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Physiology- term 1 > week 5- vascular system and blood pressure > Flashcards

week 5- vascular system and blood pressure Flashcards

1
Q

what basic structures are all blood vessels made from

A

tunica intima
tunica media
tunica externa

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2
Q

what is in the lumen of a vein and not an artery

A

valve

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3
Q

what makes up the tunica externa

A

loose CT

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4
Q

what makes up the capillaries

A

only the tunica intima

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5
Q

what is the largest section which makes up vessels

A

tunica media.

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6
Q

the larger the lumen the…

A

less frictional forces
less resistance

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7
Q

why do veins have thick tunica external

A

for structural support due to its large lumen

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8
Q

what is blood Flow directly proportional to

A

pressure gradient (high to low)

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9
Q

how can we increase pressure gradients

A

by increasing cardiac output

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10
Q

how can we alter resistance

A

by altering blood vessel size.
vasocontriction= increases resistance, reduce blood flow
vasodialation= decreases resistance, increase blood flow

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11
Q

what is resistance influenced by

A

blood vessel length.
blood viscosity

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12
Q

What makes up the tunica intima

A

Enothelial cells

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13
Q

Name the elastic arteries

A

Pulmonary artery
Aortic artery

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14
Q

What structure do capillaries live in

A

A mesh structure called capillary beds

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15
Q

What does a capillary Network/mesh allow

A

Nearly all cells of tissues are within diffusion distance of these vessels.

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16
Q

What determines how leaky an intracellular cleft is

A

The amount of tight junctions between epithelial cells

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17
Q

Why do intracellular clefts lack tight junctions

A

To allow diffusion of solutes (skin, muscle, etc)

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18
Q

Describe muscular pump and how this relates to venous return

A

Some veins travel between large muscle groups. When muscles contract they squeeze blood in the vessel. Veins have valves so blood can only move towards the heart. No backflow, blood returns

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19
Q

What happens to the blood in the thorax during inspiration

A

Draw blood into the thorax and back towards the heart

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20
Q

At rest, blood flow is determined by…

A

The number and size of the arteries supplying them

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21
Q

What is each arteriolar linked to

A

A neurone from the sympathetic nervous system

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22
Q

What causes vasoconstriction?

A

Signals being sent down the sympathetic system from the arteriole linked to the neurone

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23
Q

Can any signals cause vasodialation

A

No

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24
Q

What are arteriolar influenced by, give examples

A

Metabolic factors
Acidity (lactic acid, c02) low atp, low o2, high co2 could develop if blood flow is low

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25
Q

What does vasodialation allow

A

Blood flow into the capillary bed

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26
Q

What does vasoconstriction cause

A

Bypasses in the thoroughfare channel. Blood has it exchanged gases as it is shunted and will travel to more active tissues

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27
Q

Double the length=

A

Half the flow

28
Q

What is the primary sensory receptor

A

Baroreceptors

29
Q

Where are baroreceptors found

A

Carotid sinus
Aortic arch

30
Q

What are baroreceptors, what do they respond to?

A

Mechanoreceptors
Stretch of blood vessel

31
Q

Describe sympathetic control of vasoconstriction

A

-stretching of baroreceptors increases impulses to the Cardiovascular centre of medulla oblongata
-VASOMOTOR centre in CV centre has sympathetic efferents
-these synapse with arteries, arteries and veins stimulation body wide vasoconstrictions ^ bp

Reduced output through sympathetic efferents causes body wide vasodiolation, decrease Bp

32
Q

Why would blood flow not be reduced to very active tissues

A

Local metabolic tissue conditions are more dominant

33
Q

What does blood pressure represent

A

The force added from the heart (cardiac ouput)
Peripheral resistance provided by blood vessels

34
Q

What is the mean arterial pressure (MAP)

A

Average driving force for blood flow to occur.
At rest this is closer to diastolic pressure as at rest spent more time filling

35
Q

What is meant by systolic pressure

A

Peak force of blood pushing against blood vessels walls which occurs at the end of ventricular emptying. Combo of force generated by heart (cardiac output) and resistance of conducting vessels

36
Q

What is meant by diastolic pressure

A

Minimal force of blood pushing against blood vessel walls which occurs at the end of the ventricular filling. When ventricles are resting, it represents how easily blood flows away into peripheral tissues.

37
Q

Describe hypotension

A

(<100/60 mm Hg)
100= systolic
60= diastolic

Low bp
Poor nutrition- low blood proteins
Low blood viscosity
Pooling of blood in elderly

38
Q

Describe hypertension

A

(<140/90 mmHg)
140= systolic
90= diastolic

High bp
Increase peripheral resistance
Diet ^Na+
Obscenity, hereditary, stres, smoking

39
Q

elastic arteries leaving the heart ensure continuous blood flow even when the ventricles are resting (diastole). explain how this happens

A

-during ventricular diastole, blood tries to move down its pressure gradient from the aorta and pulmonary artery back towards the resting ventricle.
-blood fills in semi lunar valve stopping its re-entry
-blood causes walls of aorta to stretch and elastic fibres recoil forcing blood to move out and to the body

40
Q

explain how the structure of capillaries means that they are ideally suited to exchanging materials between blood and body tissues.

