endocrine system Flashcards
glands
widely separated secretory cells around capillaries
where do ductless glands discharge into?
- discharge directly into blood vessels
hormones
- chemical messengers carried to target
synthesised amino acids or steroids
what is homeostasis controlled by?
controlled by autonomic NS or endocrine
system, through positive or negative feedback
where does endocrine system give fine/subtle control too?
whole body, not just local area
endocrine glands (13 glands)
1 pituitary gland (+ hypothalamus) 1 pineal body 1 thymus 1 thyroid gland 4 parathyroid glands 2 adrenal (suprarenal) glands The islets of Langerhans (Pancreas) 2 ovaries or testes
where do hormones bind ?
Bind to receptor sites on target cells
Water-soluble hormone receptor on the
cell wall
Lipid-soluble hormone receptor inside cell
Level is variable & self-regulated, gives
fine & subtle control
Negative & positive feedback
what do hormones control
Control chemical/metabolic actions in cell
where is the Pituitary Gland & Hypothalamus located
Lies in hypophyseal fossa of sphenoid bone
Lies below hypothalamus and connected to it
by stalk called infundibulum
what is Thyroid Hormone (TSH) stimulated by
Stimulated by TRH
hypothalamus
what does thyroid gland secrete
thyroxin
when is TSH at its highest
at night
what type of feednach does TSH have
negative feedback
what is Adrenocorticotrophic hormone (ACTH) stimulated by
stimulated by CRH from Hypothalamus. Increases cholesterol & steroids, esp.
Cortisol.
when is ACTH at its highest and lowest
Highest 8am lowest midnight (circadian rhythm).
Neg feed back
what does ACTH increase
increases cholesterol & steroids, esp. Cortisol.
what does Prolactin stimulate
Prolactin Stimulates lactation – effect on breasts after parturition.
Stimulated by PRH hypothalamus. Inhibited by PIH. Relates to sleep.
what is prolactin stimulated by
Stimulated by PRH hypothalamus.
what is prolactin inhibited by
PIH
Where are Gonadotrophins (sex hormones) secreted to stimulate ?
secreted to stimulate FSH & LH. This stimulates Oestrogen & Progesterone and
testosterone
what are Posterior Pituitary made up of?
Made up of nervous tissue -Pituicytes
what does oxytocin stimulate
Oxytocin stimulates 2 target tissues – uterine smooth
muscle & muscle of lactating breast. Positive feed back
Antidiuretic hormone (ADH) or Vasopressin. what does it reduce and how?
reduces urine output by increasing
water permeability of distal convoluted tubules in the
kidney.
what are 2 thyroid glands
Thyroxin (T4) &
Triiodothyronine (T3)
what does calcitonin act on?
on bone & kidneys to reduce blood calcium when raised. Opposite effect to parathyroid hormone (PTH)
what is Parathyroid hormone – (PTH) secretion regulated by?
by calcium level (negative feedback)
functions of Parathyroid hormone – (PTH)
Main function increase blood calcium when low
Increases amount absorbed small intestine ……&/or
Reabsorbed from renal tubules………….&/or
Stimulates osteoclasts-destroys bone-Ca+ from bone
what is Ca+ needed for?
Ca+ needed for muscle contraction, blood clotting, nerve impulse transmission
Adrenal (Suprarenal) Glands
2 glands - 1 on each upper pole of kidney
4cm x 3cm
Each in 2 parts with different functions
Cortex – outer part
Medulla – inner part
what three types of hormones does Adrenal Cortex
Secrete
Glucocorticoids
Mineralocorticoids
Sex hormones
Glucocorticoids
Regulates metabolism & response to stress.
Circadian rhythm.
Functions of glucocorticoids
steroids) (4
Have anti-inflammatory action Suppress immune response suppress tissue response to injury Delay wound healing
Mineralocorticoids (aldosterone)
Maintenance balance water & electrolytes
Stimulates sodium reabsorption in renal tubules
where does the Adrenal Medulla develop from?
Develops from nervous tissue in embryo
what does the Adrenal Medulla produce?
Produces adrenaline & noradrenaline
Alpha cells secrete
glucagon
Beta cells secrete
insulin
Delta cells secrete
somatostatin (GHRIH)
what is the normal blood glucose ?
2.5 – 5.3 mmol/lt
what does the pineal gland excrete
Excretes melatonin
Histamine
secreted by mast cells. Part of inflammatory response
Serotonin
Contraction smooth muscle. Haemostasis
Prostaglandins
Inflammatory response, pain, fever, BP, blood clotting
Erythropoietin
Made in kidney. Blood formation
Gastrointestinal hormones
Gastrin, secretin, cholecystokinin influence digestive
juices