Ch 5 - The Endocrine System Flashcards
1
Q
What bridges the nervous and endocrine system and how?
A
- the hypothalamus; it stimulates the anterior pituitary gland through paracrine release of hormones into the hypophyseal portal system, which directly connect the 2 organs
2
Q
What mediates the release of hormones from the hypothalamus?
A
a number of factors including projections from other parts of the brain, chemo and baroreceptors in the blood vessels, and negative feedback from other hormones
3
Q
What happens in negative feedback?
A
the final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintain homeostasis
4
Q
What does the GnRH, GHRH, TRH, and CRF promote?
A
- GnRH (Gonadotropin-Releasing Hormone) promotes the release of FSH and LH targeting gonad to release testosterone/estrogen/progesterone
- GHRH (Growth Hormone-Releasing) promotes the release of growth hormone targeting bone and muscle
- TRH (Thyroid-releasing) promotes the release of TSH targeting thyroid to release T3 and T4
- CRF (Corticotropin-Releasing) promotes the release of ACTH targeting adrenal cortex to release glucocorticoids
5
Q
What does PIF or dopamine inhibit?
A
Prolactin-inhibiting factor
inhibits the release of prolactin
6
Q
Where are ADH or vasopressin and oxytocin synthesized and where to do they travel?
A
- antidiuretic hormones
- synthesized in the hypothalamus and then travel down these axons to the posterior pituitary, where they are released into the bloodstream
- interactions with the posterior pituitary occur via the axons of nerves projected by the hypothalamus
7
Q
What does the anterior pituitary release?
A
- hormones in response to stimulation from the hypothalamus (controlled by hypothalamus)
FLAT PEG - 4 of these (FSH, LH, ACTH, and TSH) are tropic hormones while 3 (prolactin, endorphins, and growth hormones) are direct hormones
8
Q
What does FSH, LH, ACTH, and TSH promote?
A
all peptide
- FSH (Follicle-stimulating) promotes the development of ovarian follicles in females and spermatogenesis in males
- LH (Luteinizing) promotes ovulation in females and testosterone production in males
- ACTH (Adrenocorticotropic) promotes the synthesis and release of glucocorticoids from adrenal cortex
- TSH (Thyroid-stimulating) promotes the synthesis and release of triiodothyronine and thyroxine from the thyroid
9
Q
What do prolactin, endorphins, and growth hormones promote?
A
all peptide
- prolactin promote milk production
- endorphins decrease perception of pain and can produce euphoria
- GH promotes growth of bone and muscle and shunts glucose to these tissues (raises blood glucose concentrations)
10
Q
What hormones do the posterior pituitary release?
A
ADH (antidiuretic hormone) or vasopressin and oxytocin (both peptides)
both produced in the hypothalamus, posterior pituitary does not synthesize any hormones itself
11
Q
What is the difference in secretion between ADH and oxytocin?
A
- ADH (vasopressin): stimulates water reabsorption in kidneys by increasing permeability of collecting duct
- oxytocin: secreted during childbirth and promotes uterine contractions, promotes milk ejection and may be involved in bonding behavior (unusual in that it has a positive feedback loop, not negative)
12
Q
Where is the thyroid located?
A
at the base of the neck in front of the trachea
13
Q
What 3 key hormones does the thyroid produce?
A
- Triiodothyronine (T3) and thyroxine (T4): produced by follicular cells and stimulate metabolic activity (thyroid hormones are required for proper neurological and physical development in children)
- calcitonin: produced by parafollicular (C) cells, decreases plasma calcium concentration by promoting calcium excretion in the kidneys, decreasing calcium absorption in the gut and promoting calcium storage in bone
14
Q
What do the parathyroid glands release and what does that cause?
A
release parathyroid hormone (PTH) which increases blood calcium concentration
15
Q
What does PTH decrease/increase, activate, and promote?
A
- decreases excretion of calcium by the kidneys and increase bone resorption directly to increase blood calcium concentration
- activates vitamin D, which is necessary for calcium and phosphate absorption from the gut
- promotes resorption of phosphate from bone and reduces reabsorption of phosphate in the kidney, but vitamin D promotes absorption of phosphate from the gut; these 2 effects on phosphate concentration somewhat cancel each other out
16
Q
What does the adrenal cortex produce?
A
3 classes of steroid hormones: glucocorticoids (sugar), mineralocorticoids (salt), and cortical sex hormones (sex)
17
Q
What are glucocorticoids and what do they do? What stimulates its release?
A
- such as cortisol and cortisone
- increase blood glucose concentration, reduce protein synthesis, inhibit the immune system, and participate in the stress response, anti inflammatory
- release is stimulated by ACTH
18
Q
What are mineralocorticoids and what do they do? What regulates its activity?
A
- such as aldosterone
- increase water reabsorption in the kidneys by promotes sodium reabsorption
- increases potassium and hydrogen ion excretion
- activity is regulated by the renin-angiotensin-aldosterone system, not ACTH
19
Q
What are cortical sex hormones?
A
include androgens (like testosterone) and estrogens in both males and females
20
Q
Where is the adrenal medulla derived from and what does it secrete?
A
- derived from the nervous system
- secretes catecholamines into the bloodstream
21
Q
What are the 2 catecholamines, what do they do, and what synthesizes them?
A
- include epinephrine and norepinephrine
- involved in the fight or flight (sympathetic) response
- promote glycogenolysis, increase the basal metabolic rate, increase HR, dilate the bronchi, and alter blood flow
- synthesized by adrenal medulla
22
Q
What does the endocrine pancreas produce?
