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Flashcards in Introduction to the Endocrine System Deck (95):
1

What is endocrinology

The study of the endocrine system

2

What is neuroendocrinology

The study of the control of the endocrine system by the nervous system

3

What is neuroendocrine integration

How the two systems interact in order to maintain homeostasis in the body

4

What is the endocrine system

Communication within the body using hormones

5

What is a hormone

A chemical produced by a ductless endocrine gland which is secreted into the blood. It is transported to a target elsewhere in the body where it causes an effect

6

How do hormones communicate with their target cells

They bind to receptors on their target cells

7

What happens if the appropriate receptor is not present on a cell

The hormone cannot affect it

8

Describe cell membrane receptors

A hormone binds to a receptor in the cell membrane which triggers a response in the target cell

9

Describe receptors in the nucleus

Once the hormone has crossed the cell membrane it bind to receptors in the nucleus. Forms a hormone-receptor complex which causes gene expression

10

What are the two types of receptors on target cells

Receptors on cell membranes and receptors in the nucleus

11

What types of chemical substances are hormones

1. Steroids 2. Proteins/ peptides 3. Amines

12

Where are steroids synthesised

In the adrenal cortex, ovaries, testes and placenta

13

How are steroids transported

They are not very soluble in blood so are transported bound to proteins

14

How do steroids enter cells

They are fat soluble so cross membranes easily and diffuse out of cells

15

What type of receptors do steroids have

Intracellular receptors

16

Steroids are easily absorbed in the GI tract- True/ False

True

17

Why can steriods be administered orally

Because they are easily absorbed in the GI tract

18

In what form are proteins/ peptides synthesised

They are synthesised as 'prehormones'/ 'prepeptides'

19

Where are proteins/ peptides stored

They are stored in membrane-bound vesicles/ granules

20

How are proteins/ peptides transported

They circulate unbound in the blood

21

What type of receptors do proteins/ peptides have

Cell membrane receptors

22

Why can't proteins/ peptides be administered orally

They are too easily digested

23

What are the two varieties of amines

1. Thyroid hormones 2. Catecholamines

24

What are thyroid hormones derived from

Tyrosine

25

Do thyroid hormones cross cell membranes

Yes

26

What type of receptors do thyroid hormones have

Intracellular receptors

27

How are thyroid hormones transported

They are protein-bound

28

Where are thyroid hormones stored

In thyroid follicles

29

Can thyroid hormones be administered orally

Yes

30

What are catecholamines derived from

Tyrosine

31

DO catecholamines cross the cell membrane

Yes

32

What type of receptors do catecholamines have

Cell membrane receptors

33

How are catecholamines transported

Unbound in the blood

34

How how catecholamines stored

In membrane-bound vesicles/ granules

35

Can catecholamines be administered orally

Yes but their half life is too short

36

What 5 things does binding hormones to proteins do

1. Prolongs their circulating half-life 2. Prevents them from entering the wrong type of cell 3. Prevents them from being lost through the kidneys 4. Maintains the right concentration of the hormone 5. Acts as a 'buffer' against a drop in the secretion of a hormone

37

How do hormones act on their target cells

1. Receptor binding 2. Initiates intracellular cell-signalling events (2nd messenger hypothesis).

38

Describe second messenger hypothesis

A hormone binds to a receptor which initiates the production of cAMP which are called 'second messengers'

39

Which are the male endocrine glands

1. Pituitary gland 2. Thyroid gland 3. Adrenal gland 4. Testis

40

What are the female endocrine glands

1. Pineal gland 2. Thymus 3. Pancreas 4. Ovary

41

What is a very important trace element in thyroid hormones

They contain iodine (iodothyronines)

42

What are the 3 thyroid hormones

1. Thyroxine (T4) 2. Triiodothyronine (T3) 3. Reverse T

43

Describe the 3 components of a thyroid gland

1. Colloid

2. Follicular epithelium

3. Follice

44

What are the 4 functions of thyroid hormones

1. Maturation, development and growth. 2. Metabolism (Control basic metabolic rate). 3. Skeletal muscle (calcium availability). 4. Cardiovascular system

45

Describe the stages of thyroid hormone production

  1. Thyroglobulin (TG) couples to a follicular cell membrane by thyroid peroxidase.
  2. TG enclosed by lysosome containing proteolytic enzymes.
  3. Iodinated tyrosines (MIT and DIT) are then deiodinated.
  4. Tyrosine and iodine are recycled.

