Test 4 Flashcards
Sensation:
How our sense receptors and nervous system physically represent our external environment
Perception:
How we mentally organize and interpret sensory information
What are the 3 steps from sensation to perception?
- Reception: absorption of physical energy by the receptors
- Transduction: converting physical energy to electrochemical patterns in the neurons
- Coding: one to one correspondence between physical stimulus and nervous system activity
Law of Specific Nerve Energy:
- Any impulse in a given nerve sends the same kind of message (AP) to the brain
– AP from auditory nerve = sound, olfactory = odor, optic = light - Brain differentiates one sensory modality from another by which neurons are active
Pathway of Light:
- Light enters the eye through the pupil (eye’s small opening)
- It is focused by the
– Lens (adjustable)
– Cornea (not adjustable) - It is projected to the retina (rear surface of the eye) which is lined with visual receptors
– Rods - black & white: responds to faint light most abundant in retina periphery
– Cones - color vision: more useful in bright light most abundant in around fovea - Light from the R field of vision strikes L side retina & Top strikes Bottom
– Just like a camera–the image is reversed - 3mm x 5mm are in center of retina = macula
- center of macula: fovea: most precise vision, specialized for acute, detailed vision
- Blindspot: no receptors here, where optic nerve & axons meet at the back of the eye
Visual Path:
Temporal cortex (lobe)
- contains ventral stream
– “what” pathway
- identify recognize object
Parietal cortex (lobe)
- contains dorsal stream
– “where”/”how” pathway
– visually guided movements: helps motor system find objects & determine how to move toward them/grasp them/ change item location
What is the sequence through which visual information passes?
1) Receptor cells in the back of the eye send messages to
2) Bipolar cells which are neurons located to the center of the eye
3) Ganglion cells which are still closer to the center of the eye
4) Ganglion cells join one another to form the optic nerve, loop around and travel back to the brain
5) Optic nerves from the right and left eye initially meet at the optic chiasm where 1/2 of axons from each eye cross to the opposite side of the brain
6) Most axons then travel to the lateral geniculate nucleus (LGN) of the thalamus which communicates with the
7) Visual Cortex
What is the Young-Helmholtz Theory?
Aka trichromatic theory
- perceive color by relative rates of response by three kinds of cones: red-long, blue-shorter, green-medium
What is the Opponent-Process Theory?
(Hering)
- perceive color in terms of paired opposites, three receptor complexes: red vs. green, yellow vs. blue, white vs. black
What is the Retinex Theory?
Aka color constancy (Edwin Land)
- Retina + cortex
- Information from various parts of the retina reaches the cortex
- cortex compares imputes to determine brightness and color perception
- We can perceive color despite changes in lighting (brightness)
What are refractive errors?
- Myopia
- Hyperopia
- Astigmatism
- Presbyopia
What is myopia?
(nearsightedness)
Objects up close appear clear, further away blurry
What is hyperopia?
(farsightedness0
Objects far away clear, close blurry
What is Astigmatism?
- Asymmetric curvature of the eyes
- Blurred vision for lines in one direction
What is presbyopia?
- Age-related condition
- Ability to focus up close becomes more difficult
What are the deficiencies in vision?
- Color vision deficiency
- Color blindness
- Motion blindness
- Visual Agnosia
- Prosopagnosia
- Lazy ye
- Strabismus
What is color vision deficiency?
- Inability to perceive color differences
- genetic (males)
What is color blindness?
Inability to perceive anything but shades of black, white, and gray
What is motion blindness? What causes it?
“Akinetopsia” from tumor, injury, stroke
- Failure to detect an object is moving or if able to detect the direction or speed of motion
What is visual agnosia?
Inability to recognize objects despite satisfactory vision
What is prosopagnosia?
Inability to recognize faces
What is lazy eye?
“amblyopia ex anopsia”
- Child ignores vision in one eye letting it drift
What is strabismus?
- Eyes don’t point in same direction
- Inability for both eyes to focus on the same thing
What is pain and what responds to it? (FIB)
- The experience evoked by a harmful stimulus and directs one’s attention toward a danger
- The prefrontal cortex responds to pain as along as the pain lasts
What are the three actions after pain? (List)
- Axons carrying pain info have little or no myelin
- Impulses travel slowly
- Brain processes pain information rapidly and motor responses are fast
What are the differences between intensity of pain? (FIB)
- Mild pain triggers the release of glutamate in the spinal cord
- Stronger pain triggers the release of glutamate and releases several neuropeptides including substance P and CGRP (calcitonin gene-related peptide
What are the spinal pathways for touch and pain? (FIB)
Pain information crosses to the contralateral side of the spinal cord immediately whereas touch information does not cross until the medulla
What are the aspects of emotional pain? (FIB)
- Emotional associations of pain
– activate a path that goes through the reticular formation of the medulla
– and then to several of the central nuclei of the thalamus the amygdala, hippocampus, prefrontal cortex and cingulate cortex - Experimenters monitored people’s brain activity and found that hurt feelings activate the same pathway
What are the five ways of relieving pain?
