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Lecture Presentation by Patty Bostwick-Taylor

Florence-Darlington Technical College

Chapter 9

The Endocrine System

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Introduction

Hormone and Target Cells

Steroids and Non-Steroids

HW: Read / Take notes from text p.308-310

Complete WB 184

Endocrine System

Endocrine vs Nervous Cell Communication

Nervous vs. Endocrine System

Communication:

Electrical impulses

Neurotransmitters

Reaction time

1-10 msec

Stops immediately

Effects

Specific organs

Hormones

Seconds – days

Response lingers

Often entire body

Endocrine System Anatomy

Endocrine glands secrete into blood, lymph

Exocrine glands secrete into ducts

Major Endocrine Organs

Many glands are purely endocrine

Anterior pituitary, thyroid, adrenals, parathyroids

Some glands are mixed glands

endocrine and exocrine functions

pancreas, ovaries, testes

Endocrine System Functions

Regulate metabolic processes

Controls rate of chemical reactions

Helps transport across membranes

Helps regulate water & electrolytes

Regulates glucose and calcium concentrations

Reproduction, development, growth

Mobilization of body defenses

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Endocrine Hormones

Produced by specialized cells (endocrine glands)

Blood transfers hormones to target sites

Hormones regulate activity of other cells

Turns genes on / off

The Chemistry of Hormones (2 types)

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Hormones are classified chemically as

Amino acid–based (non-steroids):

Proteins

Peptides

Amines

Steroids—made from cholesterol

Hormone Action

Hormones alter cellular activity.

Typically, one or more occurs:

1. Membrane permeability or electrical state changes

2. Synthesis of proteins (often enzymes)

3. Enzyme activation or inactivation

4. Stimulation of mitosis (cell division)

5. Promotes cell to secrete substance

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Hormone Action

Hormones affect only certain tissues / organs

(target cells / target organs)

Hormone binding to receptor alters cellular activity

Target cells must have specific protein receptors

On cell membrane OR Inside the cell

Non-Steroid Cell Communication

Second-Messenger System (Nonsteroid Hormone Action)

1. Hormone (1st messenger) binds to membrane receptor

2. Activated receptor sets off a series of reactions

Activates an enzyme

3. Enzyme catalyzes a reaction

Activates second-messenger molecule (cyclic AMP, Ca2+)

4. Additional intracellular changes promote cellular response

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Figure 9.1b Mechanisms of hormone action.

Nonsteroid hormone action

Plasmamembraneof target cell

Receptorprotein

Nonsteroidhormone (firstmessenger)

Cytoplasm

Enzyme

cAMPSecondmessenger

Effect on cellular function

Steroid Cell Communication

Direct Gene Activation (Steroid Hormone Action)

1. Steroid hormones diffuse through plasma membrane

2. Steroid hormones bind to a receptor protein

In the cytoplasm OR

In the nucleus

3. Steroid hormones enter the nucleus

4. Hormone-receptor complex binds DNA

5. Activates genes

6. New proteins are made

Figure 9.1a Mechanisms of hormone action.

Steroidhormone

Cytoplasm Nucleus

Receptorprotein

Hormone-receptorcomplex

Newprotein

Plasmamembraneof targetcell

(a) Steroid hormone action

3 Ways to Stimulate Endocrine Glands

Neural

Hormonal

Humoral

Feedback Mechanisms

Negative

Positive

HW: Read / take notes from text p.310-312

Complete Feedback Mechanisms packet

1. Hormonal 2. Neural 3. Humoral

Endocrine Gland Stimuli

Three categories of stimuli that activate endocrine glands

Hormonal Stimuli of Endocrine Glands

Most common stimulus

Endocrine organs are activated by other hormones

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Hormonal – gland secretion

Hormonal stimulus

The hypothalamus secretes

hormones that… Hypothalamus

…stimulate

the anterior

pituitary

gland to

secrete

hormones

that…

Anteriorpituitarygland

Thyroidgland

Adrenalcortex

Gonad(testis)

…stimulate other endocrine

glands to secrete hormones

Neural Stimuli of Endocrine Glands

Nerve impulses stimulate hormone release

Under sympathetic nervous system control (mostly)

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Figure 9.2c Endocrine gland stimuli.

Neural stimulus

Sympathetic fiber stimulates

adrenal medulla cells

CNS (spinal cord)

Sympathetic fibers

Figure 9.2c Endocrine gland stimuli.

