Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant environment
-Involves constant changes around an optimum point

Question 2

What is the importance of homeostasis?

Answer 2

-Changes in pH and temperature affect proteins e.g. enzymes
-Changes can cause a reduction in the rate of reaction
-Changes in water potential can change volumes in cells e.g expand or shrink
-Glucose concentration affects the glucose supply for respiration

Question 3

How are the changes of homeostasis controlled?

Answer 3

-Optimum = point where reaction works best
-Receptor = detects change from optimum
-Coordinator = links the receptor and the effector
-Effector = muscle or gland which brings changes to return system to optimum

Question 4

What is negative feedback?

Answer 4

-System deviates from optimum
-Change is detected by the receptor
-A change is then produced which returns the system back closer to the optimum

Question 5

What is positive feedback?

Answer 5

-System deviates from optimum
-Change is detected by the receptor
-A change is then produced which causes an even greater deviation from the optimum

Question 6

How are endocrine glands and hormones linked?

Answer 6

-Hormones are organic chemicals produced in an endocrine gland
-They travel in the blood and can be widespread or targeted
-Protein or peptide hormones e.g. insulin, ADH
-Steroid hormones e.g. oestrogen, progesterone

Question 7

What are the glands?

Answer 7

-Hypothalamus
-Pituitary gland
-Thyroid gland
-Pancreas
-Parathyroid gland
-Adrenal gland
-Kidneys
-Ovaries
-Testes

Question 8

How are hormones released?

Answer 8

Can be stimulated to release hormones by both nerves or other hormones

Question 9

What is the link between the pituitary gland and the hypothalamus?

Answer 9

-Both located in the brain
-The hypothalamus often controls the pituitary gland

Question 10

What is the pituitary gland?

Answer 10

-Controlled by the hypothalamus
-Produces 6 hormones from the anterior lobe
-Produces 2 from the posterior lobe

Question 11

What is the thyroid stimulating hormone?

Answer 11

Controls the secretion of thyroxin from the thyroid gland

Question 12

What is oxytocin hormone?

Answer 12

Stimulates the muscles of the uterus to contract during labour and stimulates the contraction of cells in the mammary tissue to release milk

Question 13

What is antiduretic hormone (ADH)?

Answer 13

Decreases the urine volume and causes arteries to constrict after haemorrhage

Question 14

What is prolactin hormone?

Answer 14

Stimulates and maintains the production of milk by mammary glands

Question 15

What is the lutinising hormone (LH)?

Answer 15

Stimulates ovulation and formation of corpus luteum and prepares the uterus for implantation in females and stimulates the testes to produce testosterone

Question 16

What is follicle stimulating hormone (FSH)?

Answer 16

Stimulates ovaries to produce oestrogen and stimulates the development of ova in females and stimulates the testes to produce sperm in males

Question 17

What is ACTH hormone?

Answer 17

Controls the secretion of some hormones of the adrenal glands

Question 18

What is the growth hormone (GH)?

Answer 18

Stimulates the growth of body cells and increases the build up of proteins

Question 19

What happens in the pituitary gland and hypothalamus?

Answer 19

-Hypothalamus contains neurosecretory cells which produce secretions from the axons
-Cells 1 (group of neurosecretory cells) produce substances that stimulate or inhibit the release of hormones from the anterior pituitary
-They are known as releasing factors (if they stimulate) or release-inhibiting factors (if they inhibit)
-Neurosecretory cells 2 produce secretions that are stored in the posterior pituitary and released later as hormones

Question 20

What is a second messenger?

Answer 20

-Hormones bind to a receptor on the target cell membrane
-Triggers a series of intracellular membrane bound reactions
-Stimulates the release of a second messenger
-The second messenger activates enzymes to alter the metabolism of the cell

Question 21

What is the example of a second messenger (adrenaline)?

Answer 21

-Adrenaline binds to a receptor
-This activates an enzyme called adenyl cyclase which converts ATP to cyclic AMP (cAMP)
-cAMP acts as a second messenger
-Triggers different responses in the cell e.g. increased respiration and muscle contraction

Question 22

What is oestrogen?

Answer 22

-A steroid hormone that can affect transcription by binding to a transcription factor
-Transcription factor is known as an oestrogen receptor
-Bind together to form an oestrogen to oestrogen receptor complex
-Moves to the nucleus where it binds to the promoter region before the target gene
-It then acts as a promoter

Question 23

What is an oestrogen receptor?

Answer 23

-A transcription factor
-It regulates gene expression events that culminate in cell division
-Important for mammary gland development