1EggEgg LarvaLarva PupaPupa AdultAdult

CHEMICAL SIGNALS IN ANIMALSCHEMICAL SIGNALS IN ANIMALS

ObjectivesObjectives

• State State the major functions of the major functions of hormoneshormones..

• Differentiate Differentiate between between endocrineendocrine and and exocrineexocrine glands. glands.

• Compare Compare how amino acid-based hormones act on their how amino acid-based hormones act on their target cells with how steroid or thyroid hormones act on target cells with how steroid or thyroid hormones act on their target cells.their target cells.

• Identify Identify the relationship between the hypothalamus and the relationship between the hypothalamus and the pituitary gland in the release of hormones.the pituitary gland in the release of hormones.

• List List the functions of the major endocrine glands and the functions of the major endocrine glands and hormones.hormones.

Function and SecretionFunction and Secretion

• Hormones are substances secreted by Hormones are substances secreted by cells that act to regulate the activity of cells that act to regulate the activity of other cells in the body.other cells in the body.– Hormones affect all cells in the body Hormones affect all cells in the body

and are made and secreted by and are made and secreted by endocrine glands.endocrine glands.

• Endocrine glands are ductless organs that Endocrine glands are ductless organs that secret hormones either into the secret hormones either into the bloodstream or the fluid around cells.bloodstream or the fluid around cells.

• The endocrine glands can be found The endocrine glands can be found through out the body and are collectively through out the body and are collectively known as the endocrine system.known as the endocrine system.

• Endocrine glands, such as the pancreas, Endocrine glands, such as the pancreas, can also be exocrine glands.can also be exocrine glands.

– Exocrine glands secrete substances Exocrine glands secrete substances through ducts to specific locations through ducts to specific locations inside and outside the body.inside and outside the body.

IntroductionIntroduction

• Nervous and endocrine systems are the main internal Nervous and endocrine systems are the main internal communication and regulation systems.communication and regulation systems.

• The animal hormone-secreting cells constitute the endocrine The animal hormone-secreting cells constitute the endocrine system.system.

• Hormone secreting organs are called Hormone secreting organs are called Endocrine GlandsEndocrine Glands (ductless (ductless glandsglands الصماء الصماء الغدد While ). While Exocrine GlandsExocrine Glands secrete substances secrete substances .( الغددthrough ducts to specific locations inside and outside the body.through ducts to specific locations inside and outside the body.

• Hormone is a chemical signal secreted into blood stream and Hormone is a chemical signal secreted into blood stream and regulates communicating messages within the body.regulates communicating messages within the body.

• Target cell is the site that reached by the hormone to which it Target cell is the site that reached by the hormone to which it responds.responds.

• Complete changes in the body is regulated by hormones (e.g. Complete changes in the body is regulated by hormones (e.g. metamorphosis in insects).metamorphosis in insects).

• Types of hormones are [Types of hormones are [Polypeptide H., Amino acid derivatives H Polypeptide H., Amino acid derivatives H or Steroid H.or Steroid H.]. ].

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II): Protein hormones): Protein hormones::

Bind to a receptor protein on the surface of the target cell whichBind to a receptor protein on the surface of the target cell which will trigger will trigger signal transduction pathwaysignal transduction pathway..

Types of Hormones and Mechanism Types of Hormones and Mechanism of chemical signaling:of chemical signaling:

Hormones can be grouped into two types based on their structure. Hormones can either be amino acid-based hormones or steroid hormones.

– Amino acid based-hormonesAmino acid based-hormones (protein hormones) are made of amino acids, either a single modified amino acid or a protein made of 3-200 amino acids, and are water soluble.

– Steroid hormonesSteroid hormones are lipid hormones that the body makes from cholesterol and are fat soluble.

• Similar to steroid hormones are thyroid hormones.

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IIII) Steroid hormones:) Steroid hormones:

Penetrate the cell and bind to a receptor protein Penetrate the cell and bind to a receptor protein inside the targetinside the target cell. This cell. This also will trigger also will trigger signal transduction pathwaysignal transduction pathway (for triggering mRNA (for triggering mRNA transcription for synthesizing a specific protein).transcription for synthesizing a specific protein).

