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HUBS 191 > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

What is homeostasis?

A

The presence of a stable internal environment.

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2
Q

What can happen if homeostasis is not maintained?

A

It can lead to illness and even death

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3
Q

What is negative feedback and what is its purpose?

A

When an effector activated by the control system opposes, or negates, the original stimulus ie. it reduces the change until the stimulus is removed or it directly inhibits further release.
It tends to minimise change, keeping variation in key body systems within limits compatible with our long term survival.

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4
Q

What is positive feedback?

A

When an initial stimulus produces a response that exaggerates or enhances the change in the original conditions, rather than opposing it ie. there is an amplification of a change until a desired outcome is achieved

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5
Q

Describe how homeostasis in maintained

A

A change in these controlled variables is detected by a control centre and it signals effectors (organs or tissues). The effector responds to these signals by (usually) opposing the stimulus. These effects could be localised or the whole body.

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6
Q

What is the difference between a set point and a normal range?

A

The set point is the point where the body wants to be (eg. an internal temp of 37.5 degrees).
But the body never stays at this one point; it oscillate above and below this point. This is how we get the normal range.

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7
Q

Homeostatic control is not

A

precise

it maintains a normal range rather than an absolute value

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8
Q

What is the population reference range?

A

The population reference range is based on the width of individual normal ranges within a population, covering most of the people in a population and most of their normal ranges

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9
Q

How do individual normal ranges and population reference ranges differ?

A

The population reference range tends to be wider than normal fluctuations within an individual. Some people can still exhibit symptoms of disorder even though they are inside the population range because they are outside their own normal range.

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10
Q

Most individuals will have a set point that is

A

within the population reference range

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11
Q

Some people can still exhibit symptoms of disorder even though they are inside the population range because

A

they are outside their own normal range

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12
Q

Compare the neural and endocrine control systems

A
  • Synaptic:
    • action potentials in axons and neurotransmitter release at the synapse
    • targeting achieved by one neuron synapsing onto another to get that signal going where we want
    • fastest transmission speed to minimise response delays between signals and receptors
    • good for brief responses
  • Endocrine:
    • hormones released into the blood
    • targeting by presence of specific receptors on target cells
    • relatively slow but long lasting action
    • good for widespread and sustained responses
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13
Q

What does the endocrine system consist of?

A

endocrine gland cells that secrete hormones which are carried into the bloodstream to the target cells upon which they act on.

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14
Q

What are hormones?

A

chemical messengers that allow one cell type to communicate with another cell type without the use of neurons

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15
Q

What are the main endocrine glands? (6)

A
  1. hypothalamus
  2. pituitary gland
  3. thyroid gland
  4. adrenal glands
  5. pancreas (pancreatic islets)
  6. parathyroid glands
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16
Q

What is the role of the hypothalamus?

A

It links the nervous system to the endocrine system and controls the secretion of many endocrine glands

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17
Q

What are some physiological variables that are maintained homeostatically through hormones?

A
  • blood sugar concentration
  • growth and repair
  • basal metabolic rate (how much energy our body uses)
  • blood calcium concentration
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18
Q

What is a true hormone?

A

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

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19
Q

What are three mechanisms of cellular communication?

A

paracrine communication
autocrine communication
endocrine communication

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20
Q

Describe paracrine communication

A

A cell releases things (paracrines) into the extracellular fluid. Actions of paracrines are limited to nearby the releasing cells

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21
Q

Describe autocrine communication

A

A cell releases things into the EC fluid (autocrines). They only act upon the cell that secreted them.

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22
Q

Describe endocrine communication

A

It is through the bloodstream and the chemical signals are hormones. These target cells for the hormones are often in very distant tissues and organs from the cell that released the hormone

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23
Q

What is a receptor?

A

A protein that can be in the plasma membrane or inside the cell that allows a hormone to target that cell

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24
Q

What is a target cell?

A

A cell that the hormone acts upon to create a response

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25
Q

What are the two types of hormones?

