C HAPTER 16 A UTONOMIC N ERVOUS S YSTEM You should read and outline the chapter yourself to best understand the material!!

OBJECTIVES Compare & contrast the characteristics of the somatic and autonomic nervous system Know the divisions of the autonomic nervous system and the characteristics of each Know the affect of the sympathetic and parasympathetic systems for cardiac muscles, glands, ciliary muscle, bronchi, digestive organs, and blood vessels Know the origination site of the sympathetic neurons Know the origination site of the parasympathetic neurons Know the location of the adrenergic neurons Know the types & location of the adrenergic receptors Know the location of the cholinergic neurons Know the types & location of cholinergic receptors

C OMPARE & C ONTRAST S OMATIC AND A UTONOMIC N ERVOUS S YSTEM SOMATICAUTONOMIC Cell bodies ( somatic motor neurons ) in CNS Cell bodies ( preganglionic neurons ) in CNS Axons ( somatic motor neurons) in skeletal muscle Axons ( preganglionic neurons) extend to ganglia where they SYNAPSE with postganglionic neurons Axons of postganglionic neurons extend to smooth muscle, cardiac muscle or glands Excitory effectExcitory OR inhibitory effect VoluntaryInvoluntary

O RGANIZATION OF N ERVOUS S YSTEM Enteric Division

PNS PNS has both sensory & motor neurons Sensory Neurons – carry action potentials from periphery to CNS Motor Neurons – carry action potentials from CNS to periphery PNS Motor Neurons Sensory Neurons

C OMPARISON OF S OMATIC VS A UTONOMIC N ERVOUS S YSTEM (T ABLE ON PAGE 559) CharacteristicSomatic Nervous SystemAutonomic Nervous System EffectorsVoluntary (skeletal) muscle Smooth muscle, Cardiac Muscle, Glands General functionAdjustment to external environment. Adjustment within the internal environment (homeostasis) Number of neurons from CNS to effector 12 Ganglia outside the CNS0 Chain ganglia, collateral ganglia or terminal ganglia NeurotransmitterAcetylcholine Acetylcholine, adrenaline, noradrenaline Effect of nerve damage on the effector Paralysis and muscle wastage (atrophy) Effector remains functional but not able to quickly respond to the changing needs of the body.

S TRUCTURE OF THE A UTONOMIC N ERVOUS S YSTEM Autonomic Nervous System SympatheticParasympatheticEnteric Nerve plexus within wall of digestive tract Sympathetic & Parasympathetic DIFFER: 1)Location of preganglionic neuron cell bodies within CNS 2)Location of their autonomic ganglia

FOR REVIEW Ganglia – tissue mass made of nerve cells A ganglion is a junction between two neurons in the Autonomic Nervous System in which storage,release,synthesis and degradation of the neurotransmitters are done. Nerve Plexus – network of intersecting nerves Preganglionic Neuron Postganglionic Neuron

SYMPATHETIC DIVISION

A NATOMY OF S YMPATHETIC D IVISION Cell bodies of the preganglionic neurons are in the lateral horns of the spinal cord gray matter between T1 and L2 segments The axons of the preganglionic neurons exit through the ventral roots of the spinal nerves for a short distance and project to the sympathetic ganglia

Preganglionic Neuron lateral horn T1 thru L2 gray matter exit through ventral root REVIEW SLIDE

S YMPATHETIC AXON ARE NOW IN THE SYMPATHETIC CHAIN GANGLIA …… H OW DO THEY GET OUT ?

S YMPATHETIC A XONS EXIT THE SYMPATHETIC CHAIN BY 4 POSSIBLE ROUTES 1) Spinal Nerves Preganglionic axon synapse with postganglionic neurons IN the synaptic chain ganglia 2) Sympathetic Nerves Preganglionic axons enter sympathetic chain and synapse IN a sympathetic chain ganglion with post ganglionic neurons Postganglionic neurons for sympathetic nerves which supply organs in thoracic cavity

Splanchnic (splangk-nic) nerves Preganglionic axons PASS THROUGH sympathetic chain ganglia and will form splanchnic nerves and synapse with postganglionic nerves OUTSIDE of the chain in COLLATERAL GANGLIA Innervation to the Adrenal Gland Preganglionic axons PASS THROUGH the chain AND PASS THROUGH the Collateral Ganglia and they synapse with cells in the medulla of the adrenal gland

R EMEMBER …… THE A DRENAL G LANDS ?

PARASYMPATHETIC DIVISION

Cell Bodies of parasympathetic preganglionic neurons are located either: Within the cranial nerve nuclei of brainstem Within the lateral parts of the gray matter in the sacral region of the spinal cord from S2 to S4

Notice in the Parasympathetic Division, the preganglionic axons synapse at the TERMINAL GANGLIA with the postganglionic neurons Postganglionic neurons travel a short distance to the effectors

E NTERIC N ERVOUS S YSTEM Consists of NERVE PLEXUSES within the wall of the digestive tract Plexuses have contributions from 3 sources: Sensory neurons that connect digestive system with CNS ANS motor neurons that connect CNS to digestive tract Enteric Neurons which are confined to Enteric Plexuses UNIQUE – enteric neurons are capable of monitoring and controlling the digestive tract independently of the CNS through local reflexes REMEMBER….. A nerve plexus is a network of intersecting nerves.

