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Chapter 11

Lecture Outline

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I. Endocrine Glands and

Hormones

A. Endocrine Glands

1. Ductless

2. Secrete hormones into the blood

3. Hormones are carried to target cells having

receptors for those hormones.

4. Many organs secrete hormones other than those

discussed in this chapter such as the heart, liver,

kidneys, and adipose tissue.

5. Neurohormones are secreted by specialized cells

of the hypothalamus

6. Hormones help regulate body metabolism,

growth, and reproduction

Major Endocrine Glands


(b)(a)

Testis

Pancreatic islet

(of Langerhans)

Pineal gland

HypothalamusPituitary

glandThyroid gland

Adrenal gland

Pancreas

Ovary

b: © Ed Reschke

Partial Listing of Endocrine Glands

B. Chemical Classification of Hormones

1. ______, derived from tyrosine and tryptophan

a. Examples: hormones from the adrenal

medulla, thyroid, and pineal glands

2. Polypeptides and proteins

a. Examples: antidiuretic hormone, insulin, and

growth hormone

Chemical Classification of Hormones, cont

3. Glycoproteins are long polypeptides bound to a

carbohydrate.

a. Examples: follicle-stimulating and luteinizing

hormones

4. ________ are lipids derived from cholesterol

a. Examples: testosterone, estradiol,

progesterone, cortisol

b. Secreted by adrenal cortex and gonads

Polypeptide & Glycoprotein Hormones

C. Hormone Classifications by action

1. Polar hormones: water soluble

a. Cannot pass through plasma membranes

b. Must be injected if used as a drug

c. Includes polypeptides, glycoproteins,

catecholamines, norepinephrine, and epinephrine

2. Nonpolar: insoluble in water

1. Often called lipophilic hormones

2. Can enter target cells directly

3. Include steroids, thyroid hormone, and melatonin

4. Can be taken orally in pill form

D. Prohormones and Prehormones

1. Prohormones are inactive hormones that must

be cut and spliced together to be active.

a. Example: insulin

2. Prehormones are inactive prohormones that

must be modified within their target cells.

Prohormones and Prehormones

E. Common Aspects of Neural & Endocrine

Regulation

1. Hormones and neurotransmitters both interact

with specific receptors.

2. Binding to a receptor causes a change within the

cell.

3. There are mechanisms to turn off target cell

activity; the signal is either removed or inactivated.

4. Neurotransmitters and hormones have many

similarities

5. Some hormones can also be neurotransmitters in

the CNS

II. Mechanisms of Hormone

Action

Introduction

1. Hormones bind to receptors on or in target cells.

a. Binding is highly specific.

b. Hormones bind to receptors with a high affinity.

c. Hormones bind to receptors with a low

capacity; saturating the receptors with hormone

molecules

2. __________ hormone receptors are in the

cytoplasm or nucleus

3. Water-soluble hormone receptors are on the outer

surface of the plasma membrane

Thyroid Hormone Action

1. _________ (T4) travels to target cells on

thyroxine-binding globulin (TBG).

2. Some T3 is also released, but is not bonded to a

carrier; “free iodine”

3. Inside the target cell, T4 is converted to T3.

4. Receptor proteins are located inside the nucleus

bound to DNA.



1

2

3

4

5

6

7

T4

T4 T4

Protein

synthesis

Thyroid

hormone

response

mRNA

Nucleus

DNA

Receptor

protein

Carrier

protein

(TBG)

Target cellBlood

Binding

protein

mRNA

Cytoplasm

Thyroid Hormone Action, cont

5. The hormone response element on the DNA has

two half-sites, one for a T3 receptor and one for a

9-cis-retinoic acid receptor (a Vit A derivative).

6. Binding of these molecules forms a heterodimer

because there are two different receptors

7. The binding of T3 will cause corepressor proteins

to be removed and coactivator proteins to be

recruited.

8. Vitamin D action in the cell is similar.



T3

TR receptor

(for

triiodothyronine)

RXR receptor

(for 9-cis-

retinoic acid)

9-cis-retinoic

acidTriiodothyronine

Dimerization

Genetic

transcription

Hormone-

response

elementmRNA

DNA

Tyrosine Kinase System

a. Insulin and growth factors uses this system

b. The receptor is also the enzyme tyrosine kinase.

c. The ligand-binding site is on the outside of the

cell, and the enzyme faces the cytoplasm.

d. The enzyme portion is activated via

phosphorylation.

e. The activated receptor phosphorylates insulin

receptor substrate molecules.

f. This activates a cascade of enzymatic activity.

