the endocrine system ap chapter 45. you do not need to memorize all of the specific hormones!...

The Endocrine System

• AP Chapter 45

• You do not need to memorize all of the specific hormones!

• Concentrate on the thyroid, adrenal glands, pancreas, and sex hormones

• Emphasis will be on FEEDBACKS!

• The endocrine system, along with the nervous system, is responsible for coordinating our responses.

• The endocrine system is a slower system and the nervous system is a faster response.

Chemical signals

• Chemicals found in both systems and also as part of other signaling mechanisms bind to specific receptor proteins on or in target cells.

Secreted chemical signals include

– Hormones – produced by endocrine glands,

travel through the blood stream to target organs

ex – insulin, estrogen– Local regulators

(a) paracrine signals – act on neighboring cells, ex. – cytokines, interferon, prostaglandins

(b) autocrine signals – act on secreting cells itself, ex – cytokines

– Neurotransmitters - secreted by neurons at synapses

ex- serotonin, nitric oxide (NO)– Neurohormones – secreted by neurosecretory

cells, travel through the blood stream to target organs or synapses

ex- epinephrine– Pheromones – released into the environment;

between individuals

ex – insects marking trails,

mating, etc.

Fig. 45-2

Bloodvessel Response

Response

Response

Response

(a) Endocrine signaling

(b) Paracrine signaling

(c) Autocrine signaling

(d) Synaptic signaling

Neuron

Neurosecretorycell

(e) Neuroendocrine signaling

Bloodvessel

Synapse

Response

Chemical Classes of Hormones

• Three major classes of molecules function as hormones in vertebrates:

– Polypeptides (proteins and peptides)

water soluble– Amines derived from amino acids

some are water soluble, some are lipid soluble

– Steroid hormones

lipid soluble

Fig. 45-3

Water-soluble Lipid-soluble

Steroid:Cortisol

Polypeptide:Insulin

Amine:Epinephrine

Amine:Thyroxine

0.8 nm

• Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not

• The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells

• Water-soluble hormones (hydrophilic) are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors

• Lipid-soluble hormones (hydrophobic) diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells

Fig. 45-5-1

NUCLEUS

Signalreceptor

(a) (b)

TARGETCELL

Signal receptor

Transportprotein

Water-solublehormone

Fat-solublehormone

Fig. 45-5-2

Signalreceptor

TARGETCELL

Signal receptor

Transportprotein

Water-solublehormone

Fat-solublehormone

Generegulation

Cytoplasmicresponse

Generegulation

Cytoplasmicresponse

OR

(a) NUCLEUS (b)

Multiple Effects of Hormones

• Hormones can have multiple effects which depends on:

- the type of receptor they bind to - the specific signal transduction pathway - the specific transcription factor they activate.

• A hormone can also have different effects in different species

Fig. 45-8-1

Glycogendeposits

receptor

Vesseldilates.

Epinephrine

(a) Liver cell

Epinephrine

receptor

Glycogenbreaks downand glucoseis released.

(b) Skeletal muscle blood vessel

Same receptors but differentintracellular proteins (not shown)

Fig. 45-8-2

Glycogendeposits

receptor

Vesseldilates.

Epinephrine

(a) Liver cell

Epinephrine

receptor

Glycogenbreaks downand glucoseis released.

(b) Skeletal muscle blood vessel

Same receptors but differentintracellular proteins (not shown)

Epinephrine

receptor

Different receptors

Epinephrine

receptor

Vesselconstricts.

(c) Intestinal blood vessel

Negative feedback and antagonistic hormone pairs are common features of the

endocrine system

• Hormones are assembled into regulatory pathways

• A negative feedback loop inhibits a response by reducing the initial stimulus

• Negative feedback regulates many hormonal pathways involved in homeostasis

Fig. 45-11Pathway Example

Stimulus Low pH induodenum

S cells of duodenumsecrete secretin ( )

Endocrinecell

Bloodvessel

PancreasTargetcells

Response Bicarbonate release

Neg

ativ

e fe

edb

ack

–

Insulin and Glucagon: Control of Blood Glucose – an example of antagonistic

hormone pairs

• The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin

• Insulin reduces blood glucose levels by– Promoting the cellular uptake of glucose– Slowing glycogen breakdown in the liver– Promoting fat storage

• Glucagon increases blood glucose levels by– Stimulating conversion of glycogen to

glucose in the liver– Stimulating breakdown of fat and protein

into glucose

– Remember: Glucagon – “Glucose ON!”

