Đang chuẩn bị liên kết để tải về tài liệu:
Applied Surgical Physiology Vivas - part 4

Tỷ lệ lưu lượng máu não là gì? 50 ml cho mỗi 100 g của mô não. Nó chiếm 15% CO, hoặc khoảng 750 mlmin 1. 7. Làm thế nào để tỷ lệ này của dòng chảy khác nhau với những áp lực động mạch? Tỷ lệ dòng chảy vẫn cơ bản ổn định do tự điều địa phương của dòng chảy. | APPLIED SURGICAL PHYSIOLOGY VIVAS 6. What is the rate of cerebral blood flow 50 ml per 100 g of brain tissue. It accounts for 15 of the CO or about 750mlmin 1. 7. How does this rate of flow vary with the arterial pressure The rate of flow remains essentially stable owing to local autoregulation of flow. This is a characteristic feature of some specialised vascular beds such as the renal system. 8. What is the basic mechanism of autoregulation There are two principle reasons Myogenic response an increase in the arteriolar wall tension brought on by an increase in the arterial pressure stimulates contraction of the mural smooth muscle cells. The resulting vasoconstriction stabilises the flow in the face of these pressure changes Vasodilator washout if flow is suddenly and momentarily increased by a sudden rise in the driving pressure locally-produced vasodilating mediators are washed out of the vessel leading to vasoconstriction and a return of the flow to the steady state 9. What are the main factors that govern the cerebral blood flow PaCO2 hypercarbia increases the cerebral flow through an increase of the H . The reverse occurs with hypocarbia PaO2 hypoxia produces cerebral vasodilatation increasing the flow. This influence is less important than the above Sympathetic stimulation causes some vasoconstriction but this is the least important influence C CEREBROSPINAL FLUID AND CEREBRAL BLOOD FLOW 45 APPLIED SURGICAL PHYSIOLOGY VIVAS C 10. What is meant by the cerebral perfusion pressure This is defined as the difference between the mean arterial pressure and the intracranial pressure. It must remain above around 70 mmHg for adequate cerebral perfusion. CEREBROSPINAL FLUID AND CEREBRAL BLOOD FLOW 46 APPLIED SURGICAL PHYSIOLOGY VIVAS COLON 1. What are the major functions of the colon Absorption of water the most important Absorption of minerals predominantly sodium. There is however net secretion of potassium and bicarbonate Expulsion of faeces Indirect role bacterial