Definition of blood pressure

Question 1

Define blood pressure

Answer 1

• Hydrostatic pressure of blood exerted against the walls of the blood vessels

Question 2

Describe how blood pressure changes going from arteries, all way around circulation to the vena cavae. Where is it lowest and where it is the highest?

Answer 2

• BP is highest in the aorta and larger arteries,
• Lowest in the large veins and veae cavae

Question 3

As distance from the aorta increases, what happens to the pressure?§

Answer 3

Decreases

Question 4

Where in circulation does the biggest drop in pressure occur?

Answer 4

In the transition from arteries to arterioles

Question 5

As blood enters the right atrium. what is the pressure?

Answer 5

0

Question 6

Define Mean arterial pressure

Answer 6

• The average pressure that is pushing the blood around the vascular system

Question 7

Give the two formulas for mean arterial pressure. Explain the differences in the formulas.

Answer 7

MAP = Diatsolic + (1/3 Pulse Pressure) (Pulse pressure =Systolic - Diastolic)

MAP = Cardiac Output x Total Periphral resistance

The latter formula requires invasive monitoring in order to calculate, but the former gives a good way of estimating MAP with a simple blood pressure reading.

Question 8

Blood pressure depends on the total blood volume in the CV system. What is the normal volume of blood in an adult?

Answer 8

Approximately 5L

Question 9

Define Vascular resistance

Answer 9

Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow.

Question 10

The 3 major factors that can affect blood pressure are:

Haemodynamic factors (like the physical structure of vessels, properties of the blood)

Neurohumeral factors (increased activation of the Sympathetic Nervous system)

Hormonal factors (Renin-angiotnensin, adrenaline, ADH, ANP).

Recite these

Answer 10

Recite these

Question 11

What are the 3 main factors that contribute to vascular resistance?

Answer 11

• Lumen size
• Blood viscosity
• Total blood Vessel length

Question 12

What are the effects of lumen size on vascular resistance

Answer 12

• larger the vessel lumen diameter, the less resistance there is, and therefore blood pressure is lower
• Smaller the vessel, the more resistance there is and therefore the higher the blood pressure

Question 13

Explain what is meant by blood viscosity and what factors contribute to viscosity. How does viscosity affect blood pressure? What common, often daily occurance can increase viscosity and therefore blood pressure?

Answer 13

• Viscosity is basically the ratio between the blood cells to the plasma, and to a smaller extent the concentration of proteins
• Higher the viscosity, the higher the resistance
• Dehydration, since plasma levels will be lower, thus increasing the ratio of red blood cells to plasma, therefore increasing blood pressure

Question 14

Explain how total blood vessel length affects peripheral resistance

Answer 14

• Resistance to blood flow is directly proportional to the length of the blood vessel
  
  • The longer the blood vessel, the greater the resistance, therefore higher pressure is needed to overcome that resistance

Question 15

Define blood flow

Answer 15

The volume of blood that travels through a landmark(usually a vessel or group of vessels) in a given time period.

Total systemic blood flow = Cardiac Output.

Question 16

How does cross sectional area affect velocity of blood flow?

Answer 16

• As a large artery branches, the cross sectional area of the resulting branches will be greater than the cross sectional area of the original artery
  
  • ​As such, blood flow becomes slower and slower as the cross sectional area of the blood volume decreases
  • Conversley, when venules reunite to form veins (i.e. unbranching vessels), the cross-sectional area decreases and the velocity INCREASES

Question 17

Hometstatic mechansisms regulate cardiovascular activity. Explain why these mechanisms are important at a fundamental level - i.e why does our body fight to raise or lower blood flow?

Answer 17

To ensure adequete perfusion of tissue

Question 18

Blood pressure (and thus blood flow) can regulated both locally and centrally.

Central : Neural level

Central: hormonal level

Locally: local level (controls the blow of blod within tissues)

Answer 18

RECITE

Question 19

Blood pressure (and thus blood flow) can regulated both locally and centrally - there are 3 main ways in total.

1) Central : Neural level

Describe how the CV center controls BP

Answer 19

• CV center is in Medulla oblongata in the brain steam
• CV center is made up of The Cardiac Center and Vasomotor center.

Cardiac centers are composed of cardioacceleratory cenres and cardioinhibitory centres. CA center increases cardiac output through sympathetic innervation. CI center decreases cardiac output through parasymathetic innervation.