Neural stimulus

Adrenal medulla

cells secrete epinephrine

and norepinephrine

Neural Stimuli Results inRelease of Epinephrine

Increase cardiac output

Dilate coronary blood vessels

Increase muscle contraction

Increase mental alertness

Increase glycogen

Increase blood sugar

Humoral Stimuli of Endocrine Glands

Blood levels of certain ions and nutrients stimulate

hormone release

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Humoral stimulus

Capillary blood contains lowconcentration of Ca2+, whichstimulates…

Capillary

(low Ca2+

in blood)

Thyroid gland(posterior view)

Parathyroid

glands

Parathyroid

glandsPTH

…secretion of parathyroid

hormone (PTH) by parathyroid

glands)

Regulation of Calcium Ion Concentration in Blood

Control of Hormone Release:Negative Feedback Mechanism (usually)

Hormone levels maintained by negative feedback

What triggers the release of more hormone?

A stimulus

Low hormone levels in the blood

What stops the release of hormones?

Hormone reaches appropriate level in the blood

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Negative Feedback Mechanism

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Negative Feedback Mechanism

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Master Controls of the Endocrine System

Hypothalamus

Pituitary GlandPosterior Pituitary Gland (2 hormones)

HW: Read / Take notes from text p. 310-312

Pituitary Gland and Hypothalamus

Pituitary gland is the size of a pea

Hangs by a stalk from the hypothalamus

Protected by the sphenoid bone

Has two functional lobes

Anterior pituitary—glandular tissue

Posterior pituitary—nervous tissue

Called the “master endocrine gland”

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Hypothalamus makes two hormones:

antidiuretic hormone (ADH)

oxytocin

Neurosecretory cells bring

hormones to posterior pituitary

Posterior pituitary is a storage site

Venous drainage

ADH Oxytocin

Arterial blood supply

Posterior Pituitary Stores Hormones

When stimulated

Releases ADH

Releases Oxytocin

Posterior Pituitary - ADH

Antidiuretic hormone (ADH) Prevents dehydration Inhibits urine production (diuresis)

Promotes water reabsorption by the kidneys

Alcohol inhibits ADH secretion Therefore increases water loss

Large amounts of ADH vasoconstriction of arterioles increases blood pressure ADH is also known as vasopressin

ADH hyposecretion results in Diabetes insipidus

Posterior Pituitary - Oxytocin

Oxytocin

Stimulates contractions of the uterus

during labor

sexual relations

breastfeeding

Causes milk ejection (let-down reflex) in a breastfeeding woman

Increases sense of calmness

Pitocin: synthetic oxytocin

Used to induce labor

Used post labor to stop bleeding

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Venous drainage

ADH Oxytocin

Arterial blood supply

Posterior Pituitary

When stimulated

Releases ADH

Prevents water loss

Releases Oxytocin

Uterine contractions

Milk let-down

Increases calmness

Kidney Mammary glandsUterine muscles

Hypothalamus produces releasing / inhibiting hormones

These hormones are released into portal circulation,

which connects hypothalamus to anterior pituitary

Hypothalamus also makes two hormones: oxytocin and

antidiuretic hormone

Carried to posterior pituitary via neurosecretory cells for

storage

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Master Controls of the Endocrine System

Hypothalamus

Pituitary GlandAnterior Pituitary Gland (6 hormones)

HW: Read / Take notes from text p.315-317

Complete WB 181-183

Hormones of the Anterior Pituitary

Six anterior pituitary hormones

Hormonal control

All amino acid-based hormones

Regulated by negative feedback (mostly)

Two affect non-endocrine targets:

1. Growth hormone

Muscles

2. Prolactin

Breast – milk production in females

Unknown function in males

Growth Hormone

General metabolic hormone

Causes amino acids to be built into proteins

Causes fats to be broken down for a source of energy

Plays a role in determining final body size

Growth of skeletal muscles

Growth of long bones

Growth Hormone Disorders

Pituitary dwarfism

hyposecretion of GH

during childhood

Gigantism

hypersecretion of GH

during childhood

Acromegaly

hypersecretion of GH in adulthood

continued growth of hand, feet, and facial bones

Prolactin (PRL)

In females, stimulates and maintains milk production

(after childbirth)

Positive feedback

Function in males is unknown

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Figure 9.5 Hormones of the anterior pituitary and their major target organs.

