Physiology MCQ Notes (1-18) - Dr.Elsawy PDF

MCQ Notes on Lecture (1): “Organization of Human Body” Body fluids Constitute: 65 % i.e. 40-42 liters in an adult weighing 70 Kg. Characters of indicator or dye used: Intracellular fluid (ICF)  Not toxic.  Fluid Inside cell....

MCQ Notes on Lecture (1): “Organization of Human Body” Body fluids Constitute: 65 % i.e. 40-42 liters in an adult weighing 70 Kg. Characters of indicator or dye used: Intracellular fluid (ICF)  Not toxic.  Fluid Inside cell.  Not metabolized.  2/3 of total body fluids.  Not excreted.  25-28 liters.  Evenly distributed.  Easily measured. Extracellular fluid (ECF)  Fluid Outside cell. Measurement of total body water (TBW):  1/3 of total body fluids.  Deuterium oxide (D2O, heavy water) (most frequently used).  14-15 liters.  Tritium oxide and aminopyrine. ICF is separated from ECF by the cell membrane (semi permeable). Measurement of ECF volume: ECF is the internal environment that supplies cells with nutrients & other  Inulin (polysaccharide), mannitol and sucrose. substances. Measurement of intracellular fluid volume: Plasma :  = TBW- ECF volume.  Inside blood vessels  3 - 3.5 liters Measurement of plasma volume: Interstitial fluid  Evans blue dye  In spaces between cells  Albumin labeled with radioactive iodine.  10-12 liters Trans-cellular fluid Percentages of total body water (TBW) :  In body cavities as GIT & cerebrospinal fluid (CSF) Female Male Children Old age  1 liter 50% 60% 70% Decreased ECF: Contains sodium, chloride, & bicarbonate ions. ICF : Contains potassium , magnesium, & phosphate ions. ↑ percentage of fat → ↓ percentage of water. 195 ↑ Age → ↓ percentage of water. Each gram H2O needs 0.58 Co to evaporate → latent heat of evaporation. Homeostasis: mechanisms keeping the internal environment constant. Water input or intake: Negative feedback mechanisms: Response inhibits the stimulus e.g.  2400 ml/day. a) ↑ CO2 → hyperventilation.  Exogenous water : → 2200 ml/day. b) ↑ blood glucose → ↑ insulin  Endogenous water : → 200 ml/day. c) ↑ arterial blood pressure (ABP) →reflex vasodilatation & ↓heart rate Positive feedback mechanisms: Response increases the stimulus e.g. Water output or loss: a. Heart failure  2400 ml/day. b. Heart stroke  Urine → 1500 ml. c. Labor.  Insensible → 700ml.  Sweating →100 ml.  Feces → 100ml. Control of water input:  Thirst center (in anterior hypothalamus). Control of water loss:  By antidiuretic hormone (ADH) from posterior pituitary gland.  Its secretion is stimulated by hypertonicity and hypovolemia. 196  MCQ Notes on Lecture (2): “Functional Organization of Cell Membrane” Cell membrane: Very thin elastic semi-permeable membrane Simple Diffusion: simple movement without carrier proteins. Cell membrane thickness: 7.5nm. Facilitated diffusion With carrier proteins. Cell membrane structure: Diffusion: From: 1. Proteins: 55%.  High to low concentration of water or 2. Lipids: 42%.  Low to high concentration of solute. 3. Carbohydrates: 3%. Water: diffuses at a high rate (like a bullet) due to: Lipids: form the basic structure of the membrane.  Its small size. Phospholipids head: Soluble in water (Hydrophilic) – Polar.  Its very high kinetic energy. Phospholipids tail: Insoluble in water (Hydrophobic) – non-polar Ligand-gated or chemical-gated ion channels intrinsic (Integral) proteins: Bind to hydrophobic center of the lipid bilayer  Nonselective. Transmembrane proteins: Span the entire bilayer.  Cholinergic receptors at MEP of skeletal muscle Act as: Channels – Carriers – Pumps -Receptors Voltage-gated ion channels: Present only on one side of membrane: act as enzymes.  