AAP Endocrine System

Question 1

What is the function of the endocrine system?

Answer 1

• regulates the body by chemical substances produced

- substances are hormones

Question 2

What are hormones?

Answer 2

• may be steroids, proteins or amines
• they regulate the activities of the target organ
• endocrine glands secrete hormones into the blood and are transported to the target organs where they are utilized

Question 3

What are some endocrine glands and where are they located?

Answer 3

• pituitary gland in the brain
• ovaries from the reproductive system
• adrenal gland
• kidney
• pancreas

Question 4

State and explain (or give e.g.) of why hormones are secreted.

Answer 4

Nerve impulses
- e.g. adrenaline released from the adrenal gland in response to nerve impulses from the sympathetic nervous system
A stimulating/releasing hormone
- e.g. the secretion of thyroid hormone is controlled by a hormone from pituitary gland (thyroid-stimulating hormone)
Levels of certain chemicals in the blood
- e.g. raised blood glucose levels stimulate the release of insulin from the pancreas
Negative feedback system
- mechanism that prevents over-secretion
- e.g. oestrogen from the ovaries prevents the further secretion of follicle-stimulating hormone (FSH) from pituitary gland

Question 5

Where are the endocrine glands located and what is its function?

Answer 5

• located in the ventral part of the brain (hypothalamus)
  Functions:
• appetite control
• body temperature regulation
• wake-sleep cycle control
• controls activities of the pituitary gland (more focus on this)

Question 6

How are the activities of the pituitary gland controlled?

Answer 6

• neurons in the hypothalamus secretes releasing and inhibiting factors into blood vessels
• These factors travels a short distance to the target cells at the pituitary body
• This controls the release of hormone in the region
• modified neurons in the hypothalamus also secretes antidiuretic hormone (ADH) and oxytocin
• these hormones are transported to the posterior pituitary for storage and released into the bloodstream when needed

Question 7

What are the two separate glands in the pituitary gland?

Answer 7

• anterior pituitary (rostral position)

- posterior pituitary (caudal portion)

Question 8

What are the functions of the anterior pituitary?

Answer 8

• developed from glandular tissue
• it produces hormones
• subject to stimulation of hypothalamus and/or feedback from target organs

Question 9

What are the functions of the posterior pituitary?

Answer 9

• developed from nervous system

- stores and releases hormones produced in the hypothalamus

Question 10

List the hormones that the anterior pituitary produces.

Answer 10

• growth hormone
• prolactin
• thyroid-stimulating hormone
• adrenocorticotropic hormone
• follicle-stimulating hormone
• luteinizing hormone
• melanocyte-stimulating hormone

Question 11

What is the function of the growth hormone?

Answer 11

• AKA somatotropin/somatotropic hormone
• promotes body growth in young animals
• helps regulate the metabolism of proteins, carbohydrates and lipids

Question 12

What is the function of prolactin?

Answer 12

• helps to trigger and maintain lactation (secretion of milk by the mammary glands)
• Prolactin production and release continues as long as the teat or nipple continues to be stimulated by nursing or milking
• when prolactin stimulation stops, milk production stops, and the mammary gland shrinks back to its non-lactating size

Question 13

What is the function of thyroid-stimulating hormone (TSH)?

Answer 13

• AKA thyrotrophic hormone
• stimulates the development of thyroid gland and its production of hormone (thyroxine)
• secretion of TSH is controlled directly, by feedback from the thyroid gland
• secretion of TSH is also controlled indirectly by TSH-releasing factor (hormone produced at the hypothalamus)

Question 14

What is the function of the adrenocorticotropic hormone (ACTH)?

Answer 14

• stimulates growth and development of the adrenal gland and release of its hormones
• production is controlled by feedback from the hormones of the adrenal cortex
• in times of sudden stress, ACTH can also be released very quickly as a result of stimulation of the hypothalamus

Question 15

What is the function of follicle-stimulating hormone (FSH)?

Answer 15

• in females, stimulates growth and development of ovarian follicles
• also stimulates cells that line the follicles to secrete oestrogen
• in males, FSH acts on the tubules of the testis to aid spermatogenesis

Question 16

What is the function of luteinizing hormone (LH)?

Answer 16

• completes process of follicle development in ovary (started by FSH)
• as the folicle grows, increasing amount of oestrogen is produced which feedbacks to the anterior pituitary
• this causes increased production of LH and reduced production of FSH
• LH levels reach a peak when follicle is fully mature and it causes ovulation
• after ovulation, LH stimulates cells in the empty follicle to develop into the corpus luteum
• The corpus luteum produces progesterone necessary for the maintenance of pregnancy
• in males, LH stimulates interstitial cells to develop and produce testosterone

Question 17

What is the function of melanocyte-stimulating hormone (MSH)?

Answer 17

• hormone that stimulates melanogenesis
• associated with the control of colour changes in pigment cells (melanocytes) in reptiles, fish, and amphibians
• artificially administration of large amounts of MSH to higher mammals can cause darkening of the skin due to melanocyte stimulation

Question 18

What is stored in the posterior pituitary?

Answer 18

• ADH
• oxytocin
• the two hormones are transported from the hypothalamus to the posterior pituitary and stored in nerve endings
• periodically released into the blood stream in response to nerve impulses from hypothalamus

Question 19

What is the purpose of antidiuretic hormone (ADH)?

Answer 19

• acts on the kidney to reabsorb more water from the urine and return it to the bloodstream
• helps prevents diuresis (the loss of large amounts of water in the kigney)
• ADH is released when the receptor in the hypothalamus detects a change of osmotic pressure of blood from dehydration
• ADH deficiency causes diabetes insipidus (large amount of diluted urine)

Question 20

What is the purpose of oxytocin?

Answer 20

Effect on uterus
- causes the contraction of the uterus (muscle) during breeding and at the delivery of the fetus
- contraction of the uterus aids transport of sperm to the oviducts
Effect on active mammary glands
- causes the contraction of mammary gland ducts
- causes the movement of milk along the mammary gland ducts
- teat or nipple stimulation by nursing or milking causes oxytocin to be released into the bloodstream