MCAT Study Guide Biology Ch. 8 – Circulatory System 2017-08-15T06:45:06+00:00

I.          8.1:  OVERVIEW OF THE CIRCULATORY SYSTEM

A.     COMPONENTS OF THE CIRCULATORY SYSTEM

 

II.          8.2:  THE HEART

A.     VALVES – all heart valves have 3 cusps except mitral

B.     CARDIAC CYCLE

C.    HEART SOUNDS, HR, CO

D.    FRANK-STARLING MECHANISM AND VENOUS RETURN

1.     The more the ventricle is stretched, the the more forcefully it will contract; this can be achieved with larger BV, longer filling time

E.     CARDIAC MUSCLE

1.     Atria and ventricles are different functional syncytia

2.     Fast Na+ channels and slow Ca++ channels play role in depolarization of cardiac muscles

a)     Slow Ca++ channels are responsible for the plateau phase

3.     T-tubules allow maximal entry of Ca++ from extracellular environment into cell

F.     RHYTHMIC EXCITATION OF THE HEART

1.     SA Node – pacemaker; depolarization is unique (normal rate 120 BPM)

a)     Slow Na+ leak channels cause a timed, auto-depolarization

b)     Major depolarization is caused by opening of voltage-gated Ca++ channels, which are a little slower than voltage-gated Na+ channels

c)     Repolarization occurs when voltage-gated Ca++ channels close, K+ channels open, driving membrane potential back down to K+ ⇋ potential

2)     Other cardiac cells

a)     RMP of cardiac cells is close to -90mV (near K+ ⇋)

b)     AP stimulates voltage-gated Na+ channels to open causing depolarization

c)       At about 40mV, Na+ channels close and K+ channels open (K+ out) and Ca++ channels open (Ca++ in), causing them to balance each other out (plateau phase)

d)     Repolarization happens when Ca++ channels close, and K+ channels continue to let K+ out.

e)     RMP → K+ channels close, and Na+/K+ atpase and slow K+ leak channels balance each other

G.    REGULATION OF THE HEART BY THE ANS

1.     Vagus nerve inhibits SA node

2.     Sympathetic can stimulate with NE

3.     Adrenals can stimulate with E

III.          8.3:  HEMODYNAMICS

A.     Ohm’s law:

1.     ΔP = QR (Q = flow, ΔP = pressure gradient)

 

 

IV.          8.4:  COMPONENTS OF BLOOD

A.     RBCs

1.     Glycolysis only

B.     BLOOD TYPING

1.     Type O is universal donor, but these people produce anti-A and anti-B abs

C.    LEUKOCYTES

1.     Macrophages and neutrophils move by amoeboid motility and exhibit chemotaxis

2.     T-cells – kill virus-infected cells, tumor cells, reject tissue grafts, control immune response

D.    PLATELETS AND HEMOSTASIS

1.     Megakaryocytes – precursors of platelets

2.     Fibrin – converted from fibrinogen (plasma protein) by thrombin

3.     Hemophila – results from defects in plasma proteins associated with clotting

 

V.          8.5:  TRANSPORT OF GASES

A.     OXYGEN

1.     Hemoglobin has higher affinity for O2 in lungs than capillaries because partial pressure of O2 is higher there

2.     Bohr effect – certain factors stabilize tense configuration of hemoglobin:

a)     ↓ pH

b)     ↑ CO2

c)     ↑ T

B.     CO2

1.     Most CO2 is transported by conversion to carbonic acid (73%)

2.     Some is transported by hemoglobin (not O2 binding sites) (20%)

3.     Some transported by dissolving in blood (7%)

C.    EXCHANGE OF SUBSTANCES ACROSS CAPILLARY WALL

1.     Capillary intracellular clefts – allow nutrients, waste and WBCs to pass through (gas can pass through cells by simple diffusion)

2.     Oncotic pressure (plasma pressure) helps keep most of the water in the capillaries, but some leaks out at the front end, travels through interstitial spaces, and is picked back up at the end of the capillary bed

 

VI.          8.6:  THE LYMPHATIC SYSTEM

 

VII.        8.7:  THE IMMUNE SYSTEM

A.     INNATE IMMUNITY

1.     Skin (barrier, plus acidic pH)

2.     Tears, saliva, blood (contain lysozyme, enzyme that destroys bacterial walls)

3.     Stomach acidity

4.     Macrophages and neutrophils

5.     Complement system

B.     HUMORAL IMMUNITY, ANTIBODIES, AND B CELLS

1.     Antibodies – humoral immunity

a)     Composed of 2 copies of 2 different polypeptides (light chains and heavy chains), joined by disulfide bonds

b)     Each Ab has constant region and variable region

c)     Epitope – small site the Ab recognizes

d)     Can help in 3 ways:

(1)   Directly inactivate antigen

(2)   Induce phagocytosis by macrophages, neutrophils

(3)   Activate complement system

2.     B cells – differentiate into plasma cells (produce Abs) and memory cells (dormant cell)

a)     Note – B cells and T cells have DNA recombination!

b)     Primary immune response – first exposure to antigen, can take > 1 week for sufficient Abs to be produced

c)     Secondary immune response – swifter and stronger response

C.    CELL-MEDIATED IMMUNITY AND THE T CELL

1.     T-helper cells (CD4) – controller of the whole immune response; releases lymphokines and interleukins

a)     Activated by MHC II proteins, present only on APC cells (macrophages and B cells)

b)     The MHC II proteins display chopped up antigens

c)     Once the T-helpers are activated, they in turn activate B cells and T-killers

2.    T-killer cells (CD8) –  destroy abnormal host cells (virus infected, cancer cells, or graft cells)

a)     Activated by MCH I proteins, present on all nucleated cells

MCAT Study Guide Biology - Kim Matsumoto


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