CAMPBELL BIOLOGY IN FOCUS URRY CAIN WASSERMAN MINORSKY
CAMPBELL BIOLOGY IN FOCUS URRY CAIN WASSERMAN MINORSKY REECE 32 The Internal Environment of Animals: Tissues, Endocrine and Renal Systems Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge, Simon Fraser University 2016 Pearson Education, Inc. SECOND EDITION ORGANIZATION OF ANIMAL BODIES Anatomy: the study of the biological form of an organism Physiology: the study of the biological functions an organism performs
Form fits function Cell: lowest level that can live as an organism Tissues: groups of cells with common structure and function Cells may be held together by: Sticky coating of collagen and elastin Desmosomes Tight junctions 4 main categories of tissues: Epithelial Connective Muscle Nervous Figure 32.2 Tissue Types Lumen
10 mm Apical surface Nervous tissue Basal surface Epithelial tissue (Confocal LM) Epithelial tissue Axons of neurons Blood
vessel Glia 20 mm Blood Skeletal muscle tissue Nuclei Red blood cells Collagenous fiber Muscle cell Elastic fiber 100 mm
100 mm 2016 Pearson Education, Inc. Plasma White blood cells 50 mm Loose connective tissue EPITHELIAL TISSUE Epithelium: forms interactive surfaces with environment on external and internal body surfaces; functions as barriers Formed from continuous sheets of tightly packed cells Covers outside of body; or lines body cavities and
organs Avascular; no blood vessels; the blood vessels that supply nutrients and remove waste are in adjacent connective tissue (diffusion) Apical surface Basal surface Figure 32.2-1 Lumen 10 mm Apical surface Epithelial tissue Basal surface
Epithelial tissue 2016 Pearson Education, Inc. CELL SHAPES AND ARRANGEMENT OF LAYERS OF EPITHELIUM Squamous epithelium: flat; look like floor tiles Their thinness allows rapid movement of substances through them by diffusion Cuboidal epithelium: boxlike; look like dice Produces important secretions Columnar epithelium: tall, pillarlike; some have cilia Protects underlying tissue Functions in absorption of nutrients and secretions (digestive juices) Simple epithelium: 1 layer of cells Stratified epithelium: 2 or more layers Pseudostratified epitheium: 1 layer of a mixture of cell shapes; looks like multiple layers, but it isnt. Not all cells reach the cell surface; the
ones that do are either ciliated or secrete mucus. EXAMPLES OF EPITHELIUM Simple Squamous Epithelium: alveoli; lines blood vessels; surface layer of many membranes EXAMPLES OF EPITHELIUM (CONTD) Simple Cuboidal Epithelium: kidney tubules; major glands; lines tubules.sweat ducts; thyroid and salivary glands EXAMPLES OF EPITHELIUM (CONTD) Simple Columnar Epithelium: Non-ciliated: lines inner portion of GIT; mucusproducing goblet cells found here Ciliated: Fallopian tubules (oviducts) EXAMPLES OF EPITHELIUM (CONTD) Stratified Squamous Epithelium: protects underlying
tissues where there is abrasion/wear and tear; I.e. outermost layer of skin, lines mouth, esophagus, vagina, anus EXAMPLES OF EPITHELIUM (CONTD) Pseudostratified Columnar Epithelium: forms mucus membranes that line nasal passages; ciliated (oviducts) or mucus-producing respiratory tract) CONNECTIVE TISSUE Connective tissue: connects and supports other tissues 6 major types:Characterized by few cells suspended in extracellular matrix (background materials of fibers Matrix may be liquid, gel, or ground solid Loose Connective Tissue Attaches epithelia to underlying tissues Holds organs in place.like packing material Consists of a loose weave of 2 kinds of cells and 3 types of
