copyright © 2009 pearson education, inc. the nature of chemical regulation

Copyright © 2009 Pearson Education, Inc.

THE NATURE OF CHEMICAL REGULATION


26.1 Chemical signals coordinate body functions

The endocrine system

– Consists of all hormone-secreting cells

– Works with nervous system to regulate body activities



The nervous system also

– Communicates

– Regulates

– Uses electrical signals via nerve cells



Comparing the endocrine and nervous systems

– Nervous system reacts faster

– Endocrine system responses last longer



Hormones

– Chemical signals

– Usually carried in the blood

– Cause specific changes in target cells

– Secreted by

– Endocrine glands

– Neurosecretory cells

Secretoryvesicles

Targetcell

Bloodvessel

Hormonemolecules

Endocrine cell

Hormonemolecules

Targetcell

Bloodvessel

Neurosecretorycell

Neurotransmittermolecules

Nervecell

Nervecell

Nervesignals


26.2 Hormones affect target cells by two main signaling mechanisms

Hormone signaling involves three key events

– Reception

– Signal Transduction

– Response



Amino-acid-derived hormones

– Are water-soluble

– Include proteins, peptides, and amines

– Bind to plasma-membrane receptors on target cells

– Initiate a signal transduction pathway

Animation: Water-Soluble Hormone

Plasmamembrane

Receptorprotein

Water-solublehormone(epinephrine) 1

Targetcell

Plasmamembrane

Receptorprotein

Water-solublehormone(epinephrine)

2

Signaltransductionpathway

Relaymolecules

1

Targetcell

Plasmamembrane

Receptorprotein

Targetcell

Water-solublehormone(epinephrine) 1

2


Relaymolecules

Glycogen Glucose

Cellular response(in this example, glycogen breakdown)

3



Steroid hormones

– Nonpolar lipids made from cholesterol

– Can diffuse through plasma membranes

– Bind to a receptor protein in the cytoplasm or nucleus

– Hormone-receptor complex carries out the transduction of the hormonal signal

Animation: Lipid-Soluble Hormone

Lipid-solublehormone(testosterone)

Targetcell

Nucleus

1

Lipid-solublehormone(testosterone) 1

Targetcell

Nucleus

Receptorprotein

2


Targetcell

Nucleus

Receptorprotein

2

DNA

Hormone-receptorcomplex

3


Targetcell

Nucleus

Receptorprotein

2

DNA


3

mRNATranscription

Newprotein

Cellular response:activation of a gene andsynthesis of new protein

4

New protein

Cellular response

mRNA

DNA


Receptorprotein

Lipid-solublehormone

Water-solublehormone

Receptorprotein



THE VERTEBRATE ENDOCRINE SYSTEM


26.3 Overview: The vertebrate endocrine system consists of more than a dozen major glands

The vertebrate endocrine system

– Consists of more than a dozen glands

– Secretes more than 50 hormones


Glands– Some are specialized for hormone secretion only

– Some also do other jobs


Hypothalamus

Parathyroid glands

Pineal glandPituitary gland

Thyroid gland

Thymus

Adrenal glands(atop kidneys)

Pancreas

Ovary(female)

Testes(male)


Hormones

– Some have a very narrow range of targets and effects

– Some have numerous effects on many kinds of target cells



26.4 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems

The hypothalamus

– Blurs the distinction between endocrine and nervous systems

– Receives input from nerves about body conditions

– Responds by sending out appropriate nervous or endocrine signals

– Uses the pituitary gland to exert master control over the endocrine system



The pituitary gland consists of two parts

– Posterior pituitary

– Composed of nervous tissue

– Stores and secretes oxytocin and ADH

Brain

Hypothalamus

Posterior pituitary

Anterior pituitary

(Bone)

Hypothalamus

Posteriorpituitary

Anteriorpituitary

Hormone Neurosecretorycell

Bloodvessel

Oxytocin ADH

Kidney tubulesUterine musclesMammary glands



Anterior pituitary

– Synthesizes and secretes hormones that control the activity of other glands

– Is controlled by the hypothalamus

– Releasing hormones stimulate the anterior pituitary

– Inhibiting hormones inhibit the anterior pituitary

Endocrine cells ofthe anterior pituitary

Pituitary hormones

Releasing hormonesfrom hypothalamus

Neurosecretorycell

Bloodvessel

FSHandLH

TSH ACTH Prolactin(PRL)

