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week 7 > intro to endocrine > Flashcards

intro to endocrine Flashcards

1
Q

what is the endocrine system. brief description.

what regulatory system do they control?

A
  • the second integrative control system of the body
  • slower than the nervous system but last longer (more prolonged)
  • actions mediated by hormones which are secreted into the bloodstream and initiate physiological response in distant target cells through specific receptors

Control the

  • sexual development and reproduction
  • growth and development from child to adult
  • regulation of cellular metabolism
  • maintenance of homeostasis (eg. calcium, Na, K, Cl)
  • modulation of long term behavior (mood, sleep etc.)
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2
Q

what is the first integrative control system of body? why?

A

neuronal system, they act in millisecond response and can act very fast

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3
Q

describe hormones and list the three classes of hormones.

A

hormones are chemical messengers secreted by endocrine glands into the bloodstream that travels in the systemic circulation to distant target cells and initiate a physiological response in the target cells by targeting specific receptors
(Hormones are ‘chemical messengers’ that act on target cells through specific receptors)

  1. Proteins/ polypeptides (can be very small or very large)
    - usually injected when administering to patient
  2. Steroids (derived from cholesterol)
    - oral administration can be absorbed orally
  3. Amino acid/metabolite derivates
    - eg.
    - Thyroid hormones (thyroxine derived, T3, T4)
    - Catecholamines (adrenalin, dopamine noradrenaline)
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4
Q

what cells are all glands derived from?

A

epithelial cells

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5
Q

briefly describe exocrine glands and provide examples

A

An exocrine gland secretes its products for example enzymes, into ducts that lead to the target tissue.

-Epithelial cells form ducts to carry secretions onto the surface of the epithelium.
(can have a secretory portion at the tip of tubule or deep in tubule with non-secretory duct)
Eg. intestinal glands of Lieberkuhn, sweat gland in the skin, glands of stomach/uterus, the sebaceous gland opens up to skin
pancreatic duct secrete bicarbonate and enzymes and opens into the duodenum

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6
Q

briefly describe endocrine glands and provide examples

A
  • ductless glands
  • exists as a distinct gland (most of the cells release hormones, even if they are different hormones) or can be spaced among other cell types (in digestive system)
  • highly vascularised with rich blood supply
  • blood vessels have fenestrations that allow hormones to diffuse from the extracellular fluid into the bloodstream. The hormone then travels throughout the body

-endocrine secretion usually for distant target cells

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7
Q

briefly describe paracrine secretion and provide

examples

A

-Paracrine factors (polypeptides) diffuse over short distances without needing to travel in the blood as a target cell is within the same vicinity
-Cell to cell communication : inducing changes in
adjacent cells (e.g. peptide neurotransmitters)

  • Important in embryogenesis where gradients of
    polypeptides influence developmental change (hormones released into extracellular space, not blood, so the development of cells depend on the distance and concentration of the polypeptide released)
    eg. of some polypeptide with paracrine actions
    • Fibroblast growth factor (FGF) family
    • Hedgehog family (sonic hedgehog)
    • WnT family
    • TGF-β superfamily
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8
Q

Pineal gland?

A
  • a single small gland in the brain that releases the hormone melatonin
  • coordinates external environment and perception of light into Circadian and seasonal rhythms
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9
Q

Hypothalamus?

A

is the neurocrine-endocrine junction where the brain can influence/regulate/coordinate hormone secretion and affect other endocrine glands (thyroid gland)
-regulate activity in the hypothalamus which affects the secretion of the pituitary which regulates the thyroid gland

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10
Q

What is diurnal, and episodal?

A

Diurnal- regulated by higher centers according to circadian rhythms, etc
Episodal - spasmodic release in response to a signal

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11
Q

why are steroid and thyroid hormones bound to specific carrier/binding proteins?

A

they are hydrophobic in nature and need to be transported in blood so

  1. to improve solubility in blood
  2. to increase half life (binding/carrier protein large, but hormone is small, if not bound it will be filtered out into tubule of kidney and excreted. when it is bound it stays in blood)
  3. preserved as a reserve in blood (it can then dissociate from carrier protein to become biologically active and enter cells
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12
Q

Mechanism of hormone action?

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

• Where are the receptors?
1. Cell membrane receptors: peptides, glycoproteins
and catecholamines (hydrophilic soluble hormones)
- these are integral membrane proteins, binding of hormones to the ligand-binding site of protein causes conformation change of the receptor, causing cascade of reactions to induce physiological response

  1. Intracellular receptors in the nucleus: steroids and
    thyroid hormones (hydrophobic, lipophilic)
    - can diffuse through the plasma membrane and go to receptors in the nucleus and induce transcription of genes
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13
Q

What is the anterior pituitary gland (adenohypophysis) derived from?

A

derived from the epithelium of the roof of the mouth

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14
Q

What is the posterior pituitary gland (neurohypophysis) derived from?

A

it is a down growth of the hypothalamus (consists of nerve fibers)

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15
Q

what is the endocrine axes?

A
  • the target tissue of one
    hormone is another endocrine gland - allows
    amplification and fine control
  • Hypothalamus secretes hormones that control the
    secretion and release of pituitary hormones
  • Pituitary hormones stimulate/control many other
    endocrine glands (thyroid, gonads etc)
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16
Q

Function of the hypothalamus in endocrine system?

