The Endocrine SytemSecond controlling system of the body

◦Nervous system is the fast-control systemUses chemical messengers

(hormones) that are released into the blood

Hormones control several major processes◦Reproduction◦Growth and development◦Mobilization of body defenses◦Maintenance of much of homeostasis◦Regulation of metabolism

Figure 9.3

Pineal gland

HypothalamusPituitary gland

Thyroid gland

Parathyroid glands

Thymus

Adrenal glands

Pancreas

Ovary (female)

Testis (male)

Chemical Make-upHormones are classified

chemically as◦Amino acid–based, which includes

Proteins Peptides Amines

◦Steroids—made from cholesterol◦Prostaglandins—made from highly

active lipids

Mechanisms of Hormone Action

Hormones affect only certain tissues or organs (target cells or target organs)

Target cells must have specific protein receptors

Hormone-binding alters cellular activity

Figure 9.1a

Steroidhormone

Cytoplasm Nucleus

Receptorprotein

Hormone-receptor complex

DNA

mRNA

Newprotein

Plasmamembraneof targetcell

(a) Steroid hormone action

1 2

3

4

5

6

Figure 9.1b

Nonsteroidhormone (first messenger)

Cytoplasm

Enzyme

Receptorprotein

Plasma membraneof target cell

Secondmessenger

Effect on cellular function, such as glycogenbreakdown

(b) Nonsteroid hormone action

ATP

cAMP

12

3

4

Control of Hormone Release

Hormone levels in the blood are mostly maintained by negative feedback

A stimulus or low hormone levels in the blood triggers the release of more hormone

Hormone release stops once an appropriate level in the blood is reached

Hormonal Stimuli of Endocrine Glands

Most common stimuliEndocrine glands are activated by

other hormones

© 2012 Pearson Education, Inc. Figure 9.4

Releasing hormonessecreted into portalcirculation

Anterior pituitary

Hypophysealportal system

Growth hormone (GH)

Bones and muscles Prolactin (PRL)

Mammaryglands

Follicle-stimulatinghormone (FSH)and luteinizinghormone (LH)

Posterior pituitary

Hypothalamus

Adrenocorticotropichormone (ACTH)

Adrenal cortexThyrotropichormone (TH)

Thyroid

Testes or ovaries

HypothalamusHypothalamus

© 2012 Pearson Education, Inc. Figure 9.6

Opticchiasma

Axon terminals

Anterior lobeof the pituitary

ADH

Kidney tubules

Hypothalamicneurosecretorycells

Hypothalamus

Arterial blood supply

Posterior lobe

Capillary bed

Venous drainage

Oxytocin

Mammary glandsUterine muscles

HypothalamusPart of the brain that sits above the pituitaryThey work togetherAnterior Pituitary1. Growth hormone2. Adrenocorticotropic hormone - ACTH3. Thyroid stimulating hormone - TSHPosterior Pituitary4. Antidiruetic hormone (ADH) – promotes re-

absorption of water in kidney – increases BP

5. Oxytocin – uterine contractions

Adrenal GlandsRespond to ACTH by producing:1. Glucocorticoids (cortisone) –

produce glucose in blood through fatty acid breakdown, inhibit inflammation.

2. Mineralocorticoids (aldosterone) – promote uptake of sodium and chloride in kidneys, water follows, increase BP

3. Epinephrine - emergency hormone

© 2012 Pearson Education, Inc. Figure 9.12

Decreased Na+ or

increased K+ in blood

Decreasedblood volumeand/or bloodpressure

Kidney

ReninIndirectstimulatingeffect viaangiotensin

Angiotensin II

Directstimulatingeffect

Increased absorptionof Na+ and water;

increased K+ excretion

Increased bloodvolume andblood pressure

Enhanced secretion of aldosterone targets kidney tubules

Mineralocorticoid-producing part of adrenal cortex

Inhibitoryeffect

Atrial natriureticpeptide (ANP)

ACTH

Heart

Increasedblood pressureor blood volume

Anterior pituitary

Corticotropin-releasing hormone

Hypothalamus

Stress

© 2012 Pearson Education, Inc. Figure 9.13

Short term

Spinal cord

Catecholamines(epinephrine and norepinephrine)

Adrenalmedulla

1. Increased heart rate2. Increased blood pressure3. Liver converts glycogen to glucose and releases glucose to blood4. Dilation of bronchioles5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity6. Increased metabolic rate

1. Retention of sodium and water by kidneys2. Increased blood volume and blood pressure

1. Proteins and fats converted to glucose or broken down for energy2. Increased blood sugar3. Suppression of immune system

Short-term stress response Long-term stress response

Preganglionicsympatheticfibers

Nerve impulses

Hypothalamus

More prolongedStress

Releasing hormones

Corticotropic cells ofanterior pituitary

ACTH Adrenalcortex

Mineralocorticoids Glucocorticoids

ThyroidStimulated by Thyrotropin releasing

hormone (TRH) from the hypothalamus which stimulates TSH from anterior pituitary.

