Lecture 11, 26 Sept 2006 Vertebrate Physiology ECOL 437...

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Lecture 11, 26 Sept 2006

Vertebrate PhysiologyECOL 437 (MCB/VetSci 437)

Univ. of Arizona, Fall 2006

Kevin Bonine & Kevin Oh

1. Endocrine Physiology(Chap 14)

http://eebweb.arizona.edu/eeb_course_websites.htm

9-10 Randall et al. 2002

2. Reproductive Physiology(Chap 15)

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Housekeeping, 26 September 2006

Upcoming Readings

today: Text, chapter 14&15

Wed 27 Sept: endocrine discussion, see website for papersThurs 28 Sept: Text, chapter 15 and 16

-Term Paper Topic and Annotated Reference ListTues 03 Oct: Text, chapter 16

Lab oral presentations 27 Sept9am – Karina Flores2pm – Holly McCready

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Hill et al. 2004, Fig 10.2

How do the endocrine and nervous systems differ?

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Martin Wikelski, Princeton

-Hindgut microorganism symbionts-Oil Spill-Corticosterone

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Chap 14. Endocrine System – Glands and Hormones

Secretions with consequences

All cells secrete, butSpecialized secretory cells grouped into glands

Secrete same specialized substance (e.g., hormone)

Nervous System neurotransmitter acts near and fast

Other secretions, such as hormones, may act more distantly and over a longer time period

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Categories of cellular secretions:

Autocrine – affect the secreting cell directlyParacrine – affect neighboring cells

e.g., histamine and inflammation

Endocrine – release into bloodstreamExocrine – release onto epithelial surface

e.g., sweat onto skin, bile into digestive system

Pheromone – exocrine secretion to signal other individuals

Neuroendocrine – secretion from axon terminal into blood stream

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Neuroendocrine Systems

Neurosecretory cells secrete neurohormones

Axon terminates intoneurohemal organ

Neurohormones often [effect]other glands/hormones



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Hormone Types

Amines – small(e.g., epi, norepi, thyroid)

Eicosenoids from arachodonic acid(prostaglandins etc.)

Steroid Hormones from cholesterol(e.g., testosterone, estrogen)

Peptide Hormones – common, large, complex (e.g., insulin, ADH, GH)

(autocoids = others like histamine and serotonin) 9-11 Randall et al. 2002

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9Hill et al. 2004

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Amines – small(e.g., epi, norepi, thyroid)

Modified Amino Acids1. catecholamines (epi, norepi, dopamine; tyrosine)2. thyroid (lipid soluble; tyrosine)3. melatonin (tryptophan)

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Melatonin

Pineal GlandRetinaGI Tract

Produced at NightCircadian Rhythms Suprachiasmatic Nucleus (SCN) in Hypothalamus

AntioxidantImmune System SupportSuppress libido? (LH, FSH)

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Storage before Secretion

Large molecules easily stored because can’t leave readily

Small molecules often stored bound to accessory proteins

Some molecules actively/continuosly taken into vesicles

Steroid hormones (lipid soluble) tend to leak out soonHydrophobic steroid and thyroid hormones move in blood, bound to carrier proteins

Glandular SecretionResponse to stimulus

HormoneNeurotransmitterAction Potentialetc. (e.g., osmolarity and ADH)

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Hill et al. 2004ETC…

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Hormone ACTION! (receptors etc.)

1. Lipid Soluble

2. Lipid Insoluble

- Steroid and Thyroid Hormones (~long-lived)

- Bind Cytoplasmic Receptors, then to Nucleus- Directly affect transcription (therefore long-term)

- Through Membrane

- Bind cell-surface receptors- Often one or more 2nd messengers- Amplification~ Rapid, short-duration responses

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1. Lipid Soluble

2. Lipid Insoluble


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Possible 2nd messengers:


2. Lipid Insoluble Hormones and Intracellular Signaling

1. cAMP, cGMP (cyclic nucleotide monophosphates)

2. IP3, DAG (diacylglycerol; inositol phospholipids)

3. Ca2+ ions

General Model of Hormone Binding and Intracellular Signaling:

A few receptors with direct catalytic activity, but most via 2nd messengers :

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cAMP (cyclic nucleotide monophosphates)

GTP/GDP GTP/GDPcAMP

Protein kinase A


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Randall et al. 2002

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Glandular Secretion

Secretory Granules/Vesicles –similar to synaptic vesicles but usually larger

Exocytosis – common release mechanism

Regulation via Calcium –remember that free cytosoliccalcium concentration is correlated with exocytosis(including of NT, hormones, etc.)


