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HUBS > Module 4: Endocrine > Flashcards

Module 4: Endocrine Flashcards

1
Q

How is homeostasis restored after being disturbed by the increase decrease of a variable?

A

Receptor (sensor), detects the change, control center compares it to the set point and signals effectors.

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2
Q

Set point

A

The ideal, healthy point for a variable

Differs between individuals

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3
Q

Normal range

A

The range in which a variable is normal

Differs person to person

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4
Q

Population reference range - how does it compare to an individual’s normal range?

A

The population reference range tends to be wider than normal fluctuations within an individual

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5
Q

How do the neural and endocrine control systems differ?

A

Neural transmits information quickly across synapses with neurotransmitter

Endocrine releases hormones into the bloodstream for slow but long lasting action

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6
Q

What must the target cells of a hormone have?

A

Appropriate receptors

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7
Q

Where do hormones come from?

A

Endocrine gland cells

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8
Q

Hormone

A

A chemical messenger which travels through the bloodstream from one organ to the next, where they cause a response in the cells

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9
Q

What links the nervous system to the endocrine system?

What else does it do?

A

Hypothalamus

Controls the secretion of many endocrine glands

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10
Q

What are four variables that hormones maintain?

A

Blood sugar concentration
Growth and repair of tissues
Basal metabolic rate
Blood calcium concentration

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11
Q

Two classifications of hormones

A

Water-soluble and lipid-soluble

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12
Q

Two types of water-soluble hormones

A

Peptides- short chain of amino acids

Catecholamines- including adrenaline and noradrenaline

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13
Q

Two types of lipid-soluble hormones

A

Steroids (base of cholesterol)

Thyroid hormones (modified amino acids)

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14
Q

What about thyroid hormones is unusual for their classification?

A

They are made in thyroid cells and stored until required

Unlike other lipid-soluble hormones, which are made as required

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15
Q

Are water-soluble hormones stored or made when required?

A

Stored- released by exocytosis when required

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16
Q

Which classification of hormone travels dissolved in the blood?

A

Water-soluble hormones

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17
Q

How do lipid-soluble hormones travel in the blood?

A

Bound to a carrier protein

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18
Q

Where are the receptors for water-soluble hormones located? Why?

A

Within the target cell or it’s plasma membrane

Because water-soluble hormones cannot cross the cell membrane

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19
Q

Where are the receptors for lipid-soluble hormones located? Why?

A

In the cytoplasm or nucleus of the target cell

Because lipid-soluble hormones can diffuse across the cell membrane

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20
Q

What does the binding of a water-soluble hormone to a receptor allow?

A

The activation of an associated G-protein

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21
Q

What does the G-protein do?

A

Activates/ inhibits adenylyl cyclase

Or increases intracellular calcium ions

(ACTIVATES A SECOND PATHWAY)

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22
Q

What does a lipid-soluble hormone need to do before diffusing across the cell membrane?

A

Dissociate from its carrier protein

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23
Q

What does the hormone-receptor complex do once the hormone is bound?

A

It binds to DNA and the target gene is activated

New mRNA is generated, and so is a new protein

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24
Q

What does the new protein produced due to the binding of a lipid-soluble hormone do?

A

Mediates target cells response

A slow process

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25
Q

Difference between the mechanisms of water-soluble and lipid-soluble hormones?

A

Through second messengers (water-soluble)

And by altering gene transcription (lipid-soluble)

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26
Q

Difference in speed of response between water-soluble and lipid-soluble hormones

A

Water- milliseconds to minutes

Lipid- hours to days

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27
Q

How are hormone levels maintained?

A

Most commonly through negative feedback:

  • by reducing change until stimulus is removed
  • or by directly inhibiting further hormone release
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28
Q

What two factors determine the amount of hormone in the blood?

A
  • rate of hormone secretion

- rate of removal

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29
Q

What controls the removal of hormones from the bloodstream?

A

Enzymes in the blood or in target cells

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30
Q

What controls hormone secretion?

A

Negative feedback loops

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31
Q

What is the goal of hormones? And what happens if they fail?