A

water-soluble hormones

lipid-soluble hormones

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26
Q

Describe water-soluble hormones and give two examples

A

they can not cross the plasma membrane because they are water soluble
the receptors are located in the plasma membrane
eg. peptides and catecholamines

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27
Q

Describe lipid-soluble hormones and give two examples

A

they can diffuse across the cell membrane into the target cell
the receptors are located in the cytoplasm or nucleus
eg. steroid and thyroid hormones

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28
Q

Describe water-soluble hormone receptor activation

A
  • water soluble hormone binds to the receptor surface (which is on the plasma membrane)
  • this allows the activation of the intracellular protein G-protein
  • this causes one of three responses: adenylyl cylase is activated or inhibited, or intracellular Ca2+ ions
  • these cause a SECOND MESSENGER production or reduction (eg. an increase or decrease of cAMP, or increase in Ca2+ acting as second messenger)
  • cAMP and Ca2+ cause downstream proteins and pathways to be activated or deactivated
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29
Q

Describe lipid-soluble hormone receptor activation

A
  • the lipid-soluble hormone dissociates from a carrier protein
  • the hormone diffuses across the cell membrane to reach receptors
  • the hormone binds to intracellular receptors (in the cytoplasm or nucleus)
  • the hormone-receptor complex acts as a specific transcription factor (ie. it moves onto DNA and binds to a particular region of the DNA)
  • this causes a target gene to be activated
  • mRNA is generated. It moves out of the nucleus into the cytoplasm
  • a new protein is generated by the translation on mRNA
  • the new protein mediates cell specific responses
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30
Q

How does the chemical classification of water-soluble and lipid soluble hormones differ?

A

water-soluble:

  • peptides (most abundant)
  • catecholamines

lipid-soluble:

  • steroids
  • thyroid hormones
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31
Q

How does the storage of water-soluble and lipid soluble hormones differ?

A

water-soluble:
- stored until they are required (released by exocytosis)

lipid-soluble:

  • steroids made from cholesterol as required (not stored)
  • thyroid hormones are made in thyroid cells and stored until required
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32
Q

How does the transport of water-soluble and lipid soluble hormones differ?

A

water-soluble:
- dissolved into the blood

lipid-soluble:
- bound to a carrier protein

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33
Q

How do the receptors of water-soluble and lipid soluble hormones differ?

A

water-soluble:
- on the cell surface

lipid-soluble:
- intracellular receptors in cytoplasm or nucleus

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34
Q

How does the mechanism of action of water-soluble and lipid soluble hormones differ?

A

water-soluble:
- through second messengers

lipid-soluble:
- by altering gene transcription and causing the formation of new proteins

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35
Q

How does the speed of response of water-soluble and lipid soluble hormones differ?

A

water-soluble:
- milliseconds to minutes

lipid-soluble:
- hours to days

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36
Q

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

A
  • rate of human secretion

- rate of removal from blood

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37
Q

The removal of hormones from the blood is controlled by

A

enzymes in the blood or in target cells

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38
Q

The goal of a hormone is to

A

maintain homeostasis

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39
Q

Secretion is usually controlled by a

A

negative feedback loop

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40
Q

Describe the exocrine gland of the pancreas

A
  • 99% of the organ’s volume
  • cells of pancreatic acini secrete digestive enzymes
  • secrete alkaline, enzyme rich fluid that reaches the lumen of the intestinal tract through one or more pancreatic ducts
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41
Q

Describe the endocrine gland of the pancreas

A
  • about 1% of the organ’s volume
  • consists of pancreatic islets
  • contain β cells and α cells
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42
Q

What do β cells secrete?

A

insulin

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43
Q

What do α cells secrete?

A

glucagon

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44
Q

What can happen if homeostasis is not maintained and blood glucose concentration gets too high for too long?

A

Diabetes

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45
Q

What can happen if homeostasis is not maintained and blood glucose concentration gets too low for too long?

A

Hypoglycaemia

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46
Q

What is the only source of energy that the brain uses?

A

glucose

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47
Q

What are the two metabolic states?

A

fed state

fasting state

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48
Q

What happens during the fed state?

A
  • cellular uptake of nutrients
  • anabolic metabolism (making molecules)
  • synthesis of glycogen, protein and fat
  • glucose is moved from our bloodstream into a storage system which we can then access later when we are in the fasting state
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49
Q

What is the fed state?

A

a metabolic state when we have just eaten

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50
Q

What is the fasting state?

A

after long periods of not eating

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51
Q

What happens during the fasting state?

A
  • mobilisation of nutrients
  • catabolic metabolism (breaking down molecules)
  • breakdown of glycogen, protein and fat
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52
Q

Insulin and glucagon try and maintain a blood concentration between

A

70-110 mgdL-1

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53
Q

Describe how the body maintains homeostasis after an increase in blood concentration

A
  • the β cells secrete insulin into the bloodstream
  • insulin travels to target cells
  • decrease in blood glucose concentration
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54
Q

What role do the β cells have in releasing insulin

A

as both the sensor and control centre

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55
Q

What are the target cells for insulin?

