Download 24 Regulation of blood flow

Regulation of
blood flow
Influences of metabolic products on the
diameter of vessels
Increase of Н+ ions,
pyroveniger and lactic acids,
decrease of pO2 and increase
of pCO2 in tissues
Decrease of tone of precapillary
sphincters
Dilatation of arterioles
Increase of blood flow in organs
Basal tone of vessels
Smooth muscles of vessels wall don’t relax whole. It all time has
some tension – muscular tone. Tonic condition is connect with
changes of electrical characteristic and some contraction of muscles.
Tone of smooth muscles support by two mechanisms: myogenic and
neuro-humoral. Miogenic regulation play the main role in the support
of vessel tone. When absent all nervous and humoral influences,
present vessel tone or basal tone.
In the base of basal tone is possibility of some smooth cells to the
spontaneously activity and spread of excitation from cell to cell; it
provide rhythmical changing of tone. It present in arterioles,
precapillares sphincters.
Influences, which decrease level of membrane potential, increase
frequency of spontaneously impulses and amplitude of contraction of
smooth muscles. Hyper polarization of membrane leads to
disappeared of spontaneously excitability and muscles contraction.
Role of mechano- and chemoreceptor in
regulation of the vessels tone
From mechanoreceptors of aorta
arc sensory information transmit by
left depressor (aortic) nerve, brunch
of n.vagus to the medulla oblongata.
Excitation from mechanoreceptors
of carotid sinus zone lead by Sino
carotid nerve (brunch of
glossopharingeal nerve) to the
medulla oblongata.
Characteristic of afferent link
Sensory innervations of heart and vessels is present by nerve
ending. Receptors divided by it function on mechanoreceptors, which
are reacted on the changing of arterial pressure and chemo receptors,
which are reacted on the changing of chemical composition of blood.
Irritation for mechanoreceptors is the speed and level of tissues
stretching by increase or pulse wave of blood pressure.
Angioreceptors are present at all vessel system and have the whole
receptor field, it maximal presents at the main reflector zones: aortic,
sino-carotid, in the vessels of pulmonary cycle of the blood
circulation. At the answer on the each systolic increase of arterial
pressure, mechanoreceptors of that zones generate impulses, which
disappeared in the diastolic decrease of pressure.
Minimal threshold of excitation of mechanoreceptors is 40 mm Hg,
maximal is 200 mm Hg. Increase of pressure higher than that level
don’t lead to addition increase of impulsation.
Central part in regulation of vascular tone
Central mechanisms, which regulate
connection between level of cardiac
output and tone of vessels, working by
help of complex of nervous structures,
which named vasomotor center.
Structures of vasomotor center are
present in spinal cord, medulla
oblongata, hypothalamus, cortex of big
hemisperes.
Spinal level of regulation is in the
lateral root of thoracic and lumbar
segments and consist of nervous cells,
axons of which produce the
vasculoconstrictors fibers. That neurons
support their level of excitation by help
of impulses from higher structures of
nervous system.
Vasomotor center of medulla oblongata is the main center of
regulation of blood flow. It located on the bottom of 4 ventricle, in it
upper part. Vasomotor center divided on pressor and depressor
zones.
Pressor zone support increase of arterial pressure. It connect with
the increase of tone of resistive vessels. Also increase frequency and
strength of heart contraction and as result minute volume of blood
flow.
Regulatory influences of neurons of pressor zone act by help of
increase of tone of sympathetic nervous system on heart and
vessels.
Depressor zone support decrease of arterial pressure, heart work. It
is the place of changes the impulses, which are coming from
mechanoreceptors of reflector zones and cause central inhibition of
tonic impulses of vasoconstrictors. Parallel the information from that
zone by help of parasympathetic nerves go to heart. As result,
decrease work and stroke volume of blood.
Also, depressor zone act reflector inhibition of pressor zone.
Role of brain cortex and hypothalamus
in regulation of blood flow
Centers of hypothalamus give the descendent influences on the
vasomotor center of medulla oblongata. In hypothalamus present
depressor and pressor zones. That is why hypothalamic level give
the same double reaction as bulbar center. Posterolateral part of
hypothalamus cause excitation of vasomotor center. Anterior part of
hypothalamus can cause mild inhibition of one.
Some zones of cortex also give the descendent influences on the
vasomotor center of medulla oblongata. Motor cortex excites
vasomotor center. Anterior temporal lobe, orbital areas of frontal
cortex, cingulated gyrus, amygdale, septum and hippocampus can
also control vasomotor center.
That influences form as a result of compare the information,
which enter in higher part of nervous system from different receptor
zones. It support realization of cardio-vascular component of
emotions, reaction of behavior.
Nervous efferent link of regulation of
vascular tone
Neural mechanism of efferent regulation of blood flow act by
- Preganglionic sympathetic neurons, body of which present in the
anterior root of thoracic and lumbar part of spinal cord and
postganglionic neurons, which are present in para- and prevertebral
sympathetic ganglion.
- Preganglionic parasympathetic neurons of nucleus of n. vagus,
nucleus of pelvic nerve, which present in sacral part of spinal cord,
and their postganglionic neurons.
- For hole visceral organs is efferent neurons of metasympathetic
nervous system, which are present in the intamural ganglion of their
wall.
All neurons is the end way from efferent and central influences, which
throught the adrenergic, cholinergic and other mechanism of
regulation act on heart and vessels.
Peculiarities of influences of catecholamine on the diameter
of vessels
Adrenal gland medulla
Epinephrine
Action with
β-adrenoreceptors of
vessel wall
Dilation of
vessels
Norepinephrine
Action with αadrenoreceptors of
vessel wall
Dilation of
vessels of
muscles,
brain, heart
Action with αadrenoreceptors of vessel
wall
Spasm of vessels
of skeen,
digestive organs,
kidney and lungs
Influences of chatecholamines and
vasopressin on the vessel tone
Influences of chatecholamines from adrenal glands determined by
presents of different kinds of adrenoreceptors – α and β. Connection of
hormones with α–adrenoreceptors act constriction of vessel wall, with β–
adrenoreceptor - relaxation.
Adrenalin connect with α– and β–adrenoreceptor, nor epinephrine with
α–adrenoreceptor. Adrenalin has strong action on vessels. On artery and
arterioles of skin, digestive organs, kidneys and lungs it has constrictive
influences; on the vessels of skeletal muscles, brain and heart - dilatatory.
On the physical load, emotional load it increase blood flow through
skeletal muscles, brain and heart.
Vasopressin (antidiuretic hormone) cause spasm of artery and arterioles
of organs of abdominal cavity and lungs. But vessels of brain and heart
reacted on that hormone by dilatation, which help increase the nutrition of
brain and heart.
Rennin–angiotensin-aldosteron
system
Cells of liver
Uxta glomerular
cell of kidney
Angiotensinogen
Rennin
Angiotensin І
Angiotensin converting enzyme
Angiotensin ІІ
Vascular spasm
Angiotensin ІІІ
Increase of arterial pressure
Adrenal glands
Aldosteron
Reabsorbtion
of water in
kidneys
Increase of water
in body
Role of rennin–angiotensin-aldosteron
system in regulation of vessel tone
Uxta glomerular cells of kidney produce enzyme rennin as the
answer of decrease of kidneys perfusion or increase of influences of
sympathetic nervous system. It convert angiotensinogen, which
produced in liver, in Angiotensin І. Angiotensin І, by the influences of
angiotensin converting enzyme in the vessel of lung, converted in
angiotensin II. Angiotensin ІІ has strong vasculoconstrictor influences.
It can explain of presents of sensory to angiotensin II receptors in
precapillary arterioles.
Very big dose of angiotensin II can cause the spasm of vessels of
heart and brain. Increase of rennin and angiotensin in blood increase
the thirst (need to drink water). Also angiotensin II or angiotensin III,
stimulate the production of aldosteron.
Aldosteron, which produce in the cortex of adrenal glands, increase
reabsorbtion of sodium in kidneys, salivary glands, digestive system,
and change the sensation of vessel walls to the influences of
epinephrine and norepinephrine. This is the rennin–angiotensinaldosteron system .
Changes of blood flow in the clinostatic pose
Change the body pose from vertical to horizontal
Increase of blood flow to heart
Increase the stroke volume
Increase of impulsation from mechanoreceptors of aortic arc
Activation of depressor part of vasomotor center
Inhibition of pressor part of vasomotor center
Decrease of frequency and force of heart beat, dilation of vessels
Changes of blood flow in the orthostatic pose
Change the body pose from horizontal to vertical
Depo of blood in the vein of down part ofbody
Decrease of blood flow to heart
Decrease of stroke volume
Decrease of impulsation from mechanoreceptors of aortic arc
Activation of pressor part of vasomotor center
Increase of frequency and force of heart beat, vascular spasm
Regulation of blood
flow in physical
exercises


