This document provides an overview of the autonomic nervous system (ANS). It describes that the ANS is divided into the sympathetic and parasympathetic systems which control involuntary functions. The key components of the ANS are receptors, afferent pathways, interneurons, efferent neurons, autonomic ganglia, and effector organs. It then discusses the structures, functions, and targets of the sympathetic system including its thoracic, cervical, and lumbosacral outflows which innervate organs like the heart and blood vessels.

1. NEUROANATOMY
Autonomic Nervous System 1

2. Group Names:
Abdullahi Daher Idhere
Abdulkani Ibrahim Nour
Bushra Abdullahi Issa
Hamse Abdullahi Moh’ed
Khaled Abdulaziz Hussain

3. Introduction
 Nervous system is functionally divided into following
two components –
1. Somatic nervous system
2. Autonomic nervous system.
 Somatic nervous system is the part of nervous
system that controls voluntary functions of body.

4.  Autonomic nervous system is the component of
nervous system which controls or regulates
involuntary functions of body, i.e. those which cannot
be governed as per one’s own desire. Units of these
functions are fundamentally following two:
1. Increase rate and force of contraction of
involuntary muscles (smooth as well as cardiac
muscles).
2. Secretion of exocrine glands.

5. COMPOSITION OF ANS
 Same as somatic nervous system, autonomic nervous
system is made up of following components.
1. Receptors: These are
+ baroreceptors,
+ chemoreceptors,
+ osmoreceptors.
+ Stretch and pain receptors.
2. Afferent pathway: This are peripheral sensory
fibers.
3. Interneurons or connecting neurons: These
interconnect afferent autonomic neuron with
efferent autonomic neuron.

6. 4. Efferent neurons: There are connector neurons
situated in brainstem and spinal cord.
5. Autonomic ganglia: This is the special feature of
efferent pathway of autonomic nervous system, by
which it differs from somatic nervous system.
6. Postganglionic efferent neurons: These are
situated outside central nervous system. Cell bodies
of these neurons form autonomic ganglia.
7. Effector organ: either smooth muscle, cardiac
muscle or a gland.

8. SUBDIVISION OF ANS
 Autonomic nervous system is divided into two parts—
sympathetic and parasympathetic.
 Interrelationship: There are many effector organs where one
system acts, other does not. For example,
arrectores pili muscles => sympathetic
exocrine glands => parasympathetic
 But, there are some organs where both the system produce
physiologically antagonistic effects.
# Force of contraction of heart muscles is increased by
sympathetic, diminished by parasympathetic.
# Tracheobronchial tree are stimulated by parasympathetic,
but sympathetic causes relaxation (bronchodilatation).

9. Sympathetic Vs Parasymathetic
 Sympathetic and parasympathetic parts of
autonomic nervous system differ from each other
as per following criteria –
1. Structural — Anatomical
2. Functional — i) Physiological
ii) Pharmacological.

10. I. Structural differences
 1. Center:
+ Sympathetic system:
T1 to L2 segments.
+ parasympathetic system:
# Brainstem 3rd, 7th, 9th, 10th
cranial nerve
# spinal cord S2, S3 and S4
 2. Supraspinal control:
+ Sympathetic: posterior part of
hypothalamus
+ Parasympathetic: anterior part of
hypothalamus

11. 3. Autonomic ganglia:
# Sympathetic ganglia (Sympathetic trunk)
+ situated close to central nervous system
+ postganglionic fibers are longer
# Parasympathetic ganglia
+ situated close to the target organ
+ postganglionic fibers are shorter

12. II. Physiological difference
 Sympathetic system gets activated during
emergency, stress or anger.
 Parasympathetic system is concerned with
conservation and storage of energy.
Sympathetic
1. Heartbeat increases.
2. Pulse rate becomes rapid with rise
of blood pressure.
3. Pupils get dilated.
4. Vasodilatation of skeletal muscles
due to muscular exercise.
5. Extremities become cold due to
peripheral vasoconstriction.
Parasympathetic
1. Heart rate settles down.
2. Pulse rate gets slower.
3. Rate of respiration becomes
slower with ‘snoring’.
4. Digestion of food gets promoted.
5. Peristaltic movement of intestine
is increased

13. III. Pharmacological difference
 Sympathetic:
+ Preganglionic secretes acetylcholine
+ Postganglionic:
- Norepinephrine (mostly)
- Adrenaline
- Acetylcholine
 Parasympathetic:
+ Preganglionic: Acetylcholine
+ Postganglionic: Acetylcholine

15. SYMPATHETIC PART OF ANS
 Sympathetic system is the greater components of
autonomic nervous system and is more widely
distributed in the body.
 Fundamentally sympathetic nervous system
regulates following unitary functions –
1. Smooth muscles: Which may be in wall of blood
vessels, root of hair follicles (arrectores pili) and wall
of viscera.
2. Cardiac muscles
3. Exocrine glands: Which are only sweat glands.

