Chapter 1: An Introduction to Physiology

-physiology: the study of the functions of living things

1. skeletal2. articular3. muscular4. digestive5. respiratory6. urinary7. reproductive8. circulatory9. nervous10. integumentary11. endocrine

-the human body is comprised of 11 major organ systems:

- in studying these systems we can use two approaches:1. teleological

-emphasizes the purpose of a body process -explains a function in terms of meeting a bodily need-emphasizes the WHYe.g. “why do I shiver?” – to warm up because shivering generates heat

2. mechanistic-emphasizes the underlying mechanism by whichthis process occurs-view the body as a machine whose actions can be explainedin terms of cause and effect-emphasize the HOWe.g. “why do I shiver?” – detection of body temperature by sensoryreceptors leads to activation of the somatic division of the nervoussystem and trigger the involuntary contraction of skeletal muscles

-physiology is closely related to anatomy – because structure and function are closely related-physiological mechanisms are made possible because of the structure and designof a body part-some relationships are obvious – e.g. structure of the elbow as a hinge joint-others are more subtle – e.g. interface between the air and the blood in the lungs

-air sac structure + capillary bed - 300 million air sacs + associated capillaries providesa total surface area for gas exchange = tennis court

Life: Levels of Organization

•Atoms •Molecules•Macromolecules•Organelles•Cells•Tissues•Organs•Organ systems•Organism

Organizational Levels

1. chemical or molecular: 4 major elements within the body

-99% of the total number of atoms within the body

-C, N, O and H

-molecular composition - 67% of our bodies is water

Atom = smallest unit of an element that still retains the chemical &physical properties of that element

i.e. really, really, really tiny thing!

-composed of: protons = one positive charge, 1 atomic mass unit (1.673x10-24g)electrons = one negative charge, no mass (9.109x10-28g)neutrons = no charge, 1 atomic mass unit

-elements are grouped on a Periodic Table of Elements-the elements are grouped according to physical and chemical characteristics-on the chart each element is associated with a letter, an atomic number& an atomic mass-each atom is comprised of a nucleus of protons and neutrons + orbiting electrons

Periodic Table of Elements

http://www.chemicalelements.com/http://periodic.lanl.gov/default.htm

IA IIA VIIAVIIIIIIA IVA VA VIA

126 C

atomicmass (weight)

atomicsymbol

atomicnumber

e.g. # protons (e-) = 6 # pr+6 + #No 6 = 12

73 Li e.g. # protons (e-) = 3

# pr+3 + #No 4 = 7

Atomic mass = number of protons + neutronsAtomic number = number of protons when the element is electrically neutral** when neutral, the number of protons and electrons are equal

Isotope:• same atomic # (same pr+, same e-)• differs only in # of neutrons

Radioactive isotope uses:-radioactive isotopes have a high neutron to proton ratio-the nuclear “glue” within the nucleus is not strong enough to hold the nucleus together = radioactivity1. carbon dating - 14C2. radioactive imaging - e.g. PET scanning

-use of FDG – radioactive glucose tracer-18F radioactive isotope (2-fluoro-deoxy-glucose)

3. cancer treatment - 60Co

12C 13C 14C pr+: 6 6 6e-: 6 6 6No: 6 7 8** radioactive

Chemical bonds

-forces holding atoms together = chemical bonds-different kinds of chemical bonds – but all involve the electrons of atoms

Two types of bonds:

1. Ionic

2. Covalent

Electron Configurations• Bed check for electrons• description on how are electrons organized around the nucleus

of protons and neutrons?• Bohr model: Nils Bohr proposed electrons orbit around the

atom’s nucleus in specific energy levels or orbits (shells)– these shells have a specific energy level – closer the electron is to the

nucleus the less energy it needs to “orbit”– this model only works for smaller atoms– larger atoms are described by quantum mechanics – orbitals have

energy, momentum/shape, spin and magnetic characteristics– comprised of subshells– 1st shell – closest to the nucleus only holds 2 electrons (s subshell only)– 2nd shell can hold 8 (s and p subshells – 2 + 6 electrons)– 3rd holds 18 (s, p and d subshells – 2 + 6 + 10 electrons)– 4th holds 18

•an atom will always try to complete its outermost shell•basis for bonding reactions•the number of electrons the atom gains or loses to complete its outer shell = valence•chemists really only consider the electrons in the s and p orbitals as valence electrons

Molecule:

