Essay questions and responses on academic topics

Biopsychology

Nature and nature psychology explains the behavior of man and the origin of individual differences and their personalities. Nature and nature theories explain the origin of individual differences and type development of personality. In the history of developmental psychology, heredity- environment issue has been identified as the central touchstone of theoretical differences between nature and nurture. Darwin's theory of evolution has impact on notions of human origin and their abilities. In this theory the environment does the selecting on organisms and not vice versa; natural selection dictates that organisms will survive best in the environments they find themselves. Nature- nurture discussions imply that Darwin's evolutionary theory is nature driven, while it contains an interaction of both nature and nurture. Galton (a psychologist) uses twins in his studies to differentiate between nature and nurture. The study shows that twins had little variation on their similarities despite exposure to different environments. He reaches a conclusion that nature prevails over nature; this leaves one wondering whether nurture has any impact at all.

Alfred Binet, in his studies reaches a conclusion that ability and intelligence can be measured using tests of such characteristics like; comprehension and judgment, adaptability and reasoning, not sensory acuity or reaction time.Binet uses many translators and adopters, and his theory is more environmental than Galton's. Binet also protests the idea that intelligence is a fixed quantity and argues that fixed quantities are hereditary determined. The controversy is seen to be the methods of intelligence testing and testing of behavioral differences, some argue that they are influenced by the environment (nature); others argue that these traits are influenced by nurture hence should be measured or tested using nurture. The controversy is also about methodological development and whether nature or nurture is involved to determine human differences. Evolutionary biology is a historical science that seeks to reconstruct the past. It talks about evolutionary changes that occurred in the past that led to current organisms. Evolutionary psychology uses evolutionary biology which is an historical reconstruction to explain how minds and brain works.

Question two

Whenever nerve cells are activated and produce a nerve impulse, the impulse causes the release of neurotransmitters molecules in the tiny space between nerve cells (synapses), referred to as conduction transmission. With a cell stimuli, molecules called ligands are produced to activate the receptors, which include; neurotransmitters, hormones, and acetylcholine. Electro potential exchange is then stimulated via cell membranes during initial state of cell's rest. This change is referred to as action potential, which converts to nerve impulse that spreads throughout the body cells and eventually to the axon. Presynaptic neuron is involves in releasing neurotransmitters, while postsynaptic neuron aids in receiving postsynaptic neurotransmitters. When the action potential reaches the synapse, exocytosis is released near the edge of pre-synaptic membrane where the vesicles that store neurotransmitters lie. Cytosol initiates cell depolarization that aids in passage of calcium ions from outside. This allows fusion of synaptic vesicles with plasma membrane and aid in response for triggered stimuli.

Electrical transmission of impulses in the body involves body cells and takes a short period of time. The cells are connected by a protein channel that aid in presynaptic and postsynaptic transmission of impulse. When action potential is propagated into the cell axon, it enable sodium ions passage into the cell membrane due to the potential difference that exist between the cytoplasm, which consist of potassium ions, and membrane causing cell depolarization. Surrounding cells become lowly concentrated as compared to depolarized cell, and in turn, ions become permeable too to the polarized cells and end up becoming depolarized. This aids in transmission of impulse via the cells.

Question three

The nature of Visual stimuli comprises of the fact that it is only sensitive to minuscule fraction of the electromagnetic spectrum. The spectrum is called protons which have a wavelength of between 400-700nm. This spectral range is driven by the spectrum of sunlight at the earth's surface which is 550nm. Visual perception ranges from a few tens of protons at the surface of the retina to a billion or more. This enormous range of responsiveness allows the visual system to generate perception in varying circumstances during the day and at night. To function over such a wide range, the visual system has sensory systems, which resets the sensitivity according to ambient conditions. Visual acuity is one of the most important functions of the eye; this is being able to differentiate different objects. Light travels from the outside world to the eye; it strikes the retina and through nerve impulses transmits it along visual pathways to the visual cortex. Cornea sharpens the image and accounts for the focusing power of the eye but it cannot change the shape of objects. To focus far and distant objects, the lens is made thicker and thinner; it is flattened by suspensory ligaments to focus objects and rounded to bring near objects to focus.

Retina contains two types of photoreceptor cells; rods and cones. There are more rods than cones, although the area around fovea has more cones. Rods have the same pigment (rhodopsin), and cones have three different types depending on the color. Rods and cones convert light energy to neural impulses; rods are responsive to dim light but are not useful in bright light. Cones are active when it is bright and less active in dim light; we also depend on cones in color vision. Retina is inside out and light must travel through two layers of cells before reaching the rods and cones. These receptors send their input to the bipolar cells, which in turn transmit their messages to ganglion cells. Ganglion cells loop around and exit from the eye at the blind spot. Ganglion cells input from one or more cones; they convert light to energy for transmission to the brain. Axon and ganglion cells make up the optic nerve. The occipital lobeis the final pathway where images from both eyes are mixed and binocular vision is created. Trichromatic theory suggests that color is viewed due to the different absorption of cone pigments. The different absorption differs due to amount of amino acids and opsins in the receptor. Opponent process also suggests that color vision is about processing cones and rods in an antagonistic manner.

Question four

Transgenic animals are animals that have had their DNA manipulated to possess and express an extra foreign gene. Their uses are especially to study diseases, study normal psychology and development, biological products, vaccine safety, chemical safety testing, and transplantation.