A

Muscle and adipose cells

liver cells

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56
Q

Insulin being released to reduce the blood glucose concentration is an example of:

A

negative feedback control because by decreasing the blood glucose concentration, we remove the stimulus (an increased blood sugar concentration) and so now without that stimulus, the β cells are going to stop secreting insulin

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57
Q

Insulin is a _______-________ _________ hormone and the target cells have _________ receptors

A

water-soluble
peptide
membrane

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58
Q

What effect does insulin have on muscle cells?

A
  • increase in net glucose uptake
  • increase in amino acid uptake
  • uses amino acids and glucose to make proteins
  • converts glucose to glycogen
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59
Q

What effect does insulin have on adipose cells?

A
  • increase in net glucose uptake

- fat synthesis

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60
Q

What effect does insulin have on liver cells?

A
  • prevents further production of glucose in the liver (stops glycogen –> glucose)
  • increase in net glucose uptake
  • glycogen and fat synthesis
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61
Q

What are 5 effects of insulin on the target cells?

A
  1. increased rate of glucose transport into target cells
  2. increased rate of glucose use and ATP generation
  3. increased conversion of glucose to glycogen
  4. increased amino acid absorption and protein synthesis
  5. increased triglyceride (fat) synthesis in adipose tissue
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62
Q

Describe how the body maintains homeostasis after a decrease in blood concentration

A
  • the α cells secrete glucagon
  • glucagon travels to the target cells
  • increase in blood glucose concentration and blood ketone concentration
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63
Q

What role do the α cells have in releasing glucagon?

A

the sensor and the control centre

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64
Q

What are the target cells for glucagon?

A

liver cells

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65
Q

Glucagon being released to increase the blood glucose concentration is an example of:

A

Negative feedback loop because by increasing the blood glucose concentration, we remove the stimulus (a decreased blood sugar concentration) and so now without that stimulus, the α cells are going to stop secreting glucagon

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66
Q

Glucagon is a _______-________ _________ hormone and the target cells have _________ receptors

A

water-soluble
peptide
membrane

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67
Q

What effect does glucagon have on liver cells?

A
  • increased breakdown of glycogen to glucose
  • increased glucose synthesis
  • increased ketone synthesis
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68
Q

What is the breakdown of glucose called?

A

Glycogenolysis

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69
Q

What is glycogenolysis?

A

The breakdown of glucose

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70
Q

What is glucose synthesis called?

A

Gluconeogenesis

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71
Q

What is gluconeogenesis?

A

Glucose synthesis

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72
Q

What are the two distinct parts of the pituitary gland?

A
  • anterior lobe

- posterior lobe

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73
Q

Where is the pituitary gland located?

A

at the base of the hypothalamus, attached through the narrow infundibulum

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74
Q

What does the hypothalamus control?

A

the secretion of pituitary hormones (when activated by neural input, the hypothalamus stimulates the pituitary gland to secrete hormones)

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75
Q

How does the hypothalamus communicate with the posterior pituitary?

A
  • hypothalamus connected to PP by neurons

- the cell bodies in the hypothalamus and the axon terminate in the posterior lobe

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76
Q

Where are posterior pituitary hormones made?

A

in the hypothalamus

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77
Q

Describe the release of hormones from the posterior pituitary gland

A
  • PP hormones are made in the hypothalamus in the cell body of the axons
  • the hormones travel down the axon and are stored at the axons terminals until required
  • the hypothalamus uses neural communication with the posterior lobe to release hormones into the blood (an increase or decrease in the frequency of action potentials leads to a change in hormone release)
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78
Q

What are the peptide hormones that are released from the posterior pituitary gland?

A
  • antidiuretic hormone (ADH)

- oxytocin (OXT)

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79
Q

What does ADH do?

A

stimulates the kidneys to absorb water (the kidneys conserve water when the body dehydrates)

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80
Q

What does oxytocin do?

A
  • stimulates the contraction of uterine muscles during childbirth
  • stimulates milk release in breastfeeding
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81
Q

The hormones released by the posterior pituitary gland are _______ hormones and are stored _______ ________

A

peptide

until required

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82
Q

Describe the release of hormones from the anterior pituitary gland

A
  • a neural input (stimulus) conducted down a short axon in the hypothalamus causes the release of releasing hormones from the hypothalamus
  • this is released into the portal veins which carries the the hormone into the AP
  • the hormone binds to receptors on specific cells types and a specific peptide hormone is secreted from the AP into the bloodstream
83
Q

What are some peptide hormones released from the anterior pituitary gland?

