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Home , Gray ramus communicans, Neuroeffector junction, Ramus communicans, Sacral ganglia

Autonomic

Organization of Nervous System:

Nervous system

Integration Peripheral nervous system (CNS) (PNS)

Motor Sensory output input Brain Spinal cord Motor division Sensory division (Efferent) (Afferent)

“self governing” Somatic Nervous System (Involuntary; smooth & (Voluntary; skeletal muscle) cardiac muscle) Stability of internal environment depends largely on this system

Marieb & Hoehn – Figure 14.2 Autonomic Nervous System : Comparison of Somatic vs. Autonomic: A group of cell bodies located in the PNS

Cell body Effector

location NTs organs Effect

CNS Single from CNS to effector organs ACh + Heavily myelinated Stimulatory

Somatic NS Somatic Skeletal muscle

ACh = Acetylcholine

Two-neuron chain from CNS to effector organs CNS

ACh Ganglion NE

Postganglionic axon Preganglionic axon (unmyelinated) (lightly myelinated)

Sympathetic + Stimulatory

Autonomic NS Autonomic or inhibitory

CNS Ganglion (depends ACh ACh on NT and NT receptor , Type) Postganglionic glands, cardiac Preganglionic axon axon muscle Parasympathetic (lightly myelinated) (unmyelinated) NE =

Autonomic Nervous System

Organization of Nervous System:

Nervous system

Integration Central nervous system Peripheral nervous system (CNS) (PNS)

Motor Sensory output input Brain Spinal cord Motor division Sensory division (Efferent) (Afferent)

Autonomic Nervous System Somatic Nervous System (Involuntary; smooth & (Voluntary; skeletal muscle) cardiac muscle)

Sympathetic division Parasympathetic division

1 Autonomic Nervous System

Divisions of Autonomic Nervous System (ANS): 1) Sympathetic Division: (“fight or flight”) • Readies body for stressful situations • Heightens mental alertness •  heart rate / blood pressure •  metabolic rate •  respiratory rate / bronchiole dilation • Activates energy reserves • Activates sweat glands • Dampens non-essentials (e.g., digestion)

2) Parasympathetic Division: (‘rest and digest”) • Conserves energy at rest •  metabolic rate •  digestive motility / blood flow •  heart rate / blood pressure • Stimulates defecation / urination •  digestive gland secretions

Autonomic Nervous System Sympathetic division also called the thoracolumbar division Sympathetic Division Anatomy: • Sympathetic pathways have short preganglionic fibers and long postganglionic fibers

• Preganlionic fibers originate in spinal cord between cord segments T1 – L2

• Autonomic ganglia located close to spinal cord (arranged as sympathetic chain)

• 23 ganglia / chain ( 3 cervical, 11 thoracic, T1 4 lumbar, 4 sacral, 1 coccygeal)

L2

Sympathetic chain

Marieb & Hoehn – Figure 14.5 / 14.6

Autonomic Nervous System

Sympathetic Division Anatomy: Pathways in sympathetic chain: 1) Terminate directly in sympathetic chain Spinal • Postganglionic exit out Lateral horn of gray (unmyelinated spinal cord axons) 2) Ascend / descend several segments Gray ramus before terminating communicans

Ventral root

Sympathetic chain ganglion (paravertebral ganglion) • May ascend / descend to ganglia located outside T1 – L2

White ramus : (fed via T1 – T6) communicans Rami communicantes only Serve head / (myelinated axons) associated with sympathetic division : (fed via T10 – L2) Serve genitalia / urinary bladder Marieb & Hoehn – Figure 14.5

2 Autonomic Nervous System

Sympathetic Division Anatomy: Pathways in sympathetic chain: 3) Exit sympathetic chain before terminating in collateral (prevertebral) ganglia

Cervical ganglia

Collateral T1 ganglion

Celiac ganglion

L2

Adrenal medulla • Form splanchnic (fed via T5 – L2)

Sacral Celiac ganglion: ganglia Serves upper abdominal cavity Mesenteric • Pass-through point for splanchnic ganglia Spanchnic nerve feeding adrenal medulla nerves Mesenteric ganglia: Serve lower abdominal cavity Marieb & Hoehn – Figure 14.5 / 14.6

Autonomic Nervous System Paraympathetic division also called the craniosacral division Parasympathetic Division Anatomy:

• Sympathetic pathways have long preganlionic fibers and short postganlionic fibers • Terminal ganglia located near effector tissue • Preganglionic fibers originate in brain stem Vagus and S – S : nerve 2 4 • Occulomotor Nerve (III) • Ciliary ganglia: Pupillary sphincters / ciliary muscles • Facial Nerve (IIV) • Pterygopalatine ganglia: Nasal / lacrimal glands • Submandibular ganglia: Salivary glands

• Glossopharyngeal Nerve (IX) S2

S4 • Otic ganglia: Salivary gland Splanchnic 90% of • Vagus Nerve (X) nerves PNS fibers • Intramural ganglia: Visceral organs