A

tunica externa and media are absent, and the endothelial cells have small spaces between them.
this allows the exchange of material (o2, nutrients, waste products) to and from the tissue

41
Q

what is the function of veins and how does their structure help them to achieve this function

A

collect deoxygenated Leo pressure blood and return it to the heart. veins have large lumens which offer the least resistance to flow and also have valves that prevent back flow of blood

42
Q

pressure in the venous system veins is very low and is facilitated by the ‘respiratory pump’ and ‘muscular pump’. describe how this works

A

thorax contains lungs and major vessels of the heart.
pressure changes in the lungs influence these vessels during breathing cycle.
-during inhalation pressure in the thorax is reduced and blood will flow from a vessel inferior to the thorax (which are at a higher pressure) , to vessels in the thorax, which are at lower pressure.
-during exhalation a reversal of this process is prevented by valves in the veins

43
Q

how is blood flow increased to tissues

A

vasodilation increases blood tissues, where smooth muscle with tunica media of s blood vessel is relaxed. pressure gradients also need to be maintained or increased.

44
Q

describe the neural control of blood vessel diameter

A

-drop in bp stimulates baroreceptors in aorta and carotid arteries. increases signal frequency to VASOMOTOR centre within cv and medulla oblongata. increasing sympathetic stimulation to arterioles of the body which stimulate vasoconstriction.

45
Q

how can blood Flow to tissues and organs be turned on or off

A

-blood is supplied to organs through capillary beds which provides a large sa to exchange substances with the tissues
-capillary beds also increase distances and friction in which blood must travel, reducing pressure.
-blood flow is regulated by precapillary sphincters (of the thoroughfare channel of the arterioles)
*-contraction of the precaplary syphynsters prevents blood leaving (the road) and BLOOD BYPASSES the capillary bed directly into the venule.

continues synonymous with tissue activity, low o2, high co2, low ph, low atp, stimulate sphincters to relax thereby allowing blood to flow in the capsular bed, pursuing the tissue with o2, nutrient rich blood

46
Q

explain how changed in local metabolic factors such as low o2 influence neural control

A

products of cellular respiration stimulate local arterioles and precapillary sphincters to relax even when neural sympathetic stimulation is present. sunning blood flow Is maintained or increased to areas that are respiring hard, closing off those that aren’t.

47
Q

Define blood pressure?

A

The force applied to the surface of a blood vessel by the bloodcontained within it.

48
Q

State what is meant by “diastolic” and “systolic” blood pressure.

A

Diastolic BP – lowest pressure exerted against the blood vessel wallsduring the cardiac cycle which occurs during ventricular diastoleSystolic BP – Highest pressure exerted against the blood vessel wallsduring the cardiac cycle which occurs during ventricular systole

49
Q

What would a change in systolic blood pressure mean? Your answershould consider the physiological factors that contribute to its value

A

As blood pressure is a combination of the forced placed onto bloodby the heart (Cardiac output) and the resistance that blood vesselsoffer (Peripheral Resistance), i.e. BP =COx TPR, then both of thesefactors contribute to systolic pressure

50
Q

What would a change in diastolic blood pressure mean? Your answershould consider the physiological factors that contribute to its value

A

During diastole, the direct force from ventricle contraction has endedas the ventricles are resting. Therefore, diastolic pressure can bethought of as the influence/condition of blood vessels downstreamfrom the measurement as their resistance as this will determine
-if blood flows easily(pressure will fall) or prevented(pressure willremain high).
-Wide blood vessels in the peripheral vascular will offer the least resistance and will allow blood to flow quickly away anddiastolic pressure will fall/will be low.
-Narrower blood vessels in the peripheral vascular will offer more resistance and blood will flowslowly away meaning the pressure will remain high

51
Q

Explain how blood pressure can be altered by “length”, “diameter”and “blood viscosity”

A

-Length – longer the vessel the greater the frictional resistance
-Blood diameter – smaller the tube greater the frictional resistance.
-½the diameter x16 resistance(same as tubes in the respiratory system).This is normally how the body alters blood pressure within milliseconds.Obstructions or sudden changes in diameter lead to turbulent flowwhich is 4x less efficient than laminar flow.
-Blood viscosity – this is the stickiness or thickness of blood and-relates to frictional resistance between individual blood cells and other constituent parts that exist within blood. Higher the viscositygreater the resistance

52
Q

Define what is meant by the term “blood pressure

A

The force applied per unit area of blood vessel by the blood containedwithin it

53
Q

What does your systolic pressure show?