protein fibers Fibroblasts: secrete the proteins (collagen and elastin) of the fibers Macrophages: perform phagocytosis for immune system NOTE: -blast is a cell that is making something -clast is a cell breaking down something -cyte is a mature cell Collaginous fibers: great tensile strength; no stretching Elastic fibers: stretchy Reticular fibers: strength LOOSE CONNECTIVE TISSUE NOTE: collagen is the protein for structure and strength; elastin is the protein for stretch/elasticity ADIPOSE TISSUE Adipose tissue: loose connective tissue specialized to
store fat in adipose cells; insulates body; long-term fuel molecule (fat) Each adipose cell called an adipocyte; has 1 large fat droplet Varies in size as fats are stored or utilized for energy FIBROUS CONNECTIVE TISSUE Fibrous CT: dense bundles of large numbers of collaginous fibers (strength/structure) imparts non-elastic strength Found in tendons.attach muscle to bone I.e. Achilles tendon Found in ligaments..attach bone to bone at joints; I.e. ACL Nucleus of fibroblast Collagen fiber
BLOOD (VASCULAR TISSUE) Blood: connective tissue made of plasma (liquid matrix of water, salts, and proteins) and plasma proteins The liquid matrix allows rapid transport of blood cells, nutrients, and wastes through body Cellular components: Leukocytes: WBC.immune function Erythrocytes: RBC..oxygen transport Platelets: cell fragments..blood clotting Blood cells are made in red bone marrow near ends of long bones Figure 32.2-5 Blood Plasma 50 mm
White blood cells Red blood cells 2016 Pearson Education, Inc. CARTILAGE Cartilage: connective tissue that is both strong and flexible Composed of collaginous fibers embedded in a rubbery matrix called chondroitin sulfate (a rubbery proteincarbohydrate ground substance) Avascular and without nerves Chondrocytes: cartilage cells; secrete both collagen and condroitin sulfate; confined to lacuna (scattered spaces in the condroitin sulfate) Comprises skeleton of all vertebrate embryos.retained
in some vertebrates (sharks) as cartilaginous adult skeleton Most vertebrates replace if (ossify) with bone Cartilage still retained in vertebrate adults as nose, ears, trachea, epiglottis, ribs, intervertebral discs, ends of long bones CARTILAGE (CONTINUED) Lacuna Chondroitin sulfate BONES Bones: mineralized connective tissue Osteoblasts: bone-forming cells Deposit a matrix of collagen and calcium phosphate:
hardens into the mineral hydroyapatite; makes bones hard, not brittle Bone consists of repeatiing units called Osteons or Haversian Systems Concentric layers (lamella) of hydroxyapatite matrix around a central canal of blood vessels and nerves Between the layers (lamella) are spaces (lacuna) which contain osteocytes In long bones, only the outer are is hard/compact Inner area is filled with spongy bone tissue called marrow Red bone marrow is where blood cells are made BONES (CONTINUED) Osteons Osteocyte
Within lacuna Lamella Canaliculi, channels connecting lacuna and osteocytes MUSCLE TISSUE Muscle tissue: contracts to move body Made up of parallel bundles of long microfilaments These have contractile proteins called actin and myosin 3 types of vertebrate muscle tissue Skeletal (striated) muscle Cardiac muscle Smooth (visceral) muscle Skeletal (striated) muscle:
For voluntary movement Long, cylindrical cells that are stria Multinucleated Attached to bones by tendons Figure 32.2-3 Skeletal muscle tissue Nuclei Muscle cell
100 mm 2016 Pearson Education, Inc. MUSCLE TISSUE (CONTINUED) Cardiac Muscle: contractile wall of heart Uninucleated Striated and branched Intercalated discs: ends of cells which relay contractile impulses Intercalated discs NERVOUS TISSUE Nervous tissue: transmits nerve impulses as action potentials throughout the body Neuron: nerve cell Has a cell body
Dendrites: extensions toward cell body (receives stimuli) Axons: extensions away from cell body (send stimuli on) Figure 32.2-2 Nervous tissue (Confocal LM) Axons of neurons Blood vessel Glia 2016 Pearson Education, Inc.
