Chapter 15: The Autonomic Nervous System

Somatic NS
-sensory info comes from somatic senses (external)
-consciously perceived
-innervate skeletal muscle
-always excitatory
-responses are voluntary
-single neuron connects
-ACh
Autonomic NS
-sensory info comes from autonomic sensory receptors (interoceptors)
-generally not perceived
-innervate cardiac muscle, smooth muscle & glands
-not always excitatory
-responses cannot be consciously altered
-connection = two neurons.
1st neuron – in the CNS
2nd neuron – in a ganglion
ACh at the first synapse
at the 2nd synapse – ACh or other (ex – norepinephrine (NE))
Comparison of Somatic and Autonomic Nervous Systems
The ANS can be subdivided into:
-sympathetic division
-parasympathetic division
-Dual innervation
sympathetic division
readies the body for action, ” fight or flight”.

– also called the thoracolumbar division

parasympathetic division
body conserves energy “rest & digest”- also called the craniosacral division
Dual innervation
organs/effectors with both sympathetic & parasympathetic innervation
Autonomic tone
balance between sympathetic & parasympathetic actions
-Regulated by the hypothalamus (highest control center for ANS)
Structure of the Sympathetic Division
-Thoracolumbar division
(T1-L2)
-Sympathetic ganglia: sympathetic trunk ganglia/ chain ganglia/paravertebral
prevertebral (collateral) ganglia
-only sympathetic innervation : Sweat glands
Arrector pili muscles
Kidneys
Spleen
Most blood vessels
Adrenal medullae
Postganglionic neurons in the Sympathetic Division
Postganglionic neurons in the Sympathetic Division
Structure of the Parasympathetic Division
Structure of the Parasympathetic Division
-Craniosacral division
-Parasympathetic ganglia: terminal ganglia
-Presynaptic neuron usually synapses with 4-5 postsynaptic neurons
supply a single visceral effector
localized effect
Sympathetic VS Parasympathetic Division
Sympathetic VS Parasympathetic Division
Cholinergic and Adrenergic Neurons in the Autonomic Nervous System
Cholinergic neurons → (ACh).
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Cholinergic neurons include- preganglionic neurons
Sympathetic postganglionic neurons that innervate most sweat glands.
All parasympathetic postganglionic neurons.
-Cholinergic receptors
Nicotinic receptors – excitation
Muscarinic receptors -excitation or inhibition
-Ach – broken down by acetylcholinesterase

