1.
Know
the sensory Systems: Describe the three component
parts of a typical sensory system
5.
Somatic Sensations: Somatic
sensations start in the receptor endings of surface tissues, skeletal muscles,
and walls of internal organs: they then travel up the spinal cord to the
somatosensory cortex of the brain to be interpreted
6. Describe how hearing works by using mechanoreceptors
1.
The actual structures
that respond to our environment are called receptors. Different
types of receptors exist
1) Each receptor can latch on to an odor molecules of a specific size and shape.
2) The genes for receptor proteins belong to a large family of smell genes.
3) Your sense of smell is a combination of inputs from dozens of receptors.
2.
Sensory Systems
sometimes we get a better understanding of how humans work by trying
to make artificial intelligence. To see
a discussion of androids click this link.
1)
Sensory receptors are the branched endings of sensory
neurons or specialized cells adjacent to them that detect specific stimuli.
a) Receptors are associated with specialized organs.
b) A stimulus is a form of energy capable of eliciting a response by means of an action potential.
2) Nerve pathways lead to the brain.
3) Brain regions process the information into a sensation .
1)
Chemoreceptors detect ions or molecules: they include olfactory
and taste receptors.
2) Mechanoreceptors detect changes in pressure, position, or acceleration: they include receptors for touch, stretch, hearing, and equilibrium.
3) Photoreceptors detect the energy of visible and ultraviolet light.
4) Thermoreceptors detect radiant energy, including infrared.
5) Nociceptors (pain receptors) detect tissue damage.
6) Osmoreceptors detect changes in water volume (solute concentration) in surrounding fluid.
1)
All sensory
receptors convert stimulus energy to local, graded potentials, which may result
in an action potential if the stimulus is intense or repeated fast
enough.
2) Action potentials reach the brain via synapses with interneurons and provide the following information:
a)
Genetically
determined networks of neurons in the brain can interpret incoming action
potentials only in specific ways: for example receptors from eyes see only
light.
b) The stronger the stimulation of a receptor, the greater the frequency of action potentials.
c) Strong stimulation causes a greater number of neurons to fire.
3)
Sensory
adaptation is the
reduction in frequency of depolarization due to a stimulus being maintained as
a constant strength.
3. Somatic Sensations
A.
Somatic
sensations start in the receptor endings of surface tissues, skeletal muscles,
and walls of internal organs: they then travel up the spinal cord to the
somatosensory cortex of the brain to be interpreted. Most pain receptors are near the surface of the body.
1) These sensations are dependent on mechanoreceptors, which are dendrites of sensory neurons, with or without a capsule of epithelial or connective tissue.
2) Many receptors sensitive to touch produce action potentials only when the stimulus begins and ends.
3) Receptors sensitive to pressure respond to a constant stimulus.
1) When the body surface temperature remains constant, the neuron messages to the brain are a steady stream.
2) Increases in temperature cause an increase in firing.
3) The mechanism for detection of cold has not been identified yet.
1) Pain is the perception of injury to some region of the body.
2) Nociceptors in nearly all the body tissues pick up the signals.
a)
The
messages are directed through the thalamus and on to the parietal lobe
of the brain for interpretation.
b) Responses are made to strong mechanical stimulation, intense heat and cold and chemical irritation.
3)
Much
visceral pain is referred, that is felt as some distance from the real
stimulation point.
1) Mechanoreceptors in skeletal muscle, joints, tendons, ligaments, and skin are responsible for awareness of the body’s position and of its limb movements.
2) Stretch receptors in the muscle tissue respond in accordance with the degree and speed of muscle stretching.
4. Taste and Smell
1) Taste receptors in humans are part of the sensory organs called taste buds.
a) Receptors are located on the tongue, roof of the mouth, throat and palate.
b) The four general taste categories are sweet, sour, bitter and salty.
2)
The flavors
of most foods are a combination of the four basic tastes plus sensory input
form olfactory receptors in the nose.
B. Olfaction:
the sense of smell
1)
Olfactory
receptors detect odors.
a)
Many times
the receptors respond to molecules from food or predators (you can often smell
muggers).
b)
The
interpretation of smell is done by the olfactory bulbs located in the
brain
2)
Olfaction
is one of the most ancient senses, useful in survival. Smells can also elicit very strong emotions.
3)
Humans also have a vomeronasal organ whose
receptors can detect pheromones, which are signaling molecules with roles in
sexual attraction.
5. Hearing
A. Hearing requires acoustical receptors
that can detect vibrations, wavelike forms of mechanical energy that show
amplitude (loudness)_ and frequency (pitch).
B. The Ear
1)
The outer
ear collects sound waves and channels them through a canal to an eardrum.
2)
Three small
bones in the middle ear vibrate and amplify the sound.
3)
In the
inner ear, pressure waves in the fluid of the cochlea, stimulate hair
cells.
C. Mechanism of hearing.
1)
Vibrations
are passed form the tympanic membrane to the middle ear bones (malleus,
incus, stapes) to the oval window stretched across the entrance to
the cochlea
a)
Fluid in
the cochlea responds to vibrations causing the basal membrane and hair cells in
the organ of Corti, as well as those in the tectorial membrane, to bend
sending action potentials via the auditory nerve to the brain.
b)
Loudness is
determined by the total number of cells that become stimulated: tone or Pitch
depends on the frequency of vibration.
