Chapter 9 Flashcards
What does the autonomic nervous system do?
regulates organs and organ systems and their smooth muscles and glands
What is intrinsic muscle tone?
no nerve stimulation in smooth muscle
- resting
What happens when ANS input is cut on smooth muscle?
denervation hypersensitivity
- exaggerated reflexes
- spasms
How does ANS affect smooth muscles?
smooth muscles are spontaneously active and contract rhythmically WITHOUT ANS input
- ANS input increases or decreases intrinsic activity
What neurotransmitter is at the effector of somatic nervous system? What’s the effector organ? What’s the effect?
acetylcholine
- skeletal muscle
- stimulatory
What is the 3-word phrase for sympathetic pathway?
fight or flight
What are the 2 pathways for sympathetic pathway?
1) lightly myelinated preganglionic axons -> ACh on ganglion -> unmyelinated postganglionic axon
2) lightly myelinated preganglionic axons -> ACh on adrenal medulla -> Epinephrine/Norepinephrine onto blood vessel
What neurotransmitter is at effector of sympathetic pathway? What’s the effect?
norepinephrine
- both stimulatory or inhibitory depending on neurotransmitter and receptors on effector organs
What is the 3-word phrase for parasympathetic nervous system?
rest or digest
What is the pathway for parasympathetic nervous system?
lightly myelinated preganglionic axon -> ACh onto ganglion -> unmyelinated postganglionic axon
What is the neurotransmitter at effector for parasympathetic nervous system? What’s the effect?
ACh
- both stimulatory or inhibitory
What are some features of somatic motor systems?
- skeletal muscle
- no ganglia
- one motor neuron
- excitatory
- fast-conducting thick myelinated
- flaccid paralysis and atrophy
What are some features of autonomic motor systems?
- smooth and cardiac muscles and glands
- has ganglia
- 2 motor neurons
- BOTH excitatory and inhibitory
- slow-conducting (thin, lightly myelinated TO unmyelinated
- tone and function persist
- denervation hypersensitivity
How are the 2 neurons in the ANS connected?
1st neuron = preganglionic neuron (cell body in brain/spinal cord)
2nd neuron = postganglionic neuron synapse
Where do postganglionic axons extend from?
autonomic ganglion to target tissue
What are the 2 divisions of the ANS?
sympathetic and parasympathetic
- antagonistic effects
What is another name for the sympathetic division? Why is it called that?
thoracolumbar division
- preganglionics exit spinal cord from T1 to L2
Where do the sympathetic division cells synapse?
on postganglionic in the paravertebral ganglia
- form chain of interconnected ganglia paralleling spinal cord
What is mass activation?
all sympathetic division acting as a unit
What is divergence?
preganglionics branch to synapse with a number of postganglionic neurons
- small amount to large amount
What is convergence?
postganglionics receive synaptic input from a large number of preganglionics
What happens when there’s a collateral ganglion?
prevents postganglionics from synapsing in paravertebral ganglion
What is the modified collateral ganglion? Why?
adrenal medulla
- secretory cells look like modified postganglionics
- releases 85% epinephrine and 15% norepinephrine into blood in response to preganglionic stimulation
When is the adrenal stimulated?
mass activation
How is epinephrine made?
by methylating norepinephrine
What is the craniosacral division? Why?
parasympathetic division
- long preganglionics originate in midbrain, medulla, pons, and S2-S4
Where does parasympathetic division synapse? What is special about the postganglions?
postganglionics in terminal ganglia located next to or within a target organ
- they have short axons that innervate target
What nerve has the most parasympathetic fibers?
vagus nerve
What does the vagus nerve innervate?
heart
lungs
esophagus
stomach
pancreas
liver
small intestine
upper half of large intestine
What does the preganglionic fibers from S2-S4 innervate?
lower half of large intestines
rectum
urinary
reproductive systems
Which preganglionics release ACh?
both sympathetic and parasympathetic
What do the postganglionics release?
parasympathetic: ACh (cholinergic synapses)
sympathetic: release norepinephrine (adrenergic synapses)
- small amount releases ACh
What are varicosities?
unusual synapses from postganglionics
What is synapse en passant?
varicosities release neurotransmitters along a length of axon
What causes both excitation and inhibition reactions?
adrenergic stimulation
(depends on tissue)
What are the different subtypes of a receptor?
alpha- and beta-adrenergic receptors
What do the subtypes use as second messengers?
beta: cAMP
alpha: Ca++
How are drugs developed?
they affect ANS receptors
What are the types of drugs that affect neurotransmitters?
agonists: promote action of neurotransmitter
antagonists: inhibit actions of a neurotransmitter
What is the nicotinic receptor stimulated by? What is it blocked by?
stimulated by nicotine
blocked by curare
What is the muscarinic receptor stimulated by? What is it blocked by?
stimulated by muscarine (poisonous mushrooms)
blocked by atropine
