Topic 6 - Human Physiology

Epiglottis

Covers opening of trachea when eating

Peristalsis

- Contraction of circular and longitudinal muscle layers
- Begins in esophagus, continues into the intestines
- Occurs in 1 direction
- Churns food, mixes with enzymes for digestion

Anti-peristalsis

Vomiting, stomach contracts to remove food

Stomach acid

- Kills bacteria and other pathogens
- Mucus protects the lining of the stomach from acid
- Neutralized by bicarbonate in the small intestine

Villi

- Small, finger-like projections
- Aid in nutrient absorption

Pancreas

Produces bicarbonate and other enzymes

Liver

Produces bile and other enzymes

Lipid digestion

Lipids are emulsification by bile salts to form tiny drops of triglycerides.
Lipase breaks it down into fatty acids and glycerol.

Emulsification

A process in which large lipid molecules are broken down into several small lipid molecules.
Churning action of stomach and use of bile salts in begining of small intestine

Lipase

Enzyme used to break down triglycerides

Protein digestion

Endopeptidases break peptide linkages in the protein interior to form shorter polypeptide chains.
Exopeptidases act on the ends of the chains to form dipeptides.
Dipeptidases break down dipeptides into amino acids.

Exopeptidases examples

Aminopeptidases act on the NH2 end and carboxypeptidases act on the COOH end.

Dipeptides

2 amino acids

Enzymes used for digestion

Amylase, Lipase, Protease

Cellulose digestion

Humans do not have the enzyme needed to digest cellulose.
Is excreted as waste, but provides diet with fibre, keeping digestive track healthy.

Starch digestion

Starch cannot pass through the villi, too large.
Begins in the mouth with salivary enzyme amylase, however it stops working in the stomach due to the acidity.
Pancreatic amylase continues digestion in small intestine by breaking 1-4 bonds into glucose fragments; maltose and maltriose.
Amylopectin 1-6 bonds cannot be broken down by amylase, and are called dextrins.
Enzymes from small intestine membrane turn glucose fragments into glucose.

Enzymes used to form glucose

Maltase (for maltose), Glucosidase (for maltotriose), Dextrinase (for dextrins)

Glucose absorption

Glucose is absorbed into villus by cotransport, enters into villus capillaries, moves into venules in sub-mucosa, blood is carrier to the liver, excess glucose becomes glycogen for energy storage.

Surface area increase in digestive tracts

The inner intestine wall is folded
Villi are projections on the inner wall
Epithelial cells on the villi fold into microvilli

Methods of absorption

Co-transport (for glucose and amino acids), Facilitated diffusion (for monosaccharides), Osmosis (for water), Simple diffusion (for triglycerides)

Digestive System

Gaseous exchange

the exchange of gases between an organism and it's surroundings, the uptake of oxygen and release of carbon dioxide

Factors that speed up diffusion

Surface area: greater surface area results in greater diffusion
Difference in concentration: greater concentration gradient results in greater diffusion
Length of diffusion path: shorter path results in greater diffusion

Components of Respiration

Breathing, External respiration, Internal respiration, Cellular respiration

4. Cellular respiration

Breakdown of sugar molecules into energy molecules
- Requires presence of O2, Results in production of CO2

3. Internal respiration

Exchange of gases between the blood in capillaries and individual cells
- O2 diffuses into cell, CO2 diffuses out of cell

1. Breathing

Inhalation - taking in oxygen from external environment
Exhalation - expelling carbon dioxide

2. External respiration

Exchange of gases between alveoli and the blood
- O2 diffuses into blood, CO2 diffuses out of lungs

Nasal and Oral Cavities

Warm, moisten and filter the air entering through the nose. Mucus traps small particles, Nose hairs sweep out larger particles, Cilia moves trapped particles to nose opening or down esophagus

Pharynx

Common path for food and air. Branches into esophagus (food) and trachea (air).

Larynx

Known as the voice box. Sound is produced through vibrations of the vocal cord and in the air.

Trachea

Connects pharynx to the lungs. Lined with mucus and Cilia. Branches into left and right bronchus.