A

To maintain homeostasis

Can lead to endocrine disorders

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32
Q

Is the pancreas an exocrine or endocrine gland?

A

Both

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33
Q

Three cells of the pancreas

A

Pancreatic islets (make up 1% mass)
Beta cells
Alpha cells

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34
Q

If blood glucose concentration gets too high, or too low, what happens?

A

Too high- diabetes

Too low- hypoglycaemia

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35
Q

Which organ must be supplied with glucose at all times and why?

A

The brain, because it’s its only fuel

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36
Q

Two metabolic states

A

Fed and fasting states

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37
Q

Fed state

A

Cellular uptake of nutrients and anabolic metabolism

Synthesis of glycogen protein and fat

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38
Q

Fasting state

A

Mobilisation of nutrients and catabolic metabolism

Breakdown of glycogen protein and fat

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39
Q

Reference range of blood glucose concentration

A

70-110 mg dL^-1

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40
Q

How is blood glucose lowered if too high?

A

Pancreatic islet beta cells secrete insulin into bloodstream

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41
Q

Target cells of insulin and effects

A

Muscle and adipose- increase glucose uptake

Liver cells- stop glucose output

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42
Q

Which materials are synthesised due to insulin secretion? Which materials uptake is increased?

A

Glycogen and fat

Amino acid uptake is increased in muscle and adipose cells

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43
Q

Which is the only hormone that can lower blood glucose concentration?

A

Insulin

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44
Q

How is blood glucose concentration increase when too low?

A

Pancreatic islet alpha cells secrete glucagon

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45
Q

Target cells of glucagon and effects (3)

A

Liver cells

Breakdown of glycogen, glucose and ketone synthesis all increase

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46
Q

Which other hormones can increase blood glucose? (3)

A

Growth hormone
Adrenaline
Cortisol

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47
Q

Difference between glycogen and glucagon

A

Glycogen is a stored form of glucose

Glucagon is a hormone which lowers blood glucose concentration

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48
Q

Which part of the body can be considered ‘outside’ the body?

A

Inside of gastrointestinal system

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49
Q

Function of kidneys

A

Regulate water loss in urine

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50
Q

Two parts of the pituitary gland

A

Posterior lobe/ pituitary

Anterior lobe/ pituitary

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51
Q

Where is the pituitary gland?

A

The base of the brain, connected to the hypothalamus

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52
Q

Function of hypothalamus

A

Controls secretion of pituitary hormones by stimulating the pituitary gland

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53
Q

What do pituitary hormones stimulate? (2)

A

Target cells

Secretion of hormones by other endocrine glands

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54
Q

How is the posterior pituitary connected to the hypothalamus?

A

By neurons

Cell bodies in the hypothalamus, axon terminals in posterior pituitary

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55
Q

Where are posterior pituitary hormones made and stored?

A

Made in the cell body of the neuron in hypothalamus, stored at axon endings until required (in posterior pituitary)

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56
Q

Hormones released by posterior pituitary (2) and their functions

A

Antidiuretic hormone- stimulates kidneys to reabsorb water

Oxytocin- stimulates the contraction of uterine muscles during childbirth (positive feedback), and stimulates milk release in breastfeeding

Both are peptides

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57
Q

How is the anterior pituitary connected to the hypothalamus?

A

By blood vessels

58
Q

How does the hypothalamus communicate with the anterior pituitary?

A

Stimulus arrives at cell body of neurons in hypothalamus,

releasing hormone is made and travels down blood vessel to anterior pituitary

59
Q

What do the hormones released by the hypothalamus do?

A

They are releasing/ inhibiting hormones

So they move down the portal system to the anterior pituitary, bind to receptor on membrane of the cell

There, a specific peptide hormone is secreted

60
Q

Describe feedback regulation of the anterior pituitary gland

A

Level of hormone secreted by target organ controls (feeds back) secretion of both releasing and pituitary hormone

61
Q

GH-RH and what it’s secreted by

A

Growth hormone releasing hormone

GHRH neurons

62
Q

GH-RH and what secreted it

A

Growth hormone inhibitory hormone/ somatostatin

Somatostatin neurons

63
Q

Which cells does growth hormone target?

