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Bio40c > Endocrine System Concepts > Flashcards

Endocrine System Concepts Flashcards

1
Q

Contrast endocrine vs. exocrine function, considering the products released, the location of release, and the fate of released substances.

A

Endocrine (release into the body): release hormones at the thyroid, parathyroid, adrenal, pineal, pituitary

Exocrine (release out away from the body): release sweat on the skin

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2
Q

Review the difference between paracrine, autocrine, and endocrine function, focusing on the location of target cells of each, and trying to come up with at least one simple example of each. (Autocrine = Interleukin 2 of T cells?, Paracrine = nitric oxide release, interferon release…)

A

Autocrine
- Feeding itself

Paracrine
- Releasing hormones traveling short distances within a tissue to get to near target cell

Endocrine
-circulates within the bloodstream to get to distant target cell

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3
Q

Explain how and why the down-regulation and up-regulation of hormone receptors work.

A

If circulating hormone levels are high, the # of receptors is “down-regulated” (drop # of receptors available because you don’t need them)

If they’re low, the # of receptors is “up-regulated” (increase # of receptors available)

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4
Q

Link down-regulation to Type 2 diabetes

A

Due to too much insulin circulating in the blood caused by a sugar-high diet, insulin receptors on a target cell membrane may be down regulated, or decreased, to desensitize the effects of insulin

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5
Q

Contrast travel of water-soluble and lipid-soluble hormones in the blood. Focusing on how lipid-soluble hormones are carried in the blood, and which type is more prone to being filtered at the glomeruli of the kidney

A
  • Water-soluble hormones dissolve freely in the blood plasma
  • Lipid-soluble hormones need to bind to transport proteins in order to temporarily become water-soluble and not get easily filtered at the kidney
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6
Q

Describe the mechanism of action of a lipid-soluble hormone on a target cell, being very detailed.

A
  • Transport protein carrying lipid-soluble hormone through the blood plasma
  • Lip-soluble hormones diffuse through the target cell membrane and bind to receptors in the nucleus
    Transcription and translation are stimulated to make new proteins
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7
Q

Which of the 4 macromolecules is usually most affected by hormones?

A

protein

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8
Q

Describe the mechanism of action of a water-soluble hormone on a target cell, being very detailed.

A
  • Water soluble hormones cannot enter the cell directly so they bind to a receptor on the OUTSIDE of the target cell membrane and trigger a whole cascade of events INSIDE the cell
  • The binding of hormone (first messenger) to its receptor activates G protein, which activates adenylyl cyclase
  • Activated adenylyl cyclase converts ATP to cAMP
  • cAMP serves as a second messenger to activate protein kinases
  • Activated protein kinases phosphorylate cellular proteins
  • Millions of phosphorylated proteins cause reactions that produce physiological responses
  • Phosphodiesterase eventually inactivates cAMP to end the cascade
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9
Q

Connect endocrine function (negative feedback loops driven by endocrine organs and key hormones) with blood panel parameters. Consider the contrasting effects, on these blood panel parameters, of stress and the endocrine system.

A
  • Parathyroid gland cells detect lowered Ca concentrations in the blood, so the PTH gene is “turned on” to increase the release of PTH onto the kidneys to retain Ca in the blood. Osteoclasts also increase bone reabsorption to increase blood Ca.
  • After fight or flight (stress), insulin is secreted in the kidneys to lower blood sugar levels through the parasympathetic system (rest and recovery)
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10
Q

Give 5 effects of hormones on cellular function, concentrating on the role of proteins in each.

A
  • Stimulate the synthesis of something new within a cell
  • Change the permeability of a cell’s membrane
  • Change the transport rates of certain substances across a cell’s membrane
  • Change the rate of metabolic reaction
  • Contract smooth or cardiac muscle
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11
Q

Describe the amplification of a water-soluble hormone at the cellular level

A

One water-soluble hormone molecule binding to a receptor on the outside of the cell can result in the production of millions of molecules inside the cell

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12
Q

Contrast synergistic and antagonistic effects of hormones, giving an example of each (e.g. epinephrine & norepinephrine for synergistic?)

A

Synergistic (epinephrine & norepinephrine)
- Sometimes two hormones work together on a cell in a kind of 1-2 punch
- The first hormone “loosens up” the cell and the second has a greater effect on the cell if the first one has already been at work amplifying

Antagonistic (insulin and glucagon)
- Insulin and glucagon have opposite effects on a cell

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13
Q

Name, and give a very brief description of the 3 ways that hormone release is controlled in the body.

