Osmoregulation & Excretion Chapter 44, pp. 931-939 From Leonardo da Vinci’s notebooks

An organism’s excretory system helps regulate the chemical composition of the body’s principal fluid (blood, coelomic fluid, or hemolymph) The excretory system selectively removes excess water and wastes from the principal fluid

Breakdown of proteins and nucleic acids produces ammonia (a toxin) Excretory systems Breakdown of proteins and nucleic acids produces ammonia (a toxin) Many aquatic organisms excrete ammonia, since it can be effectively diluted with water Fig. 44.8 Ammonia NH3

Breakdown of proteins and nucleic acids produces ammonia (a toxin) Excretory systems Breakdown of proteins and nucleic acids produces ammonia (a toxin) Mammalian livers convert ammonia into urea, which is much less toxic, and requires less water to excrete Fig. 44.8 Ammonia NH3

Breakdown of proteins and nucleic acids produces ammonia (a toxin) Excretory systems Breakdown of proteins and nucleic acids produces ammonia (a toxin) Birds, reptiles, and some other organisms convert ammonia into uric acid, which is relatively nontoxic, and can be excreted as a semisolid without much water loss Fig. 44.8 Ammonia NH3

Vertebrate Excretory Systems Fig. 44.9 Key functions: Filtration Reabsorption Secretion Excretion

Vertebrate Excretory Systems Blood enters the kidneys via the renal arteries and leaves via the renal veins Urine (excess water and wastes removed from the blood) is produced by the kidneys and is conveyed to the urinary bladder via the ureters Urine exits the body via the urethra Fig. 44.13

Fig. 44.13 Vertebrate Excretory Systems Each kidney is divided into a cortex, medulla, and pelvis Each kidney processes about 1000 L of blood per day! Fig. 44.13

Fig. 44.13 Vertebrate Excretory Systems Nephrons = the functional units of the kidneys Packed into the renal cortex and medulla Fig. 44.13

Fig. 44.13 Vertebrate Excretory Systems Each kidney has ~ 1 million nephrons Fig. 44.13

Fig. 44.13 Vertebrate Excretory Systems A nephron consists of: a ball of capillaries known as a glomerulus Fig. 44.13

Vertebrate Excretory Systems A nephron consists of: an afferent arteriole that leads into the glomerulus, and an efferent arteriole that leads out of the glomerulus Fig. 44.13

Vertebrate Excretory Systems A nephron consists of: Bowman’s capsule, that surrounds the glomerulus and extends into the proximal tubule, loop of Henle, and distal tubule Fig. 44.13

Vertebrate Excretory Systems A nephron consists of: capillaries that surround the tubules and loop of Henle, and that feed into venules returning to the renal vein Fig. 44.13

Vertebrate Excretory Systems Filtration occurs in Bowman’s capsules: cells and large molecules remain in the blood, while blood pressure forces water and small molecules from the blood into Bowman’s capsules Fig. 44.13

Vertebrate Excretory Systems Filtration occurs in Bowman’s capsules: cells and large molecules remain in the blood, while blood pressure forces water and small molecules from the blood into Bowman’s capsules

Vertebrate Excretory Systems Selective reabsorption returns important nutrients (glucose, etc.) to the blood, and occurs especially in proximal and distal tubules Fig. 44.13

Vertebrate Excretory Systems Selective reabsorption returns important nutrients (glucose, etc.) to the blood, and occurs especially in proximal and distal tubules Red arrows = active transport Blue arrows = passive transport Notice that nutrients are selectively reabsorbed from the proximal tubule. Fig. 44.14

Vertebrate Excretory Systems Selective secretion adds additional waste molecules to the filtrate, especially in the tubules Red arrows = active transport Blue arrows = passive transport Notice that ammonia (NH3) is selectively secreted into the proximal tubule. Fig. 44.14

Vertebrate Excretory Systems Reabsorption of water occurs along the tubules, descending loop of Henle, and collecting duct Red arrows = active transport Blue arrows = passive transport Fig. 44.14

Vertebrate Excretory Systems Reabsorption of water occurs along the tubules, descending loop of Henle, and collecting duct Red arrows = active transport Blue arrows = passive transport Fig. 44.15