Tyrosine Kinase System

P PP

P

P

1. Binding of insulin to

receptor proteins

2. Phosphorylation of

receptor

3. Phosphorylation of

signal molecules

Extracellular

fluid Insulin

Alpha

Beta

Cytoplasm

Insulin

receptor

Tyrosine kinase now

activeGlucose uptake and

anabolic reactions

Cascade of effects

ADP ADP

ATPATP

ATP

ADP

(a) (b) (c)


III. Pituitary Gland

A. Introduction

1. The pituitary gland is attached to the

hypothalamus by the infundibulum

2. Divided into an anterior lobe (_______________)

and a posterior lobe (neurohypophysis)

a. The anterior pituitary is glandular epithelium

with two parts – pars distalis and pars tuberalis

b. The posterior pituitary is nervous tissue and

also called the pars nervosa

Pituitary Gland


Infundibulum

Posterior lobe

(neurohypophysis)

Hypothalamus

Optic chiasma

Anterior lobe

(adenohypophysis):

Pars tuberalis

Pars distalis

Pars

intermedia

(fetus only)

B. Pituitary Hormones

1. Secreted by the anterior lobe

2. Trophic hormones stimulate hormone secretion in

other glands:

a. Growth hormone (GH)

b. Thyroid-stimulating hormone (TSH)

c. Adrenocorticotropic hormone (ACTH)

d. Follicle-stimulating hormone (FSH)

e. Luteinizing hormone (LH) – in the male, it is

interstitial cell stimulating hormone (ICSH)

f. Prolactin (PRL)

Anterior Pituitary Hormones

Anterior Pituitary Hormones


Thyroid

Adrenal cortex

TestisOvary

FSH

LH

Gonadotropins

Growth

hormone

Bone Muscle

Adipose

tissue

Mammary gland

Prolactin

TSH

ACTH

Posterior pituitary

Infundibulum

Hypothalamus

Paraventricular nucleus

Supraoptic nucleus

Median eminence

Portal system

Anterior pituitary

3. Posterior Pituitary Hormones

a. Stores and releases two hormones made in the

hypothalamus:

1) Antidiuretic hormone (ADH), which promotes

the retention of water in the kidneys (also

called arginine vasopressin – AVP)

2) ________, which stimulates contractions in

childbirth and milk let-down in lactation

C. Hypothalamic Control of the Posterior Pituitary

1. ADH and oxytocin are produced by the

supraoptic and paraventricular nuclei of the

hypothalamus, respectively

2. They are transported along axons of the

hypothalamo-hypophyseal tract to the posterior

pituitary where they are stored.

3. Release is controlled by neuroendocrine reflexes.

a. ADH is stimulated by an increase in blood

osmolality

b. Oxytocin is stimulated by suckling

Hypothalamic Control of the Posterior Pituitary

ADH and oxytocin

produced here

Hypothalamus

Infundibulum

Hypothalamo-

hypophyseal

tract

Posterior pituitary

ADH and

oxytocin

released

Anterior

pituitary

Optic chiasma

Supraoptic

nucleus

Paraventricular

nucleus


D. Hypothalamic Control of the Anterior Pituitary

1. The anterior pituitary

is controlled via

releasing and

inhibiting hormones

transported through

the hypothalamo-

hypophyseal portal

system.


Cell body

Median

eminence

Pituitary stalk

Posterior pituitary

Anterior

pituitary

hormonesAnterior

pituitary

Secondary

capillaries

Releasing

hormones

Portal venules

Primary

capillaries

Axons to primary

capillaries

Hypothalamic Control of Anterior Pituitary, cont

2. Releasing and inhibiting hormones

a. Corticotropin-releasing hormone (CRH)

b. Gonadotropin-releasing hormone (GRH)

c. Prolactin-inhibiting hormone (PIH) (dopamine)

d. Somatostatin

e. Thyrotropin-releasing hormone (TRH)

f. Growth hormone−releasing hormone (GHRH)

Hypothalamic Control of Anterior Pituitary

E. Feedback control of the anterior pituitary

1. The final product regulates secretion of pituitary

hormones – negative feedback inhibition

2. The relationship between the hypothalamus,

anterior pituitary,, and the target tissue is called an

axis

3. Inhibition can occur at the pituitary gland level,

inhibiting response to hypothalamic hormones.

