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Topic 3: Peripheral Nervous System
Lecture 1 Introduction
→ Anatomy and physiology
→ Neurotransmitters
→ Receptors and drugs
Autonomic nervous system: Sympathetic vs. Parasympathetic
The peripheral nervous system is in close relationship with the central nervous system. It consists of
cranial and spinal nerves and can be divided into a sensory (afferent) and motor (efferent) part.
Efferent signals can be sent to the outside. In the motor division, there are two motors: the somatic
and visceral motor system.
- Somatic: neurons that target skeletal muscles. If you want to raise your arm, the somatic
motor becomes active.
- Visceral: autonomic nervous system that targets smooth muscle, cardiac muscle and glands.
This is outside our control. The ANS can further be divided into the parasympathetic and
sympathetic systems.
o Parasympathetic: regulates actions that control rest and digest
▪ E.g. Lowers heartbeat
o Sympathetic: fight or flight. Higher heartbeat, faster breathing etc.
o They target similar organs but have different effects. Together they maintain the
body’s normal functioning.
There are always two neurons involved in targeting an organ in the autonomic nervous system. The
location where these two neurons meet is called the autonomic ganglion.
Preganglionic neuron from the spinal cord, CNS to the autonomic ganglion, it releases its
neurotransmitter in the synaptic cleft. This activates the postganglionic neuron that targets the
tissue. The neurotransmitters bind to receptors on the tissue and activate the tissue.
1
,Sympathetic nervous system: targets internal organs.
All preganglionic neurons arise from the lower parts of the CNS: from the thoracic and lumbar part of
the spinal cord. The preganglionic neurons terminate in several ganglia parallel to the spinal cord,
from here the postganglionic neurons arise and go to the target organs.
→ Characteriscs of the sympathetic nervous system is that the ganglia are in a chain parallel to the
spinal cord. The ganglionic chain is not present in the parasympathetic nervous system.
Parasympathetic nervous system:
There are no perivertebral chain ganglia. The ganglia are located very close to the organs or inside
them.
Sympathetic nervous system Parasympathetic nervous system
Innervation of smooth muscle
There is both innervation of sympathetic and parasympathetic neurons of smooth muscle cells for
example on intestine. This is different from innervation of skeletal muscle.
2
, Normally, there is 1 neuron activating 1 fiber: in the case of smooth muscle cells there are many
varicosities from one autonomic nerve fiber, which contain synaptic vesicles. So there is more
neurotransmitter activation by one innervating fiber.
Overview ANS: they usually target the same organs but have the opposite effect.
Distinguish in anatomy and function:
• Anatomical division:
o Sympathetic neurons come from the thoraco-lumbar part of the spinal cord
o Parasympathetic neurons come from the cranio-sacral part of the spinal cord
• Functional division
o Sympathetic – fight & flight
o Parasympathetic – rest & digest
• Pharmacological division: adrenergic and cholinergic neurons
The parasympathetic and sympathetic nervous systems going to various organs use 2 neurons,
preganglionic and postganglionic with different/the same neurotransmitters.
• Parasympathethic: preganglionic & postganglionic → release acetylcholine. These are both
cholinergic.
• Sympathetic: preganglionic → acetylcholine; postganglionic → norepinephrine. Preganglionic
is cholinergic; postganglionic is adrenergic.
o Exception sympathetic innervation: sweat glands. Sympathetic postganglionic
neurons of the sweat glands release also acetylcholine: postganglionic neurons are
also cholinergic.
The somatic motor nervous system going to skeletal muscle only uses 1 neuron with one
neurotransmitter which is acetylcholine. This is a cholinergic neuron.
3
Topic 3: Peripheral Nervous System
Lecture 1 Introduction
→ Anatomy and physiology
→ Neurotransmitters
→ Receptors and drugs
Autonomic nervous system: Sympathetic vs. Parasympathetic
The peripheral nervous system is in close relationship with the central nervous system. It consists of
cranial and spinal nerves and can be divided into a sensory (afferent) and motor (efferent) part.
Efferent signals can be sent to the outside. In the motor division, there are two motors: the somatic
and visceral motor system.
- Somatic: neurons that target skeletal muscles. If you want to raise your arm, the somatic
motor becomes active.
- Visceral: autonomic nervous system that targets smooth muscle, cardiac muscle and glands.
This is outside our control. The ANS can further be divided into the parasympathetic and
sympathetic systems.
o Parasympathetic: regulates actions that control rest and digest
▪ E.g. Lowers heartbeat
o Sympathetic: fight or flight. Higher heartbeat, faster breathing etc.
o They target similar organs but have different effects. Together they maintain the
body’s normal functioning.
There are always two neurons involved in targeting an organ in the autonomic nervous system. The
location where these two neurons meet is called the autonomic ganglion.
Preganglionic neuron from the spinal cord, CNS to the autonomic ganglion, it releases its
neurotransmitter in the synaptic cleft. This activates the postganglionic neuron that targets the
tissue. The neurotransmitters bind to receptors on the tissue and activate the tissue.
1
,Sympathetic nervous system: targets internal organs.
All preganglionic neurons arise from the lower parts of the CNS: from the thoracic and lumbar part of
the spinal cord. The preganglionic neurons terminate in several ganglia parallel to the spinal cord,
from here the postganglionic neurons arise and go to the target organs.
→ Characteriscs of the sympathetic nervous system is that the ganglia are in a chain parallel to the
spinal cord. The ganglionic chain is not present in the parasympathetic nervous system.
Parasympathetic nervous system:
There are no perivertebral chain ganglia. The ganglia are located very close to the organs or inside
them.
Sympathetic nervous system Parasympathetic nervous system
Innervation of smooth muscle
There is both innervation of sympathetic and parasympathetic neurons of smooth muscle cells for
example on intestine. This is different from innervation of skeletal muscle.
2
, Normally, there is 1 neuron activating 1 fiber: in the case of smooth muscle cells there are many
varicosities from one autonomic nerve fiber, which contain synaptic vesicles. So there is more
neurotransmitter activation by one innervating fiber.
Overview ANS: they usually target the same organs but have the opposite effect.
Distinguish in anatomy and function:
• Anatomical division:
o Sympathetic neurons come from the thoraco-lumbar part of the spinal cord
o Parasympathetic neurons come from the cranio-sacral part of the spinal cord
• Functional division
o Sympathetic – fight & flight
o Parasympathetic – rest & digest
• Pharmacological division: adrenergic and cholinergic neurons
The parasympathetic and sympathetic nervous systems going to various organs use 2 neurons,
preganglionic and postganglionic with different/the same neurotransmitters.
• Parasympathethic: preganglionic & postganglionic → release acetylcholine. These are both
cholinergic.
• Sympathetic: preganglionic → acetylcholine; postganglionic → norepinephrine. Preganglionic
is cholinergic; postganglionic is adrenergic.
o Exception sympathetic innervation: sweat glands. Sympathetic postganglionic
neurons of the sweat glands release also acetylcholine: postganglionic neurons are
also cholinergic.
The somatic motor nervous system going to skeletal muscle only uses 1 neuron with one
neurotransmitter which is acetylcholine. This is a cholinergic neuron.
3
