Chapter 8 Flashcards
What type of neurons belong in the Afferent and Efferent pathways of the PNS?
Afferent: Sensory neurons
Efferent: Motor neurons
Where does the interneuron fit in, in the CNS?
It is in between the sensory neurons and the motor neurons. The interneuron takes the information from the sensory input (afferent neurons) to the motor output (efferent neurons). IN THE CNS NOT PNS
Name effectors of the somatic nervous system (1)
Skeletal muscles
Name effectors of the autonomic nervous system (4)
Smooth muscles, Cardiac muscles, Glands, Adipose tissue
Describe the function of of oligodendrocytes of the CNS
They are neuroglial cells that form the myelin sheath in the CNS and wrap around the axon of the neuron and form layer of plasma membrane. They are pad shaped
Describe the function of Schwann cells of the PNS
They are neuroglial cells that form the myelin sheath in the PNS. They coil their plasma membrane around the axon of the nerves. They incorporate their cell bodies in the myelin sheath. Protect against extracellular fluid
How are oligodendrocytes and Schwann cells similar and how are they different?
Similar: They are both neuroglial cells that form a myelin sheath around the axons of the neurons
Differences
oligodendrocytes: Wrap around the axon of a neuron and extend into a pad shape and form layers of the plasma membrane. IN THE CNS NEURONS
Schwann Cells: They coil (make a swirly) around the axon of the nerves. They also incorporate their cell bodies in LAST LAYER of the myelin sheath. The nucleus and cytoplasm are on the OUTSIDE layer of the schwann cell and help in cell regeneration. IN THE PNS NERVES
What roles do astrocytes (5 things) and microglia play in supporting neurons of the CNS?
Astrocytes: Maintains the blood brain barrier
- framework for the CNS
- repairs damaged neural tissue
- helps with embryonic neural development
- controls the interstitial fluid environment (ion regulation, Rapid transport between capillaries/neurons and glucose, controlling capillary blood volume, recycling neurotransmitters, and enhance/suppress synapse communication)
Microglia: They are phagocytic cells in the CNS that collect debris and help with neural development
What is the blood brain barrier?
Astrocytes send chemical signals to the capillaries walls to form tight junctions to make them less permeable so it can keep stuff in the blood capillaries or to keep them out. IT IS A CHEMICAL BARRIER
What is the difference between chemically, voltage, and mechanically gated channels?
Chemically: Open when it binds to a specific receptor
Voltage: Opens when there is a change in voltage in the inside of the cell. More positive the channel closes. More negative it opens
Mechanically: Opens in the response to pressure or stretch of the membrane. PHYSICAL PRESSURE
Where are the chemically, voltage, and mechanically gated channels located on the neuron?
Chemicall: Cell bodies and dendrites
Voltage: Axons on the cell membranes
Mechanically: Sensory dendrites
What stimulates chemically, voltage, and mechanically gated channels to open?
Chemically: Opens when it binds to a specific receptor
Voltage: Opens when there is a change in voltage in the inside of the cell. More positive the channel closes. More negative it opens
Mechanically: Opens in the response to pressure or stretch of the membrane. PHYSICAL PRESSURE
What is the electrochemical gradient of Na+ and K+ (which way do they flow if allowed?
Na+: Chemically Na+ wants to flow in because it has a higher concentration on the outside than the inside
Electrically: It also wants to flow to the inside because the inside of the cell is more negative than on the outside of the cell
K+: Chemically K+ wants to flow out of the cell because it has a higher concentration on the inside of the cell than on the outside
Electrically: It wants to stay on the inside of the cell because he inside of the cell is more negative than on the outside of the cell. GOES SLOWLY OUT OF THE CELL
IT USUALLY FOLLOWS THE CHEMICAL GRADIENT BECAUSE IT IS STRONGER
How fast does Na+ and K+ flow in the electrochemical gradient?
Na+: IT FLOWS IN FAST
K+: IT FLOWS IN SLOW
What is the resting membrane potential?
the electrical potential difference across a cell membrane when the cell is at rest, meaning it is not actively sending electrical signals
What is the charge on the inside and outside of the plasma membrane in the resting membrane potential?
