Presentation on theme: "Chemical signaling within the animal body"— Presentation transcript:
1Chemical signaling within the animal body Chapter 30
2Hormones A hormone is a chemical signal produced in the body. HypothalamusPinealglandPituitaryThyroidPancreasTestes(in males)Ovaries(in females)AdrenalglandsThymusParathyroid glands(attached to the thyroid)A hormone is a chemical signal produced in the body.It typically acts at a site distant from where it was produced.Most hormones are produced in glands that are completely enclosed in tissue.These glands are called endocrine glands.
3HormonesThere are three big advantages to using chemical hormones as messengers rather than speedy electrical signals (like nerve signals).Chemical molecules can spread to all tissues via the blood.Chemical signals can persist much longer than electrical ones.Many different kinds of chemicals can act as hormones.
4HormonesThe glands that produce hormones are generally controlled by the nervous system.The endocrine system and the motor nervous system are the two main routes the CNS uses to issue commands to the organs of the body.The two are so closely linked that they are often considered a single system—neuroendocrine system.The hypothalamus is the main switchboard of the neuroendocrine system.
5HormonesThe CNS regulates the body’s hormones through a chain of command.For example, the hypothalamus controls the pituitary gland with thyrotropic-releasing hormone (TRH).This causes the pituitary to release or thyroid-stimulating hormone (TSH).TSH then causes the thyroid gland to release thyroid hormones.The hypothalamus also secretes inhibiting hormones that keep the pituitary from secreting specific hormones.
6HormonesHormones are effective messengers within the body because a particular hormone can influence a specific target cell.Cells that the body has targeted to respond to a particular hormone have receptor proteins shaped to fit that hormone and no other.
7Hormones polypeptides glycoproteins amines steroids Hormones secreted by endocrine glands belong to four different chemical categories:polypeptidesglycoproteinsaminessteroids
8HormonesThe path of communication taken by a hormonal signal is a series of simple steps:Issuing the command - the hypothalamus controls the release of many hormones.Transporting the signal - most are transported throughout the body by the bloodstream.Hitting the target - the hormone binds to a receptor on the target cell.Having an effect - when the hormone binds to the receptor protein, the protein changes shape and triggers a change in cell activity.
9Key Biological Process: Hormonal communication DehydrationBlood volume andpressure drops.Osmotic concentrationin the blood increases.3Osmoreceptors14Reduced urinevolume causesincreased waterretention.HypothalamusADHAntidiuretichormone (ADH)24Increasedvasoconstrictionleads to higherblood pressure.Bloodstream3Posteriorpituitary1ADHGenerally, a part ofthe neuroendocrinesystem receivessensory informationand issues acommand in the formof a chemicalmessenger (hormone).234The hormonereaches the targetcells and binds to thecell receptors.The hormone-recept or complextriggers changes in thetarget cells.The hormone istransported to targetcells via thebloodstream.
10How Hormones Target Cells The steroid hormones are recognized by protein receptors located in the cytoplasm or nucleus of the target cell.Steroids are manufactured from cholesterol.Steroid hormones can pass across the lipid bilayer of the cell plasma membrane.
11How Hormones Target Cells The complex of a steroid hormone and its receptor inside the target cell bind to DNA in the nucleus.This activates the transcription of a specific gene and a protein is subsequently synthesized.
12How steroid hormones work Tissue fluidBlood plasmaTarget cellESteroidhormoneETransportproteinPlasma membrane1Cytoplasm1Estrogen (E) is a lipid soluble steroidhormone and thus readily passes through theplasma membrane of cells lining the uterus.E2Inside the cell, estrogen binds to a specific receptorprotein associated with the DNA in the nucleus.4Receptorprotein3The estrogen-receptor complex activates thetranscription of genes.Steroid hormone-receptor complexProteinsynthesis42Protein synthesis is induced. In this case,the protein produced is a receptor foranother steroid protein, progesterone.5Later, when progesterone enters the cell, it binds tothe receptor and stimulates the cell to produce enzymesthat help prepare the uterus to nourish an embryo in theevent of a pregnancy.5DNA3mRNAProgesteronereceptorNucleus
13How Hormones Target Cells The receptors for peptide hormones are embedded in the plasma membrane.The binding of the hormone to the receptor triggers changes in the cytoplasmic end of the receptor protein.Using second messengers, this change is amplified and causes changes in the cellSecond messengers activate enzymes.one of the most common is cyclic AMP (cAMP).
14How peptide hormones work 1The peptide hormonebinds with its membranereceptor.2The hormone-receptorcombination triggers aseries of biochemicalreactions that producesthe second messenger.Peptidehormone3The second messengertriggers a series ofreactions that leads toaltered cell functions.PP1Receptor2Productionof secondmessenger3Alteration ofcell activity
15How Hormones Target Cells A single hormone binding to a receptor in the plasma membrane can result in the formation of many second messengers in the cytoplasm.Cyclic AMP is made from ATP by an enzyme that removes two phosphate units.Each second messenger can activate many molecules of a certain enzyme.