20 mm 2 COMMUNICATION SYSTEMS IN ANIMALS 2 Communication systems in animals: Endocrine System: acts slowly and over prolonged periods to affect broad changes in physiological and behavioral states of animal Uses hormoneschemical compounds that are secreted and transported by the circulatory system, often to distant targets Hormones bind to specific receptors on the surface or inside target cells that receive their signals Helps an animal respond to its environment Is involved in growth and development Nervous System: responds rapidly to sensory information, providing immediate physiological responses Both systems help maintain homeostasis.steady state
Figure 32.4a (a) Signaling by hormones STIMULUS Endocrine cell Hormone Signal travels everywhere. Blood vessel Response 2016 Pearson Education, Inc. Figure 32.4b
(b) Signaling by neurons STIMULUS Cell body of neuron Nerve impulse Axon Signal travels to a specific location. Nerve impulse Axons
mechanisms: Body temperature Weight Calcium and potassium ions Blood glucose Glucose and Negative Feedback Positive Feedback Positive feedback: continues response until completion Childbirth Arteriosclerosis and high BP
Cell Surface Receptors Peptide and amine hormones: Hydrophilic Bind to cell surface receptors Activate 2nd messenger pathways which change the state of the target cell Intracellular Receptors Steroid hormones: Hydrophobic Bind to intracellular or
nuclear receptors Act as transcription factors to alter the gene expression of the cell Amplifying a Hormonal Signal Hormones communicate by signaling cascades Amplify the strength of their downstream effect on target cells Hypothalamus & Pituitary Gland Hypothalamus: Boss Signals to pituitary glands
Which acts as a control center for most other endocrine glands POSTERIOR PITUITARY HORMONES Hypothalamus makes hormones released by posterior pituitary: 2 hormones Oxytocin: stimulates contraction of uterus/childbirth and releases milk from mammary glands ADH (Antidiuretic Hormone or Vasopressin): enhances water reabsorption by kidneys and sweat glands ANTERIOR PITUITARY HORMONES Anterior Pituitary Gland: controlled by the hypothalamus
Tropic Hormones: when anterior pituitary acts on other endocrine glands to cause release of other hormones TSH: acts on thyroid gland Gonadotropic hormones FSH and LH, which act on male & female gonads (ovaries and testes) ACTH: acts on the adrenal glands Growth Hormone (GH): stimulates growth of bones, muscles, other body tissues Tropic Hormone - TSH TSH (Thyroid Stimulating Hormone) Acts on thyroid gland Thyroid releases thyroxine (T4) and triiodothyorine (T3) Help regulate cellular metabolism throughout body Needs iodine (I)..iodized salt, kelp, seaweed Deficiencygoiter.causes thyroid enlargement Hyperthyroidism: overly active metabolism.weight loss, increased apetite
Hypothyroidism: slow metabolic rateI.e. fatigue Tropic Hormones FSH and LH Follicle Stimulating Hormone (FSH) Stimulates production of ova by ovaries in females And sperm production by testes in males Leutenizing Hormone (LH) Causes ovulation by ovaries, and changes follicle into corpus luteum Stimulates secretion of sex hormones: estrogen from ovaries & progesterone from corpus luteum And stimulates testes to secrete testosterone from testes Tropic Hormone ACTH Adrenocorticotropic
Hormone (ACTH) Acts on adrenal cortex to secrete long-term stress hormones, I.e. cortisol, aldosterone CALCIUM HOMEOSTASIS BY THYROID & PARATHYROID GLANDS Thyroid Gland: Releases calcitonin Good for you If calcium blood levels too high, the release of calcitonin lowers blood calcium 3 ways: Calcium deposition into bones Reduces calcium reabsorption in intestines and kidneys
Parathyroid Glands: Releases parathyroid hormone (PTH) .bad for you If blood calcium levels fall too low, PTH takes calcium out of bones (from osteoclast activity) Opposite of calcitonin ADRENAL GLANDS Adrenal Medulla (inner): short-term stress Releases epinephrine (adrenaline) and norepinephrine (noradrenaline) These are catecholamines that regulate fight or flight response Raises blood glucose, increases metabolic activities, constricts certain blood vessels, increases heart rate, increases BP
