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).