Chapter 14, the ANS
What are te two major classes of adrenergic?
1- Alpha 2- Beta
What distinguishes the sympathetic from the parasympathetic divisions?
1- Their unique origin sites 2- The relative length of their fibers 3- the location of their ganglia
Tell me about Acetylcholine in the ANS
1- all ANS preganglionic axons release Acetylcholine 2- All parasympathetic postganglionic axons release acetylcholine at synapses with their effectors.
What are some of the metabolic effects created by the sympathetic that the parasympathetic cannot reverse
1- increases the metabolic rate of body cells 2- raises blood glucose levels 3- mobilizes fats for use as fuels 4- increases mental alertness by stimulating the reticular activating system of the brain stem.
What are the key differences between the autonomic and the somatic nervous system?
1- their effector 2- in their efferent pathways and ganglia 3- target organ responses to their neurotransmitter
Tell me about the parasympathetic and the cranial nerve 7
Facial cranial nerve
What happens when faster blood delivery is needed?
Fibers from the sympathetic division deliver impulses more rapidly, causing blood vessels to constrict and blood pressure to rise.
What are cholinergic fibers?
Fibers that release Acetylcholine
What are adrenergic fibers?
Fibers that release norepinephrine.
What are the acetylcholine releasing fibers called?
Cholinergic fibers
Where are all sympathetic ganglia?
Close to the spinal cord, since the preganglionic nerve are short.
What is the cranial outflow of the parasympathetic division
Preganglionic fibers runs through the following cranial nerve; -oculomotor (3) -facial (7) -glossopharyngeal (9) -vagus (10)
What is the craniosacral division?
It refers to the parasympathetic, since preganglionic fibers spring from opposite ends of the CNS, the brain and the sacral region of the spinal cord.
What is the most important role of the Parasympathetic system?
Its the D division -digestion -defecation -diuresis (urination)
What is the most important role of the sympathetic system?
Its the E division -exercise -excitement -emergency -embarrassment
What is the thoracolumbar division?
Its the sympathetic division, since all the preganglionic fibers arises from cell bodies of preganglionic neurons in the spinal cord segments T1-L2
What is autonomic ganglia?
Its where the preganglionic neurons axon synapse with the postganglionic neuron. They are motor ganglia, containing the cell bodies of motor neurons.
Most glands are activated by witch type of ANS division. What is the exception?
Most glands are activated by parasympathetic division. The exception is the adrenal glands and sweat glands which are activated by the sympathetic division.
Are there any lateral horns in the sacral segments?
No, since parasympathetic preganglionic neurons in the sacral cord are far less abundant than the comparable sympathetic neurons in the thoracolumbar region
Tell me about the parasympathetic and the cranial nerve 3
Oculomotor nerve The parasympathetic fibers in the oculomotor nerve, innervate smooth muscles in the eyes that causes the pupil to constrict and the lenses to bulge.
Who serves the sweat glands and the arrector pili?
Only the sympathetic fibers
What is a good example of cooperative effect between the parasympathetic and the sympathetic division?
The control of the external genitalia. -Parasympathetic stimulation causes vasodilation of blood vessels in the external genitalia, causing erection -Sympathetic stimulation causes ejaculation of semen by the penis
What is the effect of muscarinic receptors once bound to acetylcholine?
The effect differs. ex. Muscarinic receptors in the cardiac muscle slow down heart rate. muscarinic receptors in the smooth muscle of the GI tract increase motility
What is the effect of Acetylcholine when binds to nicotinic receptors?
The effect of Acetylcholine binding to nicotinic receptors is always stimulatory.
What does the response to the neurotransmitter being release by the ANS in the target organs
The effect of norepinephrine and acetylcholine are not consistently either excitation or inhibition. The response of visceral effectors to these neurotransmitter depends not only on the neurotransmitter but also the receptors to which they attach.
Tell me about eh parasympathetic and the cranial nerve 9
The glossopharyngeal cranial nerve
What produces the lateral horns
The presence of numerous preganglionic sympathetic neurons in the gray matter of the spinal cord. The visceral motor zone.