Selective. Extrinsic (Peripheral) proteins  Voltage-gated Na+, K+ and Ca+ channels.  Bind to hydrophilic polar heads of lipids or 𝑫.𝑨 Peripheral proteins: Flux = − (𝑪𝒊𝒏 − 𝑪𝒐𝒖𝒕) 𝑿  Bind to intracellular surface → cytoskeleton. Osmolarity  Bind to extracellular surface → glycocalyx.  Concentration in osmol/L.  Property of a solution and is independent of any membrane. Diffusion: movement of substances down its electrochemical gradient.  Plasma (290-300mosm/L) Active transport: movement of substances against its electrochemical gradient. Vesicular transport: Tonicity:  Endocytosis: Pushed inside the cell.  The ability of the particles to cause a change in the cell volume.  Exocytosis: Pushed outside the cell.  Describe osmolarity of solution relative to plasma. 208 Isotonic solution: e.g. Nacl solution 0.9 %. Secondary active transport:  Use energy stored in Na concentration gradient. Primary active transport:  As: Na+-glucose co-transport & Na+-Ca2+ exchange  Obtain its energy directly from hydrolysis of ATP. Na-glucose co-transport : The luminal membrane of intestinal mucosal and renal  As: proximal tubule cells. 1. Na+-K+ ATPase (Na+-K+ pump) Na-Ca exchange: ventricular muscles cells 2. Ca2+-ATPase 3. K+-H+-ATPase (proton pump) If solutes move in same direction: cotransport or symport Na+-K+ pump inhibited by Digitalis (Digoxin) If solutes move in opposite directions: counter-transport or antiport K+-H+-ATPase inhibited by Proton pump inhibitors (omeprazole) Endocytosis  Receptor mediated endocytosis: e.g. iron & cholesterol. In Na+-K+ pump:  Phagocytosis: bacteria and dead tissue.  Binding sites for 3 Na → on intracellular side. 4. Pinocytosis: substances in solution e.g. proteins  Binding sites for ATP → on intracellular side. Exocytosis (cell vomiting) release of synaptic transmitters and hormones.  Binding sites for 2 K → on extracellular side. 209  MCQ Notes on Lecture (3): “Intracellular Connections” Tight junctions : Staging of cell signaling by Earl Sutherland  At apical borders.  Reception – Transduction -Response.  Tie cells together and provide stability. Desmosomes Receptors is protein molecules.  Fasten the cells to one another and hold cells together. Intracellular receptors:  Hemidesmosome & focal adhesion attach cells to their basal laminas.  Steroid (cytoplasmic) hormone. Gap junctions Permit transfer of ions  Thyroid (nuclear) hormone. Tight junctions  Activated hormone-receptor complex (HRC) → can act as a transcription  Present in epithelial cells. factor which bind to specific region in DNA called hormone response element  Fused at ridges (formed of Occludin, Claudin proteins). (HRE) → genes in DNA into specific proteins.  May be : 1. Tight: impermeable to solutes and H2O as in renal distal tubule. Most water-soluble signal molecules bind to specific sites on receptor proteins 2. Leaky: permeable as in renal proximal tubule or gall bladder. that span the plasma membrane. Gap junctions:  Present in cardiac, smooth muscles & epithelial cells Ligand-Gated Ion Channels receptors:  Rare in neurons.  Ion channel-linked receptors bind a ligand and open a channel through the  Absent in skeletal muscles. membrane.  Non selective.  Consist of 6 similar subunits (connexins) on each cell. G-protein coupled receptors:  G protein (3 subunits α, β & γ subunits) Paracrine: The chemical substance to neighboring cells.  Activation of enzyme → excessive production of 2nd messengers Autocrine: The chemical substance act on the same cells. Juxtacrine: The chemical substance interact with specific receptor on juxta-posed Enzyme Linked Receptors: cells.  as tyrosine kinase receptor. 