Adrenergic Neurons and Receptors
-Release norepinephrine (noradrenalin).
-Most sympathetic postganglionic neurons.
-2 types of receptors: alpha & beta
NE stimulates alpha receptors more strongly than beta
Ep stimulates alpha & beta receptors equally
-subtypes
Alpha 1 & beta 1 -excitation
Alpha 2 & Beta 2 – inhibition
-Removal of neurotransmitter: reuptake or enzymatic
(Catechol-O-methyltransferase ( COMT) or monoamine oxidase (MAO)
Agonist
activates a receptor
-It mimics the effect of a natural neurotransmitter or hormone
Antagonist
A substance that binds to and blocks a receptor.
Ex. Atropine
Ex. Propanolol (Inderal)
Sympathetic Responses
action – ” fight or flight ” response
exercise , emergency, excitement, embarrassment
-Pupils dilate
-Increased HR, force of contraction & BP
-Airways dilate
-Dilate blood vessels to skeletal muscle, heart, liver, adipose
-Constricts blood vessels to the GI tract and the kidneys
Parasympathetic Responses
Rest-and-digest
Conserve and restore
↑ digestive and urinary function.
↓ body functions that support physical activity.
decreased HR, diameter of airways & pupil diameter
-salivation
-lacrimation
-urination
-digestion
-defecation
Autonomic reflexes
ANS reflexes involve: a receptor, a sensory neuron, an integrating center within the CNS, motor neurons & effectors
-The hypothalamus
The Hypothalamus
major control & integrative center
-receives sensory input from senses and limbic system
-anatomically connected to both divisions of the ANS
posterior & lateral – sympathetic branch
anterior and medial – parasympathetic branch
Which of the following comparisons of the autonomic nervous system (ANS) and the somatic nervous system (SNS) is not true?
-the SNS carries information from the special senses
– the ANS has sensory receptors called interoceptors
– tissues of the ANS can function even if their nerve supply is damaged
-the SNS contains motor neurons which are excitatory and inhibitory
– angina pectoris is an example of input from the ANS
the SNS contains motor neurons which are excitatory and inhibitory
Which of the following does not describe the autonomic nervous system?
-the effectors are primarily skeletal muscles
-the sympathetic division generally stimulates an organ
-preganglionic axons release acetylcholine
-it is under involuntary control
-the parasympathetic division decreases heart rate
the effectors are primarily skeletal muscles
The sympathetic division of the ANS is called the thoracolumbar division because:
-the axons of the preganglionic neurons control thoracolumbar inflow
-sensory stimulation is received via all thoracic and lumber nerve roots
-it controls only organs and muscles in the thoracic and lumbar areas of the body
-its preganglionic neurons’ cell bodies are located in the gray matter of the thoracic and lumbar segments of the spinal cord
its preganglionic neurons’ cell bodies are located in the gray matter of the thoracic and lumbar segments of the spinal cord
Which statement is false in reference to the autonomic ganglia?
-the prevertebral ganglia lie close to the abdominal arteries
-the terminal ganglia lie near the bellies of skeletal muscles
-the sympathetic chain ganglia lie close to the vertebrae on each side
-the sympathetic preganglionic fibers of the sympathetic chain are very short
-the terminal ganglia are parasympathetic ganglia
the terminal ganglia lie near the bellies of skeletal muscles
The primary reason that the sympathetic division of the ANS produces immediate responses within the body is based on the concept of divergence.
True/False
True
Cholinergic neurons are named after the neurotransmitters that they release, the catecholamines.
True/False
False
Which of the following neurotransmitters does not bind to adrenergic receptors?
-noradrenaline
-acetylcholine
-epinephrine
-norepinephrine
-adrenaline
acetylcholine
An agonist is:
-a substance that binds with a neurotransmitter to enhance its effects
-a substance that blocks a hormone from applying its effect
-a substance that activates a receptor producing the same effect as a neurotransmitter
-a substance that prevents a receptor from receiving a hormone
a substance that activates a receptor producing the same effect as a neurotransmitter
The definition of autonomic tone is:
-the communication between the autonomic nervous system and the somatic nervous system
-the balance between sympathetic and parasympathetic activity
-the constant slight contraction seen in skeletal muscles
-the canceling out effect of adrenergic and cholinergic responses to a stimulus
the balance between sympathetic and parasympathetic activity
The Sympathetic division is associated with excitement or embarrassment.
True/False
True
Which of the following effects does not occur during the fight-or-flight response?
-the pupils constrict
-the airways increase in diameter
-blood vessels to skeletal muscles dilate
-heart rate speeds up
-blood pressure increases
the pupils constrict
During periods of rest and recovery, the sympathetic activity to glands and smooth muscles predominates over parasympathetic activity.
True/False
False
Which of the following sympathetic responses is mismatched with its body part?
-iris of eye – dilation of pupil
-liver – increased glycogen synthesis
-stomach – decreased motility
-hair follicles – contraction of arrector pili muscles
-adipose tissue – increased lipolysis
liver – increased glycogen synthesis
Which would be an example of a condition in the body not controlled by autonomic reflexes?
-breathing rate and depth
-rate of urine formation
-tracking a bird flying by
-digestion of your evening meal
-blood pressure change during exercise
tracking a bird flying by
The primary difference between an autonomic reflex arc and a somatic reflex arc is that the former has two motor neurons connecting the CNS to an effector.
True/False
True
The autonomic nervous system operates by reflex arcs that include sensory neurons, integrating centers that are mainly in the hypothalamus and brain stem, and motor neurons.
True/False
True
Most people have conscious control over their autonomic nervous system.
True/False
False
The parasympathetic division would increase the heart rate of a person startled by oncoming traffic.
True/False
False
The parasympathetic postganglionic axon extends from the terminal ganglion to the effector.
True/False
True
Some physiological responses require activation of both the sympathetic and parasympathetic divisions of the autonomic nervous system; the hypothalamus regulates this balance of sympathetic and parasympathetic activity.
True/False
True
The parasympathetic NS is also called the craniosacral division because it includes four cranial nerves and spinal nerves from S2-S4.
True/False
True
The sympathetic division will
-promote digestion.
-promote urination.
-increase heart rate.
-decrease pupil size.
-decrease the diameter of the airways.
increase heart rate.
Acetylcholine is released
1. at the neuromuscular junctions
2. within sympathetic ganglia
3. within parasympathetic ganglia
-1 only
-2 only
-3 only
-2 and 3 are correct
-1, 2 and 3 are correct
1, 2 and 3 are correct
Acetylcholine binds to
1. nicotinic receptors
2. muscarinic receptors
3. alpha receptors
-1 only
-2 only
-3 only
-1 and 2 are correct
-1, 2 and 3 are correct
1 and 2 are correct
Release of acetylcholine by postganglionic cells will
-increase heart rate
-dilate bronchioles
-increase digestion
-increase heart rate and dilate bronchioles
-dilate bronchioles and increase digestion
increase digestion
The sympathetic division is referred to as the thoracolumbar region because it has postganglionic neuron cell bodies located in the lateral horns of gray matter in the 12 thoracic segments and the first two lumbar segments of the spinal cord.
True/False
False
What part of the nervous system is the main control and integrative center of the autonomic nervous system?
-cerebrum
-medulla oblongata
-thalamus
-hypothalamus
hypothalamus
The fight or flight response involves all of the following except:
-Glycogenolysis
-Increase in digestive tract activity to mobilize glucose
-Activation of the sympathetic division
-Release of epinephrine
-Increase in heart rate
Increase in digestive tract activity to mobilize glucose
The parasympathetic division of the autonomic nervous system is called an energy conservation/restoration system because it supports body functions that conserve and restore energy during periods of rest and recovery.
True/False
True
The cell bodies of sympathetic preganglionic neurons are located in the
-terminal ganglia
-visceral organs
-spinal cord
-sympathetic trunk ganglia
spinal cord
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