A

ANS innervation,
- craniosacral output (parasympathetic)
- Secrete insulin to lower blood sugar levels after fight or flight

Blood chemistry
- Parathyroid gland cells detect lowered calcium levels in blood which kicks a negative feedback loop to correct calcium levels by bringing them back up

Other hormones ( The HP axis)
- Anterior pituitary hormones

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14
Q

What is the “master endocrine” organ

A

the hypothalamus is the “master endocrine” organ and it drives the posterior and anterior pituitary, creating the incredibly important HP axis

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15
Q

Specifically, describe how the hypothalamus drives secretion of neurohypophyseal hormones, focusing on hypothalamic nuclei, releasing hormones, the hypothalami-hypophyseal tract, and the specific mechanisms whereby hypothalamic hormones are sent to the neurohypophysis

A
  • The supraoptic and paraventricular nuclei of the hypothalamus produce two neurohypophyseal hormones ADH and oxytocin
  • These 2 hormones are packaged into vesicles and shipped down the axons of neurons to the axon terminals in the posterior pituitary
  • The axons of those neurons are grouped together to make the “hypothalamohypophyseal tract”
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16
Q

Contrast the two pituitaries (anterior and posterior), focusing on alternate names, sizes, types of tissue, and means of receiving hypothalamic hormones.

A

Anterior:
- “Adenohypophysis”
- Bigger (75%)
- Endocrine tissue
- Hypophyseal portal system (blood vessels)

Posterior:
- “Neurohypophysis”
- Smaller (25%)
- Nervous tissue
- Hypothalamic-hypophyseal tract (nerves)

17
Q

Discuss ADH as one of the two neurohypophyseal hormones, focusing on its role in a negative feedback loop offsetting low blood volume at the level of the kidney

A
  • The receptors in the hypothalamus sense low blood volume and high blood osmolarity
  • ADH will increase blood volume (at the kidney, Na is pulled out, and where Na goes, water follows)
  • Once ADH causes a corrective increase in blood volume and blood osmolarity, osmoreceptors in the hypothalamus will no longer stimulate the release of ADH from the posterior pituitary
18
Q

Discuss oxytocin as the other, focusing on its role in 2 separate positive feedback loops, facilitating birthing and ejection of breast milk.

A
  • Contraction of smooth muscles in the uterine wall stimulates the release of oxytocin which is sensed by cell bodies in the hypothalamic nuclei (paraventricular). This stimulates the release of more oxytocin, and this increased oxytocin stimulates more contraction of the uterine wall
  • Mechanical stimulation of the nipple by suckling infants stimulates the release of oxytocin, which is sensed by cell bodies in the hypothalamic nuclei (paraventricular). This stimulates the release of more oxytocin, and this increased oxytocin stimulates the ejection of breast milk by the mammary glands which can stimulate more sucking from the infant
19
Q

Understand the role of the infundibulum and the capillary plexus of the posterior pituitary, in the systemic distribution of neurohypophyseal hormones.

A
  • The infundibulum is the thin “stalk” connecting the hypothalamus superiorly with the pituitary inferiorly. It holds the hypothalamohypophyseal tract
  • The capillary plexus of the posterior pituitary is a network of capillaries surrounding the posterior pituitary. It’s the point of entrance of neurohypophyseal hormones into the bloodstream
20
Q

What is the role of each of the 7 hypothalamic hormones?

A

The hormones either stimulate the release of trophic (hypophyseal) hormones or inhibit their release.

21
Q

What is the path of the 7 hypothalamic hormones to the anterior pituitary, and the target trophic cells in the anterior pituitary?

A
  • 7 different hypothalamic hormones are released from short neurosecretory cells and diffuse into the primary plexus located around the infundibulum
  • From the primary plexus, 7 hypothalamic hormones enter the hypophyseal portal veins for travel to the anterior pituitary and arrive at the 5 types of cells that secrete trophic (hypophyseal) hormones which are: Somatotrophs, Thyrotrophs, Gonadotrophs, Lactotrophs, and Corticotrophs
22
Q

Explain how negative feedback loops decrease levels of effector hormones in the absence of hypothalamic inhibitory hormones (growth hormone and prolactin). How do you drop effector hormone levels for the other 3 pathways without inhibiting hormones, focusing on which molecules do the inhibition, what organs they target, and what the inhibitory effects are at each organ they target?