Inside: More negative
Outside: More positive
What is the ion concentration of Na+ and K+ like on the inside and the outside of the plasma membrane in the resting membrane potential?
Inside: Na+ = low levels, K+ = High levels
Outside: Na+ = High levels, K+ = low levels
Why should we consider membrane ion permeability in the resting membrane potential?
Because K+ is more permeable so it goes out more easily than Na+ can come in. For every 25 K+ ions that go out, only 1 Na+ ion comes in.
What system returns a neuron to the resting membrane potential (homeostatic state) following an action potential?
The sodium potassium pump (ATPase)
What is the difference between a graded potential and an action potential?
Graded: It is initiated by a stimulus
- strength determined by how much charge enters the cell
- travels short distances
- it loses strength as it travels through the cell
- occurs in cell bodies and dendrites
- axon terminal drops a stimulus on the neuron body
Action: Large all or nothing stimulus that goes all along the axon and is dependent on voltage-gated channels.
- only in muscle cells and axons
- does not lose strength over distance
What is temporal summation?
It is where one neuron inputs the same stimulus over and over again to the synapse of another neuron which causes an action potential.
How does temporal summation contribute to an action potential?
The multiple inputs from the one neuron build up on eachother and it causes the action potential
What is spatial summation?
when multiple stimuli are applied simultaneously to different areas of a neuron, resulting in a cumulative effect on the membrane potential
How does spatial summation contribute to action potential?
increasing the probability that a neuron will reach its threshold potential and fire an action potential by releasing different inputs and helping them overlap to get an action potential
When a cell is at rest in a neuron are the Na+ channels opened or closed?
Closed
When the cell is at rest in a neuron what is the Na+ flow?
There is no flow
When the neuron is in the depolarization phase are the Na+ channels opened or closed?
opened
When the neuron is in the depolarization phase what is the Na+ flow?
Fast into the cell
When the neuron is in the depolarization phase what is the voltage range?
-70mv to +30mv
When the neuron is in the repolarization phase what is the flow of Na+?
No flow at all
When the cell is at rest in a neuron are the K+ channels opened or closed?
Closed
When the cell is at rest in a neuron what is the K+ flow?
There is no flow
What is the transmembrane potential in a neuron when the cell is at rest?
It is even (the same)
When the neuron is in the repolarization phase are the Na+ channels opened or closed?
Closed
When the cell is at rest in a neuron what is the voltage range inside of the neuron?
-70mV
When the neuron is in the depolarization phase what is the transmembrane potential?
Positive (inside the cell)
When the neuron is in the repolarization phase what are the K+ channels doing?
THEY ARE OPENING
When the neuron is in the depolarization phase are the K+ channels opened or closed?
closed
When the neuron is in the depolarization phase what is the flow of K+?
No flow
When the neuron is in the repolarization phase what is the K+ flow?
They are going out slow
When the neuron is in the repolarization phase what is the voltage range?
+30mV to -70mV
When the neuron is in the repolarization phase what is the transmembrane potential?
More negative (on the inside)
When the neuron is in the hyperpolarization phase are the Na+ channels opened or closed?
Closed
When the neuron is in the hyperpolarization phase what is the flow of Na+?
NO FLOW
When the neuron is in the hyperpolarization phase what is the K+ flow?
Out slow
When the neuron is in the hyperpolarization phase are the K+ channels opened or closed?
Opened
When the neuron is in the hyperpolarization phase what is the voltage range?
-70mV to -90mV
When the neuron is in the hyperpolarization phase what is the transmembrane potential?
More negative than resting
How does the neuron cell get back to the resting voltage range after hyperpolarization?
The sodium potassium pump helps it get back to the -70mV (ATPase)
What is responsible for the movement of an action potential down an axon when threshold is met?
the opening of voltage-gated sodium channels on the axon hillocks
What is the difference between continuous and saltatory propagation?
