Types of Cellular Secretion of HormonesTypes of Cellular Secretion of HormonesBlood Transport of Hormones Blood Transport of Hormones

General Mechanisms of Hormonal ActionsGeneral Mechanisms of Hormonal Actions

Asha AlexAsha AlexPhysiologyPhysiology

What is a HORMONE?What is a HORMONE? HormoneHormone= =

chemical messenger produced in the bodychemical messenger produced in the body

that interacts w/ receptor in target tissuethat interacts w/ receptor in target tissue

to cause a change in function of that tissue. to cause a change in function of that tissue.

Types of Cellular SecretionTypes of Cellular Secretion1.1. AutocrineAutocrine2.2. ParacrineParacrine3.3. EndocrineEndocrine4.4. NeuroendocrineNeuroendocrine5.5. NeuralNeural6.6. PheromonalPheromonal

Autocrine & Paracrine: Autocrine & Paracrine: The Local TargetersThe Local Targeters

Endocrine & Neuroendocrine: Endocrine & Neuroendocrine: The Long Distance TravelersThe Long Distance Travelers

Types of Cellular Secretion of HormonesTypes of Cellular Secretion of HormonesTypes of Types of

HormonesHormonesAction of HormoneAction of Hormone ExampleExample

AutocrineAutocrine Acts on cells that synthesized them Acts on cells that synthesized them Insulin-like Growth Factor (IGF-1)-Insulin-like Growth Factor (IGF-1)-stimulates cell division in the cell stimulates cell division in the cell which produced it. which produced it.

ParacrineParacrine Acts on nearby cellsActs on nearby cells Insulin, secreted by pancreatic Insulin, secreted by pancreatic ββcells-affects secretion of cells-affects secretion of glucagon by pancreatic glucagon by pancreatic αα cells cells

EndocrineEndocrine Carried in bloodstream or thru lymph Carried in bloodstream or thru lymph to target cells in organsto target cells in organs

Insulin, Estradiol, CortisolInsulin, Estradiol, Cortisol

NeuroendocrineNeuroendocrine Hormones synthesized in neuron: Hormones synthesized in neuron: a) releases hormone next to a) releases hormone next to target cell OR target cell OR b) releases it into bloodstream, b) releases it into bloodstream, which carries it to target cell. which carries it to target cell.

Hormone synthesized in neuron, Hormone synthesized in neuron, goes from hypothalamus to goes from hypothalamus to anterior pituitary gland thru the anterior pituitary gland thru the portal system portal system

NeuralNeural Chemical released by 1 neuron, & Chemical released by 1 neuron, & acts on adjacent neuron.acts on adjacent neuron.

Neurotransmitters: AcetylcholineNeurotransmitters: Acetylcholine

PheromonalPheromonal Release of volatile hormones (into Release of volatile hormones (into atmosphere; are transmitted to atmosphere; are transmitted to another individual & recognized as another individual & recognized as olfactory signal. olfactory signal.

PheromonesPheromones

Regulation of Hormone Secretion: Regulation of Hormone Secretion: NEGATIVE FEEDBACKNEGATIVE FEEDBACK

If hormone A acts to raise If hormone A acts to raise the plasma concentration the plasma concentration of substrate B, a of substrate B, a decrease in substrate B decrease in substrate B will stimulate the will stimulate the secretion of hormone A.secretion of hormone A.Whereas an increase in Whereas an increase in substrate B will suppress substrate B will suppress secretion of hormone A.secretion of hormone A.Maintains homeostasis. Maintains homeostasis.

Blood Transport of HormonesBlood Transport of Hormones

When hormones are When hormones are secreted into blood, many secreted into blood, many are immediately bound to are immediately bound to plasma proteins.plasma proteins.Proteins can recognize Proteins can recognize hormone specifically & hormone specifically & bind it w/high affinity bind it w/high affinity (ex: binding of sex (ex: binding of sex hormones by sex hormones by sex hormone binding globulin- hormone binding globulin- SHBG).SHBG).

Blood Transport of HormonesBlood Transport of Hormones

Equilibrium btw free & bound hormoneEquilibrium btw free & bound hormone– a fixed proportion of hormone travels free/unbound, a fixed proportion of hormone travels free/unbound,

while most is carried bound.while most is carried bound.

Bound hormone isBound hormone is– physiologically inactivephysiologically inactive– protected from metabolic enzymes in organs (liver) protected from metabolic enzymes in organs (liver)

Drugs, (aspirin) can displace other substances Drugs, (aspirin) can displace other substances like anticoagulants from their binding siteslike anticoagulants from their binding sites– may cause hemorrhage. may cause hemorrhage.

General Mechanisms of Hormonal ActionGeneral Mechanisms of Hormonal Action

Hormones interact w/target cells thru primary interaction Hormones interact w/target cells thru primary interaction w/receptors that recognize the hormones.w/receptors that recognize the hormones.Several receptor systems: differ in mechanism & timing.Several receptor systems: differ in mechanism & timing.

1) Membrane Receptors1) Membrane Receptors2) Intracellular Receptors 2) Intracellular Receptors

bind to receptors on cell membrane

conformational change in other membrane

proteins

activates enzymes in cell

Synthesis of second messengersthat activate

phosphorylating enzymes

Charged ions (peptides, Charged ions (peptides, neurotransmittersneurotransmitters))

MEMBRANE RECEPTORSMEMBRANE RECEPTORS

INTRACELLULAR RECEPTORSINTRACELLULAR RECEPTORS

Uncharged molecules Uncharged molecules (steroid hormones)(steroid hormones)

diffuse into cell &bind to intracellular receptors

hormone-receptor complexbinds to specific

hormone response elements (HREs) on DNA

Modulates gene expression in target cell.

RNA & protein synthesis altered.

TO WRAP IT UP:TO WRAP IT UP:

Types of Cell SecretionTypes of Cell Secretion1.1. AutocrineAutocrine2.2. ParacrineParacrine3.3. EndocrineEndocrine4.4. NeuroendocrineNeuroendocrine5.5. NeuralNeural6.6. PheromonalPheromonal

Blood TransportBlood Transport– binding of hormone to plasma protein binding of hormone to plasma protein

Membrane Receptors Membrane Receptors Intracellular ReceptorsIntracellular Receptors

BibliographyBibliography

Endocrinology-At A GlanceEndocrinology-At A GlanceMedical Physiology-GuytonMedical Physiology-Guyton