The Endocrine System Flashcards
What is a paracrine secretory cell?
- Only affects neighbouring cells, rapid and locally degraded
- distributed by diffusion
What is an autocrine secretory cell?
- Only affects itself i.e. has receptors for its own messengers
- Distributed by diffusion
Give examples of paracrine secretion messengers?
Histamine
NO
Give examples of Neurotransmitter messengers?
AcH
Amines
Amino Acids
Neuropeptides
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
What is hormonal secretion?
secretion into blood by endocrine cells e.g. thyroid hormone or adrenaline
What is neurohormonal secretion?
secretion into blood by neurosecretory neurones e.g. ADH
What is an endocrine cell?
Ductless gland which secrete chemical messengers Into blood
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
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
Give examples of amines?
Catecholamines e.g. noradrenaline
Dopamine
thyroid hormone
Give example of Peptides?
Oxytocin
ADH
Glucagon
Give examples of Proteins
Human Growth hormone
Insulin
Parathyroid
Give examples of Steroids?
Testosterone
Progesterone
Aldosterone
Which hormones use free transport?
Amines, proteins and peptide
Which hormones use protein bound transport?
Steroids and thyroid hormones
What proteins do hormones bind to?
globulins and albumin
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
