9.2 Structure and Function of the Nervous System
4 min read•june 18, 2024
The nervous system is the body's command center, orchestrating everything from conscious thoughts to involuntary reflexes. It's made up of , specialized cells that communicate through electrical and chemical signals, forming complex networks that control our actions and reactions.
Understanding the nervous system's structure and function is crucial for grasping how drugs affect the body. From the brain's higher cognitive functions to the autonomic regulation of vital organs, this intricate system is the target of many medications and the source of numerous health conditions.
Structure and Function of the Nervous System
Structure and function of neurons
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- Neurons fundamental units of the nervous system
- Cell body contains nucleus and other organelles essential for cellular functions
- Dendrites branch-like extensions that receive signals from other neurons (synaptic input)
- long, thin fiber that conducts electrical impulses away from the cell body to other neurons or target cells
- Axons are often covered by , which enhances signal transmission speed
- Axon terminals specialized structures at the end of the axon that release neurotransmitters to communicate with other neurons or target cells (synaptic output)
- Neurons communicate through electrical and chemical signaling
- Electrical signaling occurs within the through action potentials
- Action potentials generated by changes in the membrane potential due to ion flow through voltage-gated channels (sodium and potassium)
- Chemical signaling occurs between neurons at synapses
- Neurotransmitters released from the presynaptic neuron's axon terminals into the synaptic cleft (space between neurons)
- Neurotransmitters bind to receptors on the postsynaptic neuron or target cell, causing excitation (depolarization) or inhibition (hyperpolarization)
- Electrical signaling occurs within the through action potentials
Components of nervous systems
- consists of the brain and spinal cord
- Brain divided into several regions with specific functions
- responsible for higher cognitive functions (thinking, learning, memory), sensory processing (vision, hearing, touch), and voluntary movement
- coordinates balance, posture, and fine motor control (smooth, coordinated movements)
- regulates vital functions such as breathing, heart rate, and consciousness ()
- Spinal cord serves as a conduit for sensory and motor information between the brain and the body
- Conducts sensory and motor information between the brain and the body through ascending and descending pathways
- Responsible for reflexes and central pattern generators (walking, swimming)
- Brain divided into several regions with specific functions
- consists of nerves and ganglia outside the CNS
- Sensory () division carries information from sensory receptors to the CNS
- detects stimuli from the external environment (touch, pressure, temperature) and the body's position and movement ()
- monitors internal organs and tissues (blood pressure, gut distension)
- Motor () division carries signals from the CNS to effector organs (muscles, glands)
- controls voluntary movement of skeletal muscles (walking, grasping)
- regulates involuntary functions of internal organs and glands (heart rate, digestion)
- activates "fight or flight" response
- promotes "rest and digest" functions
- Sensory () division carries information from sensory receptors to the CNS
Sympathetic vs parasympathetic regulation
- (SNS) activates the body's "fight or flight" response during stress or emergency situations
- Increases heart rate and blood pressure to deliver more oxygen and glucose to tissues
- Dilates bronchioles to improve oxygen intake and gas exchange
- Stimulates glucose release from the liver to provide energy for the body
- Diverts blood flow to skeletal muscles and away from digestive system to prioritize physical activity
- Dilates pupils () and reduces tear and saliva production to enhance sensory awareness
- (PNS) promotes "rest and digest" functions during relaxed states
- Decreases heart rate and blood pressure to conserve energy
- Constricts bronchioles to prevent overinflation of the lungs
- Stimulates digestion and (movement of food through the digestive tract)
- Promotes secretion of digestive enzymes, tears (), and saliva (salivation)
- Constricts pupils () to protect the eyes from bright light
- SNS and PNS work together to maintain homeostasis by modulating the activity of various organs and systems
- Often have opposing effects on target organs (antagonistic actions)
- Balance between the two systems is crucial for proper functioning of the body and adaptation to changing environments
Additional Nervous System Components and Processes
- support and protect neurons, maintaining the optimal environment for neural function
- The is a selective membrane that protects the CNS from potentially harmful substances in the bloodstream
- refers to the brain's ability to reorganize and form new neural connections throughout life
- Reflex arcs are rapid, involuntary responses to stimuli that bypass conscious control
- Neuromodulators are substances that can alter the effects of neurotransmitters, influencing neural communication and behavior
Key Terms to Review (42)
Action potential: An action potential is a rapid, temporary change in the electrical membrane potential of a cell. It is essential for the conduction of electrical impulses in cardiac and nerve cells.
Action Potential: An action potential is a rapid, transient electrical signal that propagates along the membrane of an excitable cell, such as a neuron or muscle cell. It is the fundamental unit of communication in the nervous system, allowing for the transmission of information between different parts of the body.