• Sacral Segments (S2 – S4): • Intramural ganglia: Large intestine / bladder / Marieb & Hoehn – Figure 14.4 genitalia

Autonomic Nervous System

ANS Physiology: Fiber Types: • Fibers: Synthesize / secrete acetylcholine (NT) • All preganglionic fibers (sympathetic and parasympathetic divisions) • Postganglionic fibers of parasympathetic division

• Adrenergic Fibers: Synthesize / secrete norepinephrine (NT) • Postganglionic fibers of sympathetic division (sans sweat glands / piloerector muscles)

Synthesis of : • NTs synthesized / stored in varicosities of nerve fibers

3 Autonomic Nervous System

• Postganglionic neuron forms diffuse, branching ANS Physiology: networks at of ANS: • NTs released from varicosities (“beads”) • Innervation by multiple ANS fibers may occur • Postsynaptic receptors spread across target

Varicosities

Smooth muscle Autonomic cells nerve fiber

Remember: Precision strike vs. Saturation bombing

Synaptic vesicles Marieb & Hoehn – Figure 9.27

Autonomic Nervous System

ANS Physiology: Fiber Types: • Cholinergic Fibers: Synthesize / secrete acetylcholine (NT) • All preganglionic fibers (sympathetic and parasympathetic divisions) • Postganglionic fibers of parasympathetic division

• Adrenergic Fibers: Synthesize / secrete norepinephrine (NT) • Postganglionic fibers of sympathetic division (sans sweat glands / piloerector muscles)

Synthesis of Neurotransmitters: • NTs synthesized / stored in varicosities of nerve fibers Removal: Acetyl-CoA + Choline Tyrosine 1) Reuptake (~ 80%) hydroxylation 2) Diffusion (~ 20%) choline 3) Destruction (> 1%) acetyltransferase Dopa monoamine oxidase decarboxylation Acetylcholine • Catalyzed by acetylcholinesterase Dopamine • Choline recycled… hydroxylation Norepinephrine

Autonomic Nervous System Nature of receptor dictates effects of NTs ANS Physiology: Receptor Types: -linked A) Adrenoreceptors (bind E / NE): receptor systems • Located on target tissues of sympathetic nervous system

4 Autonomic Nervous System

ANS Physiology: Receptor G – protein Receptor Systems: G protein Effector • Receptors interact with G-proteins to trigger cellular event Cellular response A. Receptors:

• 7 trans-membrane segments (each segment = similar –helix sequences)

• Interact with various G-proteins depending on sequence of 3rd intracellular loop Wolfe – Figure 4.3

Autonomic Nervous System

ANS Physiology: Receptor G – protein Receptor Systems: G protein Effector • Receptors interact with G-proteins to trigger cellular event Cellular response B. G proteins: • Composed of three unique sub-units (, , ) • No intrinsic enzymatic activity; activates enzymes

G protein Activation:

1) Ligand binds to receptor

2) Receptor / G protein interact • GDP (-subunit) replaced by GTP; dissociation occurs

3) -subunit activates effector

Hydrolysis of GTP to GDP causes –subunit to dissociate from effector and rejoin other subunits

Autonomic Nervous System

ANS Physiology: Receptor G – protein Receptor Systems: G protein Effector • Receptors interact with G-proteins to trigger cellular event Cellular response C. Effectors:

A) Adenylate cyclase (2nd messenger – cAMP)

Activated by Inhibited by

GS proteins GI proteins

Lodish – Figure 20.20

5 Autonomic Nervous System

ANS Physiology: Receptor G – protein Receptor Systems: G protein Effector • Receptors interact with G-proteins to trigger cellular event Cellular response C. Effectors:

A) Adenylate cyclase (2nd messenger – cAMP) • Synthesizes cAMP from ATP Methylxanthines (e.g., caffeine) Inactivates cAMP

Autonomic Nervous System

ANS Physiology: Receptor G – protein Receptor Systems: G protein Effector • Receptors interact with G-proteins to trigger cellular event Cellular response C. Effectors:

A) Adenylate cyclase (2nd messenger – cAMP) Diacylglycerol nd B) Phospholipase C (2 messengers – IP3 / DAG) (DAG)

++ • IP3 activates release of Ca (ER) • DAG activates protein kinase

Inositol triphosphate (IP3)

Phosphoinositol (PIP)

Wolfe – Figure 6.6 / 6.9

Autonomic Nervous System Nature of receptor dictates effects of NTs ANS Physiology: Receptor Types: G protein-linked A) Adrenoreceptors (bind E / NE): receptor systems • Located on target tissues of sympathetic NS • Divided into two types:  and β receptors

(most common)

1 receptors 2 receptors

Effect: (+) Excitatory (+) Effect: (-) Inhibitory (-)

