ANS

• Sweat glands are only supplied by sympathetic nerves.
• The conscious activity that we do has very little to do with our immediate or long term survival.
• Somatic nervous system is involved in voluntary control of skeletal muscle.
• Autonomic nervous system controls cardiac muscle, smooth muscle, and glands.
• Both autonomic nervous system and somatic nervous system carry motor commands, but in somatic nervous system, it is the lower motor neuron.
• Lower motor neuron directly controls the skeletal muscle.
• In ANS, there is a motor neuron in the CNS called preganglionic neuron.
• Many time our organs have both divisions supplying the postganglionic fibres.
• The effects of the sympathetic division, also known as the “fight-or-flight” division, include an increase in alertness, metabolic rate, sweating, heart rate, blood flow to skeletal muscle, and dilates the respiratory bronchioles and the pupils.
• Dual innervation refers to both divisions affecting the same organs, and they mostly have antagonistic effects; they work against eachother.
• When you are sleeping, your parasympathetic is active and your sympathetic is inhibited.
• Bronchial muscle is smooth muscle.
• Sympathetic division components include the sympathetic chain which arises from spinal segments T1–L2, and is preganglionic fibers enter the sympathetic chain ganglia just outside the spinal column.
• The parasympathetic division, also known as the “rest-and-digest” division, constricts pupils, increases digestive secretions, increases digestive tract smooth muscle activity, stimulates urination and defecation, and constricts bronchioles, decreases heart rate.
• A person who is sleeping has a reduced heart rate and respiratory rate as compared to when they are in fight or flight response.
• Some organs are innervated by only one division.
• The adrenal medullae, which are preganglionic fibers, enter the center of the adrenal glands, and are innervated by preganglionic fibers.
• Modified sympathetic ganglia, or neurons, in the adrenal medullae, secrete norepinephrine (NE) and epinephrine (E) into capillaries, functioning like an endocrine gland.
• Preganglionic neurons communicate with/send signals to ganglionic neurons (autonomic ganglia) whose axons are called postganglionic fibres.
• Autonomic ganglia is located outside of CNS, so it is not in the spinal cord.
• Preganglionic neurons will synapse with postganglionic neuron, so there is another neuron coming out.
• Postganglionic neuron will innervate the cardiac muscle, smooth muscle and the glands.
• Sympathetic division (fight or flight system) of the ANS is involved in the response to stress and emergency situations.
• Preganglionic fibers leave spinal cord in thoracic and lumbar spinal segments.
• Ganglia located near spinal cord (not inside).
• Short preganglionic fibers.
• Long postganglionic fibers.
• Parasympathetic division (rest and digest system) of the ANS conserves the energy and promotes the sedentary activities such as digestion.
• Preganglionic fibers originate in brain stem and sacral spinal region.
• Ganglia located near or within target organs.
• Long preganglionic fibers.
• Short postganglionic fibers.
• Both sympathetic and parasympathetic divisions affect the target organs through release of a substance called as neurotransmitter.
• All preganglionic fibers in ANS are cholinergic and they release acetylcholine (ACh) - neurotransmitter.
• Postganglionic parasympathetic fibers are cholinergic.
• Effects of postganglionic sympathetic fibers are usually excitatory.
• Whether the result is stimulation or inhibition, it depends on the membrane receptor where this neurotransmitter is going to get attached.