Growthhormone

(GH)

Endorphins

Thyroid Adrenalcortex

Testes orovaries

Mammaryglands

(in mammals)

Entirebody

Painreceptors

in the brain


HORMONES AND HOMEOSTASIS


26.5 The thyroid regulates development and metabolism

Thyroid gland hormones

– Thyroxine (T4) and triiodothyronine (T3)

– Regulate

– Metabolism

– Development

– Negative feedback

– Maintain homeostatic levels of T4 and T3 in the blood

TSH

TRH

Hypothalamus

Anteriorpituitary

Thyroid

Thyroxine

Inhibition

Inhibition


26.5 The thyroid regulates development and metabolism

Thyroid imbalance can cause disease

– Hyperthyroidism

– Too much T4 and T3 in the blood

– Leads to high blood pressure, loss of weight, overheating, and irritability

– Produces Graves’ disease

– Hypothyroidism

– Too little T4 and T3 in the blood

– Leads to low blood pressure, overweight, often cold, lethargy

No inhibition

No iodine

No inhibition

InsufficientT4 and T3

produced

Hypothalamus

Anteriorpituitary

Thyroid

Thyroid grows to form goiter

TRH

TSH


26.6 Hormones from the thyroid and parathyroids maintain calcium homeostasis

Blood calcium level is regulated by a tightly balanced antagonism between

– Calcitonin from the thyroid

– Parathyroid hormone (PTH) from the parathyroid glands

Calcitonin87

6

5

4

3 2

1

9

Thyroidglandreleasescalcitonin

Stimulus:Rising

blood Ca2+

level(imbalance)

Blood Ca2+ rises

Ca2+

level

Ca2+

level

Homeostasis: Normal bloodcalcium level (about 10 mg/100 mL)

Stimulus:Falling

blood Ca2+

level(imbalance)

Blood Ca2+ falls

Stimulates

Ca2+ depositionin bones

Reduces

Ca2+ uptakein kidneys

PTH

Stimulates

Ca2+ releasefrom bones

Increases

Ca2+ uptakein intestines

Activevitamin D

Increases

Ca2+ uptakein kidneys

Parathyroidglandsrelease parathyroidhormone (PTH)

Parathyroidgland


26.7 Pancreatic hormones regulate blood glucose levels

The pancreas secretes two hormones that control blood glucose

– Insulin—signals cells to use and store glucose

– Glucagon—causes cells to release stored glucose into the blood

Insulin

4Beta cellsof pancreas stimulatedto release insulin intothe blood

Glucoselevel

Homeostasis: Normal blood glucose level(about 90 mg/100 mL)

Glucoselevel

Glucagon

Low bloodglucose level

High bloodglucose level

Bodycellstake up moreglucose

Blood glucose leveldeclines to a set point;stimulus for insulinrelease diminishes

Liver takesup glucoseand stores it asglycogen

Alphacells ofpancreas stimulatedto release glucagoninto the blood

Stimulus:Declining bloodglucose level(e.g., afterskipping a meal)

Stimulus:Rising blood glucoselevel (e.g., after eatinga carbohydrate-richmeal)

Blood glucose levelrises to set point;stimulus for glucagonrelease diminishes

Liverbreaks downglycogen andreleases glucoseto the blood

7

6

1

2

5

8

3


26.8 CONNECTION: Diabetes is a common endocrine disorder

Diabetes mellitus

– Results from

– A lack of insulin or

– A failure of cells to respond to it

– Affects about 21 million Americans


26.8 CONNECTION: Diabetes is a common endocrine disorder

Two common types of diabetes mellitus

– Type 1 (insulin-dependent)

– Autoimmune disease

– Insulin-producing cells destroyed

– Type 2 (non-insulin-dependent)

– Deficiency of insulin

– More commonly, reduced response to insulin

– More than 90% of diabetics are type 2

– Associated with being overweight and underactive

Blo

od

glu

cose

(m

g/1

00 m

L)

