Gen Bio 116 Exam 2 Study Guide PDF

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Summary

Plant Hormonal Control A. The 5 Classic Plant Hormones:B. Additional Plant Hormones: Brassinosteroids Jasmonates Strigolactones induce cell elongation and division in stem segments
- molecules derived from fatty acid, linolenic acid are carotenoid derived hormones and extracellular signals Auxin (...

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Plant Hormonal Control A. The 5 Classic Plant Hormones: Auxin (IAA) - produced in shoot tips & young leaves

Cytokinins - synthesized in actively growing tissues (roots, fruits, embryo) - stimulate cell division and differentiation, apical dominance, aging

Gibberellins (GA) - produced in apical & root meristems, young leaves, developing seeds - affect stem elongation, fruit growth, and seed germination

Abscisic acid (ABA) - abscission: dropping of leaves

Ethylene - can be produced by most parts of the plant

- can be produced by nearly all cells

- stimulates cell growth (elongation) and plant development

- from roots, move up xylem to target tissue

- slows down growth, acts as antagonist to other hormones that promote growth

- inhibits growth at higher concentrations

- in combo with auxin coordinates cell differentiation

- activate enzymes that loosen cell walls and allow entry of expansin proteins (dwarf plants can grow taller; bolting, rapid growth of stalk)

- is a gas produced in response to stress (drought, flooding, injury, infection)

- stimulation of H+ pumps increases membrane potential  induces entrance of ions  water comes in via osmosis  higher turgor/longer cells

- increase in auxin  root formation; increase in cytokinins shoot bud formation - affect ability of apical buds to suppress axillary bud formation in combo with auxins & strigolactones

- transported from tips to base only (polar transport)

- decreases pH of cell walls - regulate plant development; polar transport controls spatial organization - controls branching/leaf vein patterns, affects leaf arrangement, influences vascular cambium

- can slow aging of certain organs - stimulate RNA and protein synthesis

- mobilize nutrients from surrounding tissue

B. Additional Plant Hormones: Brassinosteroids - induce cell elongation and division in stem segments

- promote flower development when combined with auxin (spray grapes  larger fruit) - embryos are rich source of gibberellins - water absorption promotes release of gibberellins from embryo  signals break of dormancy, starts germination - in barley, signals endosperm to secrete digestive enzymes  hydrolyze nutrients in endosperm

Jasmonates  - molecules derived from fatty acid, linolenic acid

- transported in xylem and phloem

- ratio of ABA against other hormones determines outcome

- two main effects are seed dormancy and drought tolerance - increased ABA in seeds inhibit germination; removal/inactivation of ABA  germination - wilting plants accumulate ABA  stomata close and reduce transpiration; ABA affects secondary messengers such as Ca2+ which causes K+ channels to open  loss of K+ & water

- also produced during fruit ripening, programmed cell death, and leaf abscission - response to stress: maneuver of shoot to avoid obstacles and minimize damage to meristems; slow stem elongation, thickening of stem, curvature; ethylene drops, vertical growth resumes - senescence = programmed death, apoptosis  ethylene released, signal enzymes -less auxin, more ethylene  hydrolysis of abscission

Strigolactones - are carotenoid derived hormones and extracellular signals

- slow leaf abscission and promote xylem and phloem differentiation

- produced in various parts of plant; travel in phloem

- promote root growth at low concentrations; inhibit at high concentrations

 - help regulate many functions including fruit ripening, pollen production, root growth, seed germination, nectar secretion

- promote seed germination and pollen tube elongation

- also produced in response to herbivory and pathogen invasion

- present in all cell plant tissues; usually act near site of synthesis

 - produced in roots in response to low phosphate or high auxin flow from shoot - move through xylem  - can also be exuded from roots - promote seed germination, control apical dominance, attract mycorrhizal fungi to root, attract parasitic plants to roots of host plants

