Metabolism Session 7 - Introduction to the endocrine system and the endocrine pancreas Flashcards Preview

Semester 1 - Metabolism > Metabolism Session 7 - Introduction to the endocrine system and the endocrine pancreas > Flashcards

Flashcards in Metabolism Session 7 - Introduction to the endocrine system and the endocrine pancreas Deck (100):
1

What are the four main types of communication in the body?

Give four characteristics of control systems

Endocrine
Nervous
Autocrine
Paracrine

Communication
Control Center
Receptor
Effector

2

What are the two main types of communication in body? (I know I said there were four before, but these are the biggies)

Endocrine
Nervous

3

What is the mechanism of action for nervous communication?

Action potentials

4

What is the afferent branch?

Signal direction towards the brain

5

What is autocrine communication?

Variety of agents released by cells have effect on cell itself

6

What is paracrine communication?

Hormones released locally rather than directly into the blood

7

What are the three roles of a control center in the body?

Name two control centers, and what they control

Determine set reference point of chemical levels
Analyses signals from afferent branch
Determines appropriate response

Hypothalamus involved in endocrine control.
Medullar involved in cardiovascular and respiratory.

8

What is a receptor used for?

To detect stimuli, such as changes in environment

9

Name three examples of receptors

Chemo, pressure and temperature

10

What is an effector?

An agent that controls change

11

What is the pathway from control center once response has been decided?

Control --> Efferent nervous pathway --> Effector

12

What does loss of efferent pathway use do in paraplegic patients?

Sweat glands cannot be controlled, so reduces ability of paraplegic patients to lose heat

13

What is negative feedback, and how common is it?

Effectors oppose stimulus
Occurs in most homeostatic control systems

14

What are the two advantages of negative feedback?

Give stability to control systems
Allow a point to be controlled within fine limits

15

What is hunting behaviour and what is it indicative of?

Occurs in negative feedback when levels overshoot set points several times before rest. Indicative of dynamic equilibrium.

16

What is positive feedback?

Stimulus produces a response which increases its effect

17

How fast is the change caused by positive feedback?

Rapid

18

Give two examples of positive feedback in the body

Ovulation and blood clotting cascade

19

Give two examples of negative feedback in body

Hyperglycaemia stimulates insulin release
Body water homeostasis

20

Where is biological clock situated in body? (think chasm)

Suprachiasmaic nucleus in hypothaamus

21

Give three examples of biological rhythmns

Cortisol levels vary throughout the day. Peak at 7 am and trough at 7 pm. So, blood cortisol levels should be measured at same time each day.
Menstral cycle varies over month. Womans core body temperature varies during cycle and can be used as a marker of ovulation.
Melatonin released from pineal gland in response to light and dark

22

What do you have to do when measuring cortisol levels in patients and why?

Take measurement same part of day, varies throughout day (peaking at 7 am, troughing at 7pm)

23

How many litres of water in normal healthy 70KG male?

42

24

How many litres of blood in heathy 70 kg male?

4.6

25

What is an increase in blood osmolarity?
What happens when it is detected?

Increase in conc (not enough water)

Osmoreceptors in hypothalamus detect decrease in water potential (increased osmolarity)
ADH (vasopressin) is released from the posterior pituatry
Causes increase in permeability of collecting ducts to water, increasing reabsorption of water from the urine into the blood
Makes urine more concentrated

26

Where is ADH released from?

Posterior pituitary

27

What is ADH released in response to?

Increased blood osmolarity

28

What does ADH do?

Causes increase in permeability of collecting ducts in kidney to water, increasing reabsorption of water

29

What is a HORMONE?

Chemical messengers travel via blood stream

30

Afferent branch Hypothalamus  Anterior pituitary gland  Endocrine glands
What is missing?

Releasing factors

31

Outline Hypothalamic-Pituitary-Adrenal axis

Hypothalmus  Corticotrophin releasing hormone (CRH)  Anterior pituitary  Adrenocorticotrophic hormone  Adrenal cortex  Cortisol  Inhibits anterior pituitary

32

What are two factors which control hormone secretion?

•Change in a variable regulated by a hormone
•Concentration of hormone itself or another hormone

33

Why do hormones bind with proteins in the blood?

Mostly not soluble enough to dissolve

34

Name two hormones which exhibit specific binding to proteins

Steroid and thyroid hormones

35

Give three reasons why hormones bind with protein carriers

•Increases solubility of hormone in plasma
•Increases half life of hormone
Serves as readily accessible reserve

36

Name four main types of hormone
(PAGS)

Polypeptide hormone
Glycoprotein hormones
Amino acid derivatives
Steroids

37

Why is the largest hormone group?

Polypeptide

38

What do polypeptide hormones consist of?

Short or long single chain(s) of amino acids

39

Give two types of polypeptide hormone

Insulin and Glucagon
(also GSH and placental lactogen)

40

What do glycoprotein hormones consist of?

Large two chained protein molecules with carbohydrate sidechains

41

Name two types of glycoproteins

LH, FSH and TSH

42

What do amino acid derviatives consist of?

Small molecules synthesised from amino acids

43

Name two types of amino acid derivatives

Adrenaline and thyroid hormones

44

What are steroids derived from?

Cholesterol

45

What do different steroid hormones differ in?

The number of carbons

46

Give three examples of steroid hormones

Cortisol, testosterone, oestrogen, progesterone

47

Name three hydrophillic hormone types

Polypeptide, Glycoprotein and adrenaline (amino acid derivative)

48

Name two hydrophobic hormone types

Steroid and thyroid hormones

49

What is the main variable which determines the effect of hormones on target cell?

