Homeostasis and the Endocrine System Flashcards Preview

Z OLD ESA 1- Metabolism > Homeostasis and the Endocrine System > Flashcards

Flashcards in Homeostasis and the Endocrine System Deck (151):
1

What are the 4 characteristics of a control system?

Stimulus, Receptor, Control centre, Effector

2

What does a receptor do?

Detects stimuli

3

Give 4 examples of receptors

#NAME?

4

Give 2 examples of things chemoreceptors respond to?

- Hormones 
- Neurotransmitters

5

What do proprioreceptors do?

Give awareness of position

6

What do nociceptors do?

Detects painful stimuli

7

How does the receptor communicate with the control centre?

By the afferent pathway

8

How does the nervous system communicate?

Action potentials

9

How does the endocrine system communicate?

Hormones

10

Where is the control centre typically located?

In the brain, usually the hypothalamus

11

What does the control centre do?

#NAME?

12

How does the control centre communicate with the effector?

The efferent pathway

13

What does the effector do?

Causes change

14

Give 3 examples of effectors

#NAME?

15

What usually happens once the effector has caused change?

Negative feedback

16

In what direction does negative feedback act?

In direction opposing original stimulus

17

What does negative feedback do?

Responds in a way to reverse the direct change

18

What does positive feedback do?

Responds in a way as to change the variable even more in the direction of change

19

When is positive feedback used?

When rapid change is desirable

20

Give 3 examples of where positive feedback is used

- Blood clotting
- Ovulation 
- The Ferguson reflex during childbirth

21

Is the set point of a control centre constant or variable?

Variable

22

What rhythm does the body display?

Circadian (or diurnal)

23

What does the ‘biological clock’ in brain consist of?

Small group of neurones in suprachiasmatic nucleus

24

What does the biological clock respond to?

Cues from environment- Zietgeben

25

What cues from the environment keep the body on a 24h cycle?

#NAME?

26

Give an example of the manifestation of disruption of biological rhythms?

Jet lag

27

What causes jet lag?

Mismatch of the environmental cues and body clock when long haul flights cross time zones

28

How much body water does the average person have?

42L

29

What does body water content vary between?

#NAME?

30

What are the 3 main compartments containing body water?

#NAME?

31

What is the osmotic pressure of the blood plasma monitored by?

Osmoreceptors in hypothalamus

32

What is osmolarity?

Number of osmoles per litre of solution

33

What is osmolality?

The number of osmoles per Kg of solution

34

What is an osmole?

The amount of substance that dissociates in solution to form one mole of osmotically active product

35

What is responsible for bodily fluid homeostasis?

Antidiuretic hormone (ADH)

36

Why is it important to keep osmolarity in set range?

Otherwise causes disruption to cells- can cause them to shrink or burst

37

What is it called when there is high blood osmolarity?

Hypertonicity

38

What must happen when the blood is hypertonic?

The body needs to conserve water

39

What are osmoreceptors in the hypothalamus technically detecting?

Tonicity, because across a membrane

40

What does hypertonicity lead to?

#NAME?

41

Why does hypertonicity cause thirst?

Because drinking reduces osmolarity, and so returns normal blood osmolarity

42

Is ADH synthesised by the posterior pituitary?

No, just secreted- synthesised in hypothalamus

43

Why does the body secrete more ADH when the blood is hypertonic?

Because it increases reabsorption of water from the urine into blood via collecting ducts in the kidney, leading to a return to normal blood osmolarity

44

What does the reabsorption of water from urine cause?

A smaller volume of concentrated urine

45

What does the body need to do when there is low blood osmolarity?

Excrete water

46

What detects low blood osmolarity?

Osmoreceptors in the hypothalamus

47

What happens in response to low blood osmolarity?

Posterior pathway secretes less ADH

48

What is the result of decreased secretion of ADH?

Decreased absorption of water from the urine into the blood from the collecting ducts of the kidney, leading to large volumes of dilute urine and a return to normal blood osmolarity

49

What does the endocrine system consist of?

A collection of glands located throughout the body

50

What are hormones?

Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues

51

What are the major endocrine glands?

- Hypothalamus 
- Pituitary glands
- Pineal glands
- Thyroid glands
- Parathyroid glands
- Thymus
- Pancreas
- Adrenal gland
- Ovary 
- Testis

52

What can release hormones other than endocrine glands?

Other organs and tissues

53

What other organs and tissues release important hormones?

#NAME?

54

What hormones does the heart produce?

#NAME?

55

What hormone does the liver produce?

IGF1

56

What hormones does the stomach produce?

#NAME?

57

What hormones does the placenta produce?

#NAME?

58

What hormone does the adipose produce?

Leptin

59

What hormones does the kidney produce?

#NAME?

60

What are the 4 mechanisms of communication via hormones?

