Chapter 18 Flashcards
Exocrine glands
Secrete their products into ducts that carry the secretions into body cavities, the lumen of an organ, or the outer surface of the body
include sweat glands, oil glands, mucus, and digestive glands
Endocrine glands
Secrete their products into the interstitial fluid surrounding the secretory cells rather than into ducts who then diffuse into blood capillaries then blood carries them to target cells throughout the body
What does the endocrine glands include?
Pituitary, thyroid, parathyroid, adrenal and pineal glands
Down-regulation
If a hormone is present in excess the number of target cell receptors decrease
Up regulation
When a hormone is deficient the number of receptors may increase
making the target cell more sensitive to a hormone
What other organs can secrete hormones?
Hypothalamus
thymus
pancreas
ovaries
testes
kidneys
stomach
liver
small intestine
skin
heart
adipose tissue
placenta
Circulating hormones
Pass from the secretory cells that make them into interstitial fluid and then into the blood
Local hormones
Act locally on neighbouring cells or on the same cell that secreted them without entering the bloodstream
Paracrines
Local hormones that act on neighbouring cells
Autocrines
Hormones that act on the same cell that secreted them
What are the three lipid soluble hormones?
- Steroid hormones
- Thyroid hormones
- Nitric oxide
Steroid hormones are derived from what?
Cholesterol
What is synthesized by attaching iodine to the amino acid tyrosine?
Thyroid hormones T3 and T4
What lipid soluble hormone is both a hormone and a neurotransmitter?
Nitric oxide (NO)
What are the three water soluble hormones?
- Amine hormones
- Peptide and protein hormones
- Eicosanoid hormones
How are Amine hormone synthesized?
By decarboxylating and otherwise modifying certain amino acids they are called amines because they retain an amino group
What are some examples of peptide hormones and protein hormones?
Peptide: antidiuretic and oxytocin
Protein: Growth hormone and insulin
What’s an example of Glycoprotein hormones?
Thyroid stimulating hormone
What are the two major types of Eicosanoids?
Prostaglandins and leukotrienes
How do water soluble hormone molecules circulate in the blood plasma?
In a “free” form
How do you lipid soluble hormone molecules move through the blood?
Via transport proteins
What are the three functions of the transport protein?
- They make lipid soluble hormones temporarily water soluble thus increasing their solubility in blood
- They retard passage of small hormone molecules through the filtering mechanism in the kidneys thus slowing the rate of hormone loss in the urine
- They provide a ready reserve of hormone already present in the bloodstream
Free fraction
The .1 to 10% of the molecules of lipid soluble hormones that are not bound to a transport protein that diffuse out of capillaries, bind to receptors and trigger responses
First messenger
When a water soluble hormone binds to its receptor at the outer surface of the plasma membrane
Second messenger
The first messenger causes production of the second messengers inside the cell where specific hormone stimulated responses take place
What is a common second messenger?
Cyclic adenosine monophosphate
Permissive affect
When a hormone will only work if there was Recent exposure from a second hormone
Synergistic effect
When the effect of two hormones acting together is greater than the sum of their individual effects
Antagonistic effects
When one hormone opposes the actions of another hormone the two hormones have an antagonistic effect
Control of hormone secretion
The release of most hormones occurs in short bursts with little or no secretion between bursts when stimulated an endocrine gland will release its hormone in more frequent bursts increasing concentration of the hormone in the blood
What are the three things hormone secretion is regulated by?
- Signals from the nervous system
- Chemical changes in the blood
- Other hormones
What are the other words and terms for pituitary gland?
Hypophysis and “master” endocrine gland
What gland controls the “master” gland?
Hypothalamus
Infundibulum
Stalk connecting the hypothalamus and pituitary
Anterior pituitary
Also called adenohypophysis
75% of glands weight
Made of epithelial tissue
Two parts: pars distalis and pars tuberalis
Posterior pituitary
Also called neurohypophysis
Made of neural tissue
Two parts: pars nervosa and pars intermedia
What are the five anterior pituitary cells?
- Somatrophs
- Thyrotrophs
- Gonadotrophs
- Corticotrophs
- Lactotrophs
Somatrophs secrete what hormones?
Growth hormone and somatropin
Thyrotrophs secret what hormone?
Thyroid-stimulating hormone
Gonadotrophs secret what hormone?
Follicle stimulating hormone and lutenizing hormone
Lactotrophs secrete what hormone?
Prolactin
Corticotrophs secret what hormone?
Adrenocorticotropic hormone (ACTH)/ corticotropin and melanocyte stimulating hormone (MSH)
What is prolactin inhibiting hormone?
Dopamine
What is growth hormone inhibiting hormone?
Somatostatin
Hypophyseal portal system
Blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary
Allows communication between hypothalamus and anterior pituitary
Link between nervous system and endocrine system
Superior hypophyseal arteries
Branches of the internal carotid arteries bring blood into the hypothalamus at the junction of the median eminence of the hypothalamus and the infundibulum and divide into a Capillery network called the primary plexus of the hypophyseal portal system
Neurosecretory cells
Clusters of neurons above the optic Chiasm
Tropic hormones
Anterior pituitary hormones that act on other endocrine glands
How does GH exert its growth promoting affects indirectly through small protein hormones?
With insulin-like growth factors (IGFs) / somatomedins
What are the specific functions of insulin like growth factors(IGFs)?
