Unit 4 Nervous System Flashcards
Nervous System Basic Function
Receives sensory data from the environment, informing body of external conditions
transmits signals throughout the body to regulate homeostasis
Neuron
Specialized nerve cell that is functional unit of nervous system
Nervous System Signalling/Neurons allow
An organism to receive and respond to both internal and external stimuli.
What is Neuronal Signalling?
Communication by neurons (reception, transmission, integration, response)
Reception
Detection of a stimulus by neurons and by specialized sensory receptors (i.e. in eyes and skin)
Transmission
Movement of a message along a neuron to another neuron or muscle or gland
Integration
sorting and interpretation of multiple neural messages and the determination of the appropriate response
Response
output or action resulting from the integration of neural messages
Three classes of neurons
-Afferent Neurons
-Interneurons
-Efferent Neurons
Afferent neurons
Sensory neurons that transmit stimuli collected by their sensory receptors to interneurons
Interneurons
Integrate information to formulate the best response (approximately 99% of interneurons are in brain and spinal cord)
Efferent Neurons
Carry response signal away from the interneurons to the effectors which are the muscles and glands
efferent neurons that carry signals from interneurons to skeletal muscle
Motor Neurons
Processing Steps (5)
- Stimulus Reception by sensory receptors on afferent neurons
- Message carried by afferent neurons to interneurons
- Integration of neural message in interneurons
- response by the transmission of neural messages by efferent neurons to effectors
- Appropriate action occurs
Description of Neuron Structure
Can vary widely in size and shape
Structure of Neuron includes
One enlarged cell body; two extension types
Cell Body contains and function
-Nucleus and most of the organelles in the cell
-Synthesizes most of proteins, lipids and carbohydrates
Projections (Extensions) do what
Conduct electrical signals
Two projections names
Dendrites
Axons
Dendrites
Highly-branched projections
Form tree-like outgrowth at one end of neuron
receives signals and transmits them toward cell body
Axons
Conduct signals away from cell body to another neuron or effectors
Basic Elements of a Neuronal Circuit
Connections between axon terminal of one neuron and the dendrites or cell body of a second neuron
Typical neuronal circuit contains what
An afferent neuron, one or more interneurons, an efferent neuron
Origins of Interneuron Input; List Potential Connection Points of Interneurons; all of this leads to creation of
Several axons; may connect to other interneurons and several efferent neurons; leads to creation of neuronal networks throughout the body
All cells in the nervous system do not consist of what
Neurons
What Glial Cells do and do not do
Provide nutrition and support to neurons; do not conduct electrical signals
Glial Cells retain
capacity to divide throughout the life of an animal
Why do glial cells divide?
Replace damaged of dead cells
Glial cells are a source of
nearly all brain tumours (produced when regulation is lost)
Schwann Cells do what
form tightly wrapped layers of plasma membrane called myelin sheaths around axons
Myelin sheaths act as
electrical insulators due to high lipid content
Name of Gaps between Schwann Cells
Nodes of Ranvier
Nodes of Ranvier Function
Expose membrane of axon directly to extracellular fluid
Function of Arrangement
Arrangement of insulated stretches of axons, punctuated by gaps that are uninsulated, speeds the rate at which electrical impulses move along the axons
