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Cardiovascular > Blood volume and blood pressure regulation > Flashcards

Blood volume and blood pressure regulation Flashcards

1
Q

What does the pump depend on?

A

Venous return

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2
Q

What is the average cardiac output at rest?

A

5L per min

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3
Q

What is the purpose of arterioles?

A

Resistance to flow

Control where cardiac output is directed

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4
Q

What are the pressures in the arteriole?

A

35 to 15 mmHg hydrostatic gradient
1 mmHg hydrostatic interstitial
25 mmHg oncotic so capillaries favour reabsorption

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5
Q

How are arterioles disturbed?

A

accumulation of interstitial oedema, reduction in plasma oncotic pressure =- low protein concentration

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6
Q

What can cause disruption to arteriole pressures?

A

chronic liver disease and malnutrition, nephrosis

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7
Q

What increases interstitial oncotic pressure?

A

Inflammation- porous capillaries lose proteins

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8
Q

What increases venular hydrostatic pressure?

A

Deep vein thrombosis

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9
Q

What increases arteriolar hydrostatic pressure?

A

vasodilator drugs, calcium channel blockers

Blockage of lymphatic system, malignant infiltration

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10
Q

How is circulatory blood pressure maintained in haemorrhage?

A

Volume deplete. Loss of pressure, pressure over capillary lower so oncotic pressure more dominant so draw in water

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11
Q

What are the challenges to homeostasis?

A

Fluid deprivation= lack of access to water , fluid overload= excess oral intake/ IV, fluid depletion= excessive fluid loss diarrhoea, exercise and meals, temp changes, postural changes, acceleration zero gravity

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12
Q

What are the most important organs to provide perfusion to by maintaining blood pressure?

A

Brain and heart most critical, skin least

Kidney, GI, muscle

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13
Q

Why must blood volume be maintained?

A

to provide venous return necessary for adequate cardiac output and blood pressure generation- maintaining renal perfusion

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14
Q

How is afferent information collected?

A

from arterial baroreceptors in carotid sinus and arch in blood pressure regulation, volume stretch receptors and juxtaglomerular cells in blood volume regulation

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15
Q

What are efferent signals?

A

autonomic NS, circulating hormones renin-angiotensin system (angiotensin 2) adrenaline and vasopressin/ local factors NO, endothelin, kinins, prostaglandins, renin-angiotensin in blood pressure
circulating hormones rein-angiotensin system (aldosterone)natriuretic peptides, vasopressin

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16
Q

What are the effector organs?

A

heart and arterioles in blood pressure, kidneys blood volume

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17
Q

What are the response times?

A

pressure seconds minutes, volume- mins to hours

18
Q

What are changes mediated by?

A

G protein receptors,= agonists bind, signal transduction, requires bonding of intermediate protein- beta-adrenergic, alpha-1-adrenergic muscarinic cholinergic
Secondary messenger- signal amplification, biological effect, muscle

19
Q

What is blood pressure?

A

Hydrostatic pressure within circulatory system, mmHg
Large artery- brachial (120/80
Peak systolic pressure, trough diastolic pressure

20
Q

What is the equation to work out blood pressure?

A

ABP (arteriole blood pressure)= CO X SVR (Systemic vascular resistance)
SVR majority provided by arterioles
Altered muscle tone
R= resistance, L length of vessel, n= viscosity of blood, r= radius of vessel (Poiseuille equation)

21
Q

What is arteriole blood pressure dependent on?

A

heart rate, cardiac contractility, arteriolar tone

22
Q

How is heart rate regulated?

A

Heart rate increased by noradrenaline, adrenaline, beta-1 adrenoreceptors
Decreased by acetylcholine, muscarinic receptors

23
Q

How is myocardial contractility increased?

A

noradrenaline, adrenaline, beta 1

24
Q

How is SVR influenced?

A

radius of lumen- tone of media (smooth muscle)- post ganglionic sympathetic, noradrenaline vasoconstriction- alpha 1
Adrenaline vasodilation beta 2
Angiotensin 2=2 released when renin-angiotensin system active, vasopressin= posterior pituitary gland when plasma volume reduced, osmolality increased, NA (circulating hormones)- constriction
Local= endothelin (constriction), NO (dilation)

25
Q

What is the baroreceptor reflex?

A

providing second to second control of blood pressure

26
Q

Where do the signals for blood pressure regulation come from?