Target organs: heart, blood vessels, liver Adrenal Cortex (outer): long term stress hormones Releases glucocorticoids.cortisol and hydrocortisone These steroids raise your blood glucose Make you retain fat Decrease immune function Releases aldosterone Promotes reabsorption of sodium and water by kidneys GLUCOSE HOMEOSTASIS BY PANCREAS Pancreas: responsible for blood glucose homeostasis Releases insulin to lower blood glucose Signals liver to convert
glucose into storage glycogen; stored in liver and muscles Releases glucagon to raise blood glucose Signals liver and muscles to release glycogen and then liver breaks it down to glucose Type I Diabetes Mellitus: autoimmune disorder with elevated blood glucose Type II: Not an autoimmune disorder Pineal Gland Pineal Gland: located in thalamic region of
brain Responds to signals from ANS Secretes melatonin ..hormone of wakefulness and sleep, biological rhythms, and mood When melatonin levels rise..animals sleep Regulating and Conforming An animal that is a regulator uses internal mechanisms to control internal change despite external fluctuation An animal that is a conformer allows its internal condition to change in accordance with external
changes An animal may regulate some internal conditions and not others For example, a fish may conform to surrounding temperature in the water, but it regulates solute concentrations in its blood and interstitial fluid (the fluid surrounding body cells) 2016 Pearson Education, Inc. Figure 32.11 40 Body temperature (C) River otter (temperature regulator) 30 20
Largemouth bass (temperature conformer) 10 0 0 10 20 30 40 Ambient (environmental) temperature (C) 2016 Pearson Education, Inc.
Homeostasis Organisms use homeostasis to maintain a steady state or internal balance regardless of external environment In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level 2016 Pearson Education, Inc. Figure 32.12 Thermostat turns heater off. Room temperature Room temperature increases. decreases.
ROOM TEMPERATURE AT 20C (set point) Room temperature increases. 2016 Pearson Education, Inc. Thermostat turns heater on. Room temperature decreases. Endothermy and Ectothermy
Thermoregulation is the process by which animals maintain an internal temperature within a normal range Endothermic animals generate heat by metabolism; birds and mammals are endotherms; maintain stable body temp in fluctuations of external temps Ectothermic animals gain heat from external sources; may use behavioral methods; consume less food; e.g. most invertebrates, fishes, amphibians, and nonavian reptiles 2016 Pearson Education, Inc. Figure 32.13 (a) A walrus, an endotherm (b) A lizard, an ectotherm 2016 Pearson Education, Inc.
Balancing Heat Loss and Gain Organisms exchange heat by 4 physical processes Radiation Evaporation Convection Conduction Heat is always transferred from an object of higher temperature to one of lower temperature 2016 Pearson Education, Inc.
Figure 32.14 2016 Pearson Education, Inc. Radiation Evaporation Convection Conduction Circulatory Adaptations for Thermoregulation In response to changes in environmental temperature, animals can alter blood (hence heat) flow between their body core and surface Vasodilation, the widening of the diameter of superficial blood vessels, promotes heat loss
Vasoconstriction, the narrowing of the diameter of superficial blood vessels, reduces heat loss 2016 Pearson Education, Inc. Figure 32.15 The arrangement of blood vessels in many marine mammals and birds allows for countercurrent exchange Countercurrent heat exchangers transfer heat between fluids
flowing in opposite directions and Key reduce heat loss Warm blood Cool blood Blood flow Heat transfer 2016 Pearson Education, Inc. Canada goose Artery Vein 35C 33
Thermostat in hypothalamus activates cooling mechanisms. Response: Sweat Body temperature increases. Body temperature decreases. NORMAL BODY TEMPERATURE (approximately 3638C)
Body temperature increases. Body temperature decreases. Response: Shivering Response: Blood vessels in skin constrict. 2016 Pearson Education, Inc. Thermostat in hypothalamus activates warming mechanisms.