Continuous: It is where the action potential in the first segment spreads the information/sodium to the segment next to it. Then that segment sends it to the segment next to it. So, in short it sends the information to one segment at a time. And it flows in one direction. SLOWER BECAUSE IT LEAKS OUT
Saltatory: The myelinated axons resist the flow of the ions in the axon. So, this causes the ions to jump from node to node in the axon in one direction. FASTER
How does myelin effects continuous and saltatory propagation?
continuous: It makes the process go slower because it has no myelin so the sodium leaks out.
saltatory: It affects by resisting the flow of the ions. So it causes the ions to jump from node to node.
What are the the 6 steps in the cholinergic synapse?
- An action potential reaches the axon terminal or presynaptic membrane
2 . Extracellular calcium ions enter the synaptic terminal through voltage-gated calcium channels.
calcium ions trigger vesicles to fuse with presynaptic membrane to release acetylcholine in the synaptic cleft by exocytosis
3.Acetylcholine diffuses across the synaptic cleft and binds to postsynaptic membrane receptors
- Sodium gated channels open and the post synaptic membrane becomes permeable to sodium causing depolarization. This allows transmission of a graded potential that if it reaches the threshold it can create an action potential (depends on the amount of neurotransmitter)
- Acetylcholinesterase (AChE) inactivates ACh breaking it down into acetate and choline through hydrolysis
- Re uptake of choline by the presynaptic membrane occurs and can be reused, acetate is absorbed and metabolized by surrounding tissues or cells
What is the location of voltage gated Ca2+ channels in a synapse?
In the membrane of the presynaptic terminal
What is the location of ionotropic Na+ channels in a synapse
On the postsynaptic membrane
What is the location of AChE in a synapse?
Postsynaptic neuromuscular junctions
What is the location of Acetylcholine in a synapse?
It is in the presynaptic vesicles then it is released into the synaptic cleft (the neurotransmitter)
What is the location of synaptic vesicles in a synapse?
In the presynaptic axon terminal until they are released
What is the location of Na+ ions in a synapse?
The synaptic cleft (outside of the synapse)
What is the location of neurotransmitters in a synapse?
In the synaptic vesicles in the presynaptic axon terminal
What is the function of voltage gated Ca2+ channels in a synapse?
To let calcium in and bind to the vesicles to draw them closer to the plasma membrane in the presynaptic synapse
What is the function of ionotropic Na+ channels in a synapse?
When a neurotransmitter binds to it (like acetylcholine) it allows a lot of sodium ions to flow in and excite the postsynaptic cell
What is the function of AChE in a synapse?
It breaks down ACh to acetate and choline through hydrolysis
What is the function of Acetylcholine in a synapse?
It excites the cell and helps start depolarization by binding to the postsynaptic membrane receptors (ionotropic Na+ channels)
What is the function of Synaptic vesicles in a synapse?
They are filled with neurotransmitters and release them when they are told to/ brought to the plasma membrane
What is the function of Na+ ions in a synapse?
It uses a symport to create an electrochemical current to pull choline back into the presynaptic neuron
What is the function of Neurotransmitter in a synapse?
It carries a signal to the postsynaptic receptor and binds to it and triggers a response in the postsynaptic cell
What is the difference between divergence and convergence?
Divergence: One presynaptic neuron branches out and affects a larger number of postsynaptic neurons (smaller to bigger)
Convergence: Many presynaptic neurons give input to a smaller number of postsynaptic neurons (bigger to smaller)
Name some examples of divergence and convergence
Divergence: Visual information that your eyes get
Convergence: Motor neurons when they are working on control of breathing
What is the GABA cell do in synapses?
It inhibits the action potential from happening (depolarization) and does hyperpolarization
The cerebral cortex is gray matter what is it made out of?
Neuron cell bodies
What makes the neuron cell bodies gray?
the perikaryon
What makes the perikaryon gray?
The nissi cell bodies
Where is gray matter at (how can we tell where it is at)?
It is wherever there is clusters of cell bodies
Determine if these structures in a neuron are gray matter or white matter?
