Autonomic Nervous System
A. Review
1. Involuntary portion of the nervous system
2. 2 branches
A) Sympathetic branch – primarily excites its effectors; responsible for “fight or
flight” response
B) Parasympathetic branch – primarily inhibits its effectors; responsible for energy
restoration/conservation
B. Components of the ANS
1. Visceral receptors
2. Visceral sensory neurons
3. Autonomic control centers in CNS
4. Preganglionic (motor) neurons (Sympathetic &Parasympathetic)
5. Autonomic ganglia (S&P)
6. Postganglionic (motor) neurons (S&P)
7. Autonomic effectors (S&P; often a single effector is shared by both branches)
Note: We will focus on the functions of #4-7 below
C. Neurotransmitters
1. Two neurotransmitters are released by the motor neurons of the ANS (components #4
& 6)
A) Acetylcholine (ACh) – released from cholinergic neurons
1) All sympathetic and parasympathetic preganglionic neurons release ACh
2) All parasympathetic postganglionic neurons release ACh
3) A few sympathetic postganglionic neurons (ex. sweat glands) release ACh
B) Norepinephrine – released from adrenergic neurons
1) Most sympathetic postganglionic neurons release norepinephrine
D. Receptors are found on the dendrites of the postganglionic neurons in the autonomic
ganglia, and on the autonomic effectors. (Refer to the summary table found on the lecture
materials page)
1. Cholinergic receptors – bind with ACh
A) 2 types
1) Nicotinic
a) 17 different types, divided into 2 subtypes (neuronal & muscle)
b) Found on the dendrites of all parasympathetic and sympathetic postganglionic
neurons; also found on the adrenal glands (excitatory)
2) Muscarinic
a) 5 subtypes (M1-M5)
b) Found throughout the body on all parasympathetic effectors
i) Mostly excitatory but some are inhibitory dependent on location
c) Found on a few sympathetic effectors – sweat glands (excitatory)
2. Adrenergic receptors – bind with norepinephrine
A) 2 types
1) Alphaadrenergic receptors – 2 subtypes
A. Review
1. Involuntary portion of the nervous system
2. 2 branches
A) Sympathetic branch – primarily excites its effectors; responsible for “fight or
flight” response
B) Parasympathetic branch – primarily inhibits its effectors; responsible for energy
restoration/conservation
B. Components of the ANS
1. Visceral receptors
2. Visceral sensory neurons
3. Autonomic control centers in CNS
4. Preganglionic (motor) neurons (Sympathetic &Parasympathetic)
5. Autonomic ganglia (S&P)
6. Postganglionic (motor) neurons (S&P)
7. Autonomic effectors (S&P; often a single effector is shared by both branches)
Note: We will focus on the functions of #4-7 below
C. Neurotransmitters
1. Two neurotransmitters are released by the motor neurons of the ANS (components #4
& 6)
A) Acetylcholine (ACh) – released from cholinergic neurons
1) All sympathetic and parasympathetic preganglionic neurons release ACh
2) All parasympathetic postganglionic neurons release ACh
3) A few sympathetic postganglionic neurons (ex. sweat glands) release ACh
B) Norepinephrine – released from adrenergic neurons
1) Most sympathetic postganglionic neurons release norepinephrine
D. Receptors are found on the dendrites of the postganglionic neurons in the autonomic
ganglia, and on the autonomic effectors. (Refer to the summary table found on the lecture
materials page)
1. Cholinergic receptors – bind with ACh
A) 2 types
1) Nicotinic
a) 17 different types, divided into 2 subtypes (neuronal & muscle)
b) Found on the dendrites of all parasympathetic and sympathetic postganglionic
neurons; also found on the adrenal glands (excitatory)
2) Muscarinic
a) 5 subtypes (M1-M5)
b) Found throughout the body on all parasympathetic effectors
i) Mostly excitatory but some are inhibitory dependent on location
c) Found on a few sympathetic effectors – sweat glands (excitatory)
2. Adrenergic receptors – bind with norepinephrine
A) 2 types
1) Alphaadrenergic receptors – 2 subtypes