Mammary

glands

Prolactin (PRL)Bones and muscles

Growth hormone (GH)

Anterior pituitary

Hypothalamus

Four are tropic hormones

stimulate other endocrine glands to release hormones

1. Thyroid-stimulating hormone (TSH)

2. Adrenocorticotropic hormone (ACTH)

3. Follicle-stimulating hormone (FSH)

4. Luteinizing hormone (LH)

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Adrenocorticotropic hormone (ACTH)

Regulates endocrine activity of the adrenal cortex

Thyroid-stimulating hormone (TSH)

Influences growth and activity of the thyroid gland

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Adrenocorticotropic

hormone (ACTH)

Adrenal cortexThyroid stimulating

hormone (TSH)

Thyroid

Hypothalamus

Gonadotropic hormones

Regulate hormonal activity of the gonads

Follicle-stimulating hormone (FSH)

Stimulates follicle development in ovaries

Stimulates sperm development in testes

Luteinizing hormone (LH)

Triggers ovulation of an egg in females

Stimulates testosterone production in males

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Follicle-stimulating

hormone (FSH)

and luteinizing

hormone (LH)

Testes or ovaries

Hypothalamus

Posterior pituitary

Adrenocorticotropic

hormone (ACTH)

Adrenal cortexThyrotropic

hormone (TH)

Thyroid

Follicle-stimulating

hormone (FSH)

and luteinizing

hormone (LH)

Testes or ovaries

Mammary

glands

Prolactin (PRL)Bones and muscles

Growth hormone (GH)

Hypophyseal

portal system

Anterior pituitary

Releasing hormones

secreted into portal

circulation

Hypothalamus

Control of Metabolism and Ca2+ ion concentration

Thyroid (3 hormones)Hormonal stimuliHumoral stimuli

Parathyroid (1 hormone)Humoral stimuli

Copy Figure 9.10 into notes

Thyroid Gland

Found at the base of the throat

Consists of two lobes and a connecting isthmus

Produces two hormones:

1. Thyroid hormone (T3 and T4)

2. Calcitonin

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Figure 9.7a The thyroid gland.

Isthmus of

thyroid gland

Thyroid

cartilage

Common

carotid artery

Trachea

Brachiocephalic

artery

(a) Gross anatomy of the thyroid gland, anterior view

Epiglottis

Left subclavian

artery

Left lobe of

thyroid gland

Thyroid Hormone (1 functional hormone)

Major metabolic hormone

Controls rate of oxidation of glucose

Chemical energy (ATP)

Body heat

Composed of two iodine-containing hormones

Thyroxine (T4)

Triiodothyronine (T3)

converts to T4 at target cells

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Figure 9.7b The thyroid gland.

(b) Photomicrograph of thyroid gland

follicles (380×)

Parafollicular cells

Colloid-filled

follicles Follicle cells

Thyroid Gland

Thyroid hormone disorders

Goiters

Thyroid gland enlarges because of lack of iodine

Salt is iodized to prevent goiters

Cretinism

Caused by hyposecretion of thyroxine

Results in dwarfism during childhood

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Thyroid Gland

Thyroid hormone disorders

Myxedema

Caused by hypothyroidism in adults

Results in physical and mental sluggishness

Graves’ disease

Caused by hyperthyroidism

Results in increased metabolism, heat intolerance,

rapid heartbeat, weight loss, and exophthalmos

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Thyroid Gland

Calcitonin

Decreases blood calcium levels

Causes calcium deposition on bone

Antagonistic to parathyroid hormone

Disorder: Calcinosis

– calcification of soft tissue

Parathyroid Glands

On the posterior of the thyroid

Parathyroid hormone (PTH)

Stimulates osteoclasts

remove calcium from bone

Hypercalcemic hormone ( blood calcium levels)

Stimulates the kidneys and intestine

absorb more calcium

Figure 9.10 Hormonal controls of ionic calcium levels in the blood.

Parathyroid

glands

Thyroid

Parathyroid

glands release

parathyroid

hormone (PTH).PTH

Stimulus

Falling blood

Ca2+ levels

BALANCE

Calcitonin

stimulates

calcium salt

deposit in bone.

Thyroid gland

releases calcitonin.

Calcitonin

BALANCE

Stimulus:

Rising blood

Ca2+ levels

Osteoclasts

degrade bone

matrix and release

Ca2+ into blood.

Calcium homeostasis of blood:

9–11 mg/100 ml

Adrenal Gland (2-in-1)

Adrenal Cortex (3 groups of hormones)

Hormonal stimuli

Humoral stimuli

Adrenal Medulla (2 hormones)

Neural stimuli

Study all glands / hormones covered so far.