A

Thyropin
- Thyrotropin from the hypothalamus triggers the release of Thyrotrophs from the anterior pituitary, which triggers the release of thyroid-stimulating hormone (TSH) which triggers the release of T3 and T4 from the thyroid gland

  • Elevated T3 and T4 in the blood suppress the release of thyrotropin by the hypothalamic neurosecretory cells and thyrotrophs from the anterior pituitary

Gonadotropin
- Gonadotropin from the hypothalamus triggers the release of Gonadotrophs from the anterior pituitary, which triggers the release of follicle-stimulating hormones and luteinizing hormones which triggers the release of sex hormones by the ovaries and testes

  • Elevated sex hormones (estrogen and progesterone in females and testosterone in males) in the blood suppress the release of Gonadotropin by hypothalamic neurosecretory cells and Gondadotrophs by the anterior pituitary

Corticotropin
- CRH from the hypothalamus triggers the release of ACTH from the anterior pituitary, which triggers the release of adrenocorticotrophin hormone (ACTH) which triggers the release of cortisol by adrenal glands

  • But elevated cortisol levels in the blood suppress the release of CRH by hypothalamic neurosecretory cells & ACTH by the anterior pituitary
23
Q

Describe the location and general anatomy of the adrenal glands.

A
  • Sit on top of kidneys
  • Shaped like a slice of bread
  • Heavily vascularized
  • Outer cortex (80-90%) of mass surrounds a much smaller inner medulla
24
Q

Name, locate, and describe the 3 zones of the adrenal cortex (cortical zones) and a key hormone produced in each. Know the general role of the key hormone produced in each zone. Identify which of the 3 regions is most noticeably under hormonal control by the HP axis.

A

From superficial to deep:
Zona glomerulosa: secretes aldosterone which modifies the amount of Na and water reabsorbed from the urine to help boost blood volume
- Most superficial layer of the adrenal cortex

Zona fasciculata: secretes cortisol which stimulate protein breakdown
- The middle and far largested layer

Zona reticula: secretes weak androgen which have minimal effect on body
- Deepest layer

The zona fascicullata is most noticeably under hormonal control by the HP axis

25
Q

Discuss the role of the adrenal medulla, the key catecholamines released, how they’re controlled by the sympathetic arm of the ANS, and the tissue and cellular effects of those catecholamines

A
  • Adrenal medula is modified sympathetic ANS nervous tissue
  • Basically a sympathetic ans ganglion that gets pinged constantly by sympathetic preganglionic (myelinated) neurons as part of thoracolumbar outflow
  • Catecholamines intensify neuronal sympathetic responses as part of the “fight or flight” responses throughout the body
26
Q

Connect adrenal medullar catecholamine action to the action of the same catecholamines as neurotransmitters of the ANS

A

Both play an important role in the body’s fight or flight response, and their release into the bloodstream causes increases in blood pressure, heart rate, and blood sugar levels

27
Q

Contrast the volume and function of pancreatic acini with pancreatic islets, focusing on exocrine vs. endocrine function

A

Pancreatic Acini:
- Exocrine function (99% mass of organ)
- Spread throughout the organ synthezising and secreting digestive enzymes into small intestine

Pancreatic Islets:
- Endocrine function (1% of pancreatic tissue)
- In tiny clusters
- Surrounded by a sea of exocrine tissue (acini)

28
Q

Discuss the 4 types of endocrine cells found in the pancreatic islets, focusing on the 2 that produce hormones critical to carbohydrate metabolism, the antagonistic role of those 2 regulatory hormones, and their contrasting roles in negative feedback loops to correct blood hypoglycemia and hyperglycemia, touching back on which arm of the ANS responds to hypo- and hyper-glycemia

A

The 4 types of endocrine cells found in the pancreatic islets are Alpha cell, Beta cell, Delta cell, and Pancreatic polypeptide cell. The 2 that produce hormones critical to carbohydrate metabolism are alpha cells and beta cells. Alpha cells secretes glucagon and beta cells secrete insulin which are antagonistic hormones regulating blood glucose. Glucagon increases blood sugar levels and insulin decreases. The sympathetic arm of the ANS response to hypoglycemia and the parasympatheic arm respondse to hyperglycemia.

29
Q

Describe the location and general anatomy of the thyroid and parathyroid glands

A
  • Butterfly-shaped gland wrapped around the anterior aspect of the trachea
  • Just inferior to the larynx
  • Right and left lobes connected by the isthmus. Some thyroids have a 3rd (pyramidal) lobe superior to the isthmus
  • parathyroid are 4 nubs on the posterior aspect of the thymus
30
Q

Describe the histology of a thyroid follicle, and briefly describe the most general features of the process by which T3 & T4 are synthesized in the follicle.