•particle formed by the union of more than one atome.g. same kind of atom - O2

e.g. different types of atoms - H20

Molecules are held together by either covalentor ionic bonds

-these bonds form through interactions between the valence electrons

1. Ionic bond: • attraction between 2 oppositely charged atoms (ions)

e.g. Na+ and Cl- NaCl

e.g. Ca2+ and Cl- CaCl2

-positively charged ions = cations-negatively charged ions = anions-these form as one atom transfers electrons to another atom-ions may also be composed of more then one atom = polyatomic-these are treated as the same as monoatomic ions

e.g. sulfate SO43-, nitrite NO2

-, hydroxide OH-

Ionic Reaction

-most of your group I and group IImetals will form ionic bonds with thegroup VIIA halogens

2. Covalent Bond:•if it isn’t favorable for an atom to gain or lose an electronit will have to share it with another•covalent bond = bond in which atoms share electrons

e.g O2, , N3

e.g H20-usually forms when one atom has to lose or gain three or more electronse.g. carbon would have to gain 4 valence electrons to complete its outer shell nitrogen would have to gain 3 valence electrons

-also form between two identical atoms – e.g. nitrogen, oxygen gas

Polar and Non-polar bonds

• the sharing of electrons does not have to be equal

• nonpolar covalent bond = equal sharing of electrons– e.g. oxygen (O2), methane (CH4)

• polar covalent bond = uneven sharing of electrons leading to a slight charge– e.g. water = H20

O

H H

-

++

Water:• 60-70% of body weight• covalent bond• POLAR molecule (uneven sharing of electrons)

•polar compounds are attracted to other•the bond between one oxygen andthe hydrogens of adjacent watermolecules = Hydrogen Bond**HB = occurs between a covalentlybonded hydrogen and negativelycharged atom a distance away

Chemical reactions:3 types:

1. Synthesis - A + B AB (Anabolism reactions)

2. Decomposition - AB A + B (Catabolism reactions)

3. Exchange - AB + CD AD + BC

-these equations must be balanced-Law of conservation of Mass or “chemical bookeeping”-i.e. the number of atoms of each element is the same before and after a chemical reaction

Chemical reactions

• are made up of reactants and creates products• these reactions go on constantly within the human body

= metabolism• each reaction involves changes in energy

– if the reaction requires energy = endothermic (anabolism)– if it liberates energy = exothermic (catabolism)

• atoms, molecules and ions are continuously moving and colliding with one another = kinetic energy– this kinetic energy if big enough (i.e. collision is large

enough) can break a bond or cause a new one to form– this collision energy = activation energy– critical to the progression of all chemical reactions in our

body– the more often a collision occurs the greater chance a bond

will form or break

Activation Energy & Catalysts• activation energy = initial “energy

investment” required to start a reaction– the reactants must absorb enough

energy to cause their chemical bonds to become unstable and created new ones

– as these bonds form – energy is released into the environment – if more energy is released than absorbed = heat (exothermic reaction)

– two influences on AE – temperature and concentration

• concentration – increasing this increases the chance of collision between atoms

• temperature – heating a reaction increases the kinetic energy of the reactants – collide more often

• catalysts = compounds that lower the activation energy of a reaction

Molecules of Life:

• the chemicals used in metabolic reactions or those that are produced by them can be classified into 2 groups:

1. Inorganic2. Organic

Inorganic Compounds

water oxygen,carbon dioxide inorganic salts

Water• major component of blood, plasma, CSF etc…• role in: transporting chemicals transporting waste products

transporting & absorbing heat• polar molecule - asymmetrical distribution of charge• liquid at room temperature – we can drink it•universal solvent for polar compounds – facilitates most chemical

reactions in the body-water molecules are cohesive – therefore they cling together (because of hydrogen bonding)

-this allows the even distribution of dissolved substancesthroughout our system – so water is an excellent transportmedium

-the temperature of water rises and falls slowly – prevents sudden and drastic changes of temperature in our bodies-water requires high heat to evaporate – it cools our bodies-frozen water is less dense than liquid water – ice floats -water freezes from the top down – allows aquatic organisms to survive winters

O

H H

-

++

Water:

-excellent solvent for dissolution of polar and ionic substancese.g. H20 + NaCl

-in a solution – a solvent dissolves another substance calleda solute-water is a versatile solvent because of its polar covalent bonds and its bent shape which allows it to interact with its neighbours very well

•ions and molecules that react with water =

•ions and molecules that don’t react =

-water + salt: the electronegative O ofwater attracts the +ve sodium in salt, theelectropositive H attracts the –ve chlorine-the salt becomes surrounded by watermolecules and the crystal lattice of saltis broken up

