Wk 2 Flashcards
Hormones & Mechanism of Hormone Actions (34 cards)
What is the Endocrine system?
- It consists of endocrine glands and hormones
- The system coordinates and integrates cellular activity for homeostasis
What does Endocrine refer to?
- ductless
- secrete hormones
- secretions poured into blood
- complex glands
- pituitary, thyroid etc.
What does Exocrine refer to?
- glands with a duct
- chemicals like enzymes, mucus and other substances
- secretions into the lumen and duct
- simple glands
- glands like liver, pancreas etc.
What are the functions of the Endocrine System?
- Homeostasis
- Cell growth and differentiation
- Development
- Reproduction
- Control system
- Regulation of metabolism
- Blood pressure control
- Sodium + potassium balance
- Water balance
- Response to stress
What are the primary and secondary Endocrine Glands?
Primary
- Pituitary
- Thyroid
- Parathyroid
- Adrenals
Secondary
- Heart
- Liver
- Stomach
- Intestine
- Kidney
What are hormones?
- 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)
What are the two types of hormone transport?
Free and Bound Form
What is Free Form hormone transport?
- Dissolved in plasma
- Unbounded form
- Active hormone
- Bind to receptor
- Transported across the cell membrane
What is Bound Form hormone transport?
- Bound to plasma proteins (Albumin, Globulin, Prealbumin)
- Hormone reservoir in blood
- Long half life
- Cannot bind to receptors
What are the two types of hormone receptors?
Intracellular and Extracellular
What are Intracellular hormone receptors?
Cytoplasm, Nucleus
- Lipophilic
- Hydrophobic
- No second messengers
- E.g. steroid, thyroid hormones
What are Extracellular hormone receptors?
Plasma membrane receptors
- Lipophobic, Hydrophilic
- Have second messengers (G protein, Tyrosine kinase, Ion channel receptor)
- E.g. protein hormone, glycoprotein hormone, catecholamines
What are target cells?
Are able to detect changes in hormone signals.
What are the types of receptor regulation?
- Up regulation
- Down regulation
- Permissiveness
- Synergism
- Antagonistic
- Agonists
What is Up Regulation?
Decrease in hormone concentration and increase in number of active receptors.
Mechanism:
- New receptor synthesis
- Increase in receptor activity
- Decrease in receptor degradation
What is Down Regulation?
Increase in hormone concentration and decrease in the number of active receptors.
Mechanism:
- Decreased synthesis of receptors
- Inactivation of receptors
What is Permissiveness Regulation?
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
What is Synergistic Effect?
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!!!
What is the Antagonistic Effect?
Two hormones having opposite effects.
E.g. Insulin –> Reduces blood sugar
Glucagon –> Increases blood sugar
PTH and Calcitonin –> Ca++ regulation
What are the different types of hormones?
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.
What are protein hormones?
- small peptides to large proteins
- water soluble
- lipophobic
- membrane receptors
- free form in blood (most proteins)
- second messengers + tyrosine kinase
What is the protein hormone synthesis pathway?
- Preprohormone (not active) - synthesis (Endoplasmic reticulum)
- Prohormone (not active) - packaging (golgi apparatus)
- Hormone (active) - storage (vesicles)
- Hormone (active) - secretion (exocytosis)
Preformed, stored in vesicles, ready to be released - hence rapid action.
What are Amine hormones?
- 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)
What are steroid hormones?
- 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
