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Physiology > Autonomic nervous system > Flashcards

Autonomic nervous system Flashcards

1
Q

what does somatic nervous system comprise of

A

Motor and sensory pathways regulating voluntary motor control of skeletal muscles

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2
Q

ANS comprise of

A

Motor & sensory pathways regulating the body’s internal environment through involuntary control of organ systems (smooth muscle, cardiac muscle, and glands)
Sympathetic
Parasympathetic

located in CNS and PNS

Coordinates and maintains a steady state among the visceral internal organs

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3
Q

Neurons

A

Preganglionic:
cell body in CNS (myelinated B fibers)
Postganglionic:
cell body in autonomic ganglia (unmyelinated C fibers)

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4
Q

Divisions of ANS

A

Sympathetic
Parasympathetic
+/- Enteric

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5
Q

what are the locations of autonomic centers

A 
Hypothalamus (influenced by connections to limbic system)
Brain stem 
Medulla 
Pons
Spinal Cord
spmbsh
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6
Q

Function of ANS

A 
Controls Visceral Functions(Involuntary smooth muscles,cardiac muscles and Glands funcrtions)
Partial control
Systemic blood pressure
GI motility and secretion
Urinary bladder emptying
Sweating and body temperature
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7
Q

Sympathetic innervation

A

Thoracolumbar: Preganglionic neurons cell bodies located in (T1-L2/3) of spinal cord
Intermediolateral horn of grey matter
Post ganglionic neuron cell bodies are located in ganglia
Paravertebral chains (either side spinal column)
Prevertebral ganglia (i.e. celiac, superior, inferior mesenteric ganglia in abdomen)
Short preganglionic neurons, long post

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8
Q

Mode of action and innervation of Sympathetic Nervous system

A

Mobilizes energy stores in times of need
“Fight or flight response”.

Nerve fibers leave the spinal cord ventrally via white rami and travel to 22 paravertebral ganglia (the sympathetic chain ganglia)
From there they can:
Synapse with post-ganglionic neuron at

  1. same level OR
  2. Move caudad or cephalad
  3. synapse at another level ganglia without synapsing to collateral ganglia surrounding the abdominal aorta (celiac, superior mesenteric, inferior mesenteric)

Some ganglia have inhibitory interneurons as well

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9
Q

Where does the SNS outflow to

A 
Piloerector muscle
sweat gland
Blood vessel
Eye
Heart
bronchi
pylorus
adrenal Medulla
Kidney
ureter
intestine
illeocecal valve
anal sphincter
detrusor
bladder
Hypogastric plexus

celiac ganglion

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10
Q

what do the (Thoracolumbar division) comprise of

A

Post-ganglionic nerve cell bodies found in ganglia of paravertebral chain exit to travel to various peripheral organs
Return to spinal nerves via gray rami travel with these nerves to blood vessels, piloerector muscles and sweat glands

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11
Q

What does the distribution of SNS fibre depend on

A

Distribution of SNS fibers is based on embryonic development and NOT spinal segments
T1 SNS fibers usually ascend into the paravertebral sympathetic chain to head
T2 neck
T3-6 chest
T7-11 abdomen
T12-L2 legs

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12
Q

Patterns of Innervation: PSNS“Rest and Energy Restoration”

A 
Parasympathetic innervation
Pre-ganglionic neurons arise in 
“Cranial” (medullary CN 3,7, 9, 10)
 “Sacral” (spinal cord S2-4) regions
Post-ganglionic neurons cell bodies located in:
Target organs
Discrete ganglia in the head and neck (i.e. ciliary ganglia) 
Long preganglionic neurons, short post
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13
Q

Parasympathetic Nervous System “Craniosacral division”

Functions

A

Functions to conserve and restore energy
“Rest or repose response”
Receives innervation from cell bodies located in:
cranial nerve nuclei (travel via III, V, VII, IX, X)
75% of PSNS fibers are in vagus (X) passing to abdominal and thoracic areas
sacral region of the spinal cord
Preganglionic neurons travel to ganglia close to the organs they innervate

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14
Q

Where does the Parasympathetic Nervous System Craniosacral division innervate

A

Vagus X = PSNS to heart, lungs, esophagus, stomach, small intestine, liver, gallbladder, pancreas, upper uterus
Cranial Nerve III – Edinger-Westphal nucleus: eye
Cranial Nerve V – Submandibular gland
Cranial Nerve VII –Superior salivatory nucleus: lacrimal, nasal, submaxillary glands
Cranial Nerve IX – Inferior salivatory nucleus: parotid gland
S2-3 (sometimes S1-4) – distal colon, rectum, bladder, lower uterus, external genitalia,anal sphincter

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15
Q

Parasympathetic Nervous System Craniosacral division……

Postganglionic neurons include

A

located in cranial ganglia, including:

Ciliary ganglion (preganglionic input is from the Edinger-Westphal nucleus)

Pterygopalatine and submandibular ganglia (input from the superior salivatory nucleus)

Otic ganglion (input from the inferior salivatory nucleus).