219  MCQ Notes on Lecture (4): “Functional Divisions of Nervous System” Neuron: Structural (anatomical) unit of nervous system. Spinal Cord : 31 segment Dendrites  Each spinal segment gives a pair of spinal nerves on both sides.  Multiple short processes Peripheral nervous system:  Receptive part.  Provides a communication between CNS & other tissues via nerves.  Conduct impulse towards cell body Somatic Nervous System Voluntary. Axon Autonomic Nervous System Involuntary.  Single long process. Cranial nerves may be :  Conducting part.  Purely sensory: C 1 , 2 & 8.  Conduct impulses away from cell body.  Purely motor: C 3 , 4 & 6.  Mixed: the remaining. Afferent neuron: Carries impulses from receptors to CNS All spinal nerves are mixed nerves (sensory and motor). Origin of Sympathetic NS: Efferent neuron: Carries impulses from CNS to effector organs  LHCs of all thoracic & upper 3 lumbar segments of spinal cord. Interneuron: Origin of Parasympathetic NS:  Located inside CNS.  Cranial part: 3, 7 ,9 ,10 cranial nerves.  link between neurons.  Sacral part: S2, S3, S4 (called pelvic nerve).  99% of nerve cells. Reflex action:  Involuntary (programmed) response to a stimulus.  Functional or physiological unit of the nervous system. 229  MCQ Notes on Lecture (5): “General Characters of Autonomic Nervous System” Sympathetic NS: Adrenal medulla: The only sympathetic effector organ directly innervated by  Fight or flight” preganglionic nerve fibers.  Sympathetic mass stimulation is useful.  Catabolic to energy Lateral (Para-Vertebral) ganglia: Sympathetic NS:  Short preganglionic & long postganglionic fibers.  “Rest and Digest”  For Sympathetic fibers.  Parasympathetic mass stimulation may be fatal.  Anabolic energy Collateral (pre-vertebral) ganglia: Chemical transmitter Preganglionic neuron Acetylcholine  Preganglionic is equal in length to postganglionic fibers. Chemical transmitter Postganglionic neuron Ach or noradrenaline  For Sympathetic fibers Terminal ganglia: Autonomic ganglia: Collection of cell bodies of neurons outside CNS (in PNS).  Long preganglionic & short postganglionic fibers. c. Sympathetic nervous system:  All parasympathetic fibers Ratio of preganglionic fibers to postganglionic fibers is 1:32  Generalized effects. Sympathetic  Short preganglionic & long post ganglionic. d. Parasympathetic nervous system: Parasympathetic  Long preganglionic & short postganglionic Ratio of preganglionic fibers to postganglionic fibers is 1:2  Localized effects. 236  MCQ Notes on Lecture (6): “Sympathetic Nervous System to Head & Neck” Origin of sympathetic to head & neck:  Lateral horn cells of 1st & 2nd thoracic segments of spinal cord. Relay of sympathetic to head & neck:  Superior cervical ganglia (SCG). Contraction of dilator pupillae (radial) muscle →Mydriasis (pupil dilatation) Relaxation of ciliary muscle → ↓ convexity of lens → Accommodate far vision Horner syndrome:  Group of signs which results from interruption of sympathetic to head and neck.  Occur at same side of the lesion. Causes of horner syndrome: c) Lesion in Tl and T2 segments. d) Lesion in Superior cervical ganglion. Signs of horner syndrome:  Ptosis – Miosis – Enophthalmos – Anhydrosis -Vasodilatation 246  MCQ Notes on Lecture (7): “Functions of Sympathetic Supply to Thorax, Abdomen & Pelvis” Origin of sympathetic to thorax: Relay of sympathetic to SRM:  Lateral horn cells of upper 4 or 5 thoracic segments of spinal cord.  Supplied by sympathetic preganglionic nerve fibers (with no postganglionic Relay of sympathetic to thorax: nerve fibers) which relay directly with the SRM cells (chromaffin cells).  