PLASMA MEMBRANES All animals regulate their water and electrolyte levels within their cells. All animals must balance their water intake/output as well as solutes (also called ions or electrolytes) for homeostasis Cell membranes and sheets of cells are selectively permeable membranes Allow the passage of water, but restrict or control the movement of many solutes Cell membranes are lipid bilayers with embedded proteins Plasma Membranes Contd Cross the membrane easily: Nonpolar/hydrophobic molecules..such as HC and O2 Small polar molecules.such as H2O and CO2 Cross by diffusion.the spontaneous, net movement of a substance DOWN its concentration gradient (from
higher concentration to lower concentration) 2016 Pearson Education, Inc. Osmosis Special type of diffusion: the diffusion of water through a semipermeable membrane Spontaneous and passive; water moves from an area of [greater H2O] (or low solute concentration) to its area of [lower H 2O] (or higher solute concentration) Expressed as osmolarity: moles of solute/liter of H2O; Higher osmolarity: more solutes (more concentrated) I.e. osmolarity of human blood is 300 mosms/L while seawater is 1,000 mosm/L Osmotic pressure: pressure by water as it moves from one solution to another Osmoregulation: regulation of water and solute levels to control osmotic pressure inside cells or organisms; a type of homeostasis;
humans balance the gain and loss of water and solutes (ions, electrolytes), because blood cant be too thick Osmosis Hypo Hyper Figure 32.17-1 Osmoregulation in a Marine Fish Gain of water and salt ions from food Excretion of salt ions
Osmotic water loss from gills through gills and other parts of body surface Water SALT WATER Gain of water and salt ions from drinking seawater 2016 Pearson Education, Inc. Excretion of salt ions and small amounts of water in scanty urine from kidneys
Salt Figure 32.17-2 Osmoregulation in a Freshwater Fish Gain of water and some ions in food Uptake of salt ions by gills Osmotic water gain through gills and other parts of body surface Water
Salt FRESH WATER 2016 Pearson Education, Inc. Excretion of salt ions and large amounts of water in dilute urine from kidneys Osmoregulators Marine and freshwater organisms have opposite challenges Marine fish drink large amounts of seawater to balance water loss and excrete salt through their gills and kidneys
Freshwater fish drink almost no water and replenish salts through eating; some also replenish salts by uptake across the gills 2016 Pearson Education, Inc. Salmon Life Cycle Osmoconformers Match internal osmotic pressure to that of their external environment Reduces the movement of water and solutes into or out of their bodies Dont spend a lot of energy regulating osmotic pressure However, they do need to adapt their [solute] to seawater Examples: Most marine invertebrates (match intracellular [solute] to seawater)
Some marine vertebrates, such as lampreys and hagfish (match intracellular [solute] to seawater) Sharks, rays, skates (match intracellular [urea] to seawater) Salt Excretion Sharks and rays: excrete excess salt by a rectal gland Marine birds have specialized nasal salt glands, allowing them to gain net water by drinking seawater Nitrogenous Waste Excretory organs eliminate nitrogenous wastes and
regulate water and electrolyte levels. Excretion: the elimination of waste products and toxic compounds from body Animals have excess nitrogenous wastes from N-containing foods they metabolize for energy; specifically proteins and nucleic acids Depending on the animal, these wastes are either excreted as: Ammonia Urea Uric acid Figure 32.18 Nucleic acids Proteins Breakdown of nitrogencontaining macromolecules
Amino acids Removal of nitrogencontaining amino group Nitrogenous bases NH2 (amino groups) Nitrogenous Wastes Conversion to nitrogenous waste NH3 Ammonia Most aquatic animals, including most bony
