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What are the two anatomical subdivisons of the nervous system?
- Central nervous system
- Peripheral nervous system
What body cavity does the CNS belong to?
Dorsal body cavity
What is the function of the CNS?
- Integration, processing,
- Interperts incoming sensory information
- Directs motor responses (both visceral
- & organs)
- Seat of higher functions
- Intelligence, memory, learning
In early developement how does the CNS begin?
As a mass of neural tissue organizing into hollow tubes
What is the PNS?
All neural tissue outside the CNS
What is the funciton of the PNS?
- Communication link with the CNS
- Provides sensory input
- Carries motor output
How does the PNS create a link with the CNS?
Nerves extend to/from brain & spinal cord
In the PNS where do the cranial nerves connect?
To & from brain
In the PNS where do the spinal nerves connect?
To & from the spinal cord
What are the two different types of cranial and spinal nerve fibers?
Afferent and Efferent are what type of anatomical division?
Where does the afferent division of the PNS begin?
Begins at receptors
Where does the efferent division of the PNS begin?
Begins inside the CNS
What does afferent mean?
What does efferent mean?
What is the function of the afferent nerve fiber?
Brings information to the CNS
What is the function of the efferent nerve fiber?
Carry motor commands from the CNS to the body
What type of nerve fibers are afferent?
What type of nerve fibers are efferent?
Give examples of efferent nerve fibers.
What are the efferent nerve fibers specialized to do?
Perform specific functions
Give examples of receptors.
- May be a dendrite, specialized cell or cluster of cells
- Or a complex sense organ
Name the two components of the afferent and efferent divisions?
Somatic & visceral
What does the somatic component monitor?
- Skeletal muscles, joints & the skin
- Voluntary of Involuntary
What does the visceral compontent control?
- Smooth muscle, cardiac muscle, glands
- Ventral body cavity system
- ANS outside awareness of control
What is neural tissue? What are two basic cell types?
- Nervous tissue
What is the function of neural tissue?
- Specialized for the conduction of electrical impluses from one
- Region of the body to another sends signals that are
- Rapid, specific and usually cause immediate response
What is another name for the perikaryon?
Describe the characteristics of the cell body?
- Usually has several branching dendrites, is attached to an
- Elongated axon that ends at one or more synaptic terminal
What is the does the cell body contain?
- Organelles responsible for energy production & biosynthesis
- Of organic molecules such as enzymes
The nerve cell neuron is highly specialized, what funciton can it perform as a result of this?
Transfer & process information
What is the function of the neurons?
Transmit the electrical impulse along their cell membrane
What kind of cell is a neuron (not nerve cell)?
- Excitable cells
- Highly specialized
What is the longest cell in the body? How long?
Why do neurons have longevity?
- It cannot divide or repair
- Lacks centrioles and centrosomes
Name the neuroglial cells of the CNS.
What are the functions of neuroglial cells?
- Supporting framework for neural tissue
- Provides nutrients to neurons
- Isolate and protect neurons
How many neuroglial cells are their?
5 times as many as neurons
What are the neuroglial cells capable of that the neurons are not?
Can divide and repair
How many types of glial cells are in the CNS?
How many types of glial cells are in the PNS?
What makes the neural tissue of the CNS different from the PNS?
When a stimulus is received it can only move one direction, why?
Because of the chemical synapse
What are astrocytes known as?
What is the function of the astrocytes?
- Shield neurons from direct contact with other neurons & fluid
- Maintain blood-brain barrier
- Structural repairs
- Absorbs and recycles neurotransmitters
What is the astrocyte feet?
Process of the astrocyte.
What is the function of the astrocyte feet?
Contacts the surface & covers most of the surface of capillaries within the CNS
What significantly increases the suface area of the astrocyte?
A large number of cytoplasmic processes
How does the increase of surface area of the astrocyte control the interstitial environment?
- By facilitating the exchange of ions and
- Other molecules within the extracellular fluid
- Within the CNS
What is the frame work of astrocytes?
Packed with microfilaments that extend across the breadth of the cell.
