The Ultimate Year 12 Biology Test

Homeostasis refers to the body's ability to maintain a stable internal environment despite external fluctuations. This includes regulating temperature, pH levels, and other physiological variables within a narrow range. It is crucial for the proper functioning of cells, tissues, and organs. The body achieves homeostasis through various mechanisms, such as feedback loops and hormonal control, which help to restore balance and ensure optimal conditions for the body's cells to function properly.

Red blood cells have a name which gives it away, as haemoglobin is a red pigment. White blood cells patrol the body. Platelets are chunks of cells broken off from a big cell called a megakaryocyte and fixes blood vessel ruptures by clotting blood there. If you watch Cells At Work, you'll know this very well.

self-explanatory

Positive feedback takes in stimulus to reinforce a process until it reaches an end point. This means that when a certain stimulus is received, it leads to an amplification or increase in the process, pushing it towards completion or an endpoint. On the other hand, negative feedback draws on stimulus to alter the process until it falls back into normal limits. This means that when a certain stimulus is received, it leads to a response that counteracts the stimulus, bringing the process back to its normal range or limits.

Honestly if you didn't get this one, I'd like to ask how you even passed the last two terms of year 12 biology.

The endocrine system is composed of several glands which all secrete different hormones. These hormones travel in the blood stream to the target cells of which they'll act upon. Hormones affect the physiological function of a cell in one way. To maintain homeostasis, an antagonistic hormone may also be secreted to counter the affect of a hormone to achieve an opposite effect.

Oxygen and carbon dioxide is exchanged through diffusion between the one-cell thick ducts and capillaries.

Sensory neurons receive external stimuli and converts them into internal electrical impulses. The relay neuron connects the impulses received from the sensory neuron and relays them to the motor neuron, which causes the effector to act.

Ca2+ channels play a vital role in nerve relays because the influx of calcium ions allow neurotransmitters to do their job.

Neurotransmitters are deactivated soon after release to ensure that the signal can be controlled and stopped after it is transmitted. This allows for precise regulation of neuronal communication and prevents continuous stimulation or overexcitation of the receiving cells. By deactivating neurotransmitters, the nervous system can maintain proper signaling and prevent excessive or prolonged activation, which could lead to detrimental effects on the body.

ADH increases the permeability of the tubules in the nephron, so water is more easily absorbed back into the blood stream. This creates more concentrated urine. Yes, that also means you pee less, but low amount of urination can be due to other reasons too.

When you breathe in, the diaphragm contracts and moves down. This expands the volume of the lungs.

Haemoglobin has a quaternary structure. It can carry up to 4 oxygen molecules at once.

In the endocrine system, the hypothalamus detects changes all around the body. This means that it is very important in maintaining various functions around the body. Once it detects something is off, it sends a message to the pituitary gland. The pituitary gland sends out many different types of hormones that are needed in body regulation.

Both the SoNS and the ANS are under the peripheral nervous system. The SoNS is associated with voluntary functions (like moving your hand) while the ANS is associated with visceral functions (a boner).

When you drive, you must step on the gas pedal to accelerate your car to near the appropriate speed limit. If your speed exceeds it however, you would let go of the gas pedal to allow the car to slow down. Once you're beginning to be too slow, you start it again. This is an example of negative feedback.

Just like being cramped in the hall, once the door opens, people would be more inclined to rush out into the open area.

Next question will get you to name their functions, have fun ;)

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More specifically, the gases are carried by red blood cells which are DISSOLVED into the blood.

Blood enters the kidney through the renal artery. It then reaches the medulla pyramids. That's where all the filtration happens. After that, the urine is collected and transported into the bladder through the ureter. The filtered blood leaves through the renal vein.

Because of a concentration gradient, water and salts move passively. In the descending limb, the very salty external environment causes water to be drawn out. As the loop moves up and back into the less salty area (cortex), salt leaves.

