W1 - conduction system

neuromuscular system

• somatic motor and autonomic control at the level of the brain

  • AP are generated

  • travel down neuron to neuromuscular junction

  • AP initiate chain of events that lead to msucle contraction

• activity can be modified by the autonomic nervous system (extrinsic innervation)

• contraction of cardiac cells is predominantly self regulated

  • doesn’t need commands form the brain

contractions

• heart beat is dependent on electrical activity that the heart generates via the intrinsic conduction system

• myocardium includes cardiac pacemaker cells (autorhythmic cells)

  • unstable resting membrane potential (changing)

  • continually depolarise to generate APs → action potentials in one muscle cell can be connected to the neck muscle cell → allows coordinated activity

Sinoatrial (SA) node (1)

• the pacemaker, generate impulses

• right atrial wall

• depolarises 80-100x per minute

• ANS modifies this to 75x per minute

• electrical activity from SA node penetrates to LA

Atrioventricular (AV) node (2)

• the impulses pause at the atrioventricular (AV) node

  • delays impulse for 0.1 sec while atria complete contraction

  • generates impulses 40-60x per min

delay of 0.1 se allows for atrium to fully contract, propelling blood into ventricles

Atrioventricular bundle (bundle of his) (3)

• connects the atria to the ventricles

bundle branches (4)

conducts impulses through the interventricular septum

purkinje fibers (5)

depolarize the contractile cells of both ventricles

extrinsic innervation

• autonomic nervous system modifies heart activity

• cardiac centres in the medulla oblongata

carioaccelerayory centre increases heart eate and force of contraction

• sympathetic input via the thoracic spinal cord to the SA node, AV node, myocardium, coronary arteries

cardioinhibitory centre decreases heart rate

• parasympathetic input via the vagus nerve to the SA and AV nodes