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SEM 1 BCS > The Endocrine System > Flashcards

The Endocrine System Flashcards

1
Q

Draw a diagram to explain thermoregulation

A
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2
Q

What are the benefits of an increase in body temp?

A

Pyrogens change the set point to a higher level resulting in fever. This:
– Inhibits bacterial growth
– Speeds up metabolic reactions
– Increases delivery of wbcs to infection sites

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3
Q

Draw a diagram to show the homeostatic control of blood pressure

A

To increase BP, HR increases and vasoconstriction occurs
To decrease BP, HR decreases and vasodilation occurs.
In hypertension, the sensitivity of the baroreceptors are reset

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4
Q

Draw a diagram to show cortisol concentration control

A

Cortisol wakes us up in the morning and its levels decrease at night- so its controlled by circadian rhythm (body clock)
Stress also alters the set point to produce more cortisol

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5
Q

How is uterine contractions during Labour an example of positive feedback?

A

In labour oxytocin is released from posterior pituitary network

stimulates contraction of uterine muscles

Cervix dilates and activate stretch receptors

Action potentials signal to hypothalamus. This stimulates further release of oxytocin

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6
Q

Give the major endocrine glands and their secretions

A

HYPOTHALAMUS: Releasing & inhibiting hormones​
PITUITARY GLAND: works w hypothalamus in concert ​
Anterior lobe: trophic hormones
Posterior lobe:oxytocin & vasopressin (ADH)​
THYROID GLAND: Thyroxine, tri-iodothyronine​
PARATHYROID GLAND - Parathyroid hormone
ADRENAL GLAND
Cortex: Cortisol, aldosterone ​
Medulla: Adrenaline/noradrenaline​
GONADS - Oestrogens, androgens, progestagens​
​PANCREAS - Insulin, glucagon ​​

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7
Q

Describe the types of signalling mechanisms in the endocrine system

A
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8
Q

Define four major classes of hormone

A 
peptide hormones- eg pituitary and hypothalamic hormones. Fast acting- half life is in mins. Does not need to bind to plasma proteins unlike the other hormone types
Steroid hormones (derived from cholesterol) eg cortisol 
aa derivatives (tyrosine/tryptophan) eg Adrenaline, NA
Fatty acid derivatives- eg prostaglandins
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9
Q

What are neurosecretory cells?

A

Neurosecretory cells: nerve cells that produce and secrete hormones eg:
Magnocellular neurones in the hypothalamus synthesise and release posterior pituitary hormones​
Other neurosecretory cells in the hypothalamus inc parvicellular hormones

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10
Q

Draw a diagram to explain Glands controlled by the hypothalmic-pituitary axis ​

A

TSH, ACTH, LH, FSH are all peptide hormones. Peptide hormones will signal to other endocrine glands and endocrine cells which produce steroid hormones​

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11
Q

Disorders of the endocrine system arise due to…

A

Excess or deficiency​
Impaired synthesis​
Transport and metabolism of hormones​
Resistance to hormone action- eg malfunctioning receptor

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12
Q

How are peptide and protein hormones formed?

A

Peptides and proteins are water soluble, made from large precursor molecules (prohormones)
Transcription of DNA to RNA​
Post-transcriptional processing: RNA forms mature RNA. Hay changes to 3’ and 5’ ends, excision of introns​
Translation of mRNA into protein
Post-translational processing: cleavage of large pre-prohormone, protein folding, glycosylation

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13
Q

Synthesis of large precursor proteins forms active hormone. What is the difference between a pre prohormone and a prohormone?

A

Synthesis of large precursor proteins forms active hormone

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14
Q

How are steroid hormones synthesised from cholesterol?

