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ENDO > Wk 2 > Flashcards

Wk 2 Flashcards

Hormones & Mechanism of Hormone Actions

1
Q

What is the Endocrine system?

A
  • It consists of endocrine glands and hormones
  • The system coordinates and integrates cellular activity for homeostasis
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2
Q

What does Endocrine refer to?

A
  • ductless
  • secrete hormones
  • secretions poured into blood
  • complex glands
  • pituitary, thyroid etc.
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3
Q

What does Exocrine refer to?

A
  • glands with a duct
  • chemicals like enzymes, mucus and other substances
  • secretions into the lumen and duct
  • simple glands
  • glands like liver, pancreas etc.
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4
Q

What are the functions of the Endocrine System?

A
  • Homeostasis
  • Cell growth and differentiation
  • Development
  • Reproduction
  • Control system
  • Regulation of metabolism
  • Blood pressure control
  • Sodium + potassium balance
  • Water balance
  • Response to stress
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5
Q

What are the primary and secondary Endocrine Glands?

A

Primary
- Pituitary
- Thyroid
- Parathyroid
- Adrenals

Secondary
- Heart
- Liver
- Stomach
- Intestine
- Kidney

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6
Q

What are hormones?

A
  • Synthesised in a gland
  • Secreted into the blood
  • Travel in blood
  • Hormone receptor in a target cell
  • Initiate cell response
  • Can be metabolised or catabolised (catabolic end product excreted in urine or bile)
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7
Q

What are the two types of hormone transport?

A

Free and Bound Form

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8
Q

What is Free Form hormone transport?

A
  • Dissolved in plasma
  • Unbounded form
  • Active hormone
  • Bind to receptor
  • Transported across the cell membrane
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9
Q

What is Bound Form hormone transport?

A
  • Bound to plasma proteins (Albumin, Globulin, Prealbumin)
  • Hormone reservoir in blood
  • Long half life
  • Cannot bind to receptors
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10
Q

What are the two types of hormone receptors?

A

Intracellular and Extracellular

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11
Q

What are Intracellular hormone receptors?

A

Cytoplasm, Nucleus
- Lipophilic
- Hydrophobic
- No second messengers
- E.g. steroid, thyroid hormones

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12
Q

What are Extracellular hormone receptors?

A

Plasma membrane receptors
- Lipophobic, Hydrophilic
- Have second messengers (G protein, Tyrosine kinase, Ion channel receptor)
- E.g. protein hormone, glycoprotein hormone, catecholamines

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13
Q

What are target cells?

A

Are able to detect changes in hormone signals.

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14
Q

What are the types of receptor regulation?

A
  • Up regulation
  • Down regulation
  • Permissiveness
  • Synergism
  • Antagonistic
  • Agonists
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15
Q

What is Up Regulation?

A

Decrease in hormone concentration and increase in number of active receptors.

Mechanism:
- New receptor synthesis
- Increase in receptor activity
- Decrease in receptor degradation

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16
Q

What is Down Regulation?

A

Increase in hormone concentration and decrease in the number of active receptors.

Mechanism:
- Decreased synthesis of receptors
- Inactivation of receptors

17
Q

What is Permissiveness Regulation?

A

A second hormone strengthens the effect of the first hormone (going to work to help your boss - both hormones have to be there).

E.g. Epinephrine –> Lipolysis Epinephrine + Thyroxine –>Lipolysis Increase

18
Q

What is Synergistic Effect?

A

Two hormones are acting together for a greater effect (teamwork).
Hormone A –> Response –
Hormone B –> Response –
Hormone C –> Response –
Hormone A + B + C –> Response!!!

E.g. Oxytocin + Prolactin + GH + Cortisol –> Milk Production!!!

19
Q

What is the Antagonistic Effect?

A

Two hormones having opposite effects.
E.g. Insulin –> Reduces blood sugar
Glucagon –> Increases blood sugar

PTH and Calcitonin –> Ca++ regulation

20
Q

What are the different types of hormones?

A

Proteins/Peptides/Glycoproteins
- From amino acids
- E.g. Insulin, GH, Prolactin

Steroids
- From cholesterol
- E.g. Cortisol, Aldosterone, Estrogen

Amine Type
- From modified amino acid tyrosine
- E.g. Epinephrine, Norepinephrine, Thyroid hormone

All originally produced from chemicals.

