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Introduction to medicine (Year 1) > Introduction to endocrinology > Flashcards

Introduction to endocrinology Flashcards

1
Q

Define homeostasis

A

Maintenance of steady state of internal environment

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2
Q

Give examples of variables controlled by homeostasis

A

Physical entities:

  • Blood pressure
  • Core temperature

Circulating concentrations of chemical substances:

  • Ions, e.g. Na+, Ca2+
  • Nutrients e.g. blood glucose concentration
  • Hormones
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3
Q

Briefly outline how negative feedback works when body temp changes

A

There’s a set point at which body temp should be (With infection, the set point is changed and body temp rises)

Change in body temp detected by hypothalmic temperature receptors and/or cutaneous temperature receptors (on skin, these can induce thermoregulatory effects)

Hypothalamus induces negative feedback, if heat needs to be lost, vasodilation occurs to allow evaporation of water via sweating

If heat needs to be gained, muscles begin shivering, vasoconstriction occurs to reduce heat loss, increased metabolism to bring body back to core body temperature

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4
Q

What are the benefits of an increased body temp and what causes an increase in body temp?

A

Pyrogens (bacteria or virus infections) change the set point to a higher level resulting in fever

Benefits are:

  • Inhibits bacterial growth
  • Speeds up metabolic reactions
  • Increases delivery of WBCs to infection sites
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5
Q

How is body temp increased?

A
  • Blood flow shifted to core to conserve heat
  • Increased muscle activity (shivering)
  • Chills stop when high temp reached
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6
Q

Describe the baroreceptor reflex

A

Homeostatic control of blood pressure

Change in BP detected by baroreceptors, which can tell how much the arteriole walls have deformed/stretched, and therefore can tell when there’s a change in TPR

Baroreceptors signal medulla

Medulla signals heart and TPR is adjusted accordingly

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7
Q

Describe how hypertension can effect blood pressure regulation

A

Hypertension causes resetting of sensitivity of baroreceptors, making them more sensitive.

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8
Q

How are cortisol concentrations controlled?

A
  • Hypothalamus receives impulse, releases CRH on anterior pituitary glad
  • Anterior pituitary gland releases ACTH on adrenal cortex
  • Adrenal cortex secretes cortisol
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9
Q

What is positive feedback?

A

Response of effector output reinforces the stimulus (e.g. blood clotting, ovulation, childbirth)

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10
Q

Describe the role of positive feedback in control of uterine contraction in labour by oxytocin

A
  • In labour oxytocin stimulates uterine muscle contractions
  • Cervix dilates, activates stretch receptors
  • Action potentials signal to hypothalamus
  • Stimulates further release of oxytocin
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11
Q

What are the major endocrine glands? Describe their anatomical locations

A
  • Pineal - Deep in middle brain
  • Hypothalamus - Superior to midbrain, inferior to thalamus (Part of the diencephalon)
  • Pituitary - Within sella turcica of neurocranium
  • Thyroid - Superficial to trachea
  • Parathyroid - Next to 2 thyroid glands (lateral)
  • Adrenal - Superior to kidneys
  • Pancreas - Deep to stomach
  • Ovaries (women) - Lower abdomen, on right and left sides of uterus
  • Testes (men) - underneath penis
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12
Q

What does the hypothalamus do?

A

Releases and inhibits hormones

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13
Q

What does the anterior lobe of the pituitary gland release?

A

Trophic hormones

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14
Q

What does the posterior lobe of the pituitary gland release?

A

Oxytocin and vasopressin (ADH)

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15
Q

What does the thyroid gland release?

A

Thyroxine (T4)

Tri-iodothyronine (T3)

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16
Q

What does the adrenal cortex release?

A
  • Cortisol
  • Aldosterone
17
Q

What does the adrenal medulla release?

A

Adrenaline/noradrenaline

18
Q

What do the gonads release?

A

Oestrogen

Androgens

Progestagens

19
Q

What does the pancreas release?