A

Cholesterol bound to sterol carrier protein is transported to mitochondria​. StAR protein transports cholesterol to inner mitochondrial membrane
Cholesterol forms pregnenolone by side chain cleavage enzyme, P450scc
Between mitochondria and sER steroids synthesised by hydroxylase enzymes

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15
Q

Draw a diagram to demonstrate simplified steroid synthesis

A
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16
Q

Describe and explain the synthesis of thyroid hormones

A
  1. Active uptake of iodide into follicular cell​​
  2. Oxidation of iodide to iodinating intermediate by thyroid peroxidase which is activated by H2O2​
  3. Iodination of tyrosine residues of thyroglobulin and apical-colloid interface​
  4. Storage of T3 and T4 in colloid in the follicular cell
  5. Uptake of thyroglobulin droplets into follicle cell​
  6. Release and secretion of T3 and T4 stimulated by TSH
17
Q

Describe the hormone action of peptide hormones

A

Peptide and protein hormones​

Water soluble so act on cell surface receptors​
Activate second messengers and/or enzymes​
Cytoplasmic and nuclear effects
Signalling pathways for receptors with tyrosine kinase activity= Raf/MEK ERK pathway​. PI3-Kinase/Akt pathway. JAK STAT pathway

18
Q

Describe the hormone action of steroid hormones

A

Steroid and thyroid hormones​

Lipophilic so act on intracellular receptors in cytoplasm ​
or nucleus. Receptors are transcription factors

19
Q

Describe steroid and thyroid hormone receptors

A

Steroid and thyroid hormones cross cell membranes and act on intracellular receptors​
Steroid hormone receptors= family of transcription factors​
Different functional regions of the receptor are defined as domains - A-F​
C domain=DNA binding region and is highly conserved​
Both the A/B domains and E/F domains have transcriptional activity (AF-1/AF-2)​

20
Q

What is the C domain?

A
21
Q

How else can hormones affect transcription?

A

Hormone crosses cell membrane​
Heat shock protein dissociates from receptor​
Hormone binds to receptor and dimerization occurs​
Dimerized receptors translocate to the nucleus​ and to the hormone response element on the DNA​
Along with other transcription factors transcription is initiated​
Some receptors located within the nucleus, not the cytoplasm

22
Q

Describe a disorder of protein signalling that is can be associated with obesity

A

Type 1 diabetes – autoimmune destruction of the pancreatic islets: absolute insulin deficiency​

Type 2 – saturation of insulin receptors, insulin resistance, partial loss of insulin production (insulinopaenia) – often associated with obesity​

23
Q

What is metabolic syndrome?

A

A clustering of metabolic abnormalities –central obesity, dyslipidaemia (changes to both the HDL and LDL low density lipoprotein), insulin resistance and hypertension

24
Q

What is testotoxicosis?

A

Activating mutation of the LH receptor – also a G-protein coupled receptor​. If you have an activating mutation, you’ll have continuous activation even in the absence of a ligand

Testotoxicosis​: High levels of testosterone stimulate penile growth and growth of pubic hair​

25
Q

Give another disorder of peptide receptor signalling

A
26
Q

Describe disorders of steroid hormone signalling

A

Abnormalities in steroid synthesis​. Can cause:
Aromatase deficiency in men​- can’t synthesise oestrogens from androgens, no epiphyseal closure, long stature

In women: Virilisation of XX fetuses​. Clitoromegaly- increased clitoral size​. Ambiguous genitalia

Girls develop male-type characteristics and boys show early sexual development due to excess androgens

27
Q

Describe Disorders of steroid receptor signalling

A

Resistance to hormone action: when you cannot respond to steroid hormones ​
Inactivating mutations of steroid receptors e.g. Androgen receptor (nuclear receptor)​
Androgen insensitivity syndrome (AIS): when a XY genotype is resistant to male hormones (androgens). They thus have physical traits of a woman

28
Q

Describe disorders of thyroid hormone signalling

A

Goitre – enlargement of thyroid gland, caused by hyper/hypothyroidism.

Lack of iodine in the diet leads to deficiency in T3 and T4 (hypothyroidism)
​
Graves’ Disease/hyperthyroidism:
Autoantibodies to the TSH receptor act on the thyroid gland, stimulating excess thyroid hormones. Can cause eye disease
OR activating mutation of the TSH G-protein coupled receptor

SEM 1 BCS (27 decks)

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