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HUBS191 > What is homeostasis and why is it important? What are hormones and how do they work? > Flashcards

What is homeostasis and why is it important? What are hormones and how do they work? Flashcards

1
Q

What is homeostasis?

A

The presence of a stable (not static) environment

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2
Q

What is the stimulus?

A

Increase or decrease in a variable

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3
Q

What is the receptor?

A

Detects the change in the variable

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4
Q

What is the control centre?

A

Compares the change to the set point and sends appropriate signals to effector organs

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5
Q

What are the effectors?

A

Organs and/or tissues which respond with various affects which may be localised or throughout the body to return the variable to set point

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6
Q

What is set point?

A

The value we would expect the variable to be at

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7
Q

What is normal range?

A

The range which the value fluctuates between as it takes time to return the variable to the set point

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8
Q

What does each individual have?

A

A normal range within which their levels of a given variable fluctuate

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9
Q

What does the population have?

A

A reference range based on the breadth of individual normal ranges within a population

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10
Q

What does the population range tend to be?

A

Wider than normal fluctuations within an individual. Therefore each individuals normal range is more narrow than the population range

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11
Q

What may moving outside the individuals normal range lead to?

A

Symptoms of a disorder, even when hormone levels are within the population reference range

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12
Q

What do most individuals have?

A

A set point and normal range that is within the population reference range

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13
Q

What is involved in synaptic (neural) control systems?

A

Action potentials in axons and neurotransmitters release at synapse

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14
Q

How is targeting achieved by neural control systems?

A

By specific wiring

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15
Q

What is the speed of transmission in neural control systems?

A

Fast to minimise response delays

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16
Q

What is the neural control system good for?

A

Brief responses

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17
Q

What is the chemical signal of the neural control system?

A

Neurotransmitters

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18
Q

What is the distribution of effects for the neural control system?

A

Limited to a very specific area, target cells must have appropriate receptors

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19
Q

What is involved in the endocrine (hormonal) control system?

A

Hormones released into the blood

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20
Q

How is targeting achieved by hormonal control systems?

A

The presence of specific receptors on target cells

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21
Q

What is the speed of transmission in hormonal control system?

A

Relatively slow but long lasting action (prolonged effect)

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22
Q

What is the hormonal control system good for?

A

Widespread and sustained responses

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23
Q

Where is transmission in the neural control system?

A

Across synapses

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24
Q

Where is transmission in the hormonal control system?

A

Through the bloodstream

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25
Q

What is the chemical signal of the hormonal control system?

A

Hormones

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26
Q

What is the distribution of effects for the hormonal control system?

A

To target cells mainly in other distant tissues and organs and must have appropriate receptors

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27
Q

What does the endocrine system consist of?

A

Endocrine gland cells which contain vesicles of hormones (chemical messengers) that are carried in the bloodstream to the target cells upon which they act

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28
Q

Where are target cells?

A

In other distant tissues or organs and they must have appropriate receptors

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29
Q

What does the hypothalamus do?

A

Links the nervous system to the endocrine system and controls the secretion of many endocrine glands

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30
Q

What are some major endocrine glands?

A

Hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas (pancreatic islets) and parathyroid glands

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31
Q

What are some variables maintained homeostatic ally through hormones?

A

Blood sugar concentration, growth and repair, basal metabolic rate, blood calcium concentration and many more

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32
Q

What is involved in the homeostasis of one variable?

A

Often many hormones

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33
Q

What are hormones?

A

Chemical messengers produced in one location and transported via the bloodstream to a second location (target cells) where they cause a response in the cells

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34
Q

What is paracrine communication?

A

Through the extracellular fluid with paracrine as chemical signals which only effect cells in the immediate vicinity

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35
Q

What is autocrine communication?

A

Through the extracellular fluid with autocrines as chemical signals which come back and act on the cell which released it

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36
Q

What is meant by specificity of hormone action?

A

A hormone can only affect cells with specific receptors for that hormone. Each receptor is a protein which may be in the target cell membrane or inside the target cell

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37
Q

What are the classifications of hormones?

A

Water soluble and lipid soluble

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38
Q

What is the chemical classification of water soluble hormones?

A

Peptides (most abundant) and catecholamines

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39
Q

What is the chemical classification of lipid soluble hormones?

A

Steroids and thyroid hormones

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40
Q

What is the storage of water soluble hormones?

A

They are stored until required and then released by exocytosis

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41
Q

What is the storage of lipid-soluble hormones?

A

Steroids are made from cholesterol as required (not stored) and thyroid hormones are made in the thyroid cells and stored until required

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42
Q

What is the transport of water soluble hormones?

A

Dissolved in the blood

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43
Q

What is the transport of lipid soluble hormones?

A

Bound to carrier proteins

44
Q

Where are the receptors of water soluble hormones?

A

On the cell surface because they cannot cross the cell membrane

45
Q

Where are the receptors of lipid soluble hormones?

A

Intracellular receptors in the cytoplasm or nucleus because they can diffuse across the cell membrane

46
Q

What is the mechanism of action of water soluble hormones?

A

Through second messengers

47
Q

What is the mechanism of action of lipid soluble hormones?

A

By altering gene transcription

48
Q

What is the speed of communication of water soluble hormones?

A

Milliseconds to minutes (neural is faster)

49
Q

What is the speed of communication of lipid soluble hormones?

A

Hours to days

50
Q

What is the first step in cellular response of water soluble hormones?

A

Water soluble hormone binds to cell surface receptor

51
Q

What happens after the water soluble hormone binds to cell surface receptor?

A

Hormone binding allows the association of G-protein

52
Q

What happens after association of G-protein?

A

Second messenger production/reduction

53
Q

What happens after second messenger production/reduction?