Fig. 45-12-2

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Insulin

Beta cells ofpancreasrelease insulininto the blood.

STIMULUS:Blood glucose level

rises.

Liver takesup glucoseand stores itas glycogen.

Blood glucoselevel declines.

Body cellstake up moreglucose.

Fig. 45-12-4

Homeostasis:Blood glucose level

(about 90 mg/100 mL)

Glucagon

STIMULUS:Blood glucose level

falls.

Alpha cells of pancreasrelease glucagon.

Liver breaksdown glycogenand releasesglucose.

Blood glucoselevel rises.

Remember!

GLUCOSE in the BLOOD

INSULIN GLUCAGON

Diabetes Mellitus

• Diabetes mellitus is perhaps the best-known endocrine disorder

• It is caused by a deficiency of insulin or a decreased response to insulin in target tissues

• It is marked by elevated blood glucose levels

• Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells

• Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors

Fig. 45-10Major endocrine glands:

Adrenalglands

Hypothalamus

Pineal gland

Pituitary gland

Thyroid gland

Parathyroid glands

Pancreas

Kidney

Ovaries

Testes

Organs containingendocrine cells:

Thymus

Heart

Liver

Stomach

Kidney

Smallintestine

Coordination of Endocrine and Nervous Systems in Vertebrates

• The hypothalamus receives information from the nervous system and initiates responses through the endocrine system

• Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary which can control other glands

Who is the boss?

The hypothalamus has neurosecretory cells which secrete releasing and inhibiting hormones which control the pituitary gland which in turn controls other glands.

* RH, such TRH, indicates a releasing hormone

Fig. 45-14

Spinal cord

Posteriorpituitary

Cerebellum

Pinealgland

Anteriorpituitary

Hypothalamus

Pituitarygland

Hypothalamus

Thalamus

Cerebrum

The hypothalamic – pituitary axis

Hypothalamus

• The hypothalamus secretes two hormones which are stored in the posterior pituitary.

1) oxytocin – induces uterine contractions during birth and milk production

2) ADH – which decreases urine volume

Fig. 45-15

Posteriorpituitary

Anteriorpituitary

Neurosecretorycells of thehypothalamus

Hypothalamus

Axon

HORMONE OxytocinADH

Kidney tubulesTARGET Mammary glands,uterine muscles

Pituitary Gland

• The posterior pituitary stores and secretes hormones that are made in the hypothalamus

• The anterior pituitary makes and releases hormones under regulation of the hypothalamus

Fig. 45-17

Hypothalamicreleasing andinhibitinghormones

Neurosecretory cellsof the hypothalamus

HORMONE

TARGET

Posterior pituitary

Portal vessels

Endocrine cells ofthe anterior pituitary

Pituitary hormones

Tropic effects only:FSHLHTSHACTH

Nontropic effects only:ProlactinMSH

Nontropic and tropic effects:GH

Testes orovaries

Thyroid

FSH and LH TSH

Adrenalcortex

Mammaryglands

ACTH Prolactin MSH GH

Melanocytes Liver, bones,other tissues

The anterior pituitary secretes tropic hormones

• A tropic hormone regulates the function of endocrine cells or glands

• You do not need to memorize these….just realize they are TROPIC hormones and regulate other endocrine glands. You may see them in diagrams.

• The four strictly tropic hormones are– Thyroid-stimulating hormone (TSH) – Follicle-stimulating hormone (FSH)– Luteinizing hormone (LH)– Adrenocorticotropic hormone (ACTH)

(FSH and LH are reproductive hormones.)

Thyroid Gland

• T3 and T4 thyroxin, regulates metabolism

(needs dietary iodine to function properly – goiter if not enough iodine)

• Calcitonin – lowers calcium in blood – deposition in bones and secretion into kidney filtrate

“tone down the calcium”

T3 and T4

• act by binding to thyroid receptors that are distributed in almost every organ.

• Typically, this process regulates gene transcription and the subsequent production of various proteins that are involved in development, growth, and cellular metabolism

Graves Disease• an autoimmune

disorder that leads to overactivity of the thyroid gland (hyperthyroidism) and causes the thyroid to increase in size. Other symptoms are anxiety, tiredness, insomnia, irregular heart rhythms, bulging eyes.

