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61 Cards in this Set

  • Front
  • Back
Three divisions of the ANS
Parasympathetic → rest and digest
Sympathetic → fight or flight
Enteric → brain of the gut
Sympathetic and Parasympathetic Autonomic Ganglia
Relay stations between CNS and organs
- Sympathetic: paravertebral chain of ganglia parallels spinal cord, but there are a few more distal prevertebral ganglia (celiac, splanchic, mesenteric)
- Parasympathetic ganglia are at the organ of innervation
The Sympatho-Adrenal System
Adrenal Gland located above kidneys has an outer cortex (secretes steroid hormones) and an inner medulla (secretes Epi and NE in response to sympathetic stimulation) – different functions, different embryonic origins. The adrenal medulla is like a sympathetic ganglion and its cells are unique neuroendocrine cells → permits global sympathetic stimulation of all cells in the body via the bloodstream
Sympathetic: Spinal origin, Fiber types, Activation
Origin: thoracolumbar spine (C8-L12)
Fibers: short pre-ganglionic, long post-ganglionic
Activation: discharges as a unit (mass activation)
Parasympathetic: Spinal origin, Fiber types, Activation
Origin: craniosacral (CN III, VII, IX, X=vagus nerve), (S2-S4)
Fibers: long pre-ganglionic, short post-ganglionic
Activation: discreet activation of specific targets
Sympathetic systemic effects and response
"Catabolic → mediates release of Epi and NE from adrenal medulla, which can affect entire organism. Mediates the fight or flight response.
Parasympathetic systemic effects and response
"Anabolic → modulates sympathetic neurotransmission through muscarinic cholinergic receptors on sympathetic post-gang. neurons, no mass activation (can ↓ HR without affecting bladder activity, for example). Systems are in opposition and continuously adjust in response to the changing environment.
Enteric nervous system
Controls GI motility and secretion and is comprised of submucosal, myenteric, and subserosal plexuses. Its activity is modulated by the sympathetic (inhibits) and parasympathetic (activates) systems, but denervation studies have shown the enteric NS can maintain function independent of any other autonomic innervation.
Autonomic nerve baseline firing rate
Refers to the level of activity (frequency of depolarization) of an autonomic nerve → helps maintain a "resting tone" or basal level of stimulation in a tissue or organ.
The baseline rate is ↑ or ↓ in response to stimuli in order to maintain homeostatic balance.
ANS innervation of organs
Most tissues receive innervation from both the SNS and PNS
Some receive innervation ONLY from the SNS
Control of BP is primarily sympathetic
Organs that receive innervation from the SNS only
Adrenal medulla
Kidney
Pilomotor muscles
Sweat glands
Parasympathetic stimulation effects - "DUMBBELSS + Abd cramping"
Diarrhea
Urination
Miosis
Bradycardia
Bronchoconstriction
Lacrimation
Erection
Salivation
Sweating
Abdominal cramping
Baroreceptor reflex responses
Drugs that ↑ BP produce reflex bradycardia
Drugs that ↓ BP produce reflex tachycardia
Baroreceptor reflex mechanims
↑ arterial pressure activates stretch receptors in aortic arch and carotid sinus → initiates afferent impulses to brain stem vasomotor center (VMC). Via solitary tract fibers, the VMC activates the vagal motor nucleus, which ↑ vagal (parasympathetic) outlfow and slows heart. At the same time, the VMC ↓ stim of spinal intermediolateral neurons that activate SNS pregang fibers, and this ↓ SNS stim of heart and blood vessels. So, drugs that ↑ BP produce reflex bradycardia and those that ↓ BP attenuate this response causing reflex tachycardia.
Sympathetic (adrenergic) response and primary receptors:
Heart
Rate: ↑, β1
Force: ↑, β1
Sympathetic (adrenergic) response and primary receptors:
Blood vessels
Arteries: vasoconstriction, α1
Skeletal muscles: vasodilation, α1/β2
Sympathetic (adrenergic) response and primary receptors:
Bronchial
Bronchodilation, β2
Sympathetic (adrenergic) response and primary receptors:
Uterus
Contraction, α1
Sympathetic (adrenergic) response and primary receptors:
Vas deferens
Contraction, α1
Sympathetic (adrenergic) response and primary receptors:
GI tract
Relaxation α2
Sympathetic (adrenergic) response and primary receptors:
Eye
Rad. muscle (iris): contraction, α1
Circ. Muscle (iris): none
Ciliary muscle: relaxation, β2
Net effect: mydriasis
Sympathetic (adrenergic) response and primary receptors:
Kidney
Renin secretion, β1
Sympathetic (adrenergic) response and primary receptors:
Pancreas
↓ insulin secretion, α2
Sympathetic (adrenergic) response and primary receptors:
Urinary bladder
Detrusor: relaxation, β2
Trigone/Sphincter: contraction, α1
Sympathetic (adrenergic) response and primary receptors:
Ureter
Relaxation, M3
Sympathetic (adrenergic) response and primary receptors:
Fat cells
Lipolysis, β3
Sympathetic (adrenergic) response and primary receptors:
Liver
↑ glycogenolysis, α1/β2
Sympathetic (adrenergic) response and primary receptors:
Nasal secretions
Decreased, α1
Sympathetic (adrenergic) response and primary receptors:
Salivary secretions
Decreased, α1
Sympathetic (adrenergic) response and primary receptors:
Sweat glands
Decreased, α1
Parasympathetic (cholinergic) response and primary receptors:
Heart
Rate: ↓, M2
Force: ↓, M2
Parasympathetic (cholinergic) response and primary receptors:
