Cardiovascular System Flashcards
What BP is hypertension classed as?
90% of HT is what?
140/90+
-90% is idiopathic
Name 3 effects HT can have on vessels.
- atheroma and aneurysm and microaneurysms
- elastic reduplication of lamina in arterioles
- retinal capillary damage
- nephrosclerosis, glomerulosclerosis
What is hyaline arteriosclerosis?
Plasma exudes into intima/deep layers of arterioles
Glassy pink on histology
What is a false aneurysm?
-breach in wall, blood leaks out but is contained in adventitia, expands
3 Types of Aneurysm
- 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
What is aortic dissection?
- elderly with medial degeneration/Marfan’s
- tear in intima so blood enters aortic wall forming a parallel tract
- Vessel dilates, may rupture through adventitia
What is a stroke?
3 associated factors:
-sudden onset of neurological deficit due to CV
HT, smoking, AF, high cholesterol
80% of strokes are ischemic, where/why might these occur?
- thromboembolic/mural thrombus
- 1ry occlusion of intracerebral artery
- lacunar (lenticulostriate perforating artery occlusion)
Why might a haemorhhagic stroke occur? What may it cause in the brain?
- rupture of cerebral microaneurysm
- midline shift as blood compresses brain
What is the penumbra areas of brain?
- infarct area necroses but adjacent areas may have some compensation from other branches
- if perfusion is restored <3hrs this ‘penumbra’ can be salvaged
Why are stroke cerebral lesions ‘soft’?
Liquefaction necrosis after MOs clear it they leave cystic spaces and nearby gliosis may be seen
What is a TIA?
neurological deficit lasting <12-24hrs. (Increases risk of stroke)
What are the brains requirements for blood?
- constant high flow of O2 rich blood
- supply that can change with need
- extracts lots of O2 at rest (vulnerable to hypoxia)
Name 2 special structural features of brain circulation?
- Circle of Willis - colaterals if stenosis occurs
- BBB tight endothelial junctions, selective control
- high capillary density
How does the brain modulate its BP/blood flow e.g. in case of high blood pressure?
Caroitid sinus baroreceptors monitor stretch, CN IX
NTS -> CVLM -> RVLM -> decreases symp at IML point
Decrease HR, SV and BP
Cerebral arterioles dont have baro-reflex vasoconstriction, how do they regulate pressure/flow?
Myogenic autoregulation (high BP causes vasoconstricts to keep flow the same.
Explain metabolic autoregulation of cerebral arteries.
- increased pCO2/increased H+ causes vasodilation
- and low O2/hypoxia releases vasodilating metabolites
Explain regional hyperaemia of cerebral arteries.
- increased K+ (ECF) hyperpolarises the VSMC
- hence they are relaxed = vasodilation in active areas
Name a vasoconstrictor abundant in perivascular nerves
Name a metabolite released in hypoxia causing vasodilation.
5HT-v.constrictor
Adenosine - v.dilates
Perivascular nerves have nociceptive fibres that mediate pain of vascular headaches, what would they do in e.g. a migrane?
-less release of vasoconstrictors (5HT)
-more vasodilators e.g. Sub P and CGRP
(also you get inflammation of extracerabral arteries)
What is the mechanism of action of Sumatriptan given to treat migranes?
5HT1B agonist - causes vasoconstriction
decreases inflammation and pain
What does the BBB keep in/out?
Keeps in - NTs
Keeps out - neuroactive chemicals
At what 3 places is the BBB defective at?
- area postrema of CTZ - drugs, toxins, Ang II enter
- subfornicular organ of hypothal - Ang II - thirst
- paraventricular osmoreceptors -> +/- ADH
What happens with herniation due to a space occupying lesion?
AKA?
-RVLM compressed which increases its activity
-more symp, higher BP –> activates baroreflex
-more vagus, decreased HR = reflex bradycardia
Cushing’s reflex
Cerebral Artery Vasospasm reduces flow and can cause a stroke. What local agents may cause it?
- local vasoconstrictors: 5HT, NPY (perivascular nerves)
- endothelin1 from damaged endothelium
What can be used to treat Cerebral Artery Vasospasm?
- VGCa2+C blockers e.g. amlodipine
- ETA receptor blockers e.g. bosentan
