Physiology of Cardiovascular System

Physiology of Cardiovascular System
Cardiovascular system (‘Rasavaha Srotas’) originates atheart and ten great vessels attached to it(Ca. Vi. 5/7). Ten vessels may beindicating two venae cavae (superior and inferior), one aorta, four pulmonaryveins, one pulmonary trunk and two coronary arteries- as all these are directlyconnected to heart.

Contents of Cardiovascular Compartment: The term ‘Rasa’stands for all circulating fluids in the body including the fluid portion ofblood (Cakrapānhi on Ca.Ci. 15/36). ‘Rasa’ is alsothe minutest and essential fraction of properly digested food. Heart is thesite for this ‘Rasa’ (Su. Sū. 14/3). This ‘Rasa’ circulates in the body alongwith ‘Rakta’ (Ātañkadarpan a on Mā.Ni. 33/4). Ten great blood vessels connected to heart carry the ‘RasātmakaOjas’, on which the whole life processis dependent (A.H. Śā. 3/18). From the above references it is clear that threemajor substances circulate in the cardiovascular compartment- the first one is ‘Rasa’-the liquid nutrient portion of blood (Plasma); the second substance is ‘Rakta’,the oxygen- carrying red material(RBCs); and the third one is ‘Ojas’- the white substance that is responsiblefor immunity (WBCs).

Autonomic Control of Heart: ‘
Vyāna Vāta’ is responsible for the forceful ejection of‘Rasa Dhātu’ from the heart that later circulates all over the body to performits function of providing nutrition (Ca. Ci. 15/36 and Su. Ni. 1/17).

Cardio Vascular System is a Closed Circuit:
‘Rasa’ is ejected out of the heart. It is then carried toall parts of the body. The blood vessels called ‘Sirās’ bring it back to theheart (Bh.Sū. 21).

Structure and Functioning of Heart:
Appearance of heartis similar to that of an inverted bud of lotus. When the individual is ‘awake’,this lotus blossoms forth and when he is ‘asleep’, it closes up (Su. Śā. 4/32).The narrow apex of the heart is directed downwards and broader base is directedupwards when the individual is standing. This observation is reflected in thisexplanation saying that the heart looks like an inverted bud of lotus. To indicate‘life’ and ‘death’, the terms ‘awake’ and ‘asleep’ are often used in Sanskritliterature. So, eaning of this statementis that functioning of heart continues till the death of an individual.

Mean Flow Velocity of Blood:
The manner, in which ‘Rasa’ moves all over the body, is exactlysimilar to the manner in which sound, fire and water move (Su.Sū. 4/16). As perthe view of different commentators, velocity with which sound moves is greaterthan that of fire and the velocity of fire is greater than that of water.Therefore, it can be said that this is the explanation of the mean flow velocity of blood which is maximum in theaorta and minimum in the capillaries. This is because the smallestcross-sectional area, which receives the entire output of the blood from heart,is aorta and accordingly, the mean flow velocity is highest in that vessel.

Theories for Microcirculation

‘Kedārī – Kulyā Nyāya’: This theory describesdifferent tissues as different fields, which receive water through differentchannels, which in turn, are connected to a big reservoir of water. Nutrientfluid in this case is ‘Rasa’, which nourishes all tissues through specific channels.This theory explains the importance of pressure-gradient, which determines the flowof fluid into the tissue-spaces as this is similar to the movement of water inthe direction of gravitational force in the above example (Cakrapānhi on Ca.Ci. 15/16-17).

‘Khale- Kapota Nyāya’: This theory explains theauto-regulation of blood flow by tissuefactors.Blood flow to each tissue isregulated depending on the metabolic needs of the particular tissue. Theexample given to explain this theory is that of different pigeons, picking upthe grains from the same field and then returning to their original places.Here, the choice regarding the amount of grains purely depends on the need ofthe individual pigeon (Cakrapānhi on Ca.Ci.15/16-17).

Physiology of Hemopoietic System
The roots of Hemopoietic system are explained to be Liverand Spleen (Ca.Vi. 5/. Role of liver and spleen in the functioning ofhemopoietic system is very important. RBC synthesis occurs in liver and spleenin between 3rd and 5th month of intrauterine life. Liver
stores some important hemopoietic factors like Vitamin B-12,folic acid and iron. It produces many clotting factors also. Cells ofmonocyte-macrophage system destroy RBCs in the spleen after they complete theirlife span.