Adrenal Glands

Sit on top of the kidneys

Two regions:

Adrenal cortex – hormonal / humoral control

produces 3 corticosteroids

Mineralocorticoids

Glucocorticoids

Sex hormones

Adrenal medulla – neural control

inner neural tissue region

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Figure 9.11 Microscopic structure of the adrenal gland.

Kidney

Adrenal

Adrenal gland• Medulla

• Cortex

Kidney

Cortex

Medulla

Adrenal

cortex

Adrenal

medulla

Sex hormone–

secreting area

Glucocorticoid-

secreting area

Mineralocorticoid-

secreting area

Capsule

Adrenal Cortex Hormones

Mineralocorticoids (mainly aldosterone)

Produced in outer adrenal cortex

Target organ: kidney

Regulate sodium and potassium ion levels in blood

Regulate water and electrolyte balance

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Aldosterone

Increases blood pressure by regulating kidney function

Causes kidney to

Reabsorb sodium

Reabsorb water

Secrete potassium

Release stimulated by:

Humoral stimulation – level of K+ ions in blood

Hormonal stimulation (ACTH – stress hormone)

Inhibited by atrial natriuretic peptide (ANP)

Heart-produced hormone when blood pressure is high

Figure 9.12 Major mechanisms controlling aldosterone release from the adrenal cortex.

Kidney

Decreased Na+ or

increased K+ in

Decreasedblood volumeand/or bloodpressure

Stress

Hypothalamus

Corticotropin-releasinghormone

Anterior pituitary

Increasedblood pressureor blood volume

HeartReninIndirectstimulatingeffect viaangiotensin

Angiotensin II

Atrial natriureticpeptide (ANP)

Inhibitory

effect

Directstimulatingeffect

Mineralocorticoid-producing part ofadrenal cortex

Enhanced secretionof aldosterone targetskidney tubules

Increased absorptionof Na+ and water;increased K+ excretion

Increased blood volume andblood pressure

Glucocorticoids

Cortisone and cortisol

Produced by middle layer of adrenal cortex

Promote normal cell metabolism

Increases blood glucose levels (hyperglycemic)

Helps resist long-term stressors

Anti-inflammatory properties

Released in response to increased ACTH in blood

(hormonal stimulus)

Sex Hormones

Androgens (male sex hormones, ex. testosterone)

Some estrogens produced (female sex hormone)

Produced in the inner layer of the adrenal cortex

Small amounts are made throughout life

Role in male development:

Testes formation (early regulation)

Spermatogenesis

Inhibition of fat deposition

Enlargement of skeletal muscle cells

Sex Hormones – Effects of Testosterone

Adrenal Medulla Hormones

Produces two similar hormones: (catecholamines)

1. Epinephrine (adrenaline)

2. Norepinephrine (noradrenaline)

“Fight or Flight” Hormones

Prepare the body to deal with short-term stress

Increases:

heart rate

blood pressure

blood glucose levels

Dilates small passageways of lungs

Cortex

Medulla

Adrenal

medulla

Sex hormone

Secreting cells

Glucocorticoid

Secreting cells

Mineralocorticoid

Secreting cells

Capsule

Figure 9.13 Roles of the hypothalamus, adrenal medulla, and adrenal cortex in the stress response.

Hypothalamus

Short term More prolonged

Spinal cord

Nerve impulses

PreganglionicsympatheticfibersAdrenal

medulla

Short-term stress response

Catecholamines(epinephrine andnorepinephrine)

1.2.3.

Increased heart rateIncreased blood pressureLiver converts glycogento glucose and releasesglucose to bloodDilation of bronchiolesChanges in blood flowpatterns, leading toincreased alertness anddecreased digestive andkidney activityIncreased metabolic rate

Stress

Releasing hormones

Corticotropic cells of

anterior pituitary

ACTHAdrenal

cortex

Mineralocorticoids Glucocorticoids

Long-term stress response

Retention of sodiumand water by kidneysIncreased bloodvolume and bloodpressure

Proteins and fatsconverted toglucose or brokendown for energyIncreased bloodsugarSuppression ofimmune system

Regulation of Blood Glucose Levels

Pancreas (hidden Islets of Langerhans)

Pancreatic Islets (2 hormones)

Humoral stimuli

Beta cells

Alpha cells

Complete Blood Glucose handout.

Pancreatic Islets

Pancreas

Located in the abdomen, close to stomach

Mixed gland, with both endocrine and exocrine

functions

The pancreatic islets produce hormones

Insulin—produced by beta cells

Glucagon—produced by alpha cells

These hormones are antagonists that maintain blood

sugar homeostasis

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Figure 9.14a Pancreatic tissue.

