Chapter 2: Structures and Functions of Cells of the Nervous System Flashcards
The CNS is made up of the ______ and the _______.
brain; spinal cord
Sensory/motor neurons gather information
Sensory
Sensory/motor neurons control the muscles
Motor
Four main parts of a neuron:
Soma, Axon, Dendrites, Terminal buttons
Which part of the neuron contains the nucleus?
Soma
Which part of the neuron receives messages from other neurons?
Dendrites
Which part of the neuron secretes neurotransmitters?
Terminal buttons
Define axoplasmic transport
An active process that propels substances along microtubule “tracks” that run inside the length of the axon
Anterograde/retrograde axoplasmic transport propels substances from the soma to the terminal buttons.
Anterograde
Anterograde/retrograde axoplasmic transport propels substances from the terminal buttons to the soma.
Retrograde
Which protein helps to accomplish anterograde axoplasmic transport?
Kinesin
Which protein helps to accomplish retrograde axoplasmic transport?
Dynein
True or False: Anterograde axoplasmic transport is considerably slower than retrograde axoplasmic transport.
False, retrograde is about two times slower than anterograde.
What are the three types of glial cells in the CNS?
Astrocytes, oligodendrocytes, microglia
Role of astrocytes:
physically support neurons by acting like glue, clean up debris in brain via phagocytosis, produce chemicals and provide nutrients
Role of oligodendrocytes:
Provide support to axons, produce myelin sheath
Role of microglia:
Phagocytosis, immune system, inflammatory reactions to bad microorganisms
Schwann cells are located in the CNS/PNS
PNS
Role of Schwann cells:
support axons, produce myelin, digest dying axons and help regrow axon
What is the blood-brain barrier?
A selectively permeable barrier with no gaps that regulates the composition of extracellular fluid and keeps messages from being disrupted
What is the weak part of the blood-brain barrier called?
Area Postrema
The area postrema controls ______ by detecting toxic substances entering the blood
vomiting
Describe a basic communication within a neuron when grabbing a BURNING HOT thing
When sensory dendrites are stimulated, it sends messages down the axon to terminal buttons, which release neurotransmitters, which excite the motor neuron, causing the muscle cells to contract.
The resting potential inside an axon is ____mV
-70
What is membrane potential?
Any difference in charge across the membrane
When there is an increase in membrane potential, ___________ occurs.
Hyperpolarization
When there is a decrease in membrane potential, _________ occurs.
Depolarization
When the inside charge becomes more negative and the outside charge becomes more positive, then _______ occurs.
Hyperpolarization
When the inside charge becomes more positive and the outside charge becomes more negative, then ________ occurs.
Depolarization
Each neuron has a threshold of excitement, which is _________.
the set point that must be reached in order to produce an action potential
An action potential is a burst of rapid ______ followed by _________.
depolarization; hyperpolarization
The electrical charge of the membrane potential is the result of a balance between two opposing forces, namely _______ and _______.
diffusion; electrostatic pressure
What is diffusion?
Molecules moving from high to low in order to achieve equilibrium
What is electrostatic pressure?
The force exerted by the attraction/repulsion of ions. Opposites attract; likes repulse.
True or False: The forces of diffusion and electrostatic pressure contributed by the intracellular fluid and the extracellular fluid ions give rise to the membrane potential.
True.
Organic anion
A-
Chloride ion
Cl-
Sodium ion
Na+
Potassium ion
K+
A- are located only in the _________ fluid because the membrane is impermeable to them.
intracellular
Diffusion pushes CI- ___ and electrostatic pressure pushes CI- ___.
in; back out
Diffusion pushes Na+ ___ and electrostatic pressure pushes Na+ ___
in; in
Diffusion pushes K+ ___ and electrostatic pressure pushes K+ ___
out; back in
What does the sodium-potassium pump exchange?
Three sodium ions for two potassium ions
The overall effect of the sodium-potassium pump:
Keeps the intracellular fluid concentration of Na+ out while slightly increasing K+ inside
How to cause an action potential:
Briefly increase the membrane permeability to Na+ (allowing these ions to rush into the cell), immediately follow this with a transient increase in the permeability of the membrane to K+ (allowing them to rush out of the cell). This is achieved via ion channels.
What determines the permeability of the membrane?
Ion channels
Both sodium and potassium channels are _______-dependent and can only be opened by changes in the ______ _______.
Voltage; membrane potential
Because potassium channels are not as sensitive as sodium channels, they open earlier/later.
Later
All-or-none law
the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fiber will fire.
Rate law
High firing rate = strong intensity (bowling ball)
Low firing rate = light intensity (feather)
True or False: Myelinated segments completely close the axon off from extracellular fluid
True, so there is no inward flow of Na+ in these areas.
