Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Metabolism > Endocrine System > Flashcards

Endocrine System Flashcards

0
Q

What is paracrine control?

A

When hormones are released locally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Describe the method of secretion of insulin in response to a rise in blood glucose concentration.

A

A rise in blood glucose concentration in the capillaries bathing the Islets of Langerhans leads to increased uptake of glucose via GLUT2 receptors. The glucose undergoes glycolysis and leads to an increased intracellular concentration of ATP. ATP binds ATP sensitive potassium channels and they close. Potassium cannot leave the cell and the membrane is depolarised, causing voltage gated calcium channels to open and calcium floods into the cell. This causes the excretion by exocytosis of insulin containing secretory granules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is autocrine control?

A

When a substance is released and has an effect on the releasing cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define the afferent and efferent branches of the peripheral nervous system

A

The afferent carries signals towards the brain from sensory input.
The efferent carries signals away from the brain to an effector organ.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where is the thyroid gland located?

A

In the neck in front of the lower larynx and upper trachea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What nerves lie close to the thyroid gland, and what are they involved in. What implications does this have for thyroidectomy

A

Recurrent laryngeal and the external branch of the superior laryngeal. They are involved in speech and must be avoided during surgery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How many arteries supply the thyroid gland? How many veins drain the thyroid gland? What are their names?

A

Three.

Superior, middle and inferior thyroid arteries and veins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

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

A

Follicular cells and parafollicular cells (C-cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the structure of the thyroid gland?

A

It is a butterfly shaped gland with two lateral lobes joined by a central isthmus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the approximate size and weight of the thyroid gland?

A

2-3cm, 15-20g in a healthy person.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How are the follicular cells arranged in the thyroid gland?

A

Into spherical follicles, they make up the epithelial lining of the follicles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where are parafollicular cells found in the thyroid gland?

A

The connective tissue surrounding the follicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What hormones are produced by the thyroid gland, what class of hormone are they and how are they derived?

A

Thyroxine (T4) is an amino acid derivative hormone from tyrosine.
Triiodothyronine (T3) is also an amino acid derivative hormone from tyrosine.
Calcitonin is a polypeptide hormone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the process by which iodine is taken up into the follicular cells of the thyroid gland, and its initial fate.

A
  1. Iodine uptake. Sodium is actively transported out of the follicular cells across the basal plasmalemma (cells are polarised). Iodine is then taken up into the cell against its concentration gradient via a cotransporter, along with sodium which is diffusing down its concentration gradient. Iodine moves across the apical membrane not the colloid. It is then activated by a peroxidase enzyme, (iodide ➡️ iodine, catalysed by thyroperoxidase) and it reacts with thyroglobulin, which is a protein rich in tyrosine.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Outline the synthesis of thyroglobulin.

A

Thyroglobulin is synthesised by ribosomes, glycosylated in the ER then transported to the Golgi and packaged into secretory vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are T3 and T4 secreted?

A

Thyroglobulin is taken into the epithelial cells from the lumen of the follicle by endocytosis. Is is then cleaved to give T3 and T4, which diffuse into the circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Classify the epithelia of the follicles of the thyroid.

A

Simple columnar or simple cuboidal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where is thyrotropin releasing hormone (TRH) released from?

A

Dorsomedial nucleus of hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What type of hormone is TRH?

A

Polypeptide (tripeptide)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What stimulates the release of TRH?

A

Decreased levels of T3 and T4.
Stress.
Fall in temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the destination of TRH, how does it get there, and what effect does it have?

A

The anterior pituitary, via the hypothalamic/pituitary portal system.
Stimulates the release of TSH (thyroid stimulating hormone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What class of hormone is TSH?

A

Glycoprotein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the structure of TSH

A

Consists of two non covalently linked subunits (alpha and beta)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

In what pattern is TSH released?

A

Diurnal rhythm, higher in the night and decreasing in the early hours of the morning. Not very pronounced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What effect does TSH have on the follicle cells of the thyroid?