4. Inhibition can occur at the hypothalamus level,

inhibiting secretion of releasing hormones.

Feedback Control of the Anterior Pituitary


Inhibits

responsiveness

to TRH

–

–

Inhibits

secretion

of TRH

ThyroxineThyroidGrowth

of thyroid

Hypothalamus

Thyrotropin-

releasing

hormone

(TRH)

Anterior

pituitary

Thyroid-

stimulating

hormone

(TSH)

Sensor

Integrating center

Effector

Feedback Control of the Anterior Pituitary


–

–

Sex steroid

hormones

(estrogens and

androgens)

Inhibits

responsiveness

to

GnRH

Inhibits

secretion

of GnRH

Negative

feedback

Negative

feedback

Gonadotropin-

releasing hormone

(GnRH)

Anterior

pituitary

Gonadotropins

(FSH and LH)

Gonads

Hypothalamus

Sensor

Integrating center

Effector

F. Higher Brain Controls

1. Since the hypothalamus receives input from

higher brain regions, emotions can alter hormone

secretion.

a. At least 26 brain regions and olfactory neurons

send axons to the GnRH-producing neurons.

b. Stressors increase CRH production as part of

the pituitary-adrenal axis

c. Circadian rhythms

IV. Adrenal Glands

A. Structure of the Adrenal Glands

1. Found atop the kidneys

2. Consist of an outer adrenal cortex and an inner

adrenal medulla that function as separate glands

a. The adrenal medulla is neural tissue and

secretes epinephrine and norepinephrine in

response to sympathetic neural stimulation.

b. The adrenal cortex is glandular epithelium and

secretes steroid hormones in response to

ACTH; three layers – zona glomerulosa, zona

fasciculata, and zona reticularis

Adrenal Glands


Adrenal gland

Kidney

Adrenal

cortex

Adrenal

medulla

Conective

tissue

capsule

Adrenal

cortex

Adrenal

medulla

Zona glomerulosa

Zona fasciculata

Zona reticularis

B. Functions of the adrenal cortex

1. Secretes hormones made from cholesterol; called

corticoseroids or corticoids

2. Three categories:

a. Mineralocorticoids from the zona glomerulosa

regulate Na+ and K+ balance.

1) Example: aldosterone

b. _______________ from the zona fasciculata

regulate glucose metabolism.

1) Example: cortisol

c. Adrenal androgens from the zona reticularis

are weak sex hormones that supplement those

made in the gonads. Ex - DHEA

a. Stimulates protein degradation

b. Stimulates gluconeogenesis and inhibits

glucose utilization to raise blood glucose levels

c. Stimulates lipolysis

4. Exogenous glucocorticoids are used medically to

suppress immune response and inhibit

inflammation; can have many negative side

effects

3. Functions of cortisol (hydrocortisone)

Steroid Hormones of the Adrenal Cortex


Zona fasciculata and zona reticularisZona glomerulosa

Cholesterol

Pregnenolone

Progesterone

Deoxycorticosterone

Corticosterone

Aldosterone

Mineralo-

corticoids

Cholesterol

Pregnenolone

Progesterone

Deoxycorticosterone

Corticosterone

Glucocorticoids Sex steroids

17-Hydroxypregnenolone

17-Hydroxyprogesterone

Deoxycortisol

Cortisol

Dehydroepiandrosterone

(DHEA)

Androstenedione

Other androgens

C. Functions of the Adrenal Medulla

1. Epinephrine and norepinephrine

a. Activated with sympathetic response

b. Have effects similar to sympathetic innervation

but lasting 10 times longer

c. Increase cardiac output, respiratory rate, and

mental alertness; dilate coronary blood vessels;

elevate metabolic rates

2. Stress and the Adrenal Gland

a. Stress increases secretion of ACTH, which results

in increased glucocorticoid release.

b. The stress hormones are glucocorticoids,

epinephrine, and CRH

c. Called the general adaptation syndrome (GAS).

1) Good for proper recovery after stress, such as

an illness or trauma.

2) Cortisol helps inhibit the immune system so it

does not overrespond.

Stress and the Adrenal Gland, cont

d. Chronic stress leads to an increased risk of

illness.

1) Cortisol may act on higher brain regions,

contributing to depression and anxiety and

memory.