Role of Bone Marrow:
In the cavities of larger bones ‘Majjā’ is present whereasin the smaller ones it is ‘Sarakta Meda’(Su. Śā. 4/10). This ‘Sarakta Meda’ isindicative of Red bone marrow.

Formation of Bilirubin:
Byproduct ofmetabolism of ‘Rakta’ is ‘Pitta’.(Ca. Ci. 15/18). This ‘Pitta’ is Bilirubin,the product of hemoglobin metabolism. This is formed in the monocytemacrophage system,mainly in the spleen.

Hyperbilirubinemia:
When the ‘Pitta’exceeds its normal levels, there is manifestation of symptoms like yellowishdiscoloration of feces, urine, eyes and skin (A.H. Sū. 11/7). When the totalserum bilirubin level exceeds 2mg/dl, usually there is manifestation ofclinical jaundice.

Endocrinology and Metabolism
Normal vision, normal appetite, normal thirst, normal bodytemperature, normal softness of body parts, normal complexion, normalnourishment and normal intellectual functions- are all the functions of normal‘Pitta’ (Ca.Sū. 18/50). These parameters are good indicators of many ofmetabolic activities. For example, impaired Vitamin A metabolism leads toproblems in vision. In hyperthyroidism there is excessive hunger and increasedbody temperature. In diabetes mellitus there is polydypsia and polyphagia. Inhypothyroidism, normal softness of the skin and subcutaneous tissue is lost. InAddison’s disease the excessive pigmentation leads to alteration in thecomplexion. In Cretinism, the mental growth is retarded.

Intermediary Metabolism:
The five ‘Agnis’ viz., ‘Bhaumāgni’, ‘Āpyāgni’, ‘Āgneyāgni’, ‘Vāyavyāgni’and ‘Nābhasāgni’ are the causative factors for the metabolism of five groups ofrespective ingredients of the food. Normally, the specific tissues arenourished from those ingredients of food which are similar to the respectivetissues in their composition (Ca. Ci. 15/ 13-14). The function of ‘Bhūtāgnis’is to metabolize the ingredients of food and to ‘sort them out’ into fivegroups depending on the predominance of particular ‘Mahābhūta’. These functionsof ‘Bhūtāgnis’ can be explained through the functions of liver. Basically,whatever is digested and absorbed has to reach liver first and metabolicinterconversion of the substances occurs there. For example, plant-derived aminoacids can be used to synthesize human proteins, glucose can be converted intoglycogen or in to fat, amino acids can be converted into glucose – and so on.‘Sorting out’ of different substances occurs in liver and that is the functionof ‘Bhūtāgnis’ too. After the digestion in gastro intestinal tract is over, theingredients of food (‘Rasas’) undergo metabolism once again. This metabolicend- product is called ‘Vipāka’(A.H. Sū. 9/20). This indicates that ‘Vipāka’ isthe end product of the action of ‘Bhūtāgnis’. In other words to say,‘Bhūtāgnipāka’ itself produces ‘Vipāka’ and therefore, ‘Vipāka’ in general,stands for intermediary metabolism.

Metabolism at the Tissue-Level:
Each tissue derivesits nutrition through the activity of so called ‘Dhātvagni’. Metabolism attissue level is dependent on these ‘Dhātvagnis’. Some part of the tissuebecomes supportive whereas some part becomes waste after the metabolism at thislevel (Ca. Ci. 15/15).

Different Metabolic Pathways at Cellular level- ‘Kshīra- Dadhi Nyāya’:
This theory speaks oftransformation of one substance into another in a particular order through the activityof respective ‘Dhātvagnis’. The example given to state this theory is that of transformationof milk into curd, curd into butter and butter into ghee in the particularorder (Cakrapānhi on Ca. Ci. 15/16-17). All metabolicpathways like Glycolytic pathway, Kreb’c TCA cyce, β- oxidation pathway,Urea cycle, Gluconeogenesis etc. could be the examples for this type oftransformations with the involvement of their specific enzymes.

