The Endocrine System

Question 1

1.1 Define a hormone.

Answer 1

Specialised chemical messengers that alter the activity of a target cell.

Question 2

1.1 Define the endocrine system.

Answer 2

A controlling system that produces and secretes hormones to influence metabolic activities through the blood.

Question 3

1.2 Difference between endocrine and exocrine glands.

Answer 3

Exocrine glands secrete through ducts onto an epithelial surface. Endocrine glands secrete messengers into the bloodstream.

Question 4

1.3 List 3 similarities and differences between the endocrine and nervous systems

Answer 4

Similarities: (x3)
○ Act via receptors
○ Hormones and neurotransmitters have multiple effects on the same organ
Chemicals can act as both neurotransmitters and hormones

Differences: (x3)
○ Communication: Endocrine communicates via chemicals, nervous system communicates via chemicals and electrical signals.
○ Distribution: Endocrine is widespread, nervous system is localised and specific.
○ Reaction to stimuli: endocrine is slow, nervous is fast

Question 5

1.4 List the 2 main chemical classes of hormones and give examples of each

Answer 5

Steroids: Testosterone

Non-stoirds: Adrenaline/melatonin

Question 6

1.5 Describe how hormones are transported to their site of action

Answer 6

Steroid are hydrophobic, must bind to transport hormones in blood. Target cells in nucelus

Non steroids are hydrophillic and mix easily with blood plasma. Target cell is cell membrane

Question 7

1.6 Describe how hormones stimulate their target cells & state any differences between the main chemical groups of hormones

Answer 7

Steroid: lipid soluble & receptors are found within target cells cytosol. Binds to receptor molecule
Non steroids: cannot pass through cell membrane. Bind to receptor proteins on cell surface which activates second messengers (cAMP)

Question 8

1.7 Describe how target cells can adjust their sensitivity to a hormone

Answer 8

Sensitivity = number of receptors
Up-regulation = increased cell receptors and cell sensitivity
Down regulation = decreased cell receptors and cell sensitivity

Question 9

2.1 Describe the anatomy of the hypothalamus & pituitary gland & their relationship to each other (Hypothalamus)

Answer 9

Location: region of the diencephalon, forms the floor/part of walls of third ventricle. Superior to pituitary gland.
Function: major control centre of endocrines and ANS.

Question 10

2.1 Describe the anatomy of the hypothalamus & pituitary gland & their relationship to each other (Pituitary)

Answer 10

Location: base of brain, inferior to hypothalamus, in sella turcica
Two regions: anterior and posterior
Connected to hypothalamus through stalk with a blood portal system. neural linkage for posterior pituitary and hypothalamus

Question 11

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (TRH)

Answer 11

TRH: Thyrotropin-releasing hormone

Promotes secretion Prolactin (PRL) and Thyroid-stimulating hormone (TSH)

Question 12

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (CRH)

Answer 12

(CRH) - Corticotropin-releasing hormone

Promotes secretion Adrenocorticotropic hormone (ACTH)

Question 13

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (GnRH)

Answer 13

(GnRH) - Gonadotropin-releasing hormone

Promotes secretion follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)

Question 14

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (GHRH)

Answer 14

(GHRH) - Growth hormone-releasing hormone

Promotes secretion Growth hormone (GH)

Question 15

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of (PIH)

Answer 15

(PIH) - Prolactin-inhibiting hormone

Inhibits secretion Prolactin (PRL)

Question 16

2.2 List hormones produced by the hypothalamus, Whats the target organ/s or tissue & state principal effects of Somatostatin

Answer 16

Somatostatin

Inhibits secretion Growth hormone (GH) and Thyroid stimulating hormone (TSH)

Question 17

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (FSH)

Answer 17

(FSH) - Follicle-stimulating hormone
Target: Ovaries and Testes
Effect: F- Growth of ovarian follicles and secretion of estrogen, M- sperm production.

Question 18

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (LH)

Answer 18

(LH) - Luteinizing hormone
Target: Ovaries and Testes
Effect: F- ovulation, maintenance of corpus luteum, M- testosterone production.

Question 19

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (TSH)

Answer 19

(TSH) - Thyroid-stimulating hormone
Target: Thyroid gland
Effect: growth of thyroid gland, secretion of thyroid hormone.

Question 20

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (ACTH)

Answer 20

(ACTH) - Adrenocorticotropic hormone
Target: Adrenal cortex
Effect: growth of adrenal cortex, secretion of glucocorticoids.

Question 21

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (PRL)

Answer 21

(PRL) - Prolactin
Target: mammary glands, testes
Effect: F- Milk synthesis, M- increased (LH) sensitivity

Question 22

2.3 List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects of (GH)

Answer 22

(GH) - Growth Hormone
Target: Liver, bone, cartilage, muscle, fat
Effect: widespread tissue growth, especially in the stated tissues.

