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AUTONOMIC NERVOUS SYSTEM (COMPARING BETWEEN THE ANS AND SNS…
AUTONOMIC NERVOUS SYSTEM
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COMPARING AND CONTRASTING BETWEEN THE TWO MAIN DIVISIONS OF THE ANS --- THE SYMPATHETIC AND THE PARASYMPATHETIC DIVISIONS
ORIGIN OF THE DIVISION IN THE CNS :The two divisions originate from different regions of the Central Nervous System
The SYMPATHETIC DIVISIONS’ fibers, emerge from the thoracic and superior lumbar parts of the spinal cord.
The PARASYMPATHETIC DIVISIONS’ fibers, emerge from the brain and the sacral spinal cord.
THE LOCATION OF THEIR PREGANGLIONIC AND POSTGANGLIONIC CELL BODIES AND WHAT NEUROTRANSMITTER THEY RELEASE
Postganglionic cell bodies in the Sympathetic Nervous System Location: Their cell bodies are located in the ganglia, and they send their axons to target organs or glands. Releases norepinephrine
Preganglionic cell bodies of the Parasympathetic Nervous System Location: Their cell bodies are either located in the nuclei of the four cranial nerves in the brain stem (Oculomotor, Facial, Glossopharyngeal and the Vagus Nerves), or in the second through the fourth sacral segments of the spinal cord. Releases ACh
Postganglionic cell bodies of the Parasympathetic Nervous System Location: Their cell bodies are usually located close to or in the wall of the structure being innervated. Releases ACh
Preganglionic cell bodies in the Sympathetic Nervous System Location: Their cell bodies are located in segments T1 to L2 In the spinal cord. Releases ACh
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THE LENTH OF THE PREGANGLIONIC VERSUS POSTGANGLIONIC AXONS: In the ANS, the motor unit includes a chain of two motor neurons
The Sympathetic Pathways The preganglionic neurons are much shorter than the postganglionic neurons. This is because the sympathetic ganglia are close to the spinal cord.
The Parasympathetic Pathways The preganglionic neurons are longer, and from there , the postganglionic neurons are super short. This is because the parasympathetic ganglia are close to their effectors.
COMPARING AND CONTRASTING BETWEEN THE INNERVATION AFFECTS OF THE SYMPATHETIC VERSUS THE PARASYMPATHETIC DIVISIONS
SYMPATHETIC EFFECT ON THE FOLLOWING ORGANS: HEART - INCREASES RATE AND FORCE OF HEARTBEAT, EFFECTS THE SA NODE. AIRWAYS OF THE LUNGS: DILATES BRONCHIOLES (BRONCHODILATION) AND MILDLY CONSTRICTS BLOOD VESSELS. GI TRACT: DECREASES ACTIVITY OF GLANDS AND MUSCLES OF DIGESTIVE SYSTEM AND CONSTRICTS SPHINCTERS; CAUSES VASOCONSTRICTION - IRIS OF THE EYE : STIMULATES DILATOR MUSCLES, DILATES EYE PUPILS. -LENS OF THE EYE WEAKLY INHIBITS CILIARY MUSCLES, WHICH FLATTEN THE LENS FOR DISTANCE VISION. - BLOOD VESSELS CONSTRICTS MOST VESSELS AND INCREASES BLOOD PRESSURE; CONSTRICTS VESSELS OF ABDOMINAL VISCERA AND SKIN; TO DIVERT BLOOD TO MUSCLES, BRAIN AND HEART WHEN NECESSARY; DILATES VESSELS OF THE SKELETAL MUSCLES DURING EXERCISE. - SWEAT GLANDS STIMULATES COPIOUS SWEATING. - ARRECTOR PILI (THESE ARE ATTACHED TO HAIR FOLLICLES) STIMULATES TO CONTRACT (ERECTS HAIRS AND PRODUCES GOOSE BUMPS). -- ADRENAL MEDULLA : STIMULATES MEDULLA CELLS TO SECRETE EPINEHRINE AND NOREPINEPHRINE INTO THE BLOODSTREAM. ACCESSORY DIGESTIVE ORGANS, WHICH INCLUDE: SALIVARY GLANDS AND THE LIVER DECREASES ACTIVITY OF THE SALIVARY GLANDS AND RELEASES GLUCOSE IN THE LIVER
PARASYMPATHETIC EFFECT ON THE FOLLOWING ORGANS: HEART - DECREASES THE RATE OF THE HEART AND SLOWS AND STEADIES THE HEART. AIRWAYS OF THE LUNGS: CONSTRICTS BRONCHIOLES - GI TRACT: INCREASES MOTILITY AND AMOUNT OF SECRETION BY DIGESTIVE ORGANS; RELAXES SPHINCTERS TO ALLOW MOVEMENT OF FOODSTUFFS ALONG TRACT. - IRIS OF THE EYE STIMULATES CONSTRICTOR MUSCLES; CONSTRICTS EYE PUPILS. - LENS OF THE EYE STIMULATES CILIARY MUSCLES, WHICH RESULTS IN BULGING OF THE LENS FOR ACCOMODATION AND CLOSE VISION. - BLOOD VESSELS LITTLE TO NO EFFECT - SWEAT GLANDS NO INNERVATION. - ARRECTOR PILI (THESE ARE ATTACHED TO HAIR FOLLICLES) NO INNERVATION. - ADRENAL MEDULLA NO INNERVATION. ACCESORY DIGESTIVE ORGANS, WHICH INCLUDE: SALIVARY GLANDS AND THE LIVER INCREASES ACTIVITY IN THE SALIVARY GLAND AND HAS NO EFFECT ON THE LIVER.