Afferent: Afferent refers to the nerves or neural pathways that transmit sensory information from the body's receptors to the central nervous system, such as the brain and spinal cord. These nerves and pathways carry signals that convey sensations, perceptions, and other inputs from the periphery to the central processing centers.
Autonomic Nervous System: The autonomic nervous system is the part of the nervous system that controls and regulates the body's internal organs and involuntary functions, such as heart rate, breathing, digestion, and blood pressure, without conscious control. It is a critical component in maintaining homeostasis and ensuring the body's proper functioning.
Axon: An axon is a long, slender projection of a neuron that transmits electrical signals away from the neuron's cell body to other cells. It is the primary means by which neurons communicate with each other and with target cells within the nervous system.
Axon Terminal: The axon terminal is the distal end of an axon, where neurotransmitters are released into the synaptic cleft to facilitate communication between neurons. It is a crucial component in the structure and function of the nervous system.
Blood-Brain Barrier: The blood-brain barrier is a highly selective semipermeable membrane that separates the circulating blood from the brain and central nervous system (CNS). It acts as a gatekeeper, controlling the movement of substances between the bloodstream and the brain to protect the delicate neural tissue from harmful substances while allowing the passage of essential nutrients, oxygen, and other molecules required for proper brain function.
Brainstem: The brainstem is the posterior part of the brain that connects the cerebrum to the spinal cord. It is responsible for regulating many of the body's basic functions, including respiration, heart rate, blood pressure, and consciousness.
Central Nervous System: The central nervous system (CNS) is the primary control center of the body, responsible for integrating and coordinating all bodily functions. It consists of the brain and spinal cord, and serves as the main hub for processing and transmitting information throughout the body.
Central nervous system (CNS): The central nervous system (CNS) consists of the brain and spinal cord, responsible for processing and transmitting information throughout the body. It integrates sensory information and coordinates bodily functions.
Cerebellum: The cerebellum is a region of the brain located at the back of the skull, just above the brainstem. It is primarily responsible for coordinating voluntary movements, maintaining balance and posture, and regulating muscle tone.
Cerebrum: The cerebrum is the largest and uppermost part of the brain, responsible for a wide range of cognitive functions, including perception, motor control, learning, and memory. It is the center of higher brain functions and plays a crucial role in the structure and function of the nervous system.
Dendrite: A dendrite is a branched projection of a neuron that receives signals from other neurons and transmits them to the cell body. Dendrites are a crucial component of the nervous system, responsible for the integration and processing of information within the neural network.
Efferent: Efferent refers to the nerve fibers or pathways that carry information or signals away from the central nervous system (CNS) to the peripheral tissues and organs. These efferent pathways are responsible for transmitting motor commands and regulating the body's involuntary functions.
Glial Cells: Glial cells, also known as neuroglia or simply glia, are non-neuronal cells that provide support and protection for the neurons in the nervous system. They are essential for the proper functioning and maintenance of the central and peripheral nervous systems.
Lacrimation: Lacrimation refers to the production and secretion of tears by the lacrimal glands. It is a physiological process that helps maintain the health and function of the eyes by lubricating, nourishing, and protecting them from foreign particles and irritants.
Miosis: Miosis is the process of pupillary constriction, or the narrowing of the pupil, in response to increased light exposure. It is a reflex controlled by the parasympathetic division of the autonomic nervous system and plays a crucial role in regulating the amount of light entering the eye.
Mydriasis: Mydriasis is the dilation or widening of the pupil of the eye. It is a physiological response controlled by the autonomic nervous system and can occur due to various stimuli or medical conditions.
Myelin: Myelin is a fatty, insulating sheath that wraps around the axons of certain nerve cells, known as myelinated neurons, in the central and peripheral nervous systems. It is essential for the efficient and rapid transmission of electrical impulses along the nerve fibers.
Neuromodulator: Neuromodulators are a class of neurotransmitters that do not directly excite or inhibit neurons, but rather modulate the activity of neural circuits. They influence the release, uptake, and effects of other neurotransmitters, thereby shaping the overall function of the nervous system.
Neuron: A neuron is the fundamental unit of the nervous system, responsible for the transmission of electrical and chemical signals throughout the body. Neurons are specialized cells that enable communication, information processing, and coordinated responses within the structure and function of the nervous system.
Neurons: Neurons are specialized cells in the nervous system responsible for transmitting information through electrical and chemical signals. They are the fundamental units that facilitate communication within the brain and between the brain and the rest of the body.