In physical exercises impulses
from pyramidal neurons of
motor zone in cerebral cortex
passes both to skeletal muscles
and vasomotor center. Than
through sympathetic influences
heart activity and
vasoconstriction are promoted.
Adrenal glands also produce
adrenalin and release it to the
blood flow.
Proprioreceptor activation
spread impulses through
interneurons to sympathetic
nerve centers. So, contraction of
skeletal muscle during exercise
compress blood vessels,
translocate blood from
peripheral vessels into heart,
increase cardiac output and
increase arterial pressure.
Renew of blood flow in the case of bleeding
Bleeding
Decrease of impulsation from mechanoreceptors
and increase from chemo receptors of aorta arc
and carotid sinus
Increase of influences
of sympathetic
nervous on heart
Activation of pressor
part of vascularmotor centre
Decrease of filtration in
kidneys glomerulus's
Activation of rennin-
angiotensin-aldosteron
system
Increase of Na+
Increase of heart
Spasm of vessels and
and water
beat and the strength decrease of capacity
Angiotensin ІІ reabsorbtion
of heart contraction
of circulatory bed
Increase of Volume of Blood
Circulation
Normotonic type of cardio-vascular reaction
on the physical load
This type of set if
when the rise in heart rate is in
60-80%, and increase
systolic blood pressure
does not exceed 30% at low
diastolic blood pressure
to 20% of the original condition. at
The percentage increase in pulseOn pressure must meet the percentage
ment increase in heart rate. Duration ofrestorative period shall not exceedschuvaty 3 min. Let us consider forarbitrary normotonichnoyu reaction
when the rate of change of blood pressure
and heart rate reexceeds normative values​​, but
recovery period ends to 3 minutes.
%
90
80
70
60
50
40
30
20
10
0
-10ВС
1 хв
2 хв
3 хв
4 хв
5 хв
-20
-30
ЧСС
САТ
ДАТ
Interpretation