fishes 2016 Pearson Education, Inc. Urea Uric acid Birds and many other Mammals, most amphibians, sharks, reptiles, insects, land snails some bony fishes Nitrogenous Waste Ammonia Excreted by most aquatic animals, including bony fishes
Most toxic, but easily released in water Liver deaminates Kidney excretes Urea Excreted by mammals, amphibians, sharks, Much less toxic than ammonia Produced in liver by combining ammonia with carbon dioxide; then excreted by kidneys
Nitrogenous Wastes Contd Uric Acid Excreted by birds, insects, reptiles Least toxic but most energetically costly Insoluble in water; excreted as semi-solid paste called guano; allows animal to conserve water Humans excrete urea, but also a little bit of uric acid. Gout: excess uric acid in joints 2016 Pearson Education, Inc. Figure 32.21-1 Excretory Organs Posterior vena cava Renal artery
and vein Aorta Ureter Urinary bladder Urethra 2016 Pearson Education, Inc. Kidney ANIMAL EXCRETORY ORGANS All animal excretory organs work by: Filtration Reabsorption Secretion Elimination; urine produced by kidneys/other excretory organs is stored in bladder or cloaca until being
eliminated Examples of excretory organs: Protonephridia in flatworms Metanephridia of segmented annelid worms Malpighian tubules of insects Kidneys of vertebrates Filtration, Reabsorption, Secretion & Excretion Most excretory systems start by pressure-filtering blood; then getting a filtrate (early urine) Reabsorption: returning valuable solutes to blood Secretion: removes toxins Excretion: discharging unwanted solutes as urine
Kidney Location in Vertebrates Kidneys: control all aspects of blood Composition; Volume, & Pressure of blood 2 kidneys Built of compact excretory tubules (nephrons) surrounded by a dense network of capillaries Urine formed in outer renal cortex and inner renal medulla of kidneys Drains to renal pelvis 2 ureters
Mammalian Kidney and Nephron Vertebrate Kidney and Nephron Nephrons: working unit of kidneys (excretory tubules) Each kidney has about 1 million nephrons 80% are cortical (short, in outer renal cortex) 20% are juxtamedullary nephrons with a Loop of Henle extending down into inner renal medulla These long nephrons are responsible for producing urine that is hyperosmotic (more concentrated) to blood
Several nephrons empty into each collecting duct, which drains into renal pelvis JUXTAMEDULLARY NEPHRONS Figure 32.21-2c Nephron Organization Afferent arteriole from renal artery Glomerulus Bowmans capsule Proximal tubule Distal tubule
Peritubular capillaries Efferent arteriole from glomerulus Branch of renal vein Collecting duct 2016 Pearson Education, Inc. Vasa recta
Descending limb Loop of Henle Ascending limb Mammalian Kidney and Nephron The mammalian kidney can produce urine that is more concentrated than blood, as an adaptation for living on land. Each juxtamedullary nephron consists of 5 parts: Bowmans Capsule (surrounds glomerulus, a ball of capillaries found inside) Proximal convoluted tubules
Loop of Henle (descending then ascending limbs) Distal convoluted tubule Collecting duct Bowmans capsule The parts of the nephron have different functions To renal pelvis PATH OF BLOOD
Left ventricle (O2 blood) Aorta (O2) Renal artery (O2) Afferent arteriole (O2) Glomerulus (O2; ball of capillaries in Bowmans Capsule) Efferent arteriole (O2) Peritubular capillaries (O2; surround proximal/distal tubules) Vasa recta (surrounds Loop of Henle, half O2 then CO2) Renal vein (CO2) Inferior vena cavae (CO2)
Path of Blood and Vasa Recta Mammalian Glomerulus and Bowmans Capsule Figure 32.22 Bowmans capsule Proximal tubule Distal tubule NaCl H2O K+ Nutrients HCO NaCl
3 100 H + CORTEX Filtrate H2O Salts (NaCl and others) HCO3 H+ Urea Glucose, amino acids
Some drugs Active transport Passive transport 2016 Pearson Education, Inc. Osmolarity of interstitial fluid (mOsm/L) H2O 300 300 300
HCO3 NH3 100 K+ H2O Descending limb of loop of Henle H2O OUTER MEDULLA NaCl 400