Solutions, Colloids and Suspensions

• solution = homogenous (same) mixtures containing a relatively large amount of one compound (solvent)

– e.g. sugar + water– the mixture is the same no matter where you sample it

• colloid = solution of larger components called dispersed-phase particles– these particles all carry the same charge (repel each other)– their particles are larger than that of solutions

• e.g. plasma proteins within the blood• suspension = solution of larger components called dispersed-phase

particles– larger particles than that of colloid– if left undisturbed these particles will settle out to form a solid

• e.g. red blood cells within blood• mixture = two or more types of elements or molecules physically blended

together without the formation of physical bonds between them– these individual compounds can be separated by physical or chemical means– types of mixtures: combination of solutions, suspensions and colloids

Electrolytes• substances that release ions when they react with water-these ions will conduct electricity = Electrolytes-created through the decomposition of ionic substances

e.g. salt-although polar compounds can also liberate electrolytes

Inorganic salts: • abundant in body fluids• source of ions eg. Na+, Ca2+, K+, Mg2+

ions play a role in: maintaining water concentration maintaining pH

bone development muscle function

nerve function ions must be maintained in a certain concentration

to maintain homeostasis

Inorganic Acids & Bases•3 types: 1. release H+ Acids

e.g. HCl H+ + Cl-

2. release ions to combine with H+ Basese.g. NaOH Na+ + OH-

3. acids + bases Salts e.g. HCl + NaCl H20 + NaCl

•one must consider acids & basesin light of how they mix with watere.g. HCl when mixed in waterdissociates into H+ ions and Cl-

ions•if a base such as NaOH is added – it will dissociate into Na+ ions and OH- ions- the Na+ ions will combine with the Cl- ions toform NaCl, the H+ ions will combine with theOH- ions to reform water.

pH Scale• measures concentration of H+ ions in a solution

e.g. pH 6 = 1 x 10-6

pH 7 = 1 x 10-7

pH 8 = 1 x 10-8

Buffers:

• chemical or compound that keeps the pH of a solution withina normal range• resists pH change by taking up excess H+ or OH- ions

e.g. blood = pH 7.4“Bicarbonate buffering system”

- our blood contains a small amount of carbonic acid

H2CO3 H+ HCO3-

excess OH- excess H+

+

H20

H2CO3

carbonic acid

Organic Compounds

H HC

H

H

C

H

HC

H

HC

H

HC

H

HC

H

H

C

H

H

H

H

CC

CC

C CH H

HH

HH

HHHH

• always contain carbon, oxygen and hydrogen• carbon can form 4 covalent bonds with other atoms

e.g. methane

• carbon can also form covalent bonds with itselfforming long chain hydrocarbons

or a ring structure

hydrophobic(non-polar)

symmetrical charge

Organic compounds

• the skeleton of carbon and hydrogen are frequently combined with other atoms and molecules = functional groups

CH C

H

H

C

H

HC

H

H

O

O-

carboxylgroup = polar group

hydrocarbon + carboxyl group “hydrophilic”

these groups confer a specific property to the organic compound

e.g. amino acid vs. nucleotide

Organic substances:1. carbohydrates2. lipids3. proteins4. nucleic acids

1. Carbohydrates:• provide energy to cells• supply materials to build certain cell structures• stored as reserve energy supply (humans = glycogen)

• water soluble• characterized H - C - OH (ratio C:H 1:2)

e.g. glucose C6H12O6

sucrose C12H22O12

• classified by size: simple - sugars complex – polysaccharides

-see Table 2-6 (Tortora)

monosaccharidesdisaccharides

A. Simple carbohydrates

• monosaccharides = single sugar in which the # of carbon atoms is low - from 3 to 7

e.g. pentose - 5 carbon sugar hexose - 6 carbon sugar

pentose sugars: ribose deoxyribose

hexose sugars: glucose galactose fructose

-three ways to represent the structure of glucose

1. Molecular form 2. 3. Simplest form

A. Simple carbohydrates

• disaccharide = two 6-carbon monosaccharides -form by a dehydration synthesis reaction-broken up by a hydrolysis reaction

e.g. glucose + glucose = maltose

e.g. glucose + fructose = sucrosee.g. glucose + galactose = lactose

B. Complex carbohydrates:

• built of simple carbohydratese.g. glycogen

starch cellulose• multiple, repeating monomers or “building blocks” polymer

Starch & Glycogen

• starch = storage form of glucose found in plants -hydrolyzed into glucose• glycogen = storage form of glucose found in animals -hydrolyzed into glucose (in liver)

