Chapter 12 - Neurophysiology - Continued

Question 1

2 Kinds of Synapses

Answer 1

1. Electrical synapse
2. Chemical synapse
   a. Excitatory synapses
   b. Inhibitory synapses

Question 2

Presynaptic neuron

Answer 2

sends the signal; releases neurotransmitter by exocytosis

Question 3

Postsynaptic neuron

Answer 3

receives the signal; bonds the neurotransmitter

Question 4

Electrical synapse

Answer 4

direct connection between 2 neurons so electrical signal can go from 1 to the next neuron; action potential keeps going; connected together electrically; extremely rare–few places in brain have them; absent in PNS; more common in muscle tissue–cardiac muscle & smooth muscle; gap junctions found here

Question 5

Chemical synapse

Answer 5

rely on neurotransmitters; chemical released by one neuron & binds to receptors on 2nd neuron; causes opening of ion channels & ions can charge; most common type of synapse in N.S.; transmission–how signal crosses to another cell

Question 6

Excitatory synapses

Answer 6

affect on postsynaptic neuron;
Excitatory post-synaptic potentials (EPSPs) are graded depolarizations; cause membrane potential to get more positive; post-synaptic MORE likely to reach threshold

Question 7

Inhibitory synapses

Answer 7

gets more & more negative; LESS likely for postsynaptic neuron to reach threshold;
Inhibitory post-synaptic potentials (IPSPs) are graded hyperpolarizations; signal will stop & not reach 2nd neuron–less likely for neuron to release action potential

Question 8

Summation happens at

Answer 8

axon hillock; all iPSPs & EPSPs are “summed”; if EPSPs are > than IPSPs & it reaches threshold, action potential happens & signal goes further

Question 9

Each & every neuron in brain, synapses with

Answer 9

1,000 other neurons

Question 10

Neurotransmitters released only at

Answer 10

chemical synapses (about 100 neurotransmitters)

Question 11

In PNS, 2 main neurotransmitters:

Answer 11

1. Acetylcholine (ACh) - truly excitatory when released @ neuromuscular junction
2. Norepinephrine (NE) - can be either excitatory or inhibitory

Question 12

In CNS, 2 examples of neurotransmitters & there general affect

Answer 12

majority NT in brain; the following 2 NT produce graded potentials in post synaptic neurons:

1. Serotonin - mood, sensory perception
2. Dopamine - motor control