C. Signal transduction pathways: the way through which plant cells are able to sense their environment 1. reception: signals are detected by receptor proteins that change shape in response to stimulus 2. transduction: conversion of signal from outside cell to create a specific cellular response; involves second messengers (small molecules and ions in the cell that amplify the signal and transfer it from the receptor to other proteins that carry out the response) 3. response: involve the increased activity of particular enzymes; occurs because of structural modification of enzyme OR increased/decreased production of enzyme Endocrine I A. Regulating or conforming:  1. regulators: animals using internal mechanisms to control internal change relative to external variability  2. conformers: allow internal change in relation to external environmental changes  B. Homeostasis: dynamic equilibrium: 1. positive feedback: response reinforces stimulus, amplifies stimulus and response 2. negative feedback: reduces the initial stimulus; restores pre-existing state C. Chemical signals: - endocrine signaling: secreted molecules diffuse into the bloodstream, trigger responses in target cells anywhere in the body - paracrine signaling: diffuse locally, trigger responses in neighboring cells - autocrine signaling: diffuse locally, trigger responses in the cells that secrete them - synaptic signaling: neurotransmitters diffuse across synapses, trigger responses in cells of target tissues - neuroendocrine signaling: neurohormones diffuse into the bloodstream, trigger responses in target cells anywhere in the body D. Water-soluble and lipid-soluble hormones: Water-soluble signaling molecules Lipid-soluble signaling molecules - receptors in plasma membrane - receptors in cytoplasm or nucleus  - response can be: activation of enzyme, - response often changes gene expression change in uptake (or secretion) of specific molecule, rearrangement of cytoskeleton, receptor entering nucleus and affecting transcription of specific genes - ex. estradiol made in ovary of bird affect egg yolk - ex. epinephrine made by adrenal glands affect liver production cells Endocrine II A. Human endocrine glands & their hormones: Endocrine gland Hormones Pineal gland - melatonin: participates in regulation of biological rhythms Hypothalamus - hormones released from posterior pituitary (oxytocin, ADH)

- releasing and inhibiting hormones: regulate anterior pituitary - follicle-stimulating hormone (FSH) and luteinizing hormone (LH); stimulate ovaries and testes - thyroid-stimulating hormone (TSH): stimulates thyroid gland - adrenocorticotropic hormone (ACTH): stimulates adrenal cortex - prolactin: stimulates mammary gland cells - growth hormone (GH): stimulates growth and metabolic functions Posterior pituitary - oxytocin: stimulates contraction of smooth muscle cells in uterus and mammary glands - antidiuretic hormone (ADH, also called vasopressin): promotes retention of water by kidneys; influence social behavior and bonding Thyroid gland - thyroid hormone (T3 and T4): stimulates and maintains metabolic processes - calcitonin: lowers blood calcium level Parathyroid glands - parathyroid hormone (PTH): raises blood calcium level Adrenal medulla - epinephrine and norepinephrine: raise blood glucose level; increase metabolic activities; constrict certain blood vessels Adrenal cortex - glucocorticoids: raise blood glucose level - mineralocorticoids: promote reabsorption of Na+ and excretion of K+ in kidneys Pancreas - insulin: lowers blood glucose level - glucagon: raises blood glucose level Ovaries - estrogen*: stimulate uterine lining growth; promote development and maintenance of female secondary sex characteristics - progestin*: promote uterine lining growth Testes - androgen*: support sperm formation; promote development and maintenance of male secondary sex characteristics * found in both males and females, but with a major role in one sex B. Hormone secretion regulatory pathways organized into 2 basic types: Simple endocrine pathway Simple neuroendocrine pathway - endocrine cells respond directly to internal/external - involve more than one cell type and have more steps environmental stimuli - secrete hormone - stimulus received by sensory neuron  - hormone travels via blood to target cells and - sensory neuron stimulates neurosecretory cell interact with specific receptors Anterior pituitary

- signal transduction in target cell occurs - physiological response then occurs

- neurosecretory cell secretes neurohormones - neurohormones diffuses into blood; travels to target cells - example: controlling pH in duodenum - example: regulation of milk production during nursing C. Coordination of endocrine system with nervous system: 1. insects - almost all insects belong to subclass Pterygota (includes winged insects) - these insects have either hemimetabolous or holometabolous development  hemimetabolous: incomplete or partial metamorphosis (juveniles resemble adults)  holometabolous: complete metamorphosis (immature stages very different from adults) - holometabolous insects have neuroendocrine coordination of larvae development into adults

