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physio 1020 > module 13 first half: endocrinology > Flashcards

module 13 first half: endocrinology Flashcards

1
Q

what is homeostasis and how is it maintained in the body?

A

The process by which conditions inside the body are maintained at constant levels
- it’s maintained by the nervous system and the endocrine system

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2
Q

what are the functions of the endocrine system

A
  • maintenance of the internal environment (body temp, body fluid, volume, osmolality)
  • adaptation to stress
  • control of growth and metabolism
  • control of reproduction
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3
Q

differences between endocrine system and nervous system actions

A

endocrine system indirectly affects many organs at a distance by secreting hormones into the blood
- slower to take effect
- last longer and are more widespread within the body

nervous system has direct contact over organs through synapse
- faster to take effect

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4
Q

glands - what is the endocrine gland, how does it work

A

a group of specialized cells that synthesize, store, and release a special chemical (hormones) into the blood

  • hormone goes into the blood stream and circulates to specific target cells that have receptors for the hormone
  • hormone will have it’s effect and can either stimulate or inhibit the activity of the cell
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5
Q

list all the glands in the body

A
  • hypothalamus
  • pituitary glands
  • thyroid gland
  • adrenal glands
  • pancreas
  • gonads (ovaries/testes)
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6
Q

three categories of hormones

A
  1. hormones derived from the amino acid tyrosine (thyroxine, triiodothyronine)
    - secreted from the thyroid gland
  2. hormones derived from proteins
    - calcitonin, parathyroid hormone, pituitary and pancreatic hormones, and most releasing/inhibiting hormones from the hypothalamus
  3. steroid hormones
    - cortisol, aldosterone, estrogen, progesterone, testosterone, all derived from cholesterol
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7
Q

protein hormones - hydrophilic/hydrophobic?, receptor location?, movement through the blood?

A

protein hormones are hydrophilic
- they can circulate freely in the blood
- they cannot diffuse through the cell membrane
- the receptor is located on the cell membrane

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8
Q

steroid and thyroid hormones - hydrophilic/hydrophobic?, receptor location?, movement through blood?

A

steroid and thyroid hormones are hydrophobic
- they require a protein carrier to help them circulate in the blood
- they can diffuse through the cell membrane
- the receptor is located inside the target cell

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9
Q

hormones - characteristic of how they are secreted in the blood and what their special effects do

A

hormones are secreted into the blood in “pulses”
- by a specific stimulus and in amounts that vary with the strength of the stimulus
- their special effects regulate preexisting reactions

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10
Q

what is a hormone receptor? what triggers the response from the cell?

A

structure in or on a cell that interacts with a chemical (the hormone) in a particular way
- type of hormone determines where the receptor is located
- interaction between receptor and hormone triggers a response from the cell

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11
Q

explain the process of receptors for hydrophobic hormones

A
  • hormone first released by its carrier protein
  • receptors are located in the cytoplasm or on the nucleus
  • once hormone is inside the cell, it will bind with the receptor
  • this new hormone/receptor complex binds to the DNA within the nucleus to alter activities of the cell:
  • increase/decrease transcription of specific genes (altering production of downstream proteins)
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12
Q

explain the process of receptors for hydrophilic hormones

A
  • hormone must alter activity of the cell from the “outside”
  • receptors are located on the cell membrane
  • when hormone attaches to the receptor, it initiates a sequence of chemical reactions that will alter cell activity
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13
Q

what are the 3 ways the receptor in a hydrophilic hormone can affect the cell

A
  1. second messenger system
  2. tyrosine kinase
  3. G - proteins
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14
Q

explain the process of the second messenger system

A
  1. Hormone receptor complex causes a G - protein on the inside of the cell produces a second messenger
    - most widely studies second messenger is called cyclic adenosine monophosphate (cAMP)
  2. Second messenger is released into the cytoplasm and rapidly alters proteins present inside the cell
  3. These altered proteins trigger a sequence of reactions inside the cell
    - leads to a variety of intracellular responses (such as protein release)
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15
Q

explain the process of tyrosine kinase

A
  1. Hormone receptor complex activates tyrosine kinase on the inside surface of the membrane
  2. Intracellular tyrosine kinase alters existing proteins that will alter the activity of the cell
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16
Q

explain the process of ion channels

A
  1. Hormone receptor complex activates a G - protein that lies within the cell membrane
  2. This G- protein can open adjacent ion channels
  3. If the ion is Ca++, it acts as a second messenger, altering existing proteins once it diffuses into the cell
17
Q

what happens after hormones have had their effects on their target tissue

A

hormones are broken down by different systems in the body
1. Metabolic destruction
- in the blood or by tissues (mainly liver and kidneys)
2. Excretion by the liver
- into the bile
3. Excretion by the kidneys
- into the urine

