Cardio 2 L8 ( Cradiac Regulation ) Flashcards
How is the heart regulated?
By two levels each of this levels may relazied neural , humoral or some other mechanism
What is the two levels that regulated the heart ?
-1- intercardiac : relating to the mechanism which are appears and situated within the heart And its 4 mechanism: 1-interacellular 2-extracellular 3-neuronal 4- humoral
-2- extracardiac : relating to the mechanism, tissue , cells , organs which are all involved directly or indirectly in the regulation of heart and situated outside the heart
And its 2 mechanism:
1- neuronal
2- humeral
What is the intercellular level includes ?
1- Atrophy
2-hypertrophy
3- direct dependence of strength on the rate
4- frank starling law
Explain the atrophy and hypertrophy of the intercellular level ?
- hypertrophy : its the enlargement of myocard from the increase in size of its cells as a result of increasing a number of contractile proteins ( actin and myosin ) or cardiomyocytes in whole
- atrophy : its opposite process waste away , especially as a result of contractile proteins degeneration or cardiocytes number decreasing
Explain the direct dependence if strength in contraction frequency ( intercellular )
- the high frequency of the heart contraction dose not allow its sarcomeres ( during diastole ) to pump the calcium from the sarcoplasm of the calcium depots
- thus each following contraction ( in systole) begins in condition of increasing of calcium contraction in sarcoplasm
- so the higher amount if calcium results in the higher amount of energy in each if the sarcomere, this increases the myocardium activity
Explain the frank starling law ( intercellular)
- the strength of the contraction of muscle ( cardyocytes ) is directly promotional to an expansion of this muscle during its previous relaxation
What is the physiological importance of frank starling mechanism ?
Its lies mainly in the maintaining left and right ventricular output equality
Explain the extracellular regulation
Syncytium ( intercardiac level )
- syncytium : Its mean tissue with cytoplasmic continuity between adjacent cells
- Cardiac muscle is like a physiological syncytium since there is no continuity of cytoplasm and the muscles fibres are separated from each other by cell membrane
- the membrane of adjacent muscles fibres fuse together to form -gap junctions
- so extracellular regulation realizes due to a nexus : special electrical gaps of cardiomyocytes which have a low threshold level , if at any reason nexuses change there threshold so an excitability of the whole myocardium will change oppositely , and in appropriate manner will change the activity of the heart
- extracellular regulation realizes due to a nexus ( yes or no )
Yes
Explain the syncytium in human
Syncytium in human heart have two portion
1- syncytium of atria
2- syncytium of ventricles
Both portions if syncytium are connected by a thick non-conducting fibrous ring called - atrioventricular ring - in organism only the heart works as the functional syncytium , heart is tissue which mean a group of cells but works like all together one cell
Explain the intercardiac neuronal regulation
- A bainbridge reflex is an increasing of strength of the left ventricle upon a increase of venous return to a right atrium, and its carried out by cardio-cardiac reflex
- the bainbridge reflex is triggered when the stretch receptor in the atria are triggered- thats mean that there is an increased level of venous blood return
- So higher the venous return to right atrium higher contraction of left ventricle
Explain what is the bainbridge reflex and baroreceptor reflex and what is the relationship between them
- bainbridge reflex: is one of the intercardiac neural mechanism
- baroreceptor reflex: its one of the extracadiac mechanism
- The relationship between them is antagonistically thats mean if venous blood pressure in atrium is much changing the bainbridge reflex is dominant , and if for example the carotid artery baroreceptor indicates much arterial blood pressure chaining thats mean baroreceptor is dominant
Explain the inercardiac humoral regulation
1- accumulation of metabolites during intensive heart working like : Co2,H+,Lactic acid , H2CO3
2- blocking of à-adrenoreceptor
3-cardiac stimulation
What is the 4 greek terms to describe key physiological properties of the heart ? And when its discovered and by whom ?
Its discovered by Engelmann in 1897
- 1-inotropy
- 2-chronotropy
- 3-dromotropy
- 4-bathmotropy
Explain the inotropy and what its mean in greek
Inotropy : its the strength of contraction pertaining to the force or energy of muscular contraction particularly those of the heart
Inos = fibres , trope - turning
Explain the chronotropy and what its mean in greek
Chronotropy its the frequency of the contraction heart rate or pulse
Its mean in greek ( chrono = reffing to time )
Explain the dromotropy and what its mean in greek
Dromotropy its a conduction an electrical impulse , conductivity of AP
Means in greek ( dromos - running )
Explain the bathomotropy and what its mean in greek
Its the excitation, chrechtrazing a threshold level
In greek mean ( bathmos - step or threshold )
Explain the types of the heart work
And explain the difference between them
We have two types 1- mechanical work - inotropy -chronotropy 2- electrical work -dromotropy -bathomotropy
- mechanical for pumping the blood
- electrical to provide the mechanical activity
And all these type of works can be increasing or decreaseing
Ex if we are speaking about negative inotropy thats mean the contraction getting weaker
What is carrying the extracardiac regulation ?
