Answers to Test & Quantitative and Thought Questions
that contains ﬁ bers of the pathways for temperature
would interfere with awareness of a heat stimulus
on the right. Thus, damage to the somatosensory
cortex of the left cerebral hemisphere (i.e., opposite
the stimulus) would interfere with awareness of the
stimulus. Injury to the spinal cord at the point at
which ﬁ bers of the anterolateral system from the two
halves of the spinal cord cross to the opposite side
would interfere with the awareness of heat applied to
either side of the body, as would the unlikely event
that damage occurred to relevant areas of both sides
of the brain.
Vision would be restricted to the rods; therefore, it
would be normal at very low levels of illumination
(when the cones would not be stimulated anyway),
but at higher levels of illumination clear vision of ﬁ ne
details would be lost, and everything would appear
in shades of gray, with no color vision. In very bright
light, there would be no vision because of bleaching
of the rods’ rhodopsin.
(a) The individual lacks a functioning primary visual
cortex. (b) The individual lacks a functioning visual
See Figure 8–6.
If by experience you discover that a persistent
stimulus like the noise from a fan does not have
relevance, there is a reduction in conscious attention
directed toward that stimulus. This is an example of
The mesolimbic dopamine pathway mediates
the perception of reward that is associated with
adaptive behaviors, including goal-directed
behaviors related to preserving homeostasis, like
eating and drinking.
Serotonin-speciﬁ c reuptake inhibitors (SSRIs) are
the most widely used antidepressant drugs, although
other types of antidepressants additionally enhance
signaling by norepinephrine.
Short-term, or “working” memories are transferred
into new long-term memories in the process
of consolidation, which requires a functional
hippocampus. When the hippocampus is destroyed,
previously formed long-term memories remain
intact, but the ability to form new memories is lost.
Broca’s area is located near the region of the left
frontal lobe motor cortex that controls the face;
when it is damaged, individuals have “expressive
aphasia.” This means that they comprehend language
but are unable to articulate their own thoughts into
Quantitative and Thought Questions
Dopamine is depleted in the basal ganglia of people
with Parkinson’s disease, and they are therapeutically
given dopamine agonists, usually L-dopa. This
treatment raises dopamine levels in other parts of
the brain, however, where the dopamine levels were
previously normal. Schizophrenia is associated with
increased brain dopamine levels, and symptoms of this
disease appear when dopamine levels are high. The
converse therapeutic problem can occur during the
treatment of schizophrenics with dopamine-lowering
drugs, which sometimes cause the symptoms of
Parkinson’s disease to appear.
Experiments on anesthetized animals often involve
either stimulating a brain part to observe the
effects of increased neuronal activity, or damaging
(“lesioning”) an area to observe resulting deﬁ cits.
Such experiments on animals, which lack the complex
language mechanisms humans have, cannot help with
language studies. Diseases sometimes mimic these
two experimental situations, and behavioral studies of
the resulting language deﬁ cits in people with aphasia,
coupled with study of their brains after death, have
provided a wealth of information.
A single skeletal muscle ﬁ ber, or cell, is composed of
many myoﬁ brils.
The dark stripe in a striated muscle that constitutes
the A band results from the aligned thick ﬁ laments
within myoﬁ brils, so thick ﬁ lament length is equal to
As ﬁ laments slide during a shortening contraction,
the I band becomes narrower, so the distance between
the Z line and the thick ﬁ laments (at the end of the A
band) must decrease.
DHP receptors act as voltage sensors in the T-tubule
membrane and are physically linked to ryanodine
receptors in the sarcoplasmic reticulum membrane.
When an action potential depolarizes the T-tubule
membrane, DHP receptors change conformation
and trigger the opening of the ryanodine receptors.
This allows calcium to ﬂ ood from the interior of the
sarcoplasmic reticulum into the cytosol.
In an isometric twitch, tension begins to rise as
soon as excitation-contraction is complete and the
ﬁ rst cross-bridges begin to attach. In an isotonic
twitch, excitation-contraction coupling takes the
same amount of time, but the ﬁ ber is delayed from
shortening until after enough cross-bridges have
attached to move the load.
In the ﬁ rst few seconds of exercise, mass-action
favors transfer of the high-energy phosphate from
creatine phosphate to ADP by the enzyme creatine