unit 19 review
The nervous system's integrative brain functions are a complex interplay of neural processes that enable cognition, behavior, and bodily regulation. From neurotransmitter signaling to synaptic plasticity, these mechanisms allow the brain to process information, form memories, and control various physiological functions.
Key structures like the cerebral cortex, subcortical regions, and brainstem work together to integrate sensory input, coordinate motor output, and regulate emotions. Understanding these intricate systems is crucial for grasping how the brain functions in health and disease.
Key Concepts and Terminology
- Neurotransmitters chemicals released by neurons to transmit signals across synapses (glutamate, GABA, dopamine, serotonin)
- Synaptic plasticity ability of synapses to strengthen or weaken in response to changes in activity
- Long-term potentiation (LTP) persistent strengthening of synapses based on recent patterns of activity
- Long-term depression (LTD) long-lasting decrease in synaptic strength
- Neurogenesis formation of new neurons from neural stem cells in specific brain regions (hippocampus, olfactory bulb)
- Neuromodulation process by which neurotransmitters and other signaling molecules regulate the excitability and activity of neurons
- Homeostasis maintenance of stable internal conditions in the body through various regulatory mechanisms
- Circadian rhythms 24-hour cycles of physiological processes regulated by the suprachiasmatic nucleus in the hypothalamus
- Neuroimaging techniques used to visualize brain structure and function (MRI, fMRI, PET, EEG)
Brain Structure and Organization
- Cerebral cortex outermost layer of the brain involved in higher-order functions (perception, cognition, motor control)
- Divided into four lobes frontal, parietal, temporal, and occipital
- Organized into functional areas specialized for specific tasks (visual cortex, motor cortex, auditory cortex)
- Subcortical structures located beneath the cerebral cortex (thalamus, hypothalamus, basal ganglia, amygdala, hippocampus)
- Thalamus relay station for sensory and motor information between the cortex and other brain regions
- Hypothalamus regulates homeostasis, endocrine function, and emotional responses
- Brainstem connects the brain to the spinal cord and regulates vital functions (breathing, heart rate, sleep-wake cycles)
- Composed of the midbrain, pons, and medulla oblongata
- Cerebellum coordinates smooth, precise movements and maintains balance and posture
- White matter consists of myelinated axons that transmit signals between different brain regions
- Gray matter contains neuronal cell bodies, dendrites, and synapses involved in information processing
Neurotransmitters and Signaling
- Glutamate primary excitatory neurotransmitter in the brain involved in learning, memory, and synaptic plasticity
- GABA (gamma-aminobutyric acid) main inhibitory neurotransmitter that reduces neuronal excitability and regulates brain activity
- Dopamine involved in reward-seeking behavior, motivation, and motor control
- Dysregulation of dopamine signaling associated with Parkinson's disease and addiction
- Serotonin regulates mood, sleep, appetite, and pain perception
- Selective serotonin reuptake inhibitors (SSRIs) used to treat depression and anxiety disorders
- Acetylcholine involved in attention, learning, and memory formation
- Degeneration of cholinergic neurons associated with Alzheimer's disease
- Norepinephrine plays a role in arousal, attention, and stress response
- Endocannabinoids lipid-based neurotransmitters that modulate synaptic transmission and regulate pain, appetite, and mood
Sensory Processing and Integration
- Sensory receptors specialized cells that detect and respond to specific stimuli (light, sound, touch, taste, smell)
- Sensory pathways relay information from receptors to the brain for processing and interpretation
- Thalamus acts as a gateway for sensory information before reaching the cortex
- Somatosensory cortex processes tactile and proprioceptive information from the body
- Organized somatotopically with different body parts represented in specific areas
- Visual cortex processes visual information from the retina
- Primary visual cortex (V1) receives input from the lateral geniculate nucleus of the thalamus
- Higher-order visual areas (V2, V3, V4, V5) involved in complex visual processing (color, motion, object recognition)
- Auditory cortex processes sound information from the cochlea
- Primary auditory cortex (A1) receives input from the medial geniculate nucleus of the thalamus
- Higher-order auditory areas involved in speech perception and music processing
- Multisensory integration combining information from different sensory modalities to create a unified perception of the environment
Motor Control and Coordination
- Motor cortex controls voluntary movements by sending signals to the spinal cord and muscles
- Primary motor cortex (M1) directly controls the execution of movements
- Premotor cortex and supplementary motor area involved in planning and coordinating complex movements
- Basal ganglia group of subcortical nuclei involved in motor control, learning, and decision-making
- Includes the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus
- Modulates activity of the motor cortex through direct and indirect pathways
