Physiology - circulating body fluids Flashcards
(32 cards)
Discuss the central Neural control affecting arteriolar tone
Vasomotor centre in medulla constrict / dilatation
Influence by Baroreceptors
NA vasoconstrictor fibres from spinal cord to smooth muscles
Peripheral barroreceptor
Peripheral chemoreceptors
Discuss the hormones that influence arteriolar tone
Adrenaline Noradrenaline AT II Vasopressin Bradykinin Histamine >> basophils and mast cells
Describe the auto regulation of tissue blood flow
Flow remains constant despite moderate changes in perfusion pressure through alterations in vascular resistance
How does auto regulation apply to cerebral blood flow
Constant blood flow over pressure range of 65-140 mmHg
Sympathetic stimulation prolongs the plateau
What are the proposed mechanisms involved in auto regulation
Myogenic
Metabolic
What local factors can cause vasoconstriction or vasodilation
.
What are Baroreceptors and where are they located
6
What is the MOA of the Baroreceptors
Inhib stimulus to tractus solitarius medulla to decrease sympathetic discharge and increase cabal tone on the heart.
What is the action of Baroreceptors in the setting of acute blood loss
Decrease blood volume and venous return results in ….
Results in…
What is the maximum firing of Barorreceptors and what are they most sensitive to?
Pulse pressure rather than constant pressure.
150mmHg at carotids
What are the effects of Baroreceptors
What is the role of Baroreceptors
Inhibit tonic sympathetic tone & once. Vaal tone to ….
Allows rapid adjustments in BP in response to abrupt changes in posture blood volume, cardiac output, or peripheral resistance
Describe the factors that control blood flow to the myocardin
Local factors to control radius
Neurogenic
Pressure differences
How is BP maintained in the setting of cute blood loss (time frames)
1 Seconds/ minutes
2 mins to hours
3 longer term
What are the factors influence the vasomotor centre in the brain
1 Direct stimulation (co2 & hypoxia)
2 Exciting inputs (hypothalamus, pain pathways and chemoreceptors)
3 inhibitory inputs (from cortex via hypothalamus lungs and Baroreceptors)
Describe the factors affecting cardiac output
😜
What are the physiological responses to moderate blood loss
1 decrease Venus return, stimulation of Baroreceptors including catecholamine release
2 decrease renal bloodflow and activation of RAS
3 fluid shifts, hepatic synthesis of proteins and increase in red blood cell production
Describe what happens to Cardiac out during exercise
.
What are the local mechanisms to maintain a high blood flow in exercising muscle
4
What factors affect cerebral blood flow
5
Describe auto regulation of cerebral bloodflow
it is the process by which cerebral bloodflow is maintained at a constant level despite variation in perfusion pressure.
Average cerebral bloodflow is 54mls/ 100g/minute between MAP of 65 to 140mmHg
What is the Munro Kelly doctrine
1 The brain tissue and spinal fluid are essentially incompressible
2 The volume of blood spinal fluid and brain tissue must be relatively constant
3 So when ICP rises, the cerebral blood vessels are compressed resulting in reduced cerebral bloodflow
What is cushing’s reflex
1 Increased ICP >33mmHg decreases CBF to cause is harms
2 causes increased stimulation of Baroreceptors and vagal outflow
3 bradycardia and slowing of respiration
Describe coronary artery or blood flow during the cardiac cycle
Flow in diastolic
LV subendocardium most vulnerable
RCA folw through systolic and diastolic due to lower RV pressures
What factors decrease coronary artery bloodflow
1 physiologic
2 pathological