Tell me about the sacral outflow of nerve for the parasympathetic division
The rest of the large intestine and the pelvic organs are served by the sacral outflow, which arises from neurons located in the lateral gray matter of spinal cord segments S2-S4
Thermoregulation in the body, is cause by
The sympathetic division mediates reflexes that regulate body temperature.
Why is the sympathetic division more complex than the parasympathetic division?
The sympathetic division supplies not only the visceral organs in the internal body cavities but also all visceral structures in the superficial part of the body. -sweat glands -arrector pili
What happens when the systemic body temperature falls?
The sympathetic nerve causes the skin's blood vessels to constrict, and as a results it allows the warm body to be restricted to vital organs
Where is the only segment of the spinal cord that sympathetic fibers arises from?
The thoracic region and the lumbar region. T1-L2 The thoracolumbar region
Tell me about the parasympathetic and the cranial nerve 10
The vagus cranial nerve.
Tell me about the preganglionic axons of the parasympathetic division?
They extend from the CNS nearly all the way to the structure to be innervated. Then they synapsed with the terminal ganglia that lie very close to target organs. Hence the very short postganglionic axon.
What doe most sympathetic postganglionic axons release?
They release Norepinephrine
Where are muscarinic receptors found?
This receptors are found on all effector cells stimulated by postganglionic cholinergic fibers That is, -all parasympathetic target organs - a few sympathetic target organs (sweat glands, blood vessels)
What are adrenergic receptors?
Those receptors for norepinephrine.
What is a major different in anatomical aspect regarding the lateral horns between parasympathetic and sympathetic?
Parasympathetic does not contain lateral horns in the sacral region, since it does not have enough preganglionic nerve. Sympathetic contains lateral sacral horns in the T1-L2 regions of the spinal cord since it contains a larger amount of preganglionic neurons.
Differences in their unique origin sites from para to sympathetic
Parasympathetic fibers emerge from the brain and sacral spinal cord Sympathetic fibers emerge from the thoracolumbar region of the spinal cord
Differences in the relative length of their fibers of para to sympathetic
Parasympathetic, has longer preganglionic and short postganglionic fibers Sympathetic, has shorter preganglionic and longer postganglionic fibers
What is the major actor in controlling blood pressure, even at rest?
sympathetic division. Since the vascular system is entirely innervated by sympathetic fibers that keep the blood vessels in continual state.
What is the sympathetic tone?
is the action of the sympathetic division in keeping the blood vessels in continual state of partial constriction.
What is the overall job of the sympathetic system?
it mobilizes the body during extreme situations
What is the overall job of the parasympathetic system?
it performs maintenance activities and conserves body energy
Differences in the location of their ganglia in the para and sympathetic
parasympathetic, most ganglia are located in the visceral effector organ (since postganglionic fibers are short) Sympathetic, ganglia lie close to the spinal cord. Since preganglionic are very short
tell me about nicotinic receptors
part of the cholinergic receptors. Nicotinic receptors are found on 1- motor end plates of skeletal muscle cells (are somatic not autonomic targets) 2- All ganglionic neurons, both sympathetic and parasympathetic. 3- The hormone-producing cells of the adrenal medulla.
In the ANS, who releases the NE and the Ach?
In the ANS The sympathetic system releases the Norepinephrine (NE) The parasympathetic system releases the Acetylcholine (ACh)
What are the two divisions of the ANS?
- Parasympathetic -Sympathetic They generally serve the same visceral organs but cause essentially opposite effects.
What are the two major neurotransmitter released by the ANS?
-Acetylcholine -Norepinephrine
What is the unique role of sympathetic division?
-The adrenal medulla -The sweat glands -arrector pili -the kidneys -most blood vessels They all only receive sympathetic fibers
What organs exhibit parasympathetic tone?
-heart -smooth muscle of digestive tract -smooth muscle of urinary tract.
What does the vagus nerve innervate?
-liver -gallbladder -stomach -small intestine -kidneys -pancreas -proximal part of large intestine
What are the two cholinergic receptors?
-nicotinic receptors -muscarinic receptors
What is the autonomic nervous system?
A system of motor neurons that innervates smooth and cardiac muscle and glands.
What is the name of norepinephrine releasing fibers called?
Adrenergic fibers
What is the difference between SNS and ANS regarding the neurotransmitter effects?