1. Thyroxine (iodine)Maintains metabolism Hyperthyroidism – high metabolic rate,

nervous, irritableHypothyroidism – low met. Rate, slow,

sluggish, overweight2. Calcitonin – takes up calcium from blood

to bones

Disorders of the endocrine systemGoiter – iodine deficiency, thyroxin

production declinesThe hypothalamus secretes TRH, but

has no effectResults in enlargement of the thyroid Grave’s disease – antibodies in the

immune system mistakenly bind to TSH receptors on the thyroid gland stimulating more thyroxin production - hyperthyroidism

ParathyroidsRest on the thyroid1. Parathyroid hormone – releases

calcium from bone to blood Opposite of calcitonin Bone remodeling

Figure 9.10

Calcitonin

Thyroid glandreleases calcitonin.

StimulusRising bloodCa2+ levels

Calcium homeostasis of blood: 9–11 mg/100 ml

Osteoclastsdegrade bonematrix andrelease Ca2+ into blood.

BALANCE

IMBALANCE

IMBALANCE

Calcitoninstimulatescalcium saltdeposit in bone.

StimulusFalling bloodCa2+ levels

BALANCE

Parathyroidglands releaseparathyroidhormone (PTH).

Thyroidgland

Parathyroidglands

PTH

© 2012 Pearson Education, Inc. Figure 5.6

Bone growth

Bone grows inlength because:

Bone remodeling

Growing shaft isremodeled as:

Cartilagegrows here.

Cartilageis replacedby bone here.

Cartilagegrows here.

Cartilageis replaced by bone here.

1

2

3

4

1

2

3 Bone isresorbed here.

Epiphyseal plate

Articular cartilage

Bone isresorbed here.

Bone is addedby appositionalgrowth here.

PancreasIslets of Langerhans – produce

insulin and glucagon1. Glucagon stimulates glycogen to

break into glucose molecules and be released into the blood

2. Insulin decreases the glucose in the blood

Figure 9.15

Uptake of glucosefrom blood isenhanced in mostbody cells

Tissue cells

Glucose GlycogenPancreas

InsulinInsulin-secreting cellsof the pancreasactivated; releaseinsulin into the blood

Elevated bloodsugar level

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

Blood glucose risesto homeostaticset point; stimulusfor glucagonrelease diminishes

Liver breaksdown glycogenstores andreleasesglucose to theblood

Glucose Glycogen

LiverGlucagon

Glucagon-releasingcells of pancreasactivated; releaseglucagon into blood

Low blood sugar level

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

BALANCE: Normal blood glucose level (about 90 mg/100 ml)

IMBALANCE

Liver takes upglucose and storesas glycogen

Blood glucosefalls to homeostaticset point; stimulusfor insulin releasediminishes

IMBALANCE

thermoregulationEctotherm vs. endothermCooling by evaporationWarming by metabolism – shivering and

metabolizing fatVasodilation and vasoconstriction of blood

vesselsEx. In hot environments, animals increase

blood flow to their ears to release heat and in cold do the opposite.

Countercurrent exchange – warm blood is traveling to extremities.

Hibernation, blubber, hair, basking,…

Reproductive SystemsFemaleOvaries – produce eggs (ova) and

secrete estrogen and progesterone

Stimulated by FSH and LHMaleFSH – stimulates sperm

productionLH – stimulates interstitial cells to

produce testosterone

Figure 16.8b

(b)

Vagina

Cervical canal

Wall ofuterus

EndometriumMyometriumPerimetrium

Round ligament of uterus

FimbriaeInfundibulumUterine

tube

Lumen (cavity)of uterus

Fundusof uterus

Ovary

Uterine (fallopian) tube

Suspensoryligament of ovary

Ovarianbloodvessels

Broadligament

Ovarian ligament

Body ofuterus

Ureter

UterosacralligamentCervix

Uterine bloodvessels

Menstrual CyclePhase 1Follicular phase (10 days)Anterior pituitary secretes FSH and LHFSH – follicle stimulating hormoneLH – luteinizing hormone Follicle grows – releases estrogen

which causes uterine lining to thicken-endometrium

Estrogen also causes ant. Pit. To release LH

The luteal surge causes ovulation

Figure 16.7

Growing follicles

Primary follicle

Degeneratingcorpus luteum

Corpus luteum

Developingcorpus luteum

Rupturedfollicle

OvulationSecondary oocyte

Germinalepithelium

Bloodvessels

Antrum

Coronaradiata

Mature vesicular(Graafian) follicle

Ovulation – release of the egg from the ovary ends the follicular phase.

Ova floats into fallopian tube (oviduct)

Phase 2Luteal phaseFollicle has released the egg and

changes into the corpus luteumCorpus luteum continues to secrete

estrogen and now begins to produce progesterone

Progesterone increases vessels and glands in uterus

After about 13-15 days, if fertilization and implantation have NOT occurred the corpus luteum shuts down

Phase 3

MenstruationUterus reabsorbs some of the

tissue created in the endometrium

The rest sheds off and is passed out of the body

Figure 16.2a

Ampulla ofductus deferens

Ductus (vas) deferens

(a)

Bulbourethral glandProstate

RectumEjaculatory duct

Seminal vesicle

Epididymis

ScrotumTestis

Shaft of the penis

Spongy urethra

External urethral orifice

Prepuce

Glans penis

Urogenital diaphragm

Membranous urethra

UreterUrinary bladderProstatic urethraPubis

Erectile tissue of the penis

Male Reproductive system