Bronchi and Bronchioles

Bronchi branch into smalller tubes called bronchioles. Lined with mucus and cilia for more filtering.

Alveoli

Hollow air sac clusters at the end of the smallest bronchioles where gas exchange occurs.

Advantages of alveoli shape

1 cell thick, decreases the diffusion path
Large combined surface area due to spherical shape

Maintanence of concentration gradients

Maintained by blood flow on one side and air flow on the other.

Pneumocytes

Cells in alveoli, 2 types

Type 1 Pneumocytes

Most of the flattened epethelial cells in alveoli walls are type 1 cells

Type 2 Pneumocytes

Occupy small portion of alveoli surface.
Secrete fluids which coat the inner surface of alveoli to reduce surface tension.
Fluid allows oxygen to dissolve and diffuse into blood.

Causes of lung cancer

smoking, second hand smoke, air pollution, radon gas, asbestos, silica

Consequences of lung cancer

Very few patients survive more than 5 years.
DIfficulty breathing, coughing, chest pain, loss of appetite, weight.
Tumors can form in many parts of the body.

Emphysema

Gradual deconstruction of alveoli - thin inner walls rupture to create larger air sacs with thick walls.
The surface are is reduced - the lungs become less elastic.
Damage is irreversible.

Types of Blood Vessels

Artery, Capillary, Vein

Arteries

Thick wall, narrow lumen, has 3 layers, can stretch, is thick and muscular, carries blood away from heart

Capilaries

Thin wall, narrow lumen, wall is 1 cell thick, no muscle/elastic fibres in wall, site of gas exchange

Veins

Thinner wall than arteries, wide lumen, elastic fibres in wall, has valves in lumen, carries blood towards heart

Endothelial

Cells which line the inside of blood vessels

Arterioles

Smaller arteries

Layers of the heart

Endocardium, Myocardium, Pericardium

Endocardium

Smooth, inner linning of heart

Myocardium

Muscle, middle layer of heart

Pericardium

Fluid filled sac, outer layer of heart

Pericardial fluid

Fluid withing the pericardium, reduces friction created by the heart when beating

Coronary arteries

Carry blood supply to the heart (heart needs blood to function)

Heart Chambers

Left ventricle, right ventricle, Left atrium, right atrium

Heart valves

Tricuspid valve, Bicuspid valve, Pulmonary valve, Aortic valve, prevents blood backflow

Tricuspid valve

Separates right atrium and ventricle

Bicuspid valve

Separates left atrium and ventricle

Pulmonary valve

Separates pulmoary artery and right ventricle

Aortic valve

Separates aorta and left ventricle

Semilunar valves

Valve at the base of arteries (aortic and pulmonary valves)

Atrioventricular valves

Valves between atria and ventricles (trsicuspid and bicuspid valves)

Blood flow

Deoxygenated blood enters right atrium through the Vena Cava. Enters right ventricle and leaves through the pulmonary arteries. Goes to lungs, where gas exchange occurs. Oxygenated blood enters left atrium through pulmonary veins. Enters left ventricle and leaves through the aorta. Goes to the rest of the body. Repeat.

Sinoatrial Node (SV)

Pacemaker, sets a rythm (approx 72 beats per minute), found near right atrium

Atrioventricular Node (AV)

Passes nerve impulses to the ventricles , found on middle edge of right atrium

Cardiac Cycle

A heartbeat. 3 stages; Atrial systole, Ventricular systole, and Diastole.

Atrial stystole

SA node sends nerve impulse, causing blood in the right and left atria to be forced into the right and left ventricles.

Ventricular systole

Blood pressure in the ventricles is high, causes the atrioventricular valves to shut. Nerve impulse reaches the AV node, causing blood in the right and left ventricles to be forced into the pulmonary artery and aorta.

Diastole

Semilunar valves close to by back pressure of blood in the arteries. Atria and Ventricles relax.
Blood flows into the atria, the atrioventricular valves open and blood enters the ventricles passively.

Heart Rate

Frequency of the cardiac cycle

Blood Pressure

Force of blood on the walls of the arteries. A ratio of systolic and diastolic pressure of the blood filling and being expelled from the heart (avg is 122mm Hg / 80mm Hg).

