Chapter 6 Barriers of the Body Interfaces with the outside

Barriers of the Body Skin, Lungs, and Digestive System The controlled exchange of molecules and heat Warm blooded animals are very expensive Rapidly turning over cells Damage repair

The Skin The surface barrier of the Body –Skin cells –Replacement skin cells –A few hairs –Sweat glands –Nerves (information: touch, temperature, and pain)

Heat, what is it? Heat Capacity Heat Transfer

Control of Body Temperature

Information out from the brain >Blood flow to the surface of the body >Heat generation by the muscles >Behavior: “Are you smart enough to come in out of the cold”?

Why is Heat Important? 106° F: Fried Brains 86 ° F: Dysfunctional Brain unable to warm its self Rate of reactions is a function of temperature Reactions are energy transfer among molecules Too much heat destroys large molecules

Heat Exchange Three Processes –Radiation –Conduction –Evaporation

Radiation Put something in between and it is blocked

Conduction Moves heat around the body and to the surface of the body Molecules of water bumping into each other Sweat is water containing heat that can be “thrown away”

Evaporation and Convection Evaporation

Temperature Regulation

Drunk

Immune Protection Macrophages (“big eaters”) –Foreign structures –Damage –Chemical messages that attract other cells of the immune system

Lungs Gas exchange Composition of Air –78% Nitrogen (N 2 ) –21% Oxygen (O 2 ) –.04% Carbon Dioxide (CO 2 ) –Traces of other gasses

Breathing In (chest expansion) Out (Chest contraction)

Bronchial Tree

Hemoglobin >Binds O 2 >The concentration of O 2 controls the ability of Hb to bind O 2  Only free O 2 plays in the concentration game  Only free CO 2 plays in the concentration game  Molecules flow from a high concentration to a low concentration

Sinks A sink is a way to remove O 2 and CO 2 from the concentration game Oxygen sink 2O 2 + Hb HbO 4 Carbon Dioxide Sink CO 2 + H 2 O H 2 CO 3 H + + HCO 3 -

Lungs: Gas exchange Air in alveoli Blood

Tissues: Gas exchange Water around cells Blood in capillary

Control of Respiration You only inhale if your brain tells you to Information in: H + concentration of the blood going to your head Your brain is responding to H + not O 2 Information out: Nerve signals to your diaphragm and intercostal muscles

Other Factors Stress: Open airways, increase depth of breathing, increase blood flow pH: drug or condition that changes blood H + concentration Drugs: Any drug that depresses brain function

Digestion

Digestive System > What we put in Protein, fat, carbohydrate, vitamins, minerals, water > Three processes Movement Breaking up big molecules Absorption into blood

Mouth Why your mother told you not to talk and eat at the same time

Stomach More water plus H + Cl - Digestive enzymes that are “ turned on” by H + H + destabilizes bonds in protein between amino acids

Small Intestine Put in OH - to neutralize H + H + + OH - H 2 O “Turns off” protein digestive enzymes Fat digestion: bile salts make oil and water mix Absorption into blood

Absorption Sifting the stream for molecules and other nutrients Nutrient filled blood goes to the liver (Hepatic Portal Vein)

Large Intestine Additional digestion by bacteria Water recovery

Control of Digestive System If you eat and when you eat What you eat Movement Release of secretions Distribution of Blood

Problems with Digestion Excessive stomach acid –Mild: heartburn –Severe: ulcers Drugs Antacids: H + + OH - H 2 O, disturbs blood pH, acid rebound Tagamet, Pepcid etc: Antihistamine that blocks production of HCl

Other Problems with Digestion Malabsorption (small intestine) eg Celiac’s disease = an autoimmune disease People do not spend enough time on digestion and absorption Many drugs cause acid production: coffee, tea, coke, alcohol, heart medicine Antibiotics can kill the “good” bacteria in the large intestine