2.1 Structure and function of the nervous system
3 min read•august 9, 2024
The nervous system is the body's control center, comprising the brain, spinal cord, and a vast network of nerves. It processes information, controls movements, and regulates bodily functions. Understanding its structure and function is crucial for grasping how drugs affect the brain and mind.
Neurons, the building blocks of the nervous system, communicate through electrical and chemical signals. They form complex networks, allowing for everything from simple reflexes to complex thoughts. This intricate system is protected by barriers like the blood-brain barrier, which regulates what enters the brain.
Nervous System Overview
Central and Peripheral Nervous Systems
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- (CNS) comprises the brain and spinal cord
- Processes and integrates information from the entire body
- Controls voluntary and involuntary actions
- (PNS) includes all nerves outside the CNS
- Connects the CNS to organs, muscles, and sensory receptors
- Divided into somatic and autonomic nervous systems
- Somatic system controls voluntary movements
- Autonomic system regulates involuntary functions (heart rate, digestion)
Cellular Components of the Nervous System
- Neurons function as the primary signaling units of the nervous system
- Consist of cell body, axon, and dendrites
- Transmit electrical and chemical signals
- Classified by function (sensory, motor, )
- Glial cells provide support and protection for neurons
- Types include astrocytes, oligodendrocytes, and microglia
- Maintain homeostasis, form myelin, and provide immune defense
- Outnumber neurons in the human brain by approximately 10 to 1
Brain Structure and Regions
Major Brain Divisions
- Brain regions divided into forebrain, midbrain, and hindbrain
- Forebrain includes cerebral cortex and subcortical structures
- Midbrain contains structures involved in visual and auditory processing
- Hindbrain comprises the cerebellum, pons, and medulla oblongata
- Cerebral cortex forms the outer layer of the brain
- Divided into four lobes: frontal, parietal, temporal, and occipital
- Responsible for higher-order cognitive functions (reasoning, language)
Subcortical Structures and Brainstem
- Limbic system includes structures involved in emotion and memory
- Key components: , , and
- Regulates emotional responses, learning, and motivation
- Brainstem connects the brain to the spinal cord
- Consists of midbrain, pons, and medulla oblongata
- Controls vital functions (breathing, heart rate, blood pressure)
- Spinal cord extends from the brainstem to the lower back
- Transmits signals between the brain and body
- Contains reflex circuits for rapid responses to stimuli
Neuronal Communication
Structural Components of Neurons
- Axons conduct electrical signals away from the cell body
- Can extend up to a meter in length
- Covered by myelin sheath to increase signal transmission speed
- Dendrites receive signals from other neurons
- Branch out in tree-like structures to increase surface area
- Contain dendritic spines that form synapses with other neurons
Synaptic Transmission and Plasticity
- functions as the junction between neurons
- Consists of presynaptic terminal, synaptic cleft, and postsynaptic membrane
- Transmits signals through release of neurotransmitters
- Neuroplasticity allows the brain to adapt and change
- Involves formation of new synapses and pruning of unused connections
- Crucial for learning, memory formation, and recovery from brain injury
Protective Barriers
Blood-Brain Barrier Structure and Function
- Blood-brain barrier (BBB) separates circulating blood from brain tissue
- Formed by specialized endothelial cells in brain capillaries
- Regulates passage of substances between blood and brain
- BBB protects the brain from harmful substances and pathogens
- Allows selective transport of essential nutrients and gases
- Presents challenges for drug delivery to the brain
- Disruption of BBB associated with various neurological disorders
- Can occur in conditions like and Alzheimer's disease
- May lead to inflammation and neuronal damage
Key Terms to Review (20)
Action Potential: An action potential is a rapid and temporary electrical signal that travels along the membrane of a neuron, allowing it to communicate information effectively. This process is crucial for the functioning of the nervous system, as it enables the transmission of signals between neurons and ultimately to muscles and glands. Action potentials are generated when a neuron's membrane potential reaches a specific threshold, leading to a sequence of ion movements that propagate the signal.
Agonist: An agonist is a substance that binds to a receptor and activates it, mimicking the action of a natural neurotransmitter. This activation can enhance or facilitate the effects of neurotransmission in the nervous system, leading to various physiological responses. By understanding how agonists interact with receptors, we can better grasp the basic principles of drug action, the role of neurotransmitters, and their influence on mental health and reward pathways.
Amygdala: The amygdala is a small, almond-shaped cluster of nuclei located deep within the temporal lobe of the brain that plays a crucial role in processing emotions and attaching emotional significance to experiences. It is involved in the regulation of various emotional responses, including fear, pleasure, and aggression, making it a key player in the emotional aspects of behavior and decision-making. The amygdala interacts with other brain regions, influencing both the physiological and psychological responses to stimuli.
Antagonist: An antagonist is a substance that binds to a receptor and inhibits or blocks its activity, preventing the normal biological response from occurring. This action is crucial in pharmacology, as antagonists can counteract the effects of agonists, which are substances that activate receptors and elicit a response. Understanding how antagonists work helps in comprehending drug actions, the nervous system's structure, neurotransmitter functions, and various mental health conditions influenced by drugs.
