Chapter 23 Endocrine Control of Growth Flashcards
What are the steps in Cortisol synthesis?
hypothalamus –CRH–> anterior pituitary –ACTH–> adrenal cortex—–> cortisol
What does cortisol do to the immune system?
suppresses immune function
What does cortisol do to the liver?
gluconeogenesis
What does cortisol do to muscles?
protein catabolism
what does cortisol do to adipose tissue?
lipolysis
What stimulates cortisol synthesis?
ACTH
How is cortisol transported?
transported in the plasma to target cell which it diffuses into cells and binds to intracellular receptors that enter the nucleus and binds to DNA.
What does cortisol control?
gene expression
How does cortisol protect against hypoglycemia?
by promoting gluconeogenesis, breaking down skeletal muscle protein, enhancing lipolysis, suppressing immune function, causing calcium and bone matrix loss, causing mood changes and alters learning & memory.
What disease are associated with hypercortisolism?
Chushing’s syndrome (caused by pituitary tumor increasing ACTH)
(2ndary hypercortisolism)
What disease is associated with hypocorticolism?
Addison’s disease (caused by autoimmune disease of the adrenal cortex)
What is POMC and what does it produce?
a prohormone that produces ACTH & a-MSH
What does the hormone a-MSH (melanocyte-stimulating hormone) do?
Melanin synthesis, immune response and decrease food intake
Which melanocortin receptor is found in skin melanocytes and causes skin darkening?
MC1
Which melanocortin receptor is found in the adrenal cortex and stimulate cortisol secretion?
MC2
Which melanocortin receptor is found in the hypothalamus and inhibits feeding?
MC4
Which melanocortin receptor(s) respond to BOTH ACTH and MSH?
MC1 & MC4
Which melanocortin receptor only responds to ACTH and not MSH?
MC2
Which hormone(s) increase feeding?
ghrelin—–> neuropeptide Y
What hormone(s) decrease feeding?
a-MSH & Leptin
What are the 6 steps involved in the synthesis of thyroid hormones (T3, T4)?
- Na+/I- symporter brings I- into the cell, then the Pendrin transporter moves I- into the colloid
- Follicular cell synthesizes enzymes & thyroglobulin for colloid
- Thyroid peroxidase adds I- to tyrosine making T3 & T4
- Thyroglobulin containing T3 & T4 is transported back into the follicular cell in vesicles
- Intracellular enzymes separate T3 & T4 from the protein
- Free T3 & T4 enter circulation
How are thyroid hormones transported to target cells?
Thyroid hormones are hydrophobic transported in the plasma bound to globulin (not thyroglobulin) and bind to intracellular receptors in the nucleus to regulate gene expression
What do thyroid hormones do in adults?
Increase oxygen consumption, generate heat and alter ion transport across cell and mitochondrial membranes
What do thyroid hormone do in children?
facilitate growth hormone action, promote myelin and synapse formation
(thyroid hormones in children are needed for normal growth and development)
What are consequences of hyperthyroidism?
increased oxygen consumption & heat production, protein breakdown & muscle weakness, rapid heartbeat and psychological effects
What are consequences of hypothyroidism?
Slower oxygen consumption & intolerance of cold, decreased protein synthesis, slowed reflexes, speech & thought and slow heart rate (bradycardia)
What are the steps in control of thyroid hormone release?
hypothalamus–TRH–> anterior pit.–TSH–> thyroid gland——–>T3 & T4
What are the steps in the release of Growth Hormones?
circadian rhythm, stress & cortisol, and fasting———————-> hypothalamus–GHRH–> anterior pit.–GH–> liver–IGF—-> cartilage growth
What hormones inhibit GH?
somatostatin & IGF (insulin-like growth factors)
What are function of GH?
stimulates bone & tissue growth and increases blood glucose
What is the function of the hormone IGF?
Cartilage growth
What is the function of GH in children?
influences bone growth
What will excess GH and GH deficiency cause in children?
excess GH–> gigantism
GH deficiency—> dwarfism
What does excess GH in adults cause?
acromegaly
What is the function of GH in adults?
acts on cartilage & soft tissue
Where in the bone does bone growth occur?
epiphyseal plate
When does bone growth stop?
sex hormones lead to inactivation of the epiphyseal plate following puberty
What produced bone cartilage?
chondrocytes
What is laid down on the collagen matrix?
calcium phosphate (hydroxyapatite)
What is cartilage made of?
collagen & proteoglycan
Where is calcium taken up, eliminated and stored in?
taken up by intestine
eliminated by kidneys
stored in bone
What are the roles of PTH, calcitriol, cortisol and calcitonin in bones?
PTH, calcitriol & cortisol release calcium from bone (osteoclastic activity)
Calcitonin = osteoblast activity (building bone)
What is released when blood calcium levels are low?
PTH–Ca2+—> Kidney—calcitriol—> increases Ca2+ in distal nephron & intestine
What is the 0.1% Ca2+ in the ECF essential for?
second messanger, tight junction integrity, blood coagulation and neuron polarization
PTH stimulated calcitriol production in the _________.
kidney
Which hormones are peptide hormones?
GH, calcitonin, PTH and IGF (insulin-like growth factor)
Which hormones are steroid hormones?
cortisol, aldosterone, TH, and calcitriol (D3)
What is bone reabsorption mediated by?
Osteoclasts
What is bone deposition mediated by?
Osteoblasts