3 cervical ganglia and upper 4 thoracic ganglia. SRM: Secretes adrenaline (80%) and noradrenalin (20%) Adrenaline acts more on metabolic actions of the body while Noradrenalin acts Origin of sympathetic to abdomen: more on blood vessels.  Lateral horn cells of T6 → T12 ( Splanchnic Nerves ) Relay of sympathetic to abdomen: Origin of sympathetic to pelvis:  Collateral (Prevertebral) Ganglia (Celiac, Superior Mesenteric & Aortico-  Lateral horn cells of L1 → L3 Renal) Relay of sympathetic to pelvis:  Inferior mesenteric & Hypo-gastric Ganglia. Effect of sympathetic on liver: ↑ Glycogenolysis → ↑glucose. Effect of sympathetic on kidney: Characters of Orbelli phenomenon: Stimulation of juxta glomerular cells → ↑ renin → VC  Better contraction Effect of sympathetic on BV: Mixed supply (VC and VD)  Delayed onset of fatigue  Early recovery after fatigue Origin of sympathetic to SRM:  LHCS of T10 & 11 segments of spinal cord. 251  MCQ Notes on Lecture (8): “Functions of Parasympathetic Supply to Head & Neck, Thorax, Abdomen & Pelvis” Occulomotor N. give motor supply to:  Ciliary muscle → accommodation to Near Vision. In near vision  parasympathetic decrease size of pupil and increases the lens power. Vagus supply atria only (doesn't supply ventricles). Pelvic nerve = nervous erigenus. The external anal and urethral sphincters are voluntary ms supplied by the somatic spinal pudendal nerve. Organs supplied by Sympathetic NS only: Organs supplied by para-sympathetic NS only: 1) Dilator pupillae muscle 1) Constrictor pupillae muscle 2) Muller's muscle. 2) Upper esophagus. 3) Cutaneous effectors 3) Glands of stomach. 4) Ventricles of heart. 5) Spleen Relation () sympathetic and parasympathetic NS may be: 6) Adrenal medulla Antagonistic One system increases the function and the 2nd decreases. Synergistic During salivary secretion: Cooperative During sexual intercourse: 257  MCQ Notes on Lecture (9): “Higher Control of ANS Functions” Spinal cord control simple autonomic functions as: Hypothalamus regulates:  Micturition, defecation & erection 1) Food intake  Vascular tone 2) Adrenaline secretion 3) Body temperature Medulla oblongata: 4) Body water  Vital centers that control: 1) Cardiovascular & respiratory functions. Stimulation of anterior nuclei of hypothalamus  ↑ parasympathetic functions 2) Gastric secretion & vomiting. Stimulation of posterior nuclei of hypothalamus  ↑ sympathetic functions Pons : Control respiration and salivary secretion Cerebral cortex can modify the autonomic functions Midbrain: 1. Cardiovascular and gastrointestinal changes : occur during psychological  Control micturition and ocular reflexes i.e. pupillary light & accommodation disturbances. reflex. 2. Voluntary control of micturition or defecation. 3. Conscious control of heart rate & respiratory rate by yoga players. Hypothalamus:  Principal higher center for autonomic nervous system  The head ganglion. 264  MCQ Notes on Lecture (10): “Functions of ANS under different Conditions” Sympathetic Tone:  Sympathetic supply to blood vessels→ decreasing its maximal diameter to its half (partial VC )  Maintains normal arterial blood pressure. Parasympathetic Tone:  In heart: Decreases SAN rhythm from 120 to 70 beat / min.  In GIT: Maintains its normal motility. Sympathectomy  Leads to immediate maximal vasodilatation. Vagotomy  Heart: increases its rate from 70 to 120 beat/min.  GIT: leads to serious prolonged GIT atony. Isolated sympathetic discharge as: Hot weather & Hand writing. Isolated parasympathetic discharge as:  Parasympathetic cardiovascular reflexes  Parasympathetic GIT reflexes 272  MCQ Notes on Lecture (11): “Cholinergic transmission & Cholinergic receptors” Synape is: Functional connection between a neuron and second cell. Anticholinesterases: Pre-synaptic: Transmits impulse towards the synapse  Neostigmine  block the action of cholinesterase. Synaptic cleft: 10-30 nm.  