Physiology 31 Lecture
Chapter 11 – PNS: Somatic & Autonomic Divisions
I. Overview
A. Two divisions of the _____
1. ____________ (voluntary) NS consists of a. Motor nerves from the CNS control skeletal ________ b. Sensory nerves from ______ceptors of the skin, muscles, bones, and joints send information to the CNS
2. _________________ (involuntary) NS consists of a. Motor neurons from the CNS control _________, cardiac and smooth ___________ b. Sensory input from ______ceptors of the internal viscera send information to the
CNS
3. The two subdivisions of the ANS are the: ______________ & Parasympathetic
II. The Somatic Motor Division
A. _____________ motor pathway features
1. _____ type of somatic motor neuron extends from the CNS to
2. ___________ muscle
3. Somatic motor neurons are always _____________ , and cause muscle contraction
B. A somatic motor pathway consists of ____ type of motor neuron
1. Somatic motor neuron cell ________ originate in the gray matter of the brain and spinal cord
2. Their _________ extend outward from cranial and spinal nerves to skeletal muscles a. Axons branch near the muscle to form a cluster of enlarged axon terminals
( ___________ ) that synapse with muscle cells b. Axon _________ allow one neuron to control many muscle cells
C. The synapse between the somatic neuron and muscle cell is called the neuron____________ junction. It consists of
1. ____synaptic axon _________ that contains synaptic vesicles with _____ neurotransmitter
2. Synaptic ________
– a minute, fluid filled gap that contains a. ___________ fibers b. Acetycholinesterase (______) that degrades ACh
3. _____synaptic motor end _________ of a skeletal muscle fiber a. _________ ACh receptors are in the motor end plate membrane
D. _____________ at the neuromuscular junction
1. An action potential stimulates release of _____ into the synaptic cleft
2. ACh binds to nicotinic ACh receptors in the motor end ________
3. __________ ACh receptors, which are ligand-gated ion channels, open to allow _____ into the muscle cell
4. Na+ influx ____________ the muscle membrane, which results in muscle contraction
E. ____________ is an agonist to ACh
1. Nicotine binds to nicotinic _____ receptors and opens Na+ channels, causing depolarization

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2. N icotine binding to ACh receptors in _______________ neurons causes vasoconstriction, and leads to high blood ___________
III. The Autonomic Nervous System
A. The autonomic nervous system (_____) is the general visceral _________ division of the
PNS, and contains two subdivisions
1. _____________ N.S. – involved in “fight or flight” responses; this branch prepares the body for ____________ activity
2. ______sympathetic N.S. – involved in “rest & ___________” activities; this division is in control the majority of the time
B . Involuntary __________ (smooth & cardiac muscle and glands) are regulated by autonomic motor impulses via the ANS
C. Autonomic ___________ are important for homeostasis
1. The _____________ NS, endocrine system, and behavior work together to maintain homeostasis
2. ___________ input from somatosensory and visceral receptors goes to control centers in the hypothalamus, pons and medulla a. These centers __________ and regulate functions such as blood pressure, temperature, and water balance
3. _________ output from the ______thalamus and brain stem creates autonomic, endocrine, and behavioral responses, such as drinking, food seeking, etc.
4. _________ reflexes can occur without input from the brain (e.g., urination, defecation, etc.) a. People with spinal cord _________ that disrupt communication between the brain and spinal cord retain some spinal _________, but lose the ability to sense or control them
(e.g., incontinence)
D. The sympathetic and parasympathetic branches demonstrate Cannon’s 4 properties of
______________
1. Maintenance of the __________ environment
2. Up-down ______________ of target tissues
3. _______________ control – one branch excites some tissues, whereas the other inhibits the tissues
4. Variable tissue responses due to different types of __________
E. The autonomic motor pathway involves ___ types of motor neurons (recall that the somatic motor pathway had 1 type of motor neuron):
1.
____ganglionic (presynaptic) neurons - have their cell bodies in the gray matter of the brain or SC, and release ____ neurotransmitter; their axon terminals synapse with
2.
______ganglionic (postsynaptic) neurons that extend from an autonomic ganglia and synapse with an __________ organ
3.
Autonomic _____________ are located in the head, neck, & abdomen, and on each side of the spinal cord

