Neuroscience PDF

**[Neuroscience]** [Central nervous system:] The central nervous system (CNS) is a crucial part of the body\'s nervous system, responsible for integrating and processing information. It consists of two main components: - Brain: The control centre of the body, responsible for processing sens...

**[Neuroscience]** [Central nervous system:] The central nervous system (CNS) is a crucial part of the body\'s nervous system, responsible for integrating and processing information. It consists of two main components: - Brain: The control centre of the body, responsible for processing sensory information, regulating bodily functions, controlling movement, and governing cognitive processes such as thought, memory, emotions, and reasoning. - Spinal Cord: A long, tubular structure that runs down the spine, acting as a communication highway between the brain and the rest of the body. It relays messages between the brain and peripheral nervous system and plays a role in reflexes. [Peripheral nervous system:] **Somatic nervous system** receives and transmits information from the senses or to the muscles - Sensory nerves (sensation) - Motor nerves (muscle contraction) - Via the spine (spinal nerves) - Or brainstem (cranial nerves) **Autonomic nervous system** maintains essential bodily functions largely without conscious control - Breathing - Pupil dilation - Sexual arousal - Swallowing - Digestion - Two parts: 1. Sympathetic: fight or flight 2. Parasympathetic: rest and digest [Neuron:] - Fundamental unit of the nervous system - Consists of: - Cell body (metabolism of cell) - Axon (typically myelin covered fibre through which electrical impulses are transmitted and converted into chemical signals) - Dendrite (tree like fibres which receive neurotransmitters as communication from other cells) - Many types of neurons through the nervous system, each with a specialised task (e.g., multipolar neurons, pyramidal neuron, bipolar neuron) [Communication:] - The electrical signal is called an action potential - Propagated down the axon due to electricity charged particles called ions that flow through ion channels in the axon membrane Negative concentration gradient = more positive ions outside than inside the cell Unequal distribution of different ions causes the inside of the axon to be relatively negatively charged (K+, Potassium = Negative, NA+, Sodium = positive) - At rest, voltage-gated sodium and potassium channels are closed - Action potential is a temporary shift in the membrane potential (from negative to positive) - Signals from other neurons allow positive ions to flow into the cell and depolarise the membrane (Depolarisation = more positive) - When one channel opens and allows positive ions in, it depolarises the surrounding axon - Voltage-gated channels open and the change in membrane potential passes down the axon -- an action potential [Communication between neurons: ] - When an action potential reaches the axon terminal it needs to pass on the signal to the next cell - Neurons communicate with each other via synapses -- the place where the neurons meet - Action potential triggers a release of neurotransmitters into the synaptic cleft - Neurotransmitters are picked up by receptors which can affect the functioning of the receiving neuron - Receptors are neurotransmitter specific and can only be activated by that neurotransmitter or a chemical which fully or partially mimics it [Synapse:] - When postsynaptic receptors are activated, they open ion channels to allow in specific ions - Change the charge inside the receiving neuron and likelihood of a new action potential - Free neurotransmitters in the synapse are either broken down by the enzymes or reabsorbed by the axon terminal by reuptake proteins [Drug Action:] - This can explain how many drugs work at the level of cell biology - Selective serotonin reuptake inhibitors (SSRIs like fluoxetine aka Prozac) prevent the reuptake of neurotransmitter serotonin - Meaning more stays in the synaptic cleft so there is more free serotonin and so serotonin receptors are more frequently activated - Other drugs mimic neurotransmitters and trigger neurotransmitters specific receptors (agonism) - Some block receptors (antagonism) - Some act directly on ion channels some affect the enzymes or proteins that "clear up" free neurotransmitters - Because of the different use of specific neurotransmitters and receptors in the brains systems to varying degrees of drugs can selectively affect specific circuits, behaviours, and perceptual systems [Many Biological Factors:] - However, anything that can affect the function of the nervous system has the potential to affect us - Proteins are the workhorses of biology and can be subject to many forms of change, alteration and dysfunction (e.g., Alzheimer's disease) - Generation and regeneration of key cells (during neurodevelopment and through stem cell therapy) - Virtually any aspect of cell metabolism - Larger scale aspects of the body's metabolism and signalling can also have an impact on the nervous system in the short and long-term - Oxygen - Glucose - Hormones - Nutrients [Lobes: ] - Frontal lobe - Parietal lobe - Occipital lobe [Neuroanatomy:] - Grey