Autonomic Nervous System
How is neurotransmitter release at the neuroeffector junction? Why are the autonomic neurons arranged this way?
-Variscosity: a series of swollen areas at the distal ends of autonomic postganglionic axons forming a synapse en passant, which travels down the tissues signaling at a faster rate. There isn't a cluster of neurotransmitter receptors in specific sites under the varicosities. The neurons are arranged with varicosities so that the tissues can be signaled fast and fully throughout the tissue.
Can you describe release and removal of norepinephrine at the neuroeffector junction?
1)Action potential arrives at the variscosity 2) Depolarization opens voltage-gated Ca2+ channels. 3)Ca2+ entry triggers exocytosis of synaptic vesicles 4) Norepinephrine binds to adrenergic receptor on target 5)Receptor activation ceases when Norepinephrine diffuses away from the synapse 6)Norepinephrine is removed from the synapse 7)Norepinephrine can be taken back into synaptic vesicle for re-release 8)Norepinephrine is metabolized by monoamine oxidase(MAO)
What are the two regions of the adrenal gland? Which is involved in sympathetic NS? What makes this arrangement different from typical pathway in sympathetic NS and what is released from here and by what cells (name)?
Adrenal Cortex and Adrenal Medulla. The adrenal medulla is involved in the sympathetic nervous system The postganglionic neurons are chromatin cells which are modified postganglionic sympathetic neurons They secrete epinephrine into the blood.
What mechanism does the adrenergic receptor signal through? Why can you have differing effects on tissue with the same neurotransmitter?
Adrenergic receptors signal through G protein coupled receptors. The effects differ due to their being alpha and beta adrenergic receptors
What are the divisions of the efferent division of the nervous system and what are their effector tissue?
Autonomic neurons and Somatic motor neurons Somatic: skeletal muscles ANS:Cardiac muscle, smooth muscle, and glands
Which regions of the brain are involved in the control of the autonomic system?
Hypothalamus, Pons, and Medulla
What are the effects of acetycholine released from the parasympathetic postganglionic neuron on the target tissue? Why can there be differ effects from the same neurotransmitter?
Inhibition: -Ach binds to G protein couple receptor -G protein is activated thus opening a potassium ion channel causing hyper polarization. Excitation: -Ach binds to G protein couple receptor -G protein is activated which then goes to activate a sodium or calcium ion channel causing depolarization There can be different effects because of different muscarinic receptors.
What does metabotropic and ionotropic receptors mean?
Metabotropic receptors are ion channels that open or close in response to the binding of a neurotransmitter (Ligand gated ion channel) Ionotropic receptors are G protein coupled receptors
What is the synapse at skeletalmuscle termed? Which neurotransmitter is released here and what receptor is found on the muscle cell membreane? What is the effect on the muscle's membrane potential?
Neuromusclar Junction. Acetylcholine is released here and it binds to the nicotinic cholinergic receptors. The muscles membrane potential becomes depolarized.
What are the differences between nicotinic and muscarinic receptors?
Nicotinic receptors are ligand gated ion channels whereas muscarinic receptors are G protein couple receptors.
What effects would drug that either decrease (antagonist) or increase (agonist) either acetylcholine or norepinephrine have on SA node cells (heart rate), smooth muscle o the lugs digestive tract, or bronchioles of the lungs.
SA node cell(Heart rate): -Increase causes heart rate to increase -lack of causes the heart rate to decrease Smooth muscle on the lungs: -Increase of causes the muscle to relax -lack of cause the smooth muscle to constrict Digestive tract: -Increase of causes the decrease of activity in the tract -lack of causes the digestive tract to increase in activity Bronchioles of the lungs: -Increase of causes the bronchioles to dilate -lack of causes the bronchioles to constrict
Where are somatic motor division and autonomic neuron cell bodies located in the spinal cord.
Somatic motor division cells bodies are located in the ventral horn Autonomic neuron cell bodies are found in the lateral horn
What are the two divisions of autonomic nervous system? What do these divisions control?
Sympathetic and Parasympathetic. Cardiac muscle, smooth muscle, and glands
How are the two divisions of the autonomic nervous system arranged? Where do they originate from? What are the lengths of the different neurons? Where do the pre and post ganglionic neurons synapse? What neurotransmitters are used pre and postganglionic synapse and at synapse between postganglionic neuron and target tissue? What receptors would be found on the dendrites of the postganglionic neurons and what receptors would be found on the target tissue?
Sympathetic: -short postganglionic neuron meets with a long post ganglionic neuron in a autonomic ganglion -originates from thoracic and lumbar regions of spinal cord -synapse at pre and post ganglionic neurons uses acetylcholine -synapse between the preganglionic neuron and target tissue uses norepinephrine and rarely epinephrine. -Nicotinic receptors on the postsynaptic neurons -Adrenergic receptors at the post ganglionic and target tissue synapse Parasympathetic: -Long preganglionic neuron meets with a short postganglionc neuron in a autonomic ganglion -Originate in the brain stem and the sacral region -synapse at pre and post ganglionic neurons uses acetylcholine -synapse between post ganglionic neuron and target tissue uses acetylcholine -nicotinic receptors on the postsynaptic neurons -Muscarinic receptors at the postsynaptic ganglionic and target tissue synapse.
How does the autonomic differ from the somatic nervous system?
The autonomic -signals cardiac muscle, smooth muscle, and glands and can be excitatory or inhibitory. -Uses two neurons from CNS to effector. -Has ganglia -no specialization on postsynaptic membrane -slow conduction preganglionic fibers lightly myelinated but thin and postganglionic fibers unmyelinated and very thin The somatic -signals skeletal muscle - is only excitatory. -Uses one neuron from CNS to effector -no ganglia -Specialized motor end plate -fast conducting and which and myelinated
What is mass activation of the sympathetic? What property allows this to occur?
The preganglionic neuron can diverge at chain and innervate multiple postganglionic neurons.
What is the main parasympathetic tract? What does it innervate?
The vagus nerve. It innervates the head, neck, and internal organs.
Which tissue are under tonic control? Which division of the autonomic exhibits tonic control?
Tonic Control: -Arterioles and veins -Adrenal medulla -Kidney -Adipose tissue -Sweat glands -Lymphoid tissue Sympathetic nervous system
How do tonic and antagonistic control differ? How does tonic control operate to change response at target tissue?
Tonic-only controlled by sympathetic branch --Uses rate of frequency of action potentials to alter the response at the target tissue Antagonistic-Controlled by the excitatory and the other branch is inhibitory. --Uses both signaling from the sympathetic and parasympathetic nervous system