A+P II Ch7 Flashcards
What are the parts of the Nervous System?
Central Nervous System
Peripheral Nervous System
What is consistent in the Central Nervous System (CNS)?
Brain
Spinal cord
What does the Peripheral Nervous System (PNS) consist of?
Afferent information (input)
Efferent information (output)
What is the function of the Central Nervous System?
Receives and processes information from sensory organs and viscera.
Where does the Sensory organs information originate?
External Environment
Where does the Viscera information originate?
Internal Environment
What kind of information does the Central Nervous System send?
Send instructions to muscles and glands instructing them to perform appropriate tasks.
What are the subdivisions of the Peripheral Nervous System?
Afferent and Efferent
What is the Peripheral Nervous System consist of?
Neurons
what are the primary actions of Afferent?
Neurons transmit sensory and visceral information from the organs to the Central Nervous System.
What information is transmitted from the Afferent to the Central Nervous System?
Somatic Senses (skin, muscles, and joints)
Special Senses (vision, hearing, equilibrium, smell, and taste)
Visceral Information ( dietary fullness, blood pressure, and blood pH.)
Efferent
Neurons that transmit information from the Central Nervous System to organs in the periphery. (effector organs)
What are the two subdivisions of Efferent?
somatic( Voluntary)
Autonomic (involuntary) nervous system
Somatic Nervous System
Consists of the motor neurons, which regulate skeletal muscle contractions
Autonomic Nervous System
Consists of neurons that regulate the function of internal organs and other structures (sweat glands and blood vessels)
What are the two branches of Autonomic Nervous System?
Parasympathetic Nervous System
Sympathetic Nervous System
Sympathetic Nervous System
Fight or Flight response and preps the body for any potential danger
Parasympathetic Nervous System
Rest and digest response which brings the body to a state of calm
What are the two main classes of cells in the Nervous System?
Neurons (Excitable cells)
Glial cells (Support cells)
Neurons (Excitable cells)
The functional and smallest unit that can carry out the function of the tissue. Communicate by transmitting electrical impulses
Excitable cells
Capable of producing large, rapid electrical signals (action potentials)
Glial cells (Support cells)
90% of the cells in the nervous system. Provide various types of support to the neurons (structural and metabolic support)
Synapse
Site of communication between two neurons or a neuron and an effector organ
Action Potentials
Brief, large changes in membrane potential during which the inside of the cell becomes positively charged relative to the outside
Innervation
The nerve supply, usually to a specific part of the body.
Innervation example
When a neuron is capable of transmitting messages to an effector organ or receiving information from the sensory organ (innervate that organ)
What are the three main components of a Neuron’s structure?
A cell body (soma)
The dendrites
An Axon
Dendrites and Axon
Neural processes (or Neurites) that extend from the body
Soma
Contains nucleus and most organelles
Soma performs what functions?
Protein synthesis and cellular metabolism and can receive input at synapses
Dendrites
Branch from the cell body
What are the functions of Dendrites?
Receive input from other neurons at specialized junctions (synapses) and have varying branch extensions among neurons
Axon
Sends information and range from 1mm - 1m
What are the functions of the Axon?
Can branch (collaterals), the extent of branching varies among neurons and indicate the amount of communication with other cells
What kind of information do Axons transmit?
Rapidly transmits information over relatively long distances in the form of electrical signals (action potentials)
What is the Specialized structures in the Axon
The Axon Hillock
Axon Hillock
The site where the axon originates from the cell body, and initiate action potentials that are transmitted to the axon terminal
Axon Terminal
The release neurotransmitter on arrival of an action potential
Presynaptic cell
The neuron whose axon terminal is releasing neurotransmitter
Postsynaptic cell
The neuron that receive signal by neurotransmitter in the dendrite or cell body
What are the two basic mechanisms for moving products?
Anterograde transport
Retrograde transport
Anterograde transport
From the Soma to Axon terminal
Retrograde transport
From Axon terminal to Soma
Slow axonal transport
0.5-40 mm/day. Associated with movement of small soluble molecules in the cytosol
Fast Axonal Transport
100-400 mm/day. Associated with movement of vesicles, including synaptic vesicles
Slow and Fast axonal transport
Both involve proteins, microtubules and neurofilaments
Fast axonal transport of vesicles function
Act as tracks for transport molecules
Fast axonal transport of vesicles
Carry a vesicle, and can be a synaptic vesicle, or the vesicle to transport other products from the site of synthesis in the body to the axon terminal
Ion channels in Neurons
The opening or closing of ion channels changes the permeability of the plasma membrane for a specific ion
Leak Channels (or nongated)
Always open
Found in the plasma membrane throughout the neuron and is responsible for resting membrane potential
Voltage-gated channels
Open or close in response to changes in membrane potential
Sodium and potassium channels
Throughout the neuron, but more in the axon (Especially in the axon hillock), necessary for initiation and propagation of action potentials.
Calcium channels
Found in the greatest density in the axon terminal.
When open, calcium enter the cytosol of axon terminal and triggers the release of neurotransmitter
Ligand-gated channels
Open or close in response to a chemical (ligand) binding to a receptor. Synaptic potentials
Location of Ligand-gated channels
Located densely in dendrites and cell body
Structural classes of Neurons
Bipolar, Psuedo-unipolar and multipolar
Bipolar
Sensory neurons with two projections, an axon and a dendrite, coming off the cell body, and functions in the senses of olfaction (smell) and vision
Pseudo-unipolar
A subclass of bipolar neurons. The axon and dendrite projections appear as a single process that extends in two directions from the cell body.
