the endocrine system - pituitary gland Flashcards
purpose of endocrine system
tightly regulated synthesis and secretion of diverse array of chemical messenger molecules called HORMONES
hormones
-regulate numerous organ/tissue systems
-control growth, metabolism + reproduction
-plays key role in homeostasis
definition of hormone
chemical messenger produced and secreted by a specialised endocrine gland that is transported in the bloodstream to a distant target organ/cell where it elicits a physiological response
primary endocrine glands
-pineal
-hypothalamus
-pituitary
-thyroid
-parathyroids
-thymus
-adrenals
-pancreas
-ovary/testes (gonads)
secondary endocrine tissues
-heart
-lungs
-liver
-kidneys
-thymus
-gut
-placenta
different modes of cell-cell communication
-paracine
-autocrine
-neurotransmission
-endocrine
-neuro-endocrine
THREE main types of hormone
-proteins/peptides
-cholesterol derivatives
-modified amino acids
proteins/peptides
-growth hormone
= hydroPHILIC
cholesterol derivatives
-steroids (e.g. oestrogen, testosterone)
-vitamin D
= hydroPHOBIC
modified amino acids
-adrenaline
= hydroPHILIC
-thyroid hormones
= hydroPHOBIC
types of receptors that hormones (ligands) bind to
-membrane-bound receptors
-intracellular receptors
which types of hormone for which receptor ?
-water soluble -> plasma-membrane receptors
-lipid soluble -> intracellular receptors
endocrine system & nervous system
work together to maintain HOMEOSTASIS
what is the primary link between the endocrine & nervous systems ?
the HYPOTHALAMUS
-it produces specific chemical messengers that stimulate or suppress hormone secretions from the PITUITARY gland
what is known as the master endocrine gland ?
the pituitary gland, it controls all the other peripheral endocrine glands
pituitary gland
-regulate growth, development, mood, tissue function, metabolism and sexual function
-plays key role in homeostasis
pituitary gland has 2 distinct lobes
-anterior
-posterior
hypothalamic regulation of ANTERIOR pituitary gland
-hypothalamic neurons fire, releasing neurohormone (e.g. TRH) from the nerve ending diffusing into capillary network
-runs down into hypophysial portal vein then the primary capillary plexus and then the secondary capillary plexus
-releasing hormones stimulate pituitary hormone secretions
-anterior pituitary hormone (e.g. TSH) released to target tissue/endocrine gland (e.g. thyroid)
example of hypothalamic reg. of ANTERIOR pituitary gland
-TRH released by hypothalamus
-thyrotrophic cell secretes TSH in response to TRH
-TSH reaches thyroid gland (target)
posterior pituitary
-different tissue from ant. pituitary
-downgrowth of the base of the hypothalamus
-magnocellular neurons produce the hormones: ADH and oxytocin
-magnocellular neuron send axons down the pituitary stalk
-eventually terminating in the post. pituitary gland itself
anterior pituitary
-GH
-ACTH
-TSH
-FSH
-LH
-PRL
-MSH
posterior pituitary
-ADH
-OXY
growth hormone (GH)
-essential for growth + development of bones, muscles & other organs
-many effects of GH mediated by insulin-like growth factor (IGF) from liver
how does growth hormone (GH) work ?
enhances:
-protein synthesis
-decreases glucose utilisation
-promotes fat mobilisation
adrenocorticotropic hormone (ACTH)
-essential for the growth + function of adrenal cortex
how does adrenocorticotropic hormone (ACTH) work ?
acts on adrenal cortical cells to stimulate their manufacture of:
-mineralocorticoids (e.g. aldosterone involved in salt reg.)
-glucocorticoids (e.g. cortisol involved in glucose metabolism)
thyroid-stimulating hormone (TSH)
-essential for growth + function of the thyroid gland
how does thyroid-stimulating hormone (TSH) work ?
stimulates thyroid gland to secrete thyroid hormones (T3 & T4)
follicle-stimulating hormone (FSH)
-gonadotropic hormone
-promotes growth of ovarian follicles in females
-promotes production of sperm in males
luteinising hormone (LH)
-gonadotropic hormone
-stimulates ovulation + development of corpus luteum (CL) in females
-stimulates production of testosterone by testis in males
corpus luteum (CL)
-after ovulation, burst follicle on surface of ovary undergoes process called luteinisation
-transforms into structure called corpus luteum
-LH triggers ovulation and kickstarts the formation of CL
-CL produces oestrogen and progesterone
prolactin (PRL)
-stimulates development + growth of the mammary glands
-stimulates milk production during pregnancy
-sucking motion of baby stimulates prolactin secretion
how does prolactin (PRL) work ?
-secreted by ant. pituitary to act upon receptors on cells within milk producing structures of the mammary gland
-milk glands contain layer of epithelial cells that synthesise and secrete milk
melanocyte-stimulating hormone (MSH)
-regulates skin pigmentation
-promotes deposition of melanin in the skin after exposure to sunlight
how does melanocyte-stimulating hormone (MSH) work ?
acts on melanocytes (found in the skin) where there is deposition of melanin
antidiuretic hormone (ADH)
-stimulates the reabsorption of water by the renal tubules
-hyposecretion of ADH can result in diabetes insipidus (excessive thirst & copious dilute urine)
oxytocin (OXY)
-stimulates uterus to contract during childbirth
-stimulates mammary glands to release milk in response to suckling
