B ches
L Grey rami communicans to all the spinal nerves, i.e.
T1-T12. The postganglionic fibres pass along the
spinal nerves to supply cutaneous blood vessels,
sweat glands and arrector pili muscles.(^2) Some white rami communicans from T1-T5 ganglia
travel up to the cervical part of sympathetic trunk to
relay in the three cervical ganglia. Fibres from the
lower thoracic ganglia T70-L2 pass down as
preganglionic fibres to relay in the lumbar or sacral
ganglia.
3 The first five thoracic ganglia give postganglionic
fibres to heart, lungs, aorta and oesophagus.
4 Lower eight ganglia give fibres which are pregang-
lionic (unrelayed) for the supply of abdomlnit
viscera. These are called splanchnic (visceral)nerves.
Ganglia 5-9 give fibres which constitute greater
splanchnic nerve. Some fibres reach adrenal medulla.
Ganglia 9-10 give fibres that constitute lesser
splanchnic nerve.
Ganglion 11 gives fibres that constitute lowest
splanchnic nerve.
Nerve Supply of Heort
Preganglionic sympathetic neurons are located inlateral
horns T1-T5 segments of spinal cord. These fibres pass
along the respective ventral roots of thoracic nervei, to
synapse with the respective ganglia of the sympathetic
trunk. After relay, the postganglionic fibres form thoracic
branches which intermingle with the vagal fibres, to form
cardiac plexus.
Some fibres from T1-T5 segments of spinal cord
reach their respective ganglia. These fibres then travel
up to the cervical part of the sympathetic chain and
relay in superior, middle and in-ferior cervical ganglia.
After relay, the postganglionic fibres form the three
cervical cardiac nerves. Preganglionic parasympathetic
neurons for the supply of heart are situated in the dorsal
nucleus of vagus nerve.
Sympathetic activity increases the heart rate. Larger
branches of coronary are mainly supplied by
Table A2.1:
Right half
- Superior, middle, inferior cervical cardiac branches of right
sympathetic trunk - Cardiac branches olf2-T4 ganglia of right side
- Superior and inferior cervical cardiac branches of right vagus
- Thoracic cardiac branch of right vagus
- Two branches of right recurrent laryngeal nerve arising from
neck region
APPENDIX 2sympathetic. It causes vasodilatation of coronary
arteries. Impulses of pain travel along sympathetic
fibres. These fibres pass mostly through left
sympathetic trunk and reach the spinal cord via T1-T5
spinal nerves. Thus the pain may be referred to the area
of skin supplied by T1-T5 nerves, i.e. retrosternal,
medial side of the upper limbs. Since one is more
conscious of impulses coming from skin than the
viscera, one feels as if the pain is in the skin. This is the
basis of the referred pain.
Smaller branches of coronary artery are supplied by
parasympathetic nerves. These nerves are concerned
with slowing of the cardiac cycle.
The nerves reach the heart by the following two
plexuses.Superficial cardiac plexus is formed by the following:
1 Superior cervical cardiac branch of left sympathetic
trunk.
2 Inferior cervical cardiac branch of left vagus nerve.Deep cardiac plexus consists of two halves which are
interconnected and lie anterior to bifurcation of trachea
(Table A2.7).
Branches from the cardiac plexus give extensive
branches to pulmonary plexuses, right and left coronary
plexuses. Branches from the coronary plexuses supply
both the atria and the ventricles. Left ventricle gets
richer nerve supply because of its larger size.Nerue Supply of Lungs
The lungs are supplied from the anterior and posterior
pulmonary plexuses. Anterior plexus is an extension
of deep cardiac plexus. The posterior is formed from
branches of vagus and T2-T5 sympathetic ganglia.
Small ganglia are found on these nerves for the relay
of parasympathetic brought via vagus nerve fibres.
Parasympathetic is bronchoconstrictor or motor,
whereas sympathetic is inhibitory. Sympathetic
stimulation causes relaxation of smooth muscles ofLeft halfOnly middle and inferior branchesSame
Only the superior cervical cardiac branch of left vagus
Same
Same, but coming from thoracic region