A

Liver, muscle and fat cells

64
Q

IGF-1

A

Insulin-like growth factor-1 / somatomedin C

A hormonal growth factor secreted by the liver

65
Q

Direct effects of growth hormone on muscle, liver and fat cells

A

Muscle: stimulates protein synthesis (long term), inhibits cellular uptake of glucose (short term)

Liver: stimulates glucose synthesis (short term)

Fat: increases triglyceride breakdown in adipose tissue (short term)

66
Q

Indirect effects of growth hormone/ effects of somatomedin C

A

Promotes cell division

67
Q

What is growth hormone’s long-term and short-term effect in general?

A

Long term effect on growth

Short term effect on metabolism

68
Q

Term for gluconeosynthesis

A

Glucose synthesis

69
Q

When is growth hormone concentration the highest? (2)

A

During sleep

During puberty

70
Q

Where is the thyroid?

A

Just below the larynx, on the anterior and lateral surfaces of the trachea

71
Q

Which main hormone is made and secreted from the thyroid gland?

Function

A

Thyroid hormone- essential for optimal metabolic activity

72
Q

Describe three cellular components of the thyroid gland

A

Follicles- small fluid filled sacs

Follicular cells surrounding follicles- site of thyroid hormone synthesis

Follicular space- in between follicles and follicular cells

73
Q

TGB protein- where’s it made?

A

Thyroglobulin protein is made in thyroid follicles

74
Q

What has to happen before thyroid hormones can detach from TGB?

A

Iodine enters follicle cell from the blood and reacts with tyrosine

75
Q

Two types of thyroid hormones

A

T3- the active form
T4- the more plentiful form

Number shows how many tyrosines are attached

T4 can be turned into T3

76
Q

How do T3 and T4 travel to target cells and why?

A

They’re lipid-soluble hormones so they travel through the blood bound to a carrier protein called thyroid-binding globulin (TBG)

77
Q

Why is iodine a necessary part of our diet?

A

Because it is required for the production of thyroid hormone

78
Q

Where is the receptor for T3? Why?

A

In the nucleus, bound to a specific DNA site

So gene transcription can occur straight away, as soon as T3 bonds to the receptor

79
Q

Response time of thyroid hormone

A

45 minutes- days

80
Q

Is thyroid hormone secretion stimulates by internal or external stimuli?

A

Both- which lead to CNS input at the hypothalamus

81
Q

What two hormones are secreted before thyroid hormones and where?

A

TRH thyrotropin-releasing hormone (hypothalamus)

TSH thyrotropin-stimulating hormone (anterior pituitary)

82
Q

Effects of increased thyroid hormones

A

Increased basal metabolic rate

Stimulates growth and effects alertness and reflexes

83
Q

BMR and basal conditions

A

Basal metabolic rate

The body’s rate of energy expenditure under basal conditions

  • awake
  • physical and mental rest
  • lying down
  • no muscle movement
  • comfortable temperature
  • fasted
84
Q

What happens to a persons BMR throughout their lifetime?

A

Decreases

85
Q

Specific effects of thyroid hormone on metabolism (5)

A

Increases body heat production

Stimulates fatty acid oxidation (stored fat usage)

Increases proteolysis (breakdown of proteins)

Stimulates carbohydrate metabolism (stored glucose usage)

Increase gluconeogenesis and glycogenolysis (formation of glucose)

86
Q

Why does thyroid hormone not cause significant increase in blood glucose?

A

There’s a balance between glucose breakdown and formation

87
Q

How is calcium normally gained and lost in the body?

A

Gained through diet (1000mg/day)

Lost through faeces and urine (1000mg/day)

88
Q

Where is calcium stored in the body?

A

Absorbed by digestive tract and stored in blood plasma and bone

89
Q

Two functions calcium is essential for

A

Contraction of muscles

Release of neurotransmitters

90
Q

Name a hormone involved in calcium regulation

A

PTH parathyroid hormone

91
Q

Where is PTH produced?

A

In thyroid follicles in the parathyroid glands

92
Q

What stimulates the parathyroid gland?