Metabolic State of a Tissue: ‘Jathharāgni’, though is situated in its own site, has its fractions situatedat the tissues. If these fractions become over active, there will be ‘Kshaya’ (Catabolism) of‘Dhātu’ and if they become depressed, there will be abnormal ‘Vrhddhi’ of ‘Dhātu’ (A. H. Sū. 11/34)
In fact, severalclassical hemocrine hormones determine the metabolic state of a tissue. Forexample, many amino acids circulating in the blood stream are taken up by musclesand they are utilized to synthesize muscle proteins under the influence of thyroxin, growth hormone, insulin andtestosterone. So, these hormones can be grouped under ‘Māmhsa Dhātvagni’. If thyroid hormone levels increase in the blood, thereis muscle wasting and loss of weight due to ‘MāmhsaKshaya’. Similarly, Calcitonin, parathormone and Vitamin D3 can beincluded under ‘Asthidhātvagni’. In hyper parathyroidism, osteoporosis or ‘Asthikshaya’ is evident.


Physiological Effects of Normal Metabolism:
At the end of ‘Bhūtāgnipāka’, three groups of etabolites areformed: ‘Madhura’, ‘Amla’ and ‘Kathu’. ‘Guru’ (Heavy)is another name for ‘Madhura’ whereas ‘Laghu’ (Light) includes remainingtwo i.e., ‘Amla’ and ‘Kathu’. These groups are called‘Vipākas’. ‘Madhura Vipāka’ promotes the synthesis of reproductive factor andpromotes the excretion of feces and urine. ‘Amla Vipāka’ opposes the formationof reproductive factor and promotes theexcretion of urine and feces. ‘Kathu Vipāka’, on the otherhand, opposes the synthesis of reproductive factor and causes retention ofurine and feces. Effects of ‘Vipāka’ on the formation of ‘Doshas’ are as follows: ‘Madhura Vipāka’ promotes ‘Kapha’, ‘AmlaVipāka’ promotes ‘Pitta’ and ‘Kathu Vipāka’ promotesthe formation of ‘Vāta’(Ca. Sū. 26/61,62). Effects of this stage ofmetabolism may be of manifold. Some products may be used for tissue synthesiswhereas the others may be used for the purpose of energy. Anabolic effects maybe called ‘Guru’ and catabolic ones, ‘Laghu’. Again, ‘Doshas’ synthesized here are of ‘Dhāturūpi’ type (‘Malarūpi Doshas’ areformed during ‘Avasthāpāka’).

Importance of Normal Metabolism:
‘Agni’ itself ispresent in the body in the form of Pitta. When it is normal, it performs thefunctions like maintenance of normal digestion, normal vision, normal bodytemperature, normal complexion, valor, happiness and nutrition. When it isabnormal, all these functions also will be abnormal (Ca.Sū. 12/11). Otherfunctions of endocrine system are described under the functions of ‘Pitta’.

Concept of ‘Pitta’:
‘Pitta’ includes allthose factors responsible for digestion and metabolism. For all practicalpurposes, ‘Agni’ & ‘Pitta’ are to be considered as identical entities (Su.Su. 21/9, Ca.Sū. 12/11).

‘Pācaka Pitta’:
‘Pācaka Pitta’ isequivalent to ‘Jathharāgni’ (A.H. Sū. 12/11). As itsfunctions suggest, all enzymes responsible for digestion along with allgastrointestinal hormones and all local hormones of G.I.T. are to be includedin it.

‘Rañjaka Pitta’: It is responsible for synthesis of‘Rakta’. It is situated in stomach (‘Amāśaya’) according to Vāgbhatha and the sites are liver and spleen according to Suśruta. Gastric intrinsic factor is the bestcandidate to represent Vāgbhatha’ s view, as itis required for the absorption of Vitamin B12, which in turn is neededfor DNA synthesis of RBC precursors in bone marrow.

‘Bhrājaka Pitta’: As is known, pigmentation of skinis under the control of some hormones like ACTH & MSH from anteriorpituitary. Some enzymes in the skin responsible for the metabolism of certaindrugs applied topically also can be considered under ‘Bhrājaka Pitta’ alongwith the hormones controlling pigmentation.

‘Sādhaka Pitta’: All functions ascribed to this‘Pitta’are of cerebrum, limbic system, hypothalamus and other CNS structures.For motivation and other psychosocial behaviors Norepinephrine is a veryessential neurotransmitter in the brain. Incidentally, it also acts on heart asa cardiac stimulant. During emergency situations it is released from adrenalmedulla and it helps for “fight or flight phenomenon”.

‘Alocaka Pitta’: This is said to be responsible fornormal vision. Photosensitive chemicals in the eye, called Photo-pigments andthe whole process involved in photochemistry of vision can be represented by‘Alocaka pitta’. Also, neurotransmitters involved in the visual pathway can beincluded under this.