Vertebrate Excretory Systems The descending loop of Henle is permeable to water, but not very permeable to salt (e.g., NaCl) Red arrows = active transport Blue arrows = passive transport Fig. 44.15

Vertebrate Excretory Systems The ascending loop of Henle is not permeable to water, but it is to NaCl Red arrows = active transport Blue arrows = passive transport Fig. 44.15

Vertebrate Excretory Systems High concentration of NaCl outside the nephron deep in the kidneys helps concentrate urine in the collecting duct Red arrows = active transport Blue arrows = passive transport Some urea escapes from the collecting duct, but most passes out in the urine. Fig. 44.15

Mammalian excretory systems are adapted to diverse environments

Mammalian excretory systems are adapted to diverse environments Mammals that live in environments with plenty of water have short loops of Henle that cannot produce concentrated urine

Mammalian excretory systems are adapted to diverse environments Mammals that live in very dry environments have very long loops of Henle that can produce highly concentrated urine

Hormones and the Endocrine System Chapter 45

The endocrine system = postal system for the body Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change.

The endocrine system = postal system for the body Hormones are the chemical messages that: Regulate aspects of behavior Regulate growth, development, & differentiation Maintain internal homeostatic conditions 4 classes of animal hormones: Peptide hormones – amino acid chains Single amino acid derivatives Steroid hormones – cholesterol based Prostaglandins – fatty-acid based Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change.

The endocrine system = postal system for the body Hormones are the chemical messages that: Maintain internal homeostatic conditions Regulate growth, development, & differentiation Regulate aspects of behavior 4 classes of animal hormones: Single amino acid derivatives Peptide hormones – amino acid chains Steroid hormones – cholesterol based Prostaglandins – fatty-acid based Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change.

The endocrine system = postal system for the body Hormones are the chemical messages that: Maintain internal homeostatic conditions Regulate growth, development, & differentiation [often irreversible] Regulate aspects of behavior 4 classes of animal hormones: Single amino acid derivatives Peptide hormones – amino acid chains Steroid hormones – cholesterol based Prostaglandins – fatty-acid based Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change.

The endocrine system = postal system for the body Hormones are the chemical messages that: Maintain internal homeostatic conditions Regulate growth, development, & differentiation [often irreversible] Regulate aspects of behavior [generally reversible] Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change.

The endocrine system = postal system for the body Hormone-secreting organs are called endocrine glands, because they secrete their chemical messengers directly into body fluids Hormones are produced by specialized cells that have been activated by a stimulus. Hormones travel through the blood to target cells, where they either promote a prolonged and irreversible change, or a transient and reversible change. In contrast, exocrine glands secrete their products into ducts Glands that secrete sweat, mucus, digestive enzymes, and milk are exocrine glands

Since hormones circulate to ALL cells, how do they act at only specific sites? Receptors Only cells with correct receptors (target cells) respond to hormones

The target cell response is idiosyncratic (i. e The target cell response is idiosyncratic (i.e., it depends on the type of cell) Fig. 45.4

Hormones exhibit a diversity of structure and function Peptides, proteins, glycoproteins, amines, Table 45.1

Hormones exhibit a diversity of structure and function Peptides, proteins, glycoproteins, amines, steroids Table 45.1

Since hormones circulate to ALL cells, how do they act at only specific sites? Receptors Only cells with correct receptors (target cells) respond to hormones Surface receptors Intracellular receptors

Surface Receptors Most amino acid-based hormones are water soluble and target surface receptors A signal-transduction pathway is a series of molecular changes that converts an extracellular chemical signal to a specific intracellular response Fig. 45.3

Intracellular Receptors Most steroid hormones are lipid soluble and target intracellular receptors An intracellular receptor usually performs the entire task of transducing the signal within the cell In almost all cases, this is a transcription factor, and the response is a change in gene expression Fig. 45.3

Major endocrine organs and glands Fig. 45.6

Hypothalamus-Pituitary Complex The hypothalamus receives nervous input from throughout the body The hypothalamus contains two sets of neurosecretory cells whose hormonal secretions are stored in or regulate the pituitary gland The posterior pituitary stores and secretes two hormones made by the hypothalamus The anterior pituitary consists of endocrine cells that synthesize and secrete at least 6 different hormones

