Nervous System Flashcards
What are the main components and functions of the nervous system?
The nervous system is made up of neurones and support cells called glia. It controls all bodily functions, from basic actions like walking, breathing, and regulating heart rate to complex tasks such as problem-solving. Like other systems in the body (e.g. urinary or cardiovascular systems), the nervous system consists of specialized cells working together to maintain essential processes.
What is a neuron and its primary functions?
Definition: Neurons are the basic functional units of the nervous system, acting as building blocks (like bricks in a house).
Quantity: The nervous system contains 22 to 100+ billion neurons, with each neuron connecting to 50,000+ other neurons.
Functions:
Receive Impulses: From sensory receptors and other neurons.
Transmit Impulses: To the next neuron or to effector organs (muscles, organs, glands) for action.
How does the nervous system process information and produce responses?
The NS receives information. from receptors (visual, skin, touch and pain), integrates internal and external information and responds with movements(muscles), fight or flight response (increased heart rate, alertness) hormonal secretion (adrenaline release during stress). These process are achieved through neurons and neural impulses.
What are glial cells and their role in the nervous system?
Definition: Glial cells (or neuroglia) are support cells in the nervous system that do not directly participate in neural communication.
Functions:
Aid in the functioning of neurons by providing support, nourishment, and protection.
Maintain homeostasis and contribute to the overall health of the nervous system.
Other Cells: While glial cells are unique to the nervous system, other cell types (e.g., blood vessel cells) also exist but are not exclusive to this system.
What are the characteristics and functions of neurons?
Characteristics:
Neurons are specialized cells with a structure adapted for their function, including:
A cell body filled with cytoplasm and organelles.
Axon terminals that transmit signals.
Synapses as tiny junctions for communication.
Functions:
Produce neural impulses to stimulate other neurons, organs, glands, and muscles.
Communicate through electro-chemical signals:
A neuron receives stimulation when a neurotransmitter is sent and received across a synapse.
How do neurons transmit signals and communicate with each other?
Neurons receive stimulation at one end and transmit messages along their entire length via electrical impulses (neural impulses).
Transmission Along the Axon:
The signal travels down the neuron’s axon as an electrical impulse.
Communication Between Neurons:
When the neural impulse reaches the end of Neuron A, it communicates with Neuron B by:Releasing neurotransmitters into the synapse (the junction between neurons).
Electro-Chemical Communication:
This chain of electro-chemical communication is the biological basis for encoding and transmitting information throughout the nervous system.
What are the main components of a neuron and their functions?
Main Components:
Soma (Cell Body): Contains the nucleus and organelles, including mitochondria.
Dendrites: Receive signals from other neurons and sensory receptors.
Axon: Transmits electrical impulses away from the cell body to other neurons or effectors.
Functions of Components:
Nucleus: Contains genetic information (chromosomes) that directs protein synthesis, determining the neuron’s type and function.
Mitochondria: Perform metabolic activities to provide energy for the neuron to function effectively.
What are the roles of dendrites and axons in neurons?
Dendrites:
Structure: Branching extensions that emerge from the cell body.
Function:
Receive stimulation across synapses from other neurons.
Their branching structure allows them to collect signals from many neurons, enhancing communication.
Axon:
Structure: A long projection that extends from the cell body.
Function:
Transmits electrical impulses away from the cell body to other neurons or effectors.
What is the myelin sheath and its significance in neuronal function?
Definition:
Myelin is a lipoprotein material that covers many axons, providing insulation.
Functions:
Increases Efficiency: Insulates the axon to enhance the speed and strength of neural impulses.
Reduces Energy Requirement: Without myelin, neural impulses would be slower, weaker, and require more energy.
Production:
Oligodendrocytes: Produce myelin in the brain and spinal cord.
Schwann Cells: Produce myelin in other parts of the nervous system.
What are afferent and efferent neurons?
Afferent Neurons:
Function: Send sensory impulses from the body to the brain and spinal cord.
Information Carried: Contains sensory information regarding touch, temperature, taste, vision, hearing, etc.
Efferent Neurons:
Function: Send impulses from the brain and spinal cord to muscles, organs, and glands.
Purpose: Produces movement or stimulates effector organs.
Directional Terms:
Afferent: Towards a structure.
Efferent: Away from a structure.
What are axon terminals and their role in neuronal communication?
Definition:
Axon Terminals (or Presynaptic Terminals): The endings of the axon where the neuron communicates with other cells.
Functions:
Form Synapses: Create synapses with the dendrites of other neurons and with effector organs (muscles, glands).
Stimulate Multiple Targets: A single neuron can stimulate many other neurons and effector organs, facilitating widespread communication within the nervous system.
How do neurons send information in the nervous system?
Neurons “send information” by transmitting messages to each other, either:
Excitation: Telling another neuron to fire.
Inhibition: Telling another neuron not to fire.
Translation to Sensation and Behavior:
Sensory Communication:
A receptor (e.g., mechanoreceptor in the skin) sends messages to the brain indicating stimulation (e.g., touch).
Motor Communication:
A motor neuron sends a message to a muscle, gland, or organ to produce an action (e.g., causing a muscle to contract).
How does the nervous system integrate complex information?
Complex Communication:
The nervous system communicates complex information (e.g., problem-solving) by integrating inputs from multiple neurons.
Neuronal Stimulation:
A single neuron’s stimulation is not sufficient to trigger the next neuron to fire.
Neurons receive input from many sources, including:
Multiple Neurons: Stimulation from many different neurons.
Repeated Stimulation: Continuous input from the same neurons.
Types of Inputs:
Inputs can be:
Excitatory: Promote the firing of the next neuron.
Inhibitory: Prevent the firing of the next neuron.
How do neurons integrate multiple inputs to make decisions?
Role of Neurons:
Neurons act as integrators of information rather than mere communicators of simple messages.
Decision-Making Process:
A neuron decides whether to fire based on:
The number of inputs it receives.
The net sum of these inputs:
Excitatory Inputs: Promote firing.
Inhibitory Inputs: Prevent firing.
Comparison to Systems:
The nervous system resembles a computer more than a simple line of telephone wires, processing complex information through integration and decision-making.
How do neurons produce complex behaviors in the brain?
Understanding brain activity requires examining neural networks rather than single neurons.
Neurons work together, communicating through:
Repeated neural impulses.
Impulses of varying durations, where timing can convey information.
Example: In the primary motor cortex:
50 ms impulses result in muscle twitching.
500 ms impulses produce coordinated movements, like raising a hand to the mouth.