- Placebo
- Cannabinoids
- Capsaicin
- Opioids
- Endorphins
What is the description and function of a placebo?
- Description: a drug or other procedure with no pharmacological effect
- Function: Decreases the brain’s emotional response to pain perception, not the sensation itself
What is the description and function of cannabinoids?
- Description: chemicals related to marijuana that block certain kinds of pain
- Function: Act mainly in the periphery of the body rather than the CNS
What is the description and function of capsaicin?
- Description: Chemical found in jalapenos that stimulate receptors for heat
- Function: Produces a temporary burning sensation followed by a longer period of decreased pain
What is the description and function of opioids?
- Description: Opiates act on the CNS rather than the injured tissue
- Function: The brain puts the brakes on prolonged pain by opioid mechanisms
What is the description and function of endorphins?
- Description: Opiate-type chemicals of the CNS
- Function: A contraction of endogenous morphine. The brain produces several types of endorphins which relieve different types of pain
What are the general structures of the ear? (Handout)
Pinna, External auditory canal, tympanic membrane (eardrum), hammer, anvil, stirrup, semicircular canals, cochlea, auditory nerve
What are the structures of the inner ear? (Handout)
- Basilar membrane, hair cells, auditory nerve, oval window (membrane behind stirrup)
- Scala vestibuli (tip), scala media, scala tympani
- Cochlear neuron, basilar membrane, hair cells
What is audition?
Soundwaves:
- Stimulus for hearing
- Jostling molecules of air
- Amplitude: (intensity) determines loudness
- Frequency: (# compressions per sec) determines pitch
- Average Adult: 15-20,000 Hz
What are the aspects of the outer ear?
- “Pinna”
- Helps locate sound
- Sound waves pass though auditory canal and strike the tympanic membrane (middle ear)
What are the aspects of the middle ear?
- Tympanic membrane is attached to three tiny bones
1. Hammer/Malleus
2. Anvil/Incus
3. Stirrup/Stapes
(As they vibrate) gain force (communicated to) - Oval window: membrane covering the opening from the middle ear to the cochlea to the inner ear forces increase causing wave-like action
What are the aspects of the inner ear?
- Cochlea (snail shaped tube): 3 fluid-filled tunnels
– Scala vestibuli/media/tympani - Tectorial membrane: more rigid
- Basilar membrane: more flexible
What happens to the vibrations from the oval window?
- Vibrations set the fluid in motion stimulating hair cells which open ion channels
- Excitatory synapses –> auditory nerve –> CN VIII –> primary auditory cortex –> temporal lobe
What is notable about the primary auditory cortex?
Tonotopic Map: map of sounds
- The cortical area with the greatest response indicates which sounds are heard
What is the frequency theory?
Basilar membrane vibrates in synchrony with sound. Causing auditory nerve axons to produce APs at the same frequency
What is the place theory?
every sound causes one location along the basilar membrane to resonates and excites neurons in that area (like a piano)
What is the volley principle?
Volley of responses by many auditory neurons
- ave. 4,000/sec
What is the prevalent theory of pitch perception?
A combination of all three: frequency theory, place theory, volley principle
What is amusia?
- Tone deafness
- can’t detect change in tone
- can’t recognize tune
- can’t tell someone else signing off key
- may be genetic
What is absolute pitch?
- Perfect pitch
- hear a note and identify it
- early musical training may help develop
- may be genetic
What are the aspects of the Auditory Cortex? (Pathway)
- “what” pathway - sensitive to patterns of sound in the
*anterior temporal cortex - “where” pathway - to sound location
*posterior temporal cortex
What cortical motion deafness?
A person hears a sound but cannot detect that source of sound is moving
What Conductive Deafness?
(Middle ear)
- caused by: disease, infection, tumorous bone growth
- may be temporary, usually can be corrected by surgery or hearing aids (hearing aids have more success with conductive than nerve)
*hear themselves clearly and may accuse others of talking too softly or mumbling.
Why do those with conductive deafness hear themselves clearly?
Can hear their own voice better than external sounds because sound is conducted through bones of the skull directly to the Cochlea bypassing the middle ear
Nerve deafness:
(inner ear)
- can hear some frequencies better than others
- caused by damage to the cochlea, basilar membrane, auditory nerve
- may be genetic
- may result from disease
What causes nerve deafness?
- Mom - German measles, syphilis, other teratogens –> baby may be born deaf
- Inadequate oxygen at birth
- MS
- meningitis,
- childhood reactions to Rx (aspirin)
- repeated exposures to loud noises
- may be tinnitus: ringing in ears (constant)
What is tinnitus?
- similar phenomenon to phantom limb
- damage to nerve endings in the inner ear
- leading cause: loud noises,
- others: wax in ear canal, stiffening of middle ear bones, allergies, increased/decreased BP, thyroid problems, injury to neck/head, medications
What is the route of auditory impulses?
- Cochlear nucleus receives input from ipsilateral ear
- impulse travels to the superior olive
- then to inferior colliculus
- then to the medial geniculate
- and finally to the primary auditory cortex