- Cerebellum coordinates smooth, precise movements and maintains balance and posture
- Receives input from the motor cortex, sensory systems, and vestibular apparatus
- Compares intended movements with actual movements and makes necessary adjustments
- Spinal cord contains motor neurons that directly control muscle contractions
- Reflex arcs allow for rapid, automatic responses to stimuli without involving the brain
- Descending motor pathways carry signals from the brain to the spinal cord to initiate and control movements
- Corticospinal tract originates in the motor cortex and controls fine, precise movements
- Reticulospinal tract originates in the brainstem and controls posture and locomotion
Cognitive Functions and Memory
- Prefrontal cortex involved in executive functions (planning, decision-making, working memory, attention)
- Dorsolateral prefrontal cortex associated with working memory and cognitive flexibility
- Ventromedial prefrontal cortex involved in emotional regulation and decision-making
- Hippocampus plays a crucial role in the formation and consolidation of new memories
- Long-term potentiation (LTP) in the hippocampus underlies the strengthening of synaptic connections during memory formation
- Consolidation process by which short-term memories are converted into long-term memories
- Amygdala involved in emotional processing and the formation of emotional memories
- Interacts with the hippocampus to modulate the strength of emotional memories
- Working memory temporary storage and manipulation of information for complex cognitive tasks
- Involves the prefrontal cortex and other brain regions (parietal cortex, anterior cingulate cortex)
- Attention process of selectively focusing on relevant information while ignoring irrelevant stimuli
- Involves the prefrontal cortex, parietal cortex, and thalamus
- Language processing involves multiple brain regions (Broca's area, Wernicke's area, angular gyrus)
- Broca's area involved in speech production and grammar processing
- Wernicke's area involved in language comprehension and semantic processing
Emotional Regulation and Behavior
- Limbic system group of brain structures involved in emotional processing, motivation, and memory
- Includes the amygdala, hippocampus, hypothalamus, and anterior cingulate cortex
- Amygdala plays a central role in the processing and regulation of emotions, particularly fear and anxiety
- Receives input from sensory systems and sends output to the hypothalamus and brainstem to initiate emotional responses
- Hypothalamus regulates emotional responses and motivated behaviors (hunger, thirst, sexual behavior)
- Releases hormones that modulate emotional states and stress response (cortisol, oxytocin)
- Anterior cingulate cortex involved in emotional regulation, decision-making, and conflict monitoring
- Interacts with the prefrontal cortex and limbic system to regulate emotional responses
- Reward system involves the release of dopamine in the nucleus accumbens and other brain regions in response to rewarding stimuli
- Plays a role in reinforcing behaviors and motivating goal-directed actions
- Serotonergic system regulates mood, anxiety, and impulsivity
- Dysregulation of serotonin signaling associated with depression, anxiety disorders, and obsessive-compulsive disorder
- Stress response involves the activation of the hypothalamic-pituitary-adrenal (HPA) axis
- Releases cortisol to mobilize energy resources and modulate immune function
- Chronic stress can lead to dysregulation of the HPA axis and increased risk of mental health disorders
Clinical Applications and Disorders
- Neurodegenerative diseases characterized by progressive loss of neurons and cognitive decline
- Alzheimer's disease associated with accumulation of amyloid plaques and neurofibrillary tangles in the brain
- Parkinson's disease caused by degeneration of dopaminergic neurons in the substantia nigra, leading to motor symptoms
- Psychiatric disorders involve dysregulation of neurotransmitter systems and brain circuits
- Depression associated with reduced serotonin and norepinephrine signaling in the brain
- Schizophrenia involves dysregulation of dopamine and glutamate signaling, leading to psychotic symptoms
- Epilepsy neurological disorder characterized by recurrent, unprovoked seizures
- Caused by abnormal, excessive neuronal activity in the brain
- Anti-epileptic drugs (AEDs) used to control seizures by modulating neurotransmitter systems
- Traumatic brain injury (TBI) caused by external force to the head, leading to damage to brain tissue
- Can result in cognitive, emotional, and motor deficits depending on the location and severity of the injury
- Neuroimaging techniques used to diagnose and monitor brain disorders
- Magnetic resonance imaging (MRI) provides detailed images of brain structure
- Functional MRI (fMRI) measures changes in blood flow related to neuronal activity
- Positron emission tomography (PET) uses radioactive tracers to visualize brain function and neurotransmitter systems
- Neuromodulation techniques used to treat brain disorders by modulating neuronal activity
- Deep brain stimulation (DBS) involves implanting electrodes in specific brain regions to alleviate symptoms of Parkinson's disease and other movement disorders
- Transcranial magnetic stimulation (TMS) uses magnetic fields to stimulate or inhibit neuronal activity in targeted brain regions