A

Prolactin and growth hormone

84
Q

Describe the feedback regulation of the anterior pituitary gland

A
  • the hypothalamus secretes a releasing hormones
  • the releasing hormones stimulate the release of a peptide hormone from the anterior pituitary hormone
  • the peptide hormone causes the release of another hormone which causes an effect (releases another hormone)
  • the hormone released by the target organ heads back to the hypothalamus and anterior pituitary to stop further release of the releasing hormones and pituitary hormone
  • the peptide hormone also feeds back to the hypothalamus to stop release (and can also sometimes cause further release of itself)
85
Q

When are growth hormone concentrations are highest? (in a day)

A

During the night

86
Q

When are growth hormone concentrations are highest? (in a lifetime)

A
  • higher in children than adults and they peak in puberty

- secretion declines with ageing

87
Q

Describe the release of the growth hormone from the anterior pituitary gland

A
  • the hypothalamus has growth hormone releasing hormone (GH-RH)
  • the GH-RH travels into the portal veins into the anterior pituitary gland which releases the growth hormone
  • this travels to the muscle and fat cells which have direct effects and to the liver cells
  • the liver releases Somatomedin C (IGF-1) which have indirect effects
88
Q

What does the Somatomedin C (IGF-1) do?

A

It feedbacks to the hypothalamus and inhibits further release of GH-RH. It also feedbacks to somatostatin neurons which release GH-IH. The signal goes through the portal veins to reduce the release of GH (negative feedback)

89
Q

What are some direct effects of the growth hormone on muscle cells?

A

Stimulates protein synthesis and inhibits cellular uptake of glucose

90
Q

What is protein synthesis important for?

A

Growth

91
Q

What are some direct effects of the growth hormone on liver cells?

A

stimulates glucose synthesis

92
Q

What are some direct effects of the growth hormone on fat cells?

A

increases triglyceride breakdown in adipose tissue so that they can be used by other parts of the body for energy

93
Q

What are some indirect effects of the growth hormone?

A

It promotes the growth of bones, muscle and other tissue by causing release of Somatomedin C which promotes cell division

94
Q

How does the hypothalamus communicate with the anterior pituitary gland?

A

using releasing and inhibiting hormones via the portal veins

95
Q

What are some indirect growth (long-term) effects of growth hormone?

A
  • stimulates the growth of bones and muscles by stimulating cell division via insulin-like growth factor (IGF1)
96
Q

What is cell division called?

A

mitogenesis

97
Q

What are some direct growth (long-term) effects of growth hormone?

A

stimulates protein synthesis in muscles

98
Q

What are some direct metabolic (short-term) effects of growth hormone?

A
  • increases blood glucose by stimulating glucose synthesis (in the liver) and inhibiting cellular uptake of glucose
  • increasing triglyceride breakdown and free fatty acid mobilisation in adipose tissue
99
Q

Where is the thyroid gland?

A

just below the larynx on the anterior and lateral surfaces of the trachea

100
Q

What are the hormones made and secreted from the thyroid gland?

A
  • thyroid hormone

- calcitonin

101
Q

What is the thyroid hormone essential for?

A

optimal metabolic activity

102
Q

What is calcitonin essential for?

A

calcium homeostasis

103
Q

Describe the structure of the thyroid gland

A
  • it is composed of small spherical sacs called follicle
  • each follicle is surrounded by follicular cells and this is the site of thyroid hormone synthesis
  • the clear cells (C cells) are where calcitonin is made
104
Q

What are follicular cells?

A

simple cuboidal cells where the thyroid hormone is synthesised

105
Q

Describe thyroid hormone synthesis:

A
  • Iodine enters the follicular cell from the blood
  • it travels into the follicle cavity (follicle) in vesicles containing thyroglobulin (TGB)
  • the iodine reacts with tyrosine in the TGB molecules (this takes place in the follicle cavity)
  • iodised TGB moves into the follicular cells
  • thyroid hormones detach from TGB as needed (T3 and T4)
  • T3 and T4 travel bound to a carrier protein (TBG) to target cells
106
Q

What does TGB stand for?

A

thyroglobulin

107
Q

What does TBG stand for?

A

carrier protein thyroid-binding globulin

108
Q

What is T3?

A

the active form of the thyroid hormone which has 3 iodines attached

109
Q

What is T4?

A

the inactive form of the thyroid hormone which has 4 iodines attached

110
Q

How is a target cell activated by the thyroid hormone?