A

Stimulates synthesis and secretion of T3 and T4
Increases vascularisation of thyroid gland and causes an increase in the size and number of follicle cells. Leading to a larger thyroid gland perceived as a goitre.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Explain the relationship between MIT, DIT, T3 and T4

A

MIT is monoiodotyrosine. DIT is diiodotyrosine. T3 is triiodothyronine. T4 is tetraiodothyronine.
Two molecules of DIT combine to form T4.
T4 can be deiodinated in the tissues to T3.
MIT and DIT combine to form r-T3 or T3

26
Q

Name three proteins that bind T3 and T4 so that they can be transported in the blood.

A

Albumin, pre-albumin, thyronine binding globulin.

27
Q

Which of the hormones has a lower affinity for binding proteins, meaning a greater proportion of it is free?
What are the consequences of being free on being active?
What are the consequences on half life?

A

T3 has a lower affinity for transport proteins so a lower proportion is bound.
It is the free hormone that is biologically active.
T3 has a shorter half life (2 days compared to 8 days)

28
Q

What is the impact of an increase in oestrogen synthesis on the levels of thyroid hormone (for example during pregnancy)

A

Oestrogen increases synthesis of thyronine binding globulin (TBG)
This means a greater proportion of T3 and T4 are bound.
This means negative feedback on TRH and TSH is reduced, so more TSH is produced and production of T3 and T4 increases, so the free concentration of T3 and T4 is normal but there is more bound.

29
Q

What are the major physiological actions of T3 and T4, on the metabolic activity of most tissues?

A

Increase metabolic rate (BMR)
Stimulate glucose uptake and metabolism.
Stimulate mobilisation and oxidation of fatty acids.
Stimulate protein metabolism
Overall leads to an increase in BMR, heat production and oxygen consumption (catabolic)

30
Q

What is the role of thyroxine in the menstrual cycle?

A

Permissive role on the actions of FSH and LH, ovulation cannot occur in the absence of thyroxine.

31
Q

Why is thyroxine necessary for growth?

A

Increase in metabolic rate
Increase synthesis of heart muscle protein
Directly affect bone mineralisation

32
Q

What is the mechanism of action of T3 and T4

A

They cross the plasma membrane and interact with proteins in the nucleus (and possibly mitochondria)
T3 has a much higher affinity than T4. It binds the hormone binding domain which produces a conformational change in the DNA binding domain of the protein.
This increases the transcription of specific genes that have a role in metabolism.

33
Q

Explain how T4 is converted to T3 and r-T3.

A

T4 to T3 by removal of the 5’ iodide
T4 to r-T3 by removal of the 3’ iodide
r-T3 is inactive but binds T3 receptors, blocks the effect of T3

34
Q

What is the most common form of hypothyroidism, and what are the two ways in which it can reduce thyroid function?

A

Hashimotos’s disease.
Either autoimmune destruction of thyroid follicles.
Or the production of an antibody that binds TSH receptors preventing follicles from responding to TSH.

35
Q

What is the treatment for hypothyroidism?

A

Oral thyroxine

36
Q

If someone had hypothyroidism, what would you expect their TSH and free T4 levels to be?

A

High TSH, low free T4.

37
Q

What proportion of the population are affected by Hashimotos’ disease?

A

Roughly 1%, mostly women

38
Q

What is Graves’ disease?

A

Autoimmune hyperthyroidism. Antibodies are produced that stimulate TSH receptors on thyroid follicles

39
Q

What is a common drug treatment for hyperthyroidism, and what is its mechanism of action?

A

Carbimazole.

It inhibits thyroid peroxidase and therefore prevents the coupling of thyroglobulin with iodine.

40
Q

What are the signs and symptoms of hypothyroidism? 8 answers.

A 
Bradycardia
Weight gain
Tiredness and lethargy
Hair loss
Deep and husky voice
Cold intolerance and reduced BMR
Muscle cramps, ataxia, weakness
Skin dry and flaky.
41
Q

What are the signs and symptoms of hyperthyroidism? 7 answers.