2)
The round
window at the far end of the cochlea serves as a release valve for the pressure
waves.
3)
The
Eustachian tube extending form the middle ear to the permit equalization of
pressure.
6.
Balance
A. The sense of balance depends on the
organs of equilibrium.
1)
The
vestibular apparatus is a closed system of fluid filled sacs and canals inside
the ear.
a.
In the
semicircular canals, whose canals are arranged in three planes of space, the
jelly like cupula is distorted by movement resulting in the bending of hairs.
b.
Two fluid
filled sacs (utricle and saccule) contain the otolith organs (hair cells) and
otoliths (ear stones) that detect changes in orientation as well as
acceleration and deceleration.
2)
Action
potentials from different parts of the vestibular apparatus travel to reflex
centers in the brainstem and the brain, to be interpreted for ordering
compensatory movements necessary to maintain postural balance.
B. Overstimulation of the hair cells of the
vestibular apparatus can result in motion sickness.
7.
Overview
of eye Structure and function
A. Vision requires structures that are able
to focus (lenses) light onto photoreceptors and brain centers that can
interpret the patterns of action potentials received.
B. Eye Structure
1)
Eyes are
photoreceptor organs that contribute to image formation.
2)
The eye has
three layers, sometime called “tunics”.
a.
The outer sclera
(white of the eye) covers most of the eye: the cornea covers the front.
b.
The middle
layer consists of a dark pigmented choroid, and iris that can
enlarge or diminish the size of the pupil opening, and a lens whose shape can
be altered by the ciliary body muscle.
c.
A clear
aqueous humor bathes both sides of the lens and a vitreous humor fills the
chamber behind the lens.
d.
The inner
layer is the retina, whose axons converge to form the optic nerve.
C. Focusing mechanisms
1)
Because of
the bending of the light rays by the cornea, accommodation must be made by the
lens so that the image is in focus on the retina.
2)
The ciliary
muscle changes the shape of the lens to focus.
3)
If the lens
cannot make sufficient adjustments of the eyeball is not shaped correctly,
corrective lenses must be worn.
8. From Neural Signaling to
visual Perception
A. Organization of the retina
1)
Photoreceptors,
linked to neurons, are located in the retina.
a.
Rods are sensitive to dim light and detect
changes in light intensity.
b.
Cones respond to high intensity light,
contribute to sharp daytime vision, and are packed at the fovea: three types
respond to red, green or blue light.
2)
The sense
of vision is the result of processing the information through levels of
synapsing neurons.
1)
Stimulation
begins in the rods and cones, then moves to bipolar cells and ganglion cells,
the axons of which form the optic nerves.
2)
Before
leaving the retina, signals are dampened or enhanced by horizontal cells and
amacrine cells.
B. Neuronal responses to light
1)
Each rod
contains molecules of rhodopsin that can be altered (cis retinal to trans
retinal) by light, resulting in voltage changes in membranes.
2)
Cone cells
do not use rhodopsin but have different visual pigments for each of the primary
colors.
3)
Visual
perception begins when light strikes receptive fields of ganglionic cells, each
of which is responsible for a tiny circle on the retina.
4)
Axons of
the optic nerves end in lateral geniculate nucleus, from which they proceed to
the brains visual cortex, which has several visual fields sensitive to
direction, movement, color and so on: her is where final interpretation of the
signals is made to produce an organized sense of sight.
Questions to Think about
1 Why is it that the tastiest food is bland and flat when a
person has a bad head cold?
2. What is motion sickness?
3. How can it be controlled?
4. Can you compare
the function of vision as it occurs in a human to that of a computer?
7.
Many people become hard of hearing when they
get older. A tribe in Sudan was shown
to not become deaf. Think of some
reasons that this would occur.
8.
How do the
neurons respond to light?
9.
Is it possible for the eye to function but
the brain to not process the image?
Describe how this can happen.
1)
Smell and
taste are intimately linked. When you
have a cold and your nose is stuffed up, food often tastes very bland. This is because
a) The photoreceptors of the toung can only
distinguish 3 tastes
b) The chemical receptors of the taste buds
can only distinguish four tastes
c) The chemical receptors of the taste buds
can distinguish hundreds of different tastes
d) Smell is a large portion of your taste
sensation and when your nose is not working you only sense the food with your
tongue
2)
What type
of receptors detect heat?
a) chemoreceptors b)
mechanoreceptors c)
Photoreceptors d)
thermoreceptors
3)
Which of
the following correctly indicates the difference between pain reception and
pain sensation?
a) There really is no difference, reception
and sensation occur at the same time in nociceptors.
b) Pain reception occurs at a nerve whose
function is to form an action potential when pain occurs, Pain sensation occurs
in the brain.
c) Pain reception is in the autonomic
portion of the CNS and pain sensation is in the sympathetic portion of the CNS
d) Pain reception occurs in the CNS and pain
sensation occurs in the PNS
Answers: 1) b,d 2) d 3) b
http://isnet.is.wfu.edu/bgsm/nba/faculty/miller/miller.html
a site on this researches work. Is looking pretty cool.
A really cool interactive site on the brain and intelligence
exorcises for the eyes? Who knows, but it probably does not hurt.
http://www.fitfun.com/eyes.html
Neuronal eye simulator look at how eye movements are controlled, requires shock wave http://cim.ucdavis.edu/Eyes/eyesim.htm