Stomach

Pancreas

Figure 9.14c Pancreatic tissue.

Cord of beta (𝛃) cells

secreting insulin into

capillaries

Capillaries

Exocrine

cells of

pancreas

Alpha (𝛂)

Pancreatic Islets

Insulin

Released when blood glucose levels are high

Increases the rate of glucose uptake and metabolism

by body cells

Glucagon

Released when blood glucose levels are low

Stimulates the liver to release glucose to blood, thus

increasing blood glucose levels

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BioFlix™: Homeostasis

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Figure 9.15 Regulation of blood glucose levels by a negative feedback mechanism involving pancreatic hormones.

Stimulus

Bloodglucose level(e.g., aftereating fourjelly doughnuts) Stimulus

Blood glucoselevel (e.g., afterskipping a meal)

Insulin

Pancreas

Tissue cells

Glucose Glycogen

Uptake of glucose fromblood is enhanced inmost body cells

Blood glucosefalls to homeostaticset point; stimulusfor insulin releasediminishes

Liver takes upglucose and storesas glycogen

Insulin-secreting cellsof the pancreas activated;release insulin into theblood

Elevated bloodsugar level

Blood glucose risesto homeostaticset point; stimulusfor glucagonrelease diminishes

Liver breaksdown glycogenstores andreleases glucoseto the blood

Glucose Glycogen

LiverGlucagon

Low blood sugar level

Glucagon-releasingcells of pancreasactivated; releaseglucagon into blood

Diabetes mellitus

Occurs in the absence of insulin

Blood sugar levels increase dramatically

Blood glucose is lost in the urine; water follows

Three cardinal signs:

1. Polyuria

production of abnormally large volumes of dilute urine.

2. Polydipsia

excessive thirst

3. Polyphagia

excessive hunger

Oral Glucose Tolerance Test

Pineal Gland (1 hormone)

Neural stimuli

Thymus (1 hormone)

Humoral stimuli

Gonads (endocrine function same as adrenal cortex)

Testes (1 group, 1 main hormone)

Ovaries (2 groups)

Placenta (3 hormones)

Study all glands and hormones. Complete WB 185-187, 189

Figure 9.3 Location of the major endocrine organs of the body.

Pineal gland

Hypothalamus

Pituitary gland

Thyroid gland

Parathyroid glands

Thymus

Adrenal glands

Pancreas

Ovary (female)

Testis (male)

Pineal GlandLocated in the middle of the brain

Stimulated by light

Secretes melatonin

Helps establish the body’s sleep/wake cycles

Establishes biological rhythms

Coordinates fertility hormones in humans

Circadian Rhythms

Thymus Gland

Located posterior to the sternum

Largest in infants and children

Produces thymosin

Matures some types of white blood cells

Important in developing the immune system

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Gonads

Ovaries

Produce eggs

Produce two groups of steroid hormones:

1. Estrogens

2. Progesterone

Testes

Produce sperm

Produce androgens

Ex. testosterone

Hormones of the Ovaries

Estrogens

Development of secondary female characteristics

Mature female reproductive organs

Progesterone

Helps in the implantation of an embryo in the uterus

Helps prepare breasts for lactation

In combination, progesterone and estrogens

Promote breast development

Regulate menstrual cycle

Hormones of the Testes

Produce several androgens

Testosterone is the most important androgen

Responsible for male secondary sex characteristics

Promotes growth

Promotes maturation of male reproductive system

Required for sperm cell production

Testosterone levels – Optimal vs. Low(exaggerated illustration)

Placenta

Hormones maintain pregnancy

Progesterone

hCG (human chorionic gonadotropin)

Estrogen

Some hormones help during childbirth

Endocrine System Videos as Review

Endocrine System Video Support

Hormone song https://www.youtube.com/watch?v=UqEgTUlG8FU

Watch the following videos to review the endocrine system, hormones and gland functions.

CC Endocrine system part 1 – A&P

https://www.youtube.com/watch?v=eWHH9je2zG4

CC Endocrine system part 2 – A&P

https://www.youtube.com/watch?v=SCV_m91mN-Q

CC Endocrine system – Biology

https://www.youtube.com/watch?v=WVrlHH14q3o

nerve activates contractionqrmhsalvarez.weebly.com/uploads/1/2/7/2/12724614/anatomy_endo… ·...

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