A
  • T3 is carried to the target cell bound to TBG
  • it detaches from TBG and enters the target cell
  • T3 binds to the T3 receptor in the nucleus
  • specific genes are activated to transcribe mRNA
  • mRNA translation occurs in the cytoplasm and specific proteins are synthesised
111
Q

Thyroid hormones are made ______ _______ and stored _______ __________

A

in advance

until required

112
Q

What is an example of a protein synthesised due to the thyroid hormone?

A

Na+/K+ ion pumps

113
Q

What is the response time of the target cells due to the thyroid hormone?

A

45 mins to days

114
Q

Due to the thyroid hormone, we can get an increase in genes being expressed from DNA in both the _______ and the ________

A

mitochondria

nucleus

115
Q

How is the release of the thyroid hormone controlled?

A
  • after an external or internal stimulus lead to CNS input to hypothalamus
  • the hypothalamus secretes TRH into the portal veins between the hypothalamus and the anterior pituitary gland
  • the anterior pituitary gland secretes TSH
  • this travels around the body until it reaches the thyroid gland
  • the thyroid gland releases TH (T3 and T4) into the blood
  • T3 has effects around the body
  • T3 and T4 also inhibit the the further release TSH and TRH
116
Q

What is TRH?

A

thyrotropin-releasing hormone and it is secreted by the hypothalamus

117
Q

What is TSH?

A

thyroid-stimulating hormone which is released by the anterior pituitary gland

118
Q

What is TH and what are some examples?

A

Thyroid hormones T3 and T4 released by the thyroid gland

119
Q

What are some of the effects of T3 around the body?

A

It increases basal metabolic rate by increasing the synthesis and activity of the Na+,K+ pump

120
Q

What are some other effects of thyroid hormones in the body?

A
  • stimulates growth (foetus and early childhood)

- promotes normal alertness and reflexes in the nervous system

121
Q

What is the basal metabolic rate?

A

The body’s rate of expenditure under basal conditions

122
Q

What are basal conditions?

A
  • awake
  • at physical and mental rest
  • lying down
  • no muscle movement
  • at a comfortable temperature
  • fasted (12-18 hr)
123
Q

How does the thyroid hormone affect metabolism?

A
  • increases body heat production by increasing oxygen consumption and ATP hydrolysis
  • Stimulates fatty acid oxidation (usage of storage fat) in many tissues
  • increases proteolysis from muscle
  • stimulates carbohydrate metabolism (usage of stored glucose) and enhances insulin-dependent entry of glucose into cells which increases gluconeogenesis and glycogenolysis
124
Q

What is proteolysis?

A

Protein breakdown

125
Q

In the presence of insulin and TH, cells tend to take up even more of the ______ ______ and increases the production of ________ and increases the breakdown of ______

A

blood glucose
glucose
glycogen

126
Q

TH does not cause a significant increase in blood glucose because

A

There is a balance between the increase in production of glucose and the uptake/usage by cells

127
Q

Where does calcium come from?

A
  • in our diet
  • some is absorbed into our intestines, some is removed in the faeces
  • of that absorbed into our intestines, some is absorbed into the plasma, some is filtered into the kidneys and some is deposited into the bones by osteoblasts
  • of that filtered into the kidneys, some is reabsorbed into the plasma and some is lost as urine
  • of that deposited in our bone, some of it remains and some of it is reabsorbed into the plasma by osteoclasts
128
Q

What is calcium important for?

A

contraction of muscles and release of neurotransmitters

129
Q

What is the body’s major store of calcium?

A

bone

130
Q

Normally, a balance exists between the _______ _____-_________ of bone and the ________ of bone

A

constant build-up

breakdown

131
Q

What are the three hormones involved in calcium regulation?

A

Parathyroid hormone (PTH)
Calcitriol
Calcitonin

132
Q

Where are the parathyroid glands?

A

Little bean-like structures on the posterior aspect of the thyroid gland

133
Q

What does the parathyroid glands do?

A

secrete PTH

134
Q

How is blood calcium concentration maintained?

A

eg. for a decrease in blood Ca2+ concentration:
- this is detected by the parathyroid gland
- it secretes the PTH which affects the kidneys, the bones and the intestines
- this causes an increase in Ca2+ concentration so it is a negative feedback control

135
Q

How does PTH affect the kidneys?

A
  • there is increased Ca2+ reabsorption into the plasma

- this decreases the urinary excretion of calcium

136
Q

How does PTH affect the bone?

A
  • there is an increase in bone breakdown

- this increases the release of Ca2+ into the blood (resorption)

137
Q

How does PTH affect the intestines?

