Station 5 Flashcards
What is / where is pacemaker of the heart
SA node, Superior/to the right of RA
Describe the conduction pathway
SA node to AV node (slows signal) to Bundle of His which splits into left and right bundle branches.
RBB travels from IV septum, to the apex region of the IV septum, then through the medioseptal trabecula (as the moderator band) which terminates at the root of the right anterior papillary muscle
LBB travels from IV septum, to apex region of IV septum, then into LV, concentrating around the bases of the Anterior papillary muscle
Blood supply to SA node?
60% of time = SA Nodal Artery from RCA
40% of time = Left Circumflex A
Blood Supply to AV Node
AV Nodal branch from RCA
Where are ALL the preganglionic neuron cell bodies of the SNS located?
Lateral horn of the spinal cord T1-L2
What spinal segments supply the heart and lungs?
T1-5
What neurotransmitters does the SNS and PSNS use?
SNS: pre-post ganglionic neurons use Ach. Post-ganglionics onto viscera = NA/A
PSNS: Ach almost always
SNS: what is the anatomical course of the pre-ganglionic and post-ganglionic axons from the cell body in the spinal cord to where they synapse?
Cell bodies in lateral horn on T1-T5. Pre-ganglionic axons exit the lateral horn through the ventral root, then the spinal nerve, then white ramus communicantes, to sympathetic chain ganglia (where they synapse directly, or move up/down the chain before synapsing), then the post-ganglionic axons travel from the sympathetic chain and terminate in cardiac plexus. Use NA/A
PSBS: What is the anatomical course of the PSNS innervation of the heart?
Vagus CN X, travels down neck in carotid sheath, into thoracic cavity (gives of recurrent laryngeal), then travels to cardiac plexus, where it synapses. Post-synaptic axon heads to heart where it principally acts on SA and AV nodes using ACh.
How is pain recieved by the brain from the heart?
Pain aferents run with sympathetic fibers to the sympathetic chain, then through grey rami, to spinal nerves, to dorsal root, to dorsal horn in T1-5.
Explain referred cardiac pain
cardiac pain is often experienced as chest, neck/jaw, l=upper arm (etc) pain. This is because pain afferents from the heart run with sympathetics and end up in dorsal horns of T1-T5. Thus, the CNS interprets the pain as arising to areas that have dermatomes arising from T1-5.
