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Home , Ramus communicans, White ramus communicans

1/18/2016

Peripheral Nerve Regeneration

• Possible if cell body has not been damaged • underlying sheath can regenerate The

PNS continued

Endoneurium Schwann cells 1 The axon 2 Macrophages Macrophage Droplets becomes clean out the of myelin fragmented at dead axon distal the injury site. to the injury.

Fragmented axon Site of nerve damage

Figure 13.4 (1 of 4) Figure 13.4 (2 of 4)

Aligning Schwann cells 3 Axon sprouts, Schwann cell Site of new 4 The axon form regeneration tube or filaments, myelin sheath regenerates and grow through a formation a new myelin regeneration tube sheath forms. formed by Schwann cells.

Fine axon sprouts Single enlarging or filaments axon filament

Figure 13.4 (3 of 4) Figure 13.4 (4 of 4)

1 1/18/2016

Neuritis Shingles

• Inflammation of a nerve • Varicella Zoster virus – Sciatica • Dorsal root ganglia – Bell’s Palsy • Consistent with dermatome • Vaccine

Multiple Sclerosis

• Loss of myelin in CNS ‰ scleroses (CNS) Peripheral nervous system (PNS) – Visual disturbances

Muscle weakness Sensory (afferent) Motor (efferent) division – division • Autoimmune disorder Somatic nervous system (ANS) • Remissions

Sympathetic Parasympathetic • Progressive division division

Figure 14.1

Autonomic Nervous System (ANS) Structure of the ANS

• Involuntary óSensory (afferent) pathway • Sensory (afferent) pathways ó Visceral interoceptors (visceroceptors) • Motor (efferent) pathways ° Osmolarity ° Pressure • Visceral reflex system ° Temperature ° Blood gases ° Chemical composition of plasma and body fluids

2 1/18/2016

Structure of the ANS Dorsal root (sensory) Dorsal root Dorsal horn () Somatic • Sensory (afferent) pathway sensory – Single sensory from organ to CNS neuron Visceral • Cell body in sensory • with association in spinal cord neuron Visceral motor neuron Ventral horn Ventral root (motor neurons) Somatic (motor) Interneurons receiving input from somatic sensory neurons

Interneurons receiving input from visceral sensory neurons

Visceral motor (autonomic) neurons

Somatic motor neurons

Figure 12.32

Autonomic Nervous System (ANS) Autonomic Nervous System (ANS)

• ANS Motor (efferent) neurons • Efferent (motor) pathway – Innervate smooth muscle, cardiac muscle and – Two motor neurons between CNS and effector glands • Preganglionic neuron – Operate via subconscious control – Cell body in CNS • Postganglionic neuron – Cell body in (outside CNS)

Motor Pathways

Neuro- Autonomic Nervous System (ANS) Cell bodies in central transmitter Effector nervous system Peripheral nervous system at effector organs Effect Single neuron from CNS to effector organs ACh + • Visceral reflex system Stimulatory

SYSTEM Heavily myelinated axon SOMATIC NERVOUS Skeletal muscle – E.g., coughing, sneezing, swallowing, vomitting Two-neuron chain from CNS to effector organs

ACh NE

Unmyelinated postganglionic axon Lightly myelinated Ganglion Epinephrine and preganglionic norepinephrine + ACh

SYMPATHETIC Stimulatory or inhibitory, depending Adrenal medulla Blood vessel on neuro- transmitter and ACh ACh Smooth muscle receptors (e.g., in gut), on effector

AUTONOMIC NERVOUS SYSTEM NERVOUS AUTONOMIC organs Lightly myelinated Unmyelinated glands, cardiac preganglionic axon Ganglion postganglionic muscle axon PARASYMPATHETIC

Acetylcholine (ACh) Norepinephrine (NE)

Figure 14.2

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Stimulus

1 Sensory receptor Dorsal root ganglion in viscera 2 Visceral sensory Spinal cord Central nervous system (CNS) Peripheral nervous system (PNS) neuron

3 Integration center Sensory (afferent) Motor (efferent) division division ó Spinal cord ó Within gastrointestinal tract wall Somatic nervous Autonomic nervous system system (ANS) Autonomic ganglion Efferent pathway 4 Sympathetic Parasympathetic (two-neuron chain) division division • Preganglionic neuron • Ganglionic neuron 5 Visceral effector A simple visceral reflex arc

Response Figure 14.7 Figure 14.1

Dual Innervation Divisions at a Glance Parasympathetic Sympathetic Eye Eye Brain stem Salivary Skin* glands Cranial Salivary Sympathetic Sympathetic Parasympathetic glands • • ganglia Heart – “Fight or Flight” – “Rest and Digest” Cervical Lungs Lungs – NE and acetylcholine – Acetylcholine T 1 Heart

– Thoracolumbar – Craniosacral Stomach Thoracic Stomach Pancreas Liver Pancreas and gall- L1 bladder Liver and Adrenal gall- Lumbar gland bladder

