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MD2001 > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

What is the endocrine system?

A

+ Second integrative control system of the body

+ Much slower to act than the nervous system

+ Actions are mediated by hormones

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2
Q

What regulatory systems does the endocrine system control?

A

+ Regulation of cellular metabolism
+ Maintenance of homeostasis (e.g. Ca++)
+Sexual development and reproduction
+ Growth and development from childhood to adulthood
+ Modulates long term behaviour (mood, sleep)

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3
Q

How do endocrine glands distribute hormones around the body?

A

They have no ducts so they secrete and release hormones directly into the bloodstream

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4
Q

What are hormones?

A

Hormones are ‘chemical messengers’ that act on target cells through specific receptors

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5
Q

What are the three classes of hormones?

A

+ Proteins
+ Steroids
+ Amino acid derivatives

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6
Q

Where do glands develop from?

A

Epithelial cells

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7
Q

What are exocrine glands?

A

+ Glands with ducts that carry secretions onto the surface of the epithelium

+ E.g salivary, sebaceous, sweat, mammary, glands open onto the skin)

+ Pancreatic duct opens into the duodenum

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8
Q

What are endocrine glands?

A

Glands that secrete their products, hormones, directly into the bloodstream rather than through ducts

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9
Q

What is paracrine secretion?

A

+ Paracrine factors (polypeptides) diffuse over short distances

+ Involves cell-cell communication: inducing changes in adjacent cells (e.g peptide neurotransmitters)

+ Important in embryogenesis where gradients of polypeptides influence developmental change

  • fibroblast growth factor (FGF) family
  • hedgehog family (sonic hedgehog)
  • WnT family
  • TGF-β superfamily
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10
Q

What are the major glands of the endocrine system?

A 
\+ Hypothalamus
\+ Pineal
\+ Pituitary
\+ Thyroid
\+ Parathyroid
\+ Thalamus
\+ Adrenal
\+ Pancreas
\+ Ovaries
\+ Testes
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11
Q

What are the features of hormones in the blood?

A

+ Very low concentrations

+ Concentrations vary (e.g episodic, diurnal)
- important when measuring plasma levels

+ Steroid and thyroid hormones are transported in the blood by specific carrier/binder proteins

  • improves solubility
  • increases half life
  • provides a reserve in the blood

+ Only free hormones are biologically active

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12
Q

What are the conditions associated with the mechanisms of action?

A

+ All hormones act by binding to receptors

+ Target cells must present receptors ( lock and key)

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13
Q

Name types of cell membrane receptors

A

+ Peptides
+ Glycoproteins
+ Catecholamines

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14
Q

Name types of intracellular receptors in the nucleus

A

+ Steroids

+ Thyroid hormones

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15
Q

What are protein hormones?

A

+ Chains of amino acids

+ Usually injected

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16
Q

What are steroid hormones?

A

+ Synthesised from cholesterol

+ Oral administration

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17
Q

What are amino acid derivative hormones?

A

+ Thyroid hormones

+ Catecholamines (adrenalin, dopamine, noradrenalin)

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18
Q

From where does the anterior pituitary develop?

A

The epithelium of the mouth

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19
Q

How does the posterior pituitary develop?

A

It is a down growth of the hypothalamus (consists of nerve fibres)

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20
Q

What is endocrine axes/cascade?

A

When the target tissue of one hormone is another endocrine gland; this allows amplification and fine control

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21
Q

Generally, what does the hypothalamus do?

A

Secrete hormones that control the secretion and release of pituitary hormones

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22
Q

Generally, what do pituitary hormones do?

A

Stimulate/control many other endocrine glands (thyroid, gonads etc)

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23
Q

What is the function of the hypothalamus gland?

A

+ Controls the release of anterior pituitary hormones via releasing hormones (prolactin is controlled by a hypothalamic inhibiting factor)

+ Also secretes hormones stored and released by the posterior lobe of the pituitary gland (oxytocin and ADH)

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24
Q

What is another name for the anterior lobe of the pituitary gland?

A

Adenohypophysis

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25
Q

What does the anterior lobe of the pituitary gland consist of?

A

Epithelial cells

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26
Q

What 6 hormones does the anterior lobe of the pituitary gland secrete?

A 
\+ Growth hormone (GH)
\+ Thyroid stimulating hormone (TSH)
\+ Adrenocorticotropic hormone (ACTH)
\+ Follicle stimulating hormone (FSH)
\+ Luteinising hormone (LH)
\+ Prolactin
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27
Q

Where does TSH target in the body?

A

Thyroid

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28
Q

Where does prolactin target in the body?

A

The mammary glands

29
Q

Where does ACTH target in the body?

A

Adrenoglands

30
Q

Where do LH and FSH target in the body?