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IV. Sympathetic & Parasympathetic divisions of the ANS
A. Sympathetic
“fight or ___________” responses include
1. __________ pupils
2. Stimulates _________ glands
3. Vaso___________ blood vessels to glands and internal organs
4. ______ bronchioles and blood vessels to heart & skeletal muscles
5. Stimulates adrenal medulla to secrete _______________ (adrenalin) & norepinephrine into the blood stream
6. Increases heart ______ and force of contraction, as well as blood ___________
7. Stimulates break down and release of __________ from liver and lipids from fat cells to supply glucose to blood stream
B. Parasympathetic “rest and ___________” responses
1. Pupils are ___________
2. Glands are stimulated to __________
3. Heart rate is __________ and steadied
4. Blood vessels to heart, and bronchioles are vaso_____________
5. Smooth muscle of bladder and digestive organs are contracted, promoting
__________________ .
C. S ympathetic and parasympathetic branches exit the spinal cord in different regions, have different ganglia, and secrete different neuron____________
1. Sympathetic (______________) division a. Preganglionic neurons are _______, exiting the spinal cord lateral horns from T1 to
L2 and synapse with postganglionic neurons in the b. Sympathetic chain ___________, which are located on both sides of the vertebral column and along the descending aorta
1) Some preganglionic neurons synapse with ____________ postganglionic neurons, leading to ______ ____________ of several organ systems at once c. Postganglionic neurons are _______, extending out to target organs, and are
_____________ , most secrete norepinephrine neurotransmitter
2. Parasympathetic (_____________) division a. Preganglionic neurons are _________; they exit from the midbrain, brain stem
(including cranial nerves III, VII, IX, & ___) and sacrum, and synapse with b. Postganglionic neurons in terminal __________ near or on target organs; these neurons are short; most are _____________ – they release ACh neurotransmitter c. Each preganglionic neuron synapses with only about _____ postganglionic neurons; thus parasympathetic effects are more ___________; no mass activation of organs occurs
D. The ANS uses a variety of neuron____________ and modulators
1. All autonomic preganglionic neurons secrete _____ onto cholinergic ____________ receptors of postganglionic neurons
2. Most postganglionic __________ neurons release norepinephrine onto
_______________ receptors on effectors

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3. Most postganglionic ______sympathetic neurons secrete _____ onto cholinergic
____________ receptors on effectors
4. A few autonomic neurons are not adrenergic or cholinergic; they secrete other neuron_______________, such as substance P, somatostatin, adenosine, nitric oxide, and
ATP
E. Autonomic pathways control glands, smooth and cardiac _______
1. The synapse between a postganglionic neuron and its target cell is called the
_______________ junction a. Autonomic neuron axon terminals form bead-like strands called ________________ , which lie across the target tissue b. Neurotransmitter released from the varicosities diffuses to ____________ on the target tissue to produce a response c. The response ceases as the neurotransmitter diffuses _______ from the synapse or is broken down by __________
2. The release of neurotransmitters may be ___________ by several sources a. Sympathetic varicosities have receptors for ____________ and paracrines, such as histamine; these modulators may _________ or facilitate neurotransmitter release b. Some preganglionic neurons secrete neuron___________ with ACh; the peptides
_______ synaptic potentials and modify postganglion neuron activity
F. The adrenal medulla secretes _____________
1. The adrenal medulla is actually a modified sympathetic ________
2. I t secretes epinephrine (_____________) into the bloodstream in response to sympathetic stimulation
G. Most sympathetic pathways secrete norepinephrine (____) onto adrenergic receptors
1. NE can have different effects in different tissues due to alpha and beta ______________ receptors a. __________ (α) a drenergic receptors are the most common sympathetic receptor; they respond _________ to NE and weakly to epinephrine;
α
receptors are found in many
_________ b. ____ (β) adrenergic receptors have two main subtypes β
1
and β
2
1) ___ receptors respond ___________ to NE and epinephrine; ___________ muscle and kidneys have β
1
receptors
2) ____ receptors are not associated with sympathetic neurons, and respond more strongly to _____________; allows dilation in blood vessels and in bronchioles
2. All adrenergic receptors are linked to ___ proteins, but the different subtypes use different second ____________
H. Parasympathetic pathways secrete _____ onto muscarinic receptors
1. ____________ cholinergic receptors are also G protein-linked
2. Some muscarinic receptors activate 2 nd ____________ systems, whereas others affect gated K+ channels
I. Autonomic agonists and antagonists are important tools in research and ___________
1. _____________ are molecules that bind to a receptor and ______ the effect of the receptor’s normal ligand. Examples: a. Nicotine binds to nicotinic receptors and mimics _____ b. Muscarine (a mushroom chemical) binds to ___________ receptors and mimics ACh

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2. _______________ a re molecules that bind to a receptor and _______ the receptor’s normal neurotransmitter action. Examples: a. ____________, a poison, binds to ___________ receptors and blocks _____; paralysis results because the nerve impulse cannot be transmitted to postganglionic neurons or muscle tissue b. _________ (bella donna) is a poison that binds to ___________ receptors and blocks parasympathetic responses
3. Many __________ used to treat depression act either on a. M embrane ___________ for neurotransmitters (e.g., selective serotonin reuptake inhibitors allow serotonin to remain in synapses longer) or b. ________________ of the neurotransmitters (e.g., monoamine oxidaze inhibitors )
4. Discovery of α and β ______________ receptors led to the development of drugs that block only one of the receptor types a. ______ blockers prevent high blood pressure by blocking β
1
receptors on the heart and kidneys
J. Primary ____________ of the ANS are relatively uncommon
1. Damage to the _______thalamus can cause abnormalities in water balance or temperature regulation
2. _______________ dysfunction may result from diseases such as cancer and diabetes mellitus a. Diabetic autonomic ____________ is a gradual desensitization of neurons due to high blood __________ levels b. It results in _________________, gastrointestinal, urinary, and reproductive problems, which can cause c. Blindness, limb ______________, heart attacks, etc.