The document summarizes cardiac innervation by the autonomic nervous system. It notes that the sympathetic and parasympathetic nervous systems both originate in the medulla oblongata and spinal cord. The sympathetic system uses long preganglionic and postganglionic fibers that travel to cardiac ganglia before innervating the heart. In contrast, the parasympathetic system uses short preganglionic and postganglionic fibers to directly innervate the heart. The sympathetic system releases norepinephrine to increase heart rate and force of contraction, while the parasympathetic system releases acetylcholine to decrease heart rate.

1. CARDIAC INNERVATION
SUBMITTED TO : DR. I.N MITRA
SUBMITTED BY : MEGHA DHADWAL
ROLL NO : 34

2. AUTONOMIC NERVOUS SYSTEM
SYMPATHETIC
PARASYMPATHETIC

3. Origin of ANS
BRAIN AND SPINAL CORD
SPINAL CORD SEGMENTS
TOTAL : 31
8 CERVICAL
12 THORACIC
5 LUMBAR
5 SACRAL
1 COCCYGEAL

4. Origin of ANS
• MEDULLA OBLANGATA , located in the brainstem
above the spinal cord is a major site in brain for
regulating autonomic nerve flow to the heart and
blood vessels .
• The medulla contains cell bodies for two main
divisions of the ANS –
• SYMPATHETIC
• PARASYMPATHETIC

5. SYMPATHETIC CONTRIBUTION
 The sympathetic nerves exit the medulla and travel down
the spinal cord where they synapse with relatively short
preganglionic fibers that travel to and synapse within the
sympathetic ganglia.
 The preganglionic sympathetic fibers innervating the
heart arise from T1-T5 segments of the spinal cord.
 They are myelinated preganglionic fibers.
 Postganglionic fibers from the ganglia travel to the heart
where they synapse at the target sites.

6.  The postganglionic axons are unmyelinated or thinly
myelinated, and those for the heart run in the various
cardiac branches of the sympathetic trunks.
 Thus in the sympathetic component of the autonomic
nervous system the synapses between pre- and post-
ganglionic neurons are often at considerable distances
from the structure innervated.
 By contrast parasympathetic postganglionic fibers are
short.

7. Sympathetic pathway

8. Parasympathetic Contribution
• The parasympathetic nerves i.e (CRANIAL NERVE X )
exit the medulla as long preganglionic efferent fibers
that form synapses with short postganglionic fibers
within the heart or vascular tissue.
• Synaptic relays close to or within the viscera supplied
are characteristic of parasympathetic innervation and
in consequence parasympathetic postganglionic
fibers are relatively short as compared with their
sympathetic counterparts, and more circumscribed in
their distribution.

9. Parasympathetic pathway

10. Anatomical Differences in Sympathetic
and Parasympathetic Divisions
 Length of postganglionic fibers
 Sympathetic – long postganglionic fibers
 Parasympathetic – short postganglionic fibers
 Branching of axons
 Sympathetic axons – highly branched
Influences many organs
 Parasympathetic axons – few branches
Localized effect

11. Neurotransmitters of Autonomic
Nervous System
 Neurotransmitter released by preganglionic axons
Acetylcholine for both branches (cholinergic)
 Neurotransmitter released by postganglionic axons
Sympathetic – most release norepinephrine
(adrenergic)
Parasympathetic – release acetylcholine

12. Peculiarities of nerve supply to the
heart
Nerve supply
Features
Sympathetic innervation More at the base
than the apex
Vagal activity Greater in posterior
and inferior wall

13. Effects of ANS
 Sympathetic nerve – noradrenergic fiber
 Parasympathetic nerve- cholinergic fiber
 Noradrenergic sympathetic nerve
 to the heart increase the cardiac rate (chronotropic
effect)
 the force of cardiac contraction (inotropic effect).
 Cholinergic vagal cardiac fibers decrease the heart rate.

14. SUMMARY

15. Thank
you !