Parathyroid Gland

• PTH parathormone – raises calcium levels in blood – from bones and reuptake in kidneys

Fig. 45-20-2

PTH

Parathyroid gland(behind thyroid)

STIMULUS:Falling blood

Ca2+ level

Homeostasis:Blood Ca2+ level

(about 10 mg/100 mL)

Blood Ca2+ level rises.

Stimulates Ca2+

uptake in kidneys

Stimulates Ca2+ release from bones

Increases Ca2+ uptake in intestines

Activevitamin D

Adrenal medulla

• Epinephrine (adrenaline) – raises metabolic rate, “fight or flight”

• Norepinephrine (noradrenaline) controls blood pressure

medulla

cortex

Adrenal cortex

• Glucocorticoids (cortisol) – glucose from noncarb sources, such as muscles

• Mineralocorticoids (aldosterone) – induces kidneys to reabsorb water and salts

• Both of these deal with long-term stress

Cushing’s Disease

Cushing's syndrome is a hormonal disorder caused by prolonged exposure of the body's tissues to high levels

of the hormone cortisol.

•severe fatigue•weak muscles•high blood pressure•high blood glucose•increased thirst and urination•irritability, anxiety, depression•a fatty hump between the shoulders•moon face

Fig. 45-21c

(b) Long-term stress response

Effects ofmineralocorticoids:

Effects ofglucocorticoids (cortisol):

1. Retention of sodium ions and water by kidneys

2. Increased blood volume and blood pressure

2. Possible suppression of immune system

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

Adrenalgland

Kidney

Adrenal cortex

STRESS!

The production of these hormonesis controlled by thehypothalamus andanterior pituitary

Testes

• Androgens (testosterone) – gender, male secondary sex characteristics

Ovaries

• Estrogen – maintenance of female reproductive system and development of secondary female characteristics

• Progesterone – prepares uterus for child

Pineal Gland

• Melatonin – biological clock

Hormonal pathways work with the hypothalamus and anterior pituitary to coordinate responses

• In regulating metabolism by the thyroid:

Also, notice the positiveAND negative feedbackshere.

Hormonal pathways work with the hypothalamus and anterior pituitary to

coordinate responses

• Ex – in the gonads

• GnRH (hypothalamus) affects FSH and LH (anterior pituitary) which affects estrogens and androgens (ovaries/testes)

Testosterone Synthesis

Estrogen and progesterone

synthesis

Which endocrine gland?

• Too little of my hormone and you will feel tired and sluggish and probably gain weight.

THYROID

A malfunction in this gland can result in a giant.

Anterior Pituitary

This gland prepares me for an emergency situation by increasing my heartrate.

AdrenalGlands

This gland is also used in the digestive system. It also comes into play when I eat lots of M and M’s!

PANCREAS

This gland is called the “master gland” because it secretes nine hormones many of which control other endocrine glands by feedback control.

PituitaryGland

If this gland is not working properly, diabetes can result.

Pancreas

• If this gland is not working properly, your nerves and muscles will not function properly either due to calcium deficiency.

ParathyroidGland

• These glands do not function properly in chromosomal mutations such as in Turner’s and Klinefelter’s syndrome.

Gonads

This gland makes me wake up in the morning and ready to go!

Pineal Gland

Fig. 45-10Major endocrine glands:

Adrenalglands

Hypothalamus

Pineal gland

Pituitary gland

Thyroid gland

Parathyroid glands

Pancreas

Kidney

Ovaries

Testes

Organs containingendocrine cells:

Thymus

Heart

Liver

Stomach

Kidney

Smallintestine

Name of

Gland

Hormone Function

A pineal Daily rhythms

B

hypothalamus

Regulates blood volume and

pressure by affecting kidneys

C Growth hormone growth

D thyroid calcitonin

E parathyroid Raises calcium levels

F Hormones for immune

system

immune

G adrenal adrenaline

H insulin Lowers blood glucose levels

I ovaries Testosterone/

J testes Testosterne/androgens Secondary female sexual

characteristics

Hormones in the reproductive system

• GnRH from the hypothalamus directs the anterior pituitary to produce FSH and LH that regulate gametogenesis and sex hormone production in males and females