Question 20

Explain what baroreceptors and chemoreceptors are

Question 21

Descrive how baroreceptors work and where they are found - and discuss how the alter acitivity in the CV centre in the medulla to produce effects (and state what these effects are) - Mention the reaction to both rise and fall in blood pressure

Answer 21

• Specialised receptors that monitor the degree of strecth in the walls of expandable organs
• The baroreceptors involved in cardiovascular regulation are found in the
  
  • walls of the carotid sinus (expandable chamber at the base of the internal carotid sinuses)
  • The aortic sinuses (pockets in the wall of the ascending aortic arch)
  • Wall of the right atrium
• These receptors are part of the baroreceptor reflexes, which adjust cardiac output and peripheral resistance to maintain normal arterial pressures

When blood pressure rises, the increased output from the baroreceptors alters activity in the CV center and produces two major effects:

• Decrease in cardiac output, due to stimulation of parasympathetic and inihibition of sympathetic actiivty - this is due to stimulation of the cardioinhibitory center and inhibition of the cardioacceleratory centre
• Widespread peripheral vasodilation, due to INHIBITION of exitatory neurones in the vasomotor centres

When blood pressure decreases, baroreceptor output is reduced, causing two major effects:

• Stimulation of cardioacceleratory centre and inhibition of cardioinhibitory centre - therefore causing Sympathetic actions on the heart
• Widespread peripheral vasoconstriction, because of the activation of sypathetic vasoconstrictor neurones by the vasomotor centre

Question 22

Study this diagram showing how baroreceptors respond to changes in blood pressure

Question 23

Explain how chemoreceptors work and their response to changes in blood pressure

Answer 23

• Chemoreceptors respond to changes in carbon dioxide, Oxygen or PH in blood and CSF
• They are just sensory neurones and are located in the cartoid and aortic bordies (below)
• The receptors monitor the chemical composition of the arterial blood
• Responses are regulated via the cardioaccelatory, cardioinhibitory and vasomotor centres depending on what the discrepency is ​

Question 24

The aortic and carotid sinuses both have nerves that feed into nerves which carry information to the brain. Which is supplied by which sinus?

Answer 24

Question 25

Hormonal control is one of the three important mechanisms for regulating blood pressure (Autoregulation, Neural, and Hormonal). Explain **how the Renin-Angiotensin-Aldosterone system regulates blood pressure**

Answer 25

* Low blood flow to the kidneys is **detected by juxtaglomerular cells** * **They produce renin** into the bloodstream * Liver is always producing **angiotensinogen** * **Renin acts to convert angiotensinogen to Angiotensin 1** * **Angiotensin converting enzyme** (ACE), mainly found in the lung, converts Antiotensin 1 to Angiotensin 2. * Angiotensin can raise blood pressure in one of **two ways:** * **​Acts as a Vasoconstrictor, increasing systemic vascular resistance** * **Secondly**, it stimulates secretion of **alodesterone** * **​Aldosterone** stimulates reabsorption of sodium ions and water retention by the kidneys - this increases total blood volume

Question 26

Hormonal control is one of the three important mechanisms for regulating blood pressure (Autoregulation, Neural, and Hormonal). Explain how Adrenaline and Noradrenaline regulate blood pressure

Answer 26

* Adrenaline and Noradrenaline are produced when **blood pressure is LOW** * In response to **sympathetic stimulation,** the adrenal medulla releases adrenaline and noradrenaline * There are two main ways in which these hormones increase blood pressure * Act on **ALPHA 1 receptors on blood vessels to cause vasoconstriction** * **Secondly, It increases the HR by acting on beta 1 receptors in the heart** * **THUS BP INCREASES**

Question 27

Hormonal control is one of the three important mechanisms for regulating blood pressure (Autoregulation, Neural, and Hormonal). Explain how ADH regulates blood pressure

Answer 27

* ADH is produced by the pituitary gland in response to a **decrease in blood volume, or to CIRCULATING ANIOTENSIN 2** * Causes **vasoconstriction that elevates blood pressure - AND stimulates water retention at kidneys**

Question 28

Hormonal control is one of the three important mechanisms for regulating blood pressure (Autoregulation, Neural, and Hormonal). Explain how Natriuretic peptides regulate blood pressure

Answer 28

* Cardiac muscle cells in the wall of the right atrium produce **atrial natriuretic peptide in response to excessive stretching during diastole** * Cardiac muscle cells in **ventricles** also produce a substance under similar situations, and this is called **Brain Natriuretic peptide** **What responses do** atrial natriuretic peptides and brain natriuretic peptides produce? * increase sodium excretion by kidneys * promotes water loss from kidneys by reducing water retention * Reduces thrist levels * Blocks the release of angiotensin 2, aldosterone, adrenaline and noradrenaline * Also stimulates peripheral vasodilation MAIN FUNCTION IS TO REDUCE BLOOD PRESSURE. As the stresses on the heart are removed, Natriuretic peptide production decreases.

Question 29

Study this diagram show the main **hormonal responses with regards to a DECREASE in blood pressure**

Question 30

There is one other substance released by the kidneys in response to a **decrease in blood pressure,** which is **eyrthropoietin. What are the two ways in which this can correct blood pressure**

Answer 30

* Increases red blood cell formation - increasing the volume and viscosity of the blood, improving it's carrying capacity * Also acts **directly on vessels, causing vasoconstriction**

Question 31

Describe the locations of the peripheral baroreceptors and chemoreceptors

Answer 31

Baroreceptors: * In the aortic arch * In the carotid sinus of the internal carotid Chemoreceptors: * Carotid body in the external carotid artery * in the aortic arch