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Questions and Answers
What is the primary function of the sympathetic supply to the lungs?
What is the primary function of the sympathetic supply to the lungs?
From which thoracic segments do the preganglionic fibers originate for the sympathetic supply to the abdomen?
From which thoracic segments do the preganglionic fibers originate for the sympathetic supply to the abdomen?
Which structure is directly stimulated by postganglionic fibers from cervical ganglia?
Which structure is directly stimulated by postganglionic fibers from cervical ganglia?
What is the result of the stimulation of the sympathetic supply to the liver?
What is the result of the stimulation of the sympathetic supply to the liver?
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What role does the adrenal medulla play in the sympathetic supply?
What role does the adrenal medulla play in the sympathetic supply?
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What is the role of internal anal sphincter contraction in the rectum?
What is the role of internal anal sphincter contraction in the rectum?
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What effect does sympathetic supply have on the blood vessels of the skeletal muscles in the upper and lower limbs?
What effect does sympathetic supply have on the blood vessels of the skeletal muscles in the upper and lower limbs?
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Which physiological response occurs during ejaculation due to sympathetic stimulation?
Which physiological response occurs during ejaculation due to sympathetic stimulation?
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What is one of the effects of vasoconstriction in the skin during sympathetic activation?
What is one of the effects of vasoconstriction in the skin during sympathetic activation?
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How does sympathetic activation affect the bladder during urine retention?
How does sympathetic activation affect the bladder during urine retention?
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Study Notes
Sympathetic Supply of Thorax
- Origin: Lateral horn cells (LHCs) of the upper 4 thoracic segments (T1-T4)
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Relay: Preganglionic fibers relay in all cervical ganglia and upper 4 thoracic ganglia. Postganglionic fibers arise from these ganglia to supply the following structures:
- Heart
- Lungs
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Function:
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Heart:
- Increases heart rate
- Increases force of contraction
- Coronary vasodilatation leading to increased blood supply to the cardiac muscle (indirect effect through accumulation of metabolites)
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Lungs:
- Bronchodilatation (widening of air passages) due to relaxation of wall smooth muscle
- Vasoconstriction of pulmonary blood vessels
- Decreases mucous secretion in the air passages
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Heart:
Sympathetic Supply of Abdomen
- Origin: LHCs of 6-12 thoracic segments (T6-T12)
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Relay:
- Celiac ganglion
- Renal ganglion
- Superior mesenteric ganglion
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Function:
- Relaxes the wall of the stomach, small intestine, and proximal part of the large intestine
- Contracts sphincters (leading to food retention)
- Liver: Stimulates glycogenolysis leading to increased blood glucose
- Spleen: Contracts splenic capsule, releasing stored blood to the general circulation (about 200 ml)
- Suprarenal Medulla: Secretory to 80% adrenaline and 20% noradrenaline
- Vasoconstriction (VC) of blood vessels of the stomach, small intestine, proximal part of the large intestine, liver, kidney, and pancreas
Sympathetic Supply of Pelvis
- Origin: LHCs of the 12th thoracic segment and the upper 3 lumbar segments. The preganglionic fibers form right and left lesser splanchnic nerves which are joined to form the pre-sacral nerve.
- Relay: Inferior mesenteric ganglion.
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Function:
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Rectum:
- Relaxation of the wall
- Contraction of the internal anal sphincter leading to retention of stool
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Urinary Bladder:
- Relaxation of the wall
- Contraction of the internal urethral sphincter leading to retention of urine
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Genital Organs:
- Ejaculation of semen due to contraction of the vas deferens, seminal vesicle and prostatic muscles
- VC of blood vessels of pelvic viscera including the external genital tract leading to shrinkage of the penis.
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Rectum:
Sympathetic Supply to Upper and Lower Limbs
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Origin:
- Upper Limb: From LHCs of the (5-9) thoracic segments (T5-T9)
- Lower Limb: From LHCs of the (10-12) thoracic segments (T10-T12)
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Relay:
- Upper Limb: Middle and inferior cervical ganglia and upper 2 thoracic ganglia.
- Lower Limb: Lumbar, sacral
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Function: (In both upper and lower limbs)
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Skeletal Muscle Blood Vessels:
- Vasodilatation - causing better contraction, delayed fatigue, and rapid recovery (Orbelli phenomenon)
- Mechanism:
- Increase in blood flow due to vasodilatation, this helps to supply more oxygen and nutrients and easy removal of waste products
- Increase sensitivity of the motor end plate to acetylcholine
- Activation of phosphorylase enzyme which helps glycogen breakdown and release of energy in the muscle
- Mechanism:
- Vasodilatation - causing better contraction, delayed fatigue, and rapid recovery (Orbelli phenomenon)
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Skin:
- Vasoconstriction
- Contraction of piloerector muscles causing erection of hair
- Secretory to sweat glands
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Skeletal Muscle Blood Vessels:
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Description
This quiz covers the sympathetic nervous system's supply to the thorax and abdomen, detailing the origin, relay, and specific functions for the heart and lungs in the thoracic region, as well as the abdominal structures. Understand the neural pathways and physiological effects involved in these critical body areas.
