chapter 11 - nervous system; part 5

Question 1

what are the 3 components of a chemical synapses?

Answer 1

1. the enlarged ends of the axon are the presynaptic terminals containing synaptic vesicles
2. the postsynaptic membranes contain receptors for the neurotransmitters
3. the synaptic cleft is a space separating the presynaptic and postsynaptic membranes

Question 2

what does an action potential arriving to a presynaptic terminal do?

Answer 2

it causes the release of a neurotransmitter, which diffuses across the synaptic cleft and binds to the receptors of the postsynaptic membrane

Question 3

what are the effects of the neurotransmitter on the postsynaptic membrane is stopped in several ways?

Answer 3

1. it is broken down by an enzyme
2. it is taken up by the presynaptic terminal
3. it diffuses out of the synaptic cleft

Question 4

what is an excitatory postsynaptic potential (EPSP)?

Answer 4

it is a depolarizing graded potential of the postsynaptic membrane; it can be caused by an increase in membrane permeability to NA+

Question 5

what is an inhibitory postsynaptic potential (IPSP)?

Answer 5

it is a hyperpolarizing graded potential of the postsynaptic membrane; it can be caused by an increase in membrane permeability to k+ or Cl-

Question 6

presynaptic inhibition

Answer 6

decreases a neurotransmitter release

Question 7

presynaptic facilitation

Answer 7

increases neurotransmitter release

Question 8

spatial summation

Answer 8

occurs when two or more presynaptic terminals simultaneously stimulate a postsynaptic neuron

Question 9

temporal summation

Answer 9

occurs when two or more action potentials arrive in succession at a single presynaptic terminal

Question 10

inhibitory and excitatory presynaptic neurons

Answer 10

can converge on a postsynaptic neuron; the activity of the postsynaptic neuron is determined by the integration of the EPSPs and IPSPs produced in the postsynaptic neuron

Question 11

convergent pathways

Answer 11

have many neurons synapsing with a few neurons

Question 12

divergent pathways

Answer 12

have a few neurons synapsing with many neurons