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Fig 14.4Hill et al. 2004

PBCA

proinsulin

insulin

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Endocrine System

Tropic hormones =act on other

endocrine tissues(e.g., adrenal cortex,

thyroid, gonads)Negative Feedback

Anterior Pituitary


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Randall et al. 2002

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Major Players:

Pituitary (9 hormones)1. Anterior

(~nonneuronal)

2. Posterior(~neuronal control)

Endocrine System

Hypothalamus- (~7 neurohormones)- mostly peptides

(Portal Vessels)


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Neuroendocrine System

Posterior Pituitary

Oxytocin – uterine contractions, milk ejection

Antidiuretic Hormone (ADH) - water retention in kidney

Both are peptide hormones

Both are similar and highly conserved


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Neuroendocrine System

Posterior Pituitary

Similar, highly conserved peptide hormones

ADH

Randall et al. 2002

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Example:Endocrine System

Hypothalamus-corticotropin-releasing hormone

In response to cold, fright, pain etc…

Portal vessel

Anterior Pituitary-Adrenocorticotropin (ACTH)

Adrenal Cortex(corticosterone; stress hormones)

Blood Stream

Response (lizard example)


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Hormone Effects

Catecholamines(from medulla)

Glucocorticoids

inside

outside

Adrenal Gland

(from cortex)


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Fig 14.10, Hill et al. 2004

MammalianStress Response

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Glucocorticoids(from adrenal cortex)

Released in response to ACTH (Adrenocorticotropin) from Anterior Pituitary

Steroid hormones(lipid soluble) derived from cholesterol

1. Reproductive2. Kidney Function

(mineralocorticoids)3. Glucocorticoids

(mobilize a.a.s and glucose, etc.) Includes ‘Stress Hormones’

Cortisol, cortisone, corticosterone


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Vasopressin from Anterior Pituitary

Negative Feedback

Loop

More on aldosterone and other kidney hormones later

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Water and Electrolyte Balance Hormones

Randall et al. 2002

Post. Pit., signal from Hypothal

cAMP pathway

Calcitonin decrease Ca++ in blood; PTH increase Ca++ in blood

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Catecholamines(adrenal medulla) - Epi, Norepi

Fight/flight, exertion

Secretion regulated by sympathetic preganglionic

cholinergic neurons

Catecholamine receptors are Alpha and Beta adrenoreceptors

Alpha – smooth muscle contraction

Beta1 – cardiac muscle stimulantBeta2 – broncho/vaso dilation


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Thyroid Hormones

T3 and T4 (# of iodines)

Development, maturation, protein synthesis, metabolism

Also lipid soluble

Being cold can stimulate

cold

Thyroid gland


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Goiter:

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Thyroid Hormones

-Hyperthyroidism

-Hypothyroidism-Goiter-Iodized table salt

cold

Thyroid gland


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Insulin and Glucagon Regulate blood [glucose]

- Insulin in response to high [glu]

Both from pancreatic glands

- Glucagon in response to low [glu]

Insulin from beta cellsGlucagon from alpha cells

Type 1 Diabetes -when beta cells decrease insulin productionType 2 Diabetes-when insulin receptor signal pathway defective

Leads to glucose uptakeinto tissues ETC.

Causes glycogenolysis and glucose release from tissues (liver, muscles)

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Growth Hormone

Metabolic and developmental effects

Often has opposite effect of insulin

From Anterior Pituitary

-Stimulates gluconeogenesis-Reserves glucose for NS-Promotes use of fatty acids

as fuel

Works with Thyroid hormone in growth and development

Gigantism / Dwarfismab

norm

ality

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Growth Hormones

-Gigantism-Acromegaly

-Dwarfism

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Vertebrate Reproduction

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Reproductive Hormones

Steroid Hormones from Adrenal cortex and Gonads

Hypothalamus

GnRH

Anterior Pituitary

FSH, LH

Gonads, Adrenal Cortex


See Fig 14.1, Hill et al. 2004

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Male Sex Hormones

Testosterone and other androgens

Released from Leydig Cells in response to LH, FSH

FSH binding to Sertoli cells stimulates spermatogenesis


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Female Sex Hormones

Estrogens

Ova created and stored before birth (mammals and birds)

Repro cycle in 2 phases:Follicular and Luteal

FSH stimulates beginning of follicular phase –> development of ovarian follicles 9-47 Randall et al. 2002

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1- FSH ⇑Causing follicular maturation

2- LH ⇑

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FSH and LH help generate Estrogen (3)

This Estrogen causes hypothaland ant. pit. to release spike of LH and FSH leading to ovulation (4)

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Follicular Phase

(endometrium 5)

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= release of ovum (6)

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7- FSH, LH ⇓Estrogen ⇓

8- LH changes ruptured follicle into corpus luteum

Luteal Phase

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89- corpus luteumsecretes estrogen and progesterone which inhibit FSH, LH release from anterior pituitary by slowing GnRH

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10- progesterone leads to richer endometrium

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11- without fert. CL degenerates and cycle begins again

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Luteal Phase

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12- with fert. Chorionicgonadotropinmaintains CL, maintaining high levels of estrogen and progesterone; maintaining endometrium; follicular development inhibited 12

13- Placenta takes over hormone production

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Birth Control Pills?Progesterone and Estradiol – mimic early pregnancy and inhibit ovulation

Parturition (Birth)Oxytocin released in response to cervical stretchOxytocin causes uterine smooth muscle contractions

PositiveFeedback

Loop

Lecture 11, 26 Sept 2006 Vertebrate Physiology ECOL 437...

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