Anatomy and Physiology of Animals/Endocrine System/Test Yourself Answers

1. What is Homeostasis?


 * Homeostasis is maintaining stability/constant conditions despite changes in the environment.

2. Give 2 examples of homeostasis.


 * Examples of homeostasis in an animal’s body are the maintenance of a constant internal temperature despite fluctuations in the air temperature, mechanisms that keep the concentration of the internal fluids constant despite changes in the diet or fluid intake, mechanisms that compensate for blood loss and mechanisms that maintain a constant internal acid/base balance or pH.

3. List 3 ways in which animals keep their body temperature constant when the weather is hot.


 * Animals keep their body temperature constant when the weather is hot by keeping out of the sun, keeping activity to the minimum, sweating, panting and dilation of the surface blood vessels to increase heat loss to the environment.

4. How does the kidney compensate when an animal is deprived of water to drink?


 * The kidney compensates when an animal is deprived of water to drink through the action of the hormones antidiuretic hormone (ADH) and aldosterone, both of which act to increase the amount of water reabsorbed from the kidney tubule and increase the concentration of the urine produced. When the blood pressure decreases as occurs when fluid intake is insufficient, the reduced flow of blood through the glomerulus of the kidney tubule also reduces the amount of fluid filtered into the tubule so less urine is produced.

5. After moderate blood loss, several mechanisms come into play to increase blood pressure and make up blood volume. 3 of these mechanisms are:


 * After moderate blood loss, several mechanisms come into play to increase blood pressure and make up blood volume. These mechanisms include: thirst, constriction of blood vessels in the skin and kidneys, increasing heart rate, secretion of antidiuretic hormone and aldosterone, as well as drawing fluid from the tissues into the blood by increasing the osmotic pressure of the blood.

6. Describe how panting helps to reduce the acidity of the blood.


 * Panting helps to reduce the acidity of the blood by blowing out carbon dioxide. Carbon dioxide dissolved in the blood makes the blood acidic so removal of this carbon dioxide reduces the acidity of the blood.