• Sex hormones:

- androgens – male in the testes

- estrogens – female in the ovaries

• So in males, FSH and LH (pituitary hormones) stimulate the production of sperm and secretion of testosterone

Fig. 46-13

Hypothalamus

GnRH

FSH

Anterior pituitary

Sertoli cells Leydig cells

Inhibin Spermatogenesis Testosterone

Testis

LH

Neg

ativ

e fe

edb

ack

Neg

ativ

e fe

edb

ack

– –

–

Nourish developing sperm Secrete testosterone

Fig. 46-11

Seminalvesicle(behind bladder)

(Urinarybladder)

Prostate gland

Bulbourethralgland

Erectile tissueof penis

Urethra

ScrotumVas deferens

Epididymis

Testis

Seminal vesicle

(Urinarybladder)

(Urinaryduct)

(Rectum)

Vas deferens

Ejaculatory duct

Prostate gland

Bulbourethral gland

Vas deferens EpididymisTestisScrotum

(Pubic bone)

Erectiletissue

Urethra

Glans

Prepuce

Penis

• In females, these control the reproductive cycle – the uterine cycle (menstrual cycle) and the ovarian cycle

• In the uterus, this results in the build-up of the inner layer of the uterus called the endometrium which will be shed (menstruation) if fertilization does not occur

Fig. 46-10b

OvariesOviduct

FolliclesCorpus luteum

Uterine wallUterus

Cervix

Endometrium

Vagina

• In the ovary, these control the development of the egg in the follicle, the release of the egg (ovulation), and the disintegration of the egg follicle (corpus luteum)

Fig. 46-14(a) Control by hypothalamus

Hypothalamus

GnRH

Anterior pituitary

1

Inhibited by combination ofestradiol and progesteroneStimulated by high levelsof estradiol

Inhibited by low levels of estradiol

2 FSH LH

Pituitary gonadotropinsin blood

(b)6

FSH

LH

FSH and LH stimulatefollicle to grow

LH surge triggersovulation

3

Ovarian cycle 8(c) 7

Growing follicle Maturingfollicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

Estradiol secretedby growing follicle inincreasing amounts

Progesterone andestradiol secretedby corpus luteum

4

Ovarian hormones in blood

Peak causesLH surge

(d)5

Estradiol Progesterone 910

Estradiol levelvery low

Progesterone and estra-diol promote thickeningof endometrium

Uterine (menstrual) cycle

Endometrium

(e)

Menstrual flow phase Proliferative phase Secretory phase

Day

s

0 5 10 14 20 25 28| | |

15| | | | |

–

–

+

Ovarian cycle

• Follicular phase: FSH stimulates follicle growth

• After LH surge, ovulation occurs

• Luteal Phase: ruptured follicle becomes a corpus luteum which secretes progesterone

LHFSH

Hypothalamus

Ant Pituitary

GnRH

Follicular phase Ovulation Luteal Phase

OvarianCycle

after LH surge

Uterine cycle

• Proliferative Phase: Estrogens from growing follicle stimulate the growth of the endometrium

• Secretory Phase - After ovulation, progesterone causes the increased vascularization and development of secretory glands

• Menstrual flow phase – rapid drop of hormones cause endometrium to disintegrate

Uterine Cycle

estradiol

progesterone

MenstrualCycle

ProliferativePhase

Secretory Phase

Promote thickeningof endometrium

When levels fall, menstrualCycle begins

endometrium

Fig. 46-14b

Ovarian hormones in blood

Peak causesLH surge

Estradiol level very low

Estradiol Progesterone

Ovulation Progesterone and estra-diol promote thickeningof endometrium

Uterine (menstrual) cycle

Endometrium

0 5 10 14 20 25 28| | | | | | | |

Da

ys

15

Menstrual flow phase Proliferative phase Secretory phase

(d)

(e)

Follicle producesestrogen

Corpus Luteummaintains production of est/progesterone

What happens if female becomes pregnant?

• Implantation takes place around 7 days after conception

• Embryo secretes hCG human chorionic gonadotropin maintains est/prog by corpus luteum

• In 2nd trimester of pregnancy, placenta takes over that job

How do birth control pills work?

• Synthetic est/prog combination that works by neg feedback to inhibit GnRN production and thus FSH and LH and no ovulation