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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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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Movement of Molecules Across the Cell Membrane

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

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Animal Cells and Osmosis
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Plant Cells and Osmosis
Vacuole fills
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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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The movement of fluid between capillaries and the
interstitial fluid
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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
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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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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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Bill Clintons Heart Surgery

• Complained of chest pain and shortness of breath
• Diagnosis 4 blocked arteries

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What was happening inside of Clintons body?

• 4 blocked arteries
• Chest pain
• Shortness of breath

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More Interactions

• The Lymphatic/Immune 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
• Edema swollen body parts

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• Interstitial fluid that does not return to the
  capillaries
• Lymph vessels collect interstitial fluid which is
  now called lymph.
• Lymph gets returned to the heart via the thoracic
  duct that empties into the veins of the
  circulatory system near the heart.

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Waste From Trillions of Cells
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Exchange and the Urinary System

• Eliminating certain wastes from the body
• urea
• Regulating the concentration of substances in the
  blood
• sodium, potassium, and other ions
• volume of water
• Urine a complex mixture of water, urea, and
  other substances

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Four Organs of the Urinary System

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

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The Kidneys Filter the Blood
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Diagram of a Nephron
3. Renal tubule Reabsorption
Glomerulus
2. Renal Capsule Filtration
5. Collecting duct Concentration
1. From renal artery
To renal vein
4. Secretion
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Processes within the Urinary System

• Filtration fluid from the blood is forced into
  the renal capsule
• Reabsorption molecules from the filtrate are
  reabsorbed into capillaries
• Secretion molecules from blood are secreted into
  filtrate
• Concentration water is reabsorbed from the
  filtrate, concentrating the urine

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