BSCI450: CV Modulation

ventricular PV relationship

what happens during passive filling

volume increases

pressure constant

ventricular PV relationship

atrial contraction

volume increases

pressure increases

ventricular PV relationship

isovolumic contraction

volume constant

pressure increases

ventricular PV relationship

ventricular ejection

volume decreases

pressure increases

ventricular PV relationship

ventricular relaxation

volume constant

pressure decreases

rank locations where blood is typically found (most to least)

systemic veins/venules

systemic arteries/arterioles

pulmonary blood vessels

heart

capillaries

which blood vessel has the largest internal diameter

vein

which blood vessel has the smallest internal diameter

capillry

which blood vessel has the largest wall thickness

artery

which blood vessel has the smallest wall thickness

capillary

what wraps around blood vessels

smooth muscle and elastin

are capillaries wrapped in smooth muscle? elastin?

no, no

are venules wrapped in smooth muscle? elastin?

depends on size, yes

are arteries wrapped in smooth muscle? elastin?

yes, yes

are arterioles wrapped in smooth muscle? elastin?

yes, yes

are veins wrapped in smooth muscle? elastin?

yes, yes

how to smooth muscle and elastin contribute to non-compliance

smooth muscle - prevents change in size upon increased BP

elastin - if volume does change, recoils back to OG shape

special features

arteries

arterioles

capillaries

venules

veins

very non-compliant

control over TPR (innervated to autonomic NS can shrink to alter size and direct blood flow)

thin wall, permeable

very compliant

very compliant, smooth muscle helps blood move back to heart

what is significant about the compliance of veins

contributes to blood pooling

compliance equation

deltaV/deltaP

what is low compliance

volume change generates big pressure change

what structures in veins help combat pooling

valves open due to skeletal muscle movement allow blood flow to heart

what is present in the thoracic cavity

lungs and heart

how does the thoracic pump affect venous return

more negative intrapleural pressure

more abdominal pressure pushes on vena cava

what is the main mechanism of autonomic control over blood pressure

baroreceptor reflex

what is the purpose of the baroreceptor reflex

maintains stable BP after period of inactivity

why do people get light headed upon standing

lack of blood flow to brain, hypoxia

what is the precursor to baroreceptor reflex

veins compliant and inelastic → pooling in lower extremities → reduced venous return → reduced stroke volume → BP drop in upper extremities

orthostatic hypotension

drop in BP upon standing

what 3 things does the baroreceptor reflex affect

heart rate, stroke volume, total peripheral resistance

what kind of outputs can the baroreceptor have

sympathetic and parasympathetic

what is a baroreceptor

pressure sensor

what are the three responses to decrease in BP

increased heart rate
increased contraction force
vasoconstriction in lower extremities

as arterial pressure increases, heart rate…

decreases

sympathetic

fight or flight

parasympathetic

rest and digest

as BP increases, parasympathetic AP rate

increases

as BP increases, sympathetic AP rate

decreases

when do baroreceptors fire most

during systole (high mean arterial pressure)

what is analogous to baroreceptor pressure sensors

skeletal muscle stretch receptors

where are baroreceptors located

what do they sense (specifically)

what channel allows mechanosensation

carotid sinus and aortic arch

stretch of vessel wall

piezo

baroreceptors

at high BP

at low BP

more stretch → more APs

less stretch → less APs

if you increase the BP of a ____ mouse, baroreceptor neuron activity

control — increases

piezo knockout — doesn’t change

if you increase BP in a healthy mouse…

if you increase BP in a piezo knockout mouse…

heart rate decreases

heart stays the same

4 targets of ANS in CV system

SA node

AV node

ventricular myocardium

blood vessels

what NT does the parasympathetic nervous system release

ACh

what NT does the sympathetic nervous system release

NE

which autonomic branches innervate the SA node

parasympathetic - ACh slows heart rate

sympathetic - NE speeds heart rate

which autonomic branches innervate the AV node

parasympathetic - ACh lengthens delay

sympathetic - NE shortens delay

which autonomic branches innervate the ventricular myocardium

sympathetic - shorter, more forceful contraction

which autonomic branches innervate the blood vessels

sympathetic - vasoconstriction

expanding: autonomic regulation of SA node — sympathetic

neurotransmitter

receptor

type of G protein

effect

mechanism

NE

beta 1

stimulatory

increase heart rate

NE binds B1 → G protein activated → activates adenylyl cyclase → increases cAMP → cAMP has two impacts

1. binds HCN channels to increase Na and K inward current

2. activates PKA → phosphorylates L-type Ca channels → makes them open faster

expanding: autonomic regulation of SA node — parasympathetic

neurotransmitter

receptor

type of G protein

effect

mechanism

ACh

muscarinic

inhibitory

decreases heart rate

ACh binds M → G protein activated → inhibits adenylyl cyclase → decreases cAMP