A
  • Insulin
  • Glucagon
20
Q

What does the parathyroid gland release?

A

Parathyroid hormone

21
Q

Describe the endocrine signalling mechanism

A

Hormones released by an endocrine cell into general circulation and act on distant target sites

22
Q

Describe the paracrine signalling mechanism

A

Hormones released by an endocrine cell which act locally on adjacent cells

23
Q

Describe the autocrine signalling mechanism

A

Hormones released by a cell which act back on the same cell

24
Q

Describe the intracrine signalling mechanism

A

Conversion of an inactive hormone to an active hormone that acts within that cell

25
Q

What are the general functions of hormones?

A
  • Reproduction, growth, development - sex steroids, thyroid hormones, prolactin, growth hormone
  • Maintenance of internal environment - Aldosterone, parathyroid hormone, vitamin D
  • Energy production, utilisation and storage - Insulin, glucagon, thyroid hormones, cortisol, growth hormone
26
Q

Describe the 4 chemical classes of hormone

A

Protein/peptide hormones - Hypothalmic hormones (exceptions Dopamine), pituitary hormones, insulin, PTH, Calcitonin

Steroid hormones (cholesterol) - Cortisol, aldosterone, oestrogens, androgens, progestagens, vitamin D

Amino acid derivatives (tyrosine/tryptop han) - Adrenaline, noradrenaline, dopamine (tyrosine), thyroid hormones (tyrosine), Melatonin (trytophan)

Fatty acid derivatives - Prostaglandins, thromboxanes, prostacyclin

27
Q

Describe the nature of transport of protein and peptide hormones. What is their half-life?

A

Mainly unbound

Half life in circulation = minutes

28
Q

Describe the nature of transport of tyrosine derivatives (catecholamines), thyroid hormones. What is their half-life?

A

Thyroid hormones bound to plasma proteins

Half life in circulation = Seconds (catecholamines), hours (thyroid hormones)

29
Q

Describe the nature of transport of Cholesterol derivations (all steroids) What is their half-life?

A

Bound to plasma proteins

Half life in circulation = hours-days

30
Q

Define a neurosecretory cell

A

Neurones that secrete substances directly into the bloodstream to act as hormones

31
Q

What is the function of magnocellular neurones? What do other neurosecretory cells in the hypothalamus release?

A

In hypothalamus

Synthesise and release posterior pituitary hormones

Other neurosecretory cells release their hormones into the portal capillaries in which they are transported directly to endocrine cells of the anterior pituitary gland

32
Q

What is the effect of corticotrophin releasing hormone (CRH) released by the hypothalamus on the anterior pituitary gland?

A

Stimulates release of adrenocorticotrophic hormone (ACTH)

33
Q

What is the effect of Thyroid releasing hormone (TRH) released by the hypothalamus on the anterior pituitary gland?

A

Stimulates release of TSH (thyroid stimulating hormone

34
Q

What is the effect of Growth hormone inhibiting hormone (GHIH - somatostatin) released by the hypothalamus on the anterior pituitary gland?

A

Inhibits release of TSH

35
Q

What is the effect of Gonadotrophin releasing hormone (GnRH) released by the hypothalamus on the anterior pituitary gland?

A

Stimulates release of Luteinising hormone (LH) and follicle stimulating hormone (FSH)

36
Q

What is the effect of Dopamine released by the hypothalamus on the anterior pituitary gland?

A

Inhibits release of prolactin (PRL)

37
Q

What is the effect of Growth hormone releasing hormone (GHRH) released by the hypothalamus on the anterior pituitary gland?

A

Stimulates release of growth hormone (GH)

38
Q

What is the effect of Growth hormone inhibiting hormone (somatostatin) released by the hypothalamus on the anterior pituitary gland?

A

Inhibits release of growth hormone (GH)

39
Q

What are the peripheral endocrine glands controlled by the HPA?

A

Thyroid

Adrenal cortex

Gonads

Introduction to medicine (Year 1) (59 decks)

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