A

Afferent info= arterial baroreceptors= carotid sinus- glossopharyngeal nerve (1X), aortic arch- vagus nerve (X)
Mechano-sensory neurones, respond to stretch
CNS- vasomotor centre medulla oblongata
Efferent signals- SN (reduced blood pressure)- increase rate and contractility- tachycardia (beta 1)/ blood vessels arteriolar constriction (alpha 1) venoconstriction (a1)/ adrenal medulla- secretion of catecholamines (a, na)/ kidneys arteriole constriction (a1), renin secretion (b1)
Para= bradycardia, muscarinic

27
Q

How does the baroreceptor reflex vary?

A

Baroreflex sensitive in younger individuals
Hypertension- chronic- high blood pressure, allowed to reset reflex
Baroreceptor reflex critical to defence of blood pressure and cerebral blood flow

28
Q

How can changes in blood pressures be treated?

A

Blood pressure increase= vasoconstrictor= phenylephrine
Reduction= vasodilator= glyceryl trinitrate
Tilt table

29
Q

What is the blood volume in an average person?

A

70 kg male= 4L (blood intravascular volume)

50-60% volume in veins- reservoir to regulate venous return, divert if necessary

30
Q

Describe the role of the kidneys in blood volume regulation

A

renal blood flow 1.25 L/min (25% CO)
GFR (Glomerular filtration rate)= 125 mL/min (180L/day)
Urine output- 1.5 L/day (1 ml/min)

31
Q

Where the receptors in blood volume regulation?

A

Volume sensors= kidneys= juxtaglomerular cells sense low Na ions delivery and urine flow, release renin
Heart- low pressure stretch receptors in atrium (venous return)- sympathetic NS

32
Q

Describe the efferent signals (blood volume)

A

Renin-angiotensin system (angiotensin and aldosterone)= efferent arteriolar constriction (AT 1)- more filtration, systemic vasoconstriction (AT1)

33
Q

What are the effects on the body from blood volume regulation?

A 
Aldosterone release (adrenal cortex) conserve sodium
Vasopressin release (posterior pituitary), thirst
Sympathetic nerves- tachycardia and increased contractility
Arteriolar constriction and venoconstriction= less reservoirs
Renin secretion and arteriolar constriction
Sodium and ester retention= vasopressin, natriuretic peptides
34
Q

Describe the renin-angiotensin system

A

macula densa closely packed specialised cells lining wall of cortical thick ascending limb- distal convoluted tubule, sensitive to NacL conc in ascending limb= decreased= decreased resistance (vasodilation in afferent arteriole- increase GFR hydrostatic pressure increases), increased renin release from cells of arterioles- storage sites of enzyme renin
Renin cleaves deck of peptides (angiotensin 1) from angiotensinogen- cleaved to angiotensin 2 by angiotensin converting enzyme- various actions

35
Q

What are the effects of the renin-angiotensin system?

A

• AT 2 effects= arteriolar vasoconstriction preserves ABP and glomerular perfusion/ aldosterone release stimulates sodium and water retention/ vasopressin secretion stimulates water retention and thirst stimulates water intake
Renin angiotensin system critical to defence of renal blood flow and extracellular fluid volumes

36
Q

What are the causes of haemorrhage?

A

major injury, complications of surgery, GI bleeding, obstetric bleeding

37
Q

What are the effects on the body from haemorrhage?

A

Decrease in intravascular volume, venous return to the heart, ventricular filling, cardiac output, blood pressure, renal perfusion, capillary hydrostatic pressure

38
Q

Describe the afferent information in haemorrhage

A

Afferent sensors activated- carotid baroreceptors aortic arch baroreceptors &sympathetic)
Reduce atrial filling, sympathetic NS, atrial volume stretch receptors
Juxtaglomerular sensors- arteriolar pressure decrease

39
Q

Describe the efferent effects in haemorrhage

A

Efferent- tachycardia, contractility increased, vasoconstriction, venoconstriction, catecholamine secretion, sweating
Renin release, all-mediated vasoconstriction, aldosterone release, vasopressin release Passive reabsorption of water from interstitial fluid

40
Q

What are the symptoms of haemorrhage?

A

Symptoms- tachycardia, pale skin, cold peripheries, sweating

Response= hypotension, reduced urine output, confusion

41
Q

What is syndrome of hypovolaemic shock?

A

failure to preserve a sufficient blood intravascular volume

42
Q

How do you treat haemorrhage?

A

IV fluid, blood transfusion

Cardiovascular (52 decks)

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