Glands
What is an endocrine gland?
A ductless gland that releases hormones directly into the bloodstream.
What is a hormone?
A chemical messenger produced by an endocrine gland and transported in the blood to target cells or organs
Where is the pituitary gland located?
At the base of the brain, beneath the hypothalamus.
What is negative feedback?
Define homeostasis.
The maintenance of a relatively constant internal environment.
Name TWO hormones produced by the pancreas that regulate blood glucose.
Insulin and Glucagon
Which hormone prepares the body for a fight-or-flight response?
Adrenaline
Which gland produces growth hormone, and what is one function of this hormone?
The pituitary gland; growth hormone stimulates growth, particularly of bones and body tissues.
What is the role of the control centre in a negative feedback system?
It processes information about a change and coordinates an appropriate response.
Give TWO benefits of maintaining homeostasis.
Enzymes can function close to their optimum conditions.
Cells can function properly.
Internal conditions remain suitable for essential metabolic reactions.
The body can maintain stable conditions despite external changes.
Name the hormone produced by the thyroid gland and give ONE function.
Thyroxine. It regulates metabolic rate
What effect does insulin have on blood glucose concentration?
It lowers blood glucose concentration by promoting glucose uptake and storage, including as glycogen.
Which hormone stimulates the thyroid gland to produce and release thyroxine?
Thyroid-stimulating hormone (TSH), released by the pituitary gland.
What is the role of a receptor in a negative feedback system?
It detects a change in an internal condition.
Name one internal conditions, other than body temperature, that the body regulates through homeostasis.
Blood glucose concentration
Blood pH
Water balance
Ion concentrations
Why is the pituitary gland often called the master gland?
It produces hormones that regulate the activity of other endocrine glands.
A person has a higher-than-normal thyroxine concentration. Predict the general effect on their metabolic rate.
Their metabolic rate generally increases.
What is meant by hormone manipulation?
Deliberately altering hormone levels or hormonal activity, for example by administering hormones or drugs that affect hormone production.
What is the role of an effector in a negative feedback system? Give ONE example.
An effector carries out a response that helps correct a change in the internal environment. For example, sweat glands produce sweat when body temperature rises.
Name TWO ways the body responds when its temperature falls below normal.
Shivering — muscle contractions generate heat.
Reduced sweating — less heat is lost through evaporation.
A person has an underactive thyroid gland. Name the hormone that is deficient and give TWO possible effects on the body.
Thyroxine. Possible effects include a reduced metabolic rate, tiredness, increased sensitivity to cold or weight gain. Accept any two.
Explain why a hormone only affects certain target cells in the body.
Only target cells with the appropriate receptors for that hormone respond to it.
Explain how administering thyroxine could affect the release of TSH from the pituitary gland in a person with a normally functioning hypothalamic-pituitary-thyroid axis.
Increased thyroxine levels inhibit the release of TSH through negative feedback, reducing stimulation of the thyroid gland.
Body temperature rises above normal. Explain how negative feedback helps return it towards normal.
Thermoreceptors detect the rise; the hypothalamus coordinates a response; sweating and vasodilation increase heat loss; body temperature falls towards normal.
A person becomes dehydrated after exercising for a long period without drinking water. Explain why maintaining water balance is important for the body.
Water is needed for essential metabolic reactions, transporting substances around the body and maintaining normal cell function. Maintaining water balance prevents cells from gaining or losing excessive amounts of water.