2) By stimulating the liver to release glucose,

insulin receptors may become resistant,

making it harder to treat people with

diabetes.

e. Stages of GAS

1) Alarm reaction – activates the adrenal glands

2) Stage of resistance – readjustments in

response

3) Stage of exhaustion – may lead to sickness or

death

f. GAS effects

1) Stimulates growth of adrenal glands

2) Atrophy of lymphatic tissue of spleen, lymph

nodes, and thymus

3) Formation of bleeding peptic ulcers

Activation of pituitary-adrenal axis by nonspecific

stress


–

–

Sensor

Integrating center

Effector

Nonspecific stressHigher

brain centers

Hypothalamus

CRH

Anterior

pituitary

ACTHAdrenal

cortex

Cortisol

Negative

feedback

V. Thyroid and Parathyroid

Glands

A. Thyroid Gland Structure

1. Located just below the

larynx

2. Has two lobes on

either side of the

trachea, connected by

the isthmus


Thyroid

cartilage

of larynx

Cricoid

cartilage

of larynx

Thyroid

gland

Trachea

3. Microscopic Thyroid Gland Structure

a. Consists of hollow spaces called thyroid follicles

lined with simple cuboidal epithelium composed

of follicular cells that produce thyroxine

1. Interior of the follicles is filled with a fluid called

colloid.

2. Outside of the follicles are parafollicular cells that

secrete calcitonin

Photomicrograph of the Thyroid Gland


Follicular

cells

FolliclesColloid

© Ed Reschke

B. Production & Action of Thyroid Hormone

1. Thyroglobulin is made by the follicular cells.

a. Thyroid follicles actively accumulate iodide (I-)

and secrete it into the colloid.

b. The iodine is attached to tyrosines within the

thyroglobulin molecule.

1) One iodine produces monoiodotyrosine

(MIT).

2) Two iodines produce diiodotyrosine (DIT).

Production & Action of Thyroid Hormone, cont

c. Enzymes within the colloid attach MIT and DIT

together:

1) DIT + DIT = T4 (tetraiodothyronine or thyroxine)

2) DIT + MIT = T3 (triiodothyronine)

d. These are still bound to thyroglobulin.

1) They dissociate from thyroglobulin when the

thyroid gland is stimulated by TSH.

2) Secreted into the blood

Production & Storage of Thyroid Hormone


T3

T4

+I–

Thyroid

hormone

secretion

Plasma

carrier

protein

Thyroid

uptake of

iodide

Blood plasma

I–

(Iodide in

plasma)

Colloid

DIT + DIT

Tetraiodothyronine

(T4)

Thyroid follicle

Monoiodotyrosine

(MIT)

Diiodotyrosine

(DIT)

MIT + DIT

Thyroglobulin

Oxidized

iodidePeroxidase

H2O2

Bound to

thyroglobulin

Triiodothyronine

(T4)

2. Action of Thyroid Hormone

a. Stimulates protein synthesis

b. Promotes maturation of the nervous system

c. Increases rates of cellular respiration

d. Elevates basal metabolic rate

C. Calcitonin

1. Made by the parafollicular cells

2. Inhibits dissolution of calcium from bone and

stimulates excretion of calcium in the kidneys to

lower blood calcium levels

D. Diseases of the Thyroid

1. Iodine deficiency leads to overstimulation of the

thyroid gland (no negative feedback on pituitary

gland) and growth of a goiter.

2. It also leads to hypothyroidism: low metabolic

rates, weight gain and lethargy, poor adaptation

to cold stress, and myxedema (accumulation of

fluids in subcutaneous connective tissues).

3. Grave’s Disease – hyperthyroidism

4. Cretinism results from hypothyroidism during

pregnancy to about 6 months after birth

Comparing Hyperthyroidism & Hypothyroidism

How iodine deficiency causes a goiter

SensorIntegrating center

EffectorHypothalamus

TRH

Anterior

pituitary

TSH

Thyroid

If iodine

adequateIf iodine

inadequateT3 and T4

Low

T3 and T4

Normal

thyroid

Low negative

feedback

Anterior

pituitary

Excess TSH

Thyroid

Hypertrophy–

produces goiter

Growth

(goiter)

Negative

feedback

–

–


Endemic goiter caused by low iodine

Symptoms of Hyperthyroidism

E. Parathyroid Glands

1. Generally 4 glands embedded in the back of the

thyroid glandCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Pharynx

Thyroid gland

Parathyroid

glands

Esophagus

Trachea

Parathyroid Glands, cont

2. Secrete parathyroid

hormone (PTH)

