Lecture 24. Memory and Senses

1. Objectives

1.1. To introduce the basic neurogical basis for short-term and long-term memory

1.2. To introduces the various types of sensors and understand on the influencts the major senses, including touch, taste, smell, hearing, and sight.

1.3. To introduce the various types of behavior and their origin including genetic, hormonal

2. Memory

2.1. Memory is the storage and retrieval of information about previous experiences.

2.1.1. Association is the linkage of information into larger packages that can be sent to other brain regions for storage.

2.1.2. Information becomes stored in "memory traces"-chemical and structural changes in brain regions.

Short-term memory lasts from seconds to hours and is limited to seven to eight bits of information.

Long-term memory is more permanent and seems to be limitless.

2.1.3. Persons suffering from retrograde amnesia (e.g. due to a blow to the head and loss of consciousness oftent lose short-term memory of what happended just prior to the blow), but long-term memory remains intact.

2.3.4. Person with Alzheimer's disease lost their short-term memory but often retain portions of their long-term memory. Over 50% of persons >85 have Alzheimer's symptons.

2.2. Information is moved into long-term storage with the cooperation of epinephrine, which increases a person's state of arousal.

beefs up person's consolidation of memory events.

2.3. Use of memory improves it. Synapses that are used are more extensively developed.

3. Senses

3.1. Sensory Systems

3.1.1. Sensory systems receive stimuli and notify the brain by means of:

sensory receptors

nerve pathways extending from receptors to the brain

brain regions where sensory information is interpreted

3.1.2. Sensation is the conscious awareness of a stimulus.

3.1.3. Types of Sensory Receptors

Chemoreceptors detect ions or molecules; they include olfactory and taste receptors.

Mechanoreceptors detect changes in pressure, position, or acceleration; they include receptors for touch, stretch, hearing, and equilibrium.

Photoreceptors detect the energy of visible and ultraviolet light.

Thermoreceptors detect radiant energy, including infrared.

Nociceptors are pain receptors.

3.1.4. Sensory Pathways

Sensory receptors convert stimulus energy to action potentials.

Action potentials are similar but can be interpreted as different sensations because:

- Different areas of the brain can interpret incoming signals to unique preprogrammed ways.

- Strength of stimulation is determined by the frequency of neuron firing.

- Stronger stimuli cause more neurons to depolarize.

3.2. Somatic Sensations

3.2.1. Somatic sensations include touch, pressure, temperature, and pain near the body surface.

nerve plexus around hair (24.1)

taste bud (diagram) (24-2) (four tastes: sweet (sugar), sour (HCl), salty (NaCl), and bitter (quinine)

taste bud section (24-3)

human olfactory receptors (24-4) (humans can detect about 10,000 odors; influence taste)

3.2.2. Muscle sense uses stretch receptors to notify the brain of limb position in space.

3.2.3. Pressure, Temperature, and Pain

Touch and pressure are detected by mechanoreceptors near the body surface.

Temperature increases result in increased firing from free nerve endings.

Pain, the perception of injury to some region of the body, begins with nociceptors.

- Response to pain depends on the brain's ability to identify the affected tissue.

- Much visceral pain is referred-that is, felt at some distance from the real stimulation point.

3.3. Hearing and Balance

3.3.1. Hearing sounds requires acoustical organs, such as the ears of humans.

	Acoustical receptors are mechanoreceptors that can respond to vibrations, wavelike forms of mechanical energy that show amplitude (loudness) and frequency (pitch).
	In invertebrates, vibrations directly stimulate mechanoreceptors attached to a membrane somewhere on the body.
	In vertebrates, the membrane vibrations cause a fluid inside the ear to be displaced, which in turn causes mechanoreceptors (hair cells) to bend and result in the firing of action potentials, which are sent to the brain for interpretation.

3.3.2. Echolocation

	Bats, dolphins, and whales produce high-frequency sound waves which echo back from objects.
	By assessing the frequency variations in the echoes, these animals can pinpoint the distance and direction of movement of predators, prey, and inanimate objects.