Dual Innervation Bladder Bladder Genitals Genitals Sacral

Figure 14.3

Parasympathetic Division Outflow

Nerve Ganglia Effector Organ(s) Cranial (Terminal Ganglia) Outflow Oculomotor (III) Ciliary Eye

Facial (VII) Pterygopalatine Salivary, nasal, and Submandibular lacrimal glands Glossopharyngeal Otic Parotid salivary glands (IX) Vagus (X) Within the walls of Heart, lungs, and most target organs visceral organs Within the walls of Large intestine, Sacral S2-S4 target organs urinary bladder, Outflow ureters, and reproductive organs

4 1/18/2016

Eye CN III Lacrimal gland CN VII Pterygopalatine CN IX ganglionganglion Nasal CN X mucosa Submandibular and sublingual glands Parotid gland Central nervous system (CNS) Peripheral nervous system (PNS) Heart Cardiac and Parasympathetic pulmonary plexuses Lung Sensory (afferent) Motor (efferent) division Division division

Liver and Celiac gallbladder Somatic nervous Autonomic nervous plexus = Craniosacral system system (ANS) Stomach

Pancreas Sympathetic Parasympathetic S2 division Large division S4 intestine

Pelvic Small splanchnic intestine nerves Inferior Rectum hypogastric plexus Urinary Genitalia Preganglionic bladder (penis, Postganglionic and ureters clitoris, and vagina) Cranial nerve

Figure 14.4 Figure 14.1

Sympathetic Division = Thoracolumbar Eye Lacrimal gland Pons Nasal mucosa The Sympathetic Division (chain) ganglia Blood vessels; Superior skin (arrector pili cervical muscles and ganglion sweat glands) Salivary glands Middle Preganglionic neurons originate in the spinal cervical • ganglion Heart Inferior cervical Cardiac and cord from T –L ganglion pulmonary Lung 1 2 T1 plexuses Greater splanchnic nerve – Thoracolumbar division Lesser splanchnic nerve Liver and Celiac ganglion gallbladder • FYI: Lateral horns L 2 Stomach White rami Superior communicantes mesenteric Spleen ganglion Adrenal medulla Kidney Sacral Lumbar Small splanchnic Inferior Preganglionic intestine nerves mesenteric (Sympathetic) ganglion Large intestine Cell Bodies Rectum

Preganglionic Postganglionic

Genitalia (uterus, vagina, and penis) and urinary bladder

Figure 14.6

Spinal cord The Sympathetic Division Dorsal root 1) Ventral root 2) Spinal nerve 1) Preganglionic fibers leave through ventral root of spinal cord 3) Ventral ramus

4) White

2) Fibers join spinal nerve 5) Sympathetic trunk ganglion Sympathetic trunk 3) Spinal nerve divides at ventral rami Rib

Gray ramus communicans 4) Rami branch immediately into white rami communicans

Thoracic splanchnic nerves 5) Join sympathetic (paravertebral) ganglia (a) Location of the sympathetic trunk

Figure 14.5a

5 1/18/2016

Sympathetic Division = Thoracolumbar Eye Lacrimal gland Sympathetic Trunk Ganglia Pons Nasal mucosa Sympathetic trunk (chain) ganglia Blood vessels; Superior skin (arrector pili cervical muscles and ganglion sweat glands) Salivary glands • Form longitudinal pathways adjacent to vertebral column Heart • Each spinal nerve has an associated ganglion (except in cervical Inferior cervical Cardiac and ganglion pulmonary Lung T1 region, where several ganglia fuse) plexuses

Greater splanchnic nerve Lesser splanchnic nerve Liver and Celiac ganglion gallbladder

L 2 Stomach White rami Superior communicantes mesenteric Spleen ganglion Adrenal medulla Kidney Sacral splanchnic nerves Lumbar Small splanchnic Inferior intestine nerves mesenteric ganglion Large intestine Rectum

Preganglionic Postganglionic

Genitalia (uterus, vagina, and penis) and urinary bladder

Figure 14.6

The Sympathetic Division Lateral horn (visceral motor zone) Dorsal root Dorsal root ganglion • Sympathetic trunks and pathways Dorsal ramus of spinal nerve –Upon entering a sympathetic trunk ganglion a Ventral ramus of spinal nerve preganglionic fiber may do one of the following: Skin (arrector Gray ramus 1. Synapse with a ganglionic neuron within the same ganglion pili muscles communicans Ventral root and sweat White ramus Sympathetic glands) communicans trunk ganglion Sympathetic trunk To effector 1 Synapse at the same level

Blood vessels

(b) Three pathways of sympathetic innervation

Figure 14.5b (1 of 3)

Sympathetic Trunks and Pathways

• Sympathetic trunks and pathways

–Upon entering a sympathetic trunk ganglion a Skin (arrector preganglionic fiber may do one of the following: pili muscles and sweat 2. Ascend or descend the sympathetic trunk to glands) synapse in another trunk ganglion To effector

