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PPP > L5: ANS > Flashcards

L5: ANS Flashcards

1
Q

The ANS controls important visceral functions

A

“automatic functions”
– Heart rate
– Blood pressure
– Digestion
– Glandular secretion
– Sweating
– Pupillary aperture

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2
Q

General Organization
of the Nervous System: Anatomy

A

Nervous System

  1. Central NS: brain and spinal cord
  2. Peripheral NS: cranial and spinal nerves
    - Autonomic NS: not under direct conscious control, innervates internal organs/glands/smooth and cardiac muscles
    - Somatic NS: motor portion concerned with conscious functions, innervates SKM
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3
Q

Sensory (afferent) neurons

A

ARRIVING
-Transmit information about external and internal environments from periphery to CNS

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4
Q

Motor (efferent) neurons

A

EXITING
-Transmit “instructions” from CNS to periphery

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5
Q

ANS and SNS neurons

A

ANS: visceral sensory and motor neurons

SNS: somatic sensory and motor neurons

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6
Q

Structure of Motor Neurons

A
  • Dendrites receive input from adjacent neurons -> soma
  • Information transmitted from soma along axon in form of an action potential
  • Nerve terminal synthesizes a neurotransmitter (NT) and stores it in vesicles
  • When action potential arrives at nerve terminal, NT is released by exocytosis
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7
Q

Neurotransmission in the ANS

A

ANS motor neurons: mostly 2 neuron system (from CNS to Effector cell)

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8
Q

Neurotransmission in the SNS

A

SNS motor neurons: one neuron system

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9
Q

Functions of the ANS

A
  • Controls:
    – Cardiac muscle
    – Smooth muscle
    – Secretory glands

*Sympathetic: Fight or Flight
*Parasympathetic: Rest and Digest

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10
Q

Fight or Flight

A
  • pupil dilation
  • bronchodilation
  • sweating
  • inc. heart rate / contractile force
  • blood glucose
  • dec. GI motility, inc. SM sphincter tone
  • dec. bladder SM tone, inc. SM sphincter
  • vasoconstriction in viscera
  • vasodilation in skeletal muscle
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11
Q

Rest and Digest

A
  • pupil constriction
  • bronchoconstriction
  • dec. heart rate
  • inc. GI motility, dec. SM sphincter tone
  • inc. bladder SM tone, dec. SM sphincter tone
  • inc. glandular secretions
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12
Q

Only the sympathetic division innervates and controls:

A
  • Most blood vessels
  • Sweat glands
  • Adrenal medulla
  • Ventricles (very little parasympathetic input)
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13
Q

Sympathetic division - Thoracolumbar division

A

Preganglionic neurons
Somas
-Thoracic and lumbar spinal cord
Fibers
* Spinal nerves T1-L2/L3
* Branch extensively (widespread responses)

Postganglionic neurons
Somas
-In peripheral ganglia near spinal cord
* Paravertebral ganglia
* Prevertebral ganglia
Fibers
* Usually longer than preganglionic fibers

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14
Q

Parasympathetic division - Craniosacral division

A

Preganglionic neurons
Somas
-In brain stem and sacral spinal cord
Fibers
* In cranial nerves III, VII, IX, X and spinal nerves S2-S4
* Limited branching (= localized responses)

Postganglionic neurons
Somas
-In peripheral ganglia near innervated structures
* Terminal ganglia
* Intramural ganglia
Fibers
* Usually shorter than preganglionic fibers

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15
Q

Autonomic NTs

A

Acetylcholine (ACh)
-all synapses in peripheral ganglia
-all NEJs in parasympathetic division
-some NEJs in sympathetic division (most sweat glands)
-all NMJs in SNS

Norepinephrine (NE) (aka Noradrenaline)
-most NEJs in sympathetic division
-exceptions: sympathetic NEJs with cholinergic transmission
-Most sweat glands <- sympathetic cholinergic

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16
Q

Neurochemistry of the Adrenal Medulla

A

ANS motor neurons: mostly 2 neuron system
-Exception: Adrenal medulla
(= Specialized peripheral ganglion)
-Cells are homologous to autonomic postganglionic neurons (without postganglionic fibers!)