The glomerulus and bowman's capsule is the beginning of the urine-production process. There, blood enters through the afferent arteriole. It then exits through the efferent arteriole and coils around the whole nephron before leaving through the renal vein as filtered blood. A way to remember the difference is that the afferent arteriole transports blood that will be AFFECTED by the process, and the efferent arteriole transports blood that is already EFFECTED by filtration. Henle's loop doesn't filter much, but rather deals with salt and water levels. For the convoluted tubules, the proximal convoluted tubules does most of the re-absorption work as opposed to the distal convoluted tubule. A way to remember the difference is that "proximal" means close by (to the glomerulus) and "distal" means far away.

The CNS and PNS aren't separated by voluntary and involuntary responses because they both do that. The main difference is just the components that make up the systems.

The cell body encompasses the nucleus of the cell. Dendrites branch out from there and receive messages. The axon refers to the 'channel', which are insulated by Schwann cells that form the Myelin Sheath. The gaps in between are called Nodes of Ranvier. At the end of the axon is the axon terminal.

The presynaptic terminal is the end of the first neuron. The impulse travels down the axon and into the synaptic vesicle, where neurotransmitters transmit the message in chemical form. Passing a gap called a synaptic cleft, the chemical message reaches the receptor region, which converts the message back into electric form. This then moves along the axon and reaches the post-synaptic terminal and it starts again.

We all know what adult haemoglobin is. Myoglobin acts as reserves in muscles for when strenuous exercise happens and extra oxygen is needed. Therefore, it's oxygen affinity is very high. Foetal haemoglobin has higher oxygen affinity levels than adults because this will allow oxygen travelling in the mother's blood stream to diffuse into the fetus. Otherwise, the fetus won't receive any oxygen.

All the following actions enable the body to increase the rate of gas exchange, which will remove carbon dioxide from the body faster.

ADH causes the body to retain water, which may happen if the body feels their water level is low. Perspiration causes the body to lose a lot of water. A low blood pressure can result due to low water level in the blood plasma, and not drinking water regularly will cause the body to be unable to replenish fluid levels. Drink up!

Carbon dioxide reacts with water to make carbonic acid. This stuff is of course in the blood stream and therefore makes blood acidic.

Once a neuron receives a stimulus, it undergoes depolarisation, which causes the cell to lose its negative charge. After a certain point, the cell repolarises and falls back to a negative charge again. However, it typically overshoots, resulting in a hyperpolarisation. This is a temporary period of time where the nerve isn't ready to receive another signal. The charge then returns back to its normal level.

The nervous system sends electric messages through nerves that run along the body. They're rapid, just like electricity cables in the city. As soon as you turn the TV on, it instantly turns on. The endocrine system is more like city piping, where it's fast, but not as fast. The endocrine system's hormones travel through the blood stream.

A reflex arc happens involuntarily, without conscious thought. During the arc, the message is relayed to the receptor and passes through the sensory neuron, then the relay neuron, then directly to the motor neuron and effector. Of course, the brain will still get a message of what's going on, but it won't be immediately and won't affect the reflex arc because it's already done.

Despite what it feels like, breathing isn't a matter of sucking air in or blowing it out. The air flow is manipulated through pressure differences. Increasing the volume of the lungs makes them have lower air pressure. Because air will travel from places with high pressure to places with low pressure, the air will invite itself into your lungs. The opposite happens when you exhale, where you squeeze your lungs smaller so the air leaves.

Both arteries and veins have elastin, but this is of course thicker in arteries.

The excretory system includes the lower part of the digestive tract (intestines and downwards), and also the urinary tract, which includes the kidneys, bladder and erethra. Although urine can come out the penis, it technically isn't included into the body system.

The upper respiratory tract consists of the nose (and also the oral cavity, cause you can breathe in through your mouth too), larynx (aka voice box) and then the trachea. The lower respiratory tract consists of the lungs, which are joined by bronchus, that split smaller and smaller till it reaches the alveoli. The diaphragm sits below the lungs.