-
The main nerves of
the parasympathetic
NS are the __
tenth cranial nerves: the vagus nerves
-
the vagus nerves
- – Originate in the medulla oblongata
- -the tenth cranial nerve
- -Called the wondering nerve because it is composed of mostly sensory neurons
- -communicates the state of the viscera to the brain.
- -attached to most organs (not kidney or spleen)
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Where do Parasympathetic neurons extend out from the spine?
At the brain and down at the lower tip
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Functions of the parasympathetic nervous system
- • Returns the body functions to normal after they have been altered by sympathetic stimulation
- – Slow down of the heartbeat
- – Lower blood pressure
- – Constrict the pupils
- – Increase blood flow to the skin and viscera
- – Cause peristalsis of the GI tract
-
SLUDDSA
- • A useful acronym to summarize the
- functions of the parasympathetic nervous system:
- – Salivation, Lacrimation(crying), Urination,
- Digestion and Defecation and Sexual arousal
-
Acetylcholine (ACh)
-chemical makeup
-Which nervous system does it act in?
- • A polyatomic cation, ester of acetic acid and choline;
- • One of most widespread neurotransmitters;
- – Acts as a neurotransmitter in both the peripheral nervous
- system (PNS) and central nervous system (CNS);
-
Acetylcholine (ACh) is the principal neurotransmitter in all ___ ganglia
autonomic
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Acetylcholine
-Uses in the motor division of the somatic nervous system
-neuromuscular junctions
-cardiac tissue
- • The only neurotransmitter in the motor division of the
- somatic nervous system;
- – At neuromuscular junctions in skeletal muscle has an
- excitatory effect;
- – In cardiac tissue has inhibitory effects - lowers heart rate.
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ACh has two types of effects:
-what makes the distinction?
- nicotinic
- muscarinic
- -Response of postsynaptic cell depends on receptor type
-
nicotinic
On the postsynaptic side of the neuromuscular junction the skeletal voluntary muscles, which it is not considered to be part of PNS.
-
muscarinic
• On the postganglionic, parasympathetic effect on the exocrine glands and on smooth and cardiac muscles
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Nicotinic ionotropic receptors
(1)type:
(2)Site of receptor:
(3)respond to Acetylcholine release from:
(1)ligand-gated ion channels
- (2)-All autonomic ganglia
- -Motor end plates of skeletal muscle fibers
- -Some CNS cell bodies and dendrites
- (3)-Sympathetic and Parasympathetic preganglionic fibers
- -Motor neurons
- -Some CNS presynaptic terminals
-
Muscarinic metabotropic receptors
(1)type:
(2)Site of receptor:
(3)respond to Acetylcholine release from:
(1)G-protein coupled receptors (GPCRs)
- (2)Effector cells(cardiac muscle, smooth muscle, glands)
- - some CNS cell bodies and dendrites
- (3)-Parasympathetic postganglionic fibers
- -some CNS presynaptic terminals
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Two main types of Nicotinic receptors
-selectively blocked by what?
muscle type: selectively blocked by curare
neuronal type:selectively blocked by hexamethonium
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How do ionotropic and metabotropic receptors compare?
(similarities/differences)
- ionotropic has a channel that allows ions such as Na+, K+, or Cl- to flow.
- -activated quickly but only open for miliseconds, used for quick response
- metabotropic is a seven transmembrane receptor that triggers a series of intracellular events that results in:
- -Opening of Na+, K+ and Ca++ channels;
- -Activation of intracellular signals
- -takes longer to open channels, not involved in quick responses
- -activated from seconds to minutes, longer lastic effect than ionotropic
-Both encourage flow of Na+ and K+
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