Chapter 4 Flashcards
Channel
Opening in a protein embedded in the cell membrane that allows the passage of ions.
Gate
Protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not others.
Pump
Protein in the cell membrane that actively transports a substance across the membrane.
How many pairs of chromosomes foes the human somatic cell contain?
23
Allele
Alternate form of a gene; a gene pair contains two
Wild type
Refers to the most common phenotype or genotype in a population
Tay-Sach’s Disease
Inherited birth defect caused by the loss of genes that encode the enzyme (Hex A) necessary for breaking down lipids in the brain
Huntington’s Disease
Hereditary disease characterized by chorea and progressive dementia
Down Syndrome
Chromosomal abnormality resulting in mental retardation and other abnormalities, caused by extra chromosome 21.
Transgenic Animal
Genes from one species is introduced into the genome of another species and passed along and expressed in subsequent generations.
Diffusion
Movement of ions from an area of higher concentration to an area of lower concentration through random motion
Concentration Gradient
Different in concentration of a substance among regions of a container that allow the substance to diffuse from an area of higher concentration to an area of lower concentration.
Voltage Gradient
Difference in charge between two regions that allows a flow of current.
Resting Potential
Electrical charge across the cell membrane in the absence of stimulation.
A store of potential energy produced by a greater negative charge on the intracellular side relative to the extracellular side
What charged particles are in higher concentration in the intracellular fluid?
Protein anions and K+ ions
Which charged particles are in higher concentration in the extracellular fluid?
Cl- and Na+ ions
Graded Potential
Small voltage fluctuations in the cell membrane restricted to the vicinity on the axon where ion concentration change to cause a brief increase or decrease in electrical across the cell membrane.
Hyperpolarization
Increase in electrical charge across a membrane.
Usually due to the outward flow of K+
Depolarization
Decrease in electrical charge across a membrane.
Usually due to the inward flow of Na+ ions.
Action Potential
Large, brief reversal in the polarity of an axon.
Threshold Potential
Voltage on a neural membrane at which an action potential is triggered by the opening of Na+ and K+ voltage sensitive channels.
-50 millivolts relative to extracellular channels.
Voltage-Sensitive Channel
Gated protein channel that opens or closes only at specific membrane voltages
Absolutely Refractory
The state of an axon in the repolarizing period during which a new action potential cannot be elicited because gate 2 of sodium channels, which is not voltage sensitive is closed.
Nerve Impulse
Propagation of an action potential on the membrane of an axon.
Relatively Refractory
The state of an axon in the later phase of an action potential during which increased electrical current is required to produce another action potential.
A phase during which potassium channels are still open.
Nodes of Ranvier
The part of an axon that is not covered by myelin
Saltatory Conduction
Propagation of an action potential at successive nodes of ranvier.
Saltatory means “jumping” or “dancing”.
Excitatory Postsynaptic Potentials
Brief depolarization of a neuron membrane in response to stimulation making the neuron more likely to produce an action potential.
Inhibitory Postsynaptic Potentials
Brief hyperpolarization of a neuron membrane in response to stimulation making the neuron less likely to produce an action potential.
EPSPs are associated with the opening of
Sodium channels
IPSPs are associated with the opening of
Potassium channels
Temporal Summation
Graded potentials that occur at approximately the same time on a membrane are summed.
Spatial Summation
Graded potentials that occur at approximately the same location and time on a membrane are summed.
Where is the action potential initiated?
At the axon hillock
Back Propagation
Reverse movement of an action potential into the dendritic field of a neuron.
Postulated to play a role in plastic changes that underlie learning.
Stretch-Sensitive Channels
Ion channel on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse.
Transmitter-Sensitive Channel
Receptor complex that has both a receptor site for a chemical and a pore through which ions can flow.