A

Systolic blood pressure is the highest pressure during the cardiac cyclewhich generally occurs at ventricular systole/contraction. It canrepresent the cardiac output as well as the condition of the majorvessels close to the heart. Higher pressures tend to be seen when bloodvessels lose their elastic properties and therefore resist expansion, oftensuggesting hardening or increased resistance.

54
Q

What does your diastolic pressure show?

A

Diastolic blood pressure is the lowest pressure during the cardiac cyclewhich generally occurs at ventricular diastole/relaxation. During thistime blood flows away from the heart
-Dependent on the CONDITION OF BLOOD VESSELS receiving the blood at the bodies peripheries.If peripheral blood vessels offer little resistance to blood flow, thissuggests that they have little narrowing or hardening and thus are healthy, blood will flow away quickly and pressure in the major vesselswill fall and a lower diastolic pressure will be observed

55
Q

What does your MAP show?

A

Mean arterial pressure is the average blood pressure and considers thatdifferent times spent in diastole and systole and therefore cannot just behalf way between the two. MAP can be considered as the driving forceof blood flow in the body.

56
Q

Describe what happened to blood pressure as you changed between thepositions and provide and explanation as to what caused the differencesyou observed

A

Seated – supine. Blood pressure will fall as gravity is no longer a force thatneeds to be opposed.
Supine to seated (immediate) – Blood pressure may fall (hydrostatic/posturalhypotension) as compensation mechanisms (neural) have not had a chance to respond.
Standing (1 minute). Blood pressure will rise to offset the increase ingravitation force

57
Q

Describe what happened to heart rate as you changed positions.

A

Seated – standing. HR increasesSeated – supine. HR reduces

58
Q

Think about the last session and explain how heart rate influences bloodpressure. Your answer should include explanations around cardiacoutput

A

Changing position to standingIncreasing gravity will cause a drop in pressure which is monitored bybaroreceptors in the aortic branch and carotid artery. The baroreceptors respond to a drop in pressure by increasing the frequency of nerve impulses tothe Cardiovascular Centre in the Medulla Oblongata. In response the CardiacCentre of the cardiovascular centre stops sending signals down theparasympathetic (brake) nerves and sends signals instead down thesympathetic (accelerator) to the heart. This increases HR and therefore CO asexplained earlier.

59
Q

Cardiac output is not the only way to change blood pressure. Provide adetailed physiological explanation as to how blood vessel diameterwould also be involved in the changes to blood pressure you observed.Your answer should include the terms baroreceptors, medullaoblongata, cardiovascular centre, vasomotor centre and arterioles. (Usediagrams if you find it helpful)

A

The Vasomotor Centre(Of the cardiovascular centre) is also stimulated at thesame time by the baroreceptors and responds by sending impulses (thatrelease noradrenalin) to the arterioles which causes vasoconstriction.Vasoconstriction increases resistance (half the diameter 16x more resistance!)and is the other “half” of blood pressure. i.e. BP= CO X ResistanceChanging position to standingIncreasing gravity will cause a drop in pressure which is monitored bybaroreceptors in the aortic branch and carotid artery. The baroreceptorsrespond to a drop in pressure by increasing the frequency of nerve impulses tothe Cardiovascular Centre in the Medulla Oblongata. In response thevasomotor Centre of the cardiovascular centre sends signals down thesympathetic (brake) nerves to arterioles of the body, stimulatingvasoconstriction. Increasing peripheral resistance increase BP and flow ismaintained to “open areas” to major organ systems.

60
Q

Blood vessel diameter is the quickest and easiest way we can changeresistance to blood flow. Using your notes, list two other factors thatcould change peripheral resistance and provide an explanation as tohow each would alter resistance

A

Viscosity – viscous fluid have more cohesive forces (sticky!) andtherefore offer more resistance to movement and therefore morepressure is required to maintain normal flow.
Vessel length – Longer vessels means fluids need to overcome increasedfrictional resistance and therefore more pressure is required to maintainnormal flow.

61
Q

State an average normal resting HR and BP for a healthy person

A

HR=70bpm, BP = 120/80 mmHg

62
Q

What stimulates precapilary syphynsters to relax

A

continues synonymous with tissue activity, low o2, high co2, low ph, low atp, stimulate sphincters to relax thereby allowing blood to flow in the capsular bed, pursuing the tissue with o2, nutrient rich blood

63
Q

What is a precapilary sphincter

A

Segments of smooth muscle that help direct blood flow

64
Q

What is meant by intrinsic conduction system and state the basic rhythm of this system

A

Cardiac conduction system is a collection of nodes and specialised cells that initiate and co-ordinate contraction of the heart muscle
The internal conduction system of the heart- sink atrial node, av node, bundle of his, bundle branches, purkunjie fibres,
Without any external influence (neural or chemical control) the sine atrial node would have a set rate of 100bpm

65
Q

When does atrial contraction occur

A

During latter part of the p wave

66
Q

When does ventrical contraction occur

A

Just after Q wave - r

Physiology- term 1 (15 decks)

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