Perikaryon
Myelin
Cell body
Axon
Perikaryon- gray matter
Myelin- White matter
Cell body- Gray matter
Axon- White matter
What is the difference in structure between multipolar, Unipolar, Bipolar, and Anaxonic neurons?
Multipolar- Normal looking neuron. cell body is on one end and with one single axon and axon terminals at the end
Unipolar- One single elongated axon with the cell body to the side of it
Bipolar- They have two processes with the cell body in between them (in between the dendrites and axon terminals)
Anaxonic- May all be dendrites axons are not obvious
What type of neuron are motor neurons in the PNS. multipolar, Unipolar, Bipolar, and Anaxonic neurons?
MULTIPOLAR
What is axoplasmic transport?
It is movement of materials between the cell body and synaptic terminals IT CAN GO BOTH WAYS
What is anterograde flow?
It is materials carried toward the synapse (mitochondria) GOES ONE WAY
What is retrograde flow?
It is material that is carried toward the cell body (aged organelles) IT GOES ONE WAY
Do oligodendrocytes and schwann cells belong to the PNS OR CNS?
oligodendrocytes - CNS
schwann- PNS
How many potassiums leave the cell compared to how many sodiums come in? (how does this cause the inner membrane to be more negative than the outside of the cell)
K+ 25 to Na+ 1 more positives leaving than coming in
Is the plasma membrane more permeable to K+ or Na+?
K+
What are the 4 steps of graded potentials?
- Stimulus triggers a neuron cell body or dendrite
- depolarization (sodium enters the cell causing a shift in charges within the cell more positive on the inside than outside
- Na+ current (spread of sodium ions produces a local current )
- Na+ current decay ( depolarization decreases with distance away from the stimulus where it was released)
What is the refractory period?
Where each section of the membrane will not respond to additional stimulus during the action potential as it is going
What are the 6 steps of the action potential?
- Resting potential ( sodium and potassium gated channels closed and got -70mV)
- Graded potential reaches threshold (stimulus initiates depolarization and passes the threshold and opens the voltage gated sodium channels)
- Depolarization (Sodium channels activate and rush into the cell and inner membrane becomes more positive)
- Repolarization (The inner membrane reaches +30mV which closes the voltage gated sodium channels to close and activates potassium channels to open and inner membrane reaches -70mV)
- Hyperpolarization (K+ channel remain open and the inside of the cell becomes -90mV)
- Resting potential (voltage gated K+ close and it turns back to its -70mV the resting membrane potential by the sodium potassium pump
Would you use chemically, voltage, or mechanically gated channels in graded potentials?
Chemically gated channels
What would cause a graded potential to become an action potential?
- It needs to hit the threshold potential (-55mV) at the trigger zone (in the axon hillocks)
Why doesn’t an action potential travel both directions?
- Due to the refractory period. Which is where each section of the membrane which will not respond to more stimuli while the action potential is going until it reaches its resting potential.
What does Saxitoxin inhibit in an action potential? And what part of the process of an action potential does it inhibit?
Voltage-gated sodium channels. And It inhibits the depolarization and proliferation of the action potential.
Determine if these ion’s movements depolarize or hyperpolarize
Na+
K+
Ca2+
Cl-
Na+ : Depolarize
K+ : Hyperpolarize
Ca2+ : Depolarize
Cl- : Hyperpolarize
What is the function of satellite cells and where are they found (PNS or CNS)?
Surrounds ganglia cell bodies (PNS)
What is the function of Astrocytes cells and where are they found (PNS or CNS)?
Blood brain barrier (CNS)
What is the function of oligodendrocyte cells and where are they found (PNS or CNS)?
Forms myelin sheath (CNS)
What is the function of schwann cells and where are they found (PNS or CNS)?
Forms myelin sheath (PNS)
What is the function of ependymal cells and where are they found (PNS or CNS)?
Forms cerebrospinal fluid (CNS)
What is the function of Microglia cells and where are they found (PNS or CNS)?
Phagocytic cell (CNS)
