Cardiovascular System

Question 1

What BP is hypertension classed as?

90% of HT is what?

Answer 1

140/90+

-90% is idiopathic

Question 2

Name 3 effects HT can have on vessels.

Answer 2

• atheroma and aneurysm and microaneurysms
• elastic reduplication of lamina in arterioles
• retinal capillary damage
• nephrosclerosis, glomerulosclerosis

Question 3

What is hyaline arteriosclerosis?

Answer 3

Plasma exudes into intima/deep layers of arterioles

Glassy pink on histology

Question 4

What is a false aneurysm?

Answer 4

-breach in wall, blood leaks out but is contained in adventitia, expands

Question 5

3 Types of Aneurysm

Answer 5

• Berry/saccular - @CofW bifurcations, rupture subA
• microaneuysm - HT in cerebral arteries
• Abdo Aortic A - usually post atheroma
• Stretched Aortic Ring - by infection or aortic dissection

Question 6

What is aortic dissection?

Answer 6

• elderly with medial degeneration/Marfan’s
• tear in intima so blood enters aortic wall forming a parallel tract
• Vessel dilates, may rupture through adventitia

Question 7

What is a stroke?

3 associated factors:

Answer 7

-sudden onset of neurological deficit due to CV

HT, smoking, AF, high cholesterol

Question 8

80% of strokes are ischemic, where/why might these occur?

Answer 8

• thromboembolic/mural thrombus
• 1ry occlusion of intracerebral artery
• lacunar (lenticulostriate perforating artery occlusion)

Question 9

Why might a haemorhhagic stroke occur? What may it cause in the brain?

Answer 9

• rupture of cerebral microaneurysm

- midline shift as blood compresses brain

Question 10

What is the penumbra areas of brain?

Answer 10

• infarct area necroses but adjacent areas may have some compensation from other branches
• if perfusion is restored <3hrs this ‘penumbra’ can be salvaged

Question 11

Why are stroke cerebral lesions ‘soft’?

Answer 11

Liquefaction necrosis after MOs clear it they leave cystic spaces and nearby gliosis may be seen

Question 12

What is a TIA?

Answer 12

neurological deficit lasting <12-24hrs. (Increases risk of stroke)

Question 13

What are the brains requirements for blood?

Answer 13

• constant high flow of O2 rich blood
• supply that can change with need
• extracts lots of O2 at rest (vulnerable to hypoxia)

Question 14

Name 2 special structural features of brain circulation?

Answer 14

• Circle of Willis - colaterals if stenosis occurs
• BBB tight endothelial junctions, selective control
• high capillary density

Question 15

How does the brain modulate its BP/blood flow e.g. in case of high blood pressure?

Answer 15

Caroitid sinus baroreceptors monitor stretch, CN IX
NTS -> CVLM -> RVLM -> decreases symp at IML point
Decrease HR, SV and BP

Question 16

Cerebral arterioles dont have baro-reflex vasoconstriction, how do they regulate pressure/flow?

Answer 16

Myogenic autoregulation (high BP causes vasoconstricts to keep flow the same.

Question 17

Explain metabolic autoregulation of cerebral arteries.

Answer 17

• increased pCO2/increased H+ causes vasodilation

- and low O2/hypoxia releases vasodilating metabolites

Question 18

Explain regional hyperaemia of cerebral arteries.

Answer 18

• increased K+ (ECF) hyperpolarises the VSMC

- hence they are relaxed = vasodilation in active areas

Question 19

Name a vasoconstrictor abundant in perivascular nerves

Name a metabolite released in hypoxia causing vasodilation.

Answer 19

5HT-v.constrictor

Adenosine - v.dilates

Question 20

Perivascular nerves have nociceptive fibres that mediate pain of vascular headaches, what would they do in e.g. a migrane?

Answer 20

-less release of vasoconstrictors (5HT)
-more vasodilators e.g. Sub P and CGRP
(also you get inflammation of extracerabral arteries)

Question 21

What is the mechanism of action of Sumatriptan given to treat migranes?

Answer 21

5HT1B agonist - causes vasoconstriction

decreases inflammation and pain

Question 22

What does the BBB keep in/out?

Answer 22

Keeps in - NTs

Keeps out - neuroactive chemicals

Question 23

At what 3 places is the BBB defective at?

Answer 23

• area postrema of CTZ - drugs, toxins, Ang II enter
• subfornicular organ of hypothal - Ang II - thirst
• paraventricular osmoreceptors -> +/- ADH

Question 24

What happens with herniation due to a space occupying lesion?
AKA?

Answer 24

-RVLM compressed which increases its activity
-more symp, higher BP –> activates baroreflex
-more vagus, decreased HR = reflex bradycardia
Cushing’s reflex

Question 25

Cerebral Artery Vasospasm reduces flow and can cause a stroke. What local agents may cause it?

Answer 25

• local vasoconstrictors: 5HT, NPY (perivascular nerves)

- endothelin1 from damaged endothelium

Question 26

What can be used to treat Cerebral Artery Vasospasm?

Answer 26

• VGCa2+C blockers e.g. amlodipine

- ETA receptor blockers e.g. bosentan