Download Solutions to Textbook questions p426

BIO12
Textbook Questions
Nerve Signals
P417#1) CNS includes nerves of the brain and spinal cord. PNS consists of
other nerves. PNS sends messages TO the CNS, which is the “control
center”.
Somatic, autonomic, sympathetic, parasympathetic
Page 412 paragraph 5
Page 413 paragraph 1
P417 #2) Sensory neurons go TO the CNS. Motor neurons come FROM the
CNS.
Neuron, CNS, ganglia, receptors, effectors, afferent, efferent
Page 413, paragraphs 3&4
P417#3)
Dendrites- receives signal from receptor or other neuron
Myelin sheath- insulates the neuron and prevents ion loss
Schwann Cells- makes the myelin sheath
Cell body- contains cell nucleus and holds other organelles
Axon- carries nerve impulse from cell body toward the next neuron or
effector
Nodes of Ranvier, neurilemma
Page 414 paragraphs 1&2
P417#4)
Receptor recognizes a stimulus
Sensory neuron receives impulse from receptor
Interneuron connects sensory neuron directly to motor neuron
(bypassing the brain and speeding up a response)
Motor neuron relays impulse to an effector
Effector makes a response
Reflexes, involuntary
Page 416, Figure 6
P417#5) Both neurons shown are motor neurons. So there must be two
effectors involved in this reflex arc. If neuron I was severed, the muscle
fibre (effector) would not contract, so there would be no muscle
movement. The other response (hair standing up on end?) would still
occur.
Effector, response
Refer back to page 416 to
review reflex arc. This was
an application question,
though.
P426#3) Unqual distribution of positively charged
particles on either side of the membrane
Ions, concentration, -70 mV
P. 419, paragraph 2
P426#4) There are more Na+ ions outside the
neuron than there are K+ ions inside the neuron.
Diffusion, ion gates
P. 419, paragraph 2
P. 419, paragraph 3
BIO12
Textbook Questions
P426#5) Na+ gates open up and Na+ ions enter the
cell, depolarizing it (ie… making it more positive on
the inside of the cell)
Permeable, depolarization
P426#6) When the neuron is stimulated, the
resting potential, which is negative, changes to
become an action potential, which is temporarily
positive. This happens because Na+ gates open up,
Na+ rushes inside, changing the charge inside from
negative to positive. Then the Na+ gates, close and
K+ gates open up, letting out K+. This makes the
potential return to negative. After this, the Na/K
pump restores the K+ and Na+ concentrations to
the resting state (refractory period)
Resting potential, ion gates
P. 418, Figure 2.
P. 419, paragraphs 2,3
P426#7) Rather than a continuous impulse, the
impulse “jumps” from one Node of Ranvier to the
next. Jumping makes the impulse go faster.
Schwann cells, Node of Ranvier
Page 414, paragraph 2.
P426#8) There is a threshold level of stimulus
required to fire an action potential… the minimum
amount required to open up Na+ ion gates. If this
level is reached, the action potential happens . If
not, it doesn’t at all.
Threshold, all-or-none
Page 422, paragraphs 2 & 3.
P426#10) Area B shows the depolarization of the
membrane… potential increases. This must be
where the Na+ channels are open and Na+ is
entering the cell.
depolarization
Refer to page 419, paragraph 3.
Nerve Signals