Multipolar
The most common neurons, that have multiple projections from the cell body. One projection is an axon and the others are dendrites.
What are the three classes of neurons?
Afferent Neurons, Efferent Neurons, and Interneurons
Afferent Neurons
Originate in the periphery with sensory receptors (outside the body) , and visceral receptors (inside the body)
Efferent Neurons
Originate in the Central Nervous System, the cell body and dendrites receive synaptic communication from other neurons
Interneurons
Lie entirely in the Central Nervous System, and can communicate with afferent neurons, efferent neurons, or other interneurons
Structural Organization of Neurons in the Central Nervous System
Cell bodies of neurons are often grouped into nuclei, and the axons travel together in bundles known as pathways (tracts)
Structural Organization of Neurons in the Peripheral Nervous System
Cell bodies of neurons are clustered together in ganglia, the axons travel together in bundles known as nerves
Glial Cells Latin meaning
Glue
Glial cells function
Provide structural integrity to the nervous system, chemical and anatomical support that permits neurons to carry out functions, and play important roles in intercellular communication.
What are the four types of Glial cells?
Astrocytes (located in Central Nervous System)
Microglia (located in Central Nervous System)
Oligodendrocytes (located in Central Nervous System)
Schwann cells (located in Peripheral Nervous System)
Oligodendrocytes & Schwann cells
Form an insulating layer of myelin around the axons of neurons, and insulation enables neurons to transmit action potentials more efficiently and rapidly
Myelin
Consists of concentric layers of plasma membranes of oligodendrocytes/schwann cells and reduce leakage of ions across the cell membrane
Oligodendrocytes
Form myelin around axons in the Central Nervous System and sends out projections providing the myelin segments for many axons
Schwann cells
Form myelin around axons in the Peripheral Nervous System and provides myelin for only one axon
Nodes of Ranvier (or nodes)
Gaps within the myelin in the axonal membrane and contains voltage-gated sodium and potassium channels which function in the transmission of action potentials by allowing ion movement across the membrane
Resting Membrane Potential (resting Vm)
At rest, cells have a potential difference across its membrane and inside of the cell is negatively charged relative to the outside while not receiving or transmitting any signals
Resting membrane potential
Neurons is approx -70 mV
All cells, -5mV to -100mV
“The types and numbers of ion channels vary”
Neurons communicate
By generating electrical signals in the form of changes in the membrane potential, and changes trigger the release of neurotransmitter which carries a signal to another cell
Existence of the Membrane Potential
The resting membrane potential is maintained by the NA+/Ka+ pump which balances the electrochemical forces with potassium ion moving out and sodium ions moving in the cell
Graded potential
A relatively small change in the membrane potential produced by some type of stimulus that triggers the opening or closing of ion channels
Synaptic potential
Graded potentials produced in the post-synaptic cell in response to neurotransmitter binding to receptors
Receptor potential
Graded potentials produced in response to a stimulus acting on a sensory receptor
Equilibrium potential
The membrane potential that counters the chemical forces acting to move an ion across the membrane, thereby putting the ion at equilibrium
Electrochemical forces
Causing sodium to continually leak into the cell and potassium to continually leak out of the cell
Leakages
Tend to slowly alter ion concentrations inside the cell, raising the sodium concentration while lowering the potassium concentration
Electrical Signal
Occur in the neurons via changes in membrane potential and are the result of gated channels whether they open or close in response to particular stimuli.
What are the three types of gated ion channels?
Voltage-gated
Ligand (chemically) gated
Mechanically gated
Mechanically gated
Found in sensory or visceral receptors located at the end of afferent neurons and crucial for normal functioning of the Nervous system
Depolarization
A change to a less negative or to a positive potential, the membrane become less polarized
Repolarization
The membrane potential returns to the resting membrane potential following a depolarization
Hyperpolarization
A change to a more negative value, and the membrane become more polarized
What are the types of Electrical Signals?
Graded potential
Action potential
Neural Integration
The particular combination of synaptic inputs-determining factor.
Divergence
A single neuron communicates to several other neurons
Convergence
A single neuron receives communication from several other neurons
In the Neural Integration Convergence
Acts as an integrator cause its adding up all the signals arriving from all active synapses “summation” process
summation
Adding effects of graded potentials
Types of Summation
Temporal, and Spatial
Temporal
Postsynaptic potentials being summed arise at the same synapse
spatial
Postsynaptic potentials being summed arise at different synapse
Excitatory input
A postsynaptic neuron receiving from neurons A and B
Inhibitory input
A postsynaptic neuron receiving from neuron C
Temporal Summation
Action potentials arrive from neuron A.
ESPSs produced in response to the binding of neurotransmitter overlap and sum
Neurons A and B
Are excitatory input meaning adding + membrane potential (mV) value
Neuron C
Is inhibitory input meaning it’s minus - membrane potential (mV) value
Location of Excitatory and inhibitory synapse
Occur at axodendritic and axosomatic synapses
Axoaxonic Synapses
Function as modulatory synapses that regulates the communication across another synapse
Axoaxonic synapse Occurs
In presynaptic facilitation or Presynaptic inhibition
Presynaptic Modulation Neurotransmitter
Binds to receptors on the membrane of the axon terminal of the postsynaptic neuron. Makes a change in calcium levels that enters the axon terminal to respond to an action potential.
The Presynaptic facilitation neurons
Neurons C and E
Neuron E
Enhances the release of neurotransmitters from C.
Increases the strength of the resulting EPSP to threshold. Generate an action potential in neuron X.
Axoaxonic
Excites or inhibits one synapse and is selective on the neuron
Axodendritic/Acosomatic
Ec
Acetylcholine