Autonomic nervous system: anatomy
What is the famous catch phrase for the sympathetic nervous system?
'Fight or flight' Adapts the body for physical activity • increases alertness, heart rate, blood pressure, pulmonary airflow, blood glucose concentration, and blood flow to cardiac and skeletal muscle • Decreases blood flow to the skin and digestive tract.
What is the famous catch phrase for the parasympathetic nervous system?
'Rest & digest'; 'feed & breed' Has a calming effect on many body functions. It is associated with reduced energy expenditure and normal bodily maintenance, including such functions as digestion and waste elimination.
Describe the 3 nerve fibre pathways of the sympathetic nervous system
1. Preganglionic fibres enter ganglia and synapse on postganglionic cell without travelling up or down the sympathetic chain; postganglionic fibre exits spinal nerve at same level 2. Preganglionic fibres travel to higher or lower ganglia and then synapse at a different spinal level with postganglionic fibre exiting chain through spinal nerve 3. Preganglionic fibres pass through sympathetic chain without synapsing to reach collateral ganglia (celiac or mesenteric) via splanchnic nerves where synapse occurs on postganglionic fibre near target organ
What is the structure of the parasympathetic nervous system?
Has a long preganglionic and short postganglionic nerve fibre.
What is the structure of the sympathetic nervous system?
Has a short preganglionic and long postganglionic nerve fibre.
In regards to the parasympathetic nervous system, what is the action of the facial nerve?
Innervates tear, nasal and salivary glands
In regards to the parasympathetic nervous system, what is the action of the glossopharyngeal nerve?
Innervates the parotid salivary gland
In regards to the parasympathetic nervous system, what is the action of the vagas nerve?
Innervates the viscera as far as proximal half of colon
In regards to the parasympathetic nervous system, what is the action of the oculomotor nerve?
Narrows pupil & focuses lens
Which cranial nerves carry parasympathetic nerve fibres?
Oculomotor nerve (CNIII) Facial nerve (CNVII) Glossopharyngeal nerve (CNIX) Vagus nerve (CNX)
Give an example of a visceral reflex.
Response to high blood pressure 1. High blood pressure detected by arterial stretch receptors 2. afferent neuron carries signal to cardiac centre in medulla oblongata 3. efferent signals travel to the heart via vagus nerve 4. heart slows reducing blood pressure
What is the alternate name of the parasympathetic nervous system?
The craniosacral division
Why is the adrenal medulla associated with the autonomic nervous system?
The inner adrenal medulla is essentially a modified sympathetic ganglion which secretes epinephrine and norepinephrine directly into the bloodstream. This process is known as "mass activation"
What is the enteric nervous system?
The nervous system of the digestive tract
Describe the nerve fibre pathways of the parasympathetic nervous system
The preganglionic fibres originate in the brain (pons & medulla) & sacral region of the spinal cord and synapse in ganglia located next to or within organs innervated. (terminal ganglia) • Do not travel within spinal nerves (cranial nerves & pelvic splanchnic nerves) • Sacral parasympathetic fibres innervate lower half of large intestine, rectum, urinary & reproductive system • No parasympathetic innervation of blood vessels, sweat glands, and arrector pili muscles, these structures only receive innervation by sympathetic nervous system (not dual innervation)
What is the alternate name of the sympathetic nervous system?
The thoracolumbar division
What is the significance of the enteric nervous system?
• Composed of 100 million neurons found in the walls of the digestive tract (no components in CNS) • Has its own reflex arcs and can operate without input from parasympathetic or sympathetic NS • Regulates motility of viscera and secretion of digestive enzymes and acid in concert with the ANS
