Homeostasis and Haemodynamics PDF

Homeostasis and Haemodynamics Learning Objectives blood loss if a reduce Define Define homeostasis ressed wall is...

Homeostasis and Haemodynamics Learning Objectives blood loss if a reduce Define Define homeostasis ressed wall is damaged ① Explain 2 3and Explain the factors that affect arterial blood flow [blood pressure3 ② Q ② Distinguish between neural and hormonal regulation of Distinguish blood pressure  things in normal values and normal limits Keeping ① ⑳ State of steady#internal, physical and chemical conditions maintained by living systems for - · optimal functioning for the organism ① ⑳ Pre-set normal limits: body temperature, fluid ③ ab for the balance, pH, ions (potassium, sodium and PSC En order ⑤ body to do this there calcium) and blood sugar levels Homeostasis non ① Regulator mechanism involves: ① Receptor Temp – thermoreceptor, mechanoreceptor af ⑭ Control centre –- respiratory centre, renin- i i sis wrong - Picks angiotensin system one thing - S ③ Effector – target acted on to return to normal state.  Blood flow – volume of blood that flows > - through any given tissue in a given time mL/min E Blood flow to individual tissues dependant on requirements - S15 Blood flow Speed (velocity) of blood flow is inversely proportional to the cross sectional area –G flow " * - wi is slow when I extensive ass branching3– capillaries – useful for diffusion to take place A Haemodynamics – factors affecting blood flow  Co = Heart Rate X Stroke DHRD volume (SU] Total blood flow = Cardiac output (CO) – 2volume of bloodIthat circulatesI through systemic (pulmonary) blood vessels I per minute 3 Eardiac OutPut] CO = Heart rate (HR) x stroke volume (SV) Haemodynamics (volume of blood pumpedC with one contraction out of the ventricle - Factors affecting CO distribution dependant on 2 factors Blood flow I Pressure difference that drives blood through - the vessel - * 2 Resistance to blood flow  3 components ①S Size of the lumen – small lumen → ↑ resistance → ↓ blood flow norther Blood viscosity - ↑ viscosity → ↑ resistance → ↓ Vascular blood flow resistance For example: dehydration or increased red blood cells ⑤ Total blood vessel length – resistance to blood flow is proportional to the length of the vessel – longer the blood vessel the more resistance  Systemic vascular resistance = total peripheral resistance It is the resistance to blood flow offered via the systemic vessels Smaller vessels – arterioles, venules and capillaries - - offer high resistance – arterioles are key in controlling systemic vascular * resistance C Larger vessels such as veins offer lower - resistance to blood – act as reservoirs for blood and need assistance to move blood back to the heart  Pressure exerted on the blood vessel wall – pumping action of the heart when ventricles E contract Highest in Aorta, systolic 120mmHG/diastolic 80mmHg Blood Mean arterial pressure (MAP) average pressure pressure flowing through the arteries S MAP = CO x systemic vascular resistance I CHR) X(V) Regulation of BP is vital for life ① ② Constant automatic (neural) and hormonal control En order to control blood pressure there is  Autonomic Cardiovascular centre (CVC) in medulla oblongata Sympathetic nervous system (SNS) Blood stimulatory, Parasympathetic nervous system (PNS) inhibitory – impact on heart rate pressure Vasomotor centre (VC) in the medulla regulation oblongata – impacts on constriction or dilation of blood vessels Hormonal Renin-angiotensin aldosterone system  Baroreceptors in the arch of the aorta and in the carotid sinus – pick - up the stretch on vessel walls Autonomic control of blood ↓ blood pressure ↓ stretch on blood vessel walls ↓ signals (via the pressure glossopharyngeal and vagus nerves) to the CVC → ↓ inhibitory PNS to SA node → ↑HR which → ↑ - CO and hence BP  Renin-angiotensin aldosterone system Hormonal ↑ BP → blood flow to kidneys → cells in the control kidney secrete renin into the blood Renin splits angiotensin, a large protein, into angiotensin I Angiotensin 1, which is inactive, is split into pieces by angiotensin-converting enzyme (ACE) into angiotensin II, a hormone which is active Angiotensin II causes the muscular walls of small arteries (arterioles to constrict, increasing blood pressure by increasing systemic vascular resistance  Angiotensin II also triggers the release of a hormone aldosterone Hormonal from the adrenal glands and vasopressin (antiduretic hormone) control from the pituitary gland (continued) Aldosterone and vasopressin cause the kidneys to retain sodium. The increased sodium causes water to be retained, thus increasing blood volume and blood pressure