Central Nervous System: The central nervous system (CNS) is a crucial part of the nervous system, consisting of the brain and spinal cord. It acts as the control center for processing information and coordinating responses throughout the body, enabling complex functions like thought, movement, and sensory perception. The CNS is essential for maintaining homeostasis and integrating signals from both internal and external environments.
Dopamine: Dopamine is a neurotransmitter that plays several important roles in the brain and body, particularly in the regulation of mood, reward, and motor control. It is crucial for feelings of pleasure and satisfaction, influencing motivation and reinforcing behaviors associated with rewards.
EEG: EEG, or electroencephalography, is a non-invasive technique used to measure the electrical activity of the brain by placing electrodes on the scalp. It allows researchers to observe brain wave patterns and identify different states of consciousness, such as sleep, wakefulness, and responses to stimuli. This technique is crucial in understanding the structure and function of the nervous system and its interaction with various drugs in research settings.
FMRI: Functional Magnetic Resonance Imaging (fMRI) is a neuroimaging technique that measures and maps brain activity by detecting changes in blood flow and oxygen levels in the brain. It is crucial for understanding the structure and function of the nervous system, studying the neural basis of addiction, exploring personalized medicine in psychopharmacology, and advancing drug research through neuroimaging.
Hippocampus: The hippocampus is a critical brain structure involved in the formation and retrieval of memories, particularly episodic and spatial memories. It plays a key role in learning processes and is essential for converting short-term memories into long-term ones. Located in the medial temporal lobe, the hippocampus is also associated with navigation and spatial awareness, linking it to various cognitive functions and emotional regulation.
Hypothalamus: The hypothalamus is a small but crucial region located at the base of the brain, playing a vital role in maintaining homeostasis and regulating various bodily functions. It serves as a link between the nervous system and the endocrine system, coordinating processes such as temperature regulation, thirst, hunger, sleep-wake cycles, and emotional responses. By releasing hormones and influencing the pituitary gland, the hypothalamus helps control many key functions essential for survival and overall health.
Interneurons: Interneurons are a type of neuron that serves as a connector or relay between sensory neurons and motor neurons within the central nervous system. They play a crucial role in processing information, reflexes, and integrating sensory input to produce appropriate responses. Interneurons can be found in various regions of the brain and spinal cord, contributing to complex behaviors and functions such as learning, memory, and decision-making.
Motor neurons: Motor neurons are specialized nerve cells that transmit signals from the central nervous system to muscles and glands, facilitating movement and response. They play a crucial role in controlling voluntary and involuntary muscle actions, connecting the brain and spinal cord to the peripheral nervous system. By activating muscle fibers, motor neurons enable the execution of movements, reflexes, and various bodily functions.
Multiple sclerosis: Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system, where the immune system mistakenly attacks the protective myelin sheath covering nerve fibers. This damage disrupts communication between the brain and other parts of the body, leading to a wide range of physical and cognitive symptoms. The connection between MS and the structure and function of the nervous system is crucial, as it highlights how this disease can alter neurological processes, while also informing debates about treatment options, including the potential use of medical marijuana.
Neurogenesis: Neurogenesis is the process by which new neurons are generated in the brain, particularly in specific areas like the hippocampus. This process is crucial for learning, memory, and overall brain health, connecting to the dynamic ability of the nervous system to adapt and reorganize itself through experiences and environmental changes. Neurogenesis plays a vital role in neuroplasticity, the brain's ability to form and reorganize synaptic connections in response to learning and injury.
Parkinson's Disease: Parkinson's disease is a progressive neurological disorder that affects movement and coordination, primarily caused by the degeneration of dopamine-producing neurons in the brain. This loss of dopamine leads to a range of motor symptoms such as tremors, stiffness, and balance issues, connecting deeply to the structure and function of the nervous system, as well as neurotransmitter roles and behavioral implications.
Peripheral Nervous System: The peripheral nervous system (PNS) is a major component of the nervous system that lies outside the brain and spinal cord, connecting the central nervous system (CNS) to the limbs and organs. It is crucial for transmitting sensory information from the body to the CNS and relaying motor commands from the CNS to the muscles, enabling coordinated movement and responses to environmental stimuli.
Sensory Neurons: Sensory neurons are specialized nerve cells responsible for converting external stimuli from the environment into internal electrical impulses that are sent to the central nervous system. They play a crucial role in processing sensory information, allowing organisms to perceive their surroundings through senses such as sight, sound, touch, taste, and smell. This process is essential for survival, as it enables the body to respond appropriately to various stimuli.
Serotonin: Serotonin is a neurotransmitter that plays a crucial role in regulating mood, emotion, and various physiological functions within the brain and body. Its impact extends to influencing behaviors like sleep, appetite, and overall emotional well-being, making it vital for understanding mental health and pharmacology.
Synapse: A synapse is a junction between two neurons that allows for communication through the transmission of neurotransmitters. This connection plays a crucial role in the transmission of signals within the nervous system, enabling the brain to process information and coordinate responses. Synapses can be excitatory or inhibitory, influencing whether the receiving neuron will fire an action potential, which is essential for all neural activities.
Synaptic Pruning: Synaptic pruning is a natural process that occurs in the brain where excess synapses, or connections between neurons, are eliminated. This process is crucial for brain development and function, allowing for a more efficient neural network by reducing redundancy in neural connections. It primarily takes place during critical periods of brain development, such as childhood and adolescence, impacting learning and cognitive abilities.