how renal dialysis works
i find it a difficult concept to grasp on

[Opengangs]

can someone please explain how renal dialysis works
i find it a difficult concept to grasp on

Hey there!

Renal dialysis is the artificial process of removing excess water and waste from the blood. It acts as a replacement to faulty kidneys, since people with faulty kidneys cannot perform the necessary actions needed to remove these excess water and waste. As a result, the use of renal dialysis is extremely important to this process.

Before understanding why this process is important, however, we need to consider how important of a role a kidney plays in our everyday lives. As we consume increased volumes of water, the role of the kidney is to "balance" out the mineral ions of potassium, calcium, sodium, and many more and maintain its equilibrium point. The acidic waste products are excreted by the kidneys. So, it is in your best interest to have functioning kidneys. Else, the internal pH of the blood decreases, leading to a denaturation of enzymes (remember that enzymes work at narrow pH levels).

In the case of kidney failures then, we need to develop some artificial process that works the same way a regular kidney does. This is known as renal dialysis. This works by diffusing solutes across a semi-permeable membrane. As a result, smaller solutes are able to pass through, leaving the larger solutes unfiltered (much like the glomerulus and Bowman's Capsule).

There are two types of dialysis:
Hemodialysis works by removing excess water and waste by circulating the blood from an external filter. This is called a dialyser, and it contains the semi-permeable membrane. As a result, the blood flow is one directional.

Peritoneal dialysis work by removing excess water and waste from the blood internally. The peritoneum acts as the semi-permeable membrane, and the waste is moved from the blood across the peritoneum into a dialysate.

[caitlinlddouglas]

hey i was wondering how having thick bark and sunken stomata reduces  water loss in plants? THanks 

[angelahchan]

hey i was wondering how having thick bark and sunken stomata reduces  water loss in plants? THanks 

Sunken stomata creates an area where water leaving the leaf can pool, keeping water in the leaf longer and decreasing the rate of transpiration, an example being the casuarina. Sorry, I don't have anything about thick bark in my notes, but from a quick google it seems thick bark is for fire prevention or something, e.g. during a fire the outer layer burns off protecting the cells inside. I'm not entirely sure though

[caitlinlddouglas]

thanks a lot !

Sunken stomata creates an area where water leaving the leaf can pool, keeping water in the leaf longer and decreasing the rate of transpiration, an example being the casuarina. Sorry, I don't have anything about thick bark in my notes, but from a quick google it seems thick bark is for fire prevention or something, e.g. during a fire the outer layer burns off protecting the cells inside. I'm not entirely sure though

[Daniyahasan]

Hey there!

Renal dialysis is the artificial process of removing excess water and waste from the blood. It acts as a replacement to faulty kidneys, since people with faulty kidneys cannot perform the necessary actions needed to remove these excess water and waste. As a result, the use of renal dialysis is extremely important to this process.

Before understanding why this process is important, however, we need to consider how important of a role a kidney plays in our everyday lives. As we consume increased volumes of water, the role of the kidney is to "balance" out the mineral ions of potassium, calcium, sodium, and many more and maintain its equilibrium point. The acidic waste products are excreted by the kidneys. So, it is in your best interest to have functioning kidneys. Else, the internal pH of the blood decreases, leading to a denaturation of enzymes (remember that enzymes work at narrow pH levels).

In the case of kidney failures then, we need to develop some artificial process that works the same way a regular kidney does. This is known as renal dialysis. This works by diffusing solutes across a semi-permeable membrane. As a result, smaller solutes are able to pass through, leaving the larger solutes unfiltered (much like the glomerulus and Bowman's Capsule).

There are two types of dialysis:
Hemodialysis works by removing excess water and waste by circulating the blood from an external filter. This is called a dialyser, and it contains the semi-permeable membrane. As a result, the blood flow is one directional.

Peritoneal dialysis work by removing excess water and waste from the blood internally. The peritoneum acts as the semi-permeable membrane, and the waste is moved from the blood across the peritoneum into a dialysate.

Oh wow thanks soo muchh

[Mounica]

can someone please explain action potential and threshold i do not understand that at all

[Natasha.97]

can someone please explain action potential and threshold i do not understand that at all

Hi!
Threshold: Minimum strength of a stimulus needed to begin an action potential (-55mV). If it is not reached, then the stimulus is not strong enough to generate it
Action potential: Generation of electrical impulses

Summary:
•   At rest (-70mV): Cl^- and K⁺ ions are inside axon, Na⁺ ions are outside, protein channels are closed
•   Strong nervous impulse: Na⁺ channels open, ions enter.
•   Threshold (-55mV) reached: Remaining Na⁺ ions flow into the axon through channels (depolarisation)
•   Na⁺ and K⁺ are pumped back out of the axon, potential is becoming negative (repolarisation)
•   Loss of both positive ions results in a potential less than -70mV
•   Na⁺ channels close, K⁺ ions move back into the axon and their channels close, reaching resting potential (-70mV)

Hope this helps

[Daniyahasan]

hey,
does anyone know any websites that has topic tests for search for better health?

[angelahchan]

hey,
does anyone know any websites that has topic tests for search for better health?

hscninja.com used to have a consolidated quiz mode where you could select a topic and they'd pick past questions for you to do. unfortunately bostes made them take it down because copyright, but they still have past questions sorted by topic.  If you want, you can buy the success one HSC biology book which has the  2001-2005 sorted by topic rather than by paper

[pikachu975]

can someone please explain action potential and threshold i do not understand that at all

1) Resting membrane potential of -70 mV.
2) A stimulus occurs which causes depolarisation if the threshold of -55 mV is met, i.e. voltage-gated sodium ion channels open so sodium ions rush in the axon which causes membrane potential to change to around +40 mV.
3) Repolarisation occurs where sodium ion channels close and potassium ion channels open, causing potassium to rush out. This makes the membrane potential down to -75 mV.
4) Since it is too negative, repolarisation occurs which means that all ion channels close and the sodium-potassium pump balances the membrane potential to -70 mV, also known as the refractory period.

[caitlinlddouglas]

Hey for Communication, I didn't really understand what it means by rods having high retinal convergence  causing them to have poor visual clarity. Thanks

[Mathew587]

Hey for Communication, I didn't really understand what it means by rods having high retinal convergence  causing them to have poor visual clarity. Thanks

Rod cells are found in bunches of thousands and are attached to a single nerve cell, resulting in high retinal convergence, consequently also resulting in poorer vision acuity. This coupled with the ability of rod cells to only distinguish between dark and light results in them to have poor visual acuity. In contrast, cone cells are each attached to a single nerve cell which coupled with their ability to distinguish colour results in them having higher visual acuity.