A

A decrease in blood calcium concentration

93
Q

What effect does PTH have on the kidneys?

A

Increases calcium reabsorption- which decreases urinary excretion of calcium

Converts vitamin D to calcitriol- which increases absorption of calcium from food (reducing loss in faeces)

94
Q

What effect does PTH have on bone?

A

Increase bone breakdown- which increases the release of calcium into the blood

95
Q

Which hormonal release pathway is not controlled by the hypothalamus?

A

PTH (parathyroid hormone)

96
Q

Two separate glands of the adrenal gland

A 
Adrenal cortex (outer)- secretes steroid hormones
Adrenal medulla- secretes adrenaline
97
Q

Where are the adrenal glands located?

A

Superior to each kidney

98
Q

Which hormone does the adrenal cortex secrete?

A

Cortisol

99
Q

Adrenal medulla is part of the _______ ________ system

A

Sympathetic nervous

100
Q

In times of stress, how does the adrenal medulla respond?

A

Secretes noradrenaline (20%) and adrenaline (80%)

101
Q

Explain the two pathways of adrenaline + noradrenaline secretion

A

Pre and post-ganglionic fibres synapse in the adrenal medulla secretory cells, where post fibre secretes adrenaline and noradrenaline (travels through bloodstream to target cell)

  1. Pre and post ganglion of fibres synapse in adrenal medulla secretory cell- BUT axons of post fibres extend to target cell, where noradrenaline is secreted
102
Q

What is adrenaline?

A

A catacholamine

Water soluble hormone

Uses a second messenger system- which amplifies the cellular response- and is fast

103
Q

Pathway of adrenaline secretion

A

Stress stimulates hypothalamus to send neural signal to sympathetic preganglionic fibres

These stimulate the adrenal medulla to secrete adrenaline- which travels in the blood to target cells

104
Q

Effects of adrenaline (3)

A

Increases breakdown of glycogen to glucose in muscle in liver

Increases breakdown of fat to fatty acids in fat cells

(Make fuel more readily available to cells)

Systems not crucial for short term survival are shut down

105
Q

What kind of hormone is cortisol?

A

Lipid-soluble steroid hormone

106
Q

How does cortisol travel in the blood?

A

Bound to a carrier protein

107
Q

Where is the cortisol receptor?

A

In the cytoplasm of the target cell

108
Q

Is the effect of cortisol fast or slow?

A

Slow (hours to days)

109
Q

Which two hormones lead to the release of cortisol and where are they released?

A

CRH (corticotropin releasing hormone) in the hypothalamus

ACTH (adrenocorticotropic hormone) in the anterior pituitary

110
Q

Is cortisol stored, or produced when needed? Why?

A

Produced when needed, because it is a steroid hormone

111
Q

If not undergoing stress response, the cortisol secretion of the body is mainly controlled by ______ _______

A

Negative feedback

112
Q

Metabolic effects of cortisol (3)

A

Increase in protein and fat breakdown (in muscles and fat respectively)

Decreases in glucose uptake (in muscles and fat)

Increase in glucose synthesis (gluconeogenesis) in the liver

113
Q

Other effects (non-metabolic) of cortisol (3)

A

Helps to cope with stress

Suppresses immune system (long term)

Maintains blood pressure

114
Q

When in the day is cortisol secretion the highest?

A

Upon waking

115
Q

What can affect daily pattern of cortisol secretion?

A

Disturbance to normal sleep schedule e.g. sleeping in, jet lag

116
Q

Overall functions of cortisol in the body (6)

A

Increased blood glucose

Increased metabolism to maintain blood glucose

Anti-inflammatory actions

Increased blood pressure

Increased heart and blood vessel contraction

Activation of CNS

117
Q

Hyposecretion

A

Too little or zero level of hormone in the blood

118
Q

Hypersecretion

A

Too much hormone in the blood

119
Q

Hyposensitive

A

Little or no response from a hormone receptor

120
Q

Hypersensitive

A

Too large of a response from a hormone receptor

121
Q

Autoimmunity

A

Destruction of hormone receptors

122
Q

What can cause problems with hormone signalling? (3)

A

Autoimmunity

Genetic mutation: cause gain or loss of function

Tumours: excess tissue can lead to too much or not enough hormone release

123
Q

Low cortisol concentration leads to _________ secretion

What does this cause? (2) (Addisons disease)

A

Increase in ACTH

Low blood pressure
Weakness (due to lack of fuel)

124
Q

What three symptoms can too much cortisol cause? (Cushings disease)

A

High blood pressure

Weakness (muscle being broken down)

Too much fat is broken down and deposited in different places

125
Q

How does the body respond to different kinds of stresses?

