ANS Flashcards
Autonomic System overview
Motor and sensory pathways regulating body’s internal environment through involuntary control
* Sympathetic
*Parasympathetic
Preganglionic neurons
Cell body in the CNS
(myelinated B fibers)
Postgangliotic neuron
Cell body in autonomic ganglia (outside CNS)
(unmyelinated C fibers
Activation of ANS
- Visceral information comes in from body to brain
- autonomic centers receive information and initiate response
- Hypothalamus
- “homeostasis”
- Pons
- Respirations
- medulla
- vasomotor tone
- respirations
ANS has partial control of 4 things
- systemic blood pressure
- GI motility and secretion
- urinary bladder emptying
- sweating and body temperature
Structure of sympathetic nervous system
- “Thoracolumbar”
- pregangliotic neurons cell bodies located in T1-L2/3 of spinal cord- in the intermediolateral horn of gray matter.
- short
- post-ganglionic neuron cell bodies are located in the ganglia on either side of the spinal cord.
- long
- pregangliotic neurons cell bodies located in T1-L2/3 of spinal cord- in the intermediolateral horn of gray matter.
SNS paravertebral ganglion T1 affects ______
head
SNS paravertebral ganglion T2 affects _____
neck
SNS paravertebral ganglion T3-6 affects _____
chest
affects phrenic nerve and cardiac accelerant compensation
SNS paravertebral ganglion T7-T11 affects
abdomen
SNS paravertebral ganglion T12-L2 affects ______
legs
parasympathetic preganglionic neurins arise from:
- Cranial
- medullary CN 3, 7, 9, 10
- Sacral
- spinal cord S2-S4 regions
Long preganglionic neurons, short post
Post ganglionic neurons cell bodies of the parasympathetic system are located in:
- target organs
- discrete ganglia in the head and neck
***Long preganglionic neurons, short post
Vagus Nerve (CN X) affects what organs in the parasympathetic nervous system?
- heart
- lungs
- esophagus
- stomach
- small intesting
- liver
- gallbladder
- pancreas
- upper uterus
Occulomotor Nerve (CN III) affects what organs in the parasympatheic nervous system
- eye (the pre-ganglionic nucleus is called the Edinger-Westphal nucleus
Trigeminal (CNV) affects what in the parasympathetic nervous system?
- Submandibular gland (secretions)
Facial nerve (CNVII) affects what in the parasympathetic nervous system?
- lacrimal
- nasal
- submaxillary glands
***pre ganglionic nucleus is calls Superior salivatory nucleus
Glossopharyngeal nerve (CNIX) affects what in the parasympathetic nervous system?
- Parotid gland
***preganglionic nucleus is called the Inferior salivatory nucleus
S2-S3 nerves affect what in the parasympathetic nervous system?
- distal colon
- rectum
- bladder
- lower uterus
- external genitalia
Edinger-Westphal nucleus is preganglionic input for what postganglionic neuron?
Ciliary ganglion
Superior Salivatory nucleus is preganglionic nucleus for what postganglionic neuron?
Pterygopalatine and submandibular ganglia
Inferior salivatory nucleus is preganglionic neuron for what postganglionic neuron?
Otic ganglion
sympathetic preganglionic fibers
neurotransmitter and receptor
Secrete Acetylcholine
Cholinergic (nicotinic)
sympathetic postganglionic fibers
neurotransmitter and receptor
Secrete Norepinephrine
Receptor type: Adrenergic
or
Secrete ACh to muscarinic receptor or adrenal medulla
parasympathetic preganlionic
neurotransmitter and receptor type
secretes Acetylcholine
Receptor: Cholinergic (nicotinic)
parasympathetic postganlionic fibers
neurotransmitter and receptor
secretes Acetylcholine
Receptor type: muscarinic
Adrenal Medulla
acts like a ganglia but releases NE and Epi as hormones
20% NE
80% Epi
sweat glands
- innervated by SNS
- Postganglionic nerve releases ACh into a muscarinic receptor
- thus it is a sympathetic cholinergic fiber ???
Adenylate cyclase activates cAMP causing _____
smooth muscle dilation
Acetylcholine
Synthesis and storage
- Synthesis- Choline and acetyl CoA form acetylcholine with help of choline acetyltransferase
- Storage- stored in synaptic vesicles and released in response to an action potential
metabolism of acetylcholine
- <1 msec rapid hydrolysis by acetylcholinesterase to choline and acetate
- Choline is transported back into nerve endings used for synthesis of new acetylcholine
Creation of Epinephrine
- Tyrosine converted into DOPA by Tyrosine hydroxylase (rate limiting step)
- DOPA converted into Dopamine by DOPA decarboxylase
- Dopamine converted into Norepinephrine by Dopamine Beta-hydroxylase
- Norepi converted into Epinephrine by Phenylethanolamine N-methyltransferase
Norepinephrine
formation and storage
- Formation
- dopamine formed in cytoplasm
- dopamine enters synaptic vesicle
- in vesicle it is converted to Norepi
- storage and release
- Norepi stored in vesicle until AP
- with AP the norepi is released from postganglionic SNS nerve endings into ECF via exocytosis
Norepinephrine
termination of action
- Reuptake- back into postganglionic sympathetic nerve endings
- most common
- 80% of released norepi can be reused
- Dilution- by diffusion from receptors
- metabolism- by the enzymes
- monoamine oxidase (MAO-cytoplasm)
- catechol-o-methyltransferase (COMT-liver)
Epinephrine
formation and storage
- Formation- synthesized in the medulla of the adrenal gland (chromaffin cells)
- Storage and release- released after stimulation of the adrenal medulla by pre-ganglionic sympathetic neurons by ACh
Epinephrine
termination of action
- COMT- liver
- MAO- cytoplasm
what does cAMP do?
relaxes muscles
Gaq
- increases IP3, DAG and Ca++
- Vasoconstriction,
- increased heart contractility
- increased CNS activity
Gai
- decreases cAMP
- smooth muscle contraction
- decreased HR
- decreased contractility
- decreased CNS activity (post synaptically A2)
Gas
- Increased cAMP
- smooth muscle relaxation/vasodilation
- Increased HR
- Increased contractility