How does the astrocyte support the brain & spinal cord?
By forming a structural framework
What is essential for maintaining the blood-brain barrier?
Chemical secretions of the astrocyte
What are neurotropic factors?
- Secreted astrocyte chemicals involved in directing growth &
- Interconnection of developing neurons
What is the function of the oligodendrocytes?
Myelinate CNS axons
How does myelin improve the functional performance of neurons?
Myelin helps prevent the electrical current from leaving the axon
Large area wrapped in myelin
What are nodes of ravier? How are they produced?
- Gaps between the myelin sheaths
- Produced by adjacent oligodendrocytes
What is another name for myelin sheaths?
Nodes of Ravier
What is the area called white matter? Why does it appear white?
- Regions dominated by myelinated axons of the CNS
What is the area of gray matter? What makes it gray?
- Regions dominated by neuron cell bodies, dendrites, & unmyelinated axons
What are the microglia in the CNS?
In times of infection or injury what glial cells increase dramatically in the CNS?
Describe microglial cells?
Smallest glial cells, posess slender cytoplasmic processes with many fine branches
How are microglial cells developed?
Appear early in embroynic development through the division of mesodermal stem cells
Describe ependymal cells?
- Cubodial to columnar in form. Unlike typical epithelial cell axon
- They have a slender process that branch extensively, making direct
- Contact with glial cells in surrounding neural tissue
What is the ependyma?
A thin epithelial membrane(made up of ependymal cells) that lines ventricles or the brain, central canal of the spinal cord. A type of neuroglial
What do the ciliated ependymal cells assist with?
Circulation of the cerebrospinal fluid
What do the ependymal cells secrete?
Where is the neuroglial of the PNS appear?
Outside brian and spinal cord
What is a collection of nerve bodies in the PNS?
Where are satellite cells located?
They surround neuron cell bodies within ganglia
What is the function of satellite cells?
- Insulate the neuron from other stimuli
- Regulate the exchange of nutrients & wastes with extracellular fluid
Every cell in the PNS is covered by what?
What does the schwann cell aid in?
Regrowth of damaged axons
What is the neurolemma?
The superficial cytoplasmic covering of schwann cells
What does the perikaryon contain?
- Organelles that provide energy and perform biosynthetic activities.
- Neurons, mitochondria, free & fixed ribosomes & membranes of the
- Rough endoplasmic reticulum
Where does the nerve impulse begin?
The axon hillock
What do neurons lack?
Because the neuron lack centrioles what does that result in?
An inability to divide
What are neurofibrils?
Bundles of neurofilaments. Cytoskeleton elements that extend into the dendrites and axon
What does the cytoskeleton of the perikaryon contain?
Neurofilaments & neurotubules
What are nissl bodies?
What is another name for nissl bodies?
How is the action potential generated?
- At the axon when it is exposed to appropiate stimuli, producing a localized change in the
- Transmembrane potential
What is the transmembrane potential?
A property resulting from the equal distribution of ions across the neurilemma
A long cytoplasmic process capable of propagating an action potential
Where is the axon hillock?
A special region in the multipolar neuron that connects the initial segments of the axon to the soma
What is the axoplasm?
Cytoplasm of the axon
What does the axoplasm contain?
- Neurofibrils, neurotubules, numerous small vesicles, lysosomes, mitochondria and various
What is the side branching of an axon called?
What are the terminal arborizations?
- The main trunk & the collateral end
- In a series of fine terminal extentions
Where does the terminal arborization end?
At the synaptic terminal
What is the synaptic terminal?
- Where the neuron contacts another neuron or effector
- Part of the synapse
Describe axoplasmic transport?
Movement of organelles, nutrients, synthesized molecules & waste products between the cell body and synaptic terminals. Complex process. Consumes energy & relies on movement along the neurofibrils of the axon and it's branches
What is the synapse?
Specialized site where the neuron comminicates with another cell
Where is the terminal bouton found?
Where one neuron synapses on another
What is another name for the terminal bouton?
What is the function of the glial cells?
