Electrochemical systems of CVS Flashcards
What does the neural regulation of cardiovascular system
Autonomic nervous system
What do motor neurons do in ANS
Innervates smooth muscle, cardiac muscle, internal organs and skin
Makes adjustments to ensure optimal support for body activities
What does motor neuron of ANS have as effector
Viscera
What neurotransmitter do somatic motor neurons release in SNS
ACh
Has excitatory effect
What neurotransmitter are released in ANS
Preganglionic fibres release ACh
Postganglionic fibres release noradrenaline or ACh - effect either stimulators or inhibitory
What is the parasympathetic division
Concerned with keeping body energy use low
Largely innervates the internal organs - not he skin
Neurotransmitter = ACh at both ganglionic and effector organs
What is the Sympathetic division
Concerned with high energy use
Promotes adjustments during exercise
Innervates every part of the body
Neurotransmitter = ganglionic is ACh, effector organ neurotransmitter is noradrenaline
What is the sinoatrial node
Auto rhythmic cells in right atrium near entry of the SVC
What is atrioventricular node
Autorhythmic cells near the floor of the right atrium
How are SA and AV nodes connected
Internodal pathways through which electrical activity spreads rapidly
Where is the bundle of His
Wall of septum between ventricles
What does the bundle of His divide into
Left and right branches which continue downwards and divide into many small Purkinje fibres
Which tissue possesses the highest degree of automaticity
SA node
Creates impulses at highest frequency and normally suppresses the other elements
What does the p wave represent
Atrial depolarisation
What is the QRS complex
Ventricular depolarisation
What is the T wave
Indicates ventricular repolarisation
What is the PR interval
Period that shows the delay in AV node
Also represents electrical activity of the atria
QT interval
Represents electrical activity of the ventricles
Phase 0 of SA node
Calcium entry
Threshold reached and AP fires
If currents inactive
Phase 3 of SA
Repolarisation to -60 mV
K+ Current as potassium chsnnels open
How does sympathetic (catecholamines) increase heart rate
Increases slope of pacemaker potential
Increases rate of depolarisation by increased Ca2+ entry
How does parasympathetic (acetylcholine) decrease heart rate
Reduces slope of pacemakers potential
Hyperpolarises pacemaker cell membrane via muscadine receptor
Difference between SA nodal cell and contractile tissue
More negative and stable resting potential
More rapid depolarisation with prominent plateau
Phase 0 of cardiac myocyte
Depolarisation
AP from SA node opens fast Na+ chennels
Large, but transient, increase in Na+ permeability
Accompanied by dramatic reduction in K+ conductance
Phase 1 of cardiac myocyte
Early repolarisation
Fast Na+ channels close
Membrane potential begins to fall
Phase 2 of cardiac myocyte
Plateau
Potential remains positive for ~300 msec
Largely due to opening of voltage-gated slow Ca2+ chennels
Plateau because of Na+ influx from slow Na+ channels and slow leakage of K+ out of the cell keeps potential from rising
Phase 3 of cardiac myocyte
Repolarisation
Intracellular K+ moves down concentration gradient repolarising cell
Repolarisation facilitated by closure of Ca2+ and slow Na+ channels
Phase 4 of cardiac myocyte
Resting membrane potential
Cell repolarised and ready for the next stimulus
What is advantage of having long refractory period
Prevents tetanic contractions
Tetanus can occur in skeletal muscle
Relationship between electrical activity and contraction
