Quiz 3 Flashcards
What are the characteristics of somatic motor neurons?
-Controls only skeletal muscle
-Mostly voluntary
-A single motor neuron extends from CNS to muscle cell
What is the neuromuscular junction?
Synapse between axon terminal of somatic motor neuron & motor end plate of skeletal muscle fiber.
How does an action potential occur at the neuromuscular junction?
Neuronal action potential opens voltage-gated Ca2+ channels causing exocytosis of acetylcholine from axon terminal. The EPP opens voltage-gated Na+ channels that always produces a sarcolemmal action potential.
What kind of receptors does the sarcolemma have? Are they excitatory or inhibitory?
Nicotinic Acetylcholine receptors; excitatory/tonic control
What kind of receptor is the nAChR?
Ionotropic receptor/ receptor-channel: binding of ACh allows depolarization
What is an end-plate potential (EPP)?
A graded potential that is always excitatory
What is the life cycle of acetylcholine at the. neuromuscular junction?
-ACh made from choline and acetyl CoA
-In synaptic cleft, ACh broken down by acetylcholinesterase
-Choline transported back into axon terminal to make ACh
What are the characteristics of visceral motor (autonomic) neurons?
-Controls involuntary effectors
-Pre & Post ganglionic neurons extend from CNS to cell
-Two branches: sympathetic & parasympathetic
What is autonomic tone?
Normal balance between the SNS & PSNS branches
Most internal organs are under __________ control.
Antagonistic.
What is the SNS & PSNS inputs to the pupil of the eye?
SNS: dilate
PSNS: constrict
What is the SNS & PSNS inputs to heart rate?
SNS: increase (tachycardia)
PSNS: decrease (bradycardia)
What is the SNS & PSNS inputs to the lung bronchioles?
SNS: dilate
PSNS: constrict
What is the SNS & PSNS inputs to GI tract motility & secretion?
SNS: Decrease
PSNS: increase
What is the SNS & PSNS inputs to the exocrine pancreas?
SNS: Decrease secretion
PSNS: Increase secretion
What is the SNS & PSNS inputs to insulin secretion?
SNS: Decrease secretion
PSNS: Increase secretion
What are the systems that are only innervated by the sympathetic branch?
-Sweat glands
-Smooth muscle of most blood vessels
What NT is secreted by the pre-ganglionic neuron in both the SNS & PSNS?
Acetylcholine
What is the type of receptor found on post-ganglionic neurons in both the SNS & PSNS?
Nicotinic AChR
What NT does the post-ganglionic neuron of the PSNS secrete?
Acetylcholine
What NT does the post-ganglionic neuron of the SNS secrete?
Norepinephrine
What is the type of receptor found on target cells of the SNS?
Adrenergic receptors
What is the type of receptor found on target cells of the PSNS?
Muscarinic
What does the Alpha-1 subtype of adrenergic receptors do?
Vasoconstriction
What does the Alpha-2 subtype of adrenergic receptors do?
-Inhibit digestive system functions
What does the Beta-1 subtype of adrenergic receptors do?
Cardiac muscle (excitatory)
What does the Beta-2 subtype of adrenergic receptors do?
-Vasodilation
-Bronchodilation
What are varicosities?
The end of autonomic postganglionic neurons that store & release NT
What is the life cycle of Norepinephrine at a sympathetic neuroeffector junction?
-NE synthesized from Tyrosine & stored in vesicles
-Action potential opens voltage-gated Ca2+ channels and allows exocytosis of NE
-NE can be transported back into varicosity by being repackaged in vesicle or broken down by MAO
What are chromaffin cells?
Postganglionic neurons in the sympathoadrenal pathway that release epinephrine into the blood to activate “fight-or-flight” response.
