The Endocrine System

The Endocrine SystemEndocrine vs exocrine glandsEndocrine glands produce and secrete hormones into the bloodstreameg. the pituitary gland Exocrine glands secrete through ducts eg. salivary glands

HormonesHormones chemical signals released by specialized cells of the body to exert an effect on cells in other parts of the body

There are 2 classes of hormones:

Steroid hormones derived from cholesterolmulti-aromatic structurelipid soluble

Steroid hormonesMode of action:

Diffuse through cell membrane of cells (phospholipid soluble)

Combine intercellularly with receptor molecule

Initiates transcription of specific gene(s)

Effect achieved by resulting protein(s)

HormonesHormones chemical signals released by specialized cells of the body to exert an effect on cells in other parts of the body

There are 2 classes of hormones:

Protein hormonesmade of amino acidswater soluble

InsulinGrowth hormoneParathyroid hormone

Protein hormonesMode of action:

Attach to specific membrane receptors(hormone acts as first messenger)

Signal transduction results in intercellular molecule activation(molecule is second messenger)

Molecule up/down regulates protein activity within cell

Effect is achieved by activated proteins

Glands of the endocrine systemPituitary glandAttached to the hypothalamusTwo-lobed (anterior & posterior)Each lobe releases different hormones

Posterior pituitaryStores/release hypothalamus-made hormoneseg. antidiuretic hormone, ADH, oxytocin

Anterior pituitaryMakes its own hormones but release is controlled by hypothalamuseg. growth hormone, follicle-stimulating hormone, luteinizing hormone

Glands of the endocrine systemPancreasSmall gland containing endocrine & exocrine cellsEndocrine tissue called islets of Langerhans and contains 2 types of cells:

-cells produce insulin released when blood sugar is highcauses muscle, liver and other organs to take up glucose (reducing blood sugar)

-cells produce glucagonreleased when blood sugar is lowcauses glycogen in aforementioned tissues/organs to be converted to glucose (raising blood sugar)Glands of the endocrine systemAdrenal glandsLocated above each kidneyConsists of adrenal medulla and adrenal cortex

MedullaRegulated by nervous systemMakes adrenaline (epinephrine) & noradrenaline (norepinephrine)Sypathetic nerves cause release of both hormonesCauses conversion of glycogen to glucose & ups heart rate, breathing rate, etc.

CortexProduces sex hormones and hormones involved in stress conditions (eg. cortisol) and water reabsorption (eg. aldosterone)

Glands of the endocrine systemThyroid/parathyroid glandsLocated in neckThyroid hormones effect growth & specific rates of function within the body (eg. calcitonin regulates bone-calcium homeostasis)

OvariesLocated in lower abdomen of femalesProduce estrogen and progesterone which regulate reproductive health (eg. the menstrual cycle)

TestesLocated in the scrotum of malesProduce testosterone which maintains libido, muscle strength and bone density

Nervous + Endocrine = There are 3 main pathways of hormonal control:

Endocrine pathwayStimulus

Endocrine gland

Blood vessel

Target

Response

Nervous + Endocrine = There are 3 main pathways of hormonal control:

Neurohormone pathwayStimulus

Hypothalamus

Blood vessel

Target

Response

Nervous + Endocrine = There are 3 main pathways of hormonal control:

Neuroendocrine pathwayStimulusHypothalamusBlood vesselEndocrine glandTargetResponse

Try thisRead pg. 938Section 46.5