Describe the structure of a neuron and explain the function of each of its major parts.
Explain the interaction between the central nervous system and peripheral nervous system.
If the corpus callosum is severed, how might this affect the way that we perceive the world?
How might modern brain imaging techniques be useful to psychologists?
Explain at least one potential implication for the genetic diagnosis of traits such as intelligence and criminality.
Briefly explain Freud's theory of dreams.
Explain the difference between absolute threshold and difference threshold.
Explain, in detail, the process of vision.
Describe the Gestalt principles of proximity, similarity, continuity, and closure.
Explain, in detail, the process of vision.
Describe the Gestalt principles of proximity, similarity, continuity, and closure.
**Structure of a Neuron:**
Neurons are the fundamental units of the brain and nervous system, responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between. Key parts of a neuron include:
- **Dendrites:** These tree-like structures receive chemical signals from the axons of other neurons and convert these signals into electrical impulses that travel towards the cell body.
- **Soma (Cell Body):** This contains the neuron's nucleus and other organelles. It processes the received signals and determines if the neuron will activate an electrical impulse.
- **Axon:** A long fiber that extends from the soma, the axon transmits the electrical impulse, known as the action potential, away from the cell body.
- **Myelin Sheath:** This fatty layer insulates the axon in segments and increases the speed of electrical transmission along the axon.
- **Nodes of Ranvier:** These are the gaps between myelin sheath segments where the action potentials are regenerated to maintain their strength over long distances.
- **Axon Terminals (Synaptic Terminals or Boutons):** The ends of the axon, which release neurotransmitters into the synaptic cleft (the gap between neurons) to communicate with other neurons.
**Interaction between the Central Nervous System (CNS) and Peripheral Nervous System (PNS):**
The CNS consists of the brain and spinal cord and is where information is processed and responses are generated. The PNS includes all the nerves that lie outside the CNS and is divided into the somatic nervous system, which controls voluntary movements and transmits sensory information, and the autonomic nervous system, which controls involuntary bodily functions.
The CNS receives sensory information from the PNS, processes it, and then sends out commands to the PNS for action. The PNS, in turn, carries out these commands by activating muscles or changing operational modes of organs.
**Effects of Severing the Corpus Callosum:**
The corpus callosum is a massive bundle of nerve fibers that connects the left and right hemispheres of the brain, allowing for communication between the two sides. If the corpus callosum is severed, a condition known as split-brain, the communication is disrupted. This can lead to symptoms such as the inability to name objects that are processed by the right hemisphere (since language is often located in the left), difficulties in coordination between the two sides of the body, and challenges in tasks that require integration of both hemispheres.
**Modern Brain Imaging Techniques:**
Modern brain imaging techniques such as fMRI, PET scans, and EEG are immensely useful for psychologists. They allow the visualization of brain activity, structure, and connectivity in real time, which helps in understanding the neural basis of behavior, cognition, and emotion. They also assist in diagnosing and tracking brain diseases, in therapeutic interventions, and in psychological research.
**Genetic Diagnosis of Traits:**
The genetic diagnosis of complex traits such as intelligence and criminality can have significant ethical and social implications. There are concerns about genetic determinism, privacy, and discrimination. For instance, labeling individuals with certain genetic profiles may stigmatize them or restrict their opportunities regardless of their behavior or environmental influences.
**Freud's Theory of Dreams:**
According to Freud, dreams are the royal road to the unconscious mind. He believed that dreams are filled with symbolic representations of unconscious desires and conflicts. He distinguished between the manifest content of a dream (the literal storyline) and the latent content (the underlying, hidden, symbolic meaning). Freud theorized that the ego protects the dreamer from the direct impact of unconscious material by disguising it in symbolic form.
**Absolute Threshold vs. Difference Threshold:**
The absolute threshold is the minimum stimulus intensity that an organism can detect at least 50% of the time. It represents the point at which a stimulus goes from undetectable to detectable.
The difference threshold, or just noticeable difference (JND), is the smallest change in the intensity of a stimulus that a person can detect. It is the minimal difference needed to notice a change between two stimuli.
**Process of Vision:**
The process of vision begins when light enters the eye through the cornea. The cornea and lens focus the light onto the retina, which contains photoreceptor cells (rods and cones). Rods detect light intensity and are crucial for night vision, while cones are responsible for color vision and visual acuity.
The photoreceptors convert light into electrical signals, which are then processed by other retinal neurons (bipolar cells, amacrine cells, and ganglion cells). Ganglion cell axons bundle together to form the optic nerve, which carries visual information to the brain.
In the brain, visual information is processed in the occipital lobe's primary visual cortex and then further analyzed in the visual association areas for recognition and interpretation.
**Gestalt Principles:**
Gestalt principles are laws of perceptual organization proposed by German psychologists in the 1920s. These principles explain how we perceive visual elements as unified wholes rather than just collections of separate parts.
- **Proximity:** Objects that are close to each other are perceived as part of the same group.
- **Similarity:** Elements that are visually similar are perceived as more related than those that are different.
- **Continuity:** Lines and patterns are perceived as continuing in space even when they are interrupted.
- **Closure:** When parts of a whole picture are missing, our perception can fill in the visual gap to create a complete image.
These principles help to explain how we organize visual information into meaningful patterns and objects.