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Human Physiology > Chapter 23- Endocrine system > Flashcards

Chapter 23- Endocrine system Flashcards

1
Q

What are the two endocrine cell types of the thyroid gland?

A

C cells, secreting calcitonin

Follicular cells secreting thyroid hormones

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2
Q

What are thyroid hormones derived from and why are they unusual?

A

They are derived from tyrosine and are unusual because they contain iodine

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3
Q

What is the structure of the follicular cells of the thryoid like?

A

The follicular cells have a spherical shape with a single layered wall of epithelial cells. It has a hollow center filled with colloid

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4
Q

What does colloid of the follicular cells contain?

A

Colloid contains thyroglobulin and enzymes for thyroid hormone synthesis

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5
Q

What do the thyroid hormones influence?

A

They influence metabolic rate

protein, fat, and carbohydrate metabolism

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6
Q

T3 and T4, which one is the more active and how much more active?

A

T3 is more active, by 3-5 times

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7
Q

How does T3 get made?

A

T4 is converted in the target cell by deiodinases

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8
Q

What are the steps of thyroid hormone synthesis?

A
  • A Na+/I- symporter brings I- into the cell and into the colloid
  • The follicular cell synthesizes enzymes and thyroglobulin for the colloid
  • Thyroid peroxidase adds iodine to tyrosine, making T3 and T4
  • Thyroglobulin is taken back into the cell in vesicles
  • Intracellular enzymes seperate T3 and T4 from the protein
  • T3 and T4 enter into the circulation as free hormones
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9
Q

What does the hormonal pathway regulating thyroid hormones look like? Name the hormone and where it is synthesized/secreted from. Is there a feedback system in place? What is it?

A

TRH- Hypothalamus
TSH- anterior pituitary
T3, T4 - thyroid gland
T3 and T4 provide negative feedback for TSH and TRH

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10
Q

What is the main function of thyroid hormones?

A

To provide substrates for oxidative metabolism

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11
Q

What is goiter?

A

When there are elevated levels of TSH stimulating the thyroid gland. The thyroid enlarges

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12
Q

What is hyperthyroidism? What are symptoms?

A

Hyperthyroidism is when there is an excess of thyroid hormones.
Symptoms include
-increase oxygen consumption and metabolic rate, causing heat production (often warm and sweaty)
- increased muscle protein breakdown causing weightloss
- hyperexcitable reflexes, psychological disturbance
-Rapid heartbeat and increased force of contraction due to effect on B1 adrenergic receptors

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13
Q

What is Graves’ disease? Symptoms?

A

Graves’ disease is a disease in which Thyroid stimulating immunoglobulins (TSI antibodies) act as an agonist on TSH receptors on the thyroid. They experience hyperthyroidism and goiter, as well as bulging eyes

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14
Q

What is hypothyroidism? What are the symptoms?

A

Hypothyroidism is a deficiency of thyroid hormones.
Symptoms include:
- Slowed metabolic rate and oxygen consumption
- decreased protein synthesis
- Slowed heart rate

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15
Q

What is Hashimoto’s thyroiditis? What are symptoms?

A

Hypothyroidism in which the patient experiences weight gain, depression, mania, sensitivity to temperature, and chronic fatigue

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16
Q

Why can hypothyroidism cause clinical depression?

A

T3 is found in synaptic junctions and regulates activity and amounts of serotonin, norepinephrine and GABA in the brain. Insufficient regulation causes chemical imbalance

17
Q

What is the most common cause of primary hypothyrodism?

A

A lack of iodine in the diet. Without iodine, thyroid hormones are not produced

18
Q

What are causes of primary hyperthyroidism? and secondary?

A
  • TSI or thyroid gland tumours

- pituitary tumours secreting TSH

19
Q

How can hypothyroidism result in goiter?

A

In hypothyroidism, absence of negative feedback increases TSH secretion, which means there is more acting on the thyroid, enlarging it

20
Q

What are four functions of Ca2+?

A
  • Act as a signalling molecule (second messenger pathways, muscle contraction, exocytosis)
  • As a part of the glue holding cells together at tight junctions
  • As a cofactor in the coagulation cascade
  • Plasma concentrations of Ca2+ affect neuroexcitability
21
Q

Which three hormones regulate Ca2+ movement between bone, kidney, and intestine?

A

PTH, vitamin D3 (Calcitriol) and calcitonin

22
Q

What are the three ways PTH raises plasma Ca2+?

A
  • PTH mobilizes Ca2+ from the bone pool
  • PTH stimulates retention of Ca2+ in the kidneys
  • Encourages increased intestinal absorption of Ca2+ through acting on vitamin D3
23
Q

What are the three functions of calictriol?

A
  • enhances Ca2+ uptake in the small intestine
  • facilitates renal absorption of Ca2+
  • helps mobilize Ca2+ out of the bone
24
Q

What are the three components of calcium homeostasis?

A
  • Calcium intake through diet absorbed in small intestine
  • Calcium loss through urine and feces
  • Distribution of calcium among ECF (2.5 mM), intracellular (0.001 mM), and bone
25
Q

How is calcitriol (D3) made?

A

D3 is made from vitamin D from diet or from sunlight, which is converted in the liver and the kidneys

26
Q

A patient has low Ca2+, what do we expect to happen with regards to hormones?

A

An increased synthesis of PTH, an increase in D3 synthesis, Ca2+ being reabsorped from the bone, retention in the kidneys, increased uptake in the intestine

27
Q

What does calcitonin do?

A

It is released when plasma Ca2+ is elevated. It decreases bone reabsorption and increases renal excretion of calcium. Plays only a minor role in calcium metabolism

28
Q

What is osteoperosis?

A

A disorder in which bone resorption exceeds bone deposition

29
Q

What is rickets?

A

A disorder of bone growth in children caused by vitamin D deficiency or low Ca2+ intake

30
Q

What are osteoblasts, osteoclasts, and osteocytes?

A

Osteoblasts are the cells that synthesize bone. Osteoclasts reabsorb and break down the bone. Osteocytes are inactive osteoblasts that are highly branched in the bone interior

31
Q

Why is calcitonin a treatment option for Paget’s disease?

A

In paget’s osteoclasts are overactive and bone is weakened by reabsorption. Giving calcitonin lowers the rate of reabsorption of bone

32
Q

What are some roles of phosphate in the body?

A

To form hydroxyapatite together with calcium
Energy transfer and storage
Activiation/deactivation of enzymes, transporters, and ion channels
Part of the DNA and RNA backbone

33
Q

Hydroxyapatite attaches to …………………… support. Calcium provides the bone with ………. while ……….. provides the bone with flexibility

A

Collagenous
Strength
collagen

34
Q

What provides input for PTH stimulation/inhibition?

A

CaSR (Ca2+ sensing receptor) that monitors plasma Ca2+ levels

35
Q

Which risk factors are there for osteoperosis?

A

Women after menopause (absence of estrogen)
Smoking
Low dietary calcium intake
Thin, small body type

36
Q

Osteocytes are linked through their …………………… allowing Calcium and ……………………. exchange between the bone matrix and the blood

A

gap junctions

chemical signal

Human Physiology (5 decks)

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