A
  • PTH encourages the conversion of vitamin D to calcitriol
  • Calcitriol travels in the blood to the intestines
  • this increases the increase of Ca2+ absorption from food
138
Q

How does the conversion of Vitamin D to calcitriol affect the bone breakdown, kidney Ca2+ reabsorption and its own conversion?

A

The conversion of vitamin D to calcitriol further increases the breakdown of bone and the reabsorption of Ca2+ from the kidneys.
Once we reach a certain level of vitamin D conversion to calcitriol, it stops further conversion

139
Q

Where are the adrenal glands located?

A

superior to each kidney

140
Q

What is are the adrenal glands made of?

A

Two separate glands

141
Q

What are the two glands that make up the adrenal glands called?

A

Adrenal cortex

Adrenal medulla

142
Q

Describe the adrenal cortex

A
  • 3 layers

- secretes steroid hormones

143
Q

What does the outer layer of the adrenal cortex secrete?

A

aldosterone to help maintain sodium homeostasis

144
Q

What does the middle layer of the adrenal cortex secrete?

A

cortisol

145
Q

What does the inner layer of the adrenal cortex secrete?

A

androgens which have a minor reproductive role

146
Q

Describe the adrenal medulla

A
  • part of the sympathetic nervous system

- secretes adrenaline

147
Q

Describe the response to stress in terms of the release of noradrenaline (norepinephrine) and adrenaline

A

NORADRENALINE:
- an action potential is propagated along the axon of a sympathetic preganglionic neuron starting in the hypothalamus in response to stress
- there is a synapse onto a sympathetic post-ganglionic neuron at the sympathetic chain ganglia
- there is a release of noradrenaline (norepinephrine -NE) at the target or effector cell
ADRENALINE:
- an internal or external stimulates a stress response which is assessed in the hypothalamus
- the hypothalamus propagates an action potential along a sympathetic preganglionic neuron
- when the action potential reaches the adrenal medulla, ACh is released
- this stimulates the adrenal medulla to secrete adrenaline (80%) and noradrenaline (20%) into the bloodstream
- this travels in the blood to target cells

148
Q

Describe adrenaline

  • water-soluble or lipid-soluble?
  • what derivative is it?
  • what sort of receptor does it have?
  • how does it amplify cellular response
  • does it acts fast or slow?
A
  • water-soluble hormone
  • amino acid derivative
  • has a cell membrane receptor
  • uses a second messenger system to amplify cellular response
  • acts fasts
149
Q

What effect does adrenaline have in response to stress?
In the skeletal muscle and liver cells?
In fat cells?
Other effects?

A

Makes fuel more readily available for the cells.
In skeletal muscle and liver cells:
- increased breakdown of glycogen to glucose
In fat cells:
- increased breakdown of fat to fatty acids
Other effects:
- systems not crucial for short term survival are shut down

150
Q

What are the target cells of adrenaline?

A

skeletal muscle
liver
fat

151
Q

Adrenaline and norepinephrine secretion is stimulated by

A

sympathetic preganglionic fibres during sympathetic activation

152
Q

What happens if the concentration of Ca2+ in plasma gets too high?

  • amount released?
  • bone?
  • kidneys?
  • Vit D?
A
  • there is a decrease in the release of PTH
  • decrease in the breakdown of bone
  • decrease in the reabsorption of Ca2+ from the kidneys
  • reduces conversion of Vit D to calcitriol
153
Q

What does calcitonin do?

A

If the plasma Ca2+ concentration gets way too high, calcitonin will be administered to immediately stop bone breakdown

154
Q

What is cortisol?

A

Steroid hormone that is released in everyday life but can also be released in response to stress and non-stress stimuli

155
Q

Describe the action of cortisol at a target cell
- how is it carried in the blood?
- how does it get into the cell?
explain the process (ie. is it a lipid-soluble or water soluble hormone)

A
  • cortisol is carried in blood bound to a carrier protein
  • it travels to the target cell and passes through the cell membrane
  • it binds to a receptor in the cytoplasm
  • the receptor complex travels into the nucleus of the cell
  • cortisol binds to DNA to activate genes to initiate RNA transcription
  • the RNA codes for a protein which has an effect in other cells
156
Q

What is the protein that carries cortisol to the target cell?

