Exam 3 Flashcards
Describe each sensory receptor.
Vision: light energy -> chemical energy
Auditory: air pressure -> mechanical energy
Somatosensory: mechanical energy
Taste and Olfaction: chemical molecules
What is the relationship between receptor density and sensitivity.
the more dense the receptors, the greater the sensitivity
What is the topographic map?
a neural-spatial representation of the body or of the areas of the sensory world perceived by a sensory organ
How do we perceive light?
Wavelengths differ from 400 nanometers to 700 nanometers
What is the fovea?
region at the center of the retina that is specialized for high acuity; rod-free area
How does acuity differ across the visual field?
Vision is best in the center and then weakens in the periphery
What is the blind spot of the retina?
the optic disc (where axons forming the optic nerve leave the eye)
Describe rod cells.
More numerous than cones
Sensitive to low levels of light
Used mainly for night vision
One type of pigment
Describe cone cells.
Highly responsive to bright light
Specialized for color and high visual acuity
Located in the fovea only
Three types of pigment
What three pigments do cones receive?
419nm - blue
531nm - green
559nm - red
What is the least numerous color of cone receptor?
blue
What are the retinal-neuron types?
Bipolar cell - input from photoreceptors
Horizontal cell - links photoreceptors and bipolar cells
Amacrine cell - links bipolar and ganglion cells
Retinal ganglion cell (RGC) - gives rise to optic nerve
What are M cells? P cells?
M cells - receive input primarily from rods, sensitive to light and moving stimuli
P cells - receives input primarily from cones, sensitive to color
Describe the geniculostriate system?
Projections from the retina to the lateral geniculate nucleus to the visual cortex; detailed visual system
Describe the tectopulvinar system?
projections from the retina to the superior colliculus to the pulvinar (thalamus) to the parietal and temporal visual areas; less color vision based; involved in movement sensing, where objects are
Describe the retinohypothalamic tract.
synapses in the tiny suprachiasmatic nucleus (SCN) in the hypothalamus; role in regulating circadian rhythms and in the pupillary reflex
Describe the dorsal visual stream.
pathway that originates in the occipital cortex and projects to the parietal cortex; the “how” pathway (how action is to be guided toward objects)
Describe the ventral visual stream.
pathway that originates in the occipital cortex and projects to the temporal cortex; the “what” pathway (identifies what an object is)
Describe the four types of injuries to the pathway leading to the cortex.
Monocular blindness - destruction of the retina or optic nerve of one eye that produces loss of sight in that eye
Homonymous hemianopia - blindness of the entire left or right visual field
Quadrantanopia - blindness of one quadrant of the visual field
Scotoma - small blind spot in the visual field caused by a small lesion or migraines of the visual cortex
What is optic ataxia?
deficit in the visual control of reaching and other movements; damage to parietal cortex; can recognize objects normally
What is injury to the “what” pathway?
visual form - inability to recognize objects or drawings of objects
color - inability to recognize colors
face - inability to recognize faces
Describe Broca’s area.
anterior speech area in the left hemisphere that functions with the motor cortex to produce the movements needed for speaking
Describe Wernicke’s area.
posterior speech area at the rear of the left temporal lobe that regulates language comprehension; also called the posterior speech zone
What is Broca’s aphasia?
inability to speak fluently
What is Wernicke’s aphasia?
inability to understand or to produce meaningful language
Auditory Cortex mapping
Passively listening to noise bursts activates the primary auditory cortex; listening to words activates the posterior speech area; making a phonetic discrimination activates the frontal region (suggesting we run speech sounds through Broca’s area to figure out what they are)
How do different kinds of sounds affect areas of the brain thought to be involved in audition and music perception?
passively listening to noise bursts activates Heschl’s gyrus; perception of melody triggers activation in the right hemisphere auditory cortex lying in front of Heschl’s gyrus; making relative pitch judgments about two notes of each melody activates a right frontal lobe area
How does music help those with Parkinson’s?
listening to rhythm activates the motor and premotor cortex and can improve gait and arm training after a stroke
What are the three major components of the motor system?
Cerebrum - conscious control of movement
Brainstem - direct movements
Spinal cord - direct movements
Describe the motor sequence.
Prefrontal cortex: plans complex behavior
Premotor cortex: produces the appropriate complex movement sequences
Primary motor cortex: specifies how each movement is to be carried out
What is the relationship between the brainstem and species-specific behaviors?
Hess (1950s) stimulated different areas within the brainstem to produce different species-specific behaviors
What is cerebral palsy?
voluntary movements become difficult to make, caused by brainstem trauma, usually perinatally; movements can be clumsy, may see too much muscular rigidity, walking on toes or crouched gait
How did Penfield create the topographic map?
he used electrical stimulation to map to cortices
Which parts of the body are mapped disproportionately compared to the amount of space they occupy?
hands, fingers, lips, and tongue are disproportionately larger than parts of the motor cortex that control other areas
What are the three types of organization in the motor cortex?
the part of the body that is to be moved, the spatial location to which the movement is directed, and the movements function
Motor Cortex and Skilled Movement
Studies using human participants reveal a
number of situations in which motor-cortex
neurons are active at the same time that no
movement occurs.
Describe the plasticity in the motor cortex.
without rehab: the hand area of the motor cortex became smaller whereas the elbow and shoulder area became larger; lost ability to move hand
with rehab: hand area of the motor cortex retained its size; retained some ability to move hand
Describe the corticospinal tract.
main efferent (away) pathways from the motor cortex to the brainstem to the spinal cord; axons descend into the brainstem, sending collaterals to a few brainstem nuclei, and eventually emerge on the brainstem’s ventral surface where they form a large bump on each side (pyramidal tracts)
What does the lateral corticospinal tract control?
branches at the brainstem level, crossing over to the opposite side of the brain and spinal cord; moves the digits and limbs on the opposite side of the body
What does the ventral corticospinal tract?
remains on the same side of the brain and spinal cord; moves the muscles of the midline body (trunk) on the same side of the body
How are limb muscles arranged?
in pairs
Extensor - moves the limb AWAY from the trunk
Flexor - moves the limb TOWARD the trunk
Describe the basal ganglia and the force of movement?
Receive input from all areas of the neocortex and allocortex, including motor cortex; project back to the motor cortex and substantia nigra; serve a wide range of functions including association or habit learning, motivation, emotion, and motor control
Describe hyperkinetic symptom.
when damage to the caudate putamen causes unwanted writhing and twitching movements called dyskinesias; Huntingtons and Tourette’s
Describe hypokinetic symptom.
when damage to the basal ganglia results in a loss of motor ability, leading to rigidity and difficulty initiating and producing movement; Parkinsons
What is the volume hypothesis?
the internal globus pallidus (Gpi) acts like a volume control on the thalamus and motor cortex
What are the two pathways within the basal ganglia?
Direct: when activated the GPi is inhibited and the pathway is freed to produce movement
Indirect: when activated, the GPi is activated and it inhibits the thalamus, thus blocking movement
What are the anatomical parts of the cerebellum and what do they control?
Flocculus: small but dense lobe involved in eye movements and balance
Lateral Hemisphere: controls movement of limbs, hands, feet, and digits
Medial Hemisphere: controls movement of face and midline of body