Chapter 18

The Endocrine System

communication between cells

mechanisms

direct cell-to-cell

cell-to-cell(short distance)

cell-cell

cell-to-cell(long distance)

gap junctions

paracrinelocal chemicals

neurotransmitters

endocrinechemicals via

bloodstream

Table 18-1

Endocrine system

cells (tissues, organs) that produce chemical messengers (hormones) that travel via the bloodstream to have distant effects

Endocrine system

classes of hormones:

peptide:

lipid:

•amino acid derivatives•polypeptides

•eicosaniods(from arachidonic acid)

•steroids(from cholesterol)

fig. 18-2

Endocrine system

receptors and mechanism of action

peptide hormones

receptors on cell surfaceactivate G proteinsuse second messengers

(cAMP)activates enzymesalter cellular activity

Endocrine system

receptors and mechanism of action

steroid hormones

diffuse across membranereceptors in cytoplasmactivate specific genes

alter cellular activity

100 keys (pg. 599)

“Hormones coordinate cell, tissue, and organ activities on a sustained basis. They circulate in the extracellular fluid and bind to specific receptors on or in target cells. They then modify cellular activities by altering membrane permeability, activating or inactivating key enzymes, or changing genetic activity.”

Endocrine reflexes

triggered by:

humoral stimulibody fluid changes

hormonal stimuli

neural stimuli

Endocrine reflexes

many are controlled by negative feedback

simple - a single hormone

complex - two or moreseveral steps

many are controlled by the hypothalamus

the “master gland” of the endocrine system:

pituitary gland

an

teri

or

post

eri

or

fig 18-6

pituitary gland

produces 9 “peptide” hormones

anterior *posterior

TSHACTHFSHLHprolactinGHMSH

ocytocinADH

pituitary gland

controlledby

hypothalamus

produces

RH releasing hormonesIH inhibiting hormones

pituitary gland

controlledby

hypothalamus

fig 18-7

produces

RHIH

pituitary gland

anterior

TSHACTHFSHLHprolactinGHMSH

thyroid glandadrenal glandgamete developmentreproductionmilk productiongrowthpigment cells

pituitary gland

an example

TSH

thyroid gland

1 2

3

4

5

pituitary gland

controlledby

hypothalamus

fig 18-7

produces

RHIH

OT

ADH

OTADH

pituitary gland

fig 18-9

the “master gland”

100 keys (pg. 604)

“The hypothalamus produces regulatory factors that adjust the activities of the anterior lobe of the pituitary gland, which produces 7 hormones. Most of the hormones control other endocrine organs, including the thyroid gland, adrenal gland, and gonads. The anterior lobe also produces growth hormone, which stimulates cell growth and protein synthesis.”

100 keys (pg. 604)

“The posterior lobe of the pituitary gland releases two hormones produced in the hypothalamus; ADH restricts water loss and promotes thirst, and oxytocin stimulates smooth muscle contractions in the mammary lands and uterus (in females) and the prostate gland (in males).”

other endocrine organs

thyroid glandsC-cells of thyroid gland

parathyroid glandsadrenal glands

cortexmedulla

pineal glandpancreasintestines, gonads, kidneys, adipose

other endocrine organs

thyroid glands

produce thyroxine (T3, T4)

affect all cells

O2 use ATP production HR, bp erythropoiesis

other endocrine organs

thyroid glandsC-cells of thyroid gland

parathyroid glands

calcitonin blood [Ca2+ ]

PTH blood [Ca2+ ]

100 keys (pg. 612)

“The thyroid gland produces (1) hormones that adjust tissue

metabolic rates and

(2) a hormone that usually plays a minor

role in calcium ion homeostasis byopposing the action of parathyroid

hormone.”

to here 4/18lec #39

other endocrine organs

adrenal glandscortex

medulla

mineralocorticoidsaldosterone retain Na+

lose K+

glucocorticoidshydrocortisone

anti-inflammatory

NE, E (Sympathetic ANS)

100 keys (pg. 616)

“The adrenal glands produce hormones that adjust metabolic activities at specific sites, affecting either the pattern of nutrient utilization, mineral ion balance, or the rate of energy consumption by active tissues.”

other endocrine organs

pineal gland

produce melatonin

timing of sexual maturation

protect from free radicals

set circadian rhythms

other endocrine organs

pancreas

produces digestive enzymes

contains isletsproduce (4) hormones

insulinglucagon

pancreas

insulin

released when blood [glucose]is greater than ~110 mg/dl

most cells in the body have insulin receptor

insulin dependent

insulin

most cells in the body have insulin receptor

insulin dependent

insulin causes these cells to

glucose absorption glucose utilization

blood [glucose]

pancreas

glucagon

released when blood [glucose]is less than ~70 mg/dl

stimulates:breakdown of glycogenbreakdown of triglyceridesproduction of glucose

blood [glucose]

pancreas

100 keys (pg. 620)

“The pancreatic islets release insulin and glucagon. Insulin is released when blood glucose levels rise, and it stimulates glucose transport into, and utilization by, peripheral tissues.

Glucagon is released when blood glucose levels decline, and it stimulates glycogen breakdown, glucose synthesis and fatty acid release.”

the “other” diabetes

diabetes insipidus

diabetes mellitusflow-through sweet

What would make the urine sweet?

Why would glucose be in the urine?

diabetes mellituscauses

•genetic

•pathological conditions•injury•immune disorder•hormonal abnormality

mutations leading tolow insulin productionabnormal insulindefective receptors

diabetes mellitustypes

•type 1insulin dependent (juvenile onset)

controlled by insulin injections

•type 2insulin independent (adult onset)

controlled by diet/lifestyle

diabetes mellitus

abnormally high blood [glucose](hyperglycemia)

so much glucose in the glomerular filtrate, that PCT can’t reabsorb it all…

(transport proteins are saturated)

… so some ends up in the urineglycosuriapolyuria

diabetes mellitus

health problems

much of the body thinks it is “starving”

diabetic retinopathydiabetic neuropathy risk of MI (3x-5x)

other vascular problems

other endocrine organs

intestinesgonadskidneys

adipose, thymus, heart

digestive hormonesreproductive hormonesEPO, renin