WEEK 3 Flashcards
The nervous system can be broken down into the ____ system and the ____ system
Central nervous system
Peripheral nervous system
The central nervous system includes which organs? The Peripheral nervous system includes?
CNS: Brain and spinal cord
PNS: Cranial nervous 1-10, spinal nerves, the Ears, eyes, sensory organs of smell, sensory organs of taste, and sensory receptors located throughout the skin, joints, muscles, and viscera
Peripheral nerves are regenerative, while CNS cells are considered ____
post mitotic
Fill in:
1. There are two types of cells in the nervous system ___ and ___ .
- ____ are excitable cells while ____ are not
- Neurons ; Glia
- Neurons; Glia
Name the types of Glia found in the CNS
Ependymal cells
Oligodendrocytes
Astrocytes
Microglia
Names the types of glia found in the PNS
Satellite Cells
Schwann Cells
Describe Microglia
- CNS glia cell
- is an immunocompetent phagocytic cell. helps by fighting off foreign objects/material, debris
- overactive presence of microglia can lead to disease
- arise from macrophages outside the cell
True or false.
Astrocytes are the most abundant glial cell
True
Describe Astrocytes
- a CNS glia cell
- the most abundant glia cell
- restricted to the Brain and spinal cord
- important in forming Blood brain barrier
- can adopt different shapes
- regulate neurotransmitter levels
describe oligodendrocytes
- a CNS glia cell
- produce myelin in CNS
describe Schwann cells
- a PNS glia cell
- myelinated peripheral axons
- involved in repairing damaged peripheral nerve fibers
Ependymal cells
- a CNS glia cell
- form a continuous epithelial sheet that lines the ventricles and central canal of the brain and spinal cord
Excitable cells include
Neurons
Muscle cells
Pancreatic beta cells(endocrine cells)
True or false. Sensory neurons detect physical stimuli and relay that information to the CNS while motor neurons carry information from the CNS to specific muscles and organs
True
Fill in.
Sensory neurons are a type of _____ neuron
pseudounipolar neuron
Fill in.
Motor neurons are a type of _____ neuron
multipolar neuron
Describe interneurons
- Connect sensory and motor neurons
- are neither a sensory or motor neuron
- housed entirely within the CNS
- is a type of multipolar neuron
Fill in.
___ houses the metabolic machinery of the cell. it is also a site of integration of incoming signals
Cell body/Soma
Describe dendrites
- delicate
- branched processes that extend off the soma
- locus of synaptic input to the neuron
- another site of signal integration
- brings information to soma via graded potentials
Signal integration occurs in which two places on a neuron
- Soma
- dendrite
describe axons
- a long process that extends from the soma.
- conducts action potentials away from the soma and toward the presynaptic terminal
describe presynaptic terminals
- where synaptic transmission between a neuron and its target cell occurs
Where are action potentials generated?
The Axon hillock
a neuron that has a single process and extends away from the cell body is a _____
unipolar neuron
How do dendrites conduct graded potentials
- through ligand gated ion channels and GPCR
what are axon collaterals?
Axon branches. Usually found in pseudounipolar neurons
describe bipolar neurons, and multipolar neurons
bipolar:
- have two processes that extend from the cell body
- a single dendrite
- a single axon
multipolar:
- have multiple dendritic processes that extend from their cell body
- a single axon
- usually found in muscles
describe psuedounipolar neurons
- common in somatic sensory system
- have a single process that extends from the cell body. this splits into a dendrite that goes to the periphery (skin) and an axon that goes to the CNS
what is the order of information flow in a neuron?
- Signal reception
- Signal integration
- Signal conduction
- Signal transmission
what initiates the action potential in a neuron
- a change in membrane potential
What does a synapse refer to?
the junction between a presynaptic neuron and postsynaptic target
where does signal conduction occur?
On the axon as the action potential is conducted to the axon terminal
What causes a membrane potential?
- the concentration of different ions in the intracellular and extracellular fluid compartments
- the plasma membrane’s permeability to different ions
what is needed to generate and maintain a membrane potential?
