physio

Question 1

How does the volume of blood vary in different genders?

Answer 1

Women: 5 liters; men: 5.5 liters.

Question 2

What percentage of total body weight is usually attributed to blood?

Answer 2

8%.

Question 3

What are the two main components of blood and their percentages?

Answer 3

Plasma → 55% of blood volume
cellular elements → 45% of blood volume.

Cellular elements refer to RBCs, WBCs, platelets, etc.

Question 4

What is hematocrit?

Answer 4

AKA the packed cell volume; it is the % of total blood volume occupied by RBCs only.

Normal hematocrit is around 45%.

Question 5

A couples decides to get blood tests together before planning for future children. What should the RBCs and Hb values look like for a healthy hetero couple?
After they get the results, their doctor tells them their WBCs and platelet count is the same. What range does that typically lie in?

Answer 5

Woman → RBC = 4.8 million/mm³ ; Hb = 14g/dl;
Man → RBC = 5.4 million/mm³ ; Hb = 16 g/dl.

WBCs will be around 4000-11000/mm³;
platelet count will be 150,000 - 400,000/mm³.

Question 6

What are the three specialized cellular elements in blood and their functions?

Answer 6

1. Erythrocytes (RBCs) → important in O2 transport.
2. Leukocytes (WBCs) → immune system defense units.
3. Platelets → important in hemostasis (prevention of blood loss from damaged blood vessels).

Question 7

What is plasma composed of?

Answer 7

It is 90% water and 10% solids.

1% accounts for electrolytes and 6% for plasma proteins. Solids include: electrolytes [Na⁺, Cl⁻, K⁺, HCO₃⁻, Ca²⁺], plasma proteins [albumin, globulins, fibrinogen], organic substances [glucose, amino acids, lipids, vitamins], waste products [urea, creatinine], gases [O₂ and CO₂].

Question 8

What are the components of plasma?

Answer 8

1. Plasma proteins (albumin, globulins, fibrinogen)
2. Organic substances (glucose, amino acids, lipids, vitamins)
3. Waste products (urea, creatinine)
4. Gases (O2 and CO2)

Question 9

Where is plasma synthesized?

Answer 9

Mostly in the liver

Question 10

How many groups of plasma proteins are there? Name them.

Answer 10

3 main groups: albumins, globulins, and fibrinogen. Globulins have 3 subclasses: α, ß, γ.

Question 11

What is the function of globulin protein in plasma?

Answer 11

Three types of globulins with different functions:
α, ß globulin → transport substances; contribute most to colloid osmotic pressure.
γ globulin → antibodies (immunoglobulins).

Question 12

What components of plasma are responsible for transport?

Answer 12

Water, nutrients, albumins, alpha + beta globulins (water-insoluble substances).

Question 13

What constituents of plasma are responsible for buffering pH changes?

Answer 13

Electrolytes and plasma proteins.

Question 14

What is indicative of anemia?

Answer 14

Decrease in RBC and Hb.

Question 15

What is indicative of polycythemia?

Answer 15

Increase in RBC and Hb.

Question 16

What is indicative of leukocytosis?

Answer 16

Increase in WBC count (x > 11,000 mm-3).

Question 17

What is indicative of leukopenia?

Answer 17

Decrease in WBC count (x < 4000 mm-3).

Question 18

What is indicative of thrombocytosis?

Answer 18

Increase in platelet count.

Question 19

What is indicative of thrombocytopenia?

Answer 19

Decrease in platelet count.

Question 20

What are the 5 main types of blood vessels and their functions?

Answer 20

1. Arteries → carry blood AWAY from the heart.
2. Arterioles → resistance vessels that regulate blood flow and pressure.
3. Capillaries → sites of exchange between blood and tissues.
4. Venules → collect blood from capillaries and return it to veins.
5. Veins → carry blood TOWARDS the heart and act as blood reservoirs.

Question 21

What are the two main functions arteries are specialized for?

Answer 21

1. Serve as passageways for blood (from heart to organs) with little resistance.
2. Act as pressure reservoirs providing driving force when the heart is relaxing.

Question 22

How does blood pressure vary in systole and diastole?

Answer 22

Systole → 120 mmHg; Diastole → 80 mmHg. The difference is called pulse pressure.

Question 23

What is pulse pressure?

Answer 23

Difference between systolic and diastolic pressures.

Question 24

Describe the structure of arterioles.

Answer 24

Highly muscular walls (rich in smooth muscle), lack elastic fiber, and are major resistance vessels.