• Estrogen, progesterone, vitamin D and NO.Estrogen, progesterone, vitamin D and NO.– Usually, the intracellular receptor activated by a hormone is a Usually, the intracellular receptor activated by a hormone is a

transcription factor.transcription factor.

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• Tropic hormones:Tropic hormones: )الهرمونات المحفزة )المنبهة Target other endocrine glands and are important to

understanding chemical coordination.

• Many endocrine organs contain specialized nerve cells called Many endocrine organs contain specialized nerve cells called neurosecretory cellsneurosecretory cells that secret hormones. that secret hormones.

• The hormone epinephrine has two functions:The hormone epinephrine has two functions:– As a hormone of the endocrine system.As a hormone of the endocrine system.– As a signal in the nervous system. As a signal in the nervous system.

• Feedback is common in regulation the activity of both endocrine Feedback is common in regulation the activity of both endocrine and nervous systems (homeostasis)and nervous systems (homeostasis)::– Calcitonin and parathyroid hormones play an important role in Calcitonin and parathyroid hormones play an important role in

maintaining the concentration of the blood calcium constant.maintaining the concentration of the blood calcium constant.– They are secreted from thyroid and parathyroid glands respictively.They are secreted from thyroid and parathyroid glands respictively.

• Hormones regulate the development of Hormones regulate the development of invertebrates (e.g. insects) invertebrates (e.g. insects)

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Tropic hormonesTropic hormones((الهرمون المنبه للغددالهرمون المنبه للغدد))

TTarget other arget other endocrineendocrineglandsglands and are and areimportant to important to understandingunderstandingchemical coordination.chemical coordination.

• Human has Human has 9 9

endocrine glandsendocrine glands..

The Vertebrate Endocrine SystemThe Vertebrate Endocrine System

Fig. 45.5, Page 960

الصنوبالنخاميرية

ةالدرقية

الكظرية

The hypothalamus and the pituitary gland, control the initial release of many hormones for the endocrine system.

The The hypothalamushypothalamus is the area of the is the area of the brain that coordinates many activities of brain that coordinates many activities of the nervous and endocrine systems.the nervous and endocrine systems.

The The pituitarypituitary gland has two parts, gland has two parts, anterior and posterior, and stores and anterior and posterior, and stores and releases hormones produced by the releases hormones produced by the hypothalamushypothalamus

Neurosecretory cells of the Neurosecretory cells of the hypothalamus produce hormones.hypothalamus produce hormones.

a)a) Releasing hormonesReleasing hormones stimulate the stimulate the anterior pituitary (anterior pituitary (adenohypophysisadenohypophysis) ) to secrete hormones.to secrete hormones.

b)b) Inhibiting hormonesInhibiting hormones prevent the prevent the anterior pituitary from secreting anterior pituitary from secreting hormones.hormones.

The hypothalamus and pituitary integrate many The hypothalamus and pituitary integrate many functions of the vertebrate endocrine systemfunctions of the vertebrate endocrine system

HypothalamusHypothalamus

PosteriorPosteriorpituitarypituitary

AnteriorAnteriorpituitarypituitary

A)- Anterior pituitary hormones.A)- Anterior pituitary hormones.1)1) Growth hormone (GH):Growth hormone (GH): a a protein. protein.

• Stimulates growth and metabolism.Stimulates growth and metabolism.• Secretion regulated by hypothalamic hormones.Secretion regulated by hypothalamic hormones.• Acts directly on tissues or acts Acts directly on tissues or acts viavia growth factorsgrowth factors..

• Gigantism:Gigantism: العملقةالعملقة excessive GH during excessive GH during developmentdevelopment..

• AcromegalyAcromegaly: excessive GH production during : excessive GH production during adulthoodadulthood..• Hypopituitary dwarfism Hypopituitary dwarfism القزميةالقزمية: childhood GH deficiency.: childhood GH deficiency.