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 - moth neurosecretory cells produce prothoracicotropic hormone (PTTH); stored in corpora cardiac  PTTH signals prothoracic gland to release hormone ecdysteroid  ecdysteroid released in bursts  PTTH also stimulates corpora allata to secrete juvenile hormone (JH) which determines result of molt development  low concentration of JH = metamorphosis to adult  2. vertebrates  - coordination of endocrine signaling relies mostly on region of brain called hypothalamus  (1) hypothalamus receives signals from nerves throughout body; initiates endocrine signaling  (2) signals travel to pituitary gland at base of hypothalamus  (3) pituitary is actually 2 fused glands with very different functions  - posterior pituitary hormones (extension of hypothalamus)  (1) travel to posterior pituitary within long axons of neurosecretory cells  (2) stored and released in response to nerve impulses from hypothalamus antidiuretic hormone (vasopressin) o regulates kidney function, increases H2O retention in kidneys o important in social behavior, sexual motivation, pair bonding oxytocin o functions in milk secretion in mammals o regulates uterine contractions at birth o influence behavior: maternal care, pair bonding, sexual activity  - anterior pituitary hormones (synthesizes/secretes hormones in response to hypothalamus)  (1) control metabolism, osmoregulation, and reproduction in humans  (2) release of all hormones is under control of hypothalamus  (3) each hypothalamus hormone one of two types based on effect to anterior pituitary hormones releasing hormone or inhibiting hormone  (4) releasing/inhibiting hormones drain into portal vessels, which drain into anterior pituitary (5) anterior pituitary then releases pituitary hormones that target other cells around body (6) some hormones hypothalamus, anterior pituitary, and target endocrine glands form hormone cascade pathways; call these tropic hormones or tropins hormone from target endocrine gland secretes hormone that acts on specific target tissue D. Thyroid gland function/regulation; hormone cascade pathway: - thyroid gland produces thyroid hormone and calcitonin - thyroid hormone: (1) stimulus: thyroid hormone levels drop below the normal range (2) hypothalamus secretes thyrotropin-releasing hormone (TRH) into the blood; portal vessels carry TRH to the anterior pituitary (3) TRH causes the anterior pituitary to secrete thyroid-stimulating hormone (TSH, also known as thyrotropin) into the circulatory system - circulation throughout body via blood (4) TSH stimulates endocrine cells in the thyroid gland to secrete thyroid hormone (T3 and T4) into the circulatory system - circulation throughout body via blood (5) thyroid hormone levels increase in the blood and body tissues, returning to the normal range; thyroid hormone acts on target cells throughout the body to control bioenergetics (help maintain normal bp, heart rate, muscle tone, regulate digestive/reproductive functions)

(6) thyroid hormone blocks TRH release from the hypothalamus, forming a negative-feedback loop that prevents overproduction of thyroid hormone Hypothyroidism Hyperthyroidism - too little thyroid hormone - too much thyroid hormone - cause weight gain, lethargy, intolerance to cold - cause weight loss, profuse sweating, high bp & body temperature, irritability - Grave’s Disease: autoimmune disorder that causes sustained thyroid production E. Growth hormone (GH): Tropic effects Non-tropic effects - induce the secretion of another hormone by its target - causes some effect other than the secretion of another cells hormone - liver is major target for GH and responds by releasing insulin-like growth factors (IGFs) - IGFs circulate in the blood and directly stimulate bone and cartilage growth - GH also affects metabolism to raise blood glucose levels - hypersecretion during childhood  gigantism; during adulthood  acromegaly - hyposecretion during childhood delays long bone growth  pituitary dwarfism Reproduction I & II (Male & Female) A. Asexual and sexual reproduction:  - sexual reproduction: creation of offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote  “twofold cost,” however results in genetic variation - asexual reproduction: creation of offspring without the fusion of egg and sperm  binary fission: separation of a parent into two or more individuals of about the same size (ex. sea anemone)  fragmentation: parent’s body breaks into pieces; each piece can develop into a new animal; parent’s body parts regenerates (ex. sea stars)  parthenogenesis: a haploid or diploid egg cell develops into an embryo without fertilization (ex. insects like male honeybees, rare in vertebrates like hammerhead sharks)  budding: part of body grows outward, separates and develops into new individual (ex. hydra) B. Male reproductive organs: External reproductive organs Internal reproductive organs - scrotum (containing testes, epididymis, vas deferens) - gonads (testes) which produces sperm and hormones - penis - accessory glands (seminal vesicles, prostate and bulbourethral glands) Testes (male gonads)

