Brain And Behavior Exam 4

In the absence of the Sry protein, the indifferent gonad develops into an ovary. The Sry protein is responsible for initiating the development of testes. Without this protein, the default pathway for sexual development is the formation of ovaries.

Rats have the highest heat production per unit of body weight compared to cats, humans, and elephants. This is because rats have a higher metabolic rate, which means they generate more heat through their metabolic processes. Their small size and high activity levels contribute to their increased heat production. Cats, humans, and elephants have lower metabolic rates and larger body sizes, resulting in lower heat production per unit of body weight.

The visual system integrates stimuli over time, which means it takes longer to process information. However, this slower processing allows for a higher level of sensitivity, meaning it can detect and respond to subtle changes or stimuli. This trade-off between speed and sensitivity means that the visual system may not be as quick as other systems, but it is more capable of detecting and analyzing visual information in detail.

Extremely dilute urine is a symptom of diabetes insipidus, a condition characterized by the inability of the kidneys to properly concentrate urine. This occurs due to a deficiency of antidiuretic hormone (ADH) or a resistance to its effects. Diabetes mellitus, on the other hand, is a different condition characterized by high blood sugar levels and is not directly related to the concentration of urine. Drinking too much seawater or having a salty dinner may lead to dehydration and concentrated urine, rather than extremely dilute urine.

Rhodopsin is a light-sensitive protein found in the retina of the eye. When light enters the eye, it interacts with rhodopsin molecules, causing a chemical change in the retinal portion of the protein. This change triggers a series of events that ultimately leads to the generation of electrical signals, which are then transmitted to the brain for visual processing. Therefore, rhodopsin is responsible for capturing the quanta of light that enter the eye and initiating the process of vision.

The magnocellular versus parvocellular distinction was made first with regard to lateral geniculate cells. The lateral geniculate nucleus is a part of the thalamus that receives input from the retina and relays visual information to the primary visual cortex. The magnocellular cells are larger and respond to low spatial frequencies and high temporal frequencies, while the parvocellular cells are smaller and respond to high spatial frequencies and low temporal frequencies. This distinction in the lateral geniculate nucleus helps in processing different aspects of visual information, such as motion and color.

An on-center/off-surround cell is a type of receptive field found in the visual system. It is characterized by having a central region that is excited by light and a surrounding region that is inhibited by light. In this case, the correct answer suggests that the cell responds most strongly when the entire center is illuminated. This means that the cell is maximally activated when light is present in the central region and there is no inhibition from the surrounding region.

The correct answer describes the complete androgen insensitivity phenotype in an XY adult human as having testes, labia, and clitoris. This condition occurs when an individual with XY chromosomes is unable to respond to androgens, which are male sex hormones. As a result, the individual's external genitalia develop in a female-like manner, with testes instead of ovaries, and the presence of labia and clitoris.

Injecting PYY (3-36) into rats causes them to eat less. PYY (3-36) is a peptide hormone that is released in the intestine after a meal. It signals to the brain that the body is full and suppresses appetite. Therefore, injecting PYY (3-36) into rats would mimic the effects of a full stomach, leading to a decrease in their food intake.

5-alpha-reductase is an enzyme that is necessary for the development of external genitalia in normal males. It converts testosterone into dihydrotestosterone (DHT), which is a more potent androgen. DHT is responsible for the masculinization of the external genitalia during fetal development. Without 5-alpha-reductase, the external genitalia may not develop properly, leading to ambiguous or female genitalia in individuals who are genetically male. The enzyme is not directly involved in the development of gonads, Wolffian ducts, or testes.

Altricial refers to animals that are born in a relatively undeveloped state and require significant care and nurturing from their parents or caregivers. This term is used to describe species such as birds, rodents, and some mammals, whose young are born hairless, blind, and helpless. These animals rely on their parents for food, protection, and warmth until they are able to fend for themselves.

Redundancy is a primary tenet of homeostasis because it refers to the presence of multiple systems or processes that can perform the same function in the body. This redundancy ensures that even if one system fails or is compromised, there are backup mechanisms in place to maintain stability and balance within the body. This principle is essential for the body to adapt and respond to changes in the internal and external environment, allowing it to maintain a steady state and ensure overall health and well-being.

The spatial frequency of a visual stimulus array refers to the number of changes in intensity per unit of visual angle. This means that it measures how rapidly the intensity of the visual stimulus changes as we move our eyes across it. The higher the spatial frequency, the more changes in intensity per unit of visual angle, indicating a more detailed or complex visual stimulus.

Angiotensin II is the correct answer because it is a hormone that plays a crucial role in regulating water balance when there is a decrease in blood volume (hypovolemia). Angiotensin II acts on the kidneys to promote water reabsorption, which helps to conserve water and maintain homeostasis. Additionally, it stimulates the release of vasopressin, another hormone involved in regulating water balance and promoting thirst. Corticosterone, renin, and vasopressin are not directly responsible for inducing drinking in response to hypovolemia.

Cephalopod eyes do not have a blind spot, unlike human eyes. A blind spot is an area on the retina where the optic nerve exits the eye, resulting in no light-sensitive cells. This blind spot is absent in cephalopod eyes, allowing them to have a more complete field of vision without any gaps or missing information.

Female rat pups are masculinized when administered with both estrogens and androgens. However, normal females are not masculinized by their own estrogen secretion. This is because they have a circulating estrogen-binding protein, which binds to the estrogen and prevents it from masculinizing the female rat pups. This protein acts as a protective mechanism to maintain the normal female characteristics in adult females.

Leptin is a hormone that regulates energy balance by inhibiting appetite. In this context, it inhibits the secretion of agouti-related peptide (AgRP), which is an endogenous antagonist of melanocortin receptors. AgRP is known to stimulate appetite and promote food intake. Therefore, by inhibiting the secretion of AgRP, leptin indirectly reduces appetite and helps regulate energy balance.

The development of masculine external genitalia is not guaranteed by any of the options given. While the XY chromosome pattern and the secretion of androgens play important roles in the development of male characteristics, they are not the sole factors responsible for the development of masculine external genitalia. The development of external genitalia is influenced by a complex interplay of genetic, hormonal, and environmental factors. The Wolffian duct system, which gives rise to the internal male reproductive organs, is also not solely responsible for the development of external genitalia. Therefore, none of the options provided can guarantee the development of masculine external genitalia.