- electrical gradient (charge difference)
- chemical gradient (concentration different)
- Leak channels essential
- Na-k ATPase pump
How does Na-K ATPase contribute to to the membrane potential
- Actively transports Na+ out of the cell and K+ into the cell
- Helps maintain the ionic gradients
- Counters effects of the leak channels
the membrane potential of a cell is always measured with respect to what?
- A reference electrode
Increasing the number of negative charges inside the cell, would cause the membrane potential to become _____
Hyperpolarized
Increasing the number of positive charges (or decreasing the amount of negative charges) inside the cell would cause the membrane potential to ____
depolarize
Fill in. To maintain the concentration gradients needed for resting membrane potential _____ and _____ are essential
- leak channels
- Na-K ATPase
the relative permeability of ion is calculated relative to ____
the permeability for potassium (K+)
Fill in
Pk=
Pna=
Pcl=
Pk= 1
Pna= 0.04
Pcl= 0.45
Leak channels are more permeable to K+ and least permeable to Na+
what is the ratio of K+ leak channels to Na+ leak channels
4 :1
[Na+ ] is ____ outside and _____ inside the cell.
[K+] is ______ outside and ____ inside the cell.
What is the Nernst Equilibrium equation
R= gas constant
T= temp in kelvin
F= Faradays constant
z= valence of the ion
What does the Nernst equation depend on? What does it not depend on?
the concentration gradient and valence of the ion
does not depend no the channel properties or permeability of the ion
The Nernst equilibrium equation assumes ______
permeability
When the concentration gradient is balanced by the electrical gradient_____
there is no net flux of ions across the membrane
True or false.
The Nernst equilibrium potential can be calculated for every ion that has an ion channel through the plasma membrane.
True.
Fill in.
The Nernst equilibrium defines _____ across a membrane that will _______ a particular concentration gradient of an ion
the voltage (electrical potential) ; balance
True or false
A lot of ions have to move to set up the potential; concentration gradients are
significantly disturbed in achieving an equilibrium
False.
few ions have to move to set up the potential. the concentration gradients are not significantly disturbed
What will happen if a membrane is permeable to only one type of ion?
the resting membrane potential will move the equilibrium potential of that ion.
The resting membrane potential is largely determined by ___
K+
*there are minor contributions from Na+ and Cl-
permeability of an ion is proportional to what? If there are no open ion channels for a specific ion, its permeability is?
the number of open ion channels for that ion; 0
What is the equation for the Goldman-Hodgkin-Katz equation?
Vm= membrane potential
Pk= permeability of potassium
the GHK equation depends on what?
the concentration gradients for each ion and their relative permeabilities
Fill in.
The greater an ions permeability, the greater its contribution to ____
the membrane potential
What happens to the resting membrane potential if an ion is very permeable?
It will be weighted more towards that ion’s Nernst equilibrium potential
At rest, Vm is dominated by what ion?
Potassium
True or False.
There will be a flux of ions across the membrane of any ion for which the membrane
potential is not at the equilibrium potential
True.
When is the Vm stable?
When no ions are at their potential
when is the total net flux of ions across the membrane zero
When the membrane potential stable
Vdf (driving force) is the difference between the ______ and the ______
membrane potential and
equilibrium potential for an ion
What is the driving force equation
A cation that has a (-) driving force flows in what direction
Inward
A anion that has a (+) driving force flows in what direction
Inward
a cation that has a (+) driving force flows in what direction
outward
a anion that has a (-) driving force flows in what direction
outward
What happens when the Na-K ATPase stops working
the sodium and potassium gradients dissipate
What would happen if Vanadate or Ouabain inhibited the Na-K ATPase?
the concentration gradient would dissipate and would not be able to establish or maintain membrane potential for action potential and other physiological processes.
normal resting membrane potential is essential for what physiological processes?
Neurons
cardiac muscle
smooth muscle
skeletal muscle
endocrine cells
the concentrative capacity of secondary active transporters
SGLT depends on Na-K ATPase and ____
low intracellular Na+ concentration
SGLT is considered a ____ pump
electrogenic pump. It is also a symporter or cotransporter.
