Please answer a total of 3 questions for this assignment. Select a question to answer for each of the sections below (Movement, Cycles and Rhythm, Visual System and Auditory System). 1. Movement, Cycles and Rhythms The control of movement is often divided into mechanisms of reflexes and of voluntary movement. What is a reflex? It is a stereotyped, automatic movement evoked by a specific stimulus. It is uniform across members of a species. Some examples in humans are the patellar or kneejerk reflex, the salivary reflex, the orienting reflex, and the pupillary reflex.  In reviewing the reflex arc, pay special attention to proprioception, muscle spindles, the stretch reflex, and primary motor cortex. (Prof. Suzuki also discusses the basal ganglia and the cerebellum, but in another lecture that I have not assigned.)  Further, let's think about the cycles in our behavior. They are ancient and varied. We certainly inherited them from species that evolved earlier than we did. We harbor a number of rhythms. Generally, we have cellular cycles that augment the day-night rhythm to regulate our behavioral cycles. There are possibly very long cycles that govern our evolution. Men and women both run on cycles, though with differences. But do our cycles still make biological sense? Questions ( answer one only ) 1) Can you point to any movements that do not involve reflexes--or some reflexes that do not involve movement? 2) Sleep is tied to recovery of normal function and memory formation. Why does it make sense, then, to stop for sleep just because the sun sets? Why not sleep just whenever we have a backlog of memories to form or we're under stress or sick? Does the wide variation in our daily experience require such an extreme regularity of sleep regulation? Since we don't learn or exercise the same amount each day, why do we nevertheless sleep the same amount? A number of possible answers are given in the first 10 minutes of this fascinating podcast but offer your own insights as well. 3) Furthermore, women show more pronounced cycles in sex hormones than men do, including menstrual cycles and a rather imprecise biological clock with a different origin. Is this an evolutionary leftover, no longer necessary or helpful for humans? Would you want the equivalent of a birth control pill for all of our cycles? 2. Visual System It’s easy to get swamped in detail about the visual system. (This animation may help.)  Videos 10 and 11 discuss the visual pathways that originate in the retina and “ascend” to the visual cortex via the thalamus.  In this week’s resources the retina is revealed as more than a screen for images. Light falls on different classes of photoreceptors, rods and cones, which organize light stimulation according to their pigments by intensity and wavelength. From the duplex nature of the retina there arises a tradeoff between greater acuity in the center and greater sensitivity in the periphery. The output of the retina ...

1. Please answer a total of 3 questions for this assignment. Select
a question to answer for each of the sections below (Movement,
Cycles and Rhythm, Visual System and Auditory System).
1.
Movement, Cycles and Rhythms
The control of movement is often divided into mechanisms of
reflexes and of voluntary movement.
What is a reflex? It is a stereotyped, automatic movement
evoked by a specific stimulus. It is uniform across members of a
species. Some examples in humans are the patellar or kneejerk
reflex, the salivary reflex, the orienting reflex, and the pupillary
reflex.
In reviewing the reflex arc, pay special attention to
proprioception, muscle spindles, the stretch reflex, and primary
motor cortex. (Prof. Suzuki also discusses the basal ganglia and
the cerebellum, but in another lecture that I have not assigned.)
Further, let's think about the cycles in our behavior. They are
ancient and varied. We certainly inherited them from species
that evolved earlier than we did.
We harbor a number of rhythms. Generally, we have cellular
cycles that augment the day-night rhythm to regulate our
behavioral cycles. There are possibly very long cycles that
govern our evolution. Men and women both run on cycles,
though with differences. But do our cycles still make biological

2. sense?
Questions
(
answer one only
)
1) Can you point to any movements that do not involve reflexes-
-or some reflexes that do not involve movement?
2) Sleep is tied to recovery of normal function and memory
formation. Why does it make sense, then, to stop for sleep just
because the sun sets? Why not sleep just whenever we have a
backlog of memories to form or we're under stress or sick? Does
the wide variation in our daily experience require such an
extreme regularity of sleep regulation? Since we don't learn or
exercise the same amount each day, why do we nevertheless
sleep the same amount? A number of possible answers are given
in the first 10 minutes of this fascinating podcast but offer your
own insights as well.
3) Furthermore, women show more pronounced cycles in sex
hormones than men do, including menstrual cycles and a rather
imprecise biological clock with a different origin. Is this an
evolutionary leftover, no longer necessary or helpful for
humans? Would you want the equivalent of a birth control pill
for all of our cycles?
2.

3. Visual System
It’s easy to get swamped in detail about the visual system. (This
animation may help.)
Videos 10 and 11 discuss the visual pathways that originate in
the retina and “ascend” to the visual cortex via the thalamus.
In this week’s resources the retina is revealed as more than a
screen for images. Light falls on different classes of
photoreceptors, rods and cones, which organize light
stimulation according to their pigments by intensity and
wavelength. From the duplex nature of the retina there arises a
tradeoff between greater acuity in the center and greater
sensitivity in the periphery. The output of the retina is further
organized into receptive fields, and sideways connections
between the photoreceptors and horizontal cells sustain lateral
inhibition that sharpens contrasts. A retinotopic map is
preserved by the visual pathways all the way to the visual
cortex; on the other hand, the image still requires a lot of
interpretation by the brain.
Yet when we look at the world we notice only the rich panorama
of detail that relayed to the brain via the fovea.
Questions (answer one only)
1)
How is the retina different from a movie projection screen? Try
to be specific.
2) How on earth did we end up with eyes that are mostly

4. peripheral retina and
only tiny foveas? Should a sensible retina have more foveas—or
larger ones, perhaps? Or might peripheral retina be more than
leftover real estate?
3.
Auditory System
Choose one part of the human ear (or ears in other animals or
the auditory pathways) and describe its contribution to hearing.
Try not to duplicate what another class member has chosen. You
have many choices:
pinna
ear canal
eardrum (tympanic membrane)
ossicles (malleus, incus, stapes)
middle ear muscles (tensor tympani, stapedius)
oval window
round window
basilar membrane
tectorial membrane

5. auditory nerve
Eustachian tube
inner hair cells
outer hair cells
differences in animal ears (whales, birds, bats, desert animals)
earwax (cerumen)
Hensen’s stripe (obscure)
cochlear nuclei
inferior colliculi
medial geniculate nucleus
primary auditory cortex