18
Q

how is the secretion of hormones controlled

A

through negative feedback loops

19
Q

where is the hypothalamus located?

what type of information from the body does it receive?

what does the hypothalamus regulate in the body (homeostatic & behavioural)

A

located at the base of the brain, above the pituitary gland and below the thalamus
- it receives informations from all over the body
- composed of regions made up of nerve cell bodies (nuclei), several of these nuclei control the release of hormones from the pituitary gland

involved with the body’s homeostatic mechanisms, including regulation of:
- body temperature, water balance, energy production

involved in regulating the behavioural drives of:
- thirst
- hunger
- sexual behaviour

to perform these actions, the hypothalamus receives lots of information from all around the body including:
- metabolic, hormonal, temperature, and neural information

20
Q

list all the hormones the hypothalamus secretes and what they cause

A
  • prolactin inhibiting hormone (PIH)
  • prolactin releasing hormone (PRH)
  • thyrotropin releasing hormone (TRH)
  • corticotropin releasing hormone (CRH)
  • growth hormone releasing hormone (GHRH)
  • growth hormone inhibiting hormone (GHIH)
  • gonadotropin releasing hormone (GnRH)

these are referred to as inhibiting/releasing hormones because they cause the release or inhibition of a hormone from the anterior pituitary gland

21
Q

explain the pituitary gland structure

anterior pituitary: what it’s made of, its function, how its regulated, how the hypothalamus and pituitary work together

A

the pituitary gland is divided into two regions:
- anterior pituitary
- posterior pituitary

anterior pituitary is made up of endocrine tissue
- these cells secrete pituitary hormones directly into the blood
- regulated by the hypothalamus through a special circulatory system, the hypothalamic-hypophyseal portal system

the hypothalamus communicates with the anterior pituitary by secreting the releasing or inhibiting hormones into the portal system
- these hormones travel to the anterior pituitary to either stimulate or inhibit the release of pituitary hormones

22
Q

what is the posterior pituitary made of, it’s function, hormones released (what is the tract called)

A

the posterior pituitary develops from neural tissue at the base of the brain
- it contains axons and nerve terminals of neurons whose cell bodies lie in the hypothalamus
- this tract is referred to as the hypothalamic hypophyseal tract

these neurons produce neurohormones (ADH and oxytocin) in the hypothalamus that are secreted into the blood in response to action potentials

23
Q

anterior pituitary hormones result of thyrotropin releasing hormone (TRH)

A

causes the release of thyroid stimulating hormone (TSH)
- TSH then stimulates the thyroid gland to secrete two thyroid hormones
- triiodothyronine (T3)
- thyroxine (T4)

24
Q

anterior pituitary hormones result of corticotropin releasing hormone (CRH)

A

stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
- ACTH then stimulates the adrenal glands to secrete mainly cortisol
- ACTH has a minor affect in the secretion of adrenal androgens and aldosterone as well

25
Q

anterior pituitary hormones - growth hormone (released by anterior pituitary)

A

under control of two hypothalamic hormones:
- growth hormone releasing hormone (GHRH)
- growth hormone inhibiting hormone (GHIH/somatostatin)

the primary stimulus for GH release is GHRH, GHIH has a weak effect on GH

26
Q

anterior pituitary hormones result of gonadotropin releasing hormone (GnRH)

A

stimulates the anterior pituitary to secrete:
- luteinizing hormone (LH)
- follicle stimulating hormone (FSH)
both of these act on the testes or ovaries

27
Q

anterior pituitary hormones - Prolactin (PRL) (released by anterior pituitary)

A

under control of two hypothalamic hormones:
- prolactin releasing hormone (PRL)
- prolactin inhibiting hormone (PIH)
PIH has the strongest effect over prolactin secretion

28
Q

list the posterior pituitary hormones and their function

A

hormones are are secreted into the blood in response to action potentials:
- antidiuretic hormone (ADH/Vasopressin): regulates water reabsorption in the kidney
- oxytocin: regulates milk release from breast and causes the contraction of the uterus during labour

29
Q

regulation of hormones by negative feedback: 3 loops

A

hypothalamus secretes a releasing hormone (H1), which causes the releasing of anterior pituitary hormone (H2) into the blood
- H2 can feed back to the hypothalamus to decrease the release of H1 in a “short loop” negative feedback system

the anterior pituitary hormone (H2) will circulate to an endocrine gland to cause the release of another hormone (H3)
- H3 can feed back to the hypothalamus and pituitary to decrease the release of H1 and H2 by a “long loop” negative feedback system

hormone from endocrine gland (H3) can also affect one or more tissues
- target tissues can feed back to the hypothalamus and can decrease the release of its hormone (H1) in an “ultra long loop” reflex

