Prelim 2 Questions 11-20 Flashcards
How do we experience the light illusions?
lateral inhibition and summation
In lateral geniculate only if all five cells have APs will a cell in the visual cortex show an AP. Requires a bunch of input all at once. Happens in seeing a line or edge of particular orientation experience inhibition from neighbors. Cortex can see lines or orientation and lines brightly distinguished from what is happening on other side of the line or edge because inhibitory activity can make dark look darker and make an edge of white look whiter
How do we see shapes?
Detecting components spatial frequency (how quickly things change from light to dark) and contrast. Simultaneously perceive both of these aspects when we are discriminating against an object which we don’t recognize unless they’re in conflict.
Explain color perception components, trichromatic theory, and how it relates to color blind.
Components of color perception are brightness, hue, and saturation. Color perception is created by context and previous experience. The trichromatic theory is that there are three kinds of cones and each responds to a different range of wavelengths (colors). The color ranges are wide and overlapping (none peak in red). Precise hue discrimination depends on relative activity of different cones. Our color vision involves looking at the mixes of activation on these different receptor types
There are reduced number of wavelengths in people who are color blind
Explain how color afterimage works
Activated by complimentary colors. Bleaching opsins in eye allows cones and cells to be activated by complementary colors
What is the movement signal pathway?
Motor neurons are in the ventral horn of the spinal cord. Movement signal from the brain goes to one segment of spinal cord to synapses in dorsal horn, sending axons out of the spinal cord into the same nerve that carries sensory information in the end on muscles, will make synapses on muscle fiber.
Explain how sensory feedback is critical for generating correct movement (2 examples)
Two major sensory feedback receptors:
Muscle spindles: in muscles to monitor stretch. Has primary sensory endings and secondary sensory endings. They function in complementary ways; as contract or relax main muscle that then exerts stretch or relaxation on the little muscle inside, little muscle will change its stretch to compensate and to match what is going on
Golgi tendon organ: attached to tendons and monitor tension in tendons due to muscle contraction. Activated by strong force, help prevent damage to muscle or tendon. Extreme mechanism, if the golgi tendon organ starts sending APs into the nervous system it’s saying you’re close to the limit and you shouldn’t push this muscle very much more or you might damage the muscle or tendon
What is the spinal reflex mechanism? (include example with lifting weight)
It is a spinal simple circuit, it does not require input from the brain. Arm out (slight contraction in biceps), weight on arm puts sudden force exerted on muscle, muscle stretches more strongly, sensory system signaled from muscle to dorsal root ganglion and goes to cell bodies in the spinal cord. Synapses on 2 cells, 1 goes back to that muscle and stimulates it to contract more strongly compensating for the weight that is there, the second cell in the spinal cord is inhibitory which has a short axon which synapses onto a neuron that leads to the opposite muscle, the triceps in the back of the arm. Inhibition turns down the number of APs on the second axon leading to active relaxation of the muscle behind your arm, adding strength to the bicep and taking away any tension from opposing muscles (triceps). Automatic circuitry.
What is the relevance of population vectors to human machine interface?
Picking up enough signals in motor or pre motor cortex could be used to compute a population vector (an intention) that then could feed into a robot or a prosthetic device to generate movement
What is the development for the sexes? (presence and absence of androgens)
Male mammals- male has a Y chromosome, SRV gene is on Y and becomes activated, early differentiation of testes from gonad, production of testosterone, masculinization of brain and body (presence of androgens, regression of mullerian ducts and growth of tubes for carrying sperm)
Females- lack of early testosterone leads to development of female gonads, genitalia, and brain circuits. (absence of androgens, regression of wolffian ducts and growth of mullerian into fallopian tubes and uterus)
Explain how male and female sexes are part of a continuum (androgen insensitivity syndrome, congenital adrenal hypertrophy (CAH), XX and exposure to environmental androgens, guevedoces)
Androgen insensitivity syndrome- (not responsive to androgens) gene for androgen receptor is on the X chromosome. Act and appear female but have testes
congenital adrenal hypertrophy (CAH)- adrenal cortex too active, XX plus androgens, act and appear male, but have ovaries
XX and exposure to environmental androgens- appear male but also develop ovaries and uterus inside
Guevedoces- 5 alpha reductase deficiency, can’t convert testosterone intermediate, raised as girl then shifts in adolescence to male like
These observations indicate at the most basic level that male and female are part of a continuum, the absolute roles assigned to males and females are based on culture, not biology