Prolong action of Ach. Post-synaptic: Transmits impulse away from the synapse  Used to treatment of some diseases such as myasthenia gravis. Electrical synapse Muscarinic action of Ach:  Resist fatigue  Slow onset  Both directions  Prolonged duration  Faster  Inhibited by Atropine Chemical synapse Nicotinic action of Ach:  Show fatigue  Rapid onset  One direction  Short duration  Slower  Inhibited by Ganglion and neuromuscular blockers Acetylcholine: Muscarinic receptors subtypes:  Sympathetic Post-ganglionic fibers to Sweat glands & Skeletal ms BV.  M1 → Brain & autonomic ganglia  M2 → Heart Synthesis of Acetylcholine by: choline – acetyl transferase (CAT) enzyme  M3 → Smooth muscles & secretory glands. Acetyl co-A + choline → acetylcholine + co-A.  M4 → Pancreas Each vesicle contains > one thousand Ach molecules (5000-10,000)  M5 → Under investigation Acetyl Choline binds to receptors on postsynaptic membrane : Muscarinic receptors stimulated by: Muscarine  Ligand-gated ion channels: Muscarinic receptors inhibited by: Atropine a) Na and Ca influx → Depolarization (stimulation ) Nicotinic receptors subtypes: b) K efflux and Cl influx → Hyper-polarization (inhibition).  Neural nicotinic (Nn)  G-protein coupled receptors: activates membrane enzymes such as adenyl a) Autonomic ganglia cyclase → cyclic AMP b) Adrenal medulla Hydrolysis of Acetylcholine by choline - estrase enzyme.  Muscle nicotinic (Nm): Motor end plate Acetylcholine → acetic acid + choline Nicotinic receptors stimulated by: Nicotine (small dose) Cholinesterases: Keep action of acetylcholine localized Nicotinic receptors inhibited by: Nicotine (Large dose) 282  MCQ Notes on Lecture (12): “Adrenergic transmission & Adrenergic receptors” Noradrenaline is chemical transmitter of sympathetic nervous system. Catecholamines include: adrenaline & noradrenaline & dopamine. Dopamine is present in certain parts of brain ( basal ganglia ) with much higher concentration than noradrenaline. In adrenal medulla: Adrenaline and Noradrenaline are stored in the form of granules in chromaffin cells. Neuronal uptake  Accounts for removal of 85 %  Either stored or destroyed by M. A.O Extra neuronal uptake  Account for removal of 15%  Destroyed by C.O.M.T. Mono-amino-oxidase (MOA)  Present in mitochondria of adrenergic fibers , liver and kidney. COMT  Present in all tissues especially kidney & brain β3 Adrenergic receptors : present in adipose tissue → lipolysis Alpha 1 adrenergic receptors:  Activation of protein G→ ↑Intracellular IP3 & ↑intracellular Ca  Ca & IP3 act as second messenger Alpha 2 & 3 adrenergic receptors: → ↑ C-AMP 289  MCQ Notes on Lecture (13): “Equilibrium Potential & Nernst equation” Nerve trunk Composed of a larger number of nerve fibers. Function of Na – K Pump: Excitability is : The ability of nerve fibers to respond to stimuli  Electrogenic Pump. Conductivity is : The ability of nerve fibers to conduct nerve impulse  Pumps 3 Na+ outside the cells and 2 K+ inside the cell. Value of RMP in: 90-95 % of RMP :  Nerves: -70mV  Passive process due to diffusion of ions  Skeletal ms: -90mV 5-10% of RMP :  Cardiac ms: -90mV  Active process due to Na-K pump.  Smooth ms: -60mV Leak or passive channels: Responsible for RMP. Graded potential : Voltage gated channels: Responsible for Action Potential (AP)  Local change. Ligand gated channels: Act as receptors  By ineffective (Sub-miniml )stimulus. K ions:  Duration & magnitude are variable according to stimulus.  