Question five

Medial forebrain bundle is one of the major fibers, located at the lateral hypothalamus that joins the telencephalonand the mencephalon which aids in the input of the hypothalamus. The fibers in medial forebrain bundle traverse the lateral preoptic area to terminate in the dorsomedial nucleus of the thalamus.

Question six

Monoamine theory of depression n holds that depression results from pathologically decreasedserotonin or norepinephrine neurotransmission. Based on the theory, it follows that increasing norepinephrine or serotonin neurotransmission could reverse depression. As a biological disease related to long-term pathological alterations, in monoamine activity, MDD should be treatable by medications. Antidepressant medications increased the level of monoamine neurotransmitters in the synaptic cleft. According to scientists, the fact that monoamine transmitters play a central role in the biochemistry of depression; low levels of norepinephrine, serotonin and dopamine in the cleft are responsible for the symptoms of depression.

This theory is supported by the study of depressed individuals, who have low levels of serotonin in the cerebrospinal fluid and brain parenchyma. Monoamines rise immediately after medication, although medications take four to six weeks to be effective; this implies that effectiveness of medications use other mechanisms. It is widely accepted that nor epinephrine, serotonin and dopamine play an important role in depression although the role is yet to be fully determined. The time lag in clinical effectiveness of antidepressants reflects auto regulatory mechanisms affecting presynaptic moaminergic neurons, or other changes in postsynaptic neural circuitry. Chronic use of antidepressants cause inhibitory auto receptors to be down regulated leading to enhanced neurotransmission. Change of auto receptor sensitivity takes several weeks, consistent with time-course of the therapeutic response in patients. This explains the delayed onset of therapeutic response; after chronic antidepressant therapy is when gradual desensitization of auto receptors allows increased neurotransmission. The hypothesis on changes in monoamine receptor sensitivity offers the explanation for the delay of onset of therapeuticaction.

Question seven

Lateral hypothalamus (LH) is a switch for hunger because when LH is destroyed in rats, as a result the rat stops eating, loses weight and eventually dies. Ventromedial hypothalamus (VHM) plays a role for creating a feeling of satiety, or lack of hunger. When VMH is destroyed in rats, the rats will eat continuously and grow fat until they eventually die. Satiety is not only due to VMH action, because it is also believed that VMH is indirectly involved in satiety. Destruction of VMH will cause disturbance to the autonomic nervous' system control over the release of insulin. This results into increased release of insulin in the bloodstream which produces great hunger, increased eating and obesity. Loss of VMH does not remove satiety center but, rather cause disturbances in the nervous system that causes increased eating and fat storage. Hunger regulation in the brain depends on the intricate communication among several different brain structures. There does not seem to be a single switch for hunger regulator, rather hunger seems to be regulated by a complex network of feedback to the brain from various sources in the body as well as by direct signaling in the brain. Anorexia nervosa entails starvation at will, and primarily occurs to patients at puberty. Studies show that specific reduction of ACC, the proposed output of the motor output of the emotional brain or may not recover with weight gain to the normal. There is also a consistent reduction in blood flow in the limbic structures in young anorexic patients.

Question eight

The upper motor control comprises the motor of the cerebral cortex. These areas are responsible for initiation of voluntary muscles activity and can dominate the lower motor neurons arising from the brain stems and the spinal cord either via the direct descending pathways (pyramidal system) or the indirect descending pathways (extrapyramidal system). Pyramidal system consists of majority of the direct connections between the motor areas of the cerebral cortex and the lower motor neurons pass through the pyramids of medulla oblongata. Extrapyramidal consists of indirect motor pathways which involve its connection with subcortical structures, and particularly with the basal ganglia. The primary function of extrapyramidaland pyramidal systems are for fine tuning of voluntary movements to render it amenable to higher levels of conscious control.

Cerebellum and cerebral cortex aids in the co-ordination of body movement. Both of the organs consist of several cells that aid in reception and transmission of movement stimuli. Cerebellum consists of cell inputs that carry information from spinal cord about the ongoing movements in all different parts of the body, but also information from different motor centers about a planned movement even before a movement has been executed. Cerebellum interacts with cerebral cortex practically, and this enables the cerebellum to be updated on body movements that are made and yet to be made in the future. This interaction also ensures volitional command for movement sequences produce the most efficient and coordinated result while still maintaining the appropriate posture. Limbic and hypothalamus initiate the movement, and the two structures lie beneath the cerebral cortex. Stimulus from this region activates the region of cerebral cortex (association area) which generates sequence to permit patterns of movements. Signals are then sent to cerebellum, that aids movement, and basal ganglia which create movement templates that provide postural compensation when the movement begins.

Question nine

Perception of color involves cones sensitive to blue, red and yellow and opponent color systems. Color sensitive, ganglion cells; detect red-green and yellow blue pairs of colors. The three types of cones found in the eyes, each has different sensitivity to wavelengths. Cells in the retina, thalamus and cortex respond differently to different colors. The cone sensitive to short wavelength of light blue, this different sensitivity helps the brain knows the color the cone is corresponding to. The rods and cons found in the eyes cause different color perceptions according to different wavelengths. Variations are caused by different physical and psychological factors. Herring suggested that color sensitive visual elements are arranged into three kinds of pairs that the members of each pair and the members of each pair oppose, or inhibit each other. Each element signals one color or the other (red or green blue or yellow, black or white).This theory explains color afterimages. When one member or an opponent pair is no longer stimulated, the other is activated.