Neuroplasticity: Neuroplasticity is the brain's ability to reorganize itself by forming new neural connections throughout life. It allows neurons in the brain to compensate for injury and disease, and to adjust their activities in response to new situations or changes in their environment.
Neuroplasticity: Neuroplasticity refers to the brain's ability to adapt, change, and reorganize itself in response to new experiences, learning, and environmental demands. It is a fundamental property of the nervous system that allows the brain to modify its structure and function throughout an individual's lifetime.
Neurotransmitter: Neurotransmitters are chemical messengers that transmit signals between neurons or between neurons and other cells, such as muscle or gland cells, at the synaptic junction. They play a crucial role in the structure and function of the nervous system by facilitating communication and regulating various physiological and psychological processes.
Parasympathetic nervous system: The parasympathetic nervous system (PNS) is a division of the autonomic nervous system that conserves energy by slowing the heart rate and increasing intestinal and gland activity. It is often referred to as the 'rest and digest' system.
Parasympathetic Nervous System: The parasympathetic nervous system is a division of the autonomic nervous system responsible for the body's rest-and-digest functions. It plays a crucial role in maintaining homeostasis and regulating various physiological processes, including digestion, heart rate, and urination.
Peripheral Nervous System: The peripheral nervous system (PNS) is the part of the nervous system that is located outside the central nervous system (CNS), which includes the brain and spinal cord. The PNS consists of the somatic and autonomic nervous systems, and it is responsible for transmitting information between the CNS and the rest of the body.
Peripheral nervous system (PNS): The peripheral nervous system (PNS) consists of all the nerves outside the brain and spinal cord. It connects the central nervous system (CNS) to limbs and organs, facilitating communication throughout the body.
Peristalsis: Peristalsis is the coordinated, rhythmic contractions of smooth muscles that move food through the gastrointestinal tract. It ensures the progressive movement of contents from the esophagus to the rectum.
Peristalsis: Peristalsis is the rhythmic, wave-like contraction of smooth muscles that propels food and other materials through the digestive tract. This coordinated movement is essential for the proper functioning of the gastrointestinal system and is influenced by the nervous system.
Proprioception: Proprioception is the sense of the relative position of one's own body parts and movements. It is the body's ability to sense its own position, movements, and actions without the need for visual cues. This awareness of the body's position and movements is crucial for coordinated and controlled movements.
Reflex Arc: A reflex arc is a neural pathway that mediates a reflex, which is an automatic and involuntary response to a specific stimulus. It is a fundamental component of the nervous system's structure and function, responsible for the rapid and coordinated responses that help maintain homeostasis and protect the body from harm.
Reticular Formation: The reticular formation is a complex network of neurons located in the brainstem that plays a crucial role in regulating various functions of the nervous system, including consciousness, sleep-wake cycles, and motor control.
Somatic Motor System: The somatic motor system is the part of the motor division of the peripheral nervous system responsible for the voluntary control of body movements. It consists of motor neurons that innervate skeletal muscles, allowing for conscious and intentional control of our musculature.
Somatic Sensory System: The somatic sensory system is a complex network of receptors and pathways that allow the body to perceive and interpret various sensations, including touch, pressure, temperature, and proprioception (awareness of body position and movement). This system is crucial for our understanding of the physical world and our ability to interact with our environment effectively.
Sympathetic nervous system: The sympathetic nervous system is a part of the autonomic nervous system responsible for the body's 'fight or flight' response. It prepares the body to respond to stress or emergencies by increasing heart rate, dilating airways, and mobilizing energy stores.
Sympathetic Nervous System: The sympathetic nervous system is a division of the autonomic nervous system that is responsible for the body's fight-or-flight response. It prepares the body to respond to perceived threats or stressful situations by increasing heart rate, blood pressure, and breathing rate, while also diverting blood flow away from the digestive system and towards the muscles.
Synapse: A synapse is the junction between two neurons where electrical or chemical signals are transmitted. It plays a critical role in neural communication and signaling within the nervous system.
Synapse: A synapse is the junction between two neurons where communication occurs through the transmission of electrical or chemical signals. It is a critical component of the nervous system, facilitating the transfer of information between different parts of the body and the brain.
Visceral Sensory System: The visceral sensory system is a component of the somatosensory system responsible for transmitting sensory information from the internal organs and viscera to the central nervous system. It allows the brain to perceive and process sensations originating from the body's internal environment, such as hunger, thirst, and pain.
Voltage-Gated Channel: Voltage-gated channels are specialized membrane proteins that open and close in response to changes in the electrical potential across the cell membrane. These channels play a crucial role in the structure and function of the nervous system by facilitating the generation and propagation of electrical signals, known as action potentials, which are essential for neural communication.