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Module 203 THEME 1 > Lecture 1- Introduction To The Endocrine System > Flashcards

Lecture 1- Introduction To The Endocrine System Flashcards

1
Q

How has the nervous system evolved?

A
  • The easiest way for two cells to communicate is for cell A to release a chemical messenger
  • this is limited by distance so a way this can be overcome is the growth of cell A towards cell B so that release of transmitter towards cell B isn’t wasteful
  • this is the nervous system that we recognise
  • it allows very rapid and focused communication between individual cells
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2
Q

How has the endocrine system evolved?

A
  • cell A releases chemical messenger into carrier medium
  • the transmitter has to go all around the body (very non specific and the transmitter is massively dilated so potent transmitters needed)
  • The Endocrine System allows for slow, sustained communication between groups of cells
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3
Q

What is the endocrine system?

A

A system of ductless glands which secrete hormones into the blood.

Each hormone may act on many different target tissues e.g. testosterone which influences the brain, muscles, fat , reproductive organs

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4
Q

Name 9 endocrine glands

A

Pineal gland

Pituitary gland

Thyroid gland

Parathyroid gland

Thymus

Adrenal gland

Pancreas

Ovary

Testis

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5
Q

What is the role if the hypothalamus in the endocrine system?

A

It is where your brain meets the endocrine system - the brain influences the endocrine system

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6
Q

What is the pineal gland involved in?

A

Sleep-wake cycles

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7
Q

Location of pituitary gland? What does it do

A

Hangs down from the brain, encased in skull (sella turcica)

Sometimes called the master gland as it controls the actions of other glands

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8
Q

What is the anatomy of the pituitary gland

A

Infundibulum- stalk of the pituitary gland

Split into anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)

Hypothalamico-adenohypophyseal portal vessels run through the infundibulum to the ant. Pituitary

Hypothalamico-neurohypophyseal tract runs through infundibulum to the posterior pituitary

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9
Q

What is the location of the thyroid gland and parathyroid gland?

A

Thyroid - wrapped around the trachea

Parathyroid- posterior of thyroid

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10
Q

What is the function of the thyroid gland?

A

Control of metabolic rate and maturation

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11
Q

What is the function of the parathyroid gland?

A

Involved in calcium homeostasis

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12
Q

What is the endocrine function of the pancreas? What is the endocrine function?

A

Endocrine - secretes hormones insulin and glucagon into the blood to regulate blood glucose

Exocrine- secretes digestive enzyme directly into GI tract

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13
Q

Function of the adrenal cortex? Function of the medulla?

A

Adrenal cortex- concerned with longer term stress, sodium and glucose homeostasis

Medulla- concerned with short term stress response

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14
Q

What is the function of the gonads?

A

The are responsible for the development of secondary sexual characteristics and for reproduction

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15
Q

Three main types of hormone receptor

A

Steroid hormone receptor

G-protein coupled receptor

Tyrosine kinase receptor

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16
Q

Explain steroid hormones and steroid hormone receptors

A
  • steroid hormones come from the gonads and adrenal cortex and are not water soluble (they are lipid soluble
  • Steroid hormones are thrfore carried in the blood found to protein
  • when they encounter a lipid membrane they unbind from the protein
  • the hormone then crosses the cell membrane and binds to an intracellular membrane (could be cytoplasmic or nuclear) and the receptor transports the hormone to the nucleus
  • hormone-receptor complex then binds to the hormone-response element of the DNA and it infulences gene transcription
  • the method of action of steroid hormones is to influence protein synthesis
  • The receptor may be constitutively active (The receptor itself can influence protein synthesis, in the absence of steroid hormone - with the presence of hormone the hormone will either accelerate or prevent this synthesis)
17
Q

What are G-protein coupled receptors?

A

They consist of a seven transmembrane domain and involve the synthesis of the second messengers IP3 and cAMP

They often are for water soluble hormones - the hormone binds to the extracellular portion of the receptor and never crosses the cell membrane

Second messengers phosphorylate the intracellular regulatory protein to influence cellular activity

As a general rule, if the hormone causes smooth muscle contraction then it acts via IP3 and if it causes relaxation it acts via cAMP

18
Q

What are TK Receptor?

A

A membrane-bound enzyme which is a single strand of protein although two receptors must be present for hormone action (dimerized receptor)

Mechanism of action:

  • hormone e.g. prolactin binds to extracellular part causing intracellular part to increase its enzyme activity and act as an enzyme to phosphorylate tyrosine
  • one hormone molecule binds to each receptor

These receptors are typically involved in growth and development e.g GH acts via this receptor because it usually gives very slow long term effects (except for insulin which takes around 15 mins)

19
Q

Peptide hormones?

A

-Chains of amino acids

Highly water soluble

Susceptible to digestion (by protease) so aren’t orally active

Unable to cross cell membrane without a carrier protein

Act on membrane bound receptors

Short plasma half life

E.g. insulin

20
Q

What are steroid hormones?

A

Highly lipid soluble

Transported in blood bound to protein

Only the unbound hormone is orally active

E.g. progesterone

21
Q

What hormones do the hypothalamus and anterior pituitary secrete? Give 3 examples

A

Anterior pituitary secretes stimulating (or Trophic) hormones which stimulate a gland to release its hormone

Hypothalamus secretes releasing hormones to control the action of the pituitary gland

Examples ( first is the releasing hormone, then the stimulating hormone, then the gland the stimulating hormone acts on and finally the hormone released from the gland)

  • TRH,TSH, thyroid, Thyroxine
  • CRH, ACTH, adrenal cortex, cortisol
  • GnRH, FSH, ovary, oestrogens
22
Q

What do FSH and LH cause the ovary to secrete?

A

FSH - oestrogens

LH - progesterone

23
Q

What do FSH and LH cause the ovary to secrete?

A

FSH - oestrogens

LH - progesterone

24
Q

What is the negative feedback in the endocrine system, using the example of cortisol, thyroid hormone and oestrogen?

A

Cortisol suppresses the secretion of ACTH and CRH

Thyroid hormone acts to decrease TRH and TSH

Oestrogens act to decrease GnRH and FSH

25
Q

What is the result of negative feedback on levels of hormone?

A

A common consequence of neg feedback is cyclical variation in hormone conc

Cortisol has a 24h cycle to do with circadian rhythms (high levels in morning , low at night

Module 203 THEME 1 (3 decks)

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