Biological Exchanges: Diffusion and Osmosis

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Biological ExchangesDiffusion and Osmosis

• Diffusion defined The net movement of molecules
  from an area of high concentration to an area of
  low concentration.
• Example Sugar or salt dissolving in water. Think
  Koolaide, instant coffee or tea, Crystal Lite

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• Molecules are always in motion
• Difference between gas, liquid and solid

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Diffusion

• Molecules in solution tend to slowly spread apart
  over time. This is diffusion.

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Diffusion
concentrated, high energy molecules
diffuse, low energy molecules
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Concentration gradient
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Diffusion in the Body

• Occurs across cell membranes
• The cell membrane is differentially permeable
  (selective)
• Movement of water across the membrane is called
  osmosis

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Movement of Molecules Across the Cell Membrane

• Oxygen and CO2
• Water (Osmosis)
• Ions (Electrolytes)
• Sugar

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In multicellular organisms, diffusion transports
substances across small distances between the
blood and the interstitial fluid and between the
interstitial fluid and the cells
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Osmosis

• Osmosis is the movement of WATER across a
  semi-permeable membrane
• At first the concentration of solute is very high
  on the left.
• But over time, the water moves across the
  semi-permeable membrane, and dilutes the
  particles.

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Animal Cells and Osmosis
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Plant Cells and Osmosis
Vacuole fills
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Interacting Systems A second Look

• As you think about how closely related the
  functions of your circulatory and gas exchange
  systems are, you may questions how the body
  regulates their activities.
• Heartbeat and breathing require continuous
  monitoring and adjustment

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Homeostasis involves the coordinated regulation
of the bodys systems

• Homeostasis is the bodys balancing act
• Assuring that internal conditions in the body
  remain within normal limits
• Healthy Homeostasis Balanced

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Requirements for Maintaining Homeostasis

• An organisms must be able to sense changes in the
  external and internal environments
• It must be able to respond to those changes with
  appropriate adjustments

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Stimulus/ Response

• Stimulus Cold Temperature
• Response Prevent heat loss from body
• Involuntary responses
• Decreased heart rate
• Blood vessels in the skin contract
• Voluntary responses
• increase movement
• Put on more clothes

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Homeostatic responses are specific

• Hypothermia (low body temperature)
• What are the symptoms of a cold body?
• What happens to your blood?
• What happens to your breathing?
• Hyperthermia (high body temperature)
• Symptoms of overheated body?
• What happens to your blood?
• What happens to your breathing?

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Regulation of Homeostasis

• The nervous system directs rapid, short term,
  very specific responses in the body
• The endocrine system directs slower, and longer
  lasting very specific responses in the body

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Regulation happens through Feedback Systems
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Parts of a Feedback System
Stimulus
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There are two kinds of feedback systems1.
Negative Feedback

• Adjusts the response in the opposite direction
  from the triggering stimulus
• Ex cruise control in an automobile
• Ex Blood glucose levels
• Ex Plants and water regulation

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There are two kinds of feedback systems2.
Positive Feedback

• Adjusts internal conditions in the same direction
  as the triggering stimulus
• Ex amplifying sound with a microphone
• Ex Blood Clotting

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Interacting Systems A Second Look

• Heartbeat and breathing require continuous
  monitoring and adjustment
• Homeostasis requires the coordination of all the
  bodys organ systems
• Example How does the body maintain homeostasis
  during exercise?

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What happens to breathing rate ?

• Exercise requires energy
• Energy producing processes in the cells require
  oxygen and release CO2
• As you exercise, you use up the oxygen in your
  cells and produce more CO2
• As CO2 concentration increases, the blood becomes
  very acidic.
• Sensors in your brain and aorta detect the
  increase in acidity and stimulate your diaphragm
  and rib muscles to contract more rapidly

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Homeostasis and Breathing Rate During Exercise

• Stimulus?
• Receptor?
• Processor?
• Effectors?

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What Happens to the Circulatory System During
Exercise?

