msalvucci's blog

Drugs affect the brain in various ways depending on the classification of the drug. Four main categories of drugs are depressants, narcotics, stimulants and hallucinogens. Depressants have certain effects on the brain and include tranquilizers, sedatives and hypnotics. Believe it or not, alcohol is a depressant. These drugs slow down brain functions and can lead to slower reflexes and coordination. They also decrease the flight response of the sympathetic nervous system. Not only do these drugs also interfere with self-awareness, but they affect memory as well. It is very dangerous to drive when taking a depressant such as alcohol due to the decrease in motor control and coordination. Additionally, due to the decrease in self-awareness, alcohol can be highly addictive for their relaxing characteristics. As for narcotics, they include morphine, heroin and fentanyl. These drugs are anti-anxiety drugs meaning they increase relaxation and drowsiness. They are used for pain reduction; they are commonly given to patients after surgical procedures. Narcotics unfortunately slow down physical activity and speech. When they wear off, they can induce extreme anxiety causing a desire for more of the drug to calm them down. 

Nastic movements are important mechanisms in plants that act as defense against herbivory, blah blah. A nastic movement in the Mimosa pudica plant, or sensitive plant, is thigmonasty. This mechanosensory response is stimulated by touch or movement of the plant and causes the plant leaves to collapse on themselves. In order to understand how nastic movements are affected by its surroundings, this experiements will test thigmonasty in Mimosa pudica plants under 5 difference conditions. Four of the environments will have varying amounts of water and sunlight given to the plants during its growth period to understand how irregular conditions affect the nastic movements. A fifth environment will test the nastic movements of the plants under normal growing conditions. The nastic movements will be observed by timing the response closure time and reopening time of the leaves after touching the leaves with a cotton swab. Following data collection of each time interval ten times, overlapping graphs will be made to easily identified how the nastic movements times have been affected by each irregular environment compared to the control group.

Thigmonasty is caused by a change in the turgor pressure within Mimosa pudica leaves. Turgor pressure is defined as the force against the cell walls of the plant that is created by the water within the cell contents. This pressure is responsible for keeping the leaves standing up under normal conditions. When this plant is touched, the mechanosensory response begins by activating the contractile proteins in the base of the leaf. These proteins allow the water within the cell to slowly diffuse out which decreases the turgor pressure in the plant and therefore causes the leaves to collapse. Once one single leaf is touched, the adjacent leaves on the branch get stimulated by the motion of the first leaf and close as well. With the lack or excess of water in heat within the 4 environments, the turgor pressure in these leaves may be altered. Through understanding how thigmonasty takes place in Mimosa pudica plants, one can infer how changes in the surrounding environment might affect the plant's nastics movements.

Four conditions will include variations in the amounts of water and heat given to the plant during the growth period. A fifth environment will supply the normal levels of heat and water to the Mimosa pudica, thus, acting as a control group. Prior to creating these environments, we will research the physiology of Mimosa pudica to understand the how much sunlight and water is needed for these plants to grow under normal conditions. Growing Mimosa pudica under various extreme conditions will allow us to test the plant’s abilities to perform nastic movements. Under low water conditions, Mimosa Pudica plants may not produce enough turgor pressure to create a nastic movement when stimulated. It is unknown how the variations in sunlight will affect the plant nastic movements.

Thigmonasty is caused by the change in the turgor pressure within Mimosa pudica leaves. Turgor pressure is the force against the cell wall of the plant that is created by the water within the cell contents. This pressure keeps the leaves standing up in normal conditions. When this plant is touched, the mechanosensory response begins by activating the contractile proteins in the base of the leaf. These proteins allow the water within the cell to slowly diffuse out, decreasing the turgor pressure in the plant and therefore causing the leaves to collapse. Once one single leaf is touched, the other leaves on the branch become stimulated by the motion of the first leaf and close as well. With the lack or excess of water in heat within the 4 environments, the turgor pressure in these leaves may be altered. This may cause the thigmonasty response to be altered in these plants.

Each plant’s nastic movement will be tested and timed 10(?) times by the same person to keep the data uniform. Each time will be recorded and organized into a data table. The average nastic movement time for each environment, including the control group, will be compared. This will be represented in a graph showing all 5 of the environment data averages. This will allow us to compare the data points to eachother in a conclusive graph.

(more on this)

SIGNIFICANCE:

The goal of this study is to understand how environmental factors affect thigmonasty of the Mimosa Pudica species. There is little know about the nastic movements in Mimosa Pudica in undesirable environments, so this project will give new insight to this topic of plant movement. Thignomasty in plants may be used as a defense mechanism so it is important to understand when plants can use this movement against certain stimuli to defend themselves.

