1 Chemical Signals in AnimalsChapter 45 Chemical Signals in Animals

2 Endocrine system regulates activity of target organs at distant sitessecretes hormones (chemical messengers)- secreted by neurosecretory cells or endocrine cells that travel in body fluids to target cells & bind to specific receptors eliciting response via ductless glands antagonistic hormones function in homeostasis pheromones – communication signals between different individuals of same species local regulators (neurotransmitters, growth factors, prostaglandins) affect target cells in immediate vicinity of secretion

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4 Hormone binding Steroid hormones – enter target cells & bindto specific protein receptors forming complexes that enter nucleus & bind to acceptor proteins on a chromosome initiating transcription Nonsteroid hormones – bind to specific receptors on membrane triggering a cascade of metabolic reactions within cells using messengers like cAMP & IP3 (inositol triphosphate)

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6 Invertebrate control systemsUsing endocrine/nervous integration Arthropods have well developed endocrine systems

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9 Vertebrate control systemshypothalamus & pituitary gland integration neurosecretory cells of hypothalamus integrate endocrine & neural function by influencing pituitary anterior pituitary produces several tropic hormones that act on other endocrine glands under direction from hypothalamus – produces TSH, FSH, LH, GH- stimulates growth factor production, prolactin (PRL) – diverse effects, ACTH – affects on adrenal cortex, MSH – skin pigmentation, endorphins – natural opiates

10 posterior pituitary – stores/releases 2 peptide hormones; repository for oxytocin & ADH – enhances water reabsorption

11 Vertebrate endocrine systemregulates growth, reproduction, & development & coordinates hormones thyroid – stimulates metabolism & influences development & maturation in vertebrates -secretes calcitonin – lowers blood Ca+ levels parathyroid – secretes PTH & raises blood Ca+ levels pancreas – secretes insulin & glucagon * increase in blood glucose levels stimulates insulin release *promotes glycogen storage in liver *stimulates protein synthesis & fat storage Type I diabetes – lack insulin Type II diabetes – loss of responsiveness of target cells to insulin

12 adrenal glands: medulla – releases epinephrine or norepinephrine; “fight or flight” response cortex – releases corticosteroids including sex hormones, glucocorticoids, & mineralocorticoids gonads – produce varying androgens, estrogens, & progestins pineal gland – secretes melotonin – influences skin pigmentation, biological rhythms & reproduction thymus – secretes thymosin

14 Endocrine/Nervous structurally, functionally, & chemically relatedmaintain homeostasis, development, & reproduction some endocrine glands have evolved from nervous tissue hormones such as epinephrine – used as signals for both systems

15 Chapter 46 Animal Reproduction

16 Asexual producing offspring whose genes came from 1 parentex: fission, budding, fragmentation with regeneration

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20 Sexual requires fusion of male & female gametes to form diploid zygoteadvantages: enhances reproductive success in changing environments variations through: a) parthenogenesis – eggs develop without fertilization b) hermaphroditism – has both M & F reprod. Systems c) sequential hermaphroditism – individual reverses its sex during its lifetime protogynous – female 1st protoandrous – male 1st ex: wrasses – sex reversal assoc. w/age & size

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23 Reproductive cycles Controlled by hormones & environmental cues, such as: temp. changes rainfall day length seasonal lunar cycles

24 Sexual methods external fertilization – requires critical timing, mediated by env. cues, pheromones &/or courtship *most common in aquatic or moist env. where zygote develops without desiccation & heat stress internal fertilization – requires important behavioral interactions between M & F, compatible copulatory organs *usu. fewer zygotes, but increased protection of embryos & parental care of young

25 Reproductive systems Invert. systems range from simple gamete production by undifferentiated cells in body cavity to complex assemblages of M & F gonads w/ accessory tubes & glands that carry/protect embryos Vert. systems are similar, but nonmammals usu. have a cloaca

26 Human reproduction male external genitalia – scrotum, penisaccessory glands – add secretions to semen female internal – 2 ovaries, oviducts, uterus, vagina -external – vestibule w/ urethra & vagina openings, labia minora & majora, clitoris -Bartholin’s gland – secretes mucus for lubrication -mammary glands – (in breasts) evolved in association w/ parental care

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31 Sexual response hormones –androgens – (M) cause dev. of primary & secondary sex characteristics; secretion of androgens & sperm produced both controlled by hypothalmic & pituitary hormones -(F) – secreted in rhythmic fashion: menstrual (endometrial bleeding) & estrous (sexual receptivity) cycles cycle: endometrium thickening in preparation for possible implantation

32 Human menstrual cycle menstrual flow phase – shedding endrometrium;~5 days proliferative phase – follicle produces estrogen that stimulates thickening; ~1-2 weeks secretory phase – continuing thickening, becomes more vascularized & secretes fluid rich in glycogen; ~2 weeks *if no implantation occurs, phase repeats

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34 Ovarian cycle follicular – several follicles in ovary grow, egg cell enlarges luteal – follicular tissue transformed into corpus luteum gonadotropin–releasing hormone (GnRH) from hypothalamus & FSH & LH from anterior pituitary gland, estrogen & progesterone from ovaries coordinate menstrual & ovarian cycles

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39 Chapter 48 Nervous Systems

40 Function Sensory input, integration, & motor outputCNS (central nervous system) – integrates info. *consists of brain, spinal cord PNS (peripheral nervous system) – communicate sensory & motor signals between CNS & rest of body *sensory neurons – carry info. from CNS to target cells

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43 Neurons transmit signalsinterneurons of CNS integrate sensory & motor output supporting cells (glial cells) – support, insulate, protect neurons a) astrocytes – blood/brain barrier b) oligodendrocytes – insulate w/myelin sheath (Schwann cells in PNS)

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49 Synaptic terminals at ends of axons; release neurotransmitters –molecules released into synapses thereby relaying neural signals to dendrites or cell bodies of other neurons or effectors impulses – action potentials (electrical signals transmitted along neuronal membranes) potential is unequal due to unequal distribution of ions (K+ or Na+) across plasma membrane stimulus changes permeability to ions & either depolarizes or hyperpolarizes membrane; magnitude proportional to stimulus strength

50 impulse is rapid, transient depolarization of neuron’s membranesynapses conduct signals from axon of presynaptic cell to dendrite or cell body of postsynaptic cell electric synapses directly pass an action potential between 2 neurons by gap junctions depolarizaton stimulates fusion of synaptic vesicles with presynaptic membrane & release of neurotransmitter molecules into synaptic cleft neurotransmitters bind to receptor proteins assoc. w/particular ion channels or postsynaptic membrane Ach (acetylcholine) is common in verts. & inverts. (also dopamine, serotonin, epinephrine, norepinephrine), several AA’s, endorphins, nitric oxide (signal othe cells)

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54 PNS Sensory – somatic (afferent) – visceral Motor – (efferent)-somatic (voluntary) – signals skeletal muscles -autonomic (involuntary) – regulates smooth & cardiac muscles -sympathetic -parasympathetic *usu. antagonistic in effect on target organs

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