- humoral
- neuronal
Explain the neuronal regulation of heart
Extracardiac
- Vital centres of medulla oblongata have both
1-Cardioaccelerator center :which activities sympathetic neurones that increases the HR ( heart rate )
2-cardioinhibatory centre : which activate parasympathetic neurons that decreases the HR
— cardiac center receive input from higher centre which is the hypothalamus monitoring the blood pressure and dissolved gas concentration
The afferentation for this reflex forms from
1- the circulatory system
2- other body parts
Explain the parasympathetic neuronal regulation of the heart
- Parasympathetic centres locate only in medulla oblongata , there influences are realising by vagus which innervates nods of the heart conductive system and contractile myocardium of auricles
— Parasympathetic innervation vagus and Dorsal nucleus ,
- preganglionic fibres of vagus arises from the neurons of C.I.C ( cardiacinhibatory center ) they reach the heart as pregangiloinc fibres and relay in terminal ganglia present in the substance of the atrial muscle particularly the nodal tissue
- postganglionic fibres supply sina atrial node and Atrioventricular node and main stem of the Atrioventricular bundle and atrial muscle, coronary blood vessels .
- vagus nerve dont supply the ventricles or branches of Atrioventricular node and purkinje fibres
Explain the sympathetic neuronal regulation of the heart
- Sympathetic centers lay both in medulla oblongata and in upper thoracic segments of spinal cord , and its fibres innervate nodes of conductive system of the heart and contractile cardiomyocytes
- its begins at C.A.C ( cardiac accelerator center ) in medulla oblongata near CIC ( cardiacinhibatory center ) the axons of there neurons descend in the white matter of the spinal cord , and relay at L.H.C ( latral gray column ) of upper 5 thoracic segments
- pregangiloinc fibres of lateral horn pass in sympathetic chain and ascend upward to relay in the three cervical sympathetic ganglia ( sup , inf , mdl , cervical sympathetic ganglia)
- postgangiloinc fibres pass from the ganglia to the heart and innervating all the structure including the ventricles
Explain the vagus nerve in the neural heart regulation of the heart
(Extracardiac)
- the vagus nerve are cardiac inhibitory nerve , when the vagus is stimulated the activity of the heart is inhibited due to a suppression of conductive system nodes (SA,AV) activity, the inhibitory action of the vagus is brought by :
1-negative bathmotorpic effect : which decreasing excitability of heart muscle
2-negative dromotropic effect : which decreases heart conductibility
3- negative chronopic effect : decreases the heart rate
4-negative inotropic effect : decreases strength of heart contractions - vagus suppresses all of it ، these 4 influences may relies separately or combined in any variations
Explain the sympathetic nerve in the neural heart regulation of the heart
(Extracardiac)
- the sympathetic nerve are accelerator nerves these fibres stimulates the (SA , AV nodes , also the contractile muscles of the auricles and the ventricles
By :
1- positive bathmotropic effect : increasing excitability of heart muscle
2- positive dromotropic effect : increasing heart rate
3- positive chronotropic effect : increasing heartbeat
4- positive inotropic effect : increasing strength of heart contractions - the sympathetic stimulates all
What is the Extracardiac humoral regulation of heart activity realizes by ?
1-metabolites
2- Gases
3- electrolytes
4- hormones
Explain the Extracardiac humoral regulation by metabolites
Its realizes the same way in the intercardiac which
1- accumulation of metabolites during intensive heart working (Co2,H+,lactic acid,H2Co3)
2-blocking of a-adrenoreceptor
3-cardiac stimulation
But the difference between them its from where these substances got to the heart
1- if its was appeared inside the heart and stimulate it activity then its intercadiac regulation
2-if the metabolite appeared in some other organ like contracted striated muscle or digestion system and got to the heart with blood flow then it will be Extracardiac regulation
Explain the Extracardiac humoral regulation by gases O2
- For the O2 Hyperoxia : occurs when cells or tissue or organ are exposed to an excess supply of oxygen or higher then normal partial pressure of oxygen
- its stimulates by oxygen of chemoreceptors of vesicular reflexoginic zones and the resulting of suppression of SyNS and activation of PNS
- and its has negative effects in the heart
Explain the Extracardiac humoral regulation by gases Co2
For the Co2 Hypercapnia : its condition of abnormally elevated carbon dioxide levels in the blood
- Its also known
( hypercarbia , Co2 -retention)
- stimulation by Co2 of chemoreceptors of vascular reflexogainc zones and its result activtion of SyNS and decreasing of PNS tonus .