Inside > outside 30-40 times  K+ ion is the main cause of RMP. Receptor potential Na ions:  In the beginning of the sensory nerves.  Outside > inside 10 times Synaptic potential  Na ions pass through passive Na channels with difficulty  In synapses inside CNS. Local excitatory state Equilibrium potential:  In cell bodies of neuron.  Electrical potential caused by charge separation due to diffusion of ions. Nernst equation (Nernst Potential): 61 𝐂𝐢𝐧 ± log 𝑧 𝐂𝐨𝐮𝐭 122  MCQ Notes on Lecture (14): “Ionic basis, Propagation & recording of Action Potentials” Depolarization Latent period affected by :  Due to Na+ influx.  Distance between stimulus and nerve fiber.  Through voltage gated Na+ channels  Velocity of nerve fibers. Spike potential: Repolarization  Large wave (105 mV from – 70 to +35 mV).  Due to K+ efflux.  Short duration (0.5 -1msec).  Through voltage gated K+ channels Negative after potential:  Short duration (4 m sec) Stimulus (cathode): adds negative charges to outer surface → passive  The membrane is partially depolarized. depolarization  Due to slow K+ efflux. At – 63 mV: Some voltage gated Na+ channels open → active depolarization Positive after potential: At – 55 mV (firing or threshold level):  Long duration (40 m sec)  All voltage gated Na+ channels open → reversal in polarity.  The membrane is hyperpolarized.  Voltage-activated K+ channels open but after a slight delay time.  Due to continuous excess K+ efflux. K ions continue to diffuse to outside due to delayed closure of its channels Biophasic Action Potential : By two microelectrode leading to hyperpolarization.  Placed on the outer surface of nerve fibers Monophasic Action Potential : By two microelectrode  One electrode (recording) into the nerve fibers (recording) Primary hypokalemic periodic paralysis:  Inherited disorder.  2nd electrode (reference) outside away from stimulated nerve fibers  Characterized by: Decreased serum K & Recurrent attacks of ms weakness Monophasic Action Potential : record  Latent period & Spike potential & After potential 130  MCQ Notes on Lecture (15): “Changes in the nerve fibers during Action Potentials & Types of Nerve Fibers” Continuous (Sweeping) conduction: Type C fibers:  Unmyelinated nerve (C).  Speed: 0.5-2 m/sec  Slow (0.5 – 2 m / sec)  Sensitive to: Local anesthetics  More energy consumption Saltatory ( jumping ) conduction: During rest: Nerve fiber spends energy to maintain RMP.  Myelinated nerve (A&B) During passage of nerve impulse: Metabolic reactions are ↑↑ to about double  Fast (Up to 120 m/sec) the resting state.  Less (1% of continuous) Thermal changes Appears in two phases:  Initial heat Due to generation and propagation of nerve impulse. ↑ diameter → ↓ internal resistance →↑ conduction velocity  Delayed heat 30 times the initial heat & remains for 30 minutes & Due to ↑ myelin sheath thickness → ↑ membrane resistance to current → increase the metabolic reactions needed to reform the ATP utilized during the action conduction velocity potential. If conduction in the normal direction → orthodromic conduction Nerve block: Failure of initiation (excitability) and propagation (conductivity) of If conduction in the opposite direction → antidromic conduction nerve impulses. Type A fibers: Multiple sclerosis:  Speed: 10-120 m/sec  Autoimmune disease  Sensitive to: Prolonged deep pressure  Women : men = 2:1. Type B fibers:  20 and 50Y.  