All SNS release acetylcholine at their synapses with skeletal muscle fibers, hence the effect is always excitatory. The ANS postganglionic axon releases onto visceral effectors organs Norepinephrine and Acetylcholine.
Where do the preganglionic fibers of the sympathetic division arise from?
All arse from cell bodies of preganglionic neurons in spinal cord segments T1-L2
What are preganglionic neurons?
Are the first neurons in a two neuron chain for the ANS. They are lightly myelinated, thin fibers
What are the postganglionic neurons?
Are the second neurons in the two neuron chain for the ANS. They are even thinner when compared to the first neuron, and are unmyelinated.
What is the role of the sympathetic division?
Called the "fight-or-flight" system, its activity is evident when we are excited of find ourselves in emergency or threatening situations.
What is the role of the parasympathetic division?
Called the "resting and digesting" system, keeps the body energy use as low as possible, even as it directs vital housekeeping like digestion and elimination of feces and urine.
What happens when Norepinephrine binds to the Alpha adrenergic receptors?
In general, NE when bound to Alpha adrenergic receptors creates an stimulatory effect
What happens when norepinephrine binds to Beta adrenergic receptors?
In general, NE when bound to Beta adrenergic receptors creates an inhibitory effect.
What is the different between ANS and SNS in their effectors
SNS stimulates skeletal muscle ANS innervates cardiac, smooth muscle and glands
What is the different between ANS and SNS in their efferent pathways and ganglia?
SNS, motor neurons cell bodies are in the CNS,and their axons extend in spinal nerve all the way to the skeletal muscle they activate. ANS, is a two neuron chain. The cell body of the first neuron (the preganglionic neuron) resides in the brain or spinal cord. Its axon (gthe preganglionic axon) synapses with the second motor neuron, the ganglionic neuron in the autonomic ganglion outside of the CNS. The axon of the ganglionic neuron, postganglionic axon, extends to the effector organ.
where is message faster, in the SNS or the ANS?
Since in the ANS you required the message to travel via a two neuron chain, this tend to be slower when compared to the SNS where you only have one neuron which delivers the message.
Which produces a more lasting effect? Para or sympathetic ?
Sympathetic activation are much longer-lasting than parasympathetic effects.
Who releases renin in the kidneys?
Sympathetic impulses stimulate the kidneys to release renin, an enzyme that promotes an increase in blood pressure.
What happens when systemic body temperature is elevated?
Sympathetic nerve causes the skin's blood vessels to dilate, allowing the skin to become flushed with warn blood, and activate the sweat glands to help cool of the body
What is the only exception to the sympathetic postganglionic axons regarding their release of neurotransmitters
Sympathetic postganglionic fibers innervating -sweat glands -some blood vessels in skeletal muscle -external genitalia They all release acetylcholine in the postganglionic axons.
Differences in the degree of branching of preganglionic fibers
Sympathetic, extensive branching of preganglionic fibers Parasympathetic, minimal branching of preganglionic fibers
Does the SNS contain ganglia?
Yes but only on the sensory not on the motor. The somatic motor division lacks ganglia. The dorsal root ganglia are part of the sensory, not the motor division of the PNS
What are the nerves that the parasympathetic supplies to the head
cranial nerve 3, 7, 9 Oculomotor cranial nerve 3 Facial cranial nerve 7 Glossopharyngeal cranial nerve 9 However only the preganglionic fibers lie within these three pairs of cranial nerve. Their postganglionic fibers do not. The preganglionic axons branched with he trigeminal nerve (5) to synapse then the postganglionic fibers travel in the trigeminal nerve to reach the face. This is because the trigeminal nerve has a better coverage of the facial distribution
What are antagonistic interactions of the ANS?
ex In the fight-or-fight situation, the sympathetic division increases respiratory and heart rates, while inhibiting digestion and elimination When emergency is over, the parasympathetic division restores heart and breathing rates to resting levels and then attends to processes that refuel body cells.
What is special about the cranial nerve 10 regarding the parasympathetic system?
the two vagus nerve account for about 90% of all preganglionic parasympathetic fibers in the body. They serve virtually every organ in the thoracic and abdominal cavities.