chapter 45 ppt

Chapter 45 Chapter 45 Hormones & the Endocrine SystemHormones & the Endocrine System

Roohi RamachandranRoohi Ramachandran

Vocab.• Endocrine glands: ductless gland that secretes hormones directly

into interstitial fluid, from which they diffuse into the bloodstream

• Exocrine glands: have ducts that carry secreted substances onto body surfaces or into body cavities, e.g. salivary glands

• Hormones: one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids and act on specific target cells in other parts of the body to change their functioning

• Target cells: cells that have receptors for a particular hormone

• Neurosecretory cells: specialized neurons found in the brain that secrete molecules that diffuse from nerve cell endings into the bloodstream

• Neurotransmitters: molecules released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft and binds to the postsynaptic cell, triggering a response

Nervous & Endocrine Systems

• Work together to maintain homeostasis, development and reproduction

• Hypothalamus: receives information from nerves throughout body and brain and initiates endocrine signalling according to environmental conditions

Insect Development

Brain

Neurosecretory cells

Corpus cardiacum

Corpus allatum

EARLYLARVA

LATERLARVA PUPA ADULT

Prothoracicgland

Ecdysone

Brainhormone (BH)

Juvenilehormone(JH)

LowJH

Brain

Neurosecretory cells

Corpus cardiacum

Corpus allatum

EARLYLARVA


EARLYLARVA


Prothoracicgland

Ecdysone

Brainhormone (BH)

Juvenilehormone(JH)

LowJH

• Neurosecretory cells produce PTTH

• PTTH signals ecdysone release

• Each ecdysone release stimulates molting

• Juveline hormone determines effect of ecdysone; high concentration suppresses metamorphosis

Types of Signalling Molecules• Local regulators: secreted

molecules that act over short distances and reach their target cells solely by diffusion

• Hormones: molecule secreted into extracellular fluid, circulates in blood/hemolymph and communicates regulatory messages throughout body

• Pheromones: small molecule released into environment that functions in communication between same species; acts like hormone in animals

Inflammation

• Interleukins: regulate lymphocytes, other immune cells

• Prostaglandins: promote inflammation & fever, intensify pain, regulate platelet aggregation (blood clotting)

• Histamines: blood vessel dilation – more permeable to inflammatory response

Local Regulators• Have varied effects because of

differences in target cells’ reception, transduction and/or response

• Prostaglandins:– Childbirth: excite muscles,

induce labor– Immune: fever, inflammation,

intensify pain• Nitric Oxide (NO)

– Neurons: neurotransmitter– White blood cells: kills bacteria

and cancer cells– Endothelial cells: dilates the

walls of blood vessels

Regulation & Communication

Figure 8.19 (b) Competitive inhibition

A competitiveinhibitor mimics the

substrate, competingfor the active site.

Competitiveinhibitor

A substrate canbind normally to the

active site of anenzyme.

Substrate

Active site

Enzyme

(a) Normal binding

Figure 8.19 (b) Competitive inhibition






Substrate

Active site

Enzyme

(a) Normal binding

(b) Competitive inhibition




(b) Competitive inhibition









Substrate

Active site

Enzyme

(a) Normal binding

Figure 8.19

A noncompetitiveinhibitor binds to theenzyme away from

the active site, alteringthe conformation of

the enzyme so that itsactive site no longer

functions.

Noncompetitive inhibitor

(c) Noncompetitive inhibitionFigure 8.19




functions.


(c) Noncompetitive inhibition




functions.


(c) Noncompetitive inhibition

Active siteavailable

Isoleucineused up bycell

Feedbackinhibition

Isoleucinebinds to allostericsite

Active site of enzyme 1 no longer binds threonine;pathway is switched off

Initial substrate(threonine)

Threoninein active site

Enzyme 1(threoninedeaminase)

Intermediate A

Intermediate B

Intermediate C

Intermediate D

Enzyme 2

Enzyme 3

Enzyme 4

Enzyme 5

End product(isoleucine)

Figure 8.21



Feedbackinhibition






Intermediate A

Intermediate B

Intermediate C

Intermediate D

Enzyme 2

Enzyme 3

Enzyme 4

Enzyme 5




Feedbackinhibition






Intermediate A

Intermediate B

Intermediate C

Intermediate D

Enzyme 2

Enzyme 3

Enzyme 4

Enzyme 5


Figure 8.21

EXTRACELLULARFLUID

Receptor

Signal molecule

Relay molecules in a signal transduction pathway

Plasma membraneCYTOPLASM

Activationof cellularresponse

Figure 11.5

EXTRACELLULARFLUID

Receptor

Signal molecule




EXTRACELLULARFLUID

Receptor

Signal molecule




Figure 11.5

Hormones are signalling molecules. Their receptors can be affected by (non)competitive inhibitors. Negative feedback loops (feedback inhibition) regulate them.

Hypothalamus & PituitaryTropic Effects OnlyFSH, follicle-stimulating hormoneLH, luteinizing hormoneTSH, thyroid-stimulating hormoneACTH, adrenocorticotropic hormone

Nontropic Effects OnlyProlactinMSH, melanocyte-stimulating hormoneEndorphin

Nontropic and Tropic EffectsGrowth hormone

Neurosecretory cellsof the hypothalamus

Portal vessels

Endocrine cells of theanterior pituitary

Hypothalamicreleasinghormones(red dots)

HORMONE FSH and LH TSH ACTH Prolactin MSH Endorphin Growth hormone

TARGET Testes orovaries

Thyroid Adrenalcortex

Mammaryglands

Melanocytes Pain receptorsin the brain

Liver Bones

Pituitary hormones(blue dots)

Figure 45.8

Tropic Effects OnlyFSH, follicle-stimulating hormoneLH, luteinizing hormoneTSH, thyroid-stimulating hormoneACTH, adrenocorticotropic hormone