Ducts

Accessory glands

- consist of highly coiled tubules surrounded by connective tissue - sperm form in seminiferous tubules - Leydig cells produce hormones and are scattered between tubules - production of sperm cannot occur at normal body temperatures, therefore the testes of many mammals are held outside the abdominal cavity in the scrotum, where the temperature is lower than in the abdominal cavity (~35C) - from the seminiferous tubules of a testis, sperm pass into the coiled tubules of the epididymis where they become mature and motile - during ejaculation, sperm are propelled through: the muscular vas deferens via accessory glands  ejaculatory duct  urethra  penis - as sperm move toward ejaculation, semen is produced  - composed of sperm plus secretions from three sets of accessory glands (the two seminal vesicles contribute about 60% of the total volume of semen) - contains mucus, fructose, coagulation enzyme, ascorbic acid and prostaglandins (oviduct motility and gamete transport in female), all of which promote the

survival/success of sperm  - the prostate gland secretes its products directly into the urethra through several small ducts  - the bulbourethral glands secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra Penis - composed of three cylinders of spongy erectile tissue - during arousal, erectile tissues fill with blood from arteries causing erection C. Female reproductive organs: External reproductive organs Internal reproductive organs - clitoris: erectile tissue supporting glans covered by - gonads (ovaries) produce eggs and reproductive hood of skin hormones - vulva: skin folds and tissues that surround clitoris  - ducts & chambers: receive and carry gametes; and vaginal opening also contain embryo and fetus if pregnancy

Ovaries

Oviduct (Fallopian tube)

Uterus

Vagina

Vulva

- females have 2 ovaries on either side of the uterus - held in place by ligaments - outer layer packed with follicles - each follicle consists of oocyte (partially developed) surrounded by support cells - extends from uterus toward ovary - each oviduct (fallopian tube) opens in funnel shape at each ovary - each tube has cilia on epithelial lining - cilia + wave-like contractions by oviduct carry egg to uterus - the womb; will help carry fetus during pregnancy  - it is thick muscular organ; expands during pregnancy  - inner lining of uterus is endometrium; has many blood vessels  - neck of uterus (cervix) opens into vagina - site for penis insertion & sperm deposition during copulation - it is muscular but elastic chamber - also serves as birth canal that opens to outside at vulva - collective term for external female genetalia - labia majora: pair of thick fatty ridges enclosing/protecting rest of vulva  - labia minora: pair of slender skin folds enclosing cavity with vaginal opening and urethra  - hymen: thin tissue that partly covers vaginal opening at birth; ruptures at some point  - clitoris, vagina, and labia minora engorge with blood and enlarge during sexual arousal

D. Gametogenesis: - the production of gametes, differs in male and female, reflecting the distinct structure and function of their gametes E. Spermatogenesis and Oogenesis: - spermatogenesis: the development of sperm (continuous and prolific) - oogenesis: the development of mature eggs Spermatogenesis Oogenesis 1. all 4 cells produced my meiosis become mature 1. results in 1 mature egg; cytokinesis uneven  gametes production of 2 polar bodies 2. occurs throughout adolescence and adulthood 2. mitosis completed before birth; gamete production stops around 50 years of age

3. produces mature sperm made from precursor cells in continuous sequence

3. long interruptions

F. Hormonal control of male reproductive system: (1) hypothalamus secretes GnRH and FSH and LH are released by the anterior pituitary in response (2) FSH and LH direct spermatogenesis by acting on different types of cells in the testis (3) FSH stimulates Sertoli cells, located within the seminiferous tubules, to nourish developing sperm (4) LH causes Leydig cells, scattered in connective tissue between the tubules, to produce testosterone and other androgens - two negative-feedback mechanisms control sex hormone production in males (1) testosterone regulates blood levels of GnRH, FSH, and LH through inhibitory effects on the hypothalamus and anterior pituitary (2) inhibin, a hormone that in males is produced by Sertoli cells, acts on the anterior pituitary gland to reduce FSH secretion G. Hormonal control of female reproductive cycles: - the cyclic changes in the uterus (menstrual cycle) are controlled by the ovarian cycle - the ovarian cycle: (1) release of GnRH from the hypothalamus (2) stimulates anterior pituitary to secrete small amounts of FSH and LH (3) follicle stimulating hormone stimulates follicle growth, aided by LH (4) the cells of the growing follicles start to make estradiol; there is a slow rise in estradiol concentration during most of the follicular phase (follicles grow and oocytes mature); the low levels of estradiol inhibit secretion of the pituitary hormones, keeping the levels of FSH and LH relatively low (5) estradiol secretion by the growing follicle begins to rise steeply

(6) FSH and LH levels increase markedly (high concentration of estradiol stimulates gonadotropin secretion in turn increasing the output of GnRH, FSH, and LH (7) the matu...