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Psychology

What is an MRI in psychology?

Magnetic Resonance Imaging (MRI) is a brain imaging technique that uses strong magnetic fields, radio waves, and a computer to produce detailed 2D or 3D images of brain structure, which can then be analysed by a trained professional. This method allows researchers to explore how differences or changes in brain structure may be linked to changes in behaviour, and vice versa. One strength of MRI is that it is safe and non-invasive, allowing repeated scans to be conducted without exposing participants to harmful radiation. This makes it useful for studying long-term changes in the brain. However, a limitation is that MRI only provides structural information, not data about brain activity. It is also expensive and requires participants to remain very still during the scan, which can be challenging for certain groups and may limit its accessibility in some research contexts. In psychology, researchers use MRI to study how the brain develops from childhood to adulthood, helping them understand typical brain maturation and how it relates to behaviour and cognitive abilities. MRI is also used to show neuroplasticity, revealing how the brain physically changes in response to learning and experience.

Chemistry

Why does electronegativity increase across and up the periodic table?

Electronegativity increases across a period (left to right) and up a group because of the combined effects of atomic size and effective nuclear charge. Electronegativity is the ability of an atom to attract the shared pair of electrons in a covalent bond. As you move across a period, the number of protons increases while electrons are being added to the same shell, resulting in a higher effective nuclear charge, which is the net positive charge experienced by valence electrons after accounting for shielding. Since the shielding remains relatively constant across a period (same number of inner shells), the increased nuclear charge pulls the valence electrons more tightly, making the atom smaller and better able to attract bonding electrons. This is why fluorine, at the far right of Period 2, is more electronegative than carbon or nitrogen in the same period. Moving up a group, electronegativity increases primarily due to decreasing atomic size. As you go up a group, there are fewer electron shells between the nucleus and the bonding electrons. For example, fluorine (Period 2) has only two electron shells while iodine (Period 5) has five. When atoms form covalent bonds, the shared electrons in smaller atoms are much closer to the nucleus and experience a stronger electrostatic attraction, despite the smaller number of protons. The effect of decreasing distance outweighs the effect of decreasing nuclear charge as you move up a group. These two trends combine to make fluorine, located in the upper right of the periodic table, the most electronegative element with a value of 4.0, while francium in the lower left would be the least electronegative. The only exception to the trend is the noble gases, which typically don't form bonds and therefore don't have standard electronegativity values.

Physics

What determines gravitational pull?

Gravitational pull, otherwise known as the force of gravity, acts between all objects due to their mass. Around any individual mass there exists a gravitational field that will cause any other mass placed within it to be attracted to the original mass. The gravitational field strength is represented by the symbol $g$ and has units of N kg$^{-1}$. The gravitational pull on an object depends on its mass m and the strength of the gravitational field that it is in. The formula for the gravitational force $F_g$ is $\hspace{3em} F_g = mg$ The gravitational pull between two masses can also be found using Newton’s Universal Law of Gravitation. This law shows that the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to their separation distance. $\hspace{3em} F_g = G\dfrac{m_1m_2}{r^2}$ Where: $\hspace{2em}F_g$ is the force of gravity in units of N \ $\hspace{2em}G$ is the gravitational constant 6.67 x 10$^{-11}$ N m$^2$ kg$^{-1}$\ $\hspace{2em}m_1$ and $m_2$ are the masses of the two objects in units of kg\ $\hspace{2em}r$ is the separation of their centres of mass in units of m

Economics

What are non-price determinants in economics?

Psychology

What is a synapse in psychology?

The synapse is the junction between two neurons and includes all the components necessary for neural communication within the nervous system. It consists of the terminal sacs (or vesicles) located at the axon terminal of the presynaptic neuron, the synaptic gap (or cleft) between the neurons, and the receptor sites on the dendrites of the postsynaptic neuron. When a neurotransmitter (a chemical messenger) is released from the terminal sacs of the presynaptic neuron, it crosses the synaptic gap and binds with complementary receptors on the postsynaptic neuron. These neurotransmitters can either stimulate or inhibit the activity of the postsynaptic neuron. In doing so, neurotransmission can influence human behaviour. Whether a neurotransmitter has an excitatory or inhibitory effect depends on the type of neurotransmitter and the specific receptors involved in the synapse.

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