Autonomic Nervous System

Homeostasis Integration Receptors Effectors Feed-back

Somatic vs Autonomic NS

Somatic vs Autonomic Nervous systems Somatic NS Receptors IntegrationEffectors 5 senses Cortex (& assoc.)Skeletal muscles Autonomic NS Receptors IntegrationEffectors Chemo-baro hypothalamus cardiac, Osmo-medulla oblongata smooth Receptors muscles glands

Autonomic Nervous system Two aspects -1 to promote survival - the other to promote in crisis state survival in stable state Sympathetic Parasympathetic Fight or flight Rest and digest

Figure Brain areas involved in controlling the ANS

Functions: Sympathetic Parasympathetic Promote survival in crisis state: - Increase heart rate - Increase breathing rate - Increase blood pressure - Vasoconstriction of peripheral/non- essential blood vessels and - Vasodilation in heart, brain, muscles - Bronchodilation - Iris dilation - Increase blood glucose Decrease digestion -Decrease digestive juice secretion -Decrease digestive tube motility -Promote sphincter closing Opposite of Sympathetic -Promotes digestion -Promotes rest

Figure 11.1 Anatomy of the motor ANS

Motor pathways of the ANS

Sympathetic NS 2 motor neurons Motor neuron 1 in lateral horn of spinal cord between T1 to L3 Motor neuron 2 in the paravertebral ganglia (forming the sympathetic trunk) Acetylcholine (nicotinic receptor) in ganglionic synapse, norepinephrine at the organ synapse Nerve pathways mixed with somatic sensory and motor pathways

Motor Sympathetic NS Two exceptions: - Adrenal gland: Motor neuron 2 has evolved into a “secretory” neuron which releases mostly epinephrine - The collateral ganglia: ganglia located between spinal cord and effectors -- ex: celiac ganglia innervating the digestive system

Sympathetic trunk: all the linked paravertebral ganglia will react as a unit to a stimulation of the sympathetic NS  heart rate increases, vasodilation of bronchi …. Collateral ganglia: they will not automatically react as a unit with the motor neurons from the sympathetic trunk

The adrenal medulla The gland is formed by the second motor neuron Secretes epinephrine Sympathetic effect sustained

Figure 11.5

Parasympathetic NS 2 motor neurons Motor neuron 1 in medulla oblongata or sacral spine Motor neuron 2 in a ganglion near the organ Acetylcholine (nicotinic receptor) in ganglionic synapse Acetylcholine (muscarinic receptor) in effector synapse Nerve pathways mixed with sensory and motor pathways, except for Vagus nerve (75% ANS)

Parasympathetic NS (motor pathway)

Neurotransmitters and receptors from the Sympathetic NS

Figure 11.7b Neurotransmitters and receptors from the parasympathetic NS

Receptors in the ANS Cholinergic receptors: Inhibitory or excitatory - Nicotinic: fast - Muscarinic: slow Adrenergic receptors: slow, excitatory or inhibitory - α 1 and 2 - β 1 and 2 (and 3)

Figure 11.8a Adrenergic receptors -α 1 and 2: affinity NE > E generally excitatory -β 1 and 3 affinity NE = E excitatory -β 2 affinity E > NE inhibitory

Figure 11.7

Effects of various drugs on the ANS Drugs acting on the cholinergic receptors: - agonist: simulate parasympathetic effect - antagonist: blocks parasympathetic effect (mimics sympathetic agonist) Drugs acting on the sympathetic NS - agonist: simulate sympathetic effect - antagonist: blocks sympathetic effect (mimics parasympathetic agonist)

Epinephrine and ephedrine are given in aerosol in people suffering from an asthma attack. - Knowing that these drugs are adrenergic agonists, which effect do you expect on the bronchi? - Which side effects are you likely to see? Refer to Table 11-2 from the book to answer these question

Propanolol is a beta-blocker. - What is this drug effect on the heart? - Which side effects are you likely to see? Refer to Table 11-2 from the book to answer these question

Atropine is a muscarinic cholinergic antagonist. - What is this drug effect on the pupils? - What is this drug effect on the heart? - Which side effects are you likely to see? - Will skeletal muscles be affected by this drug? Refer to Table 11-2 from the book to answer these question

Readings Chp. 11, p Will not be on the test: - Autonomic neuroeffector junctions, p 310