Stable Internal Environment

What are the three main components of the control system?

- Receptors which detects the change in the environment - Effectors which are the parts of the body which produces a response to the change. - Control system (hypothalamus) which controls and integrates physiological activities.

How does the hypothalamus work in order to regulate body temperature?

1.) It controls the core body temperature of 37 degrees therefore it acts as the body's thermostat. 2.) Temperature change is detected by peripheral receptors in the skin (hot and cold), deep receptors (in the organs) and the central receptors (in the brain). 3.) The receptors send nerve impulses to the hypothalamus which co-ordinates an appropriate response to the thermal effectors e.g. blood vessels and sweat glands.

How do sweat glands respond when the core body temperature decreases?

Decrease in nerve signals to inhibit sweat production.

What effect do enzymes have on homeostasis?

Enzymes are biological catalysts which control the biochemical reactions which is requires for a stable internal environment. These enzymes work in specific conditions and any changes of these conditions will affect the function of the enzymes.

What does homeostasis mean?

Homeostasis is maintaining a constant internal environment within a narrow range.

Why is homeostasis important?

Homeostasis provides a stable internal environment for the body's cells and allow them to work at their optimum conditions.

Where is the hypothalamus found?

It is located below the thalamus and is above the pituitary gland.

How is homeostasis maintained?

It is maintained through a combination of hormonal and nervous mechanisms.

What is the hypothalamus?

It is the control centre which receives information from sensory receptors and uses this information to control and integrate many basic physiological activities e.g. thermoregulation.

What is thermoregulation?

It is the regulation of body temperature (37 degrees) which is controlled by the hypothalamus

What is the role of the hypothalamus?

It links the endocrine system to the nervous system through the pituitary gland.

How do sweat glands respond when the core body temperature increases?

Sweat glands are activated through an increase in nerve signals to the sweat glands which secrete perspiration. It helps cool down the body because sweat is vaporised by body heat due to an increase in blood flow to the skin.

How does the endocrine glands respond when there is an increase in core body temperature?

The ADH is produces in the hypothalamus and is released by the pituitary gland to increase water re-absorption by the kidney which decreases metabolism.

How does the endocrine glands respond when there is a decrease in core body temperature?

The adrenal glands release adrenaline and the thyroid glands releases thyroxine.This helps heat up the body because the release of adrenaline increases metabolic rate therefore there is more heat produces. Thyroxine brings a long term change in metabolic rate.

How do the pili-erector muscles respond when there is a decrease in core body temperature?

The muscles contract and hairs rise up. This helps heat up the body because this traps a layer of insulating air next to the skin.

How do the pili-erector muscles respond when there is an increase in core body temperature?

The muscles will relax and lie flat. This helps cool down the body because more air is circulated.

How does negative feedback allow the body to go back to its steady environment?

The response acts to oppose the changes in the input.

How do skeletal muscles respond when the core body temperature decreases?

There is an increase in nerve impulses which results in involuntary contraction of the skeletal muscles known as shivering. It helps heat up the body because more heat is generated due to the activation in skeletal muscles.

What is negative feedback?

This is a form of self-correcting so the fluctuations in the internal environment are dampened to allow the body to remain in its relatively constant state.

How do blood vessels respond when the core body temperature decreases?

Vasoconstriction is when blood vessels in the skin get narrower and blood is diverted from the skin capillaries. It helps increase temperature because the volume of the blood flowing near the skin is reduces and is withdrawn to deeper tissues which minimises heat loss from the skin surface.

How do blood vessels respond when the core body temperature increases?

Vasodilation is when blood vessels in the skin get wider and capillaries become flushed with warm blood. It helps the body cool down because the large volume of the blood flows near the skin surface which transfers hear to the environment.