Nervous System Physiology Part 4 Flashcards
What determines the membrane potential of the postsynaptic neuron at any given moment?
The membrane potential of the postsynaptic neuron at any moment is the result of all the synaptic activity affecting it at that moment
How do postsynaptic potentials influence the activity of a postsynaptic neuron?
The postsynaptic potentials summate to influence the determine activity of a postsynaptic neuron.
What happens to the postsynaptic neuron if the stimulatory effects of EPSPs dominate the membrane potential enough to reach threshold?
The neuron will fire (generate an action potential).
What happens to the postsynaptic neuron if summation yields only subthreshold depolarization or hyperpolarization?
The neuron fails to generate an action potential.
What is the role of neurotransmitters in the nervous system?
Neurotransmitters, along with electrical signals, are the “language” of the nervous system – the means by which each neuron communicates with others to process and send messages to the rest of the body.
What type of postsynaptic potentials do neurotransmitters elicit?
Neurotransmitters elicit EPSPs and IPSPs.
In general, what do the receptors for neurotransmitters influence on the postsynaptic cell?
In general, the receptors for neurotransmitters influence ion channels that directly affect excitation or inhibition of the postsynaptic cell.
Approximately how many neurotransmitters or neurotransmitter candidates have been identified?
More than 50 neurotransmitters or neurotransmitter candidates have been identified.
How many types of neurotransmitters do most neurons produce and release?
Most neurons make two or more and may release any one or all of them.
Neurotransmitters fall into several chemical classes based on what?
Neurotransmitters fall into several chemical classes based on molecular structure.
How do neuromodulators typically modify synaptic transmission?
Neuromodulators often modify the postsynaptic cell’s response to specific neurotransmitters, amplifying or dampening the effectiveness of ongoing synaptic activity. Alternatively, they may change the presynaptic cell’s synthesis, release, reuptake, or metabolism of a transmitter.
Is the distinction between neurotransmitters and neuromodulators always clear?
The distinctions between neuromodulators and neurotransmitters are not always clear.
Where is Acetylcholine found?
Acetylcholine (ACh) is a major neurotransmitter in the PNS at the neuromuscular junction and in the brain.
What are neurons that release Acetylcholine (ACh) called?
Cholinergic neurons.
What are some of the things ACh has an effect on in the CNS?
In the CNS, ACh has a variety of effects on plasticity, arousal, and reward. It also plays an important role in the enhancement of alertness when we wake up, in sustaining attention, and in learning and memory.
What are the main functions of ACh in the PNS?
In the PNS, acetylcholine activates muscles and is a major neurotransmitter in the autonomic nervous system.
What happens to the concentration of ACh at the postsynaptic membrane after it is released and activates receptors? What enzyme is responsible for this?
After ACh is released and activates receptors, its concentration at the postsynaptic membrane decreases, thereby stopping receptor activation. This is due to the action of the enzyme acetylcholinesterase.
Briefly describe the process of acetylcholine synthesis and breakdown as shown in the diagram.
- Synthesis: Acetylcholine (ACh) is made from choline and acetyl CoA in the axon terminal.
- Release: ACh is released into the synaptic cleft.
- Breakdown: Acetylcholinesterase (AChE) in the synaptic cleft rapidly degrades ACh into choline and acetic acid.
- Reuptake: Choline is transported back into the axon terminal and is used to make more ACh.
How many general types of ACh receptors are there? What are they called?
There are two general types of ACh receptors:
* Nicotinic receptors
* Muscarinic receptors
Besides acetylcholine, what else do nicotinic receptors respond to?
Nicotinic receptors respond not only to acetylcholine but also to the drug nicotine.
Besides acetylcholine, what else are muscarinic receptors stimulated by?
Muscarinic receptors are stimulated not only by acetylcholine but also by the mushroom poison muscarine.
What is a Nicotinic acetylcholine receptor?
- Ligand-gated channel.
- Permeable to both sodium (\text{Na}^+) and potassium (\text{K}^+) ions.
- The larger electrochemical driving force for \text{Na}^+ results in a net influx of \text{Na}^+.
- Net effect of opening these channels is depolarization.
- Found at the neuromuscular junction and autonomic ganglia, CNS, and adrenal medulla.
What are Muscarinic receptors
- G protein-coupled receptors.
- Alter the activity of a number of different enzymes and ion channels.
- Subtypes include M1 ,M2, M3, M4, and M5.
What are Adrenergic neurons?
Neurons that release norepinephrine or epinephrine.
What are the major classes of receptors for norepinephrine and epinephrine
*Alpha-adrenergic receptors
* Beta-adrenergic receptors
Tissue location of receptor type alpha 1
Arterioles (coronary, visceral, cutaneous), veins, internal sphincters, iris dilator muscle.
Tissue location of alpha 2 adrenergic receptors
Presynaptic membrane, pancreas, veins, adipose tissue, GIT sphincters, salivary glands.
Tissue location of Beta 1 adrenergic receptor
Heart (SA node, atrial muscle, AV node, ventricles), kidney (JG apparatus), Adipose tissue.
Tissue location of beta 2 adrenergic receptors
Arterioles (muscular), veins, bronchi (muscles), liver, pancreas, uterus, iris constrictor muscle.
Tissue location beta 3 adrenergic receptor
Adipose tissue, urinary bladder.