A

cortico-steroid binding globulin

157
Q

Describe the process to secrete cortisol from the time of input to the time of cortisol carried in the blood

A
  • due to a non-stress neural input, the hypothalamus secretes CRH
  • the CRH travels in the portal veins to the anterior pituitary glands
  • this causes the AP to secrete ACTH
  • ACTH travels in the bloodstream to the adrenal cortex
  • the adrenal cortex secretes cortisol
158
Q

What are non-stress neural inputs?

A

Everyday day-night rhythms when we have low blood glucose concentration

159
Q

What does CRH stand for and what does it do?

A

It stands for corticotropin releasing hormone and it is released from the hypothalamus in response to a non-stress neural input (or in response to stress)

160
Q

What does ACTH stand for and what does it do?

A

It stands for adrenocorticotropin hormone and it travels to the adrenal cortex to stimulate the release of cortisol

161
Q

What cells does cortisol have an effect on?

A
  • muscle
  • fat
  • liver
162
Q

What effect does cortisol have on muscle cells?

A
  • increase protein breakdown to utilise amino acids

- decrease of glucose uptake

163
Q

What effect does cortisol have on fat cells?

A
  • increases fat breakdown
  • releases lipids
  • decrease of glucose uptake
164
Q

What effect does cortisol have on liver cells?

A

increase in gluconeogenesis

165
Q

Overall, cortisol has what sort of effect on its target cells?

A

it has metabolic effects and it affects the use of fuel

166
Q

Apart from the effects on muscle, liver and fat cells, cortisol has what other effects?

A
  • it can help one cope with stress
  • it can suppress the immune system in the long term
  • it is essential for maintaining normal blood pressure
  • it also inhibits the further release of ACTH and CRH
167
Q

How does cortisol affect the immune system?

A

Cortisol decreases white blood cells so the number of antibodies decreases.
It increases inflammatory response. When we have an internal injury, we will be able to see this as redness or swelling but cortisol stops this response

168
Q

The secretion of cortisol under non-stress situations is an example of

A

negative feedback

169
Q

When is the secretion of cortisol the highest?

A

upon waking up

170
Q

What are some effects of cortisol in response to stress? (6)

A
  1. increasing blood glucose levels
  2. increasing fat, protein and carbohydrate metabolism to maintain blood glucose
  3. promoting anti-inflammatory actions (reducing inflammation)
  4. increasing blood pressure
  5. increasing heart and blood vessel tone and contraction
  6. activation of the CNS
171
Q

How can we have problems with hormone signalling?

A

we can have problems with the hormone levels or problems with the hormone receptors

172
Q

What is meant by “problems with hormone levels”?

A

Too much hormone is secreted or not enough is secreted

173
Q

What is is called when too much hormone is secreted?

A

Hypersecretion

174
Q

What is is called when not enough hormone is secreted?

A

Hyposecretion

175
Q

What can cause the problems with hormone signalling?

A
  • autoimmunity
  • genetic mutation
  • tumors
  • other
176
Q

What is meant by “problems with hormone receptors”?

A

There is too much response by the target cell to the hormone or not enough

177
Q

What is is called when there is too much response to a hormone?

A

Hypersensitive

178
Q

What is is called when there is not enough response to a hormone?

A

Hyposensitive

179
Q

What is meant by autoimmunity causing problems with hormone signalling?

A

There is a destruction of the receptors leading to a hyposensitive response

180
Q

What is meant by genetic mutation causing problems with hormone signalling?

A

mutations can cause gain or loss of function

181
Q

What is meant by tumors causing problems with hormone signalling?

A

excess tissue usually leads to excess hormone release, but it can sometimes prevent release

182
Q

How can tumors both increase and decrease the hormone release?

A

INCREASE:
There is excess thyroid tissue which may be also be increasing the release of a hormone but because it is a tumorous tissue, it may not be under the same regulatory control as the normal thyroid tissue.
DECREASE/PREVENTION:
The excess tissue may push onto other glands which decreases the secretion from those glands. For example, If you get a tumor in your thyroid gland, you may get a hypersecretion of one of the hormones released from the thyroid gland but a reduction of release from the parathyroid gland as the thyroid gland becomes pressed against the parathyroid

183
Q

Give an example of a disease due to the reduction in cortisol

A

Addison’s disease

184
Q

What caused a reduction in cortisol levels that can lead to Addison’s disease?

A

Hyposecretion due to autoimmunity and other factors

185
Q

Describe Addison’s disease including the symptoms

A
  • there is lowered secretion of both cortisol and aldosterone
  • a low cortisol level increases the release of ACTH (to try and increase cortisol levels)
  • there is a build up of ACTH in the body
  • excess ACTH stimulates melanin synthesis causing a darkening to the skin
  • other symptoms include low blood pressure and weakness
186
Q

Give an example of a disease due to the increase in cortisol

A

Cushing’s disease

187
Q

What caused an increase in cortisol levels that can lead to Cushing’s disease?