- Increase growth of bones and soft tissues
- Enhance lipolysis
- Decrease glucose uptake
How is growth hormone regulated by GHRH and GHIH?
- GHRH is secreted by the hypothalamus. Due to Hypoglycemia, decrease blood levels of fatty acids, increase blood levels of amino acids, deep sleep, increased activity of the sympathetic nervous system, and other hormones including testosterone, estrogen, thyroid, hormones and ghrelin
- Once secreted, GHRH enters the hypophyseal portal system and flows to the anterior pituitary where it stimulates somatotrophs to secrete GH
- GH Acts directly on various cells to promote certain metabolic reactions in liver, bone, skeletal muscle, and cartilage GH is converted to IGF’s which intern promote growth of bone, skeletal muscle, and other tissues
- Elevated levels of GH and IGFs inhibit release of GHRH and GH
- GHIH is secreted by the hypothalamus
- GHIH enters the hypophyseal portal system and flows to the anterior pituitary where it prevents the somatotrophs from secreting GH by interfering with the signaling pathway used by GHRH
Adrenocorticotropic hormones
Secreted by Corticotrophs
Controls the production and secretion of cortisol and other glucocorticoids by the cortex of the adrenal glands
Stored hormones In posterior pituitary?
Oxytocin and anti diuretic
Thyroid gland
Composed of right and left lobes connected by the Isthmus, anterior to the trachea
Made of thyroid follicles, follicular cells, and a basement membrane
Produces thyroxine and triiodothyronine
Paraflicular cells produce calcitonin
Steps for synthesis and secretion of t3 and t4?
- Iodide trapping
- Synthesis of thyroglobulin
- Oxidation of iodide
- Iodination of tyrosine
- Coupling of t1 and t2
- Pinocytosis and digestion of colloid
- Secretion of thyroid hormones
- Transport in the blood
Functions of thyroid hormones?
- Increase basal metabolic rate
- Enhance actions of catecholamines
- Regulate development and growth of nervous tissue and bones
Calcitonin
Produced by parafollicular cells of the thyroid gland
Decrease the level of calcium in the blood by inhibiting the action of osteoclast
Parathyroid gland
One superior and one inferior the parathyroid glands are attached to each lateral thyroid lobe =4
Chief cells produce parathyroid hormone
Oxyphil cells don’t produce anything normally
Parathyroid hormone
Major regulator of calcium, magnesium and phosphate levels
Elevate bone resorption
Slows the rate at which calcium and magnesium are lost from the blood into the urine increases loss of HPO 42-
Promote formation of calcitriol
Adrenal glands
Superior to each kidney
Consists of adrenal cortex and adrenal medulla
Produces steroid hormones: Norepinephrine, epinephrine, dopamine
Adrenal cortex
Zona glomerulosa: mineralcorticoids
Zona fasciculata: glucocorticoids
Zona reticularis: androgens
Mineralcorticoids
Aldosterone
Regulates homeostasis of sodium ions and potassium ions and also promote excretion of hydrogen ions in the urine
The renin angiotensin-aldosterone (RAA) pathway That controls secretion of aldosterone
- Stimuli that initiate the renin angiotensin aldosterone pathway include dehydration, sodium deficiency, or haemorrhage
- These conditions cause a decrease in blood volume
- Decrease blood volume leads to decrease blood pressure
- Lower blood pressure stimulate certain cells of the kidneys call juxtaglomerular cells to secret the enzyme renin
- Renin in blood increases
- Renin converts angiotension a plasma protein produced by the liver into angiotension 1
- Blood containing increase levels of angiotension one circulates in the body
- As blood flows through capillaries particularly those of the lungs the enzyme angiotensin-converting enzyme converts angiotension one into the hormone angiotension two
- Blood level of angiotension 2 increases
- Angiotension two stimulates the adrenal cortex to secrete aldosterone
- Blood containing increase levels of aldosterone circulates to the kidneys
- In the kidneys aldosterone increases reabsorption of sodium which in turn causes reabsorption of water by osmosis as a result less water is lost in the urine aldosterone also stimulates the kidneys to increase the secretion of potassium and hydrogen into the urine
- Increased water reabsorption by the kidneys, blood volume increases
- As blood volume increases blood pressure increases to normal
- Angiotension 2 also stimulates contraction of smooth muscle in the walls of arterrials the resulting vaso construction of the materials increases blood pressure and thus helps raise blood pressure to normal
Effects of glucocorticoids?
- Protein breakdown
- Glucose formation
- Lipolysis
- Resistance to stress
- Anti-inflammatory
- Depression of immune responses
Androgens
Testosterone and estrogen
Adrenal medulla
Hormone producing cell called chromaffin cells synthesize epinephrine and norepinephrine
Pancreas
Cells called acini that produce digestive enzymes
With clusters of pancreatic islets
Cells types of the pancreatic islets
- Alpha/ A cells produce glucagon
- Beta/ B cells produce insulin
- Delta/ D cells somatostatin
- F cells secret pancreatic polypeptide
Insulin secretion is also stimulated by
- Acetylcholine the neurotransmitter liberated from axon terminals
- Amino acids arginine and Lusine which would be present in the blood at higher levels after a protein containing meal
- Glucose dependent insulinotropic peptide
Glucagon is stimulated by
Increase activity of a sympathetic division of the ANS
A rise in blood amino acid if blood glucose level is low