-Adrenal medulla secretes EPI and small amounts of NE
-EPI and NE are secreted into the blood, to function as neurohormones
-Responses to sympathetic stimulation include effects of EPI and NE from the adrenal medulla

17
Q

Neurotransmission Steps

A
  1. Synthesis and storage of NT
  2. Release of NT by exocytosis
  3. Diffusion of NT to postsynaptic cell
  4. Binding of NT to receptors on postsynaptic cell, initiating a response
  5. Termination of action of NT

Important mechanisms:
* Enzymatic inactivation of NT
* Reuptake of NT by presynaptic fiber

18
Q

ACh: Enzymatic Inactivation

A

Rapid hydrolysis by acetylcholine esterase (AChE

19
Q

NE Reuptake

A

-Transport back into nerve terminal by NET (Na+- dependent amine transport system)
-Re uptake allows “recycling” of NE

20
Q

Enzymatic Inactivation of ACh is _____ than Reuptake of NE

A

FASTER

Sympathetic
* Produces sustained responses

Parasympathetic
* Produces responses of short duration

21
Q

Cholinergic Receptors

A

nAChRs
(nicotinic acetylcholine receptors)
- ligand gated ion channels

mAChRs
(muscarinic acetylcholine receptors)
- GPCRs

22
Q

Soma in ____
Ganglia in ____

A

Soma in CNS
Ganglia in PNS

Soma - preganglionic neuron - synapse - postganglionic axon

23
Q

First neurotransmitter is always

A

ACh

-Parasympathetic and Somatic will release ACh as well

-Sympathetic will release NE
-EXCEPT in sweat glands (release ACh)

24
Q

nAChRs

A
  1. Binding of ACh to nAChR
  2. Opening of ion channel
  3. Na+ influx
  4. Depolarization of postsynaptic membrane
    EPSP

Everything Nn except SKM (Nm)

25
Q

mAChRs

A

M2: Gi
-Effector cells at parasympathetic NEJs
-Inhibition of heart

M3: Gq
-Effector cells at parasympathetic NEJs: smooth muscle contraction + glandular secretion
-At sympathetic cholinergic NEJs: sweating

26
Q

Alpha 1

A

Gq
smooth muscle contraction

27
Q

Alpha 2

A

Gi
presynaptic receptor, modulatory functions

28
Q

Beta 1

A

Gs
stimulation of heart, increase renin secretion

29
Q

Beta 2

A

Gs
smooth muscle relaxation, metabolic effects (epi from medulla)

30
Q

ACh is the neurotransmitter in peripheral ganglia in

A

BOTH the sympathetic division and the parasympathetic division

31
Q

NE is the neurotransmitter at most _____

A

-sympathetic NEJs
the adrenergic term, which does NOT apply to the peripheral ganglia of the sympathetic division

32
Q

Extensive branching of preganglionic fibers is a characteristic of the

A

sympathetic division

(not the parasympathetic division)

33
Q

The peripheral ganglia are close to (or in the walls of) the effector organs in…

A

in the parasympathetic division

-so preganglionic fibers are long while the postganglionic fibers are short

34
Q

the peripheral ganglia are relatively close to the spinal cord (paravertebral ganglia, prevertebral ganglia), in the…

A

in the sympathetic division

-so the preganglionic fibers are short while the postganglionic fibers are long

35
Q

in the ____, the termination of ACh’s effects at NEJs is accomplished by enzymatic hydrolysis of ACh by AChE, which is extremely ___

A

in the parasympathetic division

fast

36
Q

the termination of NE’s effects at _____ NEJs is accomplished primarily by reuptake of NE by NET, which is relatively ____

A

sympathetic division

slow

37
Q

the _____ has exclusive control of a greater number of effector organs. Most importantly, most _____ are controlled exclusively by the ____

A

the sympathetic division
-most blood vessels and all sweat glands are controlled exclusively by the sympathetic division
-adrenal medulla also

38
Q

the dominant tone at rest to most effector organs is

A

parasympathetic
-most important exceptions are the blood vessels and sweat glands (sympathetic)

PPP (15 decks)

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