Autonomic Nervous System Dr Dileep Verma Associate Professor Deptt of Physiology KGMU

Lecture-1 :Topics Autonomic Nervous System (ANS): Introduction Divisions General Organization Neurons of ANS

Learning Objectives Difference between Somatic & ANS Autonomic nervous system: - Anatomical Organization - Functional importance

Autonomic Nervous System Autonomic nervous system (ANS) Innervates organs whose functions are not usually under voluntary control Effectors of ANS are-  Cardiac muscle  Smooth muscles and  Glands. Effectors are part of visceral organs and blood vessels.

Organization of Nervous system

A Comparison of Somatic and Autonomic Function

 One neurons in the efferent pathway.  Its cell body in gray matter of spinal cord.  Innervates the Muscle fibers  Always Excitatory  Two neurons in the efferent pathway.  1 st neuron has its cell body in gray matter of brain or spinal cord. Preganglionic neuron.  Synapses with 2 nd neuron within an autonomic ganglion. Postganglionic neuron.  Excitatory/Inhibitory

A Comparison of Somatic and Autonomic Function

Higher levels of autonomic control Activity of the ANS is controlled by following centers - Higher centers  Cerebral cortex  Limbic system Hypothalamus Medullary centers Spinal centers

Autonomic Nervous System Preganglionic autonomic fibers originate in  Midbrain  Hindbrain  Spinal cord. Autonomic ganglia are located in  Head  Neck  Abdomen. Postganglionic autonomic fibers arises from ganglia & innervate the target tissue

Autonomic Nervous System Preganglionic fibers are -  Myelinated  Type B fibers Postganglionic fibers are-  Myelinated  Type B fibers Autonomic nerves release NT that may be stimulatory or inhibitory

Visceral Effector Organs Involuntary effectors are somewhat independent of their innervations  Smooth muscles maintain resting tone in absence of nerve stimulation  Denervation hypersensitivity-  Damage to autonomic nerve makes its target tissue more sensitive than normal to stimulating agents.  Cardiac and many smooth muscles can contract rhythmically in absence of nerve stimulation

Divisions of the ANS ANS has two divisions- 1.Sympathetic nervous system 2.Para-sympathetic nervous system  Both have preganglionic neurons that originate in CNS.  Both have postganglionic neurons that originate outside of the CNS in ganglia.

Autonomic Nervous System

Neurons of ANS The Neuron cell is the “functional unit” of the nervous system (Neurone is the official UK spelling) Neurons are highly specialised cells which can carry electrical impulses along their membranes Neurons can also communicate with other neurons across synapses by chemicals called neurotransmitters

Motor Neuron:

1.Autonomic ganglia are: A.Cholinergic B.Adrenergic C.Noradrenergic D.Dopaminergic

2.Head ganglion of autonomic nervous system is: A.Thalamus B.Hypothalamus C.Superior cervical ganglion D.Stellate ganglion

3.What percentage of fibers in an average skeletal nerves nerve are sympathetic ? A.08 B.20 C.40 D.60

4.True regarding autonomic system is - A.High centre of integration is medulla. B.Conduction in autonomic fibres is same as in somatic motor fibres. C.Preganglionic parasympathetic fibres are more lengthy. D.Ratio of preganglionic and postganglionic fibres is 20:1

5.ANS is also called: A.Vegetative nervous system B.Efferent visceral nervous system C.Involuntary nervous system D.All of the above