Download Nervous System Quiz Answers

Nervous System Quiz
Name _____________________
Points Possible ________ 25 pts
1. Compare and contrast the different types of cells found in the CNS. (8pts)
Astrocytes – “star cells” provide support, regulate nutrients and ion concentration.
Oligodendrocytes – wrap around cell process within CNS producing myelin
Microglia – phagocytes of CNS engulf invading microorganisms and dead neurons.
Ependymal – simple epithelium that lines central cavity of brain and spinal cord.
NOTE: I did not list the Schwann cells because they are part of the PNS not CNS.
2. How does a nerve send a “message” when stimulated? (8pts)
-A resting neuron is polarized when more Na+ is outside the membrane the K+ inside the
membrane (-70mv). + (pos) outside and – (neg) inside the membrane
1. Resting potential decrease as Na+ ions enter the cell making the inside more positive
and outside negative.
2. Threshold of -59 mv is reached and voltage gated Na+ channels open causing the
neurons membrane to become depolarized (- in and +).
3. Na+ ions continue to diffuse until the voltage reaches around +30mv. This triggers
the voltage Na+ channels to shut and the voltage K+ channels to open. The K+ ions
diffusing outward causes the membrane to repolarize +(pos) outside and –(neg) inside.
4. Hyperpolarization- repolarization overshoots the RMP when more K+ ions are
released and voltage moves to about -90 mV.
5. Na/K Pump restores membrane back to resting membrane potential.
3. Explain why a myelinated nerve travels at 150 m/s and an unmyelinated at only 1
m/s. (Hint: describe the process). (2pts)
Myelinated nerve travels faster b/c myelin increases the surface area, it conducts better,
and the action potential skips from node to node (Nodes of Ranvier).
Unmyelinated lacks the insulator and nodes so the action potential travels the entire
length of the axon which decreases the rate of conduction.
4. What is a synapse? How does it work? (4pts)
A synapse is a gap or junction between an axon of one neuron and the dendrites of an
adjacent neuron, or the junction between an axon and an effector organ/gland.
How it works: Neurotransmitters are released from the presynaptic terminal/membrane
into the synapse in response to an action potential. The neurotransmitters bind to
receptors on the postsynaptic membrane causing ion channels to open.
5. What are the roles of neurotransmitters and where do they function in relation to
the neuron? (3pts)
Role of neurotransmitters – chemical substances that transmit signals/messages across
a synapse.
Function in stimulating or inhibiting action potentials.