30
Q

structure of the thyroid gland, cells within it

A

located directly below the larynx and consists of two lobes that almost completely surround the trachea

the thyroid is made up of follicles, functional units of the gland
- these follicles consist of a central region of colloid surrounded by epithelial cells
- between the follicles are parafollicular cells (C cells)

31
Q

function of the thyroid gland, hormones’ roles in the body, hormone produced by follicular cells

A

produces thyroid hormones
- triiodothyronine (T3)
- thyroxine (T4)
these hormones contain iodine, responsible for regulating basal metabolic rate (BMR)

the follicular cells produce the protein hormone calcitonin which decreases calcium levels in the blood

32
Q

describe the production of T3 and T4

A

both T3 and T4 are produced inside the follicles of the thyroid gland by: combining iodine and tyrosine with the help of a glycoprotein called thyroglobulin

  1. epithelial cells take up molecules of tyrosine from circulation and combine with thyroglobulin which is produced within the epithelial cells
  2. epithelial cells take up iodine, absorbed from the diets
  3. tyrosine-thyroglobulin complex is secreted into the colloid, 1 or 2 molecules of iodine attach to each tyrosine
  4. in the colloid, 2 tyrosine molecules join together while attached to the thyroglobulin
  5. the number of iodine molecules attached to the tyrosine will produce either
    - T3 (3 iodine)
    - T4 (4 iodine)
33
Q

describe the secretion of T3 and T4

A

thyroid stimulating hormone (TSH) released from the anterior pituitary gland, will bind to a receptor on the membrane of the epithelial cell, will stimulate different reactions:
1. trapping and taking up circulating iodine to form hormones
2. stimulating endocytosis of the T3-andT4-thyroglobulin complex into the cells from the colloid
3. enzymatic removal of thyroglobulin from T3 and T4 in the epithelial cells and stimulating the secretion of T3 and T4 into the blood
4. stimulates the thyroid to grow a process called hyperplasia

34
Q

circulation of T3 and T4, which is secreted more in the blood, which is more active

A

hormones released from the thyroid gland consist of:
- 90% thyroxine (T4)
- 10% triiodothyronine (T3)

even though thyroid secretes mostly T4, much of it is converted to T3
- T3 is the more biologically active of the 2 hormones

35
Q

regulation of secretion - T3 and T4 (feedback loop)

A

hormones T3 and T4 will feedback to the hypothalamus and pituitary to inhibit the release of thyrotropin releasing hormone (TRH) and thyroid stimulating hormone (TSH)
- with less TSH circulating to the thyroid less T3 and T4 will be released

36
Q

What is basal metabolic rate (BMR), explain three roles of T3 and T4

A

Basal Metabolic Rate (BMR): the amount of oxygen and energy the body is using at rest, or essentially the least amount of energy a person will use

roles of T3 and T4:
1. regulating BMR
2. proper development of the nervous system in the fetus
3. maintain a person’s alertness, responsiveness, emotional state

37
Q

thyroid gland disease - Goiter, what is it, 2 main causes

A

results in the enlargement of the thyroid gland

two main causes:
1. too much thyrotropin releasing hormone (TRH) and/or thyroid stimulating hormone (TSH) being produced:
- hypothalamic tumour causes excess secretion of TRH and TSH
- excess TRH and TSH will produce large amounts of thyroid hormone, BUT excess TSH will make the thyroid grow

  1. insufficient iodine in the diet:
    - without iodine in the blood, thyronine will be unable to produce T3 and T4
    - in absence, NO negative feedback to hypothalamus and pituitary; continues to secrete TRH and TSH
    - excess TSH will cause thyroid growth
38
Q

calcitonin’s function in the body, 2 ways it functions

A

a protein hormone secreted by the parafollicular cells (C cells) of the thyroid gland
- calcitonin helps regulate calcium levels in the blood

calcitonin is secreted when blood calcium levels rise above normal, it decreases levels of Ca++ levels by:

  1. decreasing number and activity of special bone-dissolving cells called osteoclasts
    - these cells breakdown bone into calcium that is then released into the blood
  2. calcitonin also stimulates the secretion of calcium into the urine, decreasing blood calcium levels

in order to maintain relatively constant blood calcium levels, calcitonin works with parathyroid hormone (PTH)

39
Q

parathyroid gland location, what hormone they secrete, function of the hormone (2 ways)

A

parathyroid glands are located on the posterior side of the thyroid
- they secrete parathyroid hormone (PTH) when blood calcium levels are low
- PTH will raise blood calcium levels when they are too low by:

  1. increasing the number and activity of the bone-dissolving osteoclast cells, which will release calcium into the blood
  2. decreasing the excretion of calcium in the urine by reabsorbing it out of the filtrate

without PTH, the kidneys would continually excrete calcium, this would eventually deplete extracellular fluid and bones of this mineral

NOTE: OPPOSITE OF CALCITONIN

physio 1020 (5 decks)

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