Circulatory System Flashcards
1
Q
Describe the function of blood
A
- Transport: O2, CO2, nutrients, waste (kidneys, lungs, sweat glands), enzymes, heat energy
- Regulation: pH (bicarbonates, AA and Hb), water content of cells (dissolved Na ions)
- Protection: Against fluid loss (clotting) and toxins and foreign microbes (WBC and T-cells)
2
Q
Describe physical characteristics of blood
A
- 4.5-5.5x more viscous than water
- pH range 7.35-7.45 (7 during exercise)
- Sodium concentration 140mM (0.85-0.9%, doesn’t vary)
- 8% of body weight (can rapidly change / readjust)
- Plasma (55%) and blood cells (45%)
- Hematocrit (Hct), % of blood that is composed of cells, males (42%) and females (38%)
3
Q
What are components of plasma
A
- 91% water (dissolves other materials, fluid medium)
- 9% plasma proteins (serum albumin 60%, serum globulin 36% and fibrinogen 4%), minerals, ions and hormones
4
Q
What are RBC
A
- Structure: Contain haemoglobin (Hb), biconcave discs, pliable, change shape to squeeze through BV
- Function: Carry oxygen from the lungs to tissues in the body
5
Q
What is haemoglobin
A
- Protein core of globin and 4 iron containing groups (heme)
- Oxygen bind to heme
- C02 carried by globin
- Concentration: Males (16g/dL), females (14g/dL), children (12g/dL) and birth (17g/dL)
- Oxygen: 1g Hb combines with 1.34ml of O2, males carry 21.4ml O2/dL blood and females carry 18.8ml O2/dL blood
- Buffer: Stabilises pH / acidity of blood, 50% of buffering capacity, carbonic anhydrase, facilitates reaction between CO2 and H2O causing production of H and HCO3
- Carry more CO2 in blood stream through bicarbonate
6
Q
What is erythropoiesis and its regulation
A
- Production of RBCs
- 0-5 yrs (all bones), 5-20yrs (long), >20yrs (marrow of vertebrae, sternum, ribs, ilia), marrow becomes less productive as age increases
- Stress (exercise, blood loss, trauma) can stimulate marrow to produce RBCs
- Increases in response to ↓O2 PP and quantity of O2 transported to tissues (hypoxia)
7
Q
What is polycythaemia
A
- Increase in proportion of RBCs, more viscous, higher BP, increased stress on heart
- Absolute (more cells in body) or relative (certain circumstances)
- Secondary (hypoxic) and physiologic (altitude)
8
Q
What is tissue hypoxia and when does it occur
A
- Hypoxia: Deficiency in the amount of oxygen reaching the tissues, results due to
- High Altitude: Less oxygen available, stimulates increase in RBC
- Cardiac Failure: Less blood to tissues and kidney, thus low RBC stimulates increase in production
- Haemorrhage: Increase blood loss thus low RBC stimulates increase in production
- Anaemia: Low RBC conc., stimulates production
- Exercise: High intensity stimulates production
9
Q
Describe the heart
A
- Heart Wall: Epicardium, myocardium and endocardium
- Myocardium: Responsible for contraction, receives its blood supply via right and left coronary arteries
- Highly aerobic, many mitochondria, extensive capillary network, striated like skeletal muscle
- Heart Rate: Controlled by neural, hormonal, intrinsic factors
- Two pumps in one, the right side pumps blood through pulmonary circulation, while the left side delivers blood to the systemic circulation
10
Q
How is the heart neurally controlled
A
- Most dominant control mechanism
- CV regulatory centre in the medulla
- Signals delivered via ANS (SNS and PNS)
11
Q
Sympathetic / parasympathetic control of heart
A
- Sympathetic: Cardiac accelerator nerves secrete norepinephrine and some epinephrine to increase HR
- Parasympathetic: Vagus nerve secrete acetylcholine to slow heart
- Most increase in HR during exercise is due to inhibition of vagal activity
- Increase is mainly a decrease in PNS activation not an increase in SNS
12
Q
Central command control of heart
A
- Voluntary movement, motor cortex, impulse to cardiac regulatory centre in medulla
- Signals pass through medulla due to emotional factors / activation of motor cortex
- Vagus nerve inhibited (PNS) cardiac accelerator nerve is excited (SNS)
- HR increases and feedback to medulla is regulated by higher brain centres and receptors
- Neural coordination allows for rapid adjustment of heart and blood vessels to optimise tissue perfusion and maintain BP
13
Q
How is the heart intrinsically regulated
A
- Intrinsic regulating system composed of specialised myocardial cells that generate and distributes the electrical impulse which stimulates contraction of cardiac muscle fibres.
