3.3 Parts of the Nervous System
3 min read•june 24, 2024
The nervous system is our body's command center, orchestrating everything from conscious movements to unconscious bodily functions. It's divided into central and peripheral systems, with specialized cells called communicating through electrical and chemical signals.
The has two main divisions: somatic and autonomic. The somatic system controls voluntary movements, while the autonomic system regulates involuntary functions. The autonomic system further splits into sympathetic ("") and parasympathetic ("") branches, working together to maintain balance.
Nervous System Overview
Central vs peripheral nervous systems
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- (CNS) consists of the brain and
- Processes and integrates sensory information from the body and environment
- Makes decisions and generates appropriate responses based on this information
- Coordinates and controls various bodily functions to maintain
- Peripheral nervous system (PNS) includes nerves and ganglia outside the brain and spinal cord
- Connects the CNS to the rest of the body, allowing for communication between them
- Transmits sensory information from receptors (skin, eyes, ears) to the CNS for processing
- Carries motor commands from the CNS to effectors (muscles, glands) to execute responses
- Divided into somatic and autonomic nervous systems for different functions
Neural Communication
- Neurons are the basic functional units of the nervous system
- Specialized cells that transmit electrical and chemical signals
- are chemical messengers released by neurons
- Allow communication between neurons across
- Synapses are the junctions where neurons communicate with each other
- is the electrical signal that travels along a neuron's axon
- Enables rapid transmission of information over long distances
Spinal Cord
- Part of the CNS that connects the brain to the rest of the body
- Carries sensory information to the brain and motor commands from the brain
- Involved in reflexes and some automatic responses
Peripheral Nervous System Divisions
Somatic vs autonomic regulation
- enables voluntary control of skeletal muscles
- Involved in conscious actions (walking, talking, writing) and reflexes (knee-jerk reflex)
- Receives sensory input from external stimuli (touch, pressure, temperature) for perception
- provides involuntary control of smooth muscles, cardiac muscle, and glands
- Regulates unconscious bodily functions essential for survival and homeostasis
- Adjusts heart rate, digestion, respiratory rate, pupillary response (pupil size), urination, and sexual arousal
- Divided into sympathetic and parasympathetic divisions with opposing effects on organs
- Regulates unconscious bodily functions essential for survival and homeostasis
Sympathetic and parasympathetic homeostasis
- activates the "fight or flight" response during stress or emergencies
- Increases heart rate and blood pressure to deliver more oxygen and nutrients to muscles
- Dilates pupils (widens) and bronchioles (airways) to enhance vision and breathing
- Decreases digestion and urination to conserve energy for immediate survival needs
- Stimulates glucose release from the liver to provide quick energy for the body
- promotes the "rest and digest" response during relaxed situations
- Decreases heart rate and blood pressure to conserve energy and maintain a resting state
- Constricts pupils (narrows) and bronchioles to protect the eyes and lungs
- Increases digestion and urination to process food and eliminate waste products
- Promotes glucose storage in the liver to replenish energy reserves for future use
- Sympathetic and parasympathetic divisions work in opposition to maintain homeostasis
- Constantly adjust bodily functions in response to changing internal and external conditions
- Example: Heart rate regulation
- Sympathetic stimulation increases heart rate during exercise or stress
- Parasympathetic stimulation decreases heart rate during rest or relaxation
- Balance between the two divisions maintains a steady heart rate at rest (60-100 bpm)
Key Terms to Review (14)
Action Potential: An action potential is a rapid, transient electrical signal that travels along the membrane of a neuron or other excitable cell. It is the fundamental unit of communication in the nervous system, allowing neurons to transmit information and coordinate various physiological processes throughout the body.
Autonomic Nervous System: The autonomic nervous system is a division of the nervous system that controls and regulates the body's involuntary functions, such as heart rate, blood pressure, digestion, and respiration. It operates without conscious control, allowing the body to maintain homeostasis and respond to internal and external stimuli automatically.
Central Nervous System: The central nervous system (CNS) is the primary information processing and control center of the body, consisting of the brain and spinal cord. It is responsible for integrating and coordinating the body's physiological processes, sensory inputs, and motor outputs.
Fight or Flight: The fight-or-flight response is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It is a survival mechanism that prepares the body to fight or flee from danger by triggering the sympathetic nervous system to release hormones that increase heart rate, blood pressure, and glucose levels.
Homeostasis: Homeostasis is the process by which the body maintains a stable and balanced internal environment, despite changes in external conditions. It is a fundamental principle that helps the body function optimally by regulating various physiological processes, including temperature, blood pressure, and fluid balance.
Neurons: Neurons are the fundamental units of the nervous system, responsible for the transmission of electrical signals throughout the body. They are specialized cells that play a crucial role in the functioning of the Parts of the Nervous System and the Brain and Spinal Cord.
Neurotransmitters: Neurotransmitters are chemical messengers that facilitate communication between neurons in the nervous system. They are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, triggering a response that can either excite or inhibit the target cell. Neurotransmitters play a crucial role in various psychological processes and behaviors, including cognition, emotion, and motor function.
Parasympathetic Nervous System: The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system, responsible for the body's rest-and-digest functions. It works in opposition to the sympathetic nervous system, promoting activities that conserve and restore energy.
Peripheral Nervous System: The peripheral nervous system (PNS) is the part of the nervous system that is located outside the central nervous system (brain and spinal cord). It is responsible for transmitting information between the central nervous system and the rest of the body, including sensory information from the body to the brain and motor commands from the brain to the muscles.
Rest and Digest: The rest and digest response, also known as the parasympathetic nervous system, is the state of the body when it is at rest, conserving energy, and focusing on regulatory functions like digestion, urination, and sexual arousal. This is the opposite of the fight-or-flight response controlled by the sympathetic nervous system.
Somatic Nervous System: The somatic nervous system is the division of the peripheral nervous system that is responsible for controlling the voluntary movements of the body and transmitting sensory information from the external environment to the central nervous system. It consists of sensory and motor neurons that connect the brain and spinal cord to the muscles, skin, and other parts of the body.
Spinal Cord: The spinal cord is a long, cylindrical structure that extends from the base of the brain, called the medulla oblongata, down through the vertebral column. It serves as the main communication pathway between the brain and the rest of the body, transmitting sensory information and motor commands.
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 react to perceived threats or stressful situations by increasing heart rate, blood pressure, and respiration, while also redirecting blood flow away from the digestive system and towards the muscles.
Synapses: Synapses are the specialized junctions between neurons where information is transmitted from one cell to another. They are essential for the communication and coordination of the nervous system, enabling the transmission of electrical and chemical signals throughout the body.