Speed: 3-15 m/sec  Muscle weakness, fatigue, diminished coordination  Sensitive to: O2 lack (Hypoxia)  Treated by Steroids 137  MCQ Notes on Lecture (16): “Mechanism of Synaptic Transmission & Its Properties” Electrical synapse: Present in hippocampus & retina. Axo-dendritic synapse is the most common type. Impulses are conducted only in one direction from the presynaptic neuron to the post-synaptic neuron. The minimum time for synaptic delay is about 0.5 msec. Synaptic fatigue: Protective mechanism against excess neuronal activity Marked hypoxia for short period (just few seconds) → loss of excitability of neurons. Alkalosis: ↑ excitability. Acidosis: ↓ excitability. Caffeine & theophylline & Strychnine: Increase synapse Anesthetics and hypnotics: Decrease synapse 144  MCQ Notes on Lecture (17): “Physics of Blood flow, Types of Blood flow & Vascular compliance” Overall blood flow in circulation at rest is 5000 ml/minute = cardiac output. Laminar streamline blood flow : Blood flow is directly proportional to perfusion pressure Flow α Δ P  Streamline (laminar) 𝟏  Thin layer in contact of wall not move Blood flow is inversely related to resistance Flow α 𝐑  Velocity is the greatest in centre of stream Poiseuille equation  Silent 𝟖𝛈𝐋 𝛈𝐋 R= Rα  Reynold number < 2000 𝛑𝐫𝟒 𝐫𝟒 Turbelant crosswise blood flow : Resistance is inversely proportional to the 4th power of the radius.  Eddy currents Rα 𝟏  Murmur 𝐫𝟒  Reynold number > 3000 If radius is reduced to 1/2 , the flow will ↓ to be 1/16 of its Previous value.  Occurs when increased velocity of blood , decrease blood viscosity , change in The arteriolar diameter is controlled by: Sympathetic NS & drugs or hormones vessel diameter and chemicals. Resistance is directly proportional to the viscosity (R α η) Reynold number determine probability of turbulence ↑ viscosity of blood →↑ R and ↓ blood flow 𝐏𝐃𝐕 Re = ↓ viscosity of blood →↓ R and ↑ blood flow 𝛈 ↑ plasma proteins as immunoglobulins → ↑ blood viscosity → ↑ resistance. Resistance is directly proportional to length of blood vessel (L) through which When Re < 2000 → flow is not turbulent blood flow takes place. R α L When Re > 3000 → flow is turbulent Measuring of blood flow : Turbulence can occurs when: 1) Electromagnetic flowmeter. Direct  Increase velocity. 2) Ultrasonic flow meter. methods  Decreased blood viscosity. 3) Venous occlusion plethysmography.  By Fick's principle: Indirect methods Flow (F) = Q/ (Ax-Vx) 151  MCQ Notes on Lecture (18): “The Interstitium and Interstitial fluids” Interstitium: The Space between cells & 1/6 of body tissue. Interstitial fluid hydrostatic pressure (Pi) : Interstitial fluid: Gel like fluid that entrapped in interstitium.  -3 mmHg  negative interstitial fluid pressure.  +6 mmHg in kidney. Starling principle: The rate & direction of fluid movement is proportional to  +4 mmHg in brain. algabric sum of hydrostatic and osmotic forces. Plasma colloid osmotic = oncotic pressure (πc) : 28 mmHg 20 liters of fluid are filtered every day at arterial ends of capillaries.  9 mmHg by plasma proteins  18 liters of them are reabsorbed back at venous ends.  9 by accompanying Na ions due to (Donnan effect).  2 liters are drained by lymphatic system. Interstitial fluid colloid osmotic pressure (πi) :  Average protein conc. of interstitial fluid is about 3 gm/100 ml. Plasma colloid osmotic = oncotic pressure (πc)  Colloid osmotic pressure of about 8 mmHg.  The main absorbing force. 13 mmHg filtration pressure occurs at arterial ends of capillaries. Capillary hydrostatic pressure (Pc) : 7 mmHg is the reabsorbing pressure at venous ends of capillaries.  30 mmHg in arterial end 0.3 mmHg represents the slight imbalance of forces that causes slightly more  10 mmHg in venous end. filtration of fluid into the interstitial spaces than reabsorption The functional mean capillary pressure: 17.3 mmHg 157