Endocrine System

Question 1

Exocrine glands

Answer 1

• secrete into a duct that carries the secretion to the body surface or to one of the body’s cavities
• eg. sweat glands, mucous glands, salivary glands, glands of the alimentary canal

Question 2

Endocrine glands

Answer 2

• secrete hormones ino the extracellular fluid that surrounds the cells that make up the gland; usually carried by the blood
• ductless
• eg. pineal gland, thyroid gland, pancreas, testes, ovaries, adrenal gland, thymus, pituitary gland, hypothalamus

Question 3

Hormones

Answer 3

• proteins, steriods, amines
• only able to influence cells that have the correct receptor
• can change the functioning of the cells by changin type, activities or quantities of proteins being produced

Question 4

Protein and amine hormones

Answer 4

• attach to receptor proteins in the membrane of the target cell
• hormone and receptor cause a secondary messenger substance to diffuse through the cell and activate enzyme
• limited number of receptor proteins in each cell - can be no further increase in the rate of a cell’s reaction

Question 5

Steroid hormones

Answer 5

• work by entering target cells and combining with a receptor inside the cell
• receptor MAY be in the mitochondria, on other organelles or nucleus

Question 6

Hormones may…

Answer 6

• activate certain genes in the nucleus so that a particular enzyme or structural protein is produced
• change the shape or structure of an enzyme so that it is turned ‘on’ or ‘off’
• change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation during protein production

Question 7

Enzyme amplification

Answer 7

• a single hormone activates thousands of enzymes

- hormone triggers cascading effect

Question 8

Hormone clearance

Answer 8

• breaking down ot the hormone molecules once it has produced the required effect
• occurs mostly in the liver and kidneys but also in target cells
• excreted in bile or urine

Question 9

Control of hormone secretions

Answer 9

• negative feedback systems secrete the hormone that is the opposite of the stimulus that caused the secretion

Question 10

Hypthalamus

Answer 10

• located at the base of the brain
• regulates basic functions of the body eg. Temperature, water balance and heart rate
• many functions are carried out through the pituitary gland

Question 11

Pituitary gland

Answer 11

• lies just under hypothalamus (connected by a stalk; infundibulum)
• anterior and posterior love
• makes hormones that instruct other glands to produce hormones (regulate activity)

Question 12

Anterior lobe of pituitary

Answer 12

• No nerves connecting it to hypothalamus but is connected by a network of blood cells
• releases a number of hormones that regulate a range of bodily activities

Question 13

Hormones released by anterior lobe

Answer 13

• gonadotropins
  • follicle stimulating hormone (FHS)
  • luteinising hormone (LH)
• growth hormone
• thyroid-stimulating hormone (TSH) or thyrotrophin
• adrenocorticotrophin (ACTH)
• prolactin (PRL) or lactogenic hormone

Question 14

Gonadotropins

Answer 14

• hormones that affect the gonads, the ovaries and testes

Question 15

Follicle Stimulating Hormone (FSH)

Answer 15

Female; stimulates development of the follicles that contain the egg
Male; production and maturation of sperm in testes

Question 16

Luteinising hormone

Answer 16

Female; brings about ovulation and to form corpus luteum after ovulation
Male; stimulated interstitial cells in the testes to secrete male sex hormones

Question 17

Growth hormone

Answer 17

• stimulates body growth (in particular the skeleton)

- increases the rate at which amino acids are taken up by the cells and built into proteins

Question 18

Thyroid-stimulating hormone

Answer 18

Stimulate production and release of hormones from the thyroid gland

Question 19

Adrenocorticotropic hormone

Answer 19

• controls production and release of some hormones from the cortex of the adrenal glands

Question 20

Prolactin

Answer 20

• works with other hormones to initiate and maintain milk secretion in females

Question 21

Posterior lobe of the pituitary gland

Answer 21

• not a true gland as it doesn’t secrete substances
• joined to the hypothalamus by nerve fibres
• releases the hormones oxytocin and antidiuretic hormone but neither are secreted here
• produced in nerve cells of the hypothalamus

Question 22

Oxytocin

Answer 22

• stimulates contraction of the muscles of the uterus

- stimulates mammary glands (release of milk when breastfeeding)

Question 23

Antidiuretic hormone

Answer 23

• because the kidneys to remove water from urine that is forming
• water returned to the bloodstream
• helps retain fluid within the body

Question 24

Pineal gland

Answer 24

• secreted hormone melatonin; involves in regulation of sleep
• deep inside the brain
• decreases in size after puberty

Question 25

Thyroid gland

Answer 25

• located in the neck
• two lobes that lie on either side of the trachea (joined by narrow piece of tissue)
• secreted thyroxine

Question 26

Thyroxine

Answer 26

• made from iodine and an amino acid
• continually manufactured
• controls body metabolism by regulating reactions in the which complex molecules are synthesised from simple ones
• BRING ABOUT RELEASE OF ENERGY AND MAINTAIN BODY TEMPERATURE
• secreted in response to thyroid- stimulating hormone

Question 27

Parathyroid glands

Answer 27

• rear surface of the lobes of the thyroid gland

- secrete parathyroid hormone; calcium and phosphate levels in the blood