Other parasympathetic postganglionic neurons are located near or in the walls of visceral organs in the thoracic, abdominal, and pelvic cavities.

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16
Q

COmpare PSNS vs SNS

A

Often SNS & PSNS actions often (but not always) antagonistic
SNS = self preservation: most important function is maintenance of vasomotor tone
PSNS = rest for the organism but “excitatory” visceral functions such as digestion(Peristalsis and bladder contaction.

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17
Q

slide 13

A

For SNS
saliva drys up
heart pumps
depolarization in the sa node to increase
contractility fast and maximal force
Speed Av node conduction
Bronchioles to dilate
Epinephrine high
Liver to release glucose…Gluconeogenis and Glycogenolysis
no peristalsis
no bladder contraction for urine
anal sphincter nice tone
blood vessel to dialate so skeletal muscle get blood..
veins in leg constricted to get more preload

18
Q

Slide 13

A 
PSNS
Lacrimal gland constrict saliver gland salivate  more
heart slow down
pSNS lung constriction ....b
Bronchoconstriction can happen
bladder constriction
sphincter relaxation
19
Q

How does SNS respond to stress

A

SNS = amplification response with diffuse innervation
Postural changes
Exercise
Emergency massive response- fight or flight

20
Q

How does PSNs respond to stress

A

PSNS = discrete and narrowly targeted responses

21
Q

what does both system exhibit at rest

A

Both systems exhibit“baseline tone” at rest
Heart rate – vagal (at the Sa node)….Ach continuous ly released at the Sa nodes
predominance
Blood vessels- SNS tone

22
Q

Sympathetic Preganglionic fibres release what?

A 
Neurotransmitter = Secrete Acetylcholine
Receptor = Cholinergic (nicotinic – n type)
23
Q

Sympathetic postganglionic fibers

screte what?

A

Neurotransmitter = Secrete Norepinephrine

Receptor Type = Adrenergic

24
Q

Parasympathetic pre- and postganglionic fibers

releasae what

A

Neurotransmitter = Secrete Acetylcholine

Receptor Type = Cholinergic (nicotinic- n-type at ganglia; muscarinic at organ)

25
Q

3 major anomalies (exceptions to the rule)

for release of Neurotransmitter

A

Adrenal medulla (acts like a ganglia but releases NE and Epi as HORMONES)
Norepi 20%
Epi 80%
Sweat glands
Innervated anatomically by SNS
Post ganglionic nerve releases Ach onto a muscarinic Ach receptor
Thus … “sympathetic cholinergic fibers”
Blood vessel smooth muscle
Almost all have no innervation by PSNS
However, there are muscarinic Ach receptors present on the blood vessels (activate NO with eventual vasodilation if you had a situation with circulating Ach)

26
Q 
PNS Receptors subclass
Cholinergic Receptors
A 
Cholinergic Receptors(responde to acetycholine)Parasympathetic side
Nicotinic Ach receptors
Nm and Nn
Muscarinic Ach receptors
M1-5

Adrenergic receptors(responds to NE..sympathetic)
Alpha (1,2)
Beta (1, 2, 3)

27
Q 
PNS Receptors subclass
Adrenergic receptors(responds to NE..sympathetic)
A

 (1,2)

 (1, 2, 3)

28
Q

Mechanism of Action of Neurotransmitters (i.e. norepi, epi, dopamine, acetylcholine)

A

Activation of G-protein coupled receptor (D,Beta and alpha))
NT binds receptor & activates a G-protein
G-protein will activate or inhibit an intracellular enzyme (adenylate cyclase→cAMP, phospholipase C) or will open or close an ion channel
Usually the G-protein “cascade” has an eventual positive or negative effect on the amount of intracellular Ca2+ = physiological effect
Receptor type will dictate the activity of the G protein
Example Beta-1 receptors increase cAMP via G proteins. cAMP stimulates the Na-K pump and protein phosphorylation reactions leading to metabolic and pharmacologic effects we see clinically (increased heart rate and contractility, etc.)

29
Q

Mecahanism of neurotransmitter effect

A

Different parts of the body have different types & densities of receptors (skeletal muscle VS venous smooth muscle VS myocardium VS bronchial smooth muscle etc.)

