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Human Body Systems
IB Chapter 6
Digestion
• Why do we digest food?– Break down molecules to pass across the cell
membrane.
Steps of Digestion
• Ingestion: eat the food• Digestion: Chemical rxns that convert food to
smaller and smaller particles• Absorption: Small molecules absorbed
through cells and pass to blood stream• Transport: circulatory system delivers
molecules to body cells
MoleculesMolecule Type Molecular form ingested Molecular form after
digestionProtein Protein Amino acids
Lipids Triglycerides Glycerol and fatty acids
Carbohydrates Poly-, Di-, and Monosaccharides
Monosaccharides
Nucleic Acids DNA, RNA nucleotides
Enzymes in Digestion
• Enzymes lower activation energy and allow molecules to be broken down
• Enzymes are molecule specific• In digestion, specifically aid hydrolysis
reactions
EnzymesSalivary amylase Pepsin (Protease) Pancreatic Lipase
Source Salivary glands Stomach cells Pancreas Cells
Substrate Amylose (starch) Proteins (polypeptides)
Lipids
Products Maltose and glucose
Amino acids Glycerol and fatty acids
Optimum pH Neutral (7) Acidic (3) Neutral (7)
Human digestive system
• Mouth: breaks up food• Esophagus (oesophagus in IB): transport to
stomach by peristalsis (muscle contractions)• Stomach: churns to mix food with enzymes– pepsin– Hydrochloric acid: creates proper pH for pepsin
and helps break down– Mucus: lines stomach to prevent damage from
acid
Human digestive system
• Small Intestine:– Bile from liver and gall bladder– Trypsin, lipase, and amylase from pancreas– Absorbs most of the food– Inner wall is lined with villi• Contains lacteal and capillary bed• Increases surface area
Human digestive system
• Large Intestine: Main function is absorption of water.
• Contains bacteria (E. coli) that helps synthesize vitamin K and maintain healthy environment
• Undigested food leaves as waste
Circulatory System
• The Heart– Pulmonary side (Right side): capillary bed is in
lungs, blood picks up oxygen and releases carbon dioxide
– Systemic side (Left side): capillary bed is in body organs, blood picks up carbon dioxide and releases oxygen
– Coronary arteries supply the heart with blood and oxygen
The Heart
Control of Heart Rate
• Myogenic contractions: cardiac muscle contracts and reacts without nervous system signals
Control of Heart Rate
• Controlled by Sinoatrial node (SA node):– Mass of tissue in atrium walls– Pace maker: controls atria
• Also atrioventricular node (AV node): – Mass of tissue in right atrium– Contracts ventricles about .1 sec after SA fires
Control of Heart Rate
• Chemicals can influence heart rate– Adrenaline: Causes SA node to fire more
frequently
Circulatory System
• Arteries: blood vessels taking blood away from the heart
• Veins: collect blood from capillaries and return it to heart (Internal valves that act as backflow preventers)
• Capillaries: found after arteries to distribute blood to certain areas
Circulatory SystemArteries Capillaries Veins
Wall thickness Thick walled 1 cell thick Thin walled
Gas exchange None All (CO2 and O2) None
Valves No internal valve No internal valve Internal valves
Pressure High Low Low
Components of bloodComponent Description
Plasma Liquid portion of blood
Erythrocytes Red blood cells (carry O2 and CO2)
Leucocytes White blood cells (Phagocytes and lymphocytes)
Platelets Cell fragments (blood clotting)
Transport by BloodWhat is transported? What it is or does
Nutrients Glucose, amino acids, etc
Oxygen Reactant needed for aerobic cell respiration
Carbon dioxide Waste product of Rs
Hormones From gland to target cells
Antibodies Proteins involved in immunity
Urea Nitrogenous waste
Heat Skin arterioles (change diameter in order to gain or lose heat)
Is deoxygenated blood blue?
• No!• Oxygenated blood is bright red• Deoxygenated blood is dark red• Veins appear blue because light is diffused
through skin• When skin is removed, can’t tell between
veins and arteries
END of PART 1
Defense Against Disease
• Germ Theory: Pathogens cause disease.• Pathogen: Any living organism or virus that is
capable of causing a disease.
Bacteria
• Bacteria are prokaryotic– Differ in biochemical pathways and reactions– Different structures
Antibiotics
• Antibiotics: take advantage of these differences– Block cell’s ability to make protein– Block cell’s ability to make cell membrane or wall
Antibiotics
• No effect on viruses– Insert their DNA into body cells and use our
metabolism– Cannot block pathways without blocking all cell
pathways and killing all cells.
Preventing Pathogens
• Skin: Barrier to infection– Outer layer is dead and constantly being replaced– Bacteria cannot infect dead tissue– Cuts and open skin need to be treated
Preventing Pathogens
• Stomach Acid: Acidic environment kills most of the ingested pathogens
Preventing Pathogens
• Mucus: Blocks pathogens that enter through air– Sticky to trap pathogens– Contain lysozymes which chemically damage
pathogens– Cilia surround mucus cells and move pathogens to
trachea to cough out
Immune System
• Phagocytic leucocytes: ingest pathogens– Macrophage: Ingests pathogens by amoeboid
movement– Contain lysosomes which break them down
Immune System
• Macrophage steps1. Recognize whether cell is “self” or “non-self”
a. Based on glycoproteins in membrane
2. If non-self, it engulfs it and lysosomes digest it.
• Non-specific response: engulfs anything that is foreign
Antibodies
• Protein molecules that are produced in response to a specific pathogen
• Antigens: proteins on the outer coat/membrane of pathogens
• Each antibody is specific to each antigen
More on Antibodies
• Y-shaped • Each end has a binding site that attaches to
the antigen.
