the Peripheral Endocrine Glands

The peripheral endocrine glands

thyroid, parathyroid, adrenals, and pancreas

Thyroid gland

thyroud hormone increases the BMR and has a calorigenic effect “heat producing”. Also increases rate, force, and cardiac output of the heart, stimulates growth hormone secretion by increasing the production of IGF1 from the liver

Hypothyroidism

underactive thyroid, symptoms are fatigue, hoarseness, weight gain, muscle weakness, numbness in hands, brain fog, depression, and anxiety

hyperthyroidism

Overactive thyroid, Rapid heart rate, more frequent defecation, unexplained weight loss, felling anxious or nervous, shakiness, increased sweating

causes of hypothyroidism

primary failure of the gland itself, secondary to hypothalamic or anterior pituitary failure, or a lack of dietary iodine

causes of hyperthyroidism

abnormal presence of TS immunoglobulin, secondary to excess hypothalamic or anterior pituitary secretion, or. hypersecreting thyroid tumor

adrenal gland

each gland consists of a steroid secreting cortex and a catecholamine secreting medula

adrenal cortex

three layers, secretes hormones belonging to different chemical categories (cortison, aldosterone, and androgens)

adrenal medula

produces epinephrine

mineralocorticoids (aldosterone)

major effect is on Na and K balance and blood pressure homeostasis

function of aldosterone

promotes Na retention and enhances k elimination during the formation of urine (without aldosterone, a person rapidly dies of circulatory shock)

glucocorticoids (cortisol)

cortisol exerts metabolic effects and plays a key role in adaptation to stress

stress response

1. elevated blood pressure

2. suppresses immune function

3. mood alterations

4. increase protein metabolism

chronic effects of stress

1. high blood pressure

2. osteoporosis

3. diabetes

4. sleep disturbances

Epinephrine (adrenaline)

released from the adrenal medula reinforces and is stimualted by the fight or flight response of the sympathetic nervous sistem and exerts metabolic effects

metabolic effects of epinephrine

1. increases cardiac output, diabetes respiratory airways, prompt mobilization of stored carbs and fats so extra energy is available to fuels muscular work

2. promotes arousal, increases alertness, causes sweating

Integrated stress responce

generalized apttern of reaction to any situation that threatens homeostasis

Steps of integrated stress responce

1. sympathetic nervous system activation

2. epinephrine

3. Antidiurhettic hormone

4. Aldosterone

5. 
   

Anabolism

buildup of large organic macromolecules from small organic subunits

Catabolism

Breakdown of large, energy rich organic molecules within cells

interconversion amoung organic molecules

most small organic molecules can be converted into other cell types

How does the endocrine pancreas control fuel metabolism

Stores food due to intermittent nutrients

energy storage forms

excess circulating glucose, circulating fatty acids, and circulated amino acids

Metabolic fuels

metabolic fuels are stored during the absorptive state and mobilized during the post absorptive state

Absorptive “fed: state

occurs after a meal

postabsorptive “fasted” state

occurs between meals

Pancreas response to low blood glucose

releases glycogen which is converted to glucose in the liver

Pancreas response to high blood glucose level

Pancreas releases insulin which influences the liver to convert convert glucose to glycogen and also encourages glucose uptake by cells

Blood glucose control

the pancreas secretes insulin and glucagon to regulate fuel metabolism

Beta cells produce

insulin

alpha cells produce

glucagon

Fasted state Blood glucose regulation pathway

low blood glucose, glucagon release from pancreas, elevated blood glucose, prevents hyperglycemia, liver is primary target and ultimately glycogenolysis and gluconeogenesis are stimulated

Fed state blood glucose regualtion pathway

elevated blood glucose, insulin release from the beta cells of the pancreas, increased glucose transport into muscle and adipose tissue and enhances the utilization of stored glucose, low blood glucose

factors that increase blood glucose

glucose absorption from digestive tract,

factors that decrease blood glucose

urinary ezcretion of glucose

Glucose transport to adipose and skeletal muscle in fasted state

there are no GLUT 4 transporters in the membrane

Glucose transport to adipose and skeletal muscle in the fed state

1. Insulin binds to its receptor on the cell membrane

2. Signal transduction cascade reaches the secretory vesicle

3. Secretory vesicle containing the GLUT4 transport protein fuses to the membrane and completes exocytosis

4. GLUT 4 transport proteins are now a part of the cell membrane and allow the entrance of glucose into the cell

Glucose transport to the liver in the fasted state

In the fasted state, the hepatocyte makes glucose (gluconeogenesis) and transports it out into the blood along its concentration gradient using GLUT2 receptors along(this is in the presence of LOW INSULIN)

Glucose transport to the liver in the fed state

In the fed state, the glucose concentration gradient reverses and glucose enters the hepatocyte via GLUT2 receptors. Glucose concentration inside the cell is maintained low by a signal cascade signaled by insulin binding to its receptor and causing a signal cascade by removing a phosphate off of each glucose molecule

parathyroid glands and control of calcium metabolism

• regulation of Ca2+ metabolism depends on hormonal control of exchanges between the ECF and the bone, kidneys, and intestine

effect of parathyroid hormone on calcium levels

1. Parathyroid hormone released (PTH)

2. Reduces calcium clearance and causes vitamin D activation

3. enhances the absorption of calcium in the intestines by activating vitamin D

4. stimulates osteoclast activity (breaks down bone and releases calcium into the blood)

effect of thyroid on Calcium levels

TSH→ Release of Calcitonin

1. Inhibits the reabsorption of calcium and phosphate in the kidneys

2. limits the absorption of calcium in the intestines

3. Inhibits osteoclast activity in the bone