Chapter 12 Part 3 Axon Diameter & Speed

Question 1

Propagation speed down the axon depends on

Answer 1

• Myelination (myelinated axons are Saltatory Propagation
• Axon diameter (the larger the diameter, the faster the speed )

Question 2

Axons are classified by diameter, myelination, speed of action potential, 3 types?

Answer 2

1. Type A fibers
2. Type B fibers
3. Type C fibers

Question 3

Type A Fibers

Answer 3

-Myelinated
-Large diameter
-High speed (120 m/sec)
-used for vision, balance, and motor commands

Question 4

Type B Fibers

Answer 4

-Myelinated
-Medium diameter
-Medium speed (18 m/sec)
-used for sensory information)

Question 5

Type C Fibers

Answer 5

-Unmyelinated
-Small diameter
-Slow speed (1 m/sec)
-Carry information to effectors (smooth muscle,
gland secretion)

Question 6

____synapses occur when there is direct contact between cells.
-Cells are locked together at gap junctions that allow ions to pass between cells to the next
-Are found cardiac muscle

Answer 6

Electrical Synapses

Question 7

___synapse that occurs when cells are separated by a synaptic cleft.
- A neurotransmitter carries a message from the presynaptic cell to the postsynaptic cell. Most common synapse ex. NMJ

Answer 7

Chemical Synapses

Question 8

Excitatory Synapse Causes _____of postsynaptic membranes
* Promote action potentials

Answer 8

depolarization

Question 9

Inhibitory Synapse
Causes ______ of postsynaptic membranes
* Suppress action potentials

Answer 9

hyperpolarization

Question 10

___Synapse Causes DEPOLARIZATION of postsynaptic membranes
* Promote action potentials
=CELL IS LESS NEGATIVE

Answer 10

Excitatory Synapse

Question 11

____Synapse
Causes HYPERPOLARIZATION of postsynaptic membranes
* Suppress action potentials
=CELL IS MORE NEGATIVE

Answer 11

Inhibitory Synapse

Question 12

-a chemical synapse that uses ACH as NT
-excitatory
-include NMJ, neuromuscular, neuroglandular synapses of Parasympathetic NS
-Summarize event happening on this synapse

Answer 12

Cholinergic Synapse

Question 13

Events at a Cholinergic Synapse

Answer 13

1. AP arrives at synaptic terminal
2. Calcium ions enter synaptic terminal, trigger exocytosis of ACh
3. ACh travel across synaptic cleft and binds to receptors on postsynaptic membrane
4. Sodium channels open allowing the sodium to enter the postsynaptic membrane cell causing depolarization
5. AChE breaks ACh

Question 14

-uses GABA as NT Gama-aminobutyricacid (GABA)
-inhibitory synapse
-GABA binds to a receptor on the postsynaptic cell causing HYPERPOLARIZATION.
-inhibits the cell because it brings it further away from THRESHOLD voltage.

Answer 14

GABA-ergic synapse

Question 15

Graded depolarization that occurs when Na+ or Ca+ channels are opened

Answer 15

Excitatory postsynaptic potential (EPSP)

Question 16

Graded hyperpolarization that occurs when K+ or Cl- channels are opened

Answer 16

Inhibitory postsynaptic potential (IPSP)

Question 17

____Summation (wave summation)
*postsynaptic Cell is stimulated multiple times
at one synapse

Answer 17

Temporal Summation (wave summation)

Question 18

____Summation
* postsynaptic Cell is stimulated at multiple locations at multiple synapses simultaneously

Answer 18

Spatial Summation