matter (cell bodies -- traditionally the brain's computation) - White matter (axons -- traditionally the brain's cabling) - Myelination of axons (fatty tissue) produces the white colour (multiple sclerosis due to damage to myelin [Cortex:] - Outer layers of grey matter in the brain - Folded to allow for a large surface area - More involved in higher cognitive functions related to deliberate action - Microstructure (cytoarchitecture) varies across brain [Subcortical Structures:] - Cerebral cortex - Basal ganglia - Thalamus - Hippocampus - Amygdala - Hypothalamus [The brain is a network of networks ] - Even if two brain areas are not directly connected through white matter tracts activity can be passed on - Meaning all brain areas can be functionally connected - Something similar happens in cities - E.g., although there is no direct transport link between Brixton and Barnet. You can travel between them [Network Change:] - Changes in structure and/or function of these networks are what determines how the brain learns, adapts, and changes - One key aspect is neuroplasticity [Neuroplasticity:] Many different types: - Synaptic plasticity refers to changes in the strength of connections between synapses 1. Increased NT release 2. Increased NT binding 3. Both alter the number of ions entering the neuron and the electrical current to trigger an action potential - Synaptogenesis and synaptic pruning refer to the creation and removal of synapses - Neurogenesis is the creation of new neurons, a limited ability in the human brain - Neuronal migration is the process where neurons extend from their "place of birth" to connect to far reaching areas across the brain - Neural cell death is where neurons die. Can happen through damage, over-excitation, or disease, but also as a natural "programmed" death called apoptosis - Functional reorganisation is where functions of the brain are redistributed to other areas - For example, the primary visual cortex is active when blind people read braille - Also, practice is associated with a reduction in brain activity and reduced distribution of brain activity over time [Neuroscience methods:] - Direct interventional studies typically alter something about brain function and examine the result - For example, drugs, lesions, genetic changes or electrical simulation - Lesions and genetic changes may be introduced (animals) or studied in naturally occurring or secondary effect situations (humans with specific syndromes, after accidents or surgery) [Methods:] - Measurements can involve direct examination of brain tissue, its functioning, or metabolites (in vivo or post-mortem measures) - Indirect examination of tissue, functioning or metabolites (neuroimaging) - Testing behaviour, task performance, experience, or association with other features (e.g., symptoms) [How closely does cognition fit anatomy ] - Although you hear a lot of discussion about the "brain area for x" (like the hippocampus is the brain area for memory)...this is misleading - Brain areas can be preferentially involved in certain functions, but none are dedicated for specific functions [Levels of Explanation:] - It is often more helpful to think of different approaches from the social to the biological as using different levels of explanation - This also helps avoid the error of trying to classify disorders or problems as "social" or "biological" as if they were mutually exclusive - Instead, we can think of social. Psychological, cognitive, biological approaches as different tools for helping us understand the problem [Disciplines:] - In practice, there is a great deal of overlap and there are many "neuro" disciplines with slightly different emphasis but confusingly similar names - E.g., computational neuroscience, cognitive neuropsychiatry, neuropsychopharmacology, psychobiology, cognitive neuropsychology etc., [Neurobiology:] - Deals with the nervous system and its interactions at the molecular and cellular level - May be interested in understanding the complexities of - Neuronal signalling - Cell physiology - Genetics and gene expression - Interventions and pathologies (natural/artificial) [Systems Neuroscience:] - The study of neural networks - From small groups of interconnected neurons to larger scale circuits in the brain [Psychopharmacology:] - Studies the neurobiology of substances that alter the mental state - This can include: - Medications (e.g., antipsychotics) - Common drugs (e.g., caffeine, nicotine) - Street drugs (MDMA, LSD) - Industrial chemicals (e.g., toluene) [Neuropsychology:] - Looks at how the structure and function of the brain related to how we think, feel, and behave - Based on standardised tests and experimental tasks that are known to reflect the function of specific brain mechanisms - Typically conceptualises the brains work, cognition, as information processing [Cognitive Neuroscience: ] - Looks at the neural correlates of thoughts, emotions, and behaviours by measuring brain function - Usually with neuroimaging but increasingly with interventions like transcranial magnetic stimulation of TMS [Computational Neuroscience:] - Builds computer models of brain functions at various levels of abstraction to test ideas and theories