#127 Summary of Homeostasis and Co-ordination

 1 Animals and plants have internal communication systems that allow information to pass between different parts of their bodies, and so help them to respond to changes in their external and internal environments.

 2 Mammals keep their internal environment relatively constant, so providing steady and appropriate conditions within which cells can carry out their activities. This is known as homeostasis.

#116 Homeostasis in plants

Stomata have daily rhythms of opening and closing and also respond to changes in environmental conditions to

- allow diffusion of CO­_2­

- regulate water loss by transpiration

#115 Urine analysis, dipsticks and biosensors

The presence of glucose and ketones in urine indicates that a person may have diabetes. If the concentration for these rises above the renal threshold, then not all glucose has been absorbed from the filtrate in the proximal convoluted tubule --> so will be present in the urine.

#114 Control of blood glucose - glucagon

Insulin and glucagon work together as part of a negative feedback system. As a result of glucagon secretion, the liver releases extra glucose to increase the concentration in the blood. Muscle cells do not have receptors for glucagon and so do not respond to it.

#113 The control of blood glucose

The blood glucose concentration is regulated by negative feedback control mechanisms.

#112 Osmoregulation

Osmoregulation is the control of the water content of body fluids. It is part of homeostasis, the maintenance of a constant internal environment.

#111 Production of urine in a nephron - Ultrafiltration and reabsorption

Ultrafiltration occurs at the barrier between the blood and the filtrate in the renal capsule or Bowman's capsule in the kidneys.

#110 Excretion and structure of Kidneys

The kidneys remove wastes from the blood and are the effectors for controlling the water potential of the blood. The removal of waste products generated by metabolic reactions inside body cells is called Excretion. Some of these products are toxic, while others are simply in excess of requirements.

#109 Thermoregulation - The control of body temperature

One of the most important examples of homeostasis is the regulation of body temperature. It involves both coordination  systems - nervous and endocrine. Not all animals can do this physiologically.

#108 Homeostasis in mammals

In the body of an animal conditions such as water concentration, temperature, and glucose concentration must be kept as constant as possible. Control systems that keep such conditions constant are examples of homeostasis; this is the maintenance of constant internal conditions in an organism.

# 107 Homeostasis Syllabus 2016-2018

14.1  Homeostasis in mammals
14.2  Homeostasis in plants