Blood vessels 2 Synapse at a higher or lower level

(b) Three pathways of sympathetic innervation

Figure 14.5b (2 of 3)

6 1/18/2016

Sympathetic Trunks and Pathways

• Sympathetic trunks and pathways –Upon entering a sympathetic trunk ganglion a preganglionic fiber may do one of the following: 3. Pass through the trunk ganglion and emerge Splanchnic nerve without synapsing Collateral ganglion (such as the celiac)

Target organ in (e.g., intestine) 3 Synapse in a distant collateral ganglion anterior to the vertebral column (b) Three pathways of sympathetic innervation

Figure 14.5b (3 of 3)

Spinal cord Sympathetic Trunks and Pathways Dorsal root Ventral root • Sympathetic trunks and pathways Rib

–Upon entering a sympathetic trunk ganglion a Sympathetic preganglionic fiber may do one of the following: trunk ganglion Sympathetic 3. Pass through the trunk ganglion and emerge trunk without synapsing Ventral ramus of spinal nerve » Eventually synapse with post-ganglionic neurons in collateral ganglia, enter an autonomic plexus, and innervate abdominal viscera White ramus » Form splanchnic nerves communicans Thoracic splanchnic nerves (a) Location of the sympathetic trunk

Figure 14.5a

Differences Between the Divisions Neurotransmitters in the ANS

• Cholinergic fibers release the neurotransmitter ACh Origin of Length of Location Division – All ANS preganglionic axons Fibers Fibers of Ganglia – All parasympathetic postganglionic axons Sympathetic Thoracolumbar Short Close to region of the preganglionic spinal cord • Adrenergic fibers release the neurotransmitter NE spinal cord and long postganglionic – Most sympathetic postganglionic axons

Parasympathetic Brain and Long In visceral – Exceptions: sympathetic postganglionic fibers sacral spinal preganglionic effector secrete ACh at sweat glands and some blood vessels cord and short organs (craniosacral) postganglionic in skeletal muscles

7 1/18/2016

Adrenal Medulla

Two-neuron chain from CNS to effector organs

ACh NE

Unmyelinated Ganglion postganglionic axon Lightly myelinated Epinephrine and + preganglionic axons norepinephrine ACh

SYMPATHETIC Stimulatory or inhibitory, depending Adrenal medulla Blood vessel on neuro- transmitter and ACh ACh Smooth muscle receptors (e.g., in gut), on effector

AUTONOMIC NERVOUS SYSTEM NERVOUS AUTONOMIC organs Lightly myelinated Unmyelinated glands, cardiac preganglionic axon Ganglion postganglionic muscle axon PARASYMPATHETIC

Acetylcholine (ACh) Norepinephrine (NE)

“Sympathomimetic”

Figure 14.2

Receptors for Neurotransmitters Cholinergic Receptors

• Cholinergic receptors for ACh • Two types of receptors bind ACh • Adrenergic receptors for NE 1. Nicotinic 2. Muscarinic • Named after drugs that bind to them and mimic ACh effects

Cholinergic Receptors Cholinergic Receptors

• Nicotinic receptors ó Muscarinic – Blocked with curare ôBlocked by atropine • Poison arrows and blow darts ôEffect of ACh at muscarinic receptors • Used as a muscle relaxant for surgery (safer alternatives ˜Can be either inhibitory or excitatory now available) ˜Depends on the receptor type of the target organ – Effect of ACh at nicotinic receptors • Always stimulatory Clarification, PNS 8: 2d. acetylcholine is not always stimulatory. It IS always stimulatory at nicotinic and somatic receptors. It may be inhibitory or excitatory at muscarinic receptors.

8 1/18/2016

Adrenergic Receptors

• Two types – Alpha ( α) (subtypes α1, α2) – Beta ( β) (subtypes β1, β2, β3)

• Effects of NE depend on which subclass of Ignore receptor predominates on the target organ

Ignore

Table 14.2

Cardiovascular Pharmacology Cardiovascular Pharmacology

• Heart • Adrenergic blockers – β1 - Excitatory in heart – Used to treat hypertensive disease • increases heart rate, conduction velocity, and contraction – α1 blockers - produce vasodilation strength – β1 blockers - decrease heart rate and blood • Major blood vessels pressure – β2 – Inhibitory • Vasodilation – α1 – Excitatory • Vasoconstriction

Interactions of the Autonomic Parasympathetic Sympathetic Eye Eye Brain stem Divisions Salivary Skin* glands Cranial Salivary Sympathetic • Most visceral organs have dual innervation glands ganglia Heart • Dynamic and precise control of visceral activity Cervical Lungs Lungs T – Sympathetic division increases heart and respiratory 1 Heart rates, and inhibits digestion and elimination Stomach Thoracic – Parasympathetic division decreases heart and Stomach Pancreas Liver respiratory rates, and allows for digestion and the Pancreas and gall- L1 bladder discarding of wastes Liver and Adrenal gall- Lumbar gland bladder

Bladder Bladder Genitals Genitals Sacral

Figure 14.3

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