L21 Hypothalamus and Pituitary Function Flashcards Preview

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Flashcards in L21 Hypothalamus and Pituitary Function Deck (38):

Describe the action of the neurotransmitters in the Nervious system

  • Act close to the site of release
  • Target cells are muscles glands or neurons
  • Action is within milliseconds
  • Action duration is brief = milliseconds


Describe the action of the hormones in the endocrine system

  • Hormones act far from the site of release
  • Target cells are throughout the body
  • Action is within seconds to days
  • Action duration is long; seconds to days


Compare different intercellular chemical messengers

 Nervous system

NTs act close to site of release

Target cells: muslce, gland or neuron

Action is within milliseconds

Action duration is brief - milliseconds


 Endocrine system

Hormones act far from the site of release Target cells: throughout body

Action is within seconds to days

Action duration is long – seconds to days


Give an overview of the hormones and where they are released from in the body

Hypothalamus - releasing and inhibiting hormones

Pineal gland - melatonin

Thyroid gland - Thyroxine, triiodothyronine, calcitonin

Parathyroid Glands - PTH

Thymus gland - Thymosin, Thymopoietin

Heart - Atrial Natiuretic Peptite

Adrenal Glands - Cortex (cortisol, aldosterone), Medulla (epinephrine

Intestines - Secretin, Cholecystokinin

Testes - Testosterone

Ovaries - Oestrogen, Progesterone

Kidneys - Erytropoietin, Renin

Pancreas - Glucagon, Insulin, Somatostatin

Stomach - Gastrin

Pituitary Gland- Ant Lobe (ACTH, TSH, FSH, LH, prolactin) Posterior Lobe (Oxytoxin, ADH)


What are the functions of the endocrine system

  • Regulates metabolism & H2O & electrolyte balance
  • Induces adaptive changes to help body cope with stress
  • Promotes smooth, sequential growth & development
  • Controls reproduction
  • Regulates red blood cell production
  • Along with autonomic nervous system, controls & integrates both the circulation & the digestion & absorption of food


Where is the pituitary gland situated?

In the hypophyseal fossa (sella turcica) of the sphenoid bone


How is the pituitary gland linked to the hypothalamus?

By the infundibulim (pituitary stalk)


What are the lobes of the pituitary gland?

POSTERIOR (Neurohypophysis)

ANTERIOR (Adenohypophysis)



How is the POST lobe of the pituitary gland linked to the hypothalamus?

By a neuronal network

(Hypothalamo-hypophyseal tract)



How is the ANT lobe of the pituitary gland linked to the hypothalamus?

By a VASCULAR NETWORK - the pituitary portal system


What secretes ADH and oxytoxin?

The neuroendocrine system created by the POST PITUITARY and HYPOTHALMUS

(paraventricular nucleus and paraoptic nucleus are the cell bodies that synthesize the hormones)



What is the action of OXYTOCIN?

Stimulates uterine contraction and milk ejection


What is the action of ANTI-DIURETIC HORMONE (ADH)


Increases H20 permeability & absorption in renal collecting ducts, vasoconstrictor


What does the ANTERIOR Pituitary secrete?

Mainly TROPHIC hormones (These exert an effect on other endocrine glands)

GH - Growth Hormone

TSH - Thyroid Stimulating Hormone

ACTH - Adrenocorticotrophic Hormone

PRL - Prolactin

FSH - Follicle Stimulating Hormone

LH - Luteinising Hormone


What are Trophic Hormones? (tropic)


Give an example.

Regulates hormone secretion by another endocrine gland

Stimulates & maintains endocrine target tissues


Thyroid-stimulating hormone (TSH) -secreted from anterior pituitary, stimulates thyroid hormone secretion by thyroid gland, maintains structural integrity of thyroid gland

Other e.g.s ACTH, GH, FSH & LH (gonadotrophins)


What are gonadotrophins?

act to control testosterone, oestrogen, progesterone secretions

eg. ACTH, GH, FSH & LH (gonadotrophins)


What are the actions of

  1. ACTH - Adrenocorticotrophic Hormone
  2. Oxytocin
  3. Prolactin
  4. Gonadotrophins (FSH, LH)
  5. TSH
  6. MSH
  7. GH
  8. ADH

  1. stimulates the adrenal cortex to produce andrenocorticoids (and growth of gland)
  2. Stimulates uterine contraction & milk ejection
  3. enhances breast development and milk production

  4. Stimulates production of sperm in the testes, stimulates secretion of oestrogen by the ovaries and maturation of the ovarian follicles

  5. stimulates growth and activity of the thyroid gland and secretion of T3 and T4

  6. Melanocyte stimulating hormone acts upon skin - if excessive = excessive darkening of skin. Increases in humans during pregnancy. This, along with increased oestrogens, causes increased pigmentation in pregnant women. In Cushing's disease high levels of adrenocorticotropic hormone (ACTH) production also leads to high MSH levels, which cause an abnormal darkening. ACTH has MSH-like activity However– MSH has NO ACTH like activity

  7. Acts on bone and muscle, regulates metabolism, promotes tissue growth.

  8. Acts upon kidney. Increases H20 permeability & absorption in renal collecting ducts. Vasoconstrictor 




What are the two most important factors that regulate ANT pituitary hormone secretion? 

