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Physiology and Neuroscience > Physiological Aspects of the Endocrine System > Flashcards

Physiological Aspects of the Endocrine System Flashcards

1
Q

What is a hormone?

A

A chemical signal that enables an event in one part of the

body to have an effect elsewhere in the body.

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2
Q

What produces hormones?

A

May be produced from specialist organs – endocrine
glands – e.g. thyroid gland
May be produced from cells distributed around the body
– e.g. endothelial cells

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3
Q

How many hormones can an endocrine gland secrete?

A

Two or more different hormones
E.g. Thyroid Gland
T3 and T4- follicular cells
Calcitonin- parafollicular celks

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4
Q

What types of tissues secrete hormones

A

Nearly all tissues

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5
Q

Give an example of a hormone that is secreted at multiple sites

A

Somatostatin

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6
Q

What are the 3 types of chemical signalling?

A

Autocrine
Paracrine
Endocrine

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7
Q

What does exocrine mean?

A

Outside the body

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8
Q

What is endocrine signalling?

A

Within the body, directly into the blood stream, transported to target cells

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9
Q

What is autocrine signalling?

A

Signalling molecule that actually has an effect on itself

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10
Q

Give an example of autocrine signalling

A

E.g. T cells, produce growth signals which have effect on themselves

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11
Q

What is paracrine signalling?

A

Signalling molecules that have an effect on cels around them

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12
Q

Give and example of paracrine signalling

A

E.g. nerves

Synapses affect other synapses

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13
Q

Some cells can have multiple modes of signalling, give an example of this

A

Insulin
Has both endocrine and exocrine functions
Beta cells- produce insulin
Endocrine- has effect on multiple cells e.g. adipose, liver and skeletal muscle to enable uptake of glucose
Autocrine- when insulin is released it has some sort of subsequent release from its cells

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14
Q

What are target cells?

A

A particular hormone usually affects only a limited number of cells, these limited cells are target cells

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15
Q

Why is a cell a target?

A

Because it has a specific receptor for the hormone

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16
Q

What are the two types of hormone?

A

Proteins, peptides, amines

Steroids & Thyroid hormones

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17
Q

What is the structure of proteins peptides and amine hormones?

A

Hydrophilic (can’t cross membrane)
Cell surface receptors, act via second messenger system
Circulate primarily dissolved in plasma

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18
Q

What is the structure of steroids & thyroid hormones

A

Hydrophobic (Can easily pass across membrane)
Intracellular receptors, promote or suppress gene transcription
Circulate primarily bound to plasma proteins

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19
Q

What are the sizes of polypeptides and protein hormones?

A

Size 3AA to 200AA

20
Q

How are hormones initially assembled?

A

By pre pro ribosomes creating pro hormones

21
Q

Where do pro hormones then go?

A

Golgi aparatus where it is packaged and put into vesicles where it can be stored

22
Q

What happens to pro hormones in vesicles?

A

Can be cleaved to form active hormone

23
Q

What are the steps of hormone synthesis?

A

Synthesis
Packaging
Storage
Secretion

24
Q

What type of hormone is insulin?

A

Peptide hormone

25
Q

What are the steps of the synthesis of insulin?

A

Preproinsulin
Proinsulin
Insulin- released as hormone
C peptide also released

26
Q

How are steroid hormones synthesised?

A

Stimulus
Synthesis of precursor
Synthesis of enzyme
These two join and are released

27
Q

What two ways can steroid hormones be released?

A

Free binding proteins

Bound steroids

28
Q

Why can’t steroid hormones be stored in vesicles?

A

As they are lipid soluble and can easily cross membranes

29
Q

Why does it take longer for a steroid hormone to have effect?

A

It has to be synthesised first

30
Q

What are steroid hormones based on?

A

Cholestrol

Shape of ring and side chains vary

31
Q

What is the mechanism of action of peptide hormones?

A

Peptide hormone binds to a receptor on cell surface membrane
Once in the cell a inactive secondary messenger is activated which iniates a protein kinase cascade
The peptide hormone then enters the nucleus where it acts as a transcription factor which switches on gene for a specific protein

32
Q

What is the mechanism of action of steroids?

A

The steroid hormone enters the cytoplasm
Steroid hormone binds with steroid receptor to form a hormone-receptor complex
This then enters the nucleus
In the nucleus, the complex binds to receptor sites on chromatin activating mRNA transcription

33
Q

What factors determine blood concentration of hormones?

A

The Rate of Secretion

Rates of Inactivation and Excretion

34
Q

Whats are examples of the rate of secretion?

A

Neural control
Chemical control
Hormonal control
Feedback loops

35
Q

What are examples of rates of inactivation and excretion?

A

Peptide hormones – degraded in target tissues, have short
half-life in the blood (minutes to hours)
Steroid hormones – usually metabolised in the liver and
eliminated in the urine.
Longer half-life (hours to days)

36
Q

What is the Feedback in Endocrine Systems

A 
Stimulus – Fall in Blood
Calcium
Controlled condition –
Blood Calcium Level
Receptors – Calcium
receptor on parathyroid cell
membrane
Control Centre –
Parathyroid Gland
Effectors – Bones, Kidneys
Response – increased
calcium release from bones,
and increased calcium
re-uptake in kidneys
37
Q

What are multiple feedback loops?

A

More than one feedback loop

I.e. Long loop, short loop, ultra short loop

38
Q

What is a short loop?

A

Less sensitive than long loop

39
Q

What is an ultrashort loop?

A

E.g. hypothalamus feedbacks on itself

40
Q

How can cells change their sensitivity to a hormone?

A

By changing the number of receptors

41
Q

What is receptor down-regulation?

A

When a high extracellular concentration of the hormone is maintained for
some time, the total number of target cell receptors for that hormone may
decrease.

42
Q

What does receptor down-regulation reduce?

A

Target cell’s responsiveness

43
Q

What is an example of a receptor down-regulation?

A

Prolonged high concentration of insulin down regulates its receptors

44
Q

What is receptor up-regulation?

A

When cells are exposed for a prolonged period to very low concentrations
of a hormone, they may develop more receptors and have increased
sensitivity.

45
Q

What is an example of a receptor up-regulation?

A

Prolactin increases the number of its receptors in the breast for
breastfeeding.

46
Q

What is the clinical relevance of hormones?

A

Thyroid Disease- autoimmune disease
Iodine disease- hormone isn’t synthesised
Hypothalamic or Pituitary disease- e.g. tumour prevent production
Absent thyroid hormone receptor TRB- producing thyroid but cells can’t act

Physiology and Neuroscience (40 decks)

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