Homeostasis: Regulation of N and H2O

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Osmoregulation Excretion
Chapter 44, pp. 931-939
From Leonardo da Vincis notebooks
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An organisms excretory system helps regulate
the chemical composition of the bodys principal
fluid (blood, coelomic fluid, or hemolymph)
The excretory system selectively removes excess
water and wastes from the principal fluid
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Excretory systems
Breakdown of proteins and nucleic acids produces
ammonia (a toxin)
Fig. 44.8
Many aquatic organisms excrete ammonia, since it
can be effectively diluted with water
Ammonia NH3
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Excretory systems
Breakdown of proteins and nucleic acids produces
ammonia (a toxin)
Fig. 44.8
Mammalian livers convert ammonia into urea, which
is much less toxic, and requires less water to
excrete
Ammonia NH3
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Excretory systems
Breakdown of proteins and nucleic acids produces
ammonia (a toxin)
Fig. 44.8
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
Ammonia NH3
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Vertebrate Excretory Systems
Fig. 44.9
Key functions
Filtration Reabsorption Secretion Excretion
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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
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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
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Vertebrate Excretory Systems
Nephrons the functional units of the kidneys
Packed into the renal cortex and medulla
Fig. 44.13
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Vertebrate Excretory Systems
Each kidney has 1 million nephrons
Fig. 44.13
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Vertebrate Excretory Systems
A nephron consists of a ball of capillaries
known as a glomerulus
Fig. 44.13
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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
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Vertebrate Excretory Systems
A nephron consists of Bowmans capsule, that
surrounds the glomerulus and extends into the
proximal tubule, loop of Henle, and distal tubule
Fig. 44.13
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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
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Vertebrate Excretory Systems
Filtration occurs in Bowmans capsules cells
and large molecules remain in the blood, while
blood pressure forces water and small molecules
from the blood into Bowmans capsules
Fig. 44.13
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Vertebrate Excretory Systems
Filtration occurs in Bowmans capsules cells
and large molecules remain in the blood, while
blood pressure forces water and small molecules
from the blood into Bowmans capsules
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Vertebrate Excretory Systems
Selective reabsorption returns important
nutrients (glucose, etc.) to the blood, and
occurs especially in proximal and distal tubules
Fig. 44.13
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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
Fig. 44.14
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Vertebrate Excretory Systems
Selective secretion adds additional waste
molecules to the filtrate, especially in the
tubules
Red arrows active transport Blue arrows
passive transport
Fig. 44.14
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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
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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
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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
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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
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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
Fig. 44.15
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Mammalian excretory systems are adapted to
diverse environments
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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
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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
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Hormones and the Endocrine System

• Chapter 45

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The endocrine system postal system for the body
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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

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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

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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

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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

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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
In contrast, exocrine glands secrete their
products into ducts Glands that secrete sweat,
mucus, digestive enzymes, and milk are exocrine
glands
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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

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The target cell response is idiosyncratic (i.e.,
it depends on the type of cell)
Fig. 45.4
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Hormones exhibit a diversity of structure and
function
Peptides,
proteins,
glycoproteins,
amines,
Table45.1
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Hormones exhibit a diversity of structure and
function
Peptides,
proteins,
glycoproteins,
amines,
steroids
Table45.1
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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

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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
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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
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Major endocrineorgans and glands
Fig. 45.6
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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
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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
Smooth muscle in breast
Target effectors
Response
Milk release
Fig. 45.2b
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Hypothalamus-Pituitary Complex
The hypothalamus-anterior pituitary provides an
example of a simple neuroendocrine pathway
Pathway
Example
Hypothalamic neurohormone released in response
to neural and hormonal signals
Stimulus
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
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Major endocrineorgans and glands
Fig. 45.6
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Pancreas

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

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Pancreas

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

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Pancreas

• Exocrine function
• Digestive secretions released into pancreatic
  duct to small intestines
• Endocrine function
• Islets of Langerhans endocrine cells
• Insulin
• Glucagon

antagonistic hormones
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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

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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

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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

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Pancreas regulates blood glucose
Pathway
Example
Pathway
Example
Pathway
Example
An example of a simple endocrine pathway
High blood glucose
Hypothalamic neurohormone released in response
to neural and hormonal signals
Stimulus
Stimulus
Suckling
Stimulus
Receptor protein
Sensory neuron
Sensory neuron
Pancreas secretes insulin
Hypothalamus/ posterior pituitary
Hypothalamus
Endocrine cell
Neurosecretory cell
Blood vessel
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 ( )
Smooth muscle in breast
Target effectors
Glycogensynthesis,glucose uptakefrom blood
Response
Endocrine cell
Blood vessel
Response
Milk release
(a) Simple endocrine pathway
(b) Simple neurohormone pathway
Target effectors
Mammary glands
Milk production
Response
Fig. 45.2a
(c) Simple neuroendocrine pathway
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Hormone-like local regulators appear to be
produced by all the bodys 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

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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
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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
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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