A
  1. controls release of anterior pituitary hormones by releasing hormones (prolactin is controlled by hypothalamic inhibiting factor)
  2. secretes the hormones ADH and oxytocin which are stored and secreted by the posterior pituitary gland
17
Q

describe adenohypophysis and its functions

A

stimulated to produce hormones by hormone secretion of hypothalamus which is then carried to anterior pituitary gland through hypophyseal portal circulation

  • has epithelial cells that secrete 6 different hormones
    1. growth hormone (GH)
    2. thyroid stimulating hormone (TSH)
    3. adenocorticotropic hormone (ACTH)
    4. Follicle stimulating hormone (FSH)
    5. Luteinising hormone (LH)
    6. Prolactin (involved in lactation)
18
Q

describe neurohypophysis and its functions

A

it consists of neural tissue from the hypothalamus
-stores hormones which are secreted by neurosecretory cells in hypothalamus (which are transported via neuronal axons in the stalk to the posterior pituitary gland)

Two hormones:

  1. ADH : to increase water reabsorption in kidneys
  2. Oxytocin : stimulates myoepithelial contraction to release milk in breast and aids in myometrium contraction in childbirth
19
Q

describe negative feedback in endocrine cascade and how hypothalamus is involved

A

the final product of a cascade acts to inhibit a hormone in higher levels of the cascade to regulate the secretion of it. the hypothalamus is usually an important site of negative feedback for many hormone cascades

20
Q

describe the effects of pituitary adenoma.

A

pituitary adenoma is the benign growth of a tumour in the pituitary gland causing proliferation of pituitary cells resulting in pituitary getting bigger. it might crush itself against bone or escape bony structure and enter the space of the optic chiasm thus disrupting vision

effects:

  1. acromegaly - overproduction of growth hormone when patient develops adenoma in adulthood after epiphyseal growth plates have fused
  2. gigantism - same but adenoma developed in childhood before long bone plate fused
21
Q

where is the thyroid gland and what is it developed from?

A
  • the thyroid gland is anterior to the trachea in neck
  • developed as a downgrowth of the epithelium from the tongue, it leaves a pit at the back of tongue called foramen caecum
22
Q

name the two types of cells in thyroid glands and what hormones they produce

A
  1. Follicular cells
    - produce tri-iodothyronine (T3) and thyroxine (T4)
    - these are stored in colloids in the form of thyroglobulins
    - thyroxine function :
    a. regulates energy use/rate of metabolism
    b. regulates protein production/ rate of growth and development
    c. regulates the sensitivity of cells to other hormones
  2. Parafollicular cells (C cells)
    - produce calcitonin: regulates calcium homeostasis by decreasing calcium levels in blood - stimulating osteoblast and inhibiting osteoclasts
23
Q

describe the thyroid disorders and name some symptoms

A

Hyperthyroidism

  1. exophthalmos (bulging of eyes out of the orbit forwards because of muscle growth behind eye
  2. growth of goiter

Hypothyroidism

  1. tired sleepy, lethargic appearance
  2. brittle hair
  3. in neonates - cretinism
  4. goiter
24
Q

describe parathyroid gland and what hormone it produces

A
  • embedded in the posterior aspect of the thyroid gland
  • 2 pairs of glands
  • developed from the wall of the pharynx
  • produce parathyroid hormone : regulate calcium homeostasis by stimulating osteoclast activity to break down bone and thus increase calcium levels in the blood
25
Q

what are the two main layers of the adrenal gland

A

adrenal cortex and adrenal medulla

26
Q

name the layers of the adrenal cortex and what cells are they made of. Also, describe the function of each layer (give an example of hormone produced)

A

adrenal cortex have epithelial cells which produce steroid hormones

  1. zona granulosa
    - mineralocorticoids (eg. aldosterone)
  2. zona fasiculata
    - glucocorticoids (cortisol)
  3. zona reticularis
    sex steroids : androgens
27
Q

what are the cells in the adrenal cortex derived from?

A

derived from the mesoderm of the posterior abdominal wall

28
Q

describe the adrenal medulla and list the hormones produced by it

A
  • derived from the neural crest cells- neuroectoderm
  • formed from Chromaffin cells which produce catecholamines:
    1. epinephrine
    2. norepinephrine
    3. dopamine

the adrenal medulla has direct connections with sympathetic nervous system and helps regulate fight/ flight response

29
Q

What is Cushing’s syndrome?

A

relates to the overproduction of cortisol hormone from the zona fasiculata layer of the adrenal cortex leading to fatty secretions that causes the buff appearance

30
Q

Describe the development of the pancreas?

A
  • pancreas develops as an outgrowth of the gut tube
  • closely related to the development of gall bladder
  • Ducts join before emptying into the duodenum
31
Q

Describe exocrine and endocrine functions of the pancreas. List a disorder for the dysfunction of each.

A

exocrine

  • involves pancreatic acinar cells/acini
  • produces pancreatic amylase etc.
  • disease :pancreatitis (inflammation of pancreas)

endocrine

  • involves islets of Langerhans
  • produce hormones glucagon (alpha cells) and insulin (beta cells)
  • disease: diabetes mellitus
32
Q

What hormone does the GI tract produce

A

gastrin

33
Q

what hormones do the kidneys produce

A

renin

34
Q

what hormones do the ovaries produce

A

oestradiol and progestrone

35
Q

what hormones do the testes produce

A

testosterone

week 7 (6 decks)

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