Bio 212 Exam 4 Iowa State Questions and
Answers|Latest Update
Repolarization Na- channels close and K- channels open
K- rushes out of the cell
Hyperpolarization Na- and K- channels are closed
Sodium/potassium pump moves Na- out and K- in
Steps that Occur when an action Potential reaches the axon terminal 1. Action potential
(depolarization) opens voltage gated Ca++ channels
2. Ca++ enters the presynaptic terminal and triggers exocytosis releasing neurotransmitter into
synaptic cleft
3. Transmitter diffuses across cleft and binds to ligand gated channels or receptors in
postsynaptic cell membrane
, Bio 212 Exam 4 Iowa State Questions and
Answers|Latest Update
4. Binding of neurotransmitter changes membrane potential of postsynaptic cell. Can be
excitatory or inhibitory
5. To end synaptic signal-neurotransmitter in cleft is broken down or re uptake into presynaptic
terminal for repackaging into vesicles.
Characteristics of Schwann Cells Part of the PNS
Make up the myelin sheath
Keep ions from leaking out of the axon
Benefits of a Myelin Sheath Layers of the myelin membrane insulate the axon membrane
Myelinated axons conduct impulses faster than unmyelinated axons
How does Pufferfish toxin (tetrodotoxin) affect an action potential? It inhibits the
opening of voltage gated Na+ channels
Xylem Transports only minerals and water from roots
Answers|Latest Update
Repolarization Na- channels close and K- channels open
K- rushes out of the cell
Hyperpolarization Na- and K- channels are closed
Sodium/potassium pump moves Na- out and K- in
Steps that Occur when an action Potential reaches the axon terminal 1. Action potential
(depolarization) opens voltage gated Ca++ channels
2. Ca++ enters the presynaptic terminal and triggers exocytosis releasing neurotransmitter into
synaptic cleft
3. Transmitter diffuses across cleft and binds to ligand gated channels or receptors in
postsynaptic cell membrane
, Bio 212 Exam 4 Iowa State Questions and
Answers|Latest Update
4. Binding of neurotransmitter changes membrane potential of postsynaptic cell. Can be
excitatory or inhibitory
5. To end synaptic signal-neurotransmitter in cleft is broken down or re uptake into presynaptic
terminal for repackaging into vesicles.
Characteristics of Schwann Cells Part of the PNS
Make up the myelin sheath
Keep ions from leaking out of the axon
Benefits of a Myelin Sheath Layers of the myelin membrane insulate the axon membrane
Myelinated axons conduct impulses faster than unmyelinated axons
How does Pufferfish toxin (tetrodotoxin) affect an action potential? It inhibits the
opening of voltage gated Na+ channels
Xylem Transports only minerals and water from roots
