Chapter 44 Controlling the Internal Environment http:// www.funtrivia.com/ playquiz/ quiz6309973beb0.html
Dec 26, 2015
Chapter 44Controlling the Internal Environment
http://www.funtrivia.com/playquiz/quiz6309973beb0.html
Brief Overview to Body Temperature Regulation
Each animal species has an optimal temperature range Thermoregulation: the maintenance of
body temperature within a range that enables cells to function efficiently
Animals exchange heat with their environment and need some way to replenish it This creates the difference between
warm-blooded (endothermic) and cold-blooded (ectothermic) animals
Ectotherms Ectotherms are any
animal whose body temperature is a result of their surroundings
This is common in marine animals, retiles and amphibians in particular Breeding Ball, Cobra
Mating, or Meerkats
Endotherms An endotherm is an
organism that derives its internal temperature from its own metabolism
Humans are endothermic and maintain a relatively constant internal body temperature
Being endothermic solved many of the problems associated with living on land
Homeostasis By definition, homeostasis is the
property of a system (open or closed) that regulates its internal environment so that it maintains a stable, constant condition
Nerve cells that control thermoregulation and homeostasis are concentrated in the hypothalamusThe hypothalamus is a part of the brain
responsible for linking the nervous system to other systems like the endocrine system
Water Balance and Waste Disposal
Our body has to maintain a balance between water uptake and water loss
Because of our active aerobic metabolism, there are many by-products that can be toxic if accumulated
To keep balance, our body must move solutes between body fluid and environment
Water Balance When getting rid of
metabolic wastes, solutes must pass through transport epithelium This is the layer(s)
of epithelial cells that regulate solute movement
Most epithelial tissue is arranged in tubular networks These are very
important to the urinary system
Waste Disposal
The most toxic of all by-products are nitrogen-containing wastes (from breakdown of protein and nucleic acids)
Most are form of ammonia Ammonia: excreted by marine animals Urea: mammals excrete this; 10,000
times less toxic than ammonia Uric acid: excreted by land snails, birds,
and reptiles
Osmosis Def: the movement of
water across a selectively permeable membrane
Humans are osmoregulators: we must adjust internal solute concentration to match outside environment
FYI- humans will die if they lose 12% of their body water
Excretory Systems These systems (namely the urinary) are vital
to homeostasis because dispose of metabolic waste
Urine is produced through two processes: filtration of body fluids & refinement of aqueous solution from filtration Filtration: blood is exposed to filtering device of
selectively permeable membrane Water and small solutes in excretory system
because of force of blood pressure; proteins and other large molecules too big to fit through membrane
Urine Production Reabsorpion is one of
two mechanisms using active transport Selective transport of
water and valuable solutes (glucose, salts, amino acids) from filtrate back into body fluids
Filtration is nonselective-small molecules essestial to body are returned to fluids
Secretion is another mechanism Involves adding of
solutes (salt and toxins) from the body to the filtrate
Once added to the filtrate, the solutes will pass with the urine out of the body
Kidneys & The Urinary System Kidneys are involved in
excretion and osmoregulation (maintenance of solute concentration)
Bean-shaped organs (10 cm long)
Blood enters kidneys through renal artery and leaves through renal vein FYI- kidneys 1% of body
weight, but receive 20% of blood pumped with EACH heartbeat
The Kidneys & Urinary SystemFrom the kidneys, the urine flows to
ureters which connect to the urinary bladder leaves body through urethra
There are two regions of the kidney: outer renal cortex and inner renal medulla Both filled with nephrons: functional unit
of the kidneys Contains ball of capillaries (glomerulus)
covered by Bowman’s capsule
FiltrationFiltration occurs when blood pressure
forces water, urea, salts, and solutes from the blood in the glomerulus into the Bowman’s capsuleCapillaries called podocytes act as
filter-permeable to water and small solutes but not large molecules
If molecule is small enough to fit through the capillary wall, it will be filtered because filtration is nonselective
Nephrons and Components From the Bowman’s
capsule, the filtrate goes through 3 regions of nephron: Proximal tubule Loop of Henle (had
descending limb and ascending limb)
Distal tubule Distal tubule empties
into collecting duct (filtrate from nephrons)
Nephron The nephron and
collecting duct are lined with transport epithelium to process filtrate 1100-2000 L of
blood pass through kidneys/day, nephrons process 180 L of filtrate and create 1.5 L of urine
Rest is absorbed into blood as mostly water
Secretion and Reabsorption Secretion involves
both passive and active transport
The controlled secretion of hydrogen ions from the interstitial fluid is responsible for maintaining pH Proximal and distal
tubules involved in secretion
Nearly all sugars, vitamins, and other organic nutrients are reabsorbed along with a large amount of water Proximal and distal
tubules and loop of Henle contribute to reabsorption
Selective reabsorption and secretion control concentrations of salt in body fluids
Flow From Filtrate to Urine Step 1: proximal tubule
Maintains pH of body by controlling secretion of hydrogen ions
Secretes ammonia and absorbs 90% of bicarbonate buffer
Any drug/poison in liver is absorbed here
Glucose, amino acids, K+, and NaCl are reabsorbed
Water follows the movement of salt to interstitial fluid
Step 2: descending limb of loop of Henle Permeable to water,
not to salt/solutes Water leaves loop
because it is hypotonic to the interstitial fluid around it
NaCl concentration increases
Steps to Urine Formation Step 3: ascending limb
of loop of Henle Permeable to salt, not
water Two regions: thin
segment (loop tip) and thick segment (leads to distal tubule)
NaCl diffuses out in thin segment
NaCl actively trasported out of thick segment
Step 4: distal tubule Both secretion and
reabsorption happen here
Monitors amount of K+ secreted into filtrate and amount of NaCl reabsorbed from filtrate
Controls pH regulation
Urine Formation
Step 5: collecting duct Carries the filtrate to renal pelvis and
medulla, actively absorbs NaCl Permeable to water, not salt-loses more
and more water to osmosis High concentration of urea diffuses out of
ductThese five steps are parts of each
nephron, which are the components of the kidneys
Conserving Water by Kidney Action
NaCl and urea are responsible for the osmotic gradient Each step in filtration in
the nephron is meant to maintain conservation of water
Proximal tubule (1): large amount of water and salt are reabsorbed-volume of filtrate decreases; molarity is still equal to blood
Water ConservationDescending limb of the loop of Henle
(2): water leaves tubule by osmosis and NaCl concentration increases Salt concentration peaks at elbow of loop
of HenleAscending loop of Henle (3): salt
concentration decreases because it is permeable to salt, not water Two limbs combined maintain osmotic
balance and can affect each other’s chemical changes
Water Conservation
The filtrate is hypotonic when it reaches the distal tubule NaCl concentration lowered in ascending
limbFrom the cortex to medulla, the filtrate
loses water by osmosis- concentration of urea increases Urine is isotonic in relation to interstitial
fluid but hypertonic to blood and rest of body