Chapter 3 #1 Flashcards
What is the classic pattern of neural function?
Info flows within a neuron via electrical signals (action potentials) and passes between neurons through chemical signals (neurotransmitters)
Neurophysiology
The study of the life processes of neurons
Polarized
Exhibits a difference between the electric charge inside and outside of a cell.
All living cells are more negative on the inside than the outside. T or F?
True!
Ion
Electrically charged molecules contained in a neuron
Anions
Negatively charged ions. These are the majority of large protein ions within the cell that can’t exit.
Cations
Positively charged ions in a neuron
Intracellular fluid
Watery solution inside the neuron where ions are dissolved. Also known as cytoplasm
Extra cellular fluid
Fluid in between cells (interstitial fluid) surrounds the cell membrane and contains dissolved ion
Cell membrane
The lipid bilateral that ensheathes a cell
Microelectrode
Especially small electrode used to record electrical potentials in living cells
Resting potential
A difference in electrical potential across the membrane of a nerve cell during an inactive period
What is the difference in electrical potentials across a resting neuron’s membrane?
-50 to -80 millivolts (mV)
Millivolts (mV)
A thousandth of a volt
Ion channel
A pore in the cell membrane that permits the passage of certain ions through the membrane when the channels are open
Potassium ion (K+)
A potassium atom that carries a positive charge because it has lost one electron
Selective permeability
Property if the membrane to allow some substances to pass through but not others (K+ channels)
Diffusion
Tendency of molecules to move from areas of high concentration to lower concentration until a uniform concentration is achieved
Electrostatic pressure
The propensity of charged molecules to move, via diffusion, towards areas with the opposite charge.
What are the two main forces that drive ions in and out of the neuron?
Diffusion and electrostatic pressure
Sodium potassium pumps
Energetically expensive mechanism that pushes sodium ions out of a cell and potassium ions in.
What is the ratio at which the sodium potassium pumps each ion?
Three Na+ for every 2 K+
Sodium ion (Na+)
A sodium atom that carries a positive charge because it has lost one electron
Equilibrium potential
The point at which the movement if ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction
The pump and diffusion create a high intracellular concentration of which ion?
K+
The pump and diffusion create a high extracellular concentration of which ion?
Na+
Hyperpolarization
Increase in membrane potential, the inside of the neuron becomes more negative
Depolarization
Brings the membrane potential closer to zero, making the potential of the inside more like the outside
What happens when a hyper polarizing stimulus to the membrane?
Passively mirrors the stimulus pulse.
Graded response
The greater the stimulus the greater the response
Local potential
An electrical potential that is initiated by stimulation at a specific site spreads passively across the membrane and get weaker as they spread away from the point of stimulation
Threshold
The stimulus intensity that is just adequate to trigger an action potential at the axon hillock
How far must a cell become depolarizer before it reaches the threshold?
Around -40 mV or so
Action potential
“Spike”. Rapid reversal of the membrane potential that momentarily makes the inside of he membrane positive with respect to the outside
Is the action potential actively or passively reproduced?
Actively
All or none property
The amplitude of the action potential is independent to the size of the stimuli. It fires fully or not at all.
How does the size of the stimuli effect the action potential?
With stronger stimuli more action potentials are produce but the size is the same
After potential
The positive or negative change in membrane potential following an action potential.
Knee jerk reflex
Stretching of the tendon beneath the knee leads to an upward kick of the leg
Electroencephalogram (EEG)
Records gross electrical activity of the brain via large electrodes placed on the scalp
Event related potential/ evoked potential
Averaged EEG recordings measuring brain responses to repeated presentations of a stimulus
Epilepsy
A brain disorder marked by major sudden changes in the electrophysiological state of the brain that are referred to as seizures
Grand mal seizure
Epileptic seizure in which nerve cells fire in high frequency bursts, usually accompanied by involuntary rhythmic contractions of the body
Petit mal seizure
“Absence attack” seizures with spike and wave EEG and involves a loss of awareness and ability to recall surrounding events
Complex partial seizures
A type of seizure that doesn’t involve entire brain and can cause a variety of abnormal behaviors
Aura
The unusual sensations or premonition that may precede the beginning of an epileptic seizure.