A

Hypersecretion due to tumors and other factors

188
Q

Describe Cushing’s disease including the symptoms

A
  • there is an increase in the secretion of cortisol
    Symptoms:
  • buffalo hump (deposition of fat on the upper back)
  • moon face (rounded face)
  • breaking down fat but it is not being utilised so there is a redistribution of fat
  • high blood pressure
  • weakness/muscle wasting
189
Q

What are some examples of stress?

A

mental stress (like taking an exam)
famine
overpopulation (fighting for resources)
natural disasters

190
Q

Outline the body’s response to stress

A
  • stress activates the hypothalamus
  • hypothalamus organises a response and activates the
    adrenal glands, sympathetic nervous system, posterior lobe of the pituitary gland
  • the body responds
191
Q

What are the three phases of stress?

A
  1. alarm phase
  2. resistance phase
  3. exhaustion phase
192
Q

Describe the alarm phase

A
  • “fight or flight”
  • the adrenal medulla secretes adrenaline and norepinephrine
  • there is general sympathetic activation
  • these cause some immediate short term responses to a crisis
193
Q

What are some immediate short term responses to a crisis in the alarm phase? (8)

A
  1. increased mental alertness
  2. increased energy use by all the cells
  3. mobilisation of glycogen and lipid reserves to form glucose
  4. changes in circulation away from areas that don’t need it
  5. reduction in digestive activity and urine production
  6. increased sweat gland secretion
  7. increased heart rate (and force of contraction) and respiratory rate
  8. changes in pupil diameter because we want increased awareness of surroundings
194
Q

Describe what happens to the heart during the resistance phase

A
  • cardiovascular disease and hypertension are linked to prolonged stress
  • the cardiovascular tissue is activated by adrenaline which means the heart will be working harder because it is contracting with more force as well as more often
  • it this happens for too often for too long, it might cause damage to the tissue
195
Q

Describe what happens to the muscles during the resistance phase

A
  • pain and various minor muscular twitches

- nervous tics are more noticeable under stress

196
Q

Describe what happens to the skin during the resistance phase

A
  • problems such as eczema and psoriasis
197
Q

Describe the exhaustion phase

A

When you experience a significant amount of stress for a really long amount of time
You run out of stores of energy - the heart is worked too hard for too long so may get a heart attack. Aldosterone is key because imbalance of ions in the body so there is less K+ ion fluid which is key to heart malfunction

198
Q

Describe an integrated stress response

A
  • a stress stimulates is notified by the hypothalamus
    1.
  • the hypothalamus secretes CRH which travels to the anterior pituitary gland
  • the AP secretes ACTH which travels in the blood to the adrenal cortex
  • the adrenal cortex synthesises and secretes cortisol
  • cortisol causes an increase in blood glucose (by gluconeogenesis) and an increase in blood pressure
    2.
  • from the hypothalamus, action potentials travel down the sympathetic preganglionic fibres and synapse in the adrenal medulla
  • the adrenal medulla secretes adrenaline
  • this causes an increase in blood glucose level (by glycogenolysis), increased heart rate and blood pressure
    3.
  • from the hypothalamus, action potentials travel down neural connections and synapse at the posterior pituitary gland
  • the PP secretes ADH
  • there is a decrease in water excretion, an increase in blood volume and pressure
199
Q

Give examples of diseases due to the increase and decrease in growth hormone

A

when too much GH is released - gigantism

when not enough GH is released - dwarfism

200
Q

Give an example of what can happen because of hyposecretion of thyroid hormone in babies?

A

Infantile hypothyroidism

201
Q

Describe hypothyroidism

A
  • low metabolic rate
  • cold intolerant
  • growth is retarded
  • brain development is inhibited
  • caused by lack of iodine in the mother’s diet
202
Q

Give an example of what can happen because of hyposecretion of thyroid hormone in adults?

A

Iodine deficiency disorder (eg. simple goitre)

203
Q

Describe iodine deficiency disorder

A
  • the thyroid gland is unable to make enough thyroid hormone (TH)
  • this leads to TRH and TSH secretion increase to try and increase TH levels
  • overstimulation of thyroid gland
  • excess TSH stimulates growth of the thyroid gland
204
Q

Give an example of hypersecretion of the thyroid hormone caused by autoimmunity

A

Grave’s disease

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