#NAME?

61

How does autocrine communication work?

Hormone signal acts back on cell of origin

62

How does paracrine communication work?

Hormone signal carried to adjacent cell over a short distance via interstitial fluid

63

How does endocrine communication work?

Hormone signal released into bloodstream carried to distant target cells

64

How does neurocrine communication work?

Hormone originates in neurone, and after transport down axon, released into bloodstream and carried to distant target cells

65

Where is neurocrine communication important?

In hypothalamic pituitary axis

66

What features to endocrine and nervous system have in common?

- Both neurones and endocrine cells are capable of secreting 
- Both neurones and endocrine cells can be depolarised 
- Some molecules act on both neurotransmitters and hormones
- The mechanism of action requires interaction with specific receptors in the target cells

67

What do neurones secrete?

Neurotransmitters

68

Why can both neurones and endocrine cells be depolarised?

They are both excitable cells with a resting membrane potential

69

What do the endocrine and nervous systems work in parallel to do?

Control homeostasis

70

What are the differences between endocrine and nervous systems?

- The signal for the endocrine system is hormones, whereas for the nervous system it is neurotransmitters and action potentials 
- The signals for the endocrine system are chemical in nature, whereas they are both chemical and electrical for the nervous system
- Signals from the endocrine system are conveyed in the bloodstream, whereas the nervous signals are conveyed by synapses and axons
- Endocrine signals are slow, whereas nervous signals are fast

71

What groups are hormones classified into?

#NAME?

72

Which is the largest group of hormones?

Peptide/polypeptides

73

What do peptide/polypeptide hormones consist of?

Short chains of amino acids

74

Give 3 examples of peptide/polypeptide hormones

- Insulin
- Glucagon 
- Growth hormones

75

Are peptide/polypeptide hormones water or lipid soluble?

All water soluble

76

What are amino acids derivatives synthesised form?

Amino acids (tyrosine)

77

Give 3 examples of amine hormones

- Adrenaline
- Noradrenaline 
- Thyroid hormones

78

Are amine hormones water or lipid soluble?

- Adrenal medulla hormones water soluble 
- Thyroid hormones lipid soluble

79

Are do glycoprotein hormones consist of?

Large protein molecules, that tend to be glycosylated. Often made up of sub-units

80

What is meant by glycosylated?

They have a carbohydrate side chain

81

Give 3 examples of glycoprotein hormones

- Lutenizing hormone 
- Follicle stimulating hormone 
- Thyroid stimulating hormone

82

Are glycoproteins water or lipid soluble?

Water

83

What are steroid hormones derived from?

Cholesterol

84

Where are steroid hormones produced?

Steroidogenic tissues

85

Give 3 examples of steroid hormones

- Cortisol 
- Aldosterone 
- Testosterone

86

Are steroid hormones water or lipid soluble?

Lipid

87

How are hormones transported?

- Some hormones in the blood in simple solution 
- Most hormones bind to (usually) proteins

88

Give two examples of hormones that can travel in the blood in simple solution

#NAME?

89

What feature must a hormone have to be able to travel in the blood in simple solution?

Water soluble

90

What group of hormones bind to proteins to travel in the blood in particular?

Steroid

91

Give an example of a hormone that binds to a specific protein for transport?

Thyroid hormones bind to thyroxine-binding globulin

92

What exists between bound and free forms of hormone in plasma?

Dynamic equilibrium

93

What form of a hormone is biologically active?

Only the free form

94

Give the equilibrium between bound and free forms of a hormone

Free hormone + binding protein ↔ bound hormone

95

What are the roles of carrier proteins?

#NAME?

96

What 3 main factors determine hormone levels in the blood?

- Rate of production
- Rate of delivery 
- Rate of degradation

97

What is the most highly regulated aspect of hormonal control?

Rate of production

98

What does rate of production of hormone consist of?

- Synthesis 
- Secretion

99

What would result in a higher rate of delivery of hormone?

Increased blood flow to a particular organ

100

What is meant by rate of degradation of hormones?

The rate at which its metabolised and excreted from body

101

At what concentrations do hormones circulate in the blood?

Very low

102

What do hormones do to exert their effects?

Bind to specific receptors

103

Why are hormone receptors needed?

For specificity, as the blood stream bathes all cells

104

What do endocrine cells do?

Synthesise and release hormone into the bloodstream

105

What happens to hormones in the blood stream?

It’s carried to distant target tissue

106

What happens in a non-target cell?

There is no receptor for hormones, so no response to hormone

107

What happens in a target cell?

It has expressed the specific receptor for hormone, and so there is a specific cellular response to hormone

108

What do water soluble hormones bind to?

Cell surface receptors

109

Why do water soluble hormones bind to cell surface receptors?

