Assalamu alaikum wa rehmatullahi wa barakatuh
It is He, Who has created for you (the sense of) hearing, sight, and heart, little do you thank (Him)! (Surah Mominoon 75)
Say, “It is He who has produced you and made for you hearing and vision and hearts; little are you grateful.”(Surah Mulk 23)
Then He proportioned him and breathed into him from His [created] soul and made for you hearing and vision and hearts; little are you grateful. (Surah Sajdah 9)
First of all the words used in the verses are not “ears” and “eyes”.These are hearing and vision,which are definitely the set of complex mechanisms occurring in these special organs.
Number of structures contributing for the process of hearing,the pinna which collects the sound waves,the auditory canal,
The thin,delicate ear drum formed of 3 delicate layers,supplied by 3 different nerves,
The middle ear, a small area containing 3 bones which help to transmit sound and 2 muscles,one which tenses the tympanic membrane and the other which dampens the loudness,protecting the inner ear.
The bony labyrinth containing 3 semicircular canals,vestibule and cochlea,
The membranous labyrinth containing cochlear duct,utricle and sacule,semicircular ducts,endolymphatic duct and sac.
The maleus is 1.3 times larger than incus,and thus the mechanical advantage of 1.3 is provided,
The areal ratio between the tympanic membrane and the ossicles is 18:1,further helping in amplification of sound.
The phase difference between the oval and rond windows contributing for 4 dB.
The movements of the membrane are most at the periphery and it is where the malleus is attached
The movements of stapes footplate are transmitted to cochlear fluids which are converted to electrical energy by hair cells present in the basilar membrane.
2 types of hair cells,single row of inner hair cells and 3-4 rows of outer hair cells.1 type is afferent and the other is efferent.
The cochlear nerve,superior olivary nucleus,lateral leminiscus,inferior colliculus,medial geniculate body and finally the auditory cortex of the temporal lobe.
Numerous structures and number of complicated mechanisms,we should really be grateful for Our Lord.
It consists of the following: Eye,the nerve fibres,the conducting pathway to the brain,and the whole visual centre in the brain.
The eyes contribute for visualizing the object,the small aperture ie pupil to allow the proper amount of light to pass into the eyes,whose diameter adjusts accordingly,
then the passage of light from the lens which is an elastic structure,again able to adjust accordingly for the image to be focused at retina exactly,
the special color sensors (cones) present in retina which sense colour and the rods which allow one to see well in dark,
and then the formation of the image.
The image from the 2 eyes,allowing stereoscopic vision,the 3 dimensional vision.
Then comes the nerves fibres which carry the signals to the brain,in the form of electric signals,
The optic chiasma,where the impulses form the nasal halves of the right and left eyes ,cross each other to help to form a combined image.The image from the 2 eyes,allowing stereoscopic vision,the 3 dimensional view.
The optic tract and then the Lateral geniculate nucleus,The LGN which is not just a simple relay station but it is also a center for processing.
And the visual cortex,the largest centre in the brain which is for the processing of visual image,the edge and corner detection,the detection of movements,the detection of angles and colors.
The visual association cortex dealing with “what,where and how” for the object,the recognition,identification and categorization of the viewed object.The memory,the instincts,the perception and the conscious as well as subconscious interpretation of the viewed image.
This is really very little about the vision,the special sense given to us by Almighty Allah.
The circulatory system, pulmonary circulation and the systemic circulation for the oxygenation of the deoxygenated blood and then the pumping of the oxygenated blood to the whole body.
The specialized cells: Cardiac muscles and the connective tissue
larger and circumfrentially arranged ventricular myocytes while smaller and haphazardly arranged atrial cells.
The prolonged refractory period of the cardiac action potential.This This prevents tetany from occurring and ensures proper filling time.Substantial atrial to ventricular delay will allow the atria to completely empty their contents into the ventricles; simultaneous contraction would cause inefficient filling and backflow.
ANP present in atrial cells,responsible for a variety of physiologic effects, including vasodilation, natriuresis, and diuresis, actions beneficial in pathologic states such as hypertension and congestive heart failure.
Intercalated discs permitting mechanical and electrical coupling, the gap junctions facilitating synchronous myocyte contraction.
Multi layered valves restricting the flow of blood in specific direction.
The thickness of left ventricular wall helping to pump the blood efficiently.
The specialized conduction system containing of SA node,AV node,Purkenji fibres and Bundle of His.Signals arising in the SA node stimulate the atria to contract and travel to the AV node. After a delay, the stimulus is conducted through the bundle of His to the Purkinje fibers and the endocardium at the apex of the heart, then finally to the ventricular epicardium.
SA node,AV node,Bundle of His and Purkenji firbres, all are able to generate electrical impulses.When 1 system fails the other is there to take its place!
Frank starling law:
The Frank–Starling law of the heart (also known as Starling’s law or the Frank–Starling mechanism or Maestrini heart’s law) states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume) when all other factors remain constant. The increased volume of blood stretches the ventricular wall, causing cardiac muscle to contract more forcefully (the so-called Frank-Starling mechanisms). The stroke volume may also increase as a result of greater contractility of the cardiac muscle during exercise, independent of the end-diastolic volume. The Frank-Starling mechanism appears to make its greatest contribution to increasing stroke volume at lower work rates, and contractility has its greatest influence at higher work rates.This allows the cardiac output to be synchronized with the venous return, arterial blood supply and humoral length without depending upon external regulation to make alterations.(Wikipedia)