Question 25

What structures are involved in adjusting arteriolar resistance?

Answer 25

1. Vasoconstriction → narrowing of a vessel (increases pressure). 2. Vasodilation → widening of arteriole (decreases pressure but increases blood flow).

Question 26

Describe the structure and function of capillaries.

Answer 26

Narrow, water-filled gaps (pores) lie at junctions between cells; thin-walled, small radius, extensively branched. • Site of exchange between blood and tissue cells. • Permit passage of water-soluble substances. • Lipid-soluble substances readily pass.

Question 27

What type of blood vessels are referred to as capacitance vessels and why?

Answer 27

Veins; about 2/3 of blood is located in veins (64%). They serve as blood reservoirs.

Question 28

Describe the structure and functions of veins.

Answer 28

Thin-walled, large radius (offer little resistance to blood flow), serve as blood reservoir (capacitance vessels).

Question 29

What is the primary function of the lymphatic system?

Answer 29

Provides accessory route by which fluid can be returned from interstitial space to the blood via extensive network of one-way vessels.

Question 30

What is membrane potential?

Answer 30

Electrical potential across the cell membrane due to the separation of opposite charges, caused by differences in the concentration and permeability of key ions.

Question 31

What is resting membrane potential (RMP)?

Answer 31

Potential across the cell membrane at rest, typically ranging from -70 to -90 mV in excitable cells.

Question 32

Which ions are responsible for establishing resting membrane potential?

Answer 32

Sodium (Na+) and potassium (K+), along with negatively charged proteins inside the cell.

Question 33

What is the role of Na-K pump in maintaining membrane potential?

Answer 33

Actively transports 3 Na+ out and 2 K+ into the cell, maintaining the concentration gradient of these ions needed for resting membrane potential.

Question 34

What is the equilibrium potential for an ion?

Answer 34

The electrical potential that exactly balances the concentration gradient of an ion, preventing further net diffusion. For K+, it is around -94 mV and around +61 mV for Na+.

Question 35

Why is the inside of the cell negative at rest?

Answer 35

Due to K+ leakage, Na+-K+ pump pumps out 3 sodium ions and 2 potassium ions per ATP, and impermeable anions (proteins) are trapped inside.

Question 36

What is the role of Na+-K+ pump in RMP?

Answer 36

Maintains ion gradient and contributes directly slightly (about -5 mV).

Question 37

What are normal ICF and ECF concentrations of Na+ and K+?

Answer 37

Na+: 14 mM inside vs 142 mM outside; K+: 140 mM inside vs 4 mM outside.

Question 38

What are normal ICF and ECF concentrations of Na+ and K+?

Answer 38

Na+: 14mM inside vs 142mM outside K+: 140mM inside vs 4mM outside

Question 39

What is equilibrium potential?

Answer 39

Membrane potential where an ion's electrical and chemical gradients balance (no net movement). E_k = ~ -90mV E_na = ~ +60mV

Question 40

Where does RMP usually lie and why?

Answer 40

Around -90 to -70 mV, closer to E_k than E_na because the membrane is 25-30 times more permeable to K+ than Na+ at rest.

Question 41

What are excitable tissues?

Answer 41

Nerve and muscle tissues that generate rapid changes in membrane potential when excited.

Question 42

Name two types of gates ion channels.

Answer 42

Voltage-gated → open or close with voltage changes Receptor-operated / ligand-gated → open or close with chemical binding.

Question 43

Define depolarization, repolarization, and hyperpolarization.

Answer 43

Depolarization: membrane becomes LESS negative (more positive). Repolarization: return to RMP after depolarization (moves back to neg. value = -70mV). Hyperpolarization: membrane becomes more negative than RMP.

Question 44

What are the two major regulatory systems of the body?

Answer 44

- Nervous → neural communication accomplished by nerve cells. - Endocrine → hormonal communication accomplished by hormones.

Question 45

Define graded potential.

Answer 45

A localized change in membrane potential due to Na+ entry at a small membrane region.

Question 46

How does graded potential spread and how does its magnitude relate to stimulus strength?

Answer 46

Passive current flow; directly proportional → stronger the stimulus, larger the graded potential.

Question 47

Why do graded potentials die out over short distances?

Answer 47

They spread passively, meaning no voltage-gated channels are present to regenerate the signal.

Question 48

Give 3 examples of graded potentials.

Answer 48

1) Receptor potential 2) Pacemaker potential 3) End-plate potential.

