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Flashcards in Endocrine System Deck (69):
1

What is the endocrine system?

+ Second integrative control system of the body

+ Much slower to act than the nervous system

+ Actions are mediated by hormones

2

What regulatory systems does the endocrine system control?

+ 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)

3

How do endocrine glands distribute hormones around the body?

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

4

What are hormones?

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

5

What are the three classes of hormones?

+ Proteins
+ Steroids
+ Amino acid derivatives

6

Where do glands develop from?

Epithelial cells

7

What are exocrine glands?

+ 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

8

What are endocrine glands?

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

9

What is paracrine secretion?

+ 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

10

What are the major glands of the endocrine system?

+ Hypothalamus
+ Pineal
+ Pituitary
+ Thyroid
+ Parathyroid
+ Thalamus
+ Adrenal
+ Pancreas
+ Ovaries
+ Testes

11

What are the features of hormones in the blood?

+ 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

12

What are the conditions associated with the mechanisms of action?

+ All hormones act by binding to receptors
+ Target cells must present receptors ( lock and key)

13

Name types of cell membrane receptors

+ Peptides
+ Glycoproteins
+ Catecholamines

14

Name types of intracellular receptors in the nucleus

+ Steroids
+ Thyroid hormones

15

What are protein hormones?

+ Chains of amino acids

+ Usually injected

16

What are steroid hormones?

+ Synthesised from cholesterol

+ Oral administration

17

What are amino acid derivative hormones?

+ Thyroid hormones

+ Catecholamines (adrenalin, dopamine, noradrenalin)

18

From where does the anterior pituitary develop?

The epithelium of the mouth

19

How does the posterior pituitary develop?

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

20

What is endocrine axes/cascade?

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

21

Generally, what does the hypothalamus do?

Secrete hormones that control the secretion and release of pituitary hormones

22

Generally, what do pituitary hormones do?

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

23

What is the function of the hypothalamus gland?

+ 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)

24

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

Adenohypophysis

25

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

Epithelial cells

26

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

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

27

Where does TSH target in the body?

Thyroid

28

Where does prolactin target in the body?

The mammary glands

29

Where does ACTH target in the body?

Adrenoglands

30

Where do LH and FSH target in the body?

Ovaries and Testes

31

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

Neurohypophysis

32

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

Neural tissue

33

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

+ 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

What is ADH also known as?

Vasopressin

35

Where does ADH target in the body?

The kidneys

36

Where does oxytocin target in the body?

Breast tissue and uterus

37

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

+ Hypothalamus secretes GnRH

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

+ FSH stimulates the gonad to secrete oestrogen or testosterone

38

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

+ 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

What are pituitary adenomas?

+ Common benign tumours of the pituitary gland

+ Some tumours secrete one or more hormones in excess

40

Where does the thyroid gland lie?

Anterior to the trachea in the neck

41

How does the thyroid glands develop?

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

42

What hormones are secreted by follicular cells in the thyroid?

+ Tri-iodothyronine (T3)

+Thyroxine (T4) - requires iodine

43

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

The colloid

44

What does thyroxine regulate?

+ Energy use; rate of metabolism

+ Protein production; growth and development

+ Regulates sensitivity of cells to other hormones

45

What do parafollicular (aka C) cells produce?

Calcitonin

46

What does calcitonin regulate?

It regulates calcium homeostasis and stimulates osteoblasts

47

From where does the parathyroid gland develop?

The wall of the pharynx

48

Where is the parathyroid found?

+ Embedded in the posterior aspect of the thyroid

+ Two pairs of glands

49

What does the parathyroid produce?

Parathyroid hormone

50

What does parathyroid hormone regulate?

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

51

What two regions form the adrenal glands?

+ Cortex (outside)
+ (Adrenal) medulla (inside)

52

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

+ Zona glomerulosa
+ Zona fasciculata
+ Zona reticularis

53

What cells form the (adrenal) medulla?

Neural crest cells - neuroectoderm

54

What does the adrenal cortex produce?

Steroid hormones

55

What does the adrenal cortex develop from?

It develops from the mesoderm of the posterior abdominal wall

56

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

Mineralocorticoids - e.g Aldosterone

57

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

Glucocorticoids - e.g Cortisone

58

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

Sex steroids - e.g Androgens

59

What type of cells does the adrenal medulla contain?

Chromaffin cells

60

What do the chromaffin cells in the adrenal medulla produce?

Catecholamines:

+ Epinephrine
+ Norepinephrine
+ Dopamine

61

What does the adrenal medulla have a direct connection with?

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

62

What kind of gland is the pancreas?

Exocrine and endocrine

63

How does the pancreas develop?

+ As an out growth of the gut tube

+ Closely associated with the development of the gall bladder

64

What forms the exocrine component of the pancreas?

Pancreatic acini

65

What do the pancreatic acini produce?

Pancreatic amylase

66

What forms the endocrine component of the pancreas?

The islets of Langerhans

67

What do the islets of Langerhans produce?

+ Glucagon (alpha cells)
+ Insulin (beta cells)

68

What hormone does the GI tract produce?

Gastrin

69

What hormone do the kidneys produce?

Renin