Endocrine System Pathways

cAMP pathway

Step 1: Hormone binds to receptor protein on the plasma membrane

Step 2: Receptor protein activates G protein by replacing GDP with GTP

Step 3: G protein binds to adenylate cyclase

G protein is now inactive and adenylate cyclase turns ATP to cyclic AMP that causes a reaction

Phosphodiesterase is an enzyme that turns off cyclic AMP

Caffeine binds to Phosphodiesterase which is why it seems like we have more energy.

PIP2 pathway

Step 1: Hormone binds to the receptor protein

Step 2: Receptor protein activates G protein

Step 3: G protein binds to effector protein Phospholipase

Step 4: Phospholipase causes PIP2 to spilt into DAG and IP3

Step 5: DAG stays in the membrane and acts as a second messenger, IP3 travels through the cytoplasm to the ER to bind to its calcium ion channels to release Calcium ions

Step 6: Cation bind to protein Calmodulin that acts as the response

Vascular System of Hypophysis

Direct gene activation

Step 1: Steroid hormone diffuses through the membrane and binds to a intracellular receptor.

Step 2: The receptor-hormone complex enters the nucleus

Step 3: The complex binds to a specific region of the DNA

Step 4: Binding initiates for the transcription of the gene into a mRNA strand

Step 5: The mRNA strand direct the synthesis of a new protein by binding to a ribosome that translates the mRNA into a protein

Hypothalamus to the Anterior Pituitary

Step 1: Hypothalamic neurons secrete their Hormones into the primary capillary plexus

Hypothalamus to the Posterior Pituitary

Step 2: Hypothalamic hormones travel through portal veins to the anterior pituitary to give out intructions

Step 3: In response to releasing hormones the anterior pituitary secretes hormones into the secondary capillary plexus that empties into bloodstream

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Step 1:Hypothalamus makes oxytocin or ADH

Step 2: Oxytocin and ADH are transported down the hypothalamus-Hypophysis tract to be delivered to the Posterior Pituitary

Step 3: Oxytocin and ADH are stored in the axon terminals of the posterior pituitary

Step 4: When hypothalamus neurons fire an action potential at the axon terminals of the pituitary release oxytocin and ADH

Aldosterone Secretion mechanisms

Renin-angiotensin-aldosterone mechanism

decrease in blood volume/pressure

Kidneys release renin

Angiotensin levels are increased

Plasma concentration of K+

Increase in K+ levels in blood

Atrial natriuetic peptide (ANP)

Increase of blood volume/pressure

Adrenocorticotropic Hormone (ACTH)

Stressors

direct stimulating effect

Triggers hypothalamus to release Cortico releasing hormone (CRH)

Release of ACTH

leads to heart releasing

ANP

Increase in Aldosterone release from the adrenal cortex

Target kidney tubules

Increases absorption of Na+ and water, and increases K+ excretion

leads to increase in blood volume/pressure

Regulation of Aldosterone Secretion Pathway

  1. Dehydration, Na+ deficiency, or hemorrhage
  1. Decrease in blood volume
  1. Decrease in blood pressure
  1. Juxtaglomerular cells of kidney releases renin
  1. Increased levels of renin
  1. Liver releases angiotensinogen
  1. angiotensin 1 increases
  1. Lungs produce and release angiotensin converting enzyme (ACE)
  1. Increased angiotensin 2
  1. The zona glomerosa of the adrenal cortex releases aldosterone
  1. increased aldosterone
  1. In kidneys sodium and water reabsorption increased and k+ secretion into the urine
  1. Increase in blood volume
  1. Increase in blood pressure
  1. Vasocontriction of blood pressure
  1. Increased K+ in extracellular fluid

Consqu. of Diabetes Mellitus

All tissues

decrease in glucose uptake

Liver breaks down glycogen to glucose

Rise in blood glucose levels (hyperglycemia)

Skeletal muscles break down protein

Liver converts amino acids to glucose

Adipocytes break down fats (lipolysis)

liver converts fats to ketone bodies

decrease in blood pH due to ketone bodies (ketoacidosis)

Ketones in urine ( Ketonuria) pulls cations into kidney tubules

Heart rhythm abnormalities, nausea, vomiting, abdominal pain, CNS depression, coma

Ketoacidosis symptoms are acetone breath and increase in heart rate, and depth of breathing

glucose in urine (glycosuria) glucose pulls water into kidney tubules

Osmotic diuresis

polyuria

dehydration

polydipsia