Portal vessels






Mammaryglands


Liver Bones






Portal vessels






Mammaryglands


Liver Bones





Portal vessels






Mammaryglands


Liver Bones


Figure 45.8

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Anteriorpituitary

Posteriorpituitary

HORMONE ADH Oxytocin

TARGET Kidney tubules Mammary glands,uterine muscles

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Anteriorpituitary

Posteriorpituitary

HORMONE ADH Oxytocin

TARGET Kidney tubules Mammary glands,uterine muscles

• Hypothalamus: maintains homeostasis, coordinates endocrine & nervous systems

• Anterior pituitary: synthesize/secrete several tropic/nontropic hormones; regulated by hypothalamus

• Posterior pituitary: extension of hypothalamus; stores/secretes oxytocin & ADH

Pineal, Thyroid, Parathyroid• Pineal gland: in center of brain;

synthesizes/secretes melatonin• Thyroid gland: two lobes on ventral

side of trachea; secretes iodine-containing T3 and T4, which control

metabolism & development; regulated by TSH (thyroid stimulating hormone)

• Parathyroid gland: four small structures embedded in back of thyroid; regulate Ca2+ levels (PTH decomposes bone, stimulates reabsorption in kidneys, activates Vitamin D to stimulate intestines to absorb)

CalcitoninThyroid glandreleasescalcitonin.

StimulatesCa2+ depositionin bones

ReducesCa2+ uptakein kidneys

STIMULUS:Rising bloodCa2+ level

Blood Ca2+

level declinesto set point

Homeostasis:Blood Ca2+ level

(about 10 mg/100 mL)

Blood Ca2+

level risesto set point

STIMULUS:Falling bloodCa2+ level

StimulatesCa2+ releasefrom bones

Parathyroidgland

IncreasesCa2+ uptakein intestines

Activevitamin D

Stimulates Ca2+

uptake in kidneys

PTH

Figure 45.11





Blood Ca2+




Blood Ca2+




Parathyroidgland


Activevitamin D

Stimulates Ca2+

uptake in kidneys

PTH





Blood Ca2+




Blood Ca2+




Parathyroidgland


Activevitamin D

Stimulates Ca2+

uptake in kidneys

PTH

Figure 45.11

PancreasBeta cells ofpancreas are stimulatedto release insulininto the blood.

Insulin

Liver takesup glucoseand stores itas glycogen.

Body cellstake up moreglucose.

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

STIMULUS:Rising blood glucose

level (for instance, aftereating a carbohydrate-

rich meal)

Homeostasis:Blood glucose level


Blood glucose levelrises to set point;

stimulus for glucagonrelease diminishes.

STIMULUS:Dropping blood glucoselevel (for instance, after

skipping a meal)

Alpha cells of pancreasare stimulated to releaseglucagon into the blood.

Liver breaksdown glycogenand releasesglucose intoblood.

GlucagonFigure 45.12

Beta cells ofpancreas are stimulatedto release insulininto the blood.

Insulin






rich meal)






skipping a meal)



Glucagon

Beta cells ofpancreas are stimulatedto release insulininto the blood.

Insulin






rich meal)






skipping a meal)



GlucagonFigure 45.12

• Islets of Langerhans: endocrine cells w/i pancreas; secrete into interstitial fluid & circulate– Alpha cells: glucagon– Beta cells: insulin

• Insulin lowers blood glucose by stimulating glucose uptake in body cells

• Glucagon signals liver to increase glycogen hydrolysis, convert aminos & glycerol to glucose & release glucose into bloodstream

Spinal cord(cross section)

Nervesignals

Nervecell

Releasinghormone

Hypothalamus

Anterior pituitary

Blood vessel

ACTH

Adrenalgland

Kidney

Adrenal medullasecretes epinephrineand norepinephrine.

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increasedblood glucose

2. Increased blood pressure

3. Increased breathing rate

4. Increased metabolic rate

Effects ofmineralocorticoids:

1. Retention of sodiumions and water bykidneys

2. Increased bloodvolume and bloodpressure

Effects ofglucocorticoids:

1. Proteins and fatsbroken down andconverted to glucose,leading to increasedblood glucose

(b) Long-term stress response(a) Short-term stress response

Nerve cell

Spinal cord(cross section)

Nervesignals

Nervecell

Releasinghormone

Hypothalamus

Anterior pituitary

Blood vessel

ACTH

Adrenalgland

Kidney

Adrenal medullasecretes epinephrineand norepinephrine.

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increasedblood glucose

2. Increased blood pressure

3. Increased breathing rate

4. Increased metabolic rate

Effects ofmineralocorticoids:

1. Retention of sodiumions and water bykidneys

2. Increased bloodvolume and bloodpressure

Effects ofglucocorticoids:

1. Proteins and fatsbroken down andconverted to glucose,leading to increasedblood glucose

(b) Long-term stress response(a) Short-term stress response

Nerve cell

Adrenal Glands• Adrenal glands: near kidneys

• Adrenal medulla: secretes epinephrine/norepinephrin in response to stress; regulates metabolism, blood pressure, etc.

• Adrenal cortex: secrete glucocorticoids (promote glucose synthesis) and mineralocorticoids (maintain salt/water balance)

Gonads• Gonads produce following hormones:

• Androgen: any steroid that stimulates development of male reproductive system

• Testosterone: major mammalian androgen

• Estrogen: any steroid that stimulates development of female reproductive system

• Estradiol: major mammalian estrogen

• Progestin: any steroid w/ progesterone-like activity

• Progesterone: steroid that prepares uterus for pregnancy; major mammalian progestin

• All are produced in both genders – proportions differ

chapter 45 ppt

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