A

Amplification of the cellular response (FAST)

54
Q

What is the first step in cellular response of lipid soluble hormones?

A

Lipid soluble hormone dissociates from carrier protein

55
Q

What happens after lipid soluble hormone dissociated from carrier protein>

A

Hormones diffuse across the cell membrane

56
Q

What happens after hormones diffuse across the cell membrane?

A

Hormone binds to intracellular receptor in cytoplasm or nucleus

57
Q

What happens after hormone binds to intracellular receptor in cytoplasm or nucleus?

A

Hormone-receptor complex acts as a specific transcription factor

58
Q

What happens after the hormone-receptor complex acts as a specific transcription factor?

A

Target gene is activated

59
Q

What happens after the target gene is activated?

A

new mRNA is generated

60
Q

What happens after new mRNA is generated?

A

New protein is generated by translation of mRNA

61
Q

What happens after a new protein is generated by translation of mRNA?

A

New protein mediates cell specific response (slow process)

62
Q

What is the common mechanism for maintenance of hormone levels?

A

negative feedback

63
Q

What is involved in negative feedback?

A

Reduce change until stimulus is removed or directly inhibit further use

64
Q

What is the other mechanism for maintenance of hormone levels?

A

Positive feedback

65
Q

What is included in positive feedback?

A

Amplification of change until a desired outcome is achieved

66
Q

Why do hormone levels need to be maintained?

A

To maintain the effects of hormones

67
Q

What does the amount of hormones in the blood depend on?

A

Rate of hormone secretion and rate of removal from blood

68
Q

What is removal of hormones controlled by?

A

Enzymes in the blood or in target cells

69
Q

What is secretion of hormones usually controlled by?

A

A negative feedback loop but sometimes positive feedback is used by a few hormones at specific times

70
Q

What is the goal of hormones?

A

To maintains homeostasis

71
Q

What can too much or too little hormone lead to?

A

Endocrine disorders

72
Q

What is the pancreas?

A

An endocrine and exocrine gland

73
Q

What part of the pancreas is an exocrine gland?

A

Cells of the pancreatic acini which secrete digestive enzymes

74
Q

What part of the pancreas is an endocrine gland?

A

Pancreatic islets which make up approximately 1% of the mass of the pancreas

75
Q

What do the pancreatic islets contain?

A

Beta cells which secrete insulin and alpha cells that secrete glucagon

76
Q

What happens if blood glucose concentration is too high for too long?

A

Diabetes develops

77
Q

What happens if blood glucose concentration is too low for too long?

A

Hypoglycemia occurs

78
Q

What must the brain be supplied with and why?

A

Glucose at all times as it is the only fuel that the brain uses

79
Q

What happens to blood glucose concentration throughout the day?

A

It changes as we use fuel continuously but we eat intermittently

80
Q

What are the two metabolic states we move between?

A

Fed state and fasting state

81
Q

What happens in the fed state?

A

Cellular uptake of nutrients & anabolic metabolism (synthesis of glycogen, protein and fat)

82
Q

What happens in the fasting state?

A

Mobilisation of nutrients and catabolic metabolism (breakdown of glycogen, protein and fat)

83
Q

What hormones maintain blood glucose concentration?

A

Insulin and glucagon

84
Q

What is the range for blood glucose concentration?

A

70-100 mgdL-1

85
Q

What happens if blood glucose concentration is increased?

A

Insulin is secreted from the beta cells to return the value to the reference range (decrease it)

86
Q

What happens if the blood glucose concentration decreases?

A

Glucagon is secreted from the alpha cells to return the value to the reference range (increase it)

87
Q

What is new glucose synthesis called?

A

Gluconeogenesis

88
Q

What happens in gluconeogenesis?

A

fatty acids and amino acids are slowly converted into glucose

89
Q

What is the quick release of glucose called?

A

Glycogenolysis

90
Q

What happens in glycogenolysis?

A

Stored glycogen is broken down into glucose in a fast process

91
Q

What is glucose storage?

A

The formation of glycogen

92
Q

What happens first when blood glucose concentration increases?

A

Insulin is secreted from the pancreatic islet beta cells into the bloodstream. The beta cells are the receptor and control centre

93
Q

Where does the insulin in the bloodstream go to?

A

The liver, muscle and adipose cells

94
Q

What does insulin do at the liver?

A

Stops glucose output to increase the net glucose uptake (glycogen and fat synthesis)

95
Q

What does insulin do at the muscle and adipose cells?

A

Increase glucose uptake, increase amino acid uptake, glycogen and protein synthesis as well as fat synthesis

96
Q

What is the result of insulins effects on the liver, muscle and adipose cells?

A

Decreased blood glucose concentration

97
Q

What is insulin?

A

A peptide hormone which targets cells that have membrane receptors

98
Q

What does insulin do?

A

Increases fuel storage. It is the only hormone that can decrease the blood glucose concentration

99
Q

What does glucagon do?

A

Increases fuel release

100
Q

What is glucagon?

A

A peptide hormone that targets cells which have membrane receptors

101
Q

What happens when blood glucose concentration decreases?

A

The pancreatic islet alpha cells secrete glucagon into the bloodstream. The alpha cells are the receptor and control centre

102
Q

What is the target cells of glucagon?

A

Liver cells

103
Q

What does glucagon do to the liver cells?

A

Increase the breakdown of glycogen (glycogenolysis), increase glucose synthesis (gluconeogenesis) and increase ketone synthesis which can be used as an energy source for non-brain tissue

104
Q

What is the result of glucagon’s effects on the liver cells?

A

Increase blood glucose and blood ketones concentration

105
Q

What can also increase blood glucose concentration?

A

Growth hormone, adrenaline and cortisol

HUBS191 (29 decks)

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