The specific effect depends on the type of receptor stimulated, receptor density in a given tissue, and what the second messengers activate at a molecular level in the cell.

Receptors will up or down regulate based upon plasma concentrations of catecholamines (endogenous or exogenous)

30
Q

Effects of second messenger on receptors

A

Adenylate cyclase activates cAMP = smooth muscle dilation (Bronchioles blood vessels)
Increased cAMP = vasodilation (also increased strength of cardiac contraction, and increased heart rate)
Decreased cAMP= vasoconstriction
PLC(Phospholipase C) activated activates IP3 & DAG results in increased PKC and increased free Ca2+ = vasoconstriction
* Again… do not forget that The specific effect depends on the type of receptor stimulated, receptor density in a given tissue, and what the second messengers activate at a molecular level in the cell.

31
Q

Know slide 22

A

The Big table

32
Q

Cholinergic Receptor Subtypes

A

Muscarinic and Nicotinic receptors

33
Q

Muscarinic receptors (G-Protein Coupled)

A

Muscarinic receptors (G-Protein Coupled)
M1, M3, M5 inositol phosphate pathway (primarily)
M2, M4 inhibit adenylyl cyclase reduce cAMP (primarily)
M1: CNS, stomach
M2: Widely expressed
cardiac (inotropy/chronotropy), ganglia
smooth muscle bladder, GI, uterus
M3: smooth muscle, glandular tissues, work with M2
M4: CNS (ganglia)
M5: cerebral bld vessels, pupil, esophagus, parotid gland

34
Q

Nicotinic receptors (Pentameric (5 subunit) structures /ligand-gated ion channels

A

Nm: skeletal muscle at NMJ
Nn: autonomic ganglia, adrenal medulla, CNS

All Nn receptors are not parasympathetic.

35
Q

Characteristics of Acetylcholine

Does not have effcet outside the synapse

A

Synthesis
Choline (active transport brings it into the cytoplasm) and acetyl coenzyme A (formed by mitochondria) form acetylcholine under the influence of the enzyme choline acetyltransferase
Storage
Stored in synaptic vesicles released in response to an action potential
Metabolism
Brief effect <1 ms rapid hydrolysis by acetylcholinesterase to choline and acetate
Choline is transported back into nerve endings used for synthesis of new acetylcholine

36
Q

Neurotransmitter effects and selectivity on receptors

A

Norepinephrine* alpha 1,alpha 2,beta 1…….no effect or need alot to activate beta 2

Epinephrine alpha1,alpha 2,beta 1 and beta 2 .release from Medulla

Dopamine D1=D2
need more to affect beta and a lot more for alpha

37
Q

Norepi characteristics

A

Formation
In cytoplasm dopamine formed
Dopamine enters synaptic vesicle
In synaptic vesicle converted to norepinephrine
Storage and Release
Norepi stored in vesicle until action potential
With action potential the norepi is released from postganglionic SNS nerve endings into ECF via exocytosis
Effect of Norepi is affected by reuptake…

Termination of Action
Reuptake back into postganglionic sympathetic nerve endings (#1- 80% of released norepi can be reused)
Dilution by diffusion from receptors
Metabolism by the enzymes monoamine oxidase (MAO- cytoplasm) and catechol-o-methyltransferase (COMT - liver)

38
Q

Epinephrine charateristics

A

Formation - synthesized in the medulla of the adrenal gland (chromaffin cells) in the same enzymatic pathway that coverts the amino acid tyrosine into NE and dopamine (epinephrine is the final step)
Storage and Release – Released after simulation of the adrenal medulla by pre-ganglionic sympathetic neurons by Ach
Termination of Action – COMT and MAO

39
Q

KNow slides 27,30,31

A

pls go through it

40
Q

Adrenal medulla function i

A

Innervated by preganglionic fibers that bypass the paravertebral ganglia
Fibers directly from spinal cord to adrenal medulla
Cells of adrenal medulla are analagous to post-ganglionic neurons
SNS stimulation results in release of catecholamine hormones (released into systemic circulation instead of the synapse)
80% epinephrine
20% norepinephrine

41
Q

Mechanism of action of adrenal medulla

A

Release of epi & norepi by adrenal medulla occurs after acetylcholine is released by preganglionic cholinergic fibers
Acetylcholine increases the permeability of calcium by acting on plasma membrane receptors of adrenal medulla cells
Calcium ions result in the exocytosis of the hormones into systemic circulation
Results = similar to direct stimulation by the SNS however prolonged response 10-30 seconds (COMT)

42
Q

Review slides 33_35

A

…review

Physiology (11 decks)

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