The Pituitary Gland Flashcards
What organs are the main organisers of the endocrine system?
Hypothalamus and pituitary gland
What is the hypothalamus connected to the pituitary gland by?
Stalk called the infundibulum
What are the 2 lobes of the pituitary gland?
Anterior and posterior pituitary
To the anterior and posterior pituitary, is hypothalamic communication neural or endocrine?
Neural to posterior pituitary
Endocrine to anterior pituitary
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What are some key integrative functions of the hypothalamus and pituitary?
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What do tropic hormones do?
Govern the release of another hormone
What kinds of hormones does the hypothalamus release?
Neurohormones
What kind of hormones does the posterior pituitary release?
Neurohormones (from hypothalamus)
What kind of hormones does the anterior pituitary release?
Endocrine hormones
What are the 2 forms of hypothalamic neurohormones?
Tropic
Non-tropic
Where do tropic hormones from the hypothalmus travel to?
Secreted into capillaries and travel to anterior pituitary
What do tropic hormones do?
Govern the relase of anterior pituitary hormones
Where do non-tropic hormones from the hypothalamus travel to?
Posterior pituitary (via axons of hypothalamic neurons)
Where they are released into the blood
What are 5 examples of tropic hypothalamic hormones?
Thyrotropic releasing hormone (TRH)
Corticotropin releasing hormone (CRH)
Growth hormone releasing hormone (GHRH)
Gonadotropin releasing hormone (GRH)
Prolactin releasing hormone (PRH)
What does TRH stand for?
Thyrotropin releasing hormone
What does CRH stand for?
Corticotropin releasing hormone
What does GHRH stand for?
Growth hormone releasing hormone
What does GnRH stand for?
Gonadotropin releasing hormone
What does PRH stand for?
Prolactin releasing hormone
What are 2 inhibiting tropic hypothalamic hormones?
Growth hormone inhibiting hormone (GHIH)
Dopamine
What does GHIH stand for?
Growth hormone inhibiting hormone
What is growth hormone inhibiting hormone (GHIH) also known as?
Somatostatin
What is dopamine also known as?
Prolactin inhibiting hormone (PIH)
What does PIH stand for?
Prolactin inhibiting hormone
What is the classification of all of the tropic hypothalamic hormones?
Peptides, except for dopamine which is an amine
How are hormones transfered from hypothalamus to anterior pituitary?
Through hypothalamo-hypophyseal portal system (network of tiny vessels)
Contrast the anterior and posterior pituitary in terms of:
type of tissue
connections via
also called
size
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Is the anterior or posterior pituitary larger?
Anterior makes up 2/3 of gland, posterior 1/3
What is the anterior pituitary also called?
Adenohypophysis
What is the posterior pituitary also called?
Neurohypophysis
What is production of anterior pituitary hormones controlled by?
Hypothalamus ‘releasing’ or ‘inhibiting’ tropic hormones (sometimes called factors
What are the 6 hormones released by the anterior pituitary gland?
Thyroid stimulating hormone (TSH)
Adrenocorticotrophic hormone (ACTH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Growth hormone (GH)
Prolactin
What is the classification of anterior pituitary hormones?
All are peptides, 5 are also tropic hormones and dopamine is an amine
What does TSH stand for?
Thyroid stimulating hormone
What does ACTH stand for?
Adrenocorticotrophic hormone
What does FSH stand for?
Follicle stimulating hormone
What does LH stand for?
Luteinising hormone
What does GH stand for?
Growth hormone
What is thyroid stimulating hormone (TSH) also called?
Thyrotropin
What is adrenocorticotrophic hormone also called?
Corticotropin
What is FSH and LH also called?
Gandotropins
What does prolactin do?
Stimulates milk production from the breast during lactation
What is the target organ of prolactin?
Mammary glands
What is the target organ of GH?
Musculoskeletal system
What is the target organ of TSH
Thyroid gland
What is the target organ of ACTH?
Adrenal cortex
What is the target organ of gonadotropins?
Gonads (ovary/testes)
What does TSH cause?
Thyroid hormone (TH) release from thyroid
What does addrenocorticotropic hormone cause?
Cortisol release from adrenal cortex
What tropic and what direct effects does GH have?
Tropic - IGF-1 release from liver
Direct - tissue metabolism
What tropic and what direct effect does luteinising hormone have?
Tropic - sex hormone release
Direct - regulation of reproductive function
What are the 3 integration centres involved in the feedback control of the anterior pituitary?
Hypothalamus
Anterior pituitary
Target endocrine cell
How do hormones themselves act as the negative feedback signal for the anterior pituitary?
Feed back to inhibit hormone secretion by integrating centres earlier in the reflex:
feedback from endocrine target is long loop feedback
feedback from anterior pituitary to hypothalamus is short loop feedback
links levels of hormones together and maintains plasma levels within correct range
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For the anterior pituitary, what provides long-loop feedback?
Endocrine targets
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For hypothalamus and anterior pitutiary, what provides short loop feedback?
Anterior pituitary to hypothalamus
What are the 2 neurohormones stored and released from the posterior pituitary?
Vasopressin
Oxytocin
Are the hormones released from the posterior pituitary formed there?
No, they are formed in the hypothalamus but stored and released fromt he posterior pituitary
What is vasopressin also known as?
Anti-diuretic hormone (ADH)
What does ADH stand for?
anti-diuretic hormone
What are vasopressin and oxytocin synthesised in?
Magnocellular neurons which have their cells bodies in specific areas of hypothalamus
Different subsets produce either vasopressin or oxytocin
How does vasopressin and oxytocin get from hypothalamus to posterior pituitary?
1) Axons project down infundibulim to posterior pituitary
2) Do not synapse with other neurons, terminals end directly on capillaries
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What classification of hormones do posterior pituitary hormones behave as?
Typical peptide hormones, so:
synthesis and storage in vesicles
acts on cell surface receptors
What is the main function of vasopressin?
Regulates water balance
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What is the main function of oxytocin?
Milk ejection and uterine contraction
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What causes the release of vasopressin?
Increased plasma osmolarity
Decreased volume/blood pressure
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What causes the release of oxytocin?
Labour (baby’s head against cervix)
Suckling
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What are the sites and mode of action of vasopressin?
Kidney collecting ducts - increases water reabsorption
Vascular smooth muscle - increases blood pressure
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What are the different classifications of endocrine disorders?
Hyposecretion (too little hormone secreted)
Hypersecretion (too much hormone secreted)
Hyporesponsiveness (reduced response of target cell)
Hyperresponsiveness (increased response of target cell)
1st degree disorders
2nd degree disorders
3rd degree disorders
What are the sites and mode of action of oxytocin?
Milk duct smooth muscle - contracts muscle, ejecting milk
Uterine smooth muscle - child birth
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What are 1st degree endocrine disorders?
Those in which the defect is in the cell that secretes the hormone
What are 2nd degree endocrine disorders?
Those in which there is too little or too much trophic hormones from pituitary
What are 3rd degree endocrine disorders?
Relates to hypothalamic defects