% of increase heart beat - % of increase pulse
pressure (increase systolic AP and decrease of
diastolic AP)
This is rational reaction, because in the case
of heart beat increase also increase pulse
pressure and stroke volume of blood.
Increase of systolic pressure is the increase
of systole of left ventricle
Decrease of diastolic pressure is decrease of
arteriole tonus, that help of better supply of the
blood on periphery
Hypotonic type of cardio-vascular
reaction on the physical load (Functional
insufficiency of heart)
%
140
For
hypotonic reaction is characterized
by a significant increase in heart rate
(by 120-150%) with a moderate
increase in SBP and unchanged or
slight increase in DBP relative to the
initial state, which leads to little marked
increase in pulse pressure (by 12-15%).
The percentage increase in PA does
not match the percentage increase in
heart rate. The duration of the recovery
period for this type of reaction than 3
minutes.

120
100
80
60
40
20
0
ВС
1 хв
ЧСС
2 хв
3 хв
САТ
4 хв
5 хв
ДАТ
Hypertonic type of cardio-vascular reaction
on the physical load (Functional insufficiency of heart
and blood vessels. Predictor of arterial hypertension
This reaction is characterized by a significant
increase in heart rate (< 120% ) relative to the
initial state . Systolic blood pressure increased
to 180-190 mmHg. century. (50% ).
Diastolic pressure is increased and
maintained higher than the initial state for all
time the recovery period . Return parameters to
their original values ​takes more than 3 minutes.
Let us consider the reaction of hypertension in
the case when the growth SAP is within 30-40%,
with an increase in DAP of 10-15% relative to
the initial state .
Restoration of blood pressure and heart rate
also lasts for more than 3 minutes.
140
)
%
120
100
80
60
40
20
0
ВС
1 хв
HR
ЧСС
2 хв
3 хв
SAP
САТ
4 хв
5 хв
DAP
ДАТ
Distonic type of cardio-vascular
reaction on the physical load (Functional
insufficiency of blood vessels. Predictor of autonomic distony)
160
This reaction set in when the heart
rate increases to 100% of the initial
state with a sharp fall DBP, until the
emergence of the phenomenon of notaper t .
Pulse pressure as a result of growing
adequately percentage increase in heart
rate. Systolic blood pressure increased
moderately (up to 40-60% of the original
state).
Recovery targets for this type of
reaction lasts more than 3 minutes.
%
140
120
100
80
60
40
20
0
-20ВС
1 хв
2 хв
3 хв
4 хв
-40
-60
-80
-100
-120
ЧССHR
САТSAP
ДАТ
DAP
5 хв
Step type of cardio-vascular reaction on
the physical load (Functional insufficiency of
regulatory apparatuses of blood flow)
The response of a stepped increase
SAT characterized in that the 2nd and
3rd minute recovery period SBP rises
above what it was at 1 minute.
100
Duration restore all parameters than
3 minutes. It is believed that this type
points to a functional deficiency of
regulatory mechanisms of the
cardiovascular system.
40
%
80
60
20
0
ВС
1 хв
2 хв
3 хв
4 хв
5 хв
-20
-40
HR
ЧСС
SAP
САТ
DA
ДАТ
P
Cardiovascular Adjustments
to Exercise
Fetal Circulation

No circulation to lungs



Foramen ovale
Ductus arteriosum
Circulation must go to placenta

Umbilical aa., vv.
Adult remnants of fetal circulation
Adult
Fetus
Fossa ovale
Foramen ovale
Ligamentum arteriosum
Ductus arteriosus
Medial umbilical
ligaments
Umbilical aa.(within fetus)
Round ligament
Umbilical v.(within fetus)
(ligamentum teres) of liver
Ligamentum venosum
Ductus venosus
Medial umbilical ligament
Umbilical cord (leaving fetus)
Hepatic Portal System
Thank you!