As they can’t cross the plasma membrane

110

Give an example of a G protein coupled receptor

Adrenaline receptors

111

What is the mechanism of action for a G protein coupled receptor?

- Dissociation of G protein sub-unit
- Activation of effector protein
- Formation of second messenger
- Activation of protein kinase
- Phosphorylation of target proteins 
- Cellular response

112

Give an example of a tyrosine kinase receptor

An insulin receptor

113

What is the mechanism of action for a tyrosine kinase?

- Dimerisation 
- Autophosphorylation of specific tyrosines
- Recruitment of adaptor proteins and signalling complexes
- Activation of protein kinase 
- Phosphorylation of target proteins 
- Cellular response

114

Where does dimerisation not occur in a tyrosine kinase?

In an insulin receptor

115

Why does dimerisation not occur in an insulin receptor?

It is already dimerised

116

What do lipid soluble hormones bind to?

Intracellular receptors

117

Why can lipid soluble hormones bind to intracellular receptors?

Because they are able to diffuse across plasma membrane

118

How does a type I lipid soluble hormone interact with its target cell?

Cytoplasmic receptor binds hormone, and receptor-hormone complex enters nucleus and binds DNA

119

How does a type II lipid soluble hormone interact with it’s target cell?

Hormone enters nucleus and binds to a pre-bound receptor DNA. Binding relieves repression of gene transmission

120

Where does a receptor bind to a DNA molecule?

To a specific sequence called a hormone response element (HRE) in the promoter region of specific genes

121

What is the effect of hormonal binding to DNA?

It affects the mRNA, and therefore the new protein, which induces a cellular response

122

What mediates the effect of a lipid soluble hormone?

The expression of new protein

123

Do lipid soluble hormones promote or repress gene transcription rate?

Can do either

124

What is the hypothalamic pituitary axis?

A complex functional unit formed by the hypothalamus and the pituitary gland that serves as the major link between the endocrine and nervous systems

125

Where does the pituitary gland sit?

Beneath the hypothalamus, in a sock of bone called the sella turcia

126

Give 8 processes that the hypothalamus and pituitary gland module

- Body growth
- Reproduction
- Adrenal gland function
- Water homeostasis
- Milk secretion
- Lactation 
- Thyroid gland function
- Puberty

127

What does the pituitary gland consist of?

- Anterior pituitary gland (adenohypophysis) 
- Posterior pituitary gland (neurohypophysis)

128

How are the anterior and posterior pituitary gland distinct from one another?

- Different embryological origins 
- Distinct functions

129

Is the pituitary gland physically connected to the hypothalamus?

Yes, the posterior pituitary gland is

130

How is the posterior pituitary gland connected to the hypothalamus?

The hypothalamus drops down through the infundibulum to form the posterior pituitary

131

What is the neurocrine function of the posterior pituitary?

- Oxytocin and ADH hormone are produced by neurones in the hypothalamus 
- These hormones are transported down nerve cell axons to the posterior pathway 
- The hormones are stored and released from the posterior pituitary into the general circulation to act on distinct targets

132

How are hormones synthesised in the hypothalamus transported to the anterior pituitary?

They are transported down axons

133

What happens to hormones once they are in the anterior pituitary?

They are stored in median eminence before release into hypophyseal portal system

134

What is the neurocrine function of anterior pituitary hormones?

The hormones stimulate or inhibit target endocrine cells in the anterior pituitary gland

135

What is the endocrine function of the anterior pituitary hormones?

The endocrine cells of the anterior pituitary secrete a variety of hormones into the bloodstream to act on distant target cells

136

What is the autocrine and paracrine function of the anterior pituitary hormones?

The hormones also affect neighbouring cells

137

In summary, what pathways do the hormones produced by nerve cells in the hypothalamus act?

#NAME?

138

What hormones are produced in the hypothalamus for release from the posterior pathway?

#NAME?

139

What does oxytocin do?

#NAME?

140

What does ADH do?

Regulates body water volume

141

How many trophic hormones are there produced in the hypothalamus?

7

142

What do trophic hormones do?

Have direct effects on release of anterior pituitary hormone

143

What are the 7 trophic hormones produced in hypothalamus?

#NAME?

144

Give 6 hormones produced by the anterior pituitary

#NAME?

145

What does TSH do?

Controls secretion of thyroid hormone from the thyroid gland

146

What does AOTH do?

Controls secretion of hormones from adrenal cortex

147

What does LH do?

Controls ovulation and secretion of sex hormones

148

What does FSH do?

Controls development of eggs and sperm

149

What does PRL do?

Controls mammary gland development and milk secretion

150

What does GH do?

Controls growth, and energy metabolism, and stimulates IGFs

151

How are the pathways by which hypothalamic and anterior pituitary hormones are produced often regulated?

Negative feedback