Factors that affect Heart Rate

pH of blood, O2 concentrations, bloos pressure

pH of blood

Reflected in CO2 concentrations (combines with water to form carbonic acid, which lowers the pH). If there is too much CO2 it means the blood is too acidic and heart rate will increase.

Cardiovascular center

Located in the medullar oblongata. Receives input from recpetors in the body which monitor the factors that affect heart rate. Sends nerve impulses to the SA node which tell it whether to increase or decrease frequency of heart beats.

Atherosclerosis

Development of fatty tissue (atheroma) in lumen of arteries.

Causes of Arterioscleriosis

- High concentration of LDL (low density lipoprotein)
- High blood glucose levels (due to obesity/over eating)
- High blood pressure
- Consumption of trans fats

Consequences of Arterioscleriosis

- Affects the coronary arteries, can lead to a heart attack
- Affects the brain arteries, can lead to a stroke
- Affects the renal arteries, can lead to kidney disease
- Affects the aorta, can lead to aortic aneurysm

Epinephrene

- Hormone produced by the adrenal gland (also known as adrenaline).
- Level rises when physical activity is needed to increase heart rate
- Part of the fight or flight response

Galen

Believed the circulatory system consisted of two separate one-way systems of distribution, blood was consumed by all organs of the body, then regenerated in either the liver or the heart.

Harvey

Tied a ligature around the upper part of a man's arm. He observed that when tied tightly, blood flow into the arm's lower portion was cut off. When loosened slightly, blood flowed into the lower part of the arm but was unable to escape back to the upper part. As the veins swelled, small bumps in the veins became more noticeable and were distinguished as valves.
Showed that blood flow was unidirectional, with arteries carrying blood away from the heart and veins returning to the heart.

Immune System

Protects the body against foreign invaders using physical and chemical mechanisms.

Physical Mechanisms

Cilia, Mucous, Skin

Chemical Mechanisms

Phagocytosis, Antibodies/Antigens, Inflammatory response

Innate immune response

Nonspecific defence, 1st and 2nd line

Acquired immune response

Specific defence, 3rd line

First line of defence

External.
- Skin is an almost impenetrable barrier
- Enzymes in mucus can trap and destroy bacteria cells
- Cilia sweep debris out of the throat and nose (cough/sneeze)
- Stomach acid kills bacteria in stomach
- Enzymes in tears destroy bacteria
- Eyelashes sweep over the eye to keep bacteria out

Second line of defence

Internal.
- Lymphatic system
- Phagocytosis of a cell
- Natural Killer cells
- Antimicrobial proteins
- Fever

Lymphatic system organs

Spleen, Appendix, Thymus, Tonsils

Lymph Nodes

Specialized cells in the body which produce lymphocytes, located throughout the body (under chin, armpits, intestinal tract)

Lymph

Clear fluid which circulates in the lymphatic vessels. Contains lymphocytes (white blood cells).

Lymphatic vessels

Transports lymph from organs to the circulatory system.

Lymphocytes

Type of white blood cells; Made in bone marrow (spongy tissue in bones)

Macrophages

Type of white blood cells; Engulf pathogens, destroy pathogens with digestive enzymes.

Phagocytosis

1. Macrophages detect the presence of a bacterium
2. Bacterium attaches to the receptor on the membrane
3. Bacterium is englufed into a food vacuole
4. Lysosome in the cytoplasm fuses with the vacuole
5. Bacterium is broken up into its essential components which are disposed into the cytoplasm

Third line of defence

Creation of antibodies through lymphocytes (specialized white blood cells)

Antigens

On the surface of every foreign material which enters the body.

Examples of Antigens

- Potentially damaging microbes and their toxins
- Pollen, Flea, Dust mite feces
- Blood cell surface proteins
- Surface proteins of transplanted tissues/organs

Antigen Receptors

Located on both B cells and T cells, used to recognize antigens

Antibodies

Proteins that attach to specific antigens

Antigen/Antibody specificity

Tip of each antibody becomes specialized for a specific antigen. i.e. Only 1 antigen can bond to the tip of a specific antibody