1,200 FROM BLOOD TO URINE Bowmans Capsule: catches the BP filtration of the glomerulus Filtrate similar to blood plasma Lose about 20% water here Proximal convoluted tubule: Reabsorption of 75% NaCl, 75% water, aa, glucose Secretion of H+, NH3 into filtrate Descending limb of Loop of Henle: permeable to water, but not salts Reabsorption of water; therefore, tip has very high osmolarity as urine becomes very concentrated Figure 32.22-1
Active transport Passive transport Bowmans capsule Proximal tubule NaCl H2O K+ Nutrients HCO3 Distal tubule NaCl HCO3 H2O 300
H+ 300 H2O From Blood to Urine Contd Ascending limb of Loop of Henle: permeable to salt, but not to water Job #1: make medulla salty so descending limb will reabsorb water Actively pumps out (absorbs) NaCl to make medulla salty Therefore urine becomes more dilute again Countercurrent multiplier system: involves Loop of Henle to maintain a high salt concentration in medulla of kidney; creates a steep osmotic gradient that will result in concentrated urine and reabsorption of water Distal Convoluted Tubule: Reabsorption of NaCl, water, Buffers, Ca+2
Secretion of K+, H+, and mainly urea 2016 Pearson Education, Inc. Figure 32.22-2 Descending limb of loop of Henle 400 NaCl H2O OUTER MEDULLA 200
1,200 Active transport Passive transport H2O Thin segment 700 of ascending limb H2O 900 INNER MEDULLA 400
NaCl 400 NaCl Thick segment of ascending limb H2O 1,200 From Blood to Urine Contd Collecting Duct: back through salty medulla tissue again Permeable to water, but not to salt Therefore reabsorb lots of water Urine gets more hyperosmotic Excrete urine hyperosmotic to body fluids (1,200
mOsm/L) Urine is 4x more hyperosmotic to blood Main components are urea, uric acids, salts, poisons, drugs, other metabolic wastes Should look pale straw colored ADH in collecting duct dictates how porous it will be to reabsorb even more water 2016 Pearson Education, Inc. QUICK CHECK The filtrate is dilute at the start and end of the loop of Henle. What, then, is the function of the loop of Henle? Answer The loop creates a concentration gradient from the cortex to the medulla, which is important for water reabsorption from the descending limb and the
collecting ducts. The loops also leave urea as the main solute. Concentrating Urine in the Mammalian Kidney The mammalian kidneys ability to conserve water is a key terrestrial adaptation The loop of Henle and surrounding capillaries act as a type of countercurrent system This system involves active transport and thus an expenditure of energy Such a system is called a countercurrent multiplier system 2016 Pearson Education, Inc. Figure 32.24-s3 Hypothalamus
Osmoreceptors in hypothalamus trigger release of ADH. Hypothalamus generates thirst. Posterior pituitary Distal tubule ADH Blood osmolarity increases (such as after sweating profusely).
Collecting duct H2O reabsorption NORMAL BLOOD OSMOLARITY (300 mOsm/L) 2016 Pearson Education, Inc. Drinking of water Hormonal Control of Urine Concentration HORMONAL CONTROL OF KIDNEYS Antidiuretic Hormone (ADH or Vasopressin) Stimulus: high blood osmolarity; triggers osmoreceptors in
hypothalamus to have posterior pituitary gland secrete ADH ADH acts on collecting duct to increase its reaborption of water End result: helps fluid retention by making kidneys keep more water Hypothalamus also causes thirst.drinking reduces blood osmolarity NOTE: Beer lowers ADH, cant hold water, lots of dilute urine, get dehydrated NOTE: Diabetes symptom: thirst Why? Diabetes lowers ADH. Hormonal Control of Kidneys Contd Renin-Angiotensin-Aldosterone System (RAAS) Stimulus: low BP or blood volume triggers JGA in kidneys to release renin JGA releases renin, converts angiotensinogen into
angiotensin II, which constricts arterioles and increases reabsorption of water and salt Angiotensin II also stimulates adrenal cortex to release aldosterone: hormone which increases reabsorption of water and salt in distal tubules End result: increase in BP and blood volume 2016 Pearson Education, Inc. Blood Volume & Blood Pressure
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