21
Q

What are protein hormones?

A
  • small peptides to large proteins
  • water soluble
  • lipophobic
  • membrane receptors
  • free form in blood (most proteins)
  • second messengers + tyrosine kinase
22
Q

What is the protein hormone synthesis pathway?

A
  1. Preprohormone (not active) - synthesis (Endoplasmic reticulum)
  2. Prohormone (not active) - packaging (golgi apparatus)
  3. Hormone (active) - storage (vesicles)
  4. Hormone (active) - secretion (exocytosis)

Preformed, stored in vesicles, ready to be released - hence rapid action.

23
Q

What are Amine hormones?

A
  • from tyrosine
  • modified amino acid
  • biosynthesis pathway
  • free and bound form
  • lipophilic (thyroid) and lipophobic (epi, nor epi)
  • membrane receptor (for catecholamine)
  • cytoplasm + nucleus receptor (T3, T4)
  • stored in vesicles (catecholamine)
  • E.g. Thyroxine, Triiodothyronine, Epinephrine, Nor-epinephrine, dopamine)
24
Q

What are steroid hormones?

A
  • from cholesterol
  • lipophilic (bound to plasma proteins)
  • intracellular receptors
  • NO second messengers
  • synthesised on demand, not stored in vesicles (slow response)
  • E.g. adrenal cortical hormones, gonadal steroids
25
Q

What is the steroid hormone synthesis pathway?

A
  1. Cholesterol
  2. Pregnenolone (ACTH)
  3. Progesterone
  4. Aldosterone, Cortisol, Adrenal Androgens, Estrogen
  • all steroid synthesis from cholesterol
  • end products of the pathway active hormones
  • progesterone (within the biosynthesis pathway)
  • enzyme deficiency (pathway shifts to produce other steroids)
  • E.g. 21-B hydroxylase deficiency –> decrease in production of sex steroids
26
Q

How is hormone secretion regulated?

A
  • Rhythms of hormone release
  • Not constant release by hormones
  • Oscillation throughout the day (one or multiple peaks of secretion)
27
Q

What are the types of hormone secretion regulation?

A

Diurnal Rhythm:
- Day/night cycle
- One peak within a day or night
- E.g. Cortisol, ACTH

Circadian Rhythm:
- 24h cycle
- Certain time of the day secretion peaks within 24 hrs
- E.g. GH, Melatonin

Monthly Rhythm:
- Hormone peak over a month
- E.g. LH, FSH

28
Q

What are the factors controlling hormone secretion?

A

Hormonal:
- Another hormone stimulating the excretion (hypothalamic hormone or pituitary)
- Pituitary hormones on peripheral glands

Humoral:
- Blood factors (blood sugar)
- Nutritional factors (sugar)
- Electrolytes (Na+, K+)
- Osmolarity of ECF

Neural:
- Nervous system stimulation of the neural gland
- Sympathetic nerve activity –> Adrenal medullary hormone excretion

29
Q

What is a negative feedback loop?

A

Inhibits the gland
- An increase in hormone release will decrease hormone secretion

30
Q

What is a positive feedback loop?

A

Activates secretion of hormone
- An increase in hormone release will increase hormone excretion

31
Q

What are the types of feedback loops?

A

Long loop feedback - from a pituitary target gland (e.g. thyroid, adrenal, gonads) on the hypothalamus.

Short loop feedback - pituitary gland acts directly back onto hypothalamus.

Ultrashort loop - hormone released by hypothalamus acting directly back onto hypothalamus (autocrine action)

32
Q

What are Endocrine Disorders?

A

Occur from states of too much or too little hormone.
- Normal
- Hyper (secreting too much)
- Hypo (decreased synthesis of hormone)

33
Q

Where do Endocrine Disorders occur?

A

Primary –> Gland
Secondary –> Pituitary
Tertiary –> Hypothalamus

34
Q

What is the Agonist Effect?

A

Works exactly like the hormone but is not the hormone. Has the same effect, binds to the same thing.

ENDO (10 decks)

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