- Sinoatrial Node: ‘Pacemaker’ of heart, located at top right atrium, base of the superior vena cava,
- Atrioventricular: Located in the floor of the right atrium
14
Q
How does electrical conduction intrinsically control the heart
A
- SA node initiates contraction, impulse spreads out of the atria causing contraction
- Depolarisation spreads to AV node, AV bundle (Bundle of His), left and right bundle branches, Purkinje fibres and up and around the ventricles causing contraction
- Contraction begins at apex and flows upwards forcing blood out of ventricles from apex to top
- SA node increases rate due to being stretched as more blood returns to the heart during rhythmic exercise
15
Q
What is the cardiac cycle / heart sounds
A
- Systole: Contraction phase, ejection of blood, pressure in ventricles rises, blood ejected in pulmonary and systemic circulation
- Semilunar valves open when ventricular pressure is bigger than aortic pressure
- Diastole: Relaxation phase, filling with blood, pressure in ventricles is low, filling with blood from atria
- AV valves open when ventricular pressure is smaller than atrial pressure
- First (closing of AV valves) and second (closing of aortic and pulmonary valves)
16
Q
What is arterial blood pressure
A
- Arterial Pressure: Expressed as systolic / diastolic
- Systolic Pressure (SBP): Pressure generated during ventricular contraction, impacted by HR
- Diastolic Pressure (DBP): Pressure in the arteries during cardiac relaxation, not impacted by HR
- MAP: Average BP during cardiac output, MAP = DBP + (0.33 x pulse pressure), for 120 / 80 MAP = 93
- Pulse Pressure: Difference between systolic and diastolic (SBP - DBP)
17
Q
How does HR, SV and Q respond to incremental exercise
A
- HR: Steady increase
- SV: Steady increase, plateau at 40% VO2max
- Q: Steady increase, slower incline at 40% VO2max
18
Q
How does exercise influence venous return
A
- Increases
- Vasoconstriction: Increases venous return by reducing volume capacity of veins to store blood, occurs via a reflex sympathetic constriction of smooth muscle in veins draining muscle
- Muscle Pump: As muscles contract they compress veins and push blood back towards the heart
- Respiratory Pump: The rhythmic pattern of breathing, mechanical pump
19
Q
What is albumin, globulin and fibrinogen
A
- Albumins: Small, most abundant, maintain osmotic pressure
- Globulin: Large, carriers, transporting hydrophobic materials, also antibodies
- Fibrinogen: Large protein, not abundant, 4% of plasma proteins by weight, important in clotting
20
Q
What is steady state exercise
A
- Balance between energy required by working muscles and the rate of oxygen and delivery for ATP production
- Exercise that has a stable / unchanging VO2 (Q is maintained, SV decreases and HR increases to maintain Q)
- HR less than 4 bpm difference in final minutes of training
21
Q
What is stroke volume and how is it regulated
A
- Volume ejected per beat (by left ventricle)
- SV = EDV – ESV
- EDV = End Diastolic Volume
- ESV= End Systolic Volume
- Regulated by EDV, aortic blood pressure, and strength of ventricular contraction
22
Q
What is cardiac output (Q)
A
- Volume ejected by the heart per minute
- HR x SV (ml/min or L/min)
- Q̇ = VO2 (ml.min-1) / a - vO2 (ml.dL-1) x 100
23
Q
What is VO2 and the fick equation
A
- The volume of oxygen consumed by the cells
- The volume of oxygen consumed by the cells is equal to the cardiac output multiplied by the amount of oxygen extracted from blood
- VO2 = Q̇(CaO2 - CvO2)
- VO2 = (HR x SV)(CaO2 - CvO2)
24
Q
How does heart rate change over time (age)
A
- High at birth, 140 bpm at rest, SV = 3-4 ml, Q̇ = 0.5 L / min
- Lower at childhood, 70-80 bpm at rest, SV = 40 ml, Q̇ = 3.2 L / min
- Decreases slightly at adolescence / adulthood, 74 bpm, SV = 70 ml, Q̇ = 5 L / min
- Resting HR rises again as you get older, maximal HR decreases (220 - age)
25
How does Q increase with exercise
- Require increased BF
- Increased BF can result from redistribution from non-working muscles and organs
- Increased Q̇ (increased output = increased flow to muscles)
- An increase in diastolic volume causes and increase in SV (starlings law)
- Time in diastole significantly decreased
26
What is VO2max
- Maximal amount of O2 that the body can utilise, ‘gold’ standard for aerobic fitness
27
How does blood pressure respond to exercise
- Blood pressure during exercise changes due to increased Q, blood viscosity (h sweating = iPV) and geometry of vessel (length and radius affects resistance)
- Resistance to flow increases markedly as the radius decreases
28
How does Q, HR and SV change with consistent training
- Q: Increases due to an increase in SV, maximally utilising the total volume of the left ventricle to eject blood to the muscles, aerobic adaptation
- HR: Lower heart rate
- SV: Higher stroke volume
29
What is the central command theory of cardiovascular control during exercise
- The initial signal to “drive” the cardiovascular system at the beginning of exercise comes from higher brain centres
30
What is blood pressure and changes from rest to exercise
- Cardiac output (HR and SV)
- Peripheral resistance
- Exercise increases BF to muscles creating greater resistance pressure within arteries (increases SBP)
- Vasodilation of arterioles decrease arterial resistance (slight raise / no effect on DBP)
31
What is an electrocardiogram
- Record of electrical impulses that stimulate heart to contract
- P Wave: Atrial depolarisation
- QRS Complex: Ventricles depolarise, occurs quicker indicated by large peak, atrial repolarisation
- T: Ventricular repolarisation
32
Describe locations of ECG lead placement
- VI: Fourth intercostal space, right of sternal border
- V2: Fourth intercostal space, left of sternal border
- V3: Midway between V2 and V4
- V4: Mid-clavicular line over 5th intercostal space (under nipple)
- V5: Anterior axillary line, same level as V4, between 4-6
- V6: Mid axillary line (armpit), same level as V4-5
- RA / LA: Clavicular
- RL / LL: Bony prominence around hip