- it has positive chronotropic effect
Explain the Extracardiac humoral regulation by gases
- the Extracardiac humoral regulation the gases influence the vascular reflexogainc zones .
- the chemoreceptors of vascular reflexogainc zones registrate changes of o2 and Co2 concentration and send this afferentation to centres of VNS thus forming reflexes on heart
What is the main zones of vascular reflexogainc zones?
And what the reflexogainc zone receptors?
The main two zones are 1- Sino-carotid zone 2- aortal arch zone The vascular reflexogainc zone has 2 types of receptors 1-Baroreceptors 2- chemoreceptors
Explain the Extracardiac humoral regulation by electrolytes ( sodium )
-Normal sodium ion contraction in blood is 135 - 145 mmol/l
-sodium has positive chronotropic action because it takes part in depolarisation
The low level of sodium ion in body fluids reduces the electrical activity if cardiac muscle and electrocardiogram shows low-voltage waves
- condition of sodium in body
— Hypernatremia : tachycardia - is a heart rate that exceeds the normal resting rate
—Hyponatremia : bradycradia - decreasing of heart rate under 60 beats per minute
Explain the Extracardiac humoral regulation by electrolytes ( potassium )
- normal potassium ion contraction in blood is about 3.5-5 mmol/L
- potassium hall all 4 negative action
- negative inotropic effect -
- negative chronotropic effect -
- negative dromotropic effect
- negative bathmotropic effect
— condition of potassium : - hypokalaemia : has some low influence of increasing the sensitivity of heart muscle, but mainly results in critical changes in heart activity
-hyperkalemia : may be dangerous in its higher concentration changes
1- resting membrane potential is leading to hyperpolarazation
2-Excitability of the cardiomyocytes decreases
3- ventricles may get into fibrillation
4- stoppage of the heart in diastole
Explain the Extracardiac humoral regulation by electrolytes ( calcium)
—hypercalcemia :
1- improves electromechanical conjugation by : activates phosphorylase ATP dissociation output of an energy for myosin heads turning / positive inotropic effect
2-increasing of myocardium depolarisation positive chronotropic effect
3- hypercalcemia may result in stoppage of the heart in systole phase this happens cause a lot of calcium appeared in sarcoplasm
—hypocalcemia : reducing diastolic depolarisation which decreases the excitability of heart muscle Which is negative bathmotropic effect
—-an overdose of calcium drugs which are widely used in different medicine areas may be extremely dangerous
Explain the adrenaline hormone effect on heart ?
Adrenaline stimulates B-receptor
- adrenaline and noradrenaline stimulate heat activity and cause positive regulatory effects :
1- positive inotropic
2- positive chronotropic
, it happens because nor-epinephrine component of this hormone increases permeability of cardiac fibre membrane to Na and Ca
We we dont use the phrase ( Extracardiac hormonal humoral regulation)
We should say hormonal regulation
Bcs hormonal regulation is one of the mechanism if Extracardiac humoral regulation, hormones can get the heart only from Extracardiac level and only by blood
Explain the thyroid hormones
-The hormones that secreted by thyroid its the thyroxin
-1-thyroxin increase the sensitivity of the heart to action of adrenaline
-2- and increasing protien synthesis in the heart by stimulation of intercellular enzyme)
— the results of this hormone effect is positive chronotropic effect
Explain the effects of adrenocortical
hormons
They are 2
1- aldosterone: causes increasing of sodium and chlorine in blood and decreasing the potassium, this for producing action potential in the heart
2- cortisol : stimulates gluconeogenisis and increases blood glucose level giving an auditory amount of energy for cardiomyocytes
Explain the effects of islets of langerhans
hormons effect
They are 2
1- insulin : promotes facilitated diffusion of glucose into cells and activate transport of amino acid into cells
2-clucagone : stimulates gluconeogenesis and mobilises fatty acids from adipose tissue
