human body systems ib chapter 6. digestion why do we digest food? – break down molecules to pass...

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