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Rapid Control of Arterial Rapid Control of Arterial Pressure by Nervous Pressure by Nervous
SystemSystem
By:By:
M. Rasjad IndraM. Rasjad Indra
Lab. Ilmu Faal FK UNIBRAWLab. Ilmu Faal FK UNIBRAW
Pengendalian sirkulasi oleh sistem Pengendalian sirkulasi oleh sistem sarafsaraf
Peran sistem saraf dalam pengendalian Peran sistem saraf dalam pengendalian aliran darah lokal aliran darah lokal sangat kecil.sangat kecil.
Sistem saraf lebih berperan pada fungsi Sistem saraf lebih berperan pada fungsi global dalam hal:global dalam hal:
1.1. Pendistribusian darah ke area tubuh tertentuPendistribusian darah ke area tubuh tertentu
2.2. Kekuatan pompa jantungKekuatan pompa jantung
3.3. Pengendalian cepat tekanan darah Pengendalian cepat tekanan darah
Three Major Changes Three Major Changes
If sympathetic nervous system are stimulatedIf sympathetic nervous system are stimulated1.1. Almost all arterioles are constrictedAlmost all arterioles are constricted
• Increases the total peripheral resistanceIncreases the total peripheral resistance
2.2. The veins especially & other large vessels are The veins especially & other large vessels are strongly constrictedstrongly constricted• Increases venous return Increases venous return increase cardiac out put increase cardiac out put
(Starling Law)(Starling Law)
3.3. The heart enhancing cardiac pumpingThe heart enhancing cardiac pumping• Increases heart rateIncreases heart rate• Increases cardiac contractilityIncreases cardiac contractility
Anestesi spinal menyebabkan penurunan tekanan darah akibat hilangnya tonus vasomotor
Reflex Mechanism for Maintaining Reflex Mechanism for Maintaining Normal Arterial PressureNormal Arterial Pressure
Baroreceptor Reflexes:Baroreceptor Reflexes:– The receptors: Baroreceptors or PressoreceptorsThe receptors: Baroreceptors or Pressoreceptors
Located in the wall of several of large systemic Located in the wall of several of large systemic arteriesarteriesSinus caroticus Sinus caroticus n. Hering n. Hering n. Glossopharyngeus n. Glossopharyngeus tr. Solitarius tr. Solitarius Med. Oblongata.Med. Oblongata.Arcus aortae Arcus aortae n. Vagusn. Vagus
– The Response: Feedback signals to reduce The Response: Feedback signals to reduce arterial pressurearterial pressure
Vasodilatation of the veins and arteriolesVasodilatation of the veins and arteriolesDecreased heart rate & the strength of heart Decreased heart rate & the strength of heart contractioncontraction
Efek perubahan tekanan arteri (ΔP) terhadap perubahan transmisi impuls n. Hering dari sinus Caroticus (ΔI)
Baroreseptor lebih merespons perubahan tekanan daripada tekanan stasioner
Penjepitan a. carotis communis menyebabkan peningkatan tekanan arteri (MAP), pelepasan jepitan menurunkan tekanan arteri
Function of Baroreceptor ReflexFunction of Baroreceptor Reflex
During changes in Body PostureDuring changes in Body Posture– To maintain relatively constant arterial To maintain relatively constant arterial
pressure in the upper bodypressure in the upper body
Pressure BufferPressure Buffer Function Function– Opposes either Opposes either increasesincreases or or decreasesdecreases in in
arterial pressure.arterial pressure.
Unimportance of Baroreceptor System for Unimportance of Baroreceptor System for Long RegulationLong Regulation– The resetting of baroreceptor systemsThe resetting of baroreceptor systems
Pencatatan tekanan darah selama 2 jam pada kondisi NORMAL (gambar atas) dan pada beberapa minggu setelah DENERVASI sinus caroticus dan Sinus aorticus
Frekuensi distribusi MAP selama 24 jam pada anjing NORMAL dan beberapa minggu setelah denervasi baroreseptor
Chemoreceptors Reflex:Chemoreceptors Reflex:– The receptors sensitive to:The receptors sensitive to:
Lack of oxygens; COLack of oxygens; CO22 excess and H excess and H++ excess. excess.
Located in the wall of small arteries; Carotid Bodies & Aortic Located in the wall of small arteries; Carotid Bodies & Aortic Bodies.Bodies.
– Not a powerful control in a normal arterial pressure Not a powerful control in a normal arterial pressure rangerange
Important in below 80 mmHgImportant in below 80 mmHg
Low-pressure Receptors:Low-pressure Receptors:– Stretch receptorsStretch receptors– Located in the wall of: Pulmonary arteries & AtriumLocated in the wall of: Pulmonary arteries & Atrium– Role: to minimize arterial pressure changes in Role: to minimize arterial pressure changes in
response to changes in blood volume.response to changes in blood volume.
Reflex Mechanism for Maintaining Normal Reflex Mechanism for Maintaining Normal Arterial Pressure (Cont.)Arterial Pressure (Cont.)
Volume Reflex (Volume Reflex (Atrial Reflex that Activate the KidneyAtrial Reflex that Activate the Kidney))– Stimulation: Stretch of the atriaStimulation: Stretch of the atria– Response: Response:
1.1. Dilatation of the afferent arteriole in the kidneyDilatation of the afferent arteriole in the kidney
2.2. To Hypothalamus To Hypothalamus Decrease ADH secretion Decrease ADH secretion
3.3. Release of Atrial Natriuretic Peptide (ANP)Release of Atrial Natriuretic Peptide (ANP)
The Bainbridge ReflexThe Bainbridge Reflex– Stimulation: Stretch of the atriaStimulation: Stretch of the atria– Response: n. Vagus Response: n. Vagus Med. Oblongata Med. Oblongata Increase the Increase the
heart rate & strength of the heart contractionheart rate & strength of the heart contraction
Reflex Mechanism for Maintaining Reflex Mechanism for Maintaining Normal Arterial Pressure (Cont.)Normal Arterial Pressure (Cont.)
CA
CI
HIGHER CENTER
VASOMOTORCENTERCI CA
JANTUNG
SV Hr
C.O.PX
TPR
“Blood Pressure”O2
H
CO2
PH
CHEMORECEPTOR
+
VCVD
+
“Baroreceptor”
-
BARORESEPTORCONTROL “Blood Pressure”
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