There are stories of a chicken with its head cut off surviving. However, that is a MUCH more primitive animal, with ganglia which control breating, etc, further down. However, the nerves which control breathing, an automatic function are IN THE HEAD. Therefore, no human which his head cut off could breathe. Period. Again, look at the example in Maccabees. It is simply a metaphor for the desire to live.
SILLINESS!! AMEN!!
The passage did not talk about “breathing”. It said “struggled for breath”.
Here is a website about the autonomic nervous system, which is far more complex than “IN THE HEAD”:
microvet.arizona.edu/Courses/VSC401/autonomicNervous.html
Here are some details:
Basic Anatomy of ANS
Preganglionic neuron
- cell body in brain or spinal cord
- axon is myelinated type B fiber that extends to autonomic ganglion
Postganglionic neuron
- cell body lies outside the CNS in an autonomic ganglion
-axon is unmyelinated type C fiber that terminates in a visceral effector
Divisions of the ANS
2 major divisions
– parasympathetic
– sympathetic
Dual innervation
– one speeds up organ
– one slows down organ
– Sympathetic NS increases heart rate
– Parasympathetic NS decreases heart rate
•
Sources of Dual Innervation
• Sympathetic (thoracolumbar) division
– preganglionic cell bodies in thoracic and first 2 lumbar segments of spinal cord
• Parasympathetic (craniosacral) division
– preganglionic cell bodies in nuclei of 4 cranial nerves and the sacral spinal cord
Locations of Autonomic Ganglia
• Sympathetic Ganglia
– trunk (chain) ganglia near vertebral bodies
– prevertebral ganglia near large blood vessel in gut
• celiac
• superior mesenteric
• inferior mesenteric
• Parasympathetic Ganglia
– terminal ganglia in wall of organ
Autonomic Plexuses
• Cardiac plexus
• Pulmonary plexus
• Celiac (solar) plexus
• Superior mesenteric
• Inferior mesenteric
• Hypogastric
Organs Innervated by Sympathetic NS
• Structures innervated by each spinal nerve
– sweat glands, arrector pili mm., blood vessels to skin & skeletal mm.
• Thoracic & cranial plexuses supply:
– heart, lungs,esophagus & thoracic blood vessels
– plexus around carotid artery to head structures
• Splanchnic nerves to prevertebral ganglia supply:
– GI tract from stomach to rectum, urinary & reproductive organs
Circuitry of Sympathetic NS
• Divergence = each preganglionic cell synapses on many postganglionic cells
• Mass activation due to divergence
– multiple target organs
– fight or flight response explained
• Adrenal gland
– modified cluster of postganglionic cell bodies that release epinephrine & norepinephrine into blood
Anatomy of Parasympathetic NS
• Preganglionic cell bodies found in
– 4 cranial nerve nuclei in brainstem
– S2 to S4 spinal cord
• Postganglionic cell bodies very near or in the wall of the target organ in a terminal ganglia
Parasympathetic Sacral Nerve Fibers
• Form pelvic splanchnic nerves
• Preganglionic fibers end on terminal ganglia in walls of target organs
• Innervate smooth muscle and glands in colon, ureters, bladder & reproductive organs
ANS Neurotransmitters
Classified as either cholinergic or adrenergic neurons based upon the neurotransmitter released Adrenergic
Cholinergic
Cholinergic Neurons and Receptors
• Cholinergic neurons release acetylcholine from preganglionic neurons & from parasympathetic postganglionic neurons
• Excites or inhibits depending upon receptor type and organ involved
• Nicotinic receptors are found on dendrites & cell bodies of autonomic NS cells and at NMJ
• Muscarinic receptors are found on plasma membranes of all parasympathetic effectors
Adrenergic Neurons and Receptors
• Adrenergic neurons release norepinephrine (NE) )
– from postganglionic sympathetic neurons only
– Excites or inhibits organs depending on receptors
– Alpha1 and Beta1 receptors produce excitation
– Alpha2 and Beta2 receptors cause inhibition
– Beta3 receptors(brown fat) increase thermogenesis
• NE lingers at the synapse until enzymatically inactivated by monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT)
Physiological Effects of the ANS
• Most body organs receive dual innervation
– innervation by both sympathetic & parasympathetic
• Hypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels
• Some organs have only sympathetic innervation
– sweat glands, adrenal medulla, arrector pili mm & many blood vessels
– controlled by regulation of the “tone” of the sympathetic system
Sympathetic Responses
Dominance by the sympathetic system is caused by physical or emotional stress – “E situations”
– emergency, embarrassment, excitement, exercise
• Alarm reaction = flight or fight response
– dilation of pupils
– increase of heart rate, force of contraction & BP
– decrease in blood flow to nonessential organs
– increase in blood flow to skeletal & cardiac muscle
– airways dilate & respiratory rate increases
– blood glucose level increase
• Long lasting due to lingering of NE in synaptic gap and release of norepinephrine by the adrenal gland
Parasympathetic Responses
• Paradoxical fear when there is no escape route or no way to win
– causes massive activation of parasympathetic division
– loss of control over urination and defecation
Autonomic or Visceral Reflexes
• Autonomic reflexes occur over autonomic reflex arcs. Components of that reflex arc:
– sensory receptor
– sensory neuron
– integrating center
– pre & postganglionic motor neurons
– visceral effectors
We have a comedian on our board!!