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Human Physiology > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

What is a Hormone?

A

A chemical messenger secreted directly into blood stream from endocrine gland

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2
Q

What are the four types of intercellular messengers in the body?

A

1) Endocrine
2) Autocrine and Paracrine
3) Neuroendocrine
4) Neurotransmitter

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3
Q

What are the different types of hormones?

A

-Peptide hormones (chains of amino acids)
-Steroid hormones
(derived from cholesterol)
-Hormones derived from tyrosine

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4
Q

How are peptide hormones synthesised?

A

Similar to normal protein synthesis
Preprohormone = The result of the peptide forming after ribosome
Prohormone = The hormone in the golgo complex where it is packaged into the finished product
Hormone = a secretory granule that is stored until released upon arrival of a stimulus, then leaves the cell by exocytosis

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5
Q

How are steroid hormones synthesised?

A

A cholesterol-based precursor molecule is bound to a biosynthetic enzyme which breaks down the substrate into a hormone that is NOT STORED and is released by simple diffusion
-These hormones bind to plasma proteins in the blood

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6
Q

What is the half life?

A

The time taken for the initial concentration to fall by 50%

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7
Q

What are some differences between peptide and steroid hormones?

A

Peptide Hormones:

  • Hydrophilic
  • Free Hormones so biologically active
  • Half life is a few minutes

Steroid hormones

  • Lipophobic
  • Bound to plasma proteins
  • Half life can be hours or days
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8
Q

How does peptide hormone action occur?

A

Hormone binds to a receptor on cell membrane. This then activates G Proteins and Effectors
-This then leads to signal transduction which produces a physiological response such as altered activity of enzymes or ion channels

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9
Q

How does steroid hormone action occur?

A

Hormone binds to Cytosolic receptor or Nuclear receptor to eventually increase or decrease gene expression

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10
Q

How are hormones metabolised?

A

Most hormones are metabolised by enzymes in liver, kidney and/or blood

  • Small proportion by target tissues
  • Small proportion made by target tissues
  • Eventually excreted in urine and/or faeces
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11
Q

How are the release of hormones regulated?

A

1) Feedback regulation
- Negative feedback (consequence negatively controls process)
- Positive feedback (consequence enhances or amplifies process further)

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12
Q

What is the endocrine axis?

A

Interactions between the hypothalamus, the pituitary and peripheral endocrine glands showing feedback regulation

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13
Q

What are some endocrine disorders?

A

1) Hormone excess (hypersecretion)
2) Lack of hormone (hyposecretion)
3) Decreased target-cell responsiveness

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14
Q

How to treat certain hormone disorders?

A

If hormone deficiency - hormone replacement
If hormone excess - drugs to block production
If decreased target-cell responsiveness - drugs to enhance cellular response to hormone
If tumour - radiotherapy or surgery

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15
Q

What are the primary endocrine organs?

A

Hypothalamus (Brain)
Pituitary (Brain)
Pineal (Brain)
Thyroid (Throat)

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16
Q

What is the order of the endocrine axis?

A
  • Hypothalamus
  • Releasing hormone
  • Anterior pituitary
  • Tropic hormone
  • Peripheral endocrine gland
  • Peripheral hormone
  • Target cell response
17
Q

What hormones are made and what to do they do within the body?

A
  • Gonadotropin-releasing hormone (Sex Hormones)
  • Growth hormone (IGF-1)
  • Thyrotropin-releasing hormone (Thyroid hormone)
  • Dopamine/prolactin (Breast tissue)
  • Corticotropin-releasing hormone (Cortisol)
18
Q

What occurs in the Posterior pituitary?

A
  • Neuroendocrine cells synthesise vasopressin and oxytocin

- Hormones are transported along the neurons, stored in the axon termini, in the posterior pituitary

19
Q

What does Vasopressin do?

A
  • Vasoconstriction in Blood Vessels

- Kidney to increase permeability and reabsorption of water

20
Q

What is Oxytocin released by?

A

Release stimulated by suckling, and by cervical stimulation

21
Q

What are the actions of Oxytocin?

A
  • Stimulate ‘milk let-down’, expression of breast milk
  • Uterine smooth muscle contraction
  • Maternal behaviour / sexual behaviour / social bonding
22
Q

What does the pineal gland secrete?

A

Melatonin

23
Q

What is melatonin involved in?

A

Melatonin is involved in control of the body’s circadian rhythm in synchrony with the light-dark cycle

  • Promotion of sleep
  • Seasonal fluctuations of melatonin are important triggers for seasonal breeding, migration and hibernation
24
Q

What do the thyroid glands secrete?

A
  • Thyroxine (T4)
  • Tri-iodothyronine (T3) Calcitonin

Most of T4 is converted to T3 in the periphery
-most actions of thyroid hormones are by T3

25
Q

What are the actions of the Thyroid Hormones?

A
  • Increase metabolism in the body
  • Stimulate growth and development
  • Calcitonin
26
Q

What are the other Primary Endocrine Organs?

A
  • Parathyroid
  • Adrenal cortex and medulla
  • Endocrine pancreas
  • Gonads
27
Q

What is parathyroid hormone?

A

-secreted by the parathyroid hormones

Acts to increase plasma Ca2+ levels, opposing effects of calcitonin

28
Q

What is released by the Adrenal gland?

A

Catecholamines (from the adrenal medulla):

  • Adrenaline
  • Noradrenaline

Adrenal Steroid Hormones (from the adrenal cortex):

  • Mineralocorticoids (Aldosterone)
  • Glucocorticoids
  • Weak androgens
29
Q

What is released in the Pancreas?

A

Exocrine:
-Digestive enzymes to further break down carbohydrates, proteins and lipids in the chyme

Endocrine:
-Islets of langerhans (glucose homeostasis)

30
Q

What are the Islets of Langerhans?

A

Endocrine cells in clusters, scattered throughout the pancreas
-only 1-2% of the total pancreatic mass but receive 10% of blood supply

31
Q

What are the different types of Islet cells?

A

alpha - glucagon (30-40% of human islate cells)
beta - insulin (50-60%)
delta - somatostatin (5-10%)

32
Q

What is insulin? main role?

A

A peptide hormone that is the main physiological regulator in blood glucose levels
-Promote growth and development

33
Q

What is glucagon? main role?

A

Peptide hormone that is stimulated by low blood glucose

-opposite actions of those to insulin

34
Q

What are synergistic hormones?

A

Hormones that produce much greater response than sum of the effects of the individual hormones

35
Q

What are permissive hormones?

A

Presence of one hormone allows a second hormone to act

36
Q

What are antagonistic hormones?

A

Effects of hormones oppose each other

Human Physiology (29 decks)

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