Download Types of Neurons of ANS

To review the different types of neurons associated with
the ANS.
To clearly identify the position and role of the
sympathetic trunk & collateral ganglia.
To address the two different types of receptors for
neurotransmitters of the sympathetic ANS:
- Cholinergic Receptors
- Adrenergic Receptors
To relate how drugs interact (influence) the receptors
seen in the sympathetic ANS.
Types of Neurons of ANS
Ganglion – Collection of nerve cell bodies
outside of the CNS.
Preganglionic Neurons – CB in CNS which
projects its axon to a peripheral ganglion
Postganglionic Neurons – CB in peripheral
ganglion its axon projects to an effector.
Spinal cord
Dorsal root
Sympathetic
Trunk
Ventral root
Rib
Paravertebral
ganglia
3 cervical
11
thoracic
4 lumbar
4 sacral
1
coccygeal
Sympathetic
trunk ganglion
Sympathetic
trunk
Ventral ramus
of spinal nerve
Gray ramus
communicans
White ramus
communicans
Thoracic
splanchnic nerves
(a) Location of the sympathetic trunk
Figure 14.5a
Pathways with Synapses in
Collateral Ganglia
Most fibers from T5 – L2 synapse in collateral ganglia
They form thoracic, lumbar, and sacral splanchnic
nerves
Their ganglia include the celiac and the superior and
inferior mesenteric
Neurotransmitter Effects
All somatic motor neurons release acetylcholine (ACh)
Effects are always stimulatory
ANS
Preganglionic fibers release ACh
Postganglionic fibers release norepinephrine or ACh at
effectors
Effect is either stimulatory or inhibitory, depending on
type of receptors
SYMPATHETIC
NE
ACh
PARASYMPATHETIC
AUTONOMIC NERVOUS SYSTEM
Two-neuron chain from CNS to effector organs
Somatic nervous system
Acetylcholine (ACh)
Ganglion
Lightly myelinated
preganglionic axons
ACh
Unmyelinated
postganglionic axon
Epinephrine and
norepinephrine
Adrenal medulla
Blood vessel
ACh
ACh
Lightly myelinated
preganglionic axon
Ganglion
+
Unmyelinated
postganglionic
axon
Smooth muscle
(e.g., in gut),
glands, cardiac
muscle
Stimulatory
or inhibitory,
depending
on neurotransmitter
and
receptors
on effector
organs
Norepinephrine (NE)
Figure 14.2
Neurotransmitters
Cholinergic Receptors
I. Cholinergic fibers release the neurotransmitter
ACh
Two types of receptors bind ACh
II. Adrenergic fibers release the neurotransmitter
NE
Nicotinic (stimulatory)
Found on:
All ganglionic neurons both (sympath & para)
Motor end plates of skeletal muscle cells
Hormone-producing cells of the adrenal medulla
2. Muscarinic (inhibitory or excitatory)*
Found on:
All effector cells stimulated by postganglionic
cholinergic fibers
* depends on target
organ
1.
All ANS preganglionic axons
All parasympathetic postganglionic axons
Most sympathetic postganglionic axons
Exceptions: sympathetic postganglionic fibers secrete
ACh at sweat glands and some blood vessels in skeletal
muscles
Adrenergic Receptors
Two types
Alpha (α) (subtypes α1, α2) - Excitatory
Beta (β) (subtypes β1, β2 , β3)
Effects of NE depend on which subclass of receptor
predominates on the target organ.
β1 – increases heart activity
β2 – relaxes smooth muscle of bronchioles
Table 14.2
Effects of Drugs
Over-the-counter drugs for colds, allergies, and nasal
congestion
Stimulate α-adrenergic receptors
Beta-blockers
Drugs that attach to β2 receptors to dilate lung
bronchioles in asthmatics; other uses
Table 14.2
Stimulus
Visceral Reflexes
Visceral reflex arcs have the same components as
somatic reflexes
Main difference: visceral reflex arc has two neurons in
the motor pathway
Visceral pain afferents travel along the same pathways
as somatic pain fibers, contributing to the
phenomenon of referred pain
1 Sensory receptor
in viscera
2 Visceral sensory
neuron
3 Integration center
• May be preganglionic
neuron (as shown)
• May be a dorsal horn
interneuron
• May be within walls
of gastrointestinal tract
Dorsal root ganglion
Spinal cord
Autonomic ganglion
4 Efferent pathway
(two-neuron chain)
• Preganglionic neuron
• Ganglionic neuron
5 Visceral effector
Response
Figure 14.7
HW for Week 4
Due in lab:
Diseases & Disorders of the nervous system W.S.
Labeling:
pg 337 (spinal cord)
pg. 378 (eye)
Study Guide will be provided for in lab (Tuesday)
Preview dissection of eye and eye related reflexes.