Location: Vascular smooth muscle - skin Location: Membrane of adrenergic (constricts blood vessels) axon terminals (inhibits NE release) / bladder Gastrointestinal tract (constricts sphincters) (inhibits GI function) Phenylephrine Pancreas ( agonist) Iris of eye 1 (dilates pupil of eye) (inhibits insulin secretion)

Mechanism G protein coupled to Mechanism GI protein coupled to of Action: phosphorylase C of Action: adenylate cyclase

6 Autonomic Nervous System Nature of receptor dictates effects of NTs ANS Physiology: Receptor Types: G protein-linked A) Adrenoreceptors (bind E / NE): receptor systems • Located on target tissues of sympathetic NS • Divided into two types:  and β receptors

1 receptors 2 receptors

Effect: (+) Excitatory (+) Effect: (-) Inhibitory (-)

Location: Predominately in the heart Location: Vascular smooth muscle - skeletal (increases contraction rate / strength) (dilates vessels) muscle

Kidney Lungs (triggers renin (hormone) release) (dilates bronchioles)

Propanolol Albuterol Gastrointestinal tract (β-blocker) (2 agonist) (relaxes GI tract)

Mechanism GS protein coupled to Mechanism GS protein coupled to of Action: adenylate cyclase of Action: adenylate cyclase

Autonomic Nervous System Nature of receptor dictates effects of NTs ANS Physiology: Activated by Receptor Types: nicotines Activated by toxins A) Adrenoreceptors (bind E / NE): from toadstools atropine (muscarinic antagonist) B) Cholinoreceptors (bind ACh): • Located on postganglionic / target tissues of parasympathetic NS • Divided into two types: nicotinic & muscarinic Nicotinic Muscarinic

Effect: (+) Excitatory (+) Effect: (+) Excitatory (+) & (-) Inhibitory (-)

Location: Motor end plate – skeletal muscle Location: Parasympathetic organs – sans heart (contracts skeletal muscle) (excites activity)

All postganglionic neurons G protein coupled to + Heart (activate postgangionic neurons) K channel… (inhibits heart rate)

Chromaffin cells – adrenal medulla Sweat glands – sympathetic NS (triggers release of E / NE) (activates sweat glands)

Mechanism Mechanism G protein coupled to of Action: Ligand-gated of Action: phosphorylase C (Majority of locations)

Autonomic Nervous System

ANS Physiology:

Muscarinic Parasympathetic receptors

Visceral dffector cell

Cholinergic fibers Nicotinic receptors

Visceral effector cell

Autonomic Adrenergic fibers ganglion Sympathetic Adrenergic receptors (α / β)

7 Autonomic Nervous System

ANS Physiology:

Costanzo – Figure 2.1

Autonomic Nervous System

ANS Physiology: Control of Autonomic Functioning:

A) Brain stem / Spinal cord • Vasomotor center (cardiovascular) • Respiratory center • Micturition center (urination) • Swallowing / coughing / vomiting B) Hypothalamus • Main integration center • Body temperature • Water balance • Food intake • Links emotion with ANS C) Cortical control • Links emotional past with ANS • Voluntary cortical ANS control possible

Costanzo – Figure 2.4

Autonomic Nervous System Sympathetic = “fight or flight” Parasympathetic = “rest and digest” ANS Physiology: Interactions of Autonomic Divisions: A) Antagonistic Interactions: Systems do not ‘compete’ with each other; coordinated by nervous system • Pupil: • Parasympathetic = Constriction (circular fibers) • Sympathetic = Dilation (meridional fibers)

• Heart (sinoatrial node): • Parasympathetic = Decrease heart rate • Sympathetic = Increase heart rate

B) Synergistic Interactions:

• External genitalia • Parasympathetic = Vasodilation of blood vessels (erection of tissue) • Sympathetic = Smooth muscle contraction (ejaculation / reflex contraction) * Tone: Blood vessels under sympathetic tone • Basal rate of activity present in a system Decrease output = vasodilation of vessel • Allows increase / decrease by single system Increase output = vasoconstriction of vessel

8 Autonomic Nervous System Sympathetic = “fight or flight” Parasympathetic = “rest and digest” ANS Physiology: Interactions of Autonomic Divisions: C) Coordinated Function within Organ: Sympathetic Parasympathetic • Bladder: • Filling = Relaxed detrusor muscle; contracted internal sphincter • Emptying = Contracted detrusor muscle; relaxed internal sphincter

Costanzo – Figure 2.4

Autonomic Nervous System

Adrenal Medulla: • Large sympathetic ganglion

Cortex Medulla • Postganglionic cells = Chromaffin cells

• Releases catecholamines (epinephrine (80%) and norepinephrine (20%))

methylation

• Catecholamines transported via blood (= hormone) • Delayed effect (3 – 5 sec.); prolonged effect (2 – 4 min. to clear from system) • Stimulation of cardiovascular function / metabolic rate (helps deal with stress) • Perceived purpose: 1) Safety factor (dual mechanism – backs up sympathetic nervous system) 2) Stimulate structures not directly innervated (e.g., every cell of body…)

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