Question 23

2.4 List hormones stored by the posterior pituitary gland, list target organ/s or tissue & state principal effects

Answer 23

(ADH) - Antidiuretic hormone
○ Target: Kidneys
○ Effect: Water retention

(OT) - Oxytocin
○ Target: Uterus, mammary glands
○ Effect: Labour contractions, milk release, ejaculation, sperm transport

Question 24

2.5 Explain how pituitary secretion is controlled by the hypothalamus and target organs and exemplify using multiple examples

Answer 24

Anterior Pituitary Control: Hypothalamus secretes hormones into blood. Travels to hypophyseal portal system. Adenohypophysis is where the target cells of releasing hormones are located. Feedback loop.

Posterior Pituitary Control: regulated by hypothalamus, brain centres and feedback from organs. feedback can be positive or negative hence increase or decrease section of hormones.

Question 25

2.6 Describe the effects of growth hormone

Answer 25

Growth Hormone has widespread effects on the body tissues especially on cartilage, bone, muscle and fat. Bone growth at epiphyseal plates, thickening, and remodelling of bone are influenced during childhood.

Question 26

3.1 Pineal gland; state its location, list the hormone/s it produces and their effects

Answer 26

Location: in centre of the brain between the two hemispheres, in roof of third ventricle. Hormones/Effects: Melatonin - body's biological clock and sleep/wake cycles

Question 27

3.2 Thyroid gland; state its location, describe its structure, list hormones produced & their effects

Answer 27

Location: in the neck inferior to larynx and wrapped around the trachea Structure: Consists sacs called thyroid follicles which are lined with follicular cells (secrete T3 &T4) that surround a protein rich collar Parafollicular C cells (Secrete calcitonin) are found between follicles Hormones/Effects: T3 & T4 increase basal metabolic rate. Calcitonin increases osteoblast activity & raises blood calcium levels. Promotes calcium deposition and bone formation

Question 28

3.3 Parathyroid gland; state its location, describe its structure, list hormones produced & their effects

Answer 28

Location: in the neck and embedded in the posterior surface of the thyroid gland Consists of four ovoid glands Hormones/Effects: Parathyroid hormone in response to hypocalcaemia Parathyroid hormone function: Increase blood calcium levels Increase osteoblast activity Enhancing the reabsorption of Ca2+ and the secretion of phosphate by the kidneys

Question 29

3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Aldosterone

Answer 29

Aldosterone (Zona glomerulosa) - regulate electrolyte excretion and intravascular volume affects distal tubules and cortical collecting ducts of kidneys increase sodium and reabsorption and potassium excretion

Question 30

3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Glucocorticoids

Answer 30

Glucocorticoids (Zona fasciculata) - □ Stimulated by ACTH, glucocorticoids stimulate fat and protein catabolism □ Stimulate gluconeogenesis □ Increase blood glucose and fatty acid levels in the bloodstream □ Glucose sparing effect □ Supress immune system with long-term secretion □ Anti-inflammatory effect & Generally helps the body adapt to stress

Question 31

3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal cortex Conadocorticoids

Answer 31

Conadocorticoids (Zona reticularis) - Weak androgens such as dehydroepiandrosterone (DHEA) Some oestradiol supplement that functions of the sex steroid produced by the gonads

Question 32

3.4 Adrenal glands; state their location, describe its structure, list hormones produced & their effects - Adrenal medulla

Answer 32

Adrenaline & noradrenaline - (Fight or flight response) □ Increase cardiac output □ Dilation of blood vessels in heart, lungs, brain and muscles □ Vasoconstriction in vessels of skin and viscera □ Increase blood glucose □ Increase RR and metabolism □ Increase fatty acid metabolism from adipose tissue

Question 33

3.5 The pancreatic islets; state their location, describe their structure, list hormones produced & their effects

Answer 33

Location: in the curve of the duodenum • Endocrine portion of the pancreas Hormones/Effects: Endocrine islets of Langerhans consists of three different cell types that secrete hormones: Glucagon Function: (Alpha) □ Secreted in response to low blood glucose □ Increase blood glucose levels by using energy reserves □ Stimulates glycogen breakdown to glucose □ Stimulates breakdown of fats to free fatty acids Insulin Function: (Beta) □ Secreted in response to high blood glucose □ Increase glucose uptake and synthesis of energy stores □ Also stimulates amino acid uptake and protein synthesis □ Anabolic hormone Somatostatin Function: (Delta) □ Inhibits secretion of insulin and glucagon & Slows absorption of GIT.

Question 34

3.6 The gonads; state their location, describe their structure, list hormones produced and their effects

Answer 34

Location: Testes and Ovaries ○ Testes: paired oval glands located in the scrotum, consists of microscopic seminiferous tubules that produce sperm with interstitial cells, they produce testosterone. ○ Ovaries: Paired oval bodies located in the female pelvic cavity Consist of follicles which surround egg cells Produce the hormone oestradiol, progesterone, and inhibin. Hormones/Effects: Testosterone, Oestradiol, Progesterone, and Inhibin: ○ Testosterone Function: Develop male genitals and accessory sex organs Development of secondar sex characteristics Stimulate libido ○ Estrogen Function: Regulates the female reproductive cycle Stimulate female secondary sex characteristics ○ Progesterone Function: Inhibits thickness of endometrium, pro-pregnancy hormone ○ Inhibin: Supress FSH secretion