A

Tachycardia
Weight loss
Heat intolerance, raised BMR, increased oxygen consumption
Intestinal hypermobility
Skeletal and cardiac myopathy leading to tiredness, weakness and breathlessness
Osteoporosis
Mental and physical hyperactivity

42
Q

What is cretinism

A

Hypothyroidism in the neonatal period resulting in poor mental development, broad features and slow growth, as thyroid is necessary for development of nervous system - myelination, development of cellular processes of nerve cells and hyperplasia of cortical neurons.

43
Q

Which part of the brain is involved in controlling ventilation and the cardiovascular system?

A

Medulla

44
Q

What are the receptors in the body?

A

Specialised nerve endings - nociceptors, chemoreceptors, thermoreceptors, proprioreceptors.

45
Q

What is ‘hunting behaviour’ and what does it indicate?

A

The tendency of systems controlled by negative feedback to overshoot the set point several times before coming to rest at the set point - indicates a dynamic equilibrium.

46
Q

Give two examples of systems that use positive feedback.

A

Blood clotting cascade

Ovulation - build up of FSH

47
Q

Where is the ‘biological clock’

A

Suprachiasmatic nucleus in the hypothalamus.

48
Q

What is the natural diurnal cycle of humans, and what keeps us on a 24hr cycle?

A

24hrs 11 minutes

Zeitgeibers - cues from the environment

49
Q

What is the role of melatonin, where is it secreted from?

A

Involved in setting the biological clock

Pineal gland

50
Q

What causes jet lag?

A

Mismatch between environmental keys and biological clock.

51
Q

What water is present in a healthy 70kg man?

A

42l
28l intracellular fluid (35% lean body weight)
9.4l interstitial fluid (12%)
4.6l blood plasma (4-5%)

52
Q

How is the osmolality and sodium ion concentration of blood plasma controlled by ADH?

A

Monitored by osmoreceptors in the supraoptic and paraventricular nuclei of the hypothalamus.
Influence feelings of thirst. If osmolality increases, ADH released from posterior pituitary.
Increases permeability of collecting duct to water, increases reabsorption of water from the kidney, decreases water lost in the urine.

53
Q

What are the four groups of hormones (with examples)

A

Peptide/polypeptide-insulin, glucagon, growth hormone, placental lactogen
Steroid-oestrogen, testosterone, aldosterone, cortisol
Amino acid derivatives - T3 and T4, adrenaline
Glycoproteins - LH, FSH, TSH a

54
Q

How are hormones stored before secretion?

A

Catecholamines and polypeptides are stored in storage vesicles
Steroid hormones are not stored, cholesterol is stored as cholesterol esters.
T3 and T4 are stored extracellularly in a protein colloid

55
Q

How are thyroid hormones carried in the blood?

A

75% bound to thyronine binding globulin
25% bound to albumin
Less than 1% free and biologically active

56
Q

What are the six main hormones secreted by the anterior pituitary?

A

FSH, LH, GH, TSH, ACTH, prolactin

57
Q

What are the releasing or inhibiting hormones, and what is their role?

A

Alter the position of the equilibrium.
Secreted by hypothalamus, act on anterior pituitary.
Thyrotrophin releasing hormone TRH
Corticotrophin releasing hormone CRH
Somatotrophin releasing hormone SRH
Somatostatin (secreted from delta cells of pancreas, inhibits GH release)

58
Q

How do releasing and inhibiting factors travel from hypothalamus to the pituitary gland?

A

Hypophyseal portal vessels

59
Q

How do steroid hormones act on their target cells?

A

Lipid soluble so cross plasma membrane
Binds to a receptor in cytoplasm or nucleus
Binds DNA and alters the rate of transcription of DNA.
Alters the rate of production of proteins/enzymes

60
Q

How do polypeptide hormones cause an effect in their target cells?

A

Bind receptors on the cell surface
Activates second messenger inside the cell
Exerts metabolic effects, often modifies the rate of reaction of enzymes (phosphorylation etc)

61
Q

List five second messengers

A 
cAMP - low energy signal 
gAMP
Calcium ions
Inositol triphosphate IP3
Diacylglycerol DAG
62
Q

HOw are proteins inactivated?

A

In liver and kidneys - steroid hormones are made water soluble and excreted via the urine or bile
Peptide hormones are degraded to amino acids

Metabolism (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions