The autonomic nervous system is a part of the peripheral nervous system that controls cardiac muscles, smooth muscles and glands.
It functions largely below the level of consciousness and serves to control visceral activities. The primary target of autonomic nervous system include the following
1.) Circulatory system (heart and blood vessels)
2.) Digestive system (gastrointestinal gland, sphincter, liver and salivary gland)
3.) Reproductive system (uterus and genitals)
4.) Renal system (kidney and sphincters)
5.)visual system (pupil dilator and cilliary muscles)
Comparison of smooth and autonomic nervous system (Differences)
FEATURE
SOMATIC NERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM
effectors:
Skeletal muscle.
Smooth,cardiac muscles and glands.
Control:
Voluntary.
Involuntary.
Efferent pathway:
One nerve fibers from central nervous system to effector organ.
Two nerve fibers from central nervous system to effector organ.
Neurotransmitter:
Acetylcholine is its neurotransmitter.
Acetylcholine and non adrenaline is its neurotransmitter.
Effect on target organ:
Has an excitatory effect.
Its effect Could be excitatory or inhibitory.
Effect on denervation:
Placid paralysis
Denervation hypersensitivity
Similarities:
1.) Both the somatic and autonomic nerve are motor and efferent
2.) Both are characterized by afferent and efferent fibers
Divisions Of The Autonomic Nervous System
1.) Sympathetic division:- the sympathetic division functions essentially to adapt the body for physical activity and it does the following
a.) Increases alertness by stimulating the reticular activating system.
b.) Increases blood flow to the cardiac and skeletal muscle.
c.) Reduces blood to the skin and digestive tract.
All this reaction occur during exercise, stretch, danger, competition, trauma, anger, etc.
Physiology And Anatomy Of The Sympathetic Division
1.) They originate from the thoracic region and lumbar region of the spinal cord. That is they are thoracolumber in origin from t1 to l2.
2.) Their ganglia are described as been para vertebral and collateral. Para vertbral means they are located near the vertebral column. While they are called collateral because they are situated in the thorax, abdomen and pelvis in relation to aorta and its branches.
3.) They have short preganglion fibers and long post ganglionic fiber.
4.) The sympathetic division acts during period of stress or excitement.
5.) Sympathetic effect are catabolic, that is they increase the breakdown process from the body.
6.) They are ergotropic, that is they stimulate the general defense of the body.
7.) They are dynamogenic, that is they are energy producing.
Parasympathetic Division
The parasympathetic division carry out mostly vegetative and restorative function.
Physiologic Anatomy Of Parasympathetic Division
1.) They originate from cranial nerves as well sacral nerves on the sacral area of the spinal cord, that is they are craniosacral in origin.
2.) They have collateral and terminal ganglia:- terminal ganglia are located very close to the effector organ or in the effector organ itself. They have long preganglionic fiber and short post ganglionic fiber.
3.) Functionally, the parasympathetic division acts during quiet condition when the individual is at rest. It makes a homeostatic adjustment necessary for vital function. Note that heart beat, functions of the digestive system and liver, are kept going by the increased activity of parasympathetic division of the autonomic nervous system.
5.) Parasympathetic effect are anabolic
6.) They stimulate the nutritional activities of the body.
7.) They are hypnogenic meaning they produce sleeping or resting conditions.
FEATURE
SYMPATHETIC
PARASYMPATHETIC
origin:
Thoracolumber in origin
Craniosacral in origin
Location of ganglia:
Paravertebral and collateral
Collateral and terminal
Fiber length:
Short preganlionic and long postganglionic fibers
Long preganglionic and short postganglionic fibers
Neural divergence:
It is extensive
It is minimal
Effect on system:
Often wide spread and general
Most specific and local
SIMILARITIES :-
1.) Both enervate mostly same structure
2.) Both cause opposite effect
3.) Both involve multiple receptor system
4.) Both are associated with ganglia
5.) Both are cholinergic at preganglionic synapse
6.) Both are active simultaneously
7.) Both exhibit a background rate of activities called autonomic tone.
ORGANIZATION OF SYMPATHETIC DIVISION
The sympathetic nerves originate from the thoracic and lumber region of the spinal cord, that is from T1 to T2. T1 supplies the head and T2 supplies the neck. T3 - T6 supplies the thorax and upperlimb T7 - T11 supplies the abdomen, T12 - L2 supplies the lower limb. This distribution is only approximate and overlaps greatly. The distribution of sympathetic nerves to each organ is determined partly by the position in the embryo where the organ originates.