The neurons in the human body are constantly moving and firing signals at all times. When a neuron is stimulated, it fires an impulse to its neighboring neurons. The nerve impulse is called the action potential. Within the body, ions both positive and negative are floating around constantly. Certain areas are more negatively charged, while others are more positively charged. These charges can indicate an action potential. The action potential works when the ions inside and outside of the cell fluctuate. The membrane potential, or difference between the positive and negative areas, can cause the event that triggers the flow of ions across a membrane. A resting neuron is typically negative on the inside of the cell and this resting membrane potential lays at -70 millivolts. The positive sodium ions outside of the membrane and positive potassium ions inside the cell work together in the sodium potassium pump. For every 2 potassium ions that float into the cell, 3 sodium ions are pumped out of the cell. Ion channels are then opened when the membrane potential reaches -55 millivolts. When these channels open, the ions move in and out of the cell depending on the chemical gradient. When a stimulus occurs, the increase in positive ions make the membrane potential exceed -55 millivolts. The resting neuron becomes depolarized, and lets a lot of sodium rush into the cell which creates an action potential. This action potential then flows down the axon of the neuron, and the stimulus occurs. However, when the potassium channels open, the voltage tries to equal out in the cell, and the action potential degrades. This is called the hyperpolarization; the voltage drops to -75 millivolts.

A scientist by the name of Julian Rotter observed that individuals differ in their understanding of why things happen to them. The concept of fate is controversial as some believe that they should feel lucky for things that happen to them, rather than take credit for it. Rotter theorized that individuals who blame luck or a higher being as the reason things happen to them fall under the category of ‘external locus of control’. On the other hand, individuals who believe that they are their own driving force behind what happens to them, meaning they take credit for their choices, are a part of the category of ‘internal locus of control’. Rotter argued that believing or not believing in fate is a fundamental characteristic that can tell a lot about a person’s soul. Reinforcement from rewarded behavior shapes young kid’s understandings that they control their own future; they make choices to act a certain way or do a certain task that will eventually help them reach their end goal. This decreases the chance that kids will grow up to believe that the future is in the hands of fate, or a higher being. Rotter proposed multiple methods for testing whether an individual possesses the internal or external locus of control. He believed that people who had the internal locus of control would be more motivated to make good things happen for them, therefore, they would be more successful in life. The opposite goes for individuals with external locus of control because they would not feel the need to try hard in life to be successful as their fate is in the hands of a higher power. This idea relates to many aspects of society including socioeconomics. These are related as people of higher socioeconomic standings were most likely possessing an internal locus of control.  

There is a relationship between the length of a muscle fiber and the tension of a muscle fiber. It is known that the shorter the muscle fiber, the less force they exert. This can be seen by a demonstration using your wrists and hands. If one flexed their hand downward so that the hand is perpendicular to the wrist, less force will be exerted when they try to grab another finger tightly with the hand in this position. However, with the hand normally extended, the hand can tightly grasp another finger with full force. This is due to the idea that muscles have an ‘optimal’ length. This optimal length is identified as the length that it most useful for exerting forces. The length of the muscle when in a normal position is optimal to allow the hand to grasp a small object, while the flexed position is not optimal. For example, if the thick and thin filaments in a sarcomere are further apart, there is a decreased number of motor proteins that can pull on the thin filaments to move inward. Therefore, the lower amount of touching motor proteins lowers the force that it able to be exerted on another object. This is also due the crossbridge cycle. The closer the thin and thick filaments are to eachother, the lower amount the muscle will be able to contract with the restriction of the crossbridge cycle. 

Muscle is the body’s motor because it converts chemical energy into mechanical energy. This means that the ATP that is synthesized through reactions in the body are used as energy to drive mechanical force of muscles and movement. Within skeletal muscle, there are muscle fascicles containing muscle fibers that generate movement. The muscle fibers are cells that have their own plasma membrane as well as multiple nuclei. The muscle fibers are separated by the endomysium while the muscle fascicles are separated by the perimysium tissue. It is important to know that the skeletal muscle is connected to bone by collagen fibers in the epimysium, endomysium and perimysium interwoven with collagen fibers in the periosteum and bone tissue. These connections are usually made are the origin of the muscle. Muscles contract and generate movement by cross bridge cycles of the thick and thin filaments. The thick filament has motor proteins called myosin that grab onto the thin filament and drag them closer together. This shortening is the muscle contraction. The thin filaments are composed of mostly actin and regulatory proteins: tropomyosin and troponin. Although these names sound similar, they perform very different functions which will be summarized in another class period. The signal for the contraction of the muscle is the calcium ion.