2)2) Prolactin (PRL):Prolactin (PRL): a a proteinprotein..• Stimulates milk production and secretion from Stimulates milk production and secretion from mammary glandmammary gland

.This secretion regulated by hypothalamic hormones.. This secretion regulated by hypothalamic hormones .الغدد اللبنيةالغدد اللبنية

3)3) Gonadotropins (Gonadotropins (Gonotropic Gonotropic محفز للمناسلمحفز للمناسل): ): glyocoproteinsglyocoproteins..• Follicle-stimulating hormone (FSH).Follicle-stimulating hormone (FSH).

– Stimulates production of Stimulates production of spermssperms and and ovaova..– Secretion regulated by hypothalamic hormones.Secretion regulated by hypothalamic hormones.

• Luteinizing hormone (LH) Luteinizing hormone (LH) الم+حفز لتكوين الجسم األصفرالم+حفز لتكوين الجسم األصفر..– Stimulates ovaries and testes. Stimulates ovaries and testes. – Secretion regulated by hypothalamic hormones.Secretion regulated by hypothalamic hormones.

1)- Pituitary gland:1)- Pituitary gland: Secrets 9 hormonesSecrets 9 hormones ( 7 hormones by the anterior part and 2 hormones by the posterior part).the anterior part and 2 hormones by the posterior part).

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4)4) Thyroid-stimulating hormone (TSH):Thyroid-stimulating hormone (TSH): a a glycoproteinglycoprotein..• Stimulates thyroid gland.Stimulates thyroid gland.

• Secretion regulated by thyroxine in blood.Secretion regulated by thyroxine in blood.

• Secretion regulated by hypothalamic hormones.Secretion regulated by hypothalamic hormones.

5)5) Adrenocorticotropic hormone (ACTH):Adrenocorticotropic hormone (ACTH): a a peptidepeptide• Stimulates adrenal cortex secretion of glucocorticoidsStimulates adrenal cortex secretion of glucocorticoids

• Secretion regulated by glucocorticoids and hypothalamic Secretion regulated by glucocorticoids and hypothalamic hormones.hormones.

6)6) Melanocyte-stimulating hormone (MSH):Melanocyte-stimulating hormone (MSH): a a peptidepeptide..• May play a role in fat metabolism.May play a role in fat metabolism.

7)7) EndorphinsEndorphins: : peptidespeptides..• Inhibit pain perception.Inhibit pain perception.

• Effects mimicked by heroin and other opiate drugs.Effects mimicked by heroin and other opiate drugs.

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The anterior pituitary gland hormonesThe anterior pituitary gland hormones

Also called gonadotropine Also called gonadotropine hormones hormones المناسل المناسل هرمونات هرمونات

Adrenocorticotropic

Melanocyte-stimulating H.

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B)- Posterior pituitary hormones.B)- Posterior pituitary hormones.– OxytocinOxytocin: a peptide.: a peptide.

• Stimulates contraction of the uterus and Stimulates contraction of the uterus and mammary glandsmammary glands..

• Secretion regulated by the nervous system.Secretion regulated by the nervous system.

– Antidiuretic hormone (ADH):Antidiuretic hormone (ADH): م!ضاد إلدرار البولم!ضاد إلدرار البول a peptide.a peptide.• Promotes retention of Promotes retention of

water by the water by the kidneyskidneys (in Kidney tubules).(in Kidney tubules).

• High level decreases High level decreases urination and urination and vicevice versaversa..

• Secretion regulated by Secretion regulated by water/salt balance.water/salt balance.

Antidiuretic HAntidiuretic H

Summary of Hormones Secreted by the Pituitary GlandSummary of Hormones Secreted by the Pituitary Gland

2- Pineal gland:2- Pineal gland: الغدة الصنوبريةالغدة الصنوبرية

It is a small mass of tissue near the center of the mammalian It is a small mass of tissue near the center of the mammalian brain and brain and involved in involved in biorhythmsbiorhythms..

– The pineal gland secretes the hormone, The pineal gland secretes the hormone, melatoninmelatonin, an , an amineamine..• Involved in biological rhythms associated with reproduction.Involved in biological rhythms associated with reproduction.

• Secretion regulated by light/dark cycles.Secretion regulated by light/dark cycles.

Pineal glandPineal gland

Pituitary hormonesPituitary hormones