16Key Biological Process: Second messengers 1Hormone(first messenger)After a peptide hormone binds to its receptor, thehormone-receptor complex activates adenylyl cyclase.Receptor21Adenylyl cyclase converts ATP into cyclic AMP(cAMP), and cAMP acts as a second messengerthat activates enzymes called protein kinases.3Protein kinases catalyze a wide variety ofactions, depending on the nature of the firstmessenger. Because of the presence of asecond messenger, the effect on the cell isgreatly amplified.Adenylylcyclase(Secondmessenger)ATPcAMP23Protein kinase(inactive)Protein kinase(active)Altered cell function(regulates enzymes,synthesizes proteins, secretes molecules)
17The Hypothalamus and the Pituitary The pituitary gland is located beneath the hypothalamus and is the location where nine hormones are produced.These hormones act principally to influence other endocrine glands.The pituitary consists of two lobes:Posterior pituitary regulates water conservation and, in women, milk letdown and uterine contraction.Anterior pituitary regulates other endocrine glands.
18The Hypothalamus and the Pituitary The hypothalamus and the posterior pituitary are connected by a tract of neurons.Hormones are produced by cell bodies in the hypothalamus and transported to the posterior pituitary.Antidiuretic hormone (ADH) regulates the kidney’s retention of water.Oxytocin initiates uterine contractions during childbirth and milk release in mothers.
19The Hypothalamus and the Pituitary The anterior pituitary is a complete gland that produces the hormones that it secretes.Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce thyroxine, which in turn stimulates oxidative respiration.Adrenocorticotropic hormone (ACTH) stimulates the adrenal gland to produce hormones.Growth hormone (GH) simulates the growth of muscle and bone throughout the body.
20The Hypothalamus and the Pituitary Follicle-stimulating hormone (FSH)In females, it triggers the maturation of egg cells and stimulates the release of estrogen.In males, it regulates sperm development.Luteinizing hormone (LH)In females, it triggers ovulation of a mature egg.In males, it stimulates the gonads to produce testosterone.
21The Hypothalamus and the Pituitary Prolactin (PRL) stimulates the breasts to produce milk.Melanocyte-stimulating hormone (MSH) stimulates, in reptiles and amphibians, color changes in the epidermis.Its function in humans is poorly understood.
23The Hypothalamus and the Pituitary Cell bodyAxons toprimarycapillariesHormonesPortal venulesHypophysealportal systemAnteriorpituitaryPosterior pituitaryPituitary stalkPrimaryThe hypothalamus controls production and secretion of the anterior pituitary hormones by means of a family of special hormones.Neurons in the hypothalamus secrete both releasing and inhibiting hormones.
24The Hypothalamus and the Pituitary Negative feedback (feedback inhibition) often controls the release of hormones from the hypothalamus and anterior pituitary.When enough of the target hormone has been produced, the hormone then feeds back to the hypothalamus and anterior pituitary and inhibits the release of stimulating hormones.–HypothalamusInhibitionReleasing hormones(TRH, CRH, GnRH)Anterior pituitaryTarget glandsHormones(Thyroid, adrenal cortex, gonads)Tropic hormones(TSH, ACTH, FSH, LH)
25Release of stored glucose, The PancreasThe pancreas has both exocrine and endocrine functions.It secretes digestive enzymes and hormones.The hormones, produced in the islets of Langerhans, are insulin and glucagon.Insulin promotes the uptake of glucose and the accumulation of glycogen in the liver and triglycerides in fat cells.Glucagon causes liver cells to release stored glucose and to break down triglycerides.Between mealsBlood glucosePancreasAfter a mealPancreatic isletsInsulin secretionGlucagon secretionCellular uptakeof glucoseRelease of stored glucose,break down of fat
26The PancreasDiabetes mellitus is a serious disorder in which affected individuals are unable to take up glucose from the blood.There are two kind of diabetes mellitus:Type I is a hereditary autoimmune disease in which the islets of Langerhans are attacked, resulting in abnormally low insulin secretion.Type II is when cells don’t respond to insulin, sometimes due to a reduction in the number of insulin receptors in the target tissue.
27The Thyroid, Parathyroid, and Adrenal Glands The thyroid gland makes several hormones.Thyroxine increases metabolic rate and promotes growth.Calcitonin inhibits the release of calcium from bones and promotes the uptake of calcium by bones.
28The Thyroid, Parathyroid, and Adrenal Glands The parathyroid glands are four small glands attached to the thyroid.These glands produce parathyroid hormone (PTH), a hormone that is absolutely essential for survival because it regulates calcium levels in the blood.Calcium ions are necessary for muscle contractions, such as those of the heart.PTH stimulates the release of calcium from bone.Calcitonin (released from the thyroid gland) has the opposite effect.
29Maintenance of proper calcium levels in the blood LOW CALCIUM LEVELSTIMULATES PTHSECRETIONHIGH CALCIUM LEVELSTIMULATES CALCITONINSECRETIONCa++InactiveosteoblastCa++Ca++Ca++Ca++PTH stimulatesosteoclast(breaking downbone matrix)Calcitoninstimulatesactiveosteoblast(increasingbonematrix)BonematrixBonematrixOsteocyte(in lacuna)(a)(b)
30The Thyroid, Parathyroid, and Adrenal Glands The adrenal glands are located just above the kidney and each is comprised of two parts.The medulla is the inner core and produces epinephrine and norepinephrine.The cortex is the outer region and produces the steroid hormones cortisol and aldosterone.
31The Thyroid, Parathyroid, and Adrenal Glands The adrenal medulla releases epinephrine (adrenaline) and norepinephrine in times of stress.These hormones act as emergency signals that stimulate rapid deployment of body fuel.The adrenal cortex producesCortisol, which acts to maintain nutritional well-being.It is also released in times of stress but can become a chronic problem if stress continues.Aldosterone, which affects water reabsorption in the kidney and affects both blood volume and blood pressure.