Hours after glucose ingestion

Normal

400

Diabetic300

250

200

150

100

50

00

350

1 2 3 4 512


26.9 The adrenal glands mobilize responses to stress

Hormones from the adrenal glands help maintain homeostasis when the body is stressed



Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete

– Epinephrine

– Norepinephrine

These hormones quickly trigger the fight-or-flight responses



Adrenocorticotropic hormone (ACTH) from the pituitary causes the adrenal cortex to secrete

– Glucocorticoids

– Mineralocorticoids

These hormones

– Boost blood pressure

– Boost energy in response to long-term stress

Hypothalamus

Stress

Releasing hormone

Blood vessel

Anterior pituitary

Adrenal cortexACTH

Nervecell

Nerve cell

Adrenal medulla

3

4

5

2

Nervesignals

AdrenalmedullaAdrenal

gland

Adrenalcortex

Kidney

Spinal cord(cross section)

Epinephrine andnorepinephrine

Mineralocorticoids Glucocorticoids

ACTH

1

Long-term stress responseShort-term stress response

Short-term stress response

1. Glycogen broken down to glucose; increased blood glucose2. Increased blood pressure3. Increased breathing rate4. Increased metabolic rate5. Change in blood-flow patterns, leading to increased alertness and decreased digestive and kidney activity

Long-term stress response

Mineralocorticoids Glucocorticoids

2. Increased blood volume and blood pressure

1. Retention of sodium ions and water by kidneys

2. Immune system may be suppressed

1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose


26.10 The gonads secrete sex hormones

Steroid sex hormones

– Include estrogens, progestins, and androgens

– Produced by the gonads in response to signals from

– Hypothalamus

– Pituitary



Estrogens and progestins

– Stimulate the development of female characteristics

– Maintain the female reproductive system



Androgens

– Such as testosterone

– Trigger the development of male characteristics


26.11 EVOLUTION CONNECTION: A single hormone can perform a variety of functions in different animals

Prolactin in humans

– Stimulates mammary glands to grow and produce milk during late pregnancy

– Suckling by a newborn stimulates further release of prolactin

– High prolactin during nursing inhibits ovulation


Prolactin

– Nonhuman mammals—stimulates nest building

– Birds—regulates fat metabolism and reproduction

– Amphibians—movement to water

– Fish—migration between salt and fresh water

26.11 EVOLUTION CONNECTION: A single hormone can perform a variety of functions in different animals


Introduction: Gender Benders

Endocrine disruptors

– Environmental pollutants

– Interfere with the action of hormones

– Some are estrogen mimics in the environment that may produce

– Demasculinized male alligators

– Bass with male and female characteristics

– Decrease in size and functioning of polar bear genitalia


You should now be able to

1. Explain how endocrine disruptors are causing environmental problems

2. Compare the mechanisms and functions of the endocrine and nervous systems

3. Distinguish between the two major classes of vertebrate hormones

4. Describe the different types and functions of vertebrate endocrine organs



5. Describe the interrelationships between the hypothalamus and pituitary glands

6. Describe the functions of the thyroid and parathyroid glands

7. Explain how insulin and glucagon manage blood glucose levels

8. Describe the causes and symptoms of types 1 and 2 diabetes



9. Compare the functions of the adrenal gland hormones

10. Describe the three major types of sex hormones and their functions

11. Describe the diverse functions of prolactin in vertebrate groups

Posterior pituitary:Composed of nervous tissue;stores and secretes hormonesmade by hypothalamus

Brain Hypothalamus:Master controlcenter of theendocrine system

Anterior pituitary:Composed ofendocrine tissue;controlled byhypothalamus;produces andsecretes itsown hormones

Pineal gland

e. regulates metabolismf. related to daily rhythmg. raises blood calcium levelsh. boosts water retention

Parathyroid gland

Hypothalamus

a. lowers blood glucoseb. stimulates ovariesc. triggers fight-or-flightd. promotes male traits

Anterior pituitary

Testes

Adrenal medulla

Pancreas

Thyroid gland

4. insulin5. melatonin6. FSH

1. thyroxine2. epinephrine3. androgens

7. PTH8. ADH

copyright © 2009 pearson education, inc. the nature of chemical regulation

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