Cardiac conduction: fish vs. mammals: Difference between revisions

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=Notable bits from PMC:2323757 [http://www.ncbi.nlm.nih.gov/pubmed?term=18650991]=
=Notable bits from PMC:2323757 [http://www.ncbi.nlm.nih.gov/pubmed?term=18650991]=
Great coverage of different heart conduction systems across wide range of organisms
Great coverage of different heart conduction systems across wide range of organisms
[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2323757/?tool=pubmed#__sec1 phylogeny]


#Automaticity of heart rhythm can be neurogenic or myogenic depending on the organism
#Automaticity of heart rhythm can be neurogenic or myogenic depending on the organism
#'''Invertebrates''' have been proven to be outside the general concept of the myogenic origin of the heartbeat; pacemaking of a primitive heart originating from a neural ganglion placed behind the dorsal heart wall was documented in some tiny crustaceans ranked among stomatopods – Stomatopoda – for example, Squilla mantis or Squilla oratoria (9). Immediate heart arrest was demonstrated after the neural connection between the ganglion cordis and the heart muscle was cut (10). On the other hand, there was no heart innervation found in other primitive crustaceans – Branchiopoda (eg, Daphnia) – and their heart automaticity is considered to be myogenic.
#'''Invertebrates''' have been proven to be outside the general concept of the myogenic origin of the heartbeat; pacemaking of a primitive heart originating from a neural ganglion placed behind the dorsal heart wall was documented in some tiny crustaceans ranked among stomatopods – Stomatopoda – for example, Squilla mantis or Squilla oratoria (9). Immediate heart arrest was demonstrated after the neural connection between the ganglion cordis and the heart muscle was cut (10). On the other hand, there was no heart innervation found in other primitive crustaceans – Branchiopoda (eg, Daphnia) – and their heart automaticity is considered to be myogenic.
#Myoendothelial cells of '''tunicates (primitive chordates)''' are electromecahnically coupled and endowed with automaticity.  There is no dominant pacemaker.  The locus of the temporary dominant automaticity is wandering – the pacemaking centre switches from one heart tube pole to another. After every few beats (which are variable), a new centre from the other end of the tube takes over the pacemaking activity. Electrical impulses and consequently peristaltic waves spread from the place of origin along the tube. They run in turns toward one pole and then the other pole, and thus, the bloodstream direction varies over time. There is no organized conducting system in tunicates (12), but myocytes specialized for conduction have been detected in the heart tube of Ciona species (13).
#Myoendothelial cells of '''tunicates (primitive chordates)''' are electromecahnically coupled and endowed with automaticity.  There is no dominant pacemaker.  The locus of the temporary dominant automaticity is wandering – the pacemaking centre switches from one heart tube pole to another. After every few beats (which are variable), a new centre from the other end of the tube takes over the pacemaking activity. Electrical impulses and consequently peristaltic waves spread from the place of origin along the tube. They run in turns toward one pole and then the other pole, and thus, the bloodstream direction varies over time. There is no organized conducting system in tunicates (12), but myocytes specialized for conduction have been detected in the heart tube of Ciona species (13).
#'''Lancelet or amphioxus (Cephalochordata)'''These chordates differ essentially from tunicates, because they possess a head and their circulation system is closed, as in vertebrates. On the other hand, there is no developed heart at all. Instead, some vessels capable of contracting act as a pump. The main pump function relies on the aorta ventralis, but some other vessels produce autonomous contractions as well, such as the vena subintestinalis, vena portae and venae hepaticae. The walls of contracting vessels are coated by a single layer of myoepithelial cells and, therefore, differ from the structure of vessels in vertebrates. Vessels contract in sequence and thus actuate the circulation. Their co-ordination, however, is poor, sometimes even chaotic. Countercurrent contractions and flow are frequent. No specialized pacemaker cells or organized conducting system have been found in lancelets (14).
#'''Lancelet or amphioxus (Cephalochordata)'''These chordates differ essentially from tunicates, because they possess a head and their circulation system is closed, as in vertebrates. On the other hand, there is no developed heart at all. Instead, some vessels capable of contracting act as a pump. The main pump function relies on the aorta ventralis, but some other vessels produce autonomous contractions as well, such as the vena subintestinalis, vena portae and venae hepaticae. The walls of contracting vessels are coated by a single layer of myoepithelial cells and, therefore, differ from the structure of vessels in vertebrates. Vessels contract in sequence and thus actuate the circulation. Their co-ordination, however, is poor, sometimes even chaotic. Countercurrent contractions and flow are frequent. No specialized pacemaker cells or organized conducting system have been found in lancelets (14).
#'''Fish'''  As in all higher vertebrates, the heart of the fish is segmented into clearly defined chambers. The four serially grouped chambers are the sinus venosus, atrium, ventricle and truncus arteriosus or bulbus arteriosus in teleosts. There has been no septation of the atrium or ventricle, thus, they have a single atrium and a single ventricle (5,16)

