Question

1). How does the autonomic nervous system (ANS) that controls cardiac muscle contractions differ functionally & anatomically from the somatic motor system that controls skeletal muscle contractions?

2). How do the general effects of the sympathetic division differ from the general effects of the parasympathetic division?

3). Within the ANS, what neurotransmitters are secreted by adrenergic & by cholinergic fibers? Where in the ANS, are the

two neurotransmitters found?

4). Why do sympathetic division effects last much longer than parasympathetic division effects in humans?

Answer 1

1). How does the autonomic nervous system (ANS) that controls cardiac muscle contractions differ functionally & anatomically from the somatic motor system that controls skeletal muscle contractions?

AUTONOMIC NERVOUS SYSTEM	SOMATIC NERVOUS SYTEM
1.Two divisions: Sympathetic and parasympathetic	No more divisions
2.Innervates smooth muscle and cardiac muscle to cause involuntary movements	Innervates the skeletal muscle to make voluntary actions
3.Release Acetylcholine or norepinephrine as neurotransmitter	Acetyl choline as neurotransmitter
4.Axons are lightly myelinated or demyelinated	Axons are heavily myelinated
5.Singular neuron involvement from CNS to effector organ	Two- neuron chain involvement from CNS to effector organ- 1.Preganglionic 2.Postganglionic
6.The impulse is either stimulatory or inhibitory	The impulse is always stimulatory

2). How do the general effects of the sympathetic division differ from the general effects of the parasympathetic division?

SYMPATHETIC DIVISION is for fight and flight actions( to face emergency situations)

• Raising the heart rate
• Constriction of the blood vessels
• Glucose release from the liver
• Regulation of sweating(regulation of body temperature)
• Influence on metabolism
• Influence on kidney activity

1. Dilates pupils
2. Inhibit salivation
3. Relaxes bronchi
4. Accelerates heart beat
5. Inhibit peristalsis and secretion
6. Stimulate glucose production and release
7. Secretion of adrenaline and noradrenaline
8. Inhibits bladder contraction
9. Stimulates orgasm

PARASYMPATHETIC DIVISION is for rest and digestive actions.

• Digestion of food
• Expulsion of waste
• General maintenance related actions

1. Constricts pupils
2. Stimulates salivary flow
3. Constricts bronchi
4. Slows heartbeat
5. Stimulate peristalsis and secretion
6. Stimulates bile release
7. Contracts bladder

3). Within the ANS, what neurotransmitters are secreted by adrenergic & by cholinergic fibers? Where in the ANS, are the two neurotransmitters found?

Within ANS, adrenergic Fibres releases Norepinephrine at Almost all sympathetic postganglionic axons,except those at sweat glands.

Cholinergic Fibres release Acetylcholine at All ANS preganglionic axons & all parasympathetic postganglionic axons.

In both sympathetic system and parasympathetic system, ACh is released at preganglionic neurons. In parasympathetic postganglionic Fibres release Acetylcholine.whereas in sympathetic nervous System, most of the postganglionic Fibres release the norepinephrine. Hence two different neurotransmitters are found in the sympathetic nervous sytem.

4). Why do sympathetic division effects last much longer than parasympathetic division effects in humans?

In sympathetic nervous system(SNS), the preganglionic Fibres arise from the thoracic and lumbar regions of the spinal cord.

• Some of these are synapse with the postganglionic Fibres at the nearby chains of the sympathetic ganglia
• .Some neurons travel up/down the chain before synapsing.
• Some travels the chain without synapsing at all - This group continues as splanchnic nerves to the nearby collateral ganglia for synapsing instead.

The long postganglionic Fibres run all the way to the target organs.The SNS have a high degree of neuronal divergence;One preganglionic fibre can synapse with up to 20 postganglionic fibres.Hence the effect of SNS is widespread.The degree of divergence in PSNS is much lesser than that in the SNS.