Question 49

Can graded potentials be summated?

Answer 49

Yes, unlike action potentials.

Question 50

What is an action potential?

Answer 50

Brief, rapid, large (100mV) reversal of membrane potential that propagates without weakening; does not decrease in strength as it travels from site of initiation.

Question 51

What type of neural communication can the 'all-or-none' law be applied to?

Answer 51

Action potential; an action potential fires MAXIMALLY or not AT ALL.

Question 52

Define threshold potential.

Answer 52

The minimum depolarization needed to trigger an action potential.

Question 53

What aspect of action potentials can be classified as positive feedback cycles?

Answer 53

They amplify the signal through the spread of current from depolarized site along membrane, causing further depolarization of adjacent site and opening of more Na+ ion channels until threshold is reached.

Question 54

What happens during depolarization?

Answer 54

Na+ channels open; Na+ rushes in; membrane potential reverses (+30mV).

Question 55

What causes repolarization?

Answer 55

Na+ channels inactivate; K+ channels open; K+ efflux (exit).

Question 56

Why does hyperpolarization occur?

Answer 56

K+ channels remain open briefly, overshooting RMP.

Question 57

How is the gradient restored after an AP?

Answer 57

Na+ - K+ pump pumps out 3 Na+ and 2 K+ per ATP.

Question 58

What are the types of refractory periods? What is the difference between them?

Answer 58

Absolute and relative. • In absolute refractory period, no new AP can be initiated because Na+ channels are inactive. • In relative refractory period, a strong stimulus may trigger a new AP (some Na+ channels have recovered).

Question 59

How do graded and action potentials differ?

Answer 59

Graded potentials: no threshold, cause local change, die down, summate, don't obey all or none law. Action potentials: threshold, cause depolarization to threshold level, propagated, can't be summated, obey all or none law.

Question 60

A neuron’s membrane depolarizes from -70mV to -50mV but does not propagate. What is this?

Answer 60

b) Graded potential.

Question 61

A drug blocks voltage-gated Na⁺ channels. Which AP phase is blocked?

Answer 61

b) Depolarization.

Question 62

A toxin blocks voltage-gated K⁺ channels. Which phase is most affected?

Answer 62

b) Repolarization.

Question 63

What are the three main parts of a neuron?

Answer 63

Cell body, dendrites, axon.

Question 64

What part of the neuron is the input zone?

Answer 64

Dendrites and cell body.

Question 65

What happens in the cell body?

Answer 65

Houses nucleus and organelles.

Question 66

How many dendrites can a neuron have?

Answer 66

400,000 dendrites.

Question 67

What is the axon's primary role?

Answer 67

Conducts action potentials away from cell body.

Question 68

Site where action potentials are initiated?

Answer 68

Axon hillock.

Question 69

Output zone of a neuron?

Answer 69

Axon terminals.

Question 70

What cells form the myelin sheath?

Answer 70

CNS → oligodendrocytes; PNS → Schwann cells.

Question 71

Why is saltatory conduction faster than continuous conduction?

Answer 71

AP jumps between nodes of Ranvier which is faster than traveling the full length of the axon.

Question 72

What factors affect nerve conduction speed?

Answer 72

Fiber diameter (larger = faster); myelination (true = 50x faster).

Question 73

What is myelin sheath made of?

Answer 73

Lipoproteins.

Question 74

Role of myelin sheath in AP transmission?

Answer 74

Insulates axons which prevents ion leakage; interrupted by nodes of Ranvier through which ions can pass; impulse jumps from node to node = saltatory conduction; increases speed of conduction of impulses.

Question 75

Role of nodes of Ranvier?

Answer 75

Unmyelinated gaps so ions flow and are able to regenerate action potentials.

Question 76

Why is conduction of AP along unmyelinated fibers slower?

Answer 76

APs must regenerate continuously along the entire axon.

Question 77

What allows ions to flow and regenerate action potentials?

Answer 77

Gaps in the myelin sheath allow ions to flow and are able to regenerate action potentials.

Question 78

Why is conduction of action potentials along unmyelinated fibers slower?

Answer 78

Action potentials must regenerate continuously along the entire axon.

Question 79

What are the conditions for regeneration of the axon following an injury?

Answer 79

Regeneration only occurs in the PNS, where the axons are myelinated by Schwann cells. ## Footnote For CNS, the axons are myelinated by oligodendrocytes which are NOT capable of regeneration.