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Medsci 312 > Lecture One; How Hormones Work > Flashcards

Lecture One; How Hormones Work Flashcards

1
Q

Give a brief overview of the function and properties of the endocrine system;

A
  • Maintains homeostasis
  • Cell;Cell communication
  • Integrates with nervous system (neuroendocrinology) to maintain homeostasis
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2
Q

How does the nervous and endocrine system maintain homeostasis?

A

Nervous system: Responses are rapid short lived, triggered by change in environment

Endocrine system; Takes time, generates hormones to induce physiological changes of specific tissues. Can persist for a long time depending on the hormones

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3
Q

Define a hormone;

A

A chemical substrate released into circulation that acts a specific receptor and cell and creates the receptor induced response

“Classical endocrine signalling”

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4
Q

What is variation 1/3 for classical endocrine signalling?

A

Some neurons produce hormones that act in the classical endocrine signalling manner.

  • These are neurohormones and are a variation because they are not produced by classical endocrine tissue
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5
Q

What is variation 2/3 for classical endocrine signalling?

A

Paracrine signalling; Hormones that act on another endocrine cell / neighbouring cell (paracrine event)

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6
Q

What is variation 3/3 for classical endocrine signalling?

A

Autocrine signalling; Hormones synthesised and stimulates the same self (autocrine event)

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7
Q

What are the classes of receptors that hormones can act on;

A

Intracellular Receptors

Extracellular Receptors

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8
Q

What are the types of hormones?

A

Peptide hormones

Steroid/Lipid hormones

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9
Q

Describe protein hormones;

A

Hydrophilic, act on extracellular receptors because they are lipophobic and cannot diffuse through the plasma lipid membrane.

Use secondary messenger cascades

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10
Q

Write brief notes on steroid/lipid hormones;

A

Hydrophobic, carrier transporters allow movement in blood i.e albumin, SBHG then diffuse into the cell and act on intracellular receptors

Binding affinity of receptors must be greater than that of transporter.

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11
Q

How are hormone receptors classified?

A

Based on structure

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12
Q

List the hormone receptors;

A

7 transmembrane receptor (GPCR)
Single transmembrane spanning receptor
Dimer (single spanning receptor)

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13
Q

Describe the 7 transmembrane receptor.

A

7 transmembrane protein with EC N terminus that hormones bind to.

This results in a conformational change activating the G subunits, which is further propogated by PKC etc to have nuclear effects

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14
Q

Whats a common affect following receptor/GPCR activation?

A

Raised IC cAMP levels.

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15
Q

Describe single spanning receptor;

A

One transmembrane protein with IC intrinsic kinase activity

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16
Q

Discribe the dimer;

A
  • Two receptors i.e insulin that requires to molecules to be activated
  • Changes in conformation of IC tyrosine kinase domains, which then phosphorylate residues on itself (autophosphorylation)
17
Q

What do hormones typically do?

A

Once bound to receptors they alter gene expression, thus mRNA and proteins formed.

Regulate homeostasis!

18
Q

What are the three endocrine reflexes?

A

1) Humoral stimuli (changes in ECF, i.e BG, ions, Temp)
2) Hormonal Stimuli (Arrival or removal of specific hormones)
3) Neural stimuli (Neuroglandular junctions - neurotransmitter stimulates H. release)

19
Q

Once hormones achieve their purpose, what happens?

A

Endocrine reflexes must be turned off; Negative feedback

Direct or Indirect

20
Q

What is the first step in negative feedback loops?

A

The endocrine cell responds to a disturbance in homeostasis by releasing its hormone into the circulatory system.

21
Q

What is the second step in negative feedback?

A

The released hormone stimulates a target cell.

22
Q

What is the third step in negative feedback?

A

The target cell releases regulatory hormones that eliminate the release of more hormone and eliminates endocrine cell stimuli. Also restores homeostasis

23
Q

Give an example of negative feedback;

A

Glucose consumption

  • Raised BG
  • Beta cells in pancreas are stimulated and release Insulin
  • Blood glucose falls and stimulus for insulin is stopped from being produced (negative stimulus)
24
Q

Describe feedback loops

A

Direct (short)
Indirect (long)

Complex (long) negative feedback loops are most common in hormones and they can become severely complicated

25
Q

Give the example of the stress response as negative feedback;

A 
Hypothalamus
- CTRH
A. pituitary
- Corticotrophin
Adrenal Cortex
- Cortisol

Cortisol has negative feedback on AP (D) and Hyp (Ind)

Corticotrphin acts on Hyp (D) via negative feedback

26
Q

Does positive feedback play a role in hormones?

A

Oxytocin and Ovulation are examples of hormonal positive feedback

27
Q

What is positive feedback limited to?

A

Hormone regulation through positive feedback is restricted to processes that must be rushed to completion

28
Q

What is positive feedback?

A

The secretion of a hormone produces an affect that further stimulates hormone release.

29
Q

Give an example of positive feedback;

A 
Hyp.
- GnRH
A. Pituitary
- LH
Ovaries
- Estradiol

Estradiol acts on A.pituitary positively

30
Q

How is the brain critical in endocrine regulation?

A

Hyp. is key for homeostasis as it receives majority of sensory input and detects a lot

31
Q

How does the hypothalamus respond to changes in homeostasis?

A

Hypothalamus responds by regulation pituitary gland hormones and neural projections to endocrine glands

32
Q

What is the first hypothalamus action/regulation?

A

Neurons in the hypothalamus synthesise regulatory hormones which travel through the MEDIAN EMINANCE and act on the A.pituitary (Synthesises activating or inhibiting hormones)

33
Q

What is the second hypothalamus action/regulation?

A

Neurosecretory neurons synthesise store and secrete hormones. (ADH and Oxytocin(

34
Q

What is the third hypothalamus action/regulation?

A

Through nervous system (ANS), it can DIRECTLY regulate adrenal medulla release of corticotrophins

Direct Control

35
Q

What are the anterior hypothalamic nuclie?

A

Sup.

PVN
SCN
SON
PON

Inf.

36
Q

What are the posterior hypothalamic nuclie?

A

Sup.

DMN
VMN
AN

Inf.

Medsci 312 (28 decks)

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