46

What two endocrine tissues are located within the adrenal gland

1. Adrenal cortex 2. Adrenal medulla

47

Which two catecholamines are secreted by the adrenal medulla

1. Noradrenaline 2. Adrenaline

48

What controls the adrenal medulla

The sympathetic nervous system

49

Which do receptors do adrenaline and noradrenaline act on

Alphareceptors and betareceptors

50

What effects to adrenaline and noradrenaline have on betareceptors

1. Metabolic 2. Cardiovascular 3. Bronchodilation

51

What effects to adrenaline and noradrenaline have on alphareceptors

1. Metabolic 2. Cardiovascular 3. Sweating 4. Dilation of pupils 3. Sphincter contractor

52

What 3 groups of hormones does the adrenal cortex produce

1. Mineralocorticoids 2. Glucocorticoids 3. Sex hormones

53

Give an example of a mineralocorticoids and explain what they do

Aldosterone. Regulate mineral metabolsim- retention of Na+ and water resorption by the kidney. Secretion of H+ and K+

54

Give an example of a glucocorticoid and explain what they do

Cortisol. Regulates blood glucose levels

55

Give an example of a sex hormone and explain what they do

Weak androgens that can be converted into more potent sex hormones (androgens) such as testosterone and oestrogens, especially in women

56

Describe the pancreas

The pancreas is both an exocrine and endocrine gland

57

What is the endocrine part of the pancreas called

Islets of Langerhans

58

What are the 3 types of cells of the Islets of Langerhans

1. Alpha cells 2. Beta cells 3. Delta cells

59

What do alpha cells produce and what is the function of this hormone

Glucagon- a catabolic hormone which can mobilise stores of glycogen, fat and protein to act as energy sources during food deprivation

60

What do beta cells produce and what is the function of this hormone

Insulin- an anabolic hormone which causes the uptake and use of glucose from the blood during times of excess nutrient availability

61

What do delta cells produce and what is the function of this hormone

Somatostain- inhibits growth hormone and gastrin

62

Describe what happens when there are low blood glucose levels

Detected by the pancreas -> glucagon is released by alpha cells > liver releases glucose into blood -> achieve normal blood glucose levels

63

Describe what happens when there are high blood glucose levels

Detected by the pancreas -> beta cells release insulin -> fat cells take in glucose from the blood -> achieve normal blood glucose levels

64

Why must the levels of Ca2+ be tightly regulated

Because it can become very toxic to cells

65

What percentage of Ca2+ is found in the bones and teeth

99%

66

What percentage of Ca2+ is found intracellulary

0.9%

67

What percentage of calcium is found in the ECM

0.1%

68

What is half of free Ca2+ bound to

Proteins or PO4(3+)

69

How much calcium is freely diffusible

About half is freely diffusible and can take part in chemical reactions- this must be tightly regulated

70

What happens in terms of neuromuscular excitability when Ca2+ levels decrease

Over excitability of nerves and muscles

71

What happens in terms of neuromuscular excitability when Ca2+ levels increase

Depressed the excitability of nerves and muscles

72

What is the function of Ca2+ in cardiac and smooth muscle

Excitation-contraction coupling. Ca2+ entry into these tissues initiated the contractile mechanism

73

What happens when Ca2+ enters nerves and cells that secrete peptide hormones

It triggers the secretory process

74

What increases Ca2+ levels

Parathormone (PTH)

75

What is parathormone produced by

The parathyroid gland

76

What does parathormone do

Increase levels of Ca2+ and so prevents hypocalcaemia

77

Apart from parathormone what else is involved in the regulation of Ca2+

Calcitonin and vitamin D

78

Which parts of the body does parathromone regulate the exchange of Ca2+

In the bone, kidneys and intestine

79

Which are the two main cells involved in reproductive endocrinology

Leydig cells Sertoli cells

80

Label the leydig and sertoli cells

Diagram

81

What are sertoli cells involved in

Maturation of sperm by producing peptodes that act as hormones

82

What do leydig cells produce

Testosterone which is a steroid hormone and an androgen

83

What are the effects of testosterone before birth

Regulates differentiation and development of internal and external genitalia

84

What are the effects of testosterone at puberty

1. Regulates growth and maturation of the internal and external genitalia. 2. Development of secondary sexual characteristics (hair, deep voice, muscle growth). 3. Initiates and maintains spermatogenesis. 4. Develops sex drive.

85

What are the other effects of testosterone

1. Aggression 2. Bone growth and fusion of epiphyses

86

Label the parts of the female reproductive endocrinology system

Diagram

87

What do the ovaries do

1. Produce eggs (oogenesis). 2. Secrete the female sex hormones oestrogen and progesterone

88

What do oestrogen and progesterone help to promote

They help to promote fertilisation and get the reproductive system ready for pregnancy

89

What are the functions of oestrogen

Similar to those of progesterone (secondary sexual characteristics etc.)

90

What is the menstrual cycle controlled by

A very complex series of interactions between hormones

91

What are the components of the menstrual cycle synthesised by

The ovary, anterior part of the pituitary gland that the hypothalamus of the brain

92

What are the 3 aspects of the endocrinology of pregnancy

1. Development of the placenta 2. Implantation of the fertilised ovum. 3. Birth (parturition).

93

What is the posterior lobe of the pituitary gland attached to

The hypothalamus at the base of the brain

94

What does the anterior pituitary gland regulate

Several physiological processes: stress, growth, reproduction, lactation

95

How many hormones does the pitutitary gland secrete and what do these hormones do

Secretes 9 hormones that regulate homeostasis