A
  • Each follicle has T thyrocytes (epithelial follicular cells) surrounding the lumen of the follicle. These T thyrocytes synthesize T3 & T4
  • C thyrocyte in between thyroid follicles
  • Thyroglobulin (TGB) in the lumen

When stimulated by thyroid stimulating hormones (TSH), follicular cells (T-thyrocytes) swell up and begin to synthesize T3&T4

31
Q

Connect T3 & T4 synthesis back to control by the HP axis.

A
  • The hypothalamus can drive the thyroid
  • Thyrotropin from the hypothalamic neurosecretory cells triggers thyrotrophs to stimulate thyroid stimulating hormone (TSH) in the anterior pituitary which triggers the release of T3 & T4 by the thyroid gland
  • Elevated levels of T3 & T4 in the blood will go back and inhibit the release of Thyrotropin and Thyrotrophs
32
Q

Contrast the location and histology of follicular and parafollicular cells

A

Follicular:
Surrounds the lumen of the follicle

Parafollicular:
Lies in between the follicles of the thyroid

33
Q

Describe the role of parafollicular cells in Ca homeostasis, focusing on the specific tissue where calcitonin will go to try to offset hypercalcemia

A
  • C thyrocytes produce Calcitonin, which together with parathyroid hormone, works antagonistically to regulate blood CA
  • If blood Ca gets too high, the thyroid senses the disruption in homeostasis and produces calcitonin
  • The calcitonin goes to bone tissue inhibits osteoclast activity and accelerates uptake of Ca and PO4 into bone ECM (calcification of bone)
34
Q

Describe the role of parathyroid chief (or principal) cells in Ca homeostasis, focusing on the 3 tissues that parathyroid hormone will go to try to correct hypocalcemia and its general effects on those 3 tissues.

A

The cells synthesize and release parathyroid hormone (PTH) into the blood.

  • PTH goes to bone tissue and stimulates osteoblclastic activity
  • PTH goes to the kidneys and slows the rate of loss of Ca from the blood to urine
  • PTH promotes the formation of calcitriol, the active form of Vit. D that increases intestinal uptake of Ca from diet
35
Q

Describe, briefly, the role of the pineal gland and thymus in homeostasis

A

Pineal gland:
Secretes melatonin, a critical hormone that regulates sleep/waking cycles

Thymus:
Releases a handful of hormones that promote the maturation of T cells that are very important WBC involved in immune response

36
Q

Discuss how two eicosanoids (prostaglandins and leukotrienes) are formed, what type of hormone they are, and how they act in an autocrine/paracrine way throughout the body focusing on some general effects of these eicosanoids on homeostasis

A

They are formed by clipping 20 carbons off of membrane phospholipids. They are water-soluble eicosanoid hormones. They move locally to bind to cell receptors:

  • Smooth muscle contraction
  • Glandular secretion
  • Platelet function
  • Respiration
  • Immune response
  • Nociception (pain perception)
37
Q

Name some stressors to the body that can result in blood parameters moving outside normal ranges

A
  • Excessive cold or heat
  • Environmental toxins
  • Trauma or injuries
  • Infection
  • Strong emotions
38
Q

Name and briefly describe the 3 parts of the General Adaptation Syndrome (GAS), including the speed of each response, the systems and tissue involved, and the general outcomes of each. With the Resistance response, which 3 of the 5 anterior pituitary hormones are involved, and what the effect is of each?

A

Initial fight-or-flight: Sympathetic outflow is driven by the hypothalamus to mobilize the body
- Short-lived

Resistance reaction: Helps body continue fighting a stressor long after flight-or-fight dissipates
- Longer lasting
- gGH stimulates the liver, skeletal muscles, cartilage, bone, etc. to release IGFs to stimulate lipolysis and glycogenolysis (catabolizing macromolecules to fuel energy-producing metabolism)
- TSH stimulates the thyroids to release T3 and T4 to keep metabolic rates high
- ACTH stimulates the zona fasciculata of the adrenal cortex to release cortisol

Exhaustion: The resistance stage can no longer be sustained
- Wasting of muscle, suppression of the immune system, failure of pancreatic beta cells, pathological change

39
Q

Give a couple of examples of specific diseases associated with the exhaustion & disease state of the GAS

A
  • IBS
  • Asthma
  • Hypertension
  • Anxiety
  • depression

Bio40c (27 decks)

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