A

The same way

By activating the hypothalamus

Which activates the adrenal glands, sympathetic nervous systems and posterior pituitary

126
Q

Which three hormones are secreted in response to stress, and where? What is their common effect?

A

ADH (antidiuretic hormone) in the posterior pituitary

Adrenaline in the adrenal medulla

ACTH (adrenocorticotropin hormone) in the adrenal cortex

Increase in blood pressure

127
Q

What causes gigantism?

A

Hypersecretion of growth hormone

128
Q

What can cause dwarfism?

A

Hyposecretion of growth hormone

129
Q

What is infantile hypothyroidism caused by? What are the effects? (4)

A

Hyposecretion of thyroid hormone (usually due to lack of iodine in mothers diet)

Low metabolic rate
Cold intolerance
Retarded growth
Inhibited brain development

130
Q

What cause iodine deficiency disorder? What is the other name for it? What are its effects?

A

Hyposecretion of thyroid hormone due to lack of iodine in the diet

Simple goitre

TRH and TSH secretion increases to try and secrete more thyroid hormone
- there is no negative feedback so instead the thyroid gland grows

131
Q

How have we added more iodine to our diets in NZ and why?

A

Low levels of iodine in our soil so we don’t get enough through produce

Added iodine into table salt and now into commercially prepared bread

132
Q

What is Graves’ disease caused by? What are two symptoms?

A

Hypersecretion of thyroid hormone due to an autoimmune disorder
- where antibodies act like TSH

High metabolic rate
Weight loss
Thyroid swelling
Heat intolerant
Hair loss
Increased heart rate
133
Q

What is hyperparathyroidism, what causes it, and what are its effects?

A

Hypersecretion of parathyroid hormone, caused by a parathyroid tumour (usually), so the cells are no longer under control (negative feedback doesn’t work)

Raises blood calcium and phosphate
Bones become soft and deformed
Promotes kidney stone formation

134
Q

Hypercalcaemia and it’s effects

A

Blood calcium is too high

Nerve and muscle cells are less responsive/ excitable (because they’re far away from threshold)

Muscle weakness
Sluggish reflexes

Can potentially lead to cardiac arrest

135
Q

Hypocalcaemia and its effects

What is it caused by?

A

Blood calcium is too low

Increased excitability of the nervous system (always at threshold)

Spontaneous nerve firing
Muscle cramps
Laryngospasm (larynx muscles contract)

Caused by excess loss of calcium through faeces

  • vitamin D deficiency (gut doesn’t absorb)
  • diarrhoea
136
Q

Diabetes mellitus- two types

A

Type 1- hyposecretion of insulin

Type 2- insulin receptors are hyposensitive to insulin

137
Q

What is type 1 diabetes caused by, and what are its effects?

How is it treated?

A

Can be caused by destruction of the pancreatic beta cells by the immune system

Glucosuria (excess glucose in urine)
Thirst
Heart problems

Insulin injections/ infusion

138
Q

What is type 2 diabetes caused by, and what are its effects?

How is it treated?

A

Desensitisation of insulin receptor causes ‘insulin resistance’ (usually due to a high sugar diet/ obesity)

Same effects as type 1- glucosuria, thirst, heart problems

Changes in diet and exercise

139
Q

What happens if we have a hyper or hyposecretion of glucagon?

A

Other hormones will increase blood glucose

140
Q

When might you need a change in set point for a hormone? (3)

A

Change in altitude (blood count)
Change in climate (BMR)
Fever (temporary)

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