• Simultaneous and automatic responses of the
  circulatory system
• Heart rate increases
• 6.0 L/min ? 9.5 L/min
• ? in blood flow to muscles of legs and arms
• ? blood flow to skin
• Why you shouldnt exercise after you eat a large
  meal

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More Interactions The Lymphatic System and the
Circulatory System

• Functions of the Lymphatic System
• Distributes lymphocytes throughout your body to
  fight infection
• Maintains normal blood volume by returning excess
  interstitial fluids to the blood

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Exchange between Blood and Interstitial Fluid

• Interstitial fluid the fluid-filled spaces in
  between cells
• Our bodies are bathed in water. Water accounts
  for 2/3rds of our body weight
• Blood pressure on the capillaries forces blood
  plasma out into the interstitial spaces between
  cells
• As capillaries join to form small veins,
  interstitial fluid flows back into the blood
• The result of both blood pressure and diffusion

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The movement of fluid between capillaries and the
interstitial fluid
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• Interstitial fluid that does not return to the
  capillaries
• Collected by lymph vessels (24 liters/day!)
• The interstitial fluid which is now called lymph.
• Lymph gets returned to the heart via the thoracic
  duct
• The thoracic duct empties into the veins of the
  circulatory system near the heart.

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• Movement of lymph fluid relies on the movement of
  muscles
• Movement of legs and arms puts pressure on the
  lymph vessels and moves the fluid toward the
  heart
• What happens when lymph fluid does not return to
  the heart (blood)?

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Edema

• Have you ever experienced swelling after surgery
  or injury?
• The medical term for swollen body parts
• The accumulation of excess interstitial fluid in
  tissues and organs
• Injury and surgery damages lymph vessels
• Pressure on the injured area returns fluid to the
  heart
• Increased blood pressure fluids leave the
  capillaries, but are not returned to them

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Waste From Trillions of Cells The Urinary System

• Functions
• Eliminating certain wastes from cells
• Filters 2 Liters of blood every minute
• Urea a waste product from the liver and muscle
  cells
• Urine a complex mixture of water, urea, and
  other substances

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Exchange and the Urinary System

• Functions
• Regulating the concentration of substances in the
  blood
• sodium, potassium, and other ions
• volume of water

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Waste Removal is Vital

• The effects of kidney failure are not as
  immediate as a heart attack
• Kidney function must be restored OR
• Kidney dialysis

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Four Organs of the Urinary System
Basics About the Urinary System

• Kidneys filter the blood
• Ureters carriers filtrate (waste) to the bladder
• Urinary Bladder stores urine
• Urethra releases urine out of the body

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Renal Vein and Artery
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The Kidneys Filter the Blood
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Diagram of a Nephron
2. Renal tubule Reabsorption
Glomerulus
1. Renal Capsule Filtration
4. Collecting duct Concentration
From renal artery
To renal vein
3. Secretion
Steps in the production of urine
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Producing Urine

• Filtration Water and dissolved materials from
  the blood are forced into the renal capsule
• Rate of filtration depends upon blood pressure
• Reabsorption Water and other substances move
  back into the blood. More than 99 of filtrate
  is reclaimed.
• Diffusion
• Active Transport

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Producing Urine (continued)

• Secretion molecules from blood are secreted into
  filtrate (Urine)
• Waste products from bodys metabolic processes
• Drug removal
• Excess potassium and
• hydrogen ions (adjusts the acidity of the blood)
• Active transport
• Concentration Water is reabsorbed from the
  filtrate, concentrating the urine
• Variable quantities of water are reabsorbed
• Regulated by a specific hormone

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2.
1.
4.
3.
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• Most of the sodium is reabsorbed to the blood
• 100 of glucose is reabsorbed
• Excess glucose is removed in urine
• Symptom of diabetes

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Homeostasis and the Urinary System

• Maintaining water balance in the body
• How the body prevents dehydration
• Water level of the interstitial fluid drops
• This increases the sodium concentration in the
  interstitial fluid and the blood
• Increased sodium concentration triggers nerve
  signals and the
• Release of vasopressin (hormone) into the blood
• Vasopressin acts on the kidney tubules to
  reabsorb more water back into the blood

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Homeostasis and the Urinary System (continued)

• Increased sodium concentration also triggers a
  thirst response
• Homeostasis
• Hormone vasopressin conserves water in the blood
• Automatic response of the endocrine system
• Nervous system triggered stimulus of thirst
• Automatic response of the nervous system
• Voluntary behaviors play a role in homeostasis

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Study Questions

• Organize information about homeostasis and the
  urinary system in terms of stimulus-receptor-proce
  ssor-response
• What can a doctor tell from a blood sample?
• What information can be obtained from a urine
  sample?