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)
