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Endocrine System
Figure 45.2a
(a) Endocrine signaling
Bloodvessel Response
Response
Response
(b) Paracrine signaling
(c) Autocrine signaling
Figure 45.2b
Synapse
Response
Response
Neuron
(d) Synaptic signaling
Neurosecretorycell
Bloodvessel
(e) Neuroendocrine signaling
Figure 45.4Major endocrine glands:
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands(behind thyroid)
Adrenal glands(atop kidneys)
Pancreas
Ovaries (female)
Testes (male)
Organs containingendocrine cells:
Thymus
Heart
Liver
Stomach
Kidneys
Smallintestine
Figure 45.14
Pinealgland
Cerebellum
Spinal cord
Cerebrum
Thalamus
Hypothalamus
Pituitarygland
Posteriorpituitary
Anteriorpituitary
Hypothalamus
Figure 45.5
Lipid-soluble (hydrophobic)Water-soluble (hydrophilic)
Polypeptides Steroids
0.8 nmInsulin Cortisol
Amines
Epinephrine Thyroxine
Figure 45.6-2
Lipid-solublehormone
SECRETORYCELL
Water-solublehormone
VIABLOOD
Signal receptor
TARGETCELL
OR
Cytoplasmicresponse Gene
regulation
(a) (b)
Cytoplasmicresponse Gene
regulation
Signalreceptor
Transportprotein
NUCLEUS
Figure 45.7-2
Epinephrine
G protein
Adenylylcyclase
G protein-coupledreceptor
GTP
ATP
cAMP Secondmessenger
Inhibition ofglycogen synthesis
Promotion ofglycogen breakdown
Proteinkinase A
Figure 45.8-2
EXTRACELLULARFLUID
Hormone(estradiol)
Estradiol(estrogen)receptor Plasma
membrane
Hormone-receptorcomplex
NUCLEUS
DNA
CYTOPLASM
VitellogeninmRNA
for vitellogenin
Different receptorsSame receptors but differentintracellular proteins (not shown)
Different cellularresponses
Different cellularresponses
Epinephrine Epinephrine Epinephrine
receptor receptor receptor
Glycogendeposits
Vesseldilates.
Vesselconstricts.
Glycogenbreaks downand glucoseis releasedfrom cell.
(a) Liver cell (b) Skeletal muscleblood vessel
Intestinal bloodvessel
(c)
Figure 45.9
Figure 45.11Pathway Example
Stimulus Low pH in
duodenum
Endocrinecell
S cells of duodenumsecrete the hormonesecretin ( ).
Hormone
Bloodvessel
Targetcells
Pancreas
Response Bicarbonate release
Neg
ativ
e fe
edb
ack
Figure 45.12Pathway
Example
Stimulus Suckling
Sensoryneuron
Po
siti
ve f
eed
bac
k
Hypothalamus/posterior pituitary
Neurosecretory cell
Neurohormone
Blood vessel
Targetcells
Response
Posterior pituitarysecretes theneurohormoneoxytocin ( ).
Smooth muscle inbreasts
Milk release
Figure 45.14
Pinealgland
Cerebellum
Spinal cord
Cerebrum
Thalamus
Hypothalamus
Pituitarygland
Posteriorpituitary
Anteriorpituitary
Hypothalamus
Figure 45.16
Tropic effects only:FSHLHTSHACTH
Nontropic effects only:ProlactinMSH
Nontropic and tropic effects:GH Hypothalamic
releasing andinhibitinghormones
Posteriorpituitary
Neurosecretorycells of thehypothalamus
Portal vessels
Endocrine cellsof the anteriorpituitary
Pituitaryhormones
HORMONE FSH and LH TSH ACTH Prolactin MSH GH
TARGET Thyroid MelanocytesTestes orovaries
Adrenalcortex
Mammaryglands
Liver, bones,other tissues
Figure 45.15
Neurosecretorycells of thehypothalamus
Neurohormone
Posteriorpituitary
Hypothalamus
Axons
Anteriorpituitary
HORMONE
TARGET
ADH Oxytocin
Kidneytubules
Mammary glands,uterine muscles
Figure 45.17 Pathway Example
Stimulus Cold
Sensory neuron
Hypothalamus
Neurosecretory cell
Releasing hormone
Blood vessel
Anterior pituitary
Tropic hormone
Endocrine cell
Hormone
Targetcells
Response
Ne
ga
tiv
e f
ee
db
ac
k
Hypothalamus secretesthyrotropin-releasinghormone (TRH ).
Anterior pituitary secretesthyroid-stimulatinghormone (TSH, also knownas thyrotropin ).
Thyroid gland secretesthyroid hormone(T3 and T4 ).
Body tissues
Increased cellularmetabolism
Hypothyroidism Goiter
Hyperthyroidism
Figure 45.20-2
Activevitamin D
Increases Ca2
uptake inintestines
Stimulates Ca2
uptake in kidneys
Stimulates Ca2 releasefrom bones
Parathyroidgland (behindthyroid)
PTH
Blood Ca2
level rises.
Homeostasis:Blood Ca2 level
(about 10 mg/100 mL)
STIMULUS:Falling blood
Ca2 level
Rickets
Spinal cord(cross section)
(a) Short-term stress response and the adrenal medulla
Stress
Nervesignals
Nervecell
Nerve cellAdrenal medullasecretes epinephrineand norepinephrine.
Adrenalgland
Kidney
Effects of epinephrine and norepinephrine:
• Glycogen broken down to glucose;increased blood glucose
• Increased blood pressure• Increased breathing rate• Increased metabolic rate• Change in blood flow patterns, leading to
increased alertness and decreased digestive,excretory, and reproductive system activity
Hypo-thalamus
Figure 45.21a
(b) Long-term stress response and the adrenal cortex
Stress
Releasinghormone
Hypothalamus
Anterior pituitary
Blood vessel
ACTH
Adrenal cortexsecretes mineralo-corticoids andglucocorticoids.
Effects of mineralocorticoids:
Effects of glucocorticoids:
• Retention of sodium ions and water by kidneys
• Increased blood volume and blood pressure
• Proteins and fats broken down and converted to glucose, leading to increased blood glucose
• Partial suppression of immune system
Adrenalgland
Kidney
Figure 45.21b
Figure 45.13
Body cellstake up moreglucose.
Insulin
Beta cells ofpancreasrelease insulininto the blood.
Liver takesup glucose and stores itas glycogen.
Blood glucoselevel declines.
Blood glucoselevel rises.
Homeostasis:Blood glucose level
(70–110 mg/m100mL)
STIMULUS:Blood glucose level rises
(for instance, after eating acarbohydrate-rich meal).
Liver breaksdown glycogenand releasesglucose intothe blood.
Alpha cells of pancreasrelease glucagon intothe blood.
Glucagon
STIMULUS:Blood glucose level
falls (for instance, afterskipping a meal).