Blood pressure auto regulation Flashcards
Why does blood flow through the body?
-transport (nutrients, oxygen, energy to muscles, and removing substances)
-environmental homeostasis (maintain homeostasis by transport)
-communication (creates link between brain and body and other organs)
what is blood pressure?
the force exerted by blood on the walls of the vessels
How does blood flow through the body?
-By blood pressure:
when heart contracts and relaxes blood pressure increases and decreases (120 when contracting, 80 when relaxing):
Describe the pressure gradient as blood flows thru the vascular system?
pressure goes from high to low (flow down a pressure gradient) and decreases as we move thru the vascular system
what are the 3 types of pressure that are involved with pulse pressure?
-systolic pressure
-diastolic pressure
-mean arterial pressure
what is systolic pressure?
pressure during heart contraction
what is diastolic pressure?
pressure during heart relaxation
what is mean arterial pressure and what is the formula?
-it creates driving force for blood flow
Mean arterial pressure=⅓(SBP-DBP)+ DBP
How is resistance created and what is the formula for it?
-created by Friction between arteries and blood
Resistance = length of vessel x fluid viscosity/ vessel radius
what 3 factors can affect resistance?
viscosity, tube length and tube diameter
how can viscosity affect resistance?
-Its the thickness or stickiness of fluid to flow
-high viscosity means increased resistance and decreased flow
- low viscosity means low resistance and increased flow
-Increases a little with exercise due to dehydration
how can tube length affect resistance?
longer the tube the more resistance (greater drop in pressure due to friction)
(in humans blood pressure increased due to obesity)
how can tube diameter affect resistance?
-determined by vasoconstriction/vasodilation
-smaller diameter= increased friction and decreased flow
What is blood flow and what is the formula for it?
-The volume of blood moving thru a particular site over a given time period
-Flow= difference in blood pressure/ peripheral resistance
how does blood pressure and peripheral resistance impact blood flow?
-higher pressure diff, increased flow, lower pressure diff, decreased flow
-increased PR, decreased flow, decreased PR, increased flow
what is the formula to calculate blood pressure?
Blood pressure= cardiac output (l per minute) x total peripheral resistance
Name some clinical issues that affect blood pressure?
Caused by blood volume
-Major haemorrhage= decrease BP (low blood volume)
-Salt/ fluid= increase BP (if increased intake of fluids)
=decrease BP (if loss of salt/ fluids)
-polycythaemia= increase blood viscosity
-RBC anaemia= decrease blood viscosity
what is the difference between hypotension and hypertension?
-Hypotension- low blood pressure
-Hypertension-high blood pressure (140/90)
What are the 3 components of blood pressure auto regulation?
-local
-neural
-hormonal (slower process)
what is local BP auto regulation?
Local automatic adjustment of blood flow in a given region of the body
Describe what happens during local BP auto regulation?
-Receptors detect levels of O2/ CO2 in the blood then vessels respond by carrying out either Vasoconstriction & Vasodilation
Describe the process of vasoconstriction in local BP regulation and what causes it?
-Caused by increased O2 and low CO2, increased endothelin and increased sympathetic stimulation vasopressin or cold
-Increased contraction of circular smooth muscle in the arteriolar wall, leading to increased resistance and decreased flow through vessel
Describe the process of vasodilation in local BP regulation and what causes it?
-Caused by decreased o2, increased CO2, increased nitric oxide and decreased sympathetic stimulation, histamine release or heat
-Decreased contraction of circular smooth muscles in the arteriolar wall, leads to decreased resistance and increased flow through vessel
Describe the steps within a negative feedback loop?
1-Variable in homeostasis
2-If variable increases/ decreases it becomes unbalanced (change in variable)
3-Change in variable is detected by receptor
4-Input: information is sent along afferent pathway to control centre
5-Output: information is sent along efferent pathway to effector
6-Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis
-Neural BP auto regulation is an example of negative feedback loop
What are the 2 receptors involved with neural BP auto regulation?
Baroreceptors and Chemoreceptors
where are baroreceptors located and what is their role within neaural BP auto regulation?
-Baroreceptors are sensors located in aorta and carotid arteries
-Baroreceptors identify pressure by noticing changes in stretch (more stretch on arteries, higher the pressure)
Describe how baroreceptors carry out negative feedback loop within neural BP autoregulation?
1-If reduced pressure and reduced stretch is detected baroreceptors identify this and notify the brain (afferent signals are sent to the medulla)
2-medulla processes information then coordinates a response to change in pressure
(Response can either be parasympathetic (when there is too much pressure-responds by decreasing heart rate/ stroke volume or vasoconstriction of arteries) or sympathetic (when there is too little pressure- responds by increasing heart rate/ stroke volume or vasodilation of arteries)
where are chemoreceptors located and what is their role within neural BP auto regulation?
-they identify changes in blood composition (oxygen, CO2, blood pH or hydrogen ions)
- if there’s a change in CO2 pressure affect central chemoreceptor (located in medulla oblongata)
-if there’s a change in O2 or blood ph affect peripheral chemoreceptors (aortic and carotid bodies)
Describe how chemoreceptors carry out negative feedback loop within neural BP autoregulation?
1-A decrease in O2, increase in CO2 or increase in blood pH (increase in hydrogen) causes sympathetic system to respond
2-chemoreceptors inform heart that heart rate/ stroke volume needs to be increased or increased resistance (increases pressure-vasoconstriction)
3-chemoreceptors also increase respiration
4- therefore increases cardiac output meaning increase in o2 delivery to brain and facilitate CO2 and H buffering (via increased lung blood flow and ventilation)
What effect does exercise have on blood pressure?
-Causes Hypotension- vasodilation causing a decrease in blood pressure
-Can aslo cause Hypertension- increase in cardiac output causing an increase in blood pressure
what are the 2 sensors present within muscles?
Mechanoreceptors and chemo/metaboreceptors
how do mechanoreceptors respond to exercise and play a role in neural control?
senses change in muscle stretch (more muscle stretch, more activation of receptors, more blood flow to the muscle)
how do Chemo/ metaboreceptors respond to exercise and play a role in neural control?
senses change in metabolites in muscles (more exercise, more bi-products produced in muscle, senses change and causes more blood to flow to muscle)
How is blood pressure affected by aerobic exercise?
-vasodilating to working muscles and vasoconstricting to areas that don;t need blood flow
-increased heart rate, increased volume and cardiac output causing blood pressure increase
-As exercise intensity increases, blood pressure increases
how is blood pressure affected by resistance excercise?
-peripheral resistance is increasesd so blood flow is almost stopped for short period of time due to powerful contraction of muscles
-Cardiorespiratory system responds by increasing cardiac output (increased stroke volume and heart rate)
what is septic shock?
inflammatory response to infection-can negatively impact BP
what is the treatment for septic shock and how does it effect blood pressure?
-Increased Fluids to increase blood volume and increase BP
-Vasopressors- increase fluid retention (increase BP) and increase vessel vasoconstriction (increase BP)
-Corticosteroids- decrease inflammation and increase fluid retention (increase BP)