B-lymphocytes
• Leucocyte that produces antibodies• Can only produce one kind of antibody
Typical Immune Response
1. Antigen is identified (virus)2. B-lymphocyte is identified that will bind3. B-lymph. Clones itself rapidly to increase #4. B-lymphs begin producing antibodies5. Antibodies circulate6. Eliminate pathogen7. Some B-lymphocytes remain for next time
(memory cells)
HIV
• Infects Helper T-cells• Communicate which cells need to undergo
cloning for antibody production• When they die no antibodies are produced• AIDS: once they stop fighting infections– Usually die of secondary infections
Issues related to AIDS
• Virus hides away for years• Virus mutates quickly• Association of AIDS to drug use and sexual
activity– Initial reluctance for funding– Blood wasn’t tested before transfusions– Led to discrimination by employers, insurance,
and education facilities
Respiratory System
• Purpose: To provide the cells with Oxygen so they can undergo cell respiration
Respiratory system
• Ventilation: Filling our lungs with air, then breathing that air out
• Gas exchange: Diffusion of the gases into and out of the capillaries
• Cell respiration: Breaking down glucose into ATP and CO2
Respiratory System
• Why do we need one?– Gases cannot diffuse very far– Concentration of gases in the lungs encourages
diffusion
Alveoli
• Clusters at the ends of the bronchioles– Surrounded by capillary bed– Where gas exchange occurs
AlveoliAdaptation Advantage
Spherical shape Provides a large surface area for respiratory gases to diffuse through
Flattened, single cell thickness
Prevents gases from having to diffuse through too many layers
Moist inner lining of alveolus
Allows for efficient diffusion
Associated capillary bed nearby
Gases do not have to diffuse far to reach blood stream
Mechanism of inspiration
1. Diaphragm and intercostal muscles contract2. Pressure decreases and lung tissue increases
in volume3. Decrease in pressure inside (partial vaccuum)4. Air comes in through mouth and nose
Breathing
Nervous System
• Central Nervous System: Spinal cord and brain• Neurons (Neurones): cells that carry nerve
impulse.
Peripheral Nervous System
• Sensory and Motor nerves• Two categories:– Spinal nerves: emerge directly from spinal cord– Cranial nerves: nerves from the brainstem
Typical pathway
• Stimulation: Transform a stimulus into an action potential
• Interpretation: occurs in the brain– Chain of nerves that takes the action potential to
the brain• Response: Pathway begins in the brain and
travels down to the motor neurons
Nerve Impulse
• Kind of like a flow of electrons down the neurons
Resting potential
• State of being of a nerve that is ready to send an action potential
• Active transport of Na+ and K+ in two different directions– Na+ out of axon– K+ into axon cytoplasm
Resting potential
• Collection of ions leads to a net positive charge outside the axon and net negative inside
• Sets up concentration gradient
Action Potential
• Diffusion of Na+ back into the cell and K+ back out of the cell.
• Moves “impulse” down the axon. • Once you start the potential it will self-
propagate down the axon
Resting RestingAction potential
Synaptic transmission
• How neurons communicate with each other• Terminal end dendrites of the next• Chemical transmission
Synaptic transmission
• Neurotransmitter: any chemical that is used for transmission– Acetylcholine– Serotonin
Mechanism
• Terminal end releases chemical • Dendritic end of next neuron engulfs chemical
by phagocytosis
Serotonin reuptake inhibitors (SRI)
• Drug that blocks the reuptake in the next nerve
• Serotonin is the neurotransmitter involved in depression
• Builds up serotoninbetween nerves
Homeostasis
• Keeping the body at its normal limits with nervous and endocrine systems– Blood pH– CO2 concentration– Blood glucose concentration– Body temperature– Water balance within tissues
Control of body temp
• By Hypothalamus• Senses temp rising from thermoreceptors in
the skin• Too Hot: Begins cooling regimen– Increased sweating- evaporative cooling– Arterioles dilate- increased radiation
Control of body temp
• Too Cold• Warming regimen– Constricting skin arterioles- blood travels to
deeper organs– Stimulates skeletal muscles to shiver
Control of Blood Glucose levels
• For Cell Rs• Glucose you eat travels to liver cells• There it triggers one of two hormones; insulin
or glucagon
Glucose Too High
• Beta cells in pancreas produce insulin• Insulin opens membrane proteins to allow
glucose to diffuse into cellOR• Liver will catch the glucose and store it as
glycogen
Glucose Too Low
• Use the glycogen reserves• Alpha cells of the pancreas produce glucagon• Stimulates hydrolysis of glycogen• Glucose enters bloodstream
Diabetes
• Type I (10%): when beta cells do not produce enough insulin
• Type II (90%): when body cell receptors do not respond properly to insulin (doesn’t open channels)
Diabetes
• Type I: controlled by insulin injections• Type II: controlled by diet• Uncontrolled can lead to:– Damage to retina– Kidney failure– Nerve damage– Risk of cardiovascular disease– Poor wound healing