SGLT is sensitive to resting membrane potential. This means what?
If you change resting membrane potential, you change the driving force thus changing glucose absorption.
GLUT transports glucose out of the cell to ____
the intracellular space. (basement membrane > interstitial fluid > capillary)
As the membrane potential decreases what happens to the glucose concentration
the ratio of Glucose(inside) to Glucose(outside) increases. meaning more glucose goes into the cell
As depolarization occurs what happens to the concentration of the glucose
Concentration of glucose inside decreases
as polarization occurs what happens to the concentration of glucose
Concentration of glucose inside increases
Vm < Vrev
Na+ and solute will go in
Vm > Vrev
Na+ and solute will go out
action potential in excitable cells is described as what
a brief and reversible change in their membrane polarization
How do non-excitable cells respond to depolarizing and hyper polarizing stimuli
by producing graded changes in their membrane potential
In excitable cells, during action potential the membrane potential depolarizes from ____ to ____
-70 mV to + 50mV
True or false.
action potentials are all or nothing events
True
What are the different time scales for motor neurons, skeletal muscle, and cardiac ventricles
motor neurons: 2 msec
skeletal muscle: 5 msec
Cardiac ventricles: 200 sec
Of motor neurons, skeletal muscle, and cardiac ventricle which of the three has the most negative Em and is the most long lasting?
Cardiac Ventricle
Describe how the following are opened:
- voltage gated ion channel
- ligand gated ion channels
- mechanical gated ion channels
Voltage gated- open by change in voltage (depolarization)
Ligand gated- opened by signal molecules binding to the protein
mechanical gated- open by mechanical forces.
who developed the Hodgkin-Huxley model
Sir Alan Lloyd Hodgkin and Sir Andrew Huxley
What is the basis of information processing and transfer in the nervous system
action potential
overshoot describes what during the depolarization phase
- the reverse in sign of the membrane potential. essentially going from negative to positive.
what are the phases of action potential
- Rising phase or depolarization phase
- Repolarization phase
- afterhyperpolarization phase
voltage gated ion channels are important for ____
the different phases of action potential
every voltage gated ion channel must have the following:
- a pore with selectivity filter
- a gated mechanism (this can be a voltage, ligand or mechanical force).
what does the selectivity filter of a voltage gated ion channel do?
- it uses amino acids that can use their carbonyl oxygens to act like a cage to strip the ion of water
what amino acid code makes for a strong K+ channel
G-Y-G
when you introduce more channels what happens to the selectivity of K+
it will reduce, and more ions will be able to pass through
What does the Hodgkin-Huxley model of the action potential say about Na+ channels
- each Na+ channel has 3 identical rapidly responding activation gates (M-gates)
- each Na+ channel contains a single slower responding inactivation gate (H-gate)
the probability of a Na+ gate being open is dependent upon what?
- the voltage across the membrane
the probability of the Na+ activation gates being open increases ___
increases with depolarization of the membrane potential
the probability of the Na+ inactivation gates being open decreases
decreases with depolarization
At rest the m-gate is ___ and the H-gate is ___
m-gate is closed
h-gate is open
When the Na+ channel is open the m-gate is _____ and the H-gate is ____
m-gate is open
h-gate is open
when the Na+ channel is inactive the m-gate is ____ and the h-gate is _____
m-gate is open
H-gate is closed
the depolarization phase of the action potential is an example of what type of feedback
positive feedback
it is called the Hodgkin cycle
What is the Hodgkin cycle (depolarization phase)
- open voltage gated Na+ channels
- Pna increases
- influx of Na+ ions
- Membrane depolarization
What happens at the peak of the depolarization phase
- Voltage gated Na+ channels rapidly inactivate
- voltage gated K+ channels slow activate. K+ leaving contributes to the repolarization phase
what did the Hodgkin-Huxley model say about voltage gated K+ channels
- voltage gated K+ channels have slower kinetics
- voltage gated K+ channel slowly activate. using 4 n-gates
- these K+ gates remain open for as long as the membrane is depolarized.
- when the membrane depolarizes the n-gates close and the K+ channel can no longer conduct a current
