Chapter 45: Endocrine System

Learning Targets

1. I can idnetify and explain the role that hormones have in homeostatic pathways. I can diagram how hormones bind to tarfet receptors and trigger

specific pathways. I can explain one hormone that displays positive feedback and one

that displays negative feedback.

2. I can explain how steriod and peptide hormones differ as ligands in signal transduction pathways.

3. I can explain the significance of having antagonistic hormones to maintain homeostasis.

Steroid vs. water soluble hormones

Figure 45.21

Spinal cord(cross section)

(a) (b) Long-term stress responseand the adrenal cortex

Short-term stress responseand the adrenal medulla

Stress

Nervesignals

Nervecell

Releasinghormone

Hypothalamus

Anterior pituitary

Blood vessel

Nerve cell ACTHAdrenal medullasecretes epinephrineand norepinephrine.

Adrenalgland

Kidney

Adrenal cortexsecretes mineralo-corticoids andglucocorticoids.

Effects of epinephrine and norepinephrine: Effects of mineralocorticoids:

Effects of glucocorticoids:

• 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

• 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

Figure 45.7-2

Epinephrine

G protein

Adenylylcyclase

G protein-coupledreceptor

GTP

ATP

cAMP Secondmessenger

Inhibition ofglycogen synthesis

Promotion ofglycogen breakdown

Proteinkinase A

Figure 45.9 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 45.11Pathway 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 45.16

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.UN04