Hormonal regulation

24 important questions on Hormonal regulation

What is the difference in site of mediator action between the endocrine and nervous system?

Endocrine system: far from site of release
Nervous system: close to site of release (synapses)

What is the difference in types of target cells between the endocrine and nervous system?

Endocrine system: virtually all cells in the body
Nervous system: muscle cells, glands, other neurons

What is the difference in time of onset between the endocrine and nervous system?

Endocrine system: seconds, hours or days
Nervous system: typically within milliseconds
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What are water soluble hormones?

  • Amines (modified AA)
  • Peptides
  • Eicosanoids (derived from arachadonic acid)

What are lipid soluble hormones?

  • Steroids (derived from cholesterol)
  • Thyroid hormones (iodine added to tyrosine)

How are lipid soluble hormones transported?

These hormones must attach to transport proteins that are synthesised by the liver.

What is the advantage of being bound to a transport protein?

  • Transport is improved by making the hormones water soluble
  • Loss of the hormone by filtration of the kidney is prevented

What is the difference in receptors for lipid soluble and water soluble hormones?

Lipid soluble:
  1. hormones diffuse into the cell
  2. in the nucleus the activated receptor-hormone complex alters gene expression
  3. this newly formed mRNA directs synthesis of specific proteins on ribosomes.
Water soluble:
  1. the hormone binds to its receptor and activate G proteins, which activate adenylate cyclase
  2. activated adenylate cyclase converts ATP to cAMP
  3. cAMP serves as a second messenger to activate protein kinases
  4. activated protein kinases phosphorylate other enzymes
  5. millions of phosphorylated enzymes catalyse reactions that produce physiological responses
  6. phosphodiesterase inactivates cAMP

What are steroid receptors?

Hormone-bound steroid receptors are transcription factors that regulate gene expression in a DNA sequence-specific manner.

What are four different hormonal interactions?

  • Permissive effect
  • Synergistic effect
  • Antagonistic effect
  • Integrative effects

What is the permissive effect of hormones, can you give an example?

One hormone is needed for a second hormone to produce its effect.
Example: Thyroid hormone is required in order for epinephrine to affect energy consumption.

What is the synergistic effect of hormones, can you give an example?

Two hormones produce an effect that is greater than the combined effects of each individual hormone.
Example: Estrogen and LH are both required for oocyte production.

What is the antagonistic effect of hormones, can you give an example?

Two hormones have opposite effect.
Example: insulin promotes glycogen synthesis and glucagon stimulates glycogen breakdown.

What is the integrative effect of hormones?

Multiple hormones act together to produce complex cell type  and tissue specific effects.

What are the two feedback mechanisms? Can you explain them?

Autocrine and target cell feedback. Autocrine is within the cell, target cell feedback is feedback from the target cell. This can be a short or a long loop (target cell feedback).

How are hormones released from the posterior pituitary?

Neuroendocrine cells from the hypothalamus flow into the bloodstream in the posterior pituitary (bottom).

How are hormones released from the anterior pituitary?

Blood vessels in top of the anterior pituitary take up hormones, these hormones stimulate other hormones in anterior pituitary that will also go into blood stream to activate third hormone.

What is the function of vasopressin? What about oxytocin?

Vasopressin: regulate blood pressure and salt balance
Oxytocin: regulate reproductive activities

What are circumventricular organs?

Brain structures that lie outside the blood-brain barrier that can easily detect changes in the blood.

What affects vasopressin release?

  • Plasma osmolarity (high plasma osmolarity --> release of vasopressin)
  • Blood pressure (low blood pressure --> release of vasopressin)

What are the two different types of diabetes insipidus?

Central (primary) DI: inability of magnocellular neurons to release AVP
  • Genetic defect of vasopressin gene
  • Destruction of magnocellular neurons by tumors


Peripheral (secondary/nephrogenic) DI: inability of collecting dust cells to respond to AVP
  • Genetic defect of the vasopressin V2 receptor gene
  • Inability to synthesize or insert sufficient amounts of aquaporin channels

What are the four types of pancreatic islet cells? What do they secrete?

Alpha cells: secrete glucagon
Beta cells: secrete insulin
Delta cells: secrete growth hormone - inhibiting hormone (GH-IH) 
F cells: secrete pancreatic polypeptide (PP)

What is diabetes mellitus?

Glucose accumulates in the blood and is secreted by the kidneys, not taken up by tissues so they start to break down lipids and proteins.

What is the difference between type 1 and type 2 DM?

Type 1: inadequate insulin production by pancreatic beta cells
  • Insulin treatment
Type 2: normal insulin production but tissues do not respond to insulin
  • FA reduce insulin sensitivity
  • Associated with obesity and age
  • Treated by diet (weight loss) and exercise 

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