Hypothalamic Hormones

and Feedback by target gland hormones


What do the hypothalamic hypophysiotrophic hormones do and what are they?

Secretion of each anterior pituitary hormone is stimulated/inhibited by one or more of 7 hypothalamic hypophysiotropic hormones

GHRH - growth hormone releasing hormone

GHIH - growth hormone inhibiting hormone (SOMATOSTATIN)

TRH - thyroid releasing hormone

CRH - corticotrophin releasing hormone

PRH - prolactin releasing hormone

PIH - prolactin inhibiting hormone

GnRH - gonadotrophin releasing hormone


Summarise the action of the 7 hypothalamic hypophysiotropic hormones


How do the hypothalamic regulatory hormones reach the anterior pituitary from the hypothalamus?


What are the benefits of this route?

By means of the hypothalamic-hypophyseal portal system

Minimises dilution of hormones

Allows rapid response


What is the 3 hormone sequence in the negative feedback in hypothalamic-anterior pituitary control systems?

1.  Hypophysiotropic hormone (neurohormone)

2.  Anterior pituitary tropic hormone

3.  Peripheral target-endocrine gland hormone (acts to suppress secretion of tropic hormone driving it: long-loop negative feedback)


What is a 'portal system'

where you have one capillary bed flowing into another capillary bed


Generally, outline the diurnal (circadian) rhythms

During the night: (12am to 8am)

Body temperature - decreases

SBPressure - decreases

Plasma growth hormone - increases (rapidly)

Plasma ACTH - increases (in steps)

Plasma Melatonin - increases (smoothly)


What can endocrine disorders be attributable to?

  • hormonal deficiency (hyposecretion)
  • hormonal excess (hypersecretion),
  • decreased responsiveness of the target cells


What is Primary Hyposecretion?

Give examples of this

Too little hormone is secreted due to abnormality within gland

    Genetic, Dietary (e.g. lack of iodine), Chemical or toxic, Immunologic (autoimmune diseases), cancer, Iatrogenic (e.g. surgical removal)


What is Secondary Hyposecretion?

Gland is normal but too little hormone is secreted due to deficiency of its tropic hormone


What is tertiary hyposecretion?

problem within the hypothalamus 


What is 

  1. Primary Hyposecretion
  2. Secondary Hyposecretion
  3. Tertiary Hyposecretion 

  1. Too little hormone is secreted due to abnormality within gland

  2. normal gland - too little hormone is secreted due to deficiency of its tropic hormone

  3. problem within the hypothalamus 


what is panhypopituitarism?

a condition of inadequate or absent production of the anterior pituitary hormones


Explain the pathophysiology of panhypopituitarism

  1. ADH
  2. Growth Hormone
  3. LH FSH (Sex Steroids)
  4. TSH (Thyroxine)
  5. ACTH (Cortisol)


(global lack of hormone)

  1. Diabetes Insipidus - Polyuria, Polydypsia, Hypernatremia, Lethargy, Dehydration
  2. Dwarfism - Hypoglycaemia, short statuture 
  3. Oestrogen deficiency (delayed puberty, amenorhea) Testosterone deficiency (Micropenis, Delayed puberty)
  4. Hypothyroidism - Fatigue, Constipation, Cold Intolerance, Bradycardia
  5. Addison's Disease - Hypoglycaemia, Vomiting, Malaise 


Outline the actions of Growth Actions

Circian Rhythm, Stress and Fasting act upon GH

GHRH increases, Somatostatin decreases levels


  • Stimulates AA uptake
  • decreases glucose uptake
  • inhibits protein breakdown
  • increases muscle mass

Adipose Tissue

  • decreases glucose uptake
  • increases fat breakdown
  • decrease in fat deposits


  • increase in protein synthesis
  • increase gluconeogenesis
  • stimulates IGF production


What can cause hypersecretion?

Tumours that ignore normal regulatory input & continuously secrete excess hormone


What is

primary hypersecretion?

secondary hypersecretion (tertiary)?

Abnormality within gland

Excessive stimulation from outside the gland


What are the consequences of hypersecretion of

  1. ACTH
  2. Prolactin
  3. ADH
  4. TSH
  5. hGH in children
  6. hGH in adults

  1. ↑ ACTH - corticosteroid excess (Cushing’s disease)
  2. ↑ prolactin - impaired reproductive function
  3. ↑ ADH - fluid retention & low plasma osmolality
  4. ↑ TSH – Grave’s disease (not strictly an ↑ TSH but antibodies act like TSH)
  5. ↑ hGH in children - giantism
  6. ↑ hGH in adults - acromegaly


What does hypersecretion of growth hormone in children cause?



What does hypersecretion of growth hormone in adults  cause?


Thick phalanges, swelling within the tissue. Brow is protruding, jawline thick. Voices are deep – tissues have grown. 

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