3. Hormone promotes a

rise in blood calcium

by acting on bones,

kidneys, and intestine


–

Sensor

Integrating center

Effector

Decreasing blood

Ca2+

Parathyroids

Parathyroid

hormone

Kidneys Bone

Reabsorption

of Ca2+

Negative

feedback

Dissolution of

CaPO4 crystals

Increased blood

Ca2+

Decreased urinary

excretion of Ca2+

VI. Pancreas and Other

Endocrine Glands

A. Pancreas

1. The pancreas is both an endocrine and an

exocrine gland.

2. Endocrine cells are located in pancreatic islets

(islets of Langerhans).

a. Alpha cells: glucagon

b. Beta cells: insulin

Pancreas


Pancreatic islet

(of Langerhans)

Beta cell

Alpha cell

Tail of pancreas

Celiac

arteryAorta

Gallbladder

Common bile duct

Pancreatic duct

Duodenum

Body of pancreas

3. Insulin

a. Primary hormone regulating plasma glucose

concentration.

b. Insulin is secreted by beta cells when blood

glucose levels rise after a sugary or carbohydrate

meal.

c. Its purpose is to lower blood glucose levels to the

“normal” range.

d. Action of Insulin

1) Insulin binds to receptors on target cells.

a) Vesicles with GLUT4 carrier proteins bind to

membrane.

b) Glucose diffuses through GLUT4 channels by

facilitated diffusion

c) Occurs in adipose tissue, skeletal muscle, and

the liver.

2) Indirectly stimulates the enzyme glycogen

synthase in liver and skeletal muscles to promote

sugar storage

3) Stimulates adipose tissue to store fat

Action of Insulin


4

4

Insulin

receptor

Insulin

Translocation

Vesicles

Glucose

GLUT4

Signaling

molecules

Tra

nslo

ca

tion

2

P

1

3

3

4. Glucagon

a. Antagonistic to insulin

b. Secreted by alpha cells when blood glucose

levels are low

c. Purpose is to raise blood glucose levels to a

“normal” range

d. Action of Glucagon

1) Stimulates liver to hydrolyze glycogen into glucose

and release it into the blood

2) Stimulates gluconeogenesis, conversion of

noncarbohydrates into glucose

3) Stimulates lipolysis in adipose tissue so fat is

released and used as a fuel source instead of

glucose

Glucose Homeostasis


–

–

Blood Pancreatic islets

Glucose

in plasma

Glucagon

Insulin

Gluconeogenesis

Glycogenolysis

Cellular uptake

of glucose

Cellular uptake

and utilization

of glucose

Glucagon

Insulin

EffectorIntegrating centerSensor

Blood

Glucose

in plasma

Glucose

in plasma

β cells

Pancreatic islets

α cells

(b)(a)

Glucose

in plasma

β cells

α cells

B. Pineal Gland

1. Located on roof of third ventricle in the brain

2. Secretes the hormone melatonin

3. Regulated by the suprachiasmatic nucleus of the

hypothalamus through sympathetic neurons

a. Stimulates melatonin production when it gets

dark

b. Part of the regulation of circadian rhythms

c. Requires melanopsin found in the ganglion

cells of the retina

d. Secretion related to puberty, jet lag, and

seasonal affective disorder

Secretion of Melatonin


H

C

H

H

C

H

H

N

O

C

N

H

Pineal

gland

Sympathetic

neurons

Superior cervical

ganglion

Retinohypothalamic

tract

Suprachiasmatic

nucleus (the

"biological clock")

Stimulation

Inhibition

Day

Night

Melatonin

CH3CH3O

C. Other Endocrine Glands

1. Gastrointestinal tract: Several hormones are

made in the stomach and small intestine to

regulate digestive processes; includes gastrin,

secretin, cholecystokinin

2. Gonads: Produce testosterone, estrogen, and

progesterone to regulate production of gametes

and secondary sexual characteristics

3. Placenta: produces human chorionic gonadotropin

(hCG) and samatomammotropin to regulate

pregnancy

See separate PowerPoint slides for all figures and tables pre …streaming.missioncollege.org/jcabanilla/media/BIOSC_048... · 2015-07-20 · Chapter 11 Lecture Outline See separate

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