Cardiac Innervation Flashcards
Summary of Cardiac innervation (sympathetic)
CNS -> (bilateral) Presynaptic cardiac sympathetic efferent ->synapse in cervical/upper thoracic sympathetic chain ganglion -> (bilateral) postsynaptic cardiac sympathetic efferent -> to SA node & myocardium (APs increase heart rate and contractility)
Summary of Cardiac innervation (parasympathetic)
Presynaptic cardiac parasympathetic efferent fibres travel in vagus nerve -> ganglion on surface of the heart where a synapse takes place -> postsynaptic parasympathetic fibres will travel to the surface of the heart -> SA node (APs decrease heat rate)
This is Vagal tone - continuous background APs in CN X to slow heart rate
How does sympathetic signals from the CNS reach organs?
Presynaptic sympathetic fibres from he brain travel inferiorly within spinal chord tracts
Then exit the spinal chord in one of T1-L2/3 spinal nerves (thoracolumbar outflow) and then do 1 if the following 5 options… (bold relevant to cardio/this)
1.) go into ganglion of same level and synapse
2/3.) travel superiorly/inferiorly in the sympathetic chain to another ganglion and synapse. Postsynaptic fibre travelling to organ as splanchnic nerves.
4.) pass straight through the sympathetic chain ganglion without synapsing, as a domino pelvic splanchnic nerves, to synapse in one of the prevertebral ganglia of the abdomen (e.g. celiac ganglion)
5.) pass straight to adrenal medulla without synapsing as abdominopelvic splanchnic nerve (directly stimulating adrenaline release)
What splanchnic nerves travel to heart and lungs?
Cardiopulmonary splanchnic nerves (carry postsynaptic sympathetic nerves to heart and lungs - thoracic visera)
Why does the heart have bilateral sympathetic innervation?
As it is essentially a midline organ, although the innervation is predominantly left sided for the heart
What is the cardiac plexus?
An intertwining/network of nerves that contains various different nerve fibre types:
Sympathetic
Parasympathetic (via vagus nerve)
Visceral afferent
How are signals sent from heart back to CNS
Aortic arch Baroreceptor reflex afferents travel back up the vagus nerve back to CNS about blood pressure
Visceral afferent - pain fibres from heart- travel back with cardiopulmonary sphlanchnic nerves and follow sympathetic fibres back to CNS
How do pain signals from the heart reach the brain? And therefore reach conciousness
Visceral afferents APs (via cardiopulmonary splanchnic nerves) through spinal nerves back toward spinal chord , up spinal chord,pass bilaterally to thalamus and hypothalamus and then diffuse areas of the cortex in order to reach consciousness
What is the dual function of cardiopulmonary splancnic nerves do?
Carry post synaptic sympathetic fibres towards heart
Also
Carry pain fibres (visceral afferents) away from heart to CNS