Blood vessels
Arteries: little effect
Skeletal muscles: little effect
Parasympathetic (cholinergic) response and primary receptors:
Bronchial
Bronchoconstriction, M3
Parasympathetic (cholinergic) response and primary receptors:
Uterus
Variable response
Parasympathetic (cholinergic) response and primary receptors:
Vas deferens
None
Parasympathetic (cholinergic) response and primary receptors:
GI tract
Contraction, M3
Parasympathetic (cholinergic) response and primary receptors:
Eye
Rad. muscle (iris): none
Circ. Muscle (iris): contraction, M3
Ciliary muscle: contracion, M3
Net effect: miosis
Parasympathetic (cholinergic) response and primary receptors:
Kidney
None
Parasympathetic (cholinergic) response and primary receptors:
Pancreas
None
Parasympathetic (cholinergic) response and primary receptors:
Urinary bladder
Detrusor: contraction, M3
Trigone/Sphincter: relaxation, M3
Parasympathetic (cholinergic) response and primary receptors:
Ureter
Relaxation, M3
Parasympathetic (cholinergic) response and primary receptors:
Fat cells
Little effect
Parasympathetic (cholinergic) response and primary receptors:
Liver
Little effect
Parasympathetic (cholinergic) response and primary receptors:
Nasal secretions
Increased, M3
Parasympathetic (cholinergic) response and primary receptors:
Salivary secretions
Increased, M3
Parasympathetic (cholinergic) response and primary receptors:
Sweat glands
Increased, M3
Organs with a dominant cholinergic response
Heart
Lungs
GI tract
Ciliary and Circ. Muscles of the eye
Detrusor of the urinary bladder
Secretory glands (nasal, salivary, sweat)
Organs with a dominant adrenergic response
Blood vessels
Uterus
Vas deferens
Radial muscles of the eye
Kidney
Pancreas
Ureter
Adipocytes
Liver
Locations of cholinergic neurotransmission
All preganglionic neurons of the entire ANS are cholinergic (nicotinic), and all parasympathetic postganglionic neurons are cholinergic (muscarinic)
Metabolism of acetylcholine
Choline acetyltransferase is synthesized in the cell body & transported to axon terminals which are high in mito →abundance of AcetylCoA substrate. Choline is taken up by active transport from the extracellular fluid. Uptake of choline is rate-limiting step in ACh synthesis. ACh is synthesized in cytoplasm. High and low affinity transporters for choline in axon terminal. High affinity transporter is unique to cholinergic neurons and is dependent on extracellular Na+. The transporter recycles choline from the synapse. ACh is stored in vesicles of the axon terminals. Concentration of ACh in vesicles is ATP dependent. Note that the ACh is RECYCLED by cholinesterase
Acetylcholinesterase (AChE)
Removes ACh from the synapse by degradation to choline + acetate → terminates neurotransmission at cholinergic synapses
Time required is less than 1 millisecond
Sympathetic/Parasympathetic cross-reactivity
Some cholinergic systems have M1 autoreceptors on the presynaptic neuron, for negative feedback regulation of firing. These receptors can also be involved in drug reactions and rarely, one branch (para or symp) can affect the other branch via these receptors.
Muscarinic ACh receptors
Locations: autonomic ganglia, sympathetic effector neurons (pre-synaptic, inhibitory), pre-synaptic autoreceptors, parasympathetic neuroeffector junctions and CNS
High affinity for muscarine
Second messenger-operated (G protein coupled)
Able to regulate (inhibit) sympathetic system
Nicotinic ACh receptors
Locations: sympathetic and parasympathetic ganglia, skeletal muscle, CNS
High affinity for nicotine
Ligand gated ion channels (Na+)
Does not regulate parasympathetic system
Muscarinic ACh receptors: Gq coupled subtypes
M1: sympathetic presynaptic neuroeffectors
M3: bladder, eye, lungs, vasculature
M5: locations, pathways, and effects not well known
Note: M3 receptors are present in vasculature despite the fact that there is no parasympathetic innervation of vasculature, reason is unknown.
Muscarinic ACh receptors: Gi coupled subtypes
M2: heart
M4: locations, pathways, and effects not well known
Properties of Muscarinic Cholinergic Receptors: M1 -"neural"
Principal location: Parasympathetic, pre-synaptic autoreceptors, CNS (note that all 5 subtypes on neurons of CNS)
Signal transduction: Increased IP3 and DAG
Effects: Modulation of neurotransmissioncognition in CNS
Properties of Muscarinic Cholinergic Receptors: M2 - "cardiac"
Principal location: Cardiac tissue (sinoatrial & AV nodes) & smooth muscle, some in CNS
Signal transduction: Increased K+ efflux or decreased cAMP, Hyperpolarization
Effects: Slowing of heart rate and conduction
Properties of Muscarinic Cholinergic Receptors: M3 - "glandular"
Principal location: Smooth muscle & glands, some in CNS
Signal transduction: Increased cGMP due to NO stimulation
Effects: Vasodilation
Properties of Nicotinic Cholinergic Receptors: Nn - "neuronal"
"Principal location: Autonomic Ganglia, Adrenal medulla
Signal transduction: Increased Na+ Influx – Depolarization (excitatory)
Effects: Excitation of postganglionic neurons, increased release of NE in sympathetic system, ACh in parasympathetic. Release of Epi and NE at adrenal medulla
Properties of Nicotinic Cholinergic Receptors: Nm - "muscular"
"Principal location: Somatic Neuromuscular Junctions
Signal transduction: Increased Na+ Influx – Depolarization (excitatory)
Effects: Contraction of muscles