To limit the number & type of stimuli
Name the four structural classifications of neurons?
What are anaxonic? Where are they found?
- Small, cannot distinguish from dendrites
- Only found in CNS and in special sense organs
What does bipolar neurons contain?
A number of fine dendrites that fuse to form a single dendrite. Cell body lies between this dendrite & a single axon. Relatively rare
What important role do bipolar neurons play? Are their axons myelinated?
- Relaying sensory information concerning sight, smell, & hearing
- Axons are not myelinated
What does the pseudounipolar look like? Is it myelinated? What type of neurons are these?
- Continious dendrite & axonal processes & cell body lies off to one side. The initial segment lies at the base of the dendrite branches. May be myelinated
- Usually sensory neurons
What is the most common neuron in the CNS?
Describe a multipolar neuron?
All motor neurons that control skeletal muscles. Myelinated axons. Several dendrites & a single axon that may have one or more branches.
What are pre-ganglionic fibers?
Axons extending from the CNS to a ganglion
What are post ganglionic fibers?
Axons connecting the ganglion cells with the peripheral effectors
What are afferent fibers? Where are they found?
Axons of sensory neurons. Extend between sensory receptor and the spinal cord or brain
Name the three catagories of receptors.
Name the three functional classifications of neurons. Which system do they belong to?
- Sensory (PNS)
- Interneurons (CNS)
- Motor (PNS)
What is the function of the sensory neurons?
Transmits impulses from sensory receptors to CNS using afferent fibers
What forms the two afferent divisions of the PNS?
What does the somatic division of the PNS deliver?
- Information about the outside world and our position in it
- Consciously controlled
What organs belong in the somatic division?
Muscles, joints, skin, sense organs
What does the visceral division of the PNS deliver?
Information on internal conditions & status of other organs
What organs belong to the visceral division of the PNS?
Smooth muscle, cardiac muscle, organs, glands
What is the function of interneurons? Where are they located?
- Analysis of sensory inputs & coordination or motor outputs
- Within the CNS
- May be between the sensory & motor neurons
What neurons account for 99% of the body?
Most interneurons are structurally what type of neuron?
Finish this sentence, the more complex the given stimulus...
The greater the number of interneurons involved
What is the function of motor neurons?
Carry impulses away from the CNS to stimulate or modify the activity of a peripheral tissue or organ
What type of fibers are the motor neurons?
What is the efferent somatic division (SNS) responsible for?
Innervate skeletal muscles consciously controlled
What is the efferent visceral division responsible for?
- Effects organs, tissues, other muscles
- Little conscious control
What two properties of an axon determines the rate of impluse conduction?
- The presences or absence of a myelin sheath
- The diameter of the axon
What results in a change in the resting membrance potential?
How does the action potential develope?
After the plasmalemma is stimulated to a level known as threshold. Once threshold has been reached, the membrane permability to sodium & potassium ions changes
Ability of cell membrane (plasmalemma) to conduct electrical impulses
Define nerve impulse.
Propagation of action potentials
What is a vesicular synapses?
All somatic neuromuscular synapses utilize what?
What is the synaptic communication?
Neuroeffector junction where axon interacts with another neuron, muscle or gland
What is the process of chemical synapses?
- Action potential arrives at end of presynaptic axon
- Synaptic vesicles release neurotransmitter
- Neurotransmitter diffuses across synaptic cleft
- Neurotransmitters bind to postsynaptic membrane receptors
- Effects channels in postsynaptic membrane (close or open)
- Result=stimulation or inhibition
- Neurotransmitters are broken down by enzymes or transported back into presynaptic terminal.
What is present in the electrical synapses?(non-vesicular)
Gap junctions between the CNS & PNS neurons
In chemical synapses communication is which direction?
Only one way from presynaptic to postsynaptic
In electrical synapses communication is which direction?
Can convey nerve impulses in either direction
What are neuronal pools?
- Organized interneurons into smaller numbers
- Group of neurons with specific functions
- Defined by function soley
How many neurotransmitters are their?