3.1 State ONE change in the nerve tissue of the brain that can cause Alzheimer's disease - NSC Life Sciences - Question 3 - 2023 - Paper 1

A symptom of Alzheimer's disease is the worsening ability to remember new information.

A genetic risk factor for Alzheimer's disease is family history.

One function of the hippocampus is to support learning ability, while another function is to orient as it helps in maintaining spatial awareness.

The participants were selected based on being between the ages of 65 and 75, and they did not show any symptoms of Alzheimer's disease.

This investigation could not establish a relationship because there was no control group that could help determine how exercise affected blood flow and higher-order thinking abilities, as the participants who did not show symptoms were used in the study.

Exercise increases blood flow to the brain, which can maintain the volume of the hippocampus. This is critical because it helps prevent cognitive decline, which includes higher-order thinking and learning capabilities.

Organ X is the kidney.

The adrenal gland belongs to the endocrine system.

The glands of the endocrine system release hormones directly into the blood and are ductless.

When salt levels are low, receptor cells in the kidney are stimulated, leading the adrenal glands to secrete more aldosterone. This hormone increases the reabsorption of salt in the renal tubules, which helps to restore normal blood salt levels.

When a person experiences dehydration, the secretion of ADH (antidiuretic hormone) from the pituitary gland increases. This will increase the permeability of the renal tubules in organ X (the kidney), allowing more water to be reabsorbed from the filtrate back into the bloodstream.

The homeostatic mechanism that brings about the change in skin temperature is thermoregulation.

The part of the brain responsible for this mechanism is the hypothalamus.

Part P is the sweat gland.

Part Q is the capillary or blood vessel.

The average skin temperature of the boy before exercise was 37.4°C and directly after exercise was 35.4°C. The percentage decrease is calculated as follows:

$ext{Percentage Decrease} = \frac{37.4 - 35.4}{37.4} \times 100 = 5.35\%$

Part P (the sweat gland) increases sweat production when the body temperature rises, helping cool the body through evaporation. Part Q (the capillary or blood vessel) dilates, increasing blood flow to the skin's surface, which facilitates heat loss through radiation and convection.

The independent variable in this investigation is the presence or absence of auxins.

The dependent variable is the growth of lateral branches.

All the plants were exposed to the same environmental conditions to ensure that the results were caused only by the presence of auxins, thereby increasing the validity of the investigation.

Agar without auxins was used in plant C to serve as a control, ensuring that any observed growth could be attributed solely to the presence of auxins in the agar used for plant D.

The presence of auxins stimulates the growth of lateral branches, or conversely, the absence of auxins inhibits their growth.