Cellulose• polysaccharide found in cell walls in plants• linkage between glucose monomers differs from starch• indigestible

Lipids• many types

– 1. triglycerides = fats and oils– 2. phospholipids– 3. steroids

• cholesterol – animal cell membranes, basis for steroid hormones• bile salts - digestion• vitamin D – calcium regulation• Adrenocorticosteroid hormones• Sex hormones

– 4. Eicanosoids• prostaglandins• leukotrienes

– 5. Others• fatty acids• carotenes – synthesis of vitamin A• vitamin E – wound healing• vitamin K – blood clotting• lipoproteins – HDL and LDL

2. Lipids

A. Fats• energy supply• most plentiful lipids in your body• composed of C, H and O• “building blocks” = 3 fatty acid chains (hydrocarbons)

1 glycerol molecule

fatty acid

fatty acid

fatty acid

glycerol portion fatty acid portion

• fatty acids - carboxyl at end -differ in chain length with each fat

-differ in carbon bonding

1. single C bonds - saturated

2. double C bonds - unsaturated

monounsaturated:1 double bond

polyunsaturated:2 or more double bonds

carboxyl gp

-some fatty acids cannotbe made by the bodyand must be taken inthrough food = essentialfatty acids

e.g omega-3 fatty acids-polyunsaturated fatty acids-important in regulating cholesterollevels -lower LDL levels in the blood-increase calcium utilization by body – stronger bones & teeth-reduce inflammation – arthritis-promote wound healing

B. Phospholipids

• form the majority of the cell membrane = lipid bilayer

• similar to fat molecules - glycerol + 2 fatty acids+ a phosphate group

• phosphate gp hydrophilic “head”• fatty acid gps hydrophobic “tails”

C. Steroids

• backbone = 4 fused carbon rings• diversity through attached functional groups

e.g. cholesterol testosterone, estrogen

aldosterone

3. Proteins• roles: structural

energy sourcechemical messengerscombine with carbohydrates = glycoproteinsreceptorsantibodiesmetabolic role - enzymes

• building blocks = amino acids

a.a. = amino group at 1 end, carboxyl at the other between is a single C atom bound to: 1. H atom 2. R group

HO CC N

H

H

R H

HO

carboxyl gp amino gp

some amino acids:asparaginealaninearginineaspartic acidcysteineglutamic acidglycinehistidineleucinelysinephenylalanineprolineserinethyminetyrosinetryptophanvaline

• amino acids joined together by a condensation reactionforming a peptide bond = between the NH2 of 1 a.a. and the COOH of the next

CC N

H

H

R H

HO

HO CC N

H

R H

HO+ -

peptide bond = polar

2 a.a. dipeptide

3 a.a. tripeptide

4 or more a.a. polypeptide

• polypeptides have 4 types of structures or conformationswhich affect their ultimate function

Protein conformation:

1. primary - a.a. sequence of polypeptides

2. secondary - a.a. chain folds into -helical coils or -pleated sheets

3. tertiary - coiled a.a. helix folds into a unique

3-D shape

4. quaternary = joining of 2 or more polypeptides

Enzymes

4. Nucleic acids

• make up DNA, RNA• C,H,O,N,P• building blocks = nucleotides

• nucleotide: 5 carbon sugar (pentose)•this pentose sugar has precise numbering of its carbons

phosphate group (negative charge)organic base - 4 types: adenine (A)

cytosine (C) guanine (G)

thymine (T)uracil (U)

• polynucleotide chain - formed by a phosphate bond betweenthe phosphate (5’) of 1 n.t. and the sugar of the next (3’)

• two major types of nucleic acids:1. RNA sugar = ribose2. DNA sugar = deoxyribose

ribose deoxyribose

HOCH2

H

OH

H

OH

O OH HOCH2

H H

H

O OH

OH

• so a DNA/RNA chain “grows” in one direction only-5’ to 3’

A. RNAsingle p.p chainbases: A, C, G and uracil

(U) in place of T3 types: mRNA

tRNA rRNA

B. DNAdouble p.p chain = double helix

2 chains held by hydrogen bonds between the bases

bases pair up in a complementary fashion

A = TC G

sense strand (5’ to 3’) anti-sense strand

Figure 2.17

c. ATPindividual n.t’s can have metabolic functions

e.g. adenosine = adenine + ribose-adenine modified by adding three phosphates

major source of ATP = breakdown of glucose1 glucose molecule

36 ATP

glycolysisKreb’s cycleoxidative phosphorylation