Hypothalamus-Pituitary Complex The hypothalamus-posterior pituitary provides an example of a simple neurohormone pathway Pathway Example Stimulus Suckling Sensory neuron Hypothalamus/ posterior pituitary Neurosecretory cell Oxytocin Blood vessel Target effectors Smooth muscle in breast Response Milk release Fig. 45.2b

Hypothalamus-Pituitary Complex The hypothalamus-anterior pituitary provides an example of a simple neuroendocrine pathway Pathway Example Stimulus Hypothalamic neurohormone released in response to neural and hormonal signals Sensory neuron Hypothalamus Neurosecretory cell Prolactin- releasing hormone Blood capillary Prolactin Endocrine cell of pituitary Blood vessel Target effectors Mammary glands Milk production Response Fig. 45.2c

Major endocrine organs and glands Fig. 45.6

Pancreas Exocrine function Endocrine function Digestive secretions released into pancreatic duct to small intestines Endocrine function Islet cells Insulin Glucagon

Pancreas Exocrine function Endocrine function Digestive secretions released into pancreatic duct to small intestines Endocrine function Islet cells Insulin Glucagon

Pancreas Exocrine function Endocrine function Digestive secretions released into pancreatic duct to small intestines Endocrine function Islets of Langerhans – endocrine cells Insulin Glucagon antagonistic hormones

Pancreas regulates blood glucose Insulin – decrease blood glucose stimulates uptake by cells – use it or store it as fat and glycogen Glucagon increase blood glucose stimulates release by cells – breakdown fat and glycogen Diabetes mellitis defects in production, release or response to insulin

Pancreas regulates blood glucose Insulin – decreases blood glucose Stimulates uptake by cells – cells use it or store it as fat and glycogen Glucagon – increase blood glucose stimulates release by cells – breakdown fat and glycogen Diabetes mellitis defects in production, release or response to insulin

Pancreas regulates blood glucose Insulin – decreases blood glucose Stimulates uptake by cells – cells use it or store it as fat and glycogen Glucagon – increases blood glucose Stimulates release by cells – breakdown of fat and glycogen Diabetes mellitis defects in production, release or response to insulin

Pancreas regulates blood glucose Pathway Example Pathway An example of a simple endocrine pathway Example Pathway Example Stimulus High blood glucose Stimulus Suckling Stimulus Hypothalamic neurohormone released in response to neural and hormonal signals Receptor protein Pancreas secretes insulin Sensory neuron Sensory neuron Hypothalamus/ posterior pituitary Hypothalamus Endocrine cell Blood vessel Neurosecretory cell Neurosecretory cell Hypothalamus secretes prolactin- releasing hormone ( ) Posterior pituitary secretes oxytocin ( ) Blood vessel Blood vessel Diabetes mellitus (all forms) Results from defects in the production, release or response to insulin Target effectors Liver Anterior pituitary secretes prolactin ( ) Target effectors Smooth muscle in breast Glycogen synthesis, glucose uptake from blood Response Endocrine cell Blood vessel (a) Simple endocrine pathway Response Milk release (b) Simple neurohormone pathway Target effectors Mammary glands Milk production Response Fig. 45.2a (c) Simple neuroendocrine pathway

Hormone-like local regulators appear to be produced by all the body’s cells… These chemical messengers affect target cells adjacent to or near their point of secretion and can act very rapidly; the process is known as paracrine signaling

The same hormones are found across diverse taxa E. g The same hormones are found across diverse taxa E.g., Insulin is found in bacteria, fungi, protists, etc. E.g., Thyroxin is found in many vertebrates; increases metabolism in humans & controls metamorphosis in amphibians

The same hormones are found across diverse taxa E. g The same hormones are found across diverse taxa E.g., Insulin is found in bacteria, fungi, protists, etc. E.g., Thyroxin is found in many vertebrates; increases metabolism in humans & controls metamorphosis in amphibians

The same hormones are found across diverse taxa E. g The same hormones are found across diverse taxa E.g., Insulin is found in bacteria, fungi, protists, etc. E.g., Thyroxin is found in many vertebrates; increases metabolism in humans & controls metamorphosis in amphibians