3.3.3. The Human Ear

	ear structure (24-5)
	ear detail (24-6)
	The human ear has regions to receive, amplify, and sort out sound waves.
	However, it does not have provision for tolerating excessive sounds which can lead to permanent damage.
	damaged ear (24-7)

3.3.4. Organs of Balance

	The vestibular apparatus is a closed system of fluid-filled sacs and semicircular canals inside the ear.
	The sense of balance (24-8) depends on the organs of equilibrium that incorporate hair cells that fire off action potentials when bent.
	Otoliths (24-9) are calcium carbonate crystals that respond to gravity or motion for orientation
	Overstimulation of the hair cells of the vestibular apparatus can result in motion sickness.

3.4. Vision

3.4.1. Requirements for Vision

	All organisms are sensitive to light; may invertebrates have photoreceptor cells that detect changes in light intensity but do not form images.
	Vision requires eyes and a complex system of photoreceptors and neural program in the brain that can interpret the patterns of action potentials.
	Some mammals only see varying shades of gray

3.4.2. Structure and Function of Vertebrate Eyes

3.4.2.1. The components of the eye are as follows:

dense white sclera covers the eyeball.

curved, transparent cornea forms the front cover.

light-sensitive retina is at the back of the eye.

transparent lens focuses the light rays.

aqueous body and vitreous body bathe the interior.

choroid layer inside prevents light scattering.

iris adjusts the pupil size.

rods are more sensors of light intensity (rhodopsin (24-10) derived from Vitamin A)

cones are more sensitive to colors (24-11)

diagram of eye (23-12)

photo of eye detail (24-13)

3.4.2.2. 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.

how the eye works (24-14)

In fish and reptiles, the lens is moved forward and back (like a camera lens) to focus. b. In birds and mammals, the ciliary muscle changes the shape of the lens to focus.

3.4.3. Case Study-From Signaling to Visual Perception

3.4.3.1. Photoreceptors, linked to neurons, are located in the retina.

Rods are sensitive to dim light and detect changes in light intensity.

Cones respond to high-intensity light, contribute to sharp daytime vision, and detect colors.

3.4.3.2. The sense of vision is the result of processing the information through levels of synapsing neurons.

Stimulation begins in the rods and cones, then moves to bipolar sensory neurons, then to ganglion cells whose axons form the optic nerves that lead to the brain's visual cortex.

Before leaving the retina, signals flow among horizontal cells and amacrine cells, which dampen or enhance the signals.

3.4.3.3. Neuronal Responses to Light

Each rod cell contains molecules of rhodopsin that can be altered by light, resulting in voltage changes in membranes.

Cone cells carry different pigments for red, green, and blue colors; cone cells at the fovea (center of retina) provide the greatest visual acuity.

Ganglion cells form restricted areas of the retinal surface called "receptive fields" which respond best to small spots of light.

Axons of the two optic nerves end in the lateral geniculate nucleus of the brain, where the positions of the receptive fields correspond to those of the retina; final interpretation of sight occurs in the visual cortex.

cells of human retina (24-15)

4. Critical Concepts or Questions

4.1. What parts of the brain are associated with long-term and short term memory?

4.2. What are six types of human sensors and specific examples of stimuli that they sense?

4.3. What are the four tastes and examples of substances that ellicit them?

4.4. What factors influence the taste of a food?

4.5. You should know the parts of the ear and be able to describe how the ear process sound.

4.6. How does the ear influence your equilibrium? What is the cause of motion sickness?

4.7. You should know the parts of the eye and how it processes light.

4.8. Using a diagram illustrate the cause of farsightedness and nearsightedness? You won't find the details in these notes or your text.

5. Vocabulary

chemoreceptor	nocireceptor	sensory system
cone cell	photoreceptor	stimulus
ear	retina	thermoreceptor
echolocation	rod cell	rhodopsin
eye	sensation	auditory nerve
mechanoreceptor	sensory neuron	optic nerve

6. Webpage Links

Seeing, Hearing, and Smelling the World - Human Senses - Howard Hughes Medical Institute Numerous examples and the connections to the brain.

