1QQ#11 for 10:30 1. Retrograde axonal transport limits the rate of axonal regeneration to 1-2 mm/day. 2. The cell body of an afferent neuron is located in the ventral root. 3. Microglia are a component of the blood- brain barrier. 4. The neural crest consists of cells, some of which will become somatic motoneurons. Revise two of the following misleading statements. Your revision cannot consist of a “not” statement.
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1QQ#11 for 10:30 1.Retrograde axonal transport limits the rate of axonal regeneration to 1-2 mm/day. 2.The cell body of an afferent neuron is located in.
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1QQ#11 for 10:30
1. Retrograde axonal transport limits the rate of axonal regeneration to 1-2 mm/day.
2. The cell body of an afferent neuron is located in the ventral root.
3. Microglia are a component of the blood-brain barrier.
4. The neural crest consists of cells, some of which will become somatic motoneurons.
Revise two of the following misleading statements. Your revision cannot consist of a “not” statement.
1QQ#11 for 11:30
1. Anterograde axonal transport limits the rate of axonal regeneration to 200 mm/day.
2. The cell body of an interneuron is located in the dorsal root ganglion.
3. Microglia adjust the concentration of ions and neurotransmitters in the interstitial fluid surrounding neurons of the CNS.
4. The neural crest consists of cells, some of which will become interneurons.
Revise two of the following misleading statements. Your revision cannot consist of a “not” statement.
Topics covered with board drawings
Axonal regeneration
• Peripheral vs central• Role of growth cones• Timecourse of recovery• Wallerian degeneration• Schwann cells and
Schwann tubes• CNS and spreading
necrosis
Cortical vesicle exocytosis during fertilization leads to envelope elevationA, prior to fertilization (left), the proteinaceous vitelline coat of the sea urchin egg of Lytechinus pictus
is not visible in this differential interference contrast image.
Big questions:1)How do cells generate a resting membrane potential?2)What causes changes in the membrane potential?3)How do cells use these potentials? i.e. What is their purpose?
Fig. 06.09
Fig. 06.10a
There is a concentration gradient favoring the diffusion of Na+ and K+ through the selectively permeable membrane which has ion channels only for potassium.
At the start, is there an electrical driving force?
Fig. 06.10b
With K+ channels open, K+ diffuses down its concentraiton gradient, leaving behind CL- ions which are not permeable through the membrane. As more and more K+ move to the left, the compartment they leave becomes more and more negatively charged.
Is there an electrical driving force?
Fig. 06.10c
Fig. 06.10d
Soon, the accumulation of negative charges seriously impeded the diffusion of K+ as the electrostatic force builds up in opposition to the concentration driving force.
Eventually, the electrostatic force that impedes diffusion of K+ is exactly equal to the driving force favoring diffusion based on a concentration gradient. When these two driving forces are equal and opposite, the membrane potential reaches an equilibrium at which the voltage is called
So which compartment corresponds to intracellular fluid?
E ion+ = 61/Z log ([conc outside]/ [conc inside])
E K+ = 61/1 log (5/150)E K+ = -90 mV
The Nernst Equation
• If the membrane is permeable to ONLY ONE ion species and you know the concentrations on both sides of the membrane, use the Nernst Equation to calculate the membrane potential.
Nernst potential for X = 61/Z log [Outside ] / [Inside]
• Equilibrium potentials and Resting Membrane potential.
Comprehensive list of topics at http://webs.wofford.davisgr/bio342/test1study2012.htm
Electrical and concentration gradient driving forces for Sodium and Potassium
How does the membrane potential change if 1) permeability to sodium increases2) Permeability to potassium increases
Why is resting membrane potential closer to EK than ENa?
What would happen to membrane potential if suddenly PNa
became very great?
Size and Direction of Arrows show driving forces!
The G-H-K Equation!S 8
How can the membrane become suddenly more permeable to Na+?
The Goldman Hodgkin Katz Equation
• If you know the concentrations of ALL permeable ions and their relative permeabilities, you can calculate the membrane potential using the GHK Equation.
S 9
At RMP, some Na+ leaks in, some K+ leaks out.
S 10
Na+ K+ ATPase maintains the concentration gradients across
cell membranes
Animation of the Pump
What would happen to membane potentials and concentrations of Na+ and K+ if cells didn’t have this pump?
S 11
Animations of the Origin of Resting Membrane Potential
Animation of Resting Membrane Potential (single ion)
YouTube animation of Na-K-ATPase, Sodium Co-transporter, and K Leak channels
Origin of Resting Membrane Potential and intracellular recording
S 12
S 13
Which ion moving in which direction (into or out of cell) is responsible for depolarization and overshoot? Which ion moving in
which direction (into or out of cell) is responsible for repolarization and hyperpolarization?
Can the membrane potential go more negative than -90 mV?
Increase PK+
Increase PNa+
S 14
Increase PK+
How do ions get across the membrane? Ion channels!