NEUROTRANSMITTE RS

Sympathetic & Parasympathetic Nerve Endings secrete one of two neurotransmitters: ACETYLCHOLINE Nerve that secretes this NT is called a CHOLINERGIC NEURON NOREPINEPHERINE (or EPINEPHERINE) Nerve that secretes this NT is called an ADRENERGIC NEURON {once believed to secrete adrenaline (aka: epinepherine)} CHOLINERGIC NEURONS Preganglionic SYMPATHETIC Neurons Preganglionic PARASYMPATHETIC Neurons Postganglionic PARASYMPATHETIC Neurons ADRENERGIC NEURONS Postganglionic SYMPATHETIC Neurons (most)

N EUROTRANSMITTER “LIKE” S UBSTANCES The following substances play a role in regulating the ANS, but it is unclear exactly how. They act as neurotransmitters or neuromodulators. These “chemicals” have also been found (in addition to epi and acety) in the ANS. Nitric oxide Fatty acids Eicosanoids Peptides Gastrin Somatostatin Cholecystokinin Vasoactive intestinal peptide Enkephalines Substance P Monoamines Dopamine Serotonin Histamine

R ECEPTORS FOR N EUROTRANSMITTERS Receptors for acetylcholine and norepinephrine are located in the plasma membrane of certain cells. Depending on the type of cell, the response to these NT can be excitatory or inhibitory. There are two types of receptors: CHOLINERGIC RECEPTORS Receptors to which acetylcholine bind (there are two types) NICOTINIC RECEPTORS MUSCARINIC RECEPTORS ADRENERGIC RECEPTORS Receptors to which norepinephrine or epinephrine bind

N ICOTINIC R ECEPTORS ( A TYPE OF C HOLINERGIC R ECEPTOR ) Respond to the Neurotransmitter: Acetylcholine Located in ALL POSTGANGLIONIC NEURONS in Autonomic ganglia AND the membranes of ALL SKELETAL MUSCLE CELLS EXCITATORY EFFECT since it results in opening of Na + channels which will produce an action potential

M USCARINIC R ECEPTORS ( A TYPE OF C HOLINERGIC R ECEPTOR ) Respond to the Neurotransmitter: Acetylcholine LOCATION: found on cells of ALL PARASYMPATHETIC EFFECTORS and some sympathetic effectors Response: Excitatory or Inhibitory (depending on effector in which receptors are found) ACh binds to muscarinic receptors in cardiac muscle which will REDUCE heart rate ACh binds to muscarinic receptors in smooth muscle of stomach INCREASING rate of contraction

A DRENERGIC R ECEPTOR Receptors to which Norepinephrine or Epinephrine bind LOCATION: Plasma membrane of Effectors innervated by the Sympathetic Division Stimulated by: Nervous System Epinephrine & Norepinephrine released from Adrenal Gland Subdivided into: Alpha ( α) Receptors Beta ( β) Receptors

GENERALIZATIONS! BOTH divisions of ANS produce stimulatory & inhibitory effects Most organs are innervated by BOTH divisions Usually each division produces an OPPOSITE effect on a given organ Sympathetic Division produces more GENERALIZED effects than the parasympathetic division Sympathetic division generally prepares the body for PHYSICAL ACTIVITY Parasympathetic division is more important in RESTING FUNCTIONS

A FFECT OF S YMPATHETIC & P ARASYMPATHETIC S YSTEMS FOR C ERTAIN E FFECTORS ( PAGE 567) EFFECTORSympatheticParasympathetic Cardiac Muscle Increase rate and force of contraction (beta) Decreased rate of contraction(m) Glands: Adrenal Release epi & norepi (n)None Pancreas Decrease insulin (alpha)Increase Insulin (m) Salivary Constrict blood vessels and slight production of thick saliva (alpha) Dilation of blood vessels and thin, copious saliva (m) Ciliary Muscle (eye) Relaxation for far vision (beta)Contraction for near vision (m) Bronchi Dilated air passage (beta)Constricted air passage (m) Digestive Organs: Wall Decreased tone (alpha and beta)Increased motility (m) Sphincter Increased tone (alpha)Decreased tone (m) Blood Vessels Constriction (alpha) Dilation (beta) none

INFLUENCE OF DRUGS

D RUGS Direct Acting – bind to ACS receptors to produce an effect Agonists (stimulating agents) – bind to specific receptors and activate them Antagonists (blocking agents) – bind to specific receptors and prevent them from being activated

NICOTINE Present in tobacco Nicotine STIMULATES the Postganglionic neuron of BOTH Sympathetic and Parasympathetic Divisions, its effects VARY Heart Rate may increase or decrease Heart Rhythm becomes less regular Blood Pressure Increases (due to constriction of Blood Vessels) Drugs that BLOCK nicotine receptors are called Ganglionic Blocking Agents, because they block the effect of Ach on neurons Trimethaphancamsylate is used to treat high BP, it blocks the sympathetic stimulation of blood vessels causing blood vessels to dilate which decrease blood pressure (problem: act on both sym and parasym ganglia, so not the best drug choice to use)

D RUGS THAT BIND TO MUSCARINIC RECEPTORS