The Endocrine System Flashcards by mia Barry

What is a paracrine secretory cell?

Only affects neighbouring cells, rapid and locally degraded
distributed by diffusion

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What is an autocrine secretory cell?

Only affects itself i.e. has receptors for its own messengers
Distributed by diffusion

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Give examples of paracrine secretion messengers?

Histamine

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Give examples of Neurotransmitter messengers?

AcH
Amines
Amino Acids
Neuropeptides

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How do neurotransmitter messengers get released from the cell?

secreting cell is neurone which sends an electrical impulse down its axon into the axon terminal where exocytose and diffuse across to target cell

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What is hormonal secretion?

secretion into blood by endocrine cells e.g. thyroid hormone or adrenaline

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What is neurohormonal secretion?

secretion into blood by neurosecretory neurones e.g. ADH

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What is an endocrine cell?

Ductless gland which secrete chemical messengers Into blood

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Differences between nervous and endocrine system?

N v E
Mediator molecule: Neurotransmitter v hormone
Onset: millisecond v seconds, hours or days
Duration: brief v longer
Target cell: Muscle, glands or neurones v cells throughout body
site: close to release v long range

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What are the four types of hormones?

Amine - synthesised from tyrosine
Peptide - made of short chain amino acids
Protein - made of long chain amino acids
Steroid - derived from cholesterol

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Give examples of amines?

Catecholamines e.g. noradrenaline
Dopamine
thyroid hormone

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Give example of Peptides?

Oxytocin
ADH
Glucagon

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Give examples of Proteins

Human Growth hormone
Insulin
Parathyroid

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Give examples of Steroids?

Testosterone
Progesterone
Aldosterone

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Which hormones use free transport?

Amines, proteins and peptide

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Which hormones use protein bound transport?

Steroids and thyroid hormones

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What proteins do hormones bind to?

globulins and albumin

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What are the functions of the endocrine system?

Regulates metabolism
Adapts body to help cope with stress
Promotes Growth
Controls reproduction
Regulates RBC production
Regulates energy balance
Maintain homeostasis

What structure connects the pituitary gland and hypothalamus?

Infundibulum

What bone houses the pituitary gland and what is the indentation of the bone the gland sites in called?

Sphenoid bone

Sphenoid sinus

What structure is most likely to be affected by a pituitary tumour?

Optic chiasma causing bilateral hemianopsia (peripheral vision loss)

What are the two lobes of the pituitary called?

Posterior pituitary = Neurohypophysis made up of neural tissue derived from brain
Anterior pituitary = Aden-hypophysis made up of glandular tissue derived from the mouth

Via what pathways is the pituitary connected to the hypothalamus?

posterior = neural pathway 
anterior = vascular pathway

What hormones are secreted by the posterior pituitary?

ADH and oxytocin (synthesised in hypothalamus by released from pituitary)

What hormones are released from the anterior pituitary?

- Growth hormone - Thyroid stimulating hormone - Adrenocorticotrophic hormone - prolactin (non tropic) - follicle stimulating hormone - Luteinisng hormone - Melanocyte stimulating hormone (non tropic) (rest tropic)

What structures in the hypothalamus are connected to the posterior pituitary?

Supra-optic and paraventricular nuclei

What does Oxytocin do?

stimulates uterine contraction and milk ejection

What does ADH do (brief)?

- increases water permeability and absorption in renal collecting ducts - vasoconstriction of vascular smooth muscle to increase BP

What is a tropic hormone?

Hormone which regulates another hormone secretion by a different endocrine gland

What two factors affect secretion of anterior pituitary gland hormones?

- Hypothalamic hormones - Feedback by target gland hormones (negative feedback loops will stop secretion of hypothalamic hormones when levels of target hormone in blood is normal)

What are the hypothalamic hypophysiotropic hormones?

- Growth hormone releasing hormone and growth hormone inhibiting hormone (somatostatin) - Thyroid releasing hormone and corticotrophin releasing hormone - Prolactin releasing hormone and prolactin inhibiting hormone (dopamine) - Gonadotrophin releasing hormone (controls FSH and LH) - The balance of these hormones will decide wether hormone secreted

What structure connects the anterior pituitary and hypothalamus

the hypothalamic pituitary portal system (two sets of capillaries)

Which hypothalamic hormones act on which anterior pituitary hormones?

``` PRH + PIH > Prolactin TRH > Thyroid stimulating hormone CRH > Adrenocorticotrophic hormone GHRH + GHIH > Growth hormone GnRH > FSH + LH ```

What is the benefit of using the portal system?

- Minimises dilution of hormones - Allows for a rapid response means hormones don't need to travel through blood all the way around the body to get back to pituitary

What are the hormones released from hypothalamus called

hypothalamic hypophysiotropic hormones

What is the normal three hormone sequence in hypothalamic anterior pituitary systems

- First hypothalamic hypophysiotropic hormone - Then anterior pituitary hormones (mainly tropic) - Finally peripheral gland hormones (target gland)

Where do the negative feedback loops occur?

Long loop negative feedback = peripheral gland hormone inhibits anterior pituitary secretion or hypothalamic secretion short loop = pituitary gland hormone inhibits hypothalamic hormone

What needs to be taken into account when measuring hormone levels at different times of day?

Hormone levels often have diurnal or circadian rhythms so change naturally across the day

What are the three types of hypo secretion and hyper secretion?

Primary - abnormality in target gland which will then not secrete final hormone Secondary - deficiency in tropic hormone released by anterior pituitary gland Tertiary - deficiency in hypothalamic hormone which then results in too little tropic hormone and too little target gland hormone

What is panhypopituitarism?

Deficiency in all hormones produced by anterior and posterior pituitary glands

What is the cause of hormone hyper secretion?

Tumours which ignore normal regulatory input and continuously secrete excess hormone can again by primary, tertiary or secondary

What is the consequence of hyper secretion of each anterior pituitary hormone?

ACTH - Cushing Syndrome Prolactin - impaired reproductive function ADH - fluid retention and low plasma osmolality TSH - Graves disease hGH - children = gigantism, adults = acromegaly

What are the causes of primary hyposecretion?

Genetic, Dietary, Chemical, Immunologic, cancer, Iatrogenic