Psychological Type Profiles - J. Butt, M. Heiss, B. Yamauchi 16 Type profiles with examples.

Human Clock/ Sleep-Wake Cycle - The Center for Biological Timing, U. of Virginia Plenty of graphs and explanations.

Interactive On-line Simulators - BITMed Game of life; Genetic Algorithm; Hypothalmic-pituitary-adrenal axis; Dendritic growth; Hodge rule; etc.

Color Vision Sample Tests - Allendale Eyecare Some of the traditional color dot tests.

UMIST Eye System Sample Tests - C.N. French, UMIST University, UK Great variety of vision tests and links.

Color in Visual Search: A Pictoral Introduction - M. D'Zmura, UC Irvine Finding target items among distractors.

Photomosaics - Images made from thousands of other images - Runaway Technology, Inc. Many amazing images for examination.

	Short-term memory lasts from seconds to hours and is limited to seven to eight bits of information.
	Long-term memory is more permanent and seems to be limitless.

	sensory receptors
	nerve pathways extending from receptors to the brain
	brain regions where sensory information is interpreted

	Chemoreceptors detect ions or molecules; they include olfactory and taste receptors.
	Mechanoreceptors detect changes in pressure, position, or acceleration; they include receptors for touch, stretch, hearing, and equilibrium.
	Photoreceptors detect the energy of visible and ultraviolet light.
	Thermoreceptors detect radiant energy, including infrared.
	Nociceptors are pain receptors.

	Sensory receptors convert stimulus energy to action potentials.
	Action potentials are similar but can be interpreted as different sensations because:

	nerve plexus around hair (24.1)
	taste bud (diagram) (24-2) (four tastes: sweet (sugar), sour (HCl), salty (NaCl), and bitter (quinine)
	taste bud section (24-3)
	human olfactory receptors (24-4) (humans can detect about 10,000 odors; influence taste)

	Touch and pressure are detected by mechanoreceptors near the body surface.
	Temperature increases result in increased firing from free nerve endings.
	Pain, the perception of injury to some region of the body, begins with nociceptors.

	dense white sclera covers the eyeball.
	curved, transparent cornea forms the front cover.
	light-sensitive retina is at the back of the eye.
	transparent lens focuses the light rays.
	aqueous body and vitreous body bathe the interior.
	choroid layer inside prevents light scattering.
	iris adjusts the pupil size.
	rods are more sensors of light intensity (rhodopsin (24-10) derived from Vitamin A)
	cones are more sensitive to colors (24-11)
	diagram of eye (23-12)
	photo of eye detail (24-13)

	how the eye works (24-14)
	In fish and reptiles, the lens is moved forward and back (like a camera lens) to focus. b. In birds and mammals, the ciliary muscle changes the shape of the lens to focus.

	Rods are sensitive to dim light and detect changes in light intensity.
	Cones respond to high-intensity light, contribute to sharp daytime vision, and detect colors.

	Stimulation begins in the rods and cones, then moves to bipolar sensory neurons, then to ganglion cells whose axons form the optic nerves that lead to the brain's visual cortex.
	Before leaving the retina, signals flow among horizontal cells and amacrine cells, which dampen or enhance the signals.

	Each rod cell contains molecules of rhodopsin that can be altered by light, resulting in voltage changes in membranes.
	Cone cells carry different pigments for red, green, and blue colors; cone cells at the fovea (center of retina) provide the greatest visual acuity.
	Ganglion cells form restricted areas of the retinal surface called "receptive fields" which respond best to small spots of light.
	Axons of the two optic nerves end in the lateral geniculate nucleus of the brain, where the positions of the receptive fields correspond to those of the retina; final interpretation of sight occurs in the visual cortex.
	cells of human retina (24-15)