Unit 5 Lecture Flashcards
What are the two types of cells?
- Nerve Cells (Neurons)
- Involved in the generation and interpretation of ‘Electrical Signals’
- Glial Cells (Neuroglia)
- Support neuronal cell activity
What do the dendrites, cell body, axon, and synapses do?
- Dendrites
- Collect information
- Cell Body
- Process Information
- Axon
- Propagate info
- Synapses
- Transmit info

What are the two components of bioelectricity
Resting Membrane Potential
Action Potential
What is the resting membrane potential and what are the 2 parameters that it depends on?
- Baseline electrical conditions (of ALL cells)
- Depends on 2 parameters
- Transmembrane ion gradients (particularly Na+ and K+)
- Membrane permeability to those ions
What do ion concentrations look like for a resting membrane potential in a muscle cell interior

How is the resting membrane potential maintained?
- Ion gradients!!!
- 3 sodium is pumped out of the cell and 2 potassium are pumped into the cell
- K+ leak channels present in all cells
- Na, K-ATPase develops and maintains steady-state ion gradients for ALL cells
- Notice the inside it negitive outside is positive
- 3 sodium is pumped out of the cell and 2 potassium are pumped into the cell
- Permeability
- K has leak channels (highly permeable)
- Not very permeable to sodium

What are three key points about the resting membrane potential and the intracellular (cytoplasm) vs extracellular areas
- Pumping creates ionic gradient for K+
- K+ “leaks” out, down its concentration gradient, so that the inside of the cells becomes more negative
- Now two kinds of forces push/pull on K+ (chemical and electrical)

What are the 2 opposing forces regarding resting membrane potential?
- Chemical and electrical
- Chemical forces (K+ gradient)
- Tends to push K+ out
- Developed Electrical Force (inside negative)
- Tends to pull K+ in
- Chemical forces (K+ gradient)

What is in a typical cell (includinh neuronal cells)
- Chemical and electrical forces for K+ are nearly in balance
- What does that mean to us?
- Outwardly-directed K+ gradient results in an inside-negative electrical potential
What is the typical electrical potential difference?
Typical value -0.05 volts to -0.1 volts
What is a characteristic of all cells at rest?
K+ dominated inside-negative membrane potential. K+ dominates because it has so many leak channels in the membranes
What does the distribution of ions during a resting membrane potential lookl ike?

What does the distribution of charges look like regarding resting membrane potential?

What can changes in ‘Membrane permeability’ do?
Can produce large changes in the ‘membrane potential’
Membrane permeability to an ion (K+ or Na+) = open channels for that ion
What are keys to manipulation of membrane potential
- Maintain (stable) Na+ and K+ gradients (Na/K ATPase)
- Vary the activity of specific ion channels
How are membrane permeabilities manipulated?
- Ion channels
- Integral membrane proteins
- Channels can be “open” or “closed”
- Some channels are routinely open
- e.g. K-leak channel is the basis of the inside-negative resting membrane potential
- Some channels have their open states regulated

Discuss how some channels have their open states regulated
- Chemically (ligand)-gated channels open when a signal molecule binds to the channel protein (ACh)
- Mechanically-gated channels open when membrane gets stretched
- Voltage-gated channels open when the membrane potential gets less negative ‘depolarized’

What does it mean that neurons are ‘excitable cells’
In Nerve and muscles, can change membrane potential to generate an electrical signal
What is the principal mechanism for a neuronal action potential
Voltage-gated Na+ Channel
What is the first step of the chain of events in the generation of the action potential?
- Local change in membrane potential
- Such local changes can be hyperpolarizing (more negative) or depolarizing (less negative)
- (‘graded’ potentials)

What does an action potential begin with
A local depolarization
Discuss what graded potentials are
- Occur in dendrites and cell body of neuron
- Size varies with strength of stimulus
- Usually generated by chemically and mechanically gated channels
What are the two types of graded potentials?
- Inhibitory Post-Synaptic Potential (IPSP)
- Excitatory Post-Synaptic Potential (EPSP)
What is the second step of the chain of events in the generation of the action potential?
Depolarization to a threshold value induces a population of voltage-gated Na-channels within the local region of membrane to open….
























































