Endocrine Physiology_Dr Aricheta (1).pdf

Endocrine System Physiology

8/27/2014 1 Dr. Joseph Aricheta

Endocrine means:

endo-: within

-crino: to secrete

-logy: study of

Exocrine means:

exo-: outside

-crino: to secrete

-logy: study of

Endocrine gland vs. Exocrine gland


Exocrine gland: secretes its products outside of the gland through a duct.

Endocrine gland: secretes its products (usually Hormones) into the blood circulation or surrounding interstitial fluid towards its target organ (ductless).

Endocrine gland vs. Exocrine gland


Neurotransmitters released locally in response to nerve impulses.

Close to site of release, at a synapse; binds to receptors in postsynaptic membrane.

Mediator molecules

Site of mediator action

Hormones delivered to tissues throughout the body by the blood.

Far from site of release (usually); binds to receptors on or in target cells.

Nervous System Endocrine System Characteristics

Nervous System vs. Endocrine System


Muscle (smooth, cardiac, and skeletal) cells, gland cells, other neurons.

Typically within milliseconds (thousandths of a second).

Types of target cells

Time to onset of action

Cells throughout the body.

Seconds to hours or days.



Generally briefer (milliseconds).

Duration of action

Generally longer (seconds to days).



Functions of Hormones

1. Help regulate:

Chemical composition and volume of internal environment (interstitial fluid)

Metabolism and energy balance

Contraction of smooth and cardiac muscle fibers

Glandular secretions

Some immune system activities


Functions of Hormones

2. Control growth and development.

3. Regulate operation of reproductive

systems.

4. Help establish circadian rhythms.


Chemical Classes of Hormones

Lipid Soluble:

Steroid hormones (acts in the cytoplasm):

Aldosterone, cortisol, and androgens (Adrenal Cortex), Calcitriol (Kidney), Testosterone (Testes), Estrogens and progesterone (Ovaries).

Thyroid hormones (acts in the nucleus):

T3 (triiodothyronine) and T4 (thyroxine) in the thyroid gland



Lipid Soluble:

Gas:

Nitric oxide (NO) in the endothelial cells lining blood vessels



Water Soluble:

Amines:

Epinephrine and norepinephrine (catecholamines) in the Adrenal medulla.

Melatonin (Pineal gland),

Histamine (Mast cells in connective tissues),

Serotonin (Platelets in blood)



Water Soluble: Peptides and proteins (acts in the cell membrane): All hypothalamic releasing and inhibiting

hormones (Hypothalamus) Oxytocin, ADH (Posterior pituitary) Human growth hormone, thyroid-stimulating

hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, prolactin, melanocyte stimulating hormone (Anterior pituitary)


Chemical Classes of Hormones Water Soluble:

Peptides and proteins (acts in the cell membrane):

Insulin, glucagon, somatostatin, pancreatic polypeptide (Pancreas)

Parathyroid hormone (Parathyroid glands)

Calcitonin (Thyroid gland)

Gastrin, secretin, cholecystokinin, GIP

(glucose-dependent insulinotropic peptide) in the stomach and small intestine (enteroendocrine cells).


Chemical Classes of Hormones Water Soluble:

Peptides and proteins (acts in the cell membrane):

Erythropoietin (Kidneys)

Leptin (Adipose tissue)

Eicosanoids:

Prostaglandins, leukotrienes (all cells except red blood cells)


Summary of the Principal Actions of Anterior Pituitary Hormones

Human growth hormone (hGH) or somatotropin

Stimulates liver, muscle, cartilage, bone, and other tissues to synthesize and secrete insulin-like growth factors (IGFs);

IGFs promote growth of body cells, protein synthesis, tissue repair, lipolysis, and elevation of blood glucose concentration.



Thyroid-stimulating hormone (TSH) or thyrotropin

Stimulates the synthesis and secretion of thyroid hormones by the thyroid gland.

Follicle-stimulating hormone (FSH)

In females, initiates development of oocytes and induces ovarian secretion of estrogens.

In males, stimulates testes to produce testosterone.



Prolactin (PRL)

Together with other hormones, promotes milk secretion by the mammary glands.

Adrenocorticotropic hormone (ACTH) or corticotropin

Stimulates secretion of glucocorticoids (mainly cortisol) by the adrenal cortex.



Melanocyte-stimulating hormone (MSH)

Exact role in humans is unknown but may influence brain activity; when present in excess, can cause darkening of skin.


Summary of the Principal Actions of Posterior Pituitary Hormones

Oxytocin (OT):

Neurosecretory cells of hypothalamus secrete OT in response to uterine distention and stimulation of nipples.

Stimulates contraction of smooth muscle cells of the uterus during childbirth;

stimulates contraction of myoepithelial cells in the mammary glands to cause milk ejection.


Summary of the Principal Actions of Posterior Pituitary Hormones

Antidiuretic hormone (ADH) or vasopressin: Neurosecretory cells of hypothalamus secrete

ADH in response to elevated blood osmotic pressure, dehydration, loss of blood volume, pain, or stress; low blood osmotic blood pressure, high blood volume, and alcohol inhibit ADH secretion. Conserves body water by decreasing urine

volume; decreases water loss through perspiration; raises blood pressure by constricting arterioles.


Actions of Thyroid Hormones:

Increase basal metabolic rate

Regulate development and growth of nervous tissue and bones

Enhance some actions of catecholamines

Stimulate lipolysis


Actions of Thyroid Hormones:

Stimulate protein synthesis

Increase the use of glucose and fatty acids for ATP production

Increase body temperature (calorigenic effect)

Stimulate synthesis of Na+/K+ ATPase


Terima kasih!


Endocrine Physiology_Dr Aricheta (1).pdf

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