1.5 Endocrine Flashcards
What happens when cells don’t get enough glucose?
They die
What happens when cells get too much glucose?
Tissue glycosylation, globs onto proteins, lose tissue elasticity (critical in blood vessels)
What 3 things are most involved in glucose homeostasis?
Liver, muscle and fat
How is the liver involved in glucose homeostasis?
Glucose is stored as glycogen, de novo synthesis and release to bloodstream
How is muscle involved in glucose homeostasis?
Glucose uptake, storage (glycogen), breakdown
How is fat involved in glucose homeostasis?
Glucose uptake, converto to triglyceride and storage
Two functions of the pancreas
1) Exocrine function for digestion
2) Endocrine function for glucose regulation
Alpha islet cells secrete….
Glucagon
Beta-islet cells secrete…
Insulin
Both insulin and glucagon are______ with ______
Soluble peptide hormones
~50 amino acids
Do the alpha and beta cells use the brain to regulate glucose?
NO
In glucose regulation, what are the sensors / integrators?
Alpha & Beta cells
In glucose regulation, what are the effectors?
Liver, muscle and fat cells
In glucose regulation, what is the physiological parameter?
Blood [Glucose]
When you are hungry with low blood glucose, what hormones are secreted and suppressed?
Glucagon up, insulin down
What happens in the liver when glucagon is secreted?
- Glycogen breakdown
- ->glucose (glycogenolysis)
- GLUCONEOGENESIS: new glucose made from amino acids, lactate or glycerol (De novo synthesis of sugar)
What happens in the skeletal muscle when glucagon is secreted?
Glycogen breakdown–> Glucose (used by muscle)
What happens in fat when glucagon is secreted?
Triglycerides–> glycerol & fatty acids–> released into blood (spares glucose for brain)
LIPOLYSIS
Using non-glucose molecules for energy releases…
Acidic ketone bodies, which is why diabetics become acidotic and ketotic
When you just ate, what hormones are secreted / suppressed?
Insulin up, glucagon down
What happens in the liver when insulin is released?
Glucose uptake –> converted to glycogen (GLYCOGENISIS)
What happens in the skeletal muscle when insulin is secreted?
Glucose uptake—> Glycogen
What happens in fat when insulin is secreted?
FA uptake –> Converted to triglycerides (LIPOGENISIS)
Which cells have insulin receptors?
ALL CELLS
Glucose is very (polar / non polar)
Polar
What is the carrier protein called that allows glucose to get into the cell?
GLUT protein
Type I Diabetes
Pancreatic beta cells destroyed by auto immune disease–> insufficient insulin
*No glucose uptake–> hyperglycemia (elevated blood glucose)
Type II Diabetes
“Insulin sensitivity”
Defect in in insulin receptor signal transduction
Need a very high insulin to elicit normal GLUT expression
What appears to be the culprit of type II diabetes?
Cellular accumulation of fat
Cortisol
AKA glucocorticoids
Lipid soluble, steroid hormone derived from cholesterol molecule
Target tissues of cortisol
Muscle, adipose, liver, brain
IMMUNE CELLS, excess cortisol is toxic to these cells
Primary function of cortisol
Glucose & protein metabolism under long term stress.. keeps ample energy available to body’s tissues
(protein breakdown, glucose formation, lipolysis)
3 Regulators of cortisol
- CRH from the hypothalamic neurons
- ACTH from corticotropes
- Cortisol from adrenal cortex (outer layer of adrenal gland)
Feedback control of cortisol regulation
Negative, by cortisol, every step of the above pathway
Excess cortisol in body
Adrenal gland produces excess cortisol
Protein is catabolized
Massive edema due to fluid retention
Addison’s Disease
Insufficient cortisol
Low blood sugar
Low blood volume
JFK
GH
AKA Somatotropin
Soluble, peptide hormone
Target tissues of GH
Adipose, muscle cartilage and bone
GH promotes cell growth via
- Cell enlargement
- Mitosis
Second function of GH
And what does it favor
Regulates nutrient (protein, fat, glucose) metabolism in target tissue Favors muscle anabolism and adipose catabolism
GH stimulates what production from the liver?
Insulin-like growth factor
IGF-1 is a potent hormone / growth factor in target tissues (same as GH)
Diurnal
GH levels are higher at night than day –> sleep long & well for growth
Regulators of GH
GHRH and GHIH (somatostatin) from the hypothalamic neurons
-Expressed on somatotropes in AP –> release GH into bloodstream
Feedback control of GH
GH & IGF1 elicit negative feedback to stop release from hypothalamus and pituitary somatotropes
Acromegaly
Thickening of bones (especially face and hands); usually results from pituitary adenoma (hormone producing tumor in pituitary)
Thyroid Hormone
Lipid soluble hormone derived from adding 3 or 4 IODINE atoms (T3 or T4) to the amino acid tyrosine
Secreted from thyroid gland
Target cells of TH
Cells that express TH receptor (virtually every cell in the body)
TH receptor is in the cytoplasm!
What does thyroid hormone do?
Regulates body temp through nutrient metabolism
-Stimulates expression of genes involved in cellular respiration, catabolic reaction that cause heat!
TH generally increases degradation of…
Proteins, fats and carbohydrates
What is thyroglobulin and what is it secreted by?
Precurser to active T3 and T4
Secreted by secretory epithelium lining thyroid gland follicles
Thyroid Hormone Regulation
Thyrotropin releasing hormone detects low T3 & T4, TRH causes TSH to be released from anterior pituitary, and T3 and T4 are released from thyroid
What do thyroid hormones do once released?
Activate nuclear receptors in target tissue; increases metabolic rate (burn more glucose) & body temp
Where is there negative feedback with the thyroid hormone?
Any place there is a stimulatory signal, hypothalamus, AP, thyroid gland
Four general actions of thyroid hormone
- Increase basal metabolic rate
- Increase body temperature
- Increase the use of glucose and fatty acids for ATP production
- Enhance neuronal function
Iodine deficiency leads to what?
Hyper stimulation of thyrotropes by TSH because of insufficient T3/T4 negative feedback (Hypothyroidism)
Grave’s Disease
Autoimmune proteins mimic TSH –> lots of T3 and T4 (Hyperthyroidism)
Hashimoto’s Thyroiditis
Autoimmune, stops T3 and T4 production (Hypothyroidism)
Primary Thyroid Nodules
thyroid cancer
Results in hyper-secretion of T3 and T4 (Hyperthyroidism)
Goiter
Thyroid gland hypertrophy: all diseases mentioned except for cancer can lead to this
Calcium homeostasis Importance
Needed for heart to beat and for bone health
What does calcium homeostasis involve?
Parathyroid gland, intestine, bone, and kidney (target organs)
Parathyroid Hormone (intestine)
Promotes Ca 2+ absorption, requires vitamin D
Parathyroid Hormone (Bone)
Promotes reabsorption into blood (osteoclasts)
Parathyroid Hormone (Kidney)
Inhibits Ca 2+ excretion in the urine
Parathyroid glands
Embedded within the thyroid gland… Sensor & integrator all in one
Where in the parathyroid glands is PTH secreted
Chief cells when decreased plasma Ca 2+ is detected