A
hormones that regulate glucose homeostasis: glucagon, insulin, and somatostatin
23
Q
What produces glucagon and what does it do?
A
- produced by alpha cells
- raises blood glucose levels by stimulating protein and fate degradation, glycogenolysis, and gluconeogenesis
- glucagon levels are high when glucose is gone
24
Q
What produces insulin and what does it do?
A
- produced by beta cells
- lowers blood glucose levels by stimulating glucose uptake by cells and promoting anabolic processes, like glycogen, fat, and protein synthesis
25
What produces somatostatin and what does it do?
- produced by gamma cells
- inhibits insulin and glucagon secretion
- pancreatic somatostatin secretion is increased by high blood glucose or amino acid levels, leading to decreased insulin and glucagon secretion
26
What kind of hormones do the gonads produce and how are these hormones secreted?
- hormones that are involved in the development of maintenance of the reproductive systems and secondary sex characteristics
- testes secrete testosterone
- ovaries secrete estrogen and progesterone
27
What does the pineal gland release and what does that release do?
releases melatonin which helps regulate circadian rhythm
28
What hormones do cells in the stomach and intestine produce?
secretin, gastrin, and cholecstokinin
29
What hormones do the kidneys secrete and what do these hormones do?
secrete erythropoietin which stimulates bone marrow to produce erythrocytes (RBC) in response to low oxygen levels in the blood
30
What hormones do the atria of the heart secret and what do these hormones do?
atrial natriuretic peptide (ANP) which promotes excretion of salt and water in the kidneys in response to stretching of the atria (high blood volume)
31
What hormone does the thymus secrete and what does this hormone do?
secretes thymosin which is important for proper T cell development and differentiation
32
What is the difference between peptide and steroid hormones?
- peptide: amino acids (chemical precursor), receptor located extracellular, stimulates a receptor affecting levels of second messengers (cAMP) initiating signal cascade, dissolve and travel freely through bloodstream, quick onset, short lived
- steroid: cholesterol (chemical precursor), receptor located intracellular, binds to a receptor inducing conformational change and regulates transcription at the level of DNA, binds to a carrier protein in bloodstream, slow onset, long lived
33
What is the difference between insulin and estrogen/testosterone?
- insulin is a peptide hormone, and it has to be released at every meal in order to be active (fast onset, short acting)
- estrogen/testosterone are steroid hormones that promote sexual maturation (slower, long lasting changes)
34
What is the difference between the amino acid derivative mechanism of (nor)epinephrine and thyroxine, T3?
- (nor)epinephrine have extremely fast onset but are short lived, like peptide hormones (adrenaline)
- thyroxine and T3 have slower onset but a longer duration like steroid hormones and regulate metabolic rate over a long period of time
35
What is the difference between the naming of steroid, peptide, and amino acid derivative hormones:
- most peptide and amino acid derivatives hormones have names that end in -in or -ine
- most steroid hormones have names that end in -one, -ol, or -oid
36
How are amino acid derivative hormones synthesized?
made by modifying amino acids such as the addition of iodine to typrine (in thyroid hormone production)
37
What is the difference between a direct and tropic hormone?
- direct: secreted into the bloodstream and travel to a target tissue, where they have direct effects
- tropic: cause secretion of another hormone that then travels to the target tissue to cause an effect
38
Which hormone in the anterior pituitary does not require a factor from the hypothalamus to be released?
prolactin
- as long as the hypothalamus releases PIF (dopamine), no prolactin will be released
- it is the absence of PIF that allows prolactin to be released
39
What is the negative feedback mechanism between the hypothalamus, anterior pituitary, adrenal cortex, and cortisol?
- release of CRF from the hypothalamus stimulates anterior pituitary to secrete ACTH which causes the adrenal cortex to increase secretion of cortisol levels into the blood
- cortisol is detrimental when levels become too high, so to prevent excess cortisol secretion, cortisol inhibits the hypothalamus and anterior pituitary from release CRF and ACTH
40
What are the critically important functions of calcium?
- bone structure and strength
- release of neurotransmitters from neurons
- regulation of muscle contraction
- clotting of blood (cofactor)
- plays role in cell movement and exocytosis of cellular materials
41
How do PTH and calcitonin affect calcium levels?
PTH increases serum calcium levels
| calcitonin decreases calcium levels
42
How do insulin, glucagon, and growth hormones, glucocorticoids, and epinephrine affect plasma glucose?
- insulin decreases plasma glucose
- glucagon increases plasma glucose
- GH, glucocorticoids, and epi increase plasma glucose
43
What are counterregulatory hormones?
hormones that raise blood glucose levels
44
What is the relationship between insulin and blood glucose?
high blood glucose --> stimulates insulin secretion --> lower blood glucose level --> inhibits insulin --> rise in blood glucose level (repeat)
45
Which 3 hormones are primarily involved in water homeostasis? Where does each come from and what effects does each have on blood volume and osmolarity?
- ADH (vasopressin) from hypothalamus (released by posterior pituitary) increases blood volume and decreases blood osmolarity
- aldosterone from adrenal cortex increases blood volume with no effect on blood osmolarity
- ANP from the heart decreases blood volume with no effect on blood osmolarity
46
What is cretinism?
- characterized by poor neurological and physical development (including retardation, short stature, and coarse facial features)
- can be caused by hypothyroidism in newborn infants which can be caused by inflammation of thyroid or iodine deficiency
