Answers to Illustration Questions 541tion; potassium ions leave the cell during repo-
larization.
7–5: The myosin filaments pull the actin filaments
toward the center of the sarcomere. (A step fur-
ther: Name the proteins that inhibit the sliding
of myosin and actin, and the ion that takes them
out of the way.)
7–6:The muscular, circulatory, respiratory, and
integumentary systems are all part of responses
to exercise.
7–7: Crossing the arm in front of the chest is flexion
of the arm.
7–8: Shape: trapezius (trapezoid), deltoid (the Greek
letter delta)
Size: pectoralis major, gluteus maximus
Location: rectus abdominis, biceps brachii,
latissimus dorsi
A bone: tibialis anterior, biceps femoris, stern-
ocleidomastoid, brachioradialis
Function: adductor longus
7–9: Both orbicularis muscles are circular muscles
that regulate the size of an opening.
7–10: The pectoralis major, latissimus dorsi, and teres
major all move the arm. They are on the trunk
because the sternum and vertebrae provide
strong anchors (origins).
7–11: Flexor muscles of the fingers are on the ante-
rior side of the forearm. You knew because of
the names flexorand digitorum, or you followed
the tendons from the fingers and saw that they
led to these muscles.
7–12: The gastrocnemius is much larger than the tib-
ialis anterior. The gastrocnemius extends the
foot, as when standing on tiptoes or pushing off
to walk. In either case, it must be strong enough
(large enough) to support the entire body.
7–13: The muscles of the female pelvic floor support
the urinary bladder and uterus.CHAPTER 88–1: Effectors are muscle tissues and glands.
8–2: This is an excitatory synapse because sodium
ions enter the postsynaptic neuron, causing
depolarization. At an inhibitory synapse, potas-
sium ions leave the postsynaptic neuron, caus-
ing hyperpolarization.
8–3: An ascending tract carries sensory impulses to
the brain; a descending tract carries motor
impulses from the brain. (Let’s go a step fur-ther: Where are the cell bodies of sensory and
motor neurons located?)
8–4: The spinal cord ends between the first and sec-
ond lumbar vertebrae. This is important for a
lumbar puncture: The needle must be inserted
into the meningeal sac below the end of the
spinal cord.
8–5: The receptor is a stretch receptor, and the mus-
cle that is stretched contracts.
8–6: The corpus callosum connects the cerebral
hemispheres, so that each knows what the other
is doing. It is a flat though slightly arched band
of nerve fibers (white matter) extending left and
right. (A step further: What parts of a neuron
make up white matter?)
8–7: A lateral ventricle extends from the frontal lobe
back through the parietal and occipital lobes,
and forward and down into the temporal lobe.
8–8: The general sensory area in the parietal lobe
feels and interprets the cutaneous senses and
muscle sense.
8–9: The spinal dura mater is a single layer. The cra-
nial dura mater is a double layer, and at inter-
vals contains the cranial venous sinuses.
8–10: Cerebrospinal fluid is reabsorbed from the cra-
nial subarachnoid space, through the arachnoid
villi, into the blood in the cranial venous
sinuses. (A step further: Why is CSF considered
tissue fluid?)
8–11: Secretion of saliva is mediated by the facial and
glossopharyngeal nerves; gastrointestinal secre-
tions are mediated by the vagus nerves.
8–12: Both ANS divisions supply the heart and have
opposite functions. Sympathetic impulses in-
crease the heart rate, and parasympathetic
impulses decrease the rate.CHAPTER 99–1: Most cutaneous receptors are in the dermis;
some are in subcutaneous tissue. (Let’s go a step
further: Which cutaneous receptors are free
nerve endings, and which are encapsulated
nerve endings?)
9–2: The air we inhale (with vapor molecules) goes
down the pharynx and passes the back of the
tongue (with taste buds).
9–3: Tears end up in the nasal cavities.
9–4: The inferior rectus muscle pulls the eyeball
downward, as if you were looking at the floor.29Scanlon(p3) App-G 8/17/06 11:08 AM Page 541