Revision as of 17:53, 17 June 2011

Back to: cardiac conduction

Birds:

Many avian species develop an AV-ring which plays a role similar to that of the mammalian AV-node (Szabo et al. Anat Rec. 1986 May;215(1):1-9. PubMed PMID:3706789.) [[1]]

Steps in CCS develoment in zebrafish:

From Genetic and physiologic dissection of the vertebrate cardiac conduction system. PLoS Biol. 2008 May 13;6(5):e109. PubMed PMID: 18479184; PubMed Central PMCID: PMC2430899. [[2]]

  1. Initially, a linear conduction travels across the heart tube from the sinus venosus to the OFT (20–24 hours postfertilization (hpf)).
  2. next, a significant AV conduction delay develops during cardiac chamber formation (36–48 hpf)
  3. as the heart loops and develops ventricular trabeculations (72–96 hpf), an immature fast conduction network develops within the ventricle
  4. finally, this fast conduction network fully matures to an apex-to-base activation pattern when the ventricular apex has

formed.

Notable bits from PMC:2323757 [3]

Great coverage of different heart conduction systems across wide range of organisms

phylogeny

  1. Automaticity of heart rhythm can be neurogenic or myogenic depending on the organism
  2. Invertebrates have been proven to be outside the general concept of the myogenic origin of the heartbeat; pacemaking of a primitive heart originating from a neural ganglion placed behind the dorsal heart wall was documented in some tiny crustaceans ranked among stomatopods – Stomatopoda – for example, Squilla mantis or Squilla oratoria (9). Immediate heart arrest was demonstrated after the neural connection between the ganglion cordis and the heart muscle was cut (10). On the other hand, there was no heart innervation found in other primitive crustaceans – Branchiopoda (eg, Daphnia) – and their heart automaticity is considered to be myogenic.
  3. Myoendothelial cells of tunicates (primitive chordates) are electromecahnically coupled and endowed with automaticity. There is no dominant pacemaker. The locus of the temporary dominant automaticity is wandering – the pacemaking centre switches from one heart tube pole to another. After every few beats (which are variable), a new centre from the other end of the tube takes over the pacemaking activity. Electrical impulses and consequently peristaltic waves spread from the place of origin along the tube. They run in turns toward one pole and then the other pole, and thus, the bloodstream direction varies over time. There is no organized conducting system in tunicates (12), but myocytes specialized for conduction have been detected in the heart tube of Ciona species (13).
  4. Lancelet or amphioxus (Cephalochordata). These chordates differ essentially from tunicates, because they possess a head and their circulation system is closed, as in vertebrates. On the other hand, there is no developed heart at all. Instead, some vessels capable of contracting act as a pump. The main pump function relies on the aorta ventralis, but some other vessels produce autonomous contractions as well, such as the vena subintestinalis, vena portae and venae hepaticae. The walls of contracting vessels are coated by a single layer of myoepithelial cells and, therefore, differ from the structure of vessels in vertebrates. Vessels contract in sequence and thus actuate the circulation. Their co-ordination, however, is poor, sometimes even chaotic. Countercurrent contractions and flow are frequent. No specialized pacemaker cells or organized conducting system have been found in lancelets (14).
  5. Fish As in all higher vertebrates, the heart of the fish is segmented into clearly defined chambers. The four serially grouped chambers are the sinus venosus, atrium, ventricle and truncus arteriosus or bulbus arteriosus in teleosts. There has been no septation of the atrium or ventricle, thus, they have a single atrium and a single ventricle (5,16)