A

Ovaries and Testes

31
Q

What is another name for the posterior lobe of the pituitary gland?

A

Neurohypophysis

32
Q

What does the posterior lobe of the pituitary gland consist of?

A

Neural tissue

33
Q

What is the function of the posterior lobe of the pituitary gland?

A

+ Stores hormones secreted by neurosecretory cells in the hypothalamus, which are transported via neuronal axons in the stalk to posterior lobe of the pituitary

Hormones released:

+ Antidiuretic hormone (ADH) (aka Vasopressin)
+ Oxytocin

34
Q

What is ADH also known as?

A

Vasopressin

35
Q

Where does ADH target in the body?

A

The kidneys

36
Q

Where does oxytocin target in the body?

A

Breast tissue and uterus

37
Q

Describe the sequence of events of the hypothalamo-hypophyseal-gonadal axis

A

+ Hypothalamus secretes GnRH

+ GnRH stimulates secretion of pituitary FSH (and LH?)

+ FSH stimulates the gonad to secrete oestrogen or testosterone

38
Q

What is the concept of negative feedback regarding the endocrine system?

A

+ The final product of a cascade acts to inhibit a hormone higher up in the cascade

+ The hypothalamus is an important site of negative feedback in many hormone systems

39
Q

What are pituitary adenomas?

A

+ Common benign tumours of the pituitary gland

+ Some tumours secrete one or more hormones in excess

40
Q

Where does the thyroid gland lie?

A

Anterior to the trachea in the neck

41
Q

How does the thyroid glands develop?

A

It is a down growth of the epithelium of the tongue (leaves a pit at the back of the tongue - foramen caecum)

42
Q

What hormones are secreted by follicular cells in the thyroid?

A

+ Tri-iodothyronine (T3)

+Thyroxine (T4) - requires iodine

43
Q

Where are Tri-iodothyronine (T3) and Thyroxine (T4) stored?

A

The colloid

44
Q

What does thyroxine regulate?

A

+ Energy use; rate of metabolism

+ Protein production; growth and development

+ Regulates sensitivity of cells to other hormones

45
Q

What do parafollicular (aka C) cells produce?

A

Calcitonin

46
Q

What does calcitonin regulate?

A

It regulates calcium homeostasis and stimulates osteoblasts

47
Q

From where does the parathyroid gland develop?

A

The wall of the pharynx

48
Q

Where is the parathyroid found?

A

+ Embedded in the posterior aspect of the thyroid

+ Two pairs of glands

49
Q

What does the parathyroid produce?

A

Parathyroid hormone

50
Q

What does parathyroid hormone regulate?

A

Calcium homeostasis - stimulates osteoclasts to breakdown bone matrix and therefore increases blood calcium levels

51
Q

What two regions form the adrenal glands?

A

+ Cortex (outside)

+ (Adrenal) medulla (inside)

52
Q

What are the three layers of epithelial cells that form the cortex?

A

+ Zona glomerulosa
+ Zona fasciculata
+ Zona reticularis

53
Q

What cells form the (adrenal) medulla?

A

Neural crest cells - neuroectoderm

54
Q

What does the adrenal cortex produce?

A

Steroid hormones

55
Q

What does the adrenal cortex develop from?

A

It develops from the mesoderm of the posterior abdominal wall

56
Q

What (steroid) hormones does the zona glomerulosa produce and secrete?

A

Mineralocorticoids - e.g Aldosterone

57
Q

What (steroid) hormones does the zona fasciculata produce and secrete?

A

Glucocorticoids - e.g Cortisone

58
Q

What (steroid) hormones does the zona reticularis produce and secrete?

A

Sex steroids - e.g Androgens

59
Q

What type of cells does the adrenal medulla contain?

A

Chromaffin cells

60
Q

What do the chromaffin cells in the adrenal medulla produce?

A

Catecholamines:

+ Epinephrine
+ Norepinephrine
+ Dopamine

61
Q

What does the adrenal medulla have a direct connection with?

A

The sympathetic nervous system (controlling our fight/flight response)

62
Q

What kind of gland is the pancreas?

A

Exocrine and endocrine

63
Q

How does the pancreas develop?

A

+ As an out growth of the gut tube

+ Closely associated with the development of the gall bladder

64
Q

What forms the exocrine component of the pancreas?

A

Pancreatic acini

65
Q

What do the pancreatic acini produce?

A

Pancreatic amylase

66
Q

What forms the endocrine component of the pancreas?

A

The islets of Langerhans

67
Q

What do the islets of Langerhans produce?

A

+ Glucagon (alpha cells)

+ Insulin (beta cells)

68
Q

What hormone does the GI tract produce?

A

Gastrin

69
Q

What hormone do the kidneys produce?

A

Renin

MD2001 (52 decks)

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