16. EFFERENT COMPONENT
 Sympathetic part of autonomic nervous system is
made up of following efferent components—
1. Spinal center: This is the collection of nerve cells
in the intermediolateral column if spinal cord
extending from T1–L2 (may be L3) segments.
These cells are called connector neurons.
2. Effector neuron: These neurons are situated
outside central nervous system (spinal cord)
which receive synaptic connection from axons of
connector neuron.

17. 3. Effector organs: Effector organs which receive
axon terminal of effector neuron, are
i. Cardiac muscle fibers
ii. Smooth muscle fibers
iii. Sweat glands.
4. Supraspinal center: Nuclei of posterior half of
hypothalamus which influence spinal center
through hypothalamospinal tract.

20. Types of outflow from Sympathetic
ganglia
1. Lateral branches.
2. Medial branches.
3. Sympathetic trunk.
4. Above T1:
+ Superior cervical ganglion (C1- C4)
+ Middle cervical ganglion (C5 - C6)
+ Inferior cervical ganglion (C7 – C8)
5. Below L2:
+ lower lumbar ( L3 – L5 )
+ sacral ( S1 – S5 )
+ one coccygeal

22. Detailed Efferent Outflow
 Distribution of branches from whole sympathetic
trunk needs to be studied in following three
components.
 Branches from thoracic sympathetic ganglia.
 Branches from cervical sympathetic ganglia.
 Branches from lumbosacral sympathetic ganglia.

23. Branches from Thoracic Sympathetic
Ganglia
 Thoracic part of sympathetic chain is continuous
above with its cervical part and below with its
lumbosacral part.
 The thoracic part of the trunk contains 12 ganglia
numbered as 1st (T1)–12th (T12) thoracic ganglia.
 Sometimes, they may be 11 in number, when 1st
ganglion fuses with inferior cervical ganglion to
form cervicothoracic ganglion. It is called stellate
ganglion.

24. Branches:
 Lateral branches: lateral branches of all the 12 thoracic
ganglia are gray rami which join the respective thoracic
spinal nerve.
 Medial branches: medial splanchnic branches of 12 pair
of thoracic ganglia have the duty to supply branches to
thoracic viscera, and to upper abdominal viscera. That is
why medial branches of thoracic sympathetic ganglia are
classified into following two groups:
1. Medial branches from T1–T5 ganglia to thoracic
viscera.
2. Medial branches from T5–T12 ganglia to upper
abdominal viscera.

25. Medial branches from T1–T5 ganglia:
 Before reaching the target organs these branches of
sympathetic ganglia form plexuses with
parasympathetic fibers of vagus (10th cranial) nerve
close to the viscera.
 The plexuses are following—
a) Cardiac plexus
b) Pulmonary plexus
c) Esophageal plexus
d) Aortic plexus

27. Medial branches from T5–T12 ganglia:
 Nerves formed by medial branches from
T5–T12 ganglia are following:
 These three nerves are commonly termed as
thoracic splanchnic nerve.
1. Greater splanchnic nerve: T5 – T9 ganglia.
2. Lesser splanchnic nerve: T10 and T11 ganglia.
3. Least (Lowest) splanchnic nerve: T12 ganglia

28. Cervical Part of Sympathetic Trunk
 Cervical part of sympathetic trunks are situated on
either side of cervical part of vertebral column, behind
the carotid sheath and in front of prevertebral layer.
 The trunk presents three cervical ganglia —
Superior, middle and inferior.
 preganglionic fibers arise from T1 – T4, and
postganglionic emerges in two forms:
+ Lateral
+ Medial

29. 1. Superior cervical ganglion:
 Lateral : 4 gray communicantis joins C1-C4
 Medial :
1. Internal carotid nerve
2. Branches of external carotid artery
3. Pharyngeal branch
4. Cardiac branch

30. 2. Medial cervical ganglion:
 Lateral: 2 gray rami communicantis joins C5-C6
 Medial:
1. Tracheal and esophageal plexus
2. Thyroid branch
3. Cardiac branch

31. 3. Inferior cervical ganglion:
 Lateral: 2 lateral branches forming inferior
cervical ganglion
 Medial:
1. Ansa subclavia
2. Vertebral nerve
3. Cardiac branch