Concentration of free or unbound hormone

50

What two changes in concentration can have clinical consequences?

Defiency and excess

51

Where are the receptors bound to by lipophillic hormones situated?

Inside cell (cytoplasmic/nuclear)

52

What do hormones bind to

Specific, high affinity receptor

53

Give examples of things which hormone binding to receptors may affect

Activity of enzyme or gene expression

54

How long does a change in gene expression take to take effect?

Minutes-hours

55

Give three factors which influence magnitude of hormonal response

• Concentration of active hormone at target tissue
• Receptor number
• Affinity of receptor for hormone
• Degree of signal amplification

56

How is rate of secretion of hormones affected?

By blood concentration of hormones

57

What is a trophic hormone?

One that controls the secretion of another hormone by targeting endocrine tissue

58

Where are trophic hormones secreted?

Anterior pituitary

59

Name three hormones secreted by the anterior pituitary gland and their role

Thyroid Stimulating Hormone = Thyrotrophin (TSH) – affects thyroid gland
Adrenocorticotrophic Hormone = Corticotrophin (ACTH) – affects adrenal gland
Growth Hormone = Somatotrophin (GH) – affects metabolism
Luteinizing Hormone (LH) = Affects ovary and testis function

60

Name a regulatory mechanism for trophic hormones

Inhibited by high level of hormone they cause the secretion of in the blood (Wen concentration of thyroid hormone gets too high, less TSH is secreted. Negative feedback)

61

Where do releasing or inhibiting hormones come from?

Nerve cells in the hypothalamus

62

How do releasing or inhibiting hormones travel to endocrine glands?

Specialised blood vessels known as hypophseal portal vessels

63

Name three releasing hormones and what they effect

Thyrotrophin Releasing Hormone (TRH) – stimulates TSH release
Corticotrophin Releasing Hormone (CRH) – stimulates ATCH release
Somatotrophin Releasing Hormones (SRH) – stimulates GH release

64

Where does inactivation of hormones occur?

Liver, kidney and sometimes in target tissues

65

How are steroid hormones inactivated?

Relatively small change in chemical structure which increases water solubility enabling them to be excreted from the body in urine or bile

66

How are protein hormones inactivated?

Undergo extensive chemical change and are degraded to amino acids, which are then reused.

67

What is the structure of insulin?

Two chains linked covalently by two disulphide bridges. Extra third disulphide bridge in alpha chain

68

Where is insulin secreted?

B cells of islets of langerhans

69

How is insulin stored?

In B cells as crystalline-zinc complex storage granules

70

What is the structure of glucagon?

Single chain polypeptide hormone, lacking disulphide bridge so has flexible 3D structure

71

How is insulin circulated?

Dissolve in the plasma and circulates as free hormon

72

When is Glucagon activated?

Upon binding to its receptor on surface of target cells

73

What are the three main target tissues of insulin?

Liver, Skeletal muscle and adipose tissue

74

What part of a cell does insulin react with?

Cell surface receptors

75

What does insulin stimulate to work?

Enzymes and proteins inside target cell

76

How does glucagon become an active molecule?

Post translational processing to produce biologically active molecule

77

What type of metabolism does insuline encourage?

Anabolic

78

What type of metabolism does glycogen encourage?

Catabolic

79

What three metabolic reactants do insulin and Glucagon influence?

Carbohydrate, lipid and amino acid metabolism

80

What are the function of insulin in the short term?

Removes absorbed nutrients from blood following a meal

81

What are the long term functions of insulin?

cell growth/cell division that relate to its ability to stimulate protein synthesis and DNA replication.

82

What is the name for a glucagon receptor?

G protein coupled receptor (GPCR)

83

What does binding to the GPCR receptor by glucagon do?

Causes adenylate cyclase to increase, which increases cyclic AMP in the cell

84

Effect of insulin on glucose transport into adipose tissue?

Increase

85

What affect does insulin have on glycogenolysis?

Decrease in insulin
Increase glucagon

86

What effect do insulin and glucagon have on gluconeogenesis?

Decrease insulin
Increase in glucagon

87

What effect do insulin and glucagon have on ketogenesis in the liver?

Decrease in insulin
Increase with Glucagon

88

What effect does insulin have on lipolysis?

Decrease in insulin
Increase in glucagon

89

What effect does insulin have on amino acid uptake in liver?

Increase

90

What are the major cell types in islets of langerhans, and what quantities do they exist in?

B - 75% - Insulin
A - 20% - Glucagon

91

Where is glucagon and insulin stored in a cell?

In a storage granule

92

What are the three main features of a cell specialised for protein synthesis?

More RER, well defined golgi, more mitochondria and system of microtubules and filaments

93

Where is proinsulin converted to insulin?

Golgi apparatus

94

Where is preproinsulin converted to proinsulin?

Endoplasmic reticulum

95

How does glucose move into B cells?

GR2 receptor

96

What does increase of glucose in cells cause an increase in?

ATP conc

97

What channels does increase in ATP inhibit and what effect does this have?

ATP sensitive potassium ion channels
Depolarises cell membrane

98

What enters through voltage gated channel after membranal depolarisation?

Calcium ions

99

What do calcium ions do in B cells?

Stimulate exocytosis of insulin

100

Define homeostasis

The control of an internal environment within set limits, dynamic equilibrium rather than fixed steady state.