Homeostasis: notes and practice questions

Living organisms must maintain a stable internal environment, a process known as homeostasis.

(a) Explain the control of blood glucose concentration in humans.

(b) Explain the effect of pH on the activity of enzymes.

(c) Distinguish between the transport of glucose and oxygen in the blood, with reference to the properties of water.

A group of volunteers participated in an Arctic expedition where they were exposed to extreme cold. During the expedition, their core body temperatures and blood glucose concentrations were continuously monitored.

Compare the roles of insulin and glucagon in regulating the volunteers' blood glucose concentrations.

One of the volunteers was previously diagnosed with Type 2 diabetes. Distinguish between Type 1 and Type 2 diabetes.

Outline the roles of muscle and adipose tissue in the physiological responses used by the volunteers to maintain their core body temperature.

The circulatory system transports essential substances, including hormones, which are vital for maintaining a stable internal environment (homeostasis).

(a) Outline how the structures of arteries and capillaries are related to their functions.

(b) Explain the roles of insulin and glucagon in the homeostatic control of blood glucose concentration.

(c) Discuss the causes and treatments for type 2 diabetes.

Thermoregulation is a key homeostatic process. A study investigated the response of human participants to a cold environment ($10^\circ\text{C}$). Participants were divided into two groups: one group remained at rest, while the other performed moderate exercise on a stationary bicycle. Core body temperature was measured every 15 minutes for two hours.

![Line graph showing core body temperature (°C)

over 120 minutes for two groups: Resting and Exercising. The y-axis is Core Body Temperature (°C) from 36.5 to 37.5. The x-axis is Time (minutes) from 0 to 120. Both groups start at 37.0°C. The Resting line shows a steady decline to about 36.6°C. The Exercising line shows a very slight initial dip, then rises to about 37.2°C and remains stable.](https://jujwjkjdeuwpscvsbilk.supabase.co/storage/v1/object/public/question-images/b242d1e2-5cff-4548-9da6-249648b0b274/1791279084335.png){width="3.6in"}

(a) Describe the trend in core body temperature for the exercising group.

(b) Compare the core body temperature in the resting group with the exercising group over the 120-minute period.

(c) Suggest a reason for the difference in core body temperature observed between the two groups.

(d) The resting group then underwent a 10-week cold acclimatization program, involving regular, controlled exposure to cold. Their core body temperature response to the same cold environment ($10^\circ\text{C}$) at rest was measured again.

![Line graph comparing core body temperature (°C)

over 120 minutes for the same group Pre-acclimatization and Post-acclimatization. The y-axis is Core Body Temperature (°C) from 36.5 to 37.5. The x-axis is Time (minutes) from 0 to 120. Both lines start at 37.0°C. The Pre-acclimatization line shows a steady decline to 36.6°C. The Post-acclimatization line shows a much smaller decline, stabilizing around 36.9°C.](https://jujwjkjdeuwpscvsbilk.supabase.co/storage/v1/object/public/question-images/b242d1e2-5cff-4548-9da6-249648b0b274/1791279066631.png){width="3.6in"}

Distinguish between the results pre- and post-acclimatization.

(e) Suggest why participants were required to rest in a thermoneutral room ($24^\circ\text{C}$) for 30 minutes before each experimental trial.

(f) The study also measured the resting metabolic rate of the participants before and after the acclimatization program.

![Bar chart showing Resting Metabolic Rate (mL O2 kg⁻¹ min⁻¹)

Pre-acclimatization and Post-acclimatization. The y-axis is Resting Metabolic Rate. The Pre-acclimatization bar is lower than the Post-acclimatization bar. Error bars are shown.](https://jujwjkjdeuwpscvsbilk.supabase.co/storage/v1/object/public/question-images/b242d1e2-5cff-4548-9da6-249648b0b274/1791279048041.png){width="3.6in"}

Describe the difference in resting metabolic rate before and after the program.

(g) Suggest how an increased resting metabolic rate might contribute to the improved tolerance to cold shown in part (d).

(h) The hormone thyroxin is involved in regulating metabolic rate. Outline the role of thyroxin in thermoregulation.

(a) The graph shows the results of an experiment in which the oxygen consumption rate of deer mice (Peromyscus maniculatus) was measured at various environmental temperatures from $-5~^\circ\text{C}$ to $35~^\circ\text{C}$. Between $-5~^\circ\text{C}$ and $30~^\circ\text{C}$, the mice maintained a constant core body temperature, but above $30~^\circ\text{C}$ their body temperature increased.

Describe the relationship between environmental temperature and oxygen consumption rate in the deer mice.

(b) Explain the change in oxygen consumption rate as the environmental temperature drops from $20~^\circ\text{C}$ to $-5~^\circ\text{C}$.

(c) Suggest a reason for the change in oxygen consumption rate as environmental temperatures increased from $30~^\circ\text{C}$ to $35~^\circ\text{C}$.

(d) Suggest two reasons for the variation in oxygen consumption rate between individual mice at each environmental temperature.