Nervous System Flashcards
Describe the role of the sodium-potassium ATPase pump in establishing and maintaining the resting membrane potential (RMP).
The sodium-potassium ATPase pump actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell, both against their concentration gradients. This maintains the concentration gradients necessary for RMP and contributes a small amount to the negative charge inside the cell by pumping more positive ions out than in.
Explain the difference between a graded potential and an action potential.
Graded potentials are small, localized changes in membrane potential that can be either depolarizing or hyperpolarizing and vary in magnitude with stimulus strength. Action potentials are large, all-or-none changes in membrane potential that propagate along the axon without losing strength and are triggered when the threshold is reached.
What is the significance of the absolute refractory period?
The absolute refractory period prevents the neuron from generating another action potential, regardless of the stimulus strength. This ensures that action potentials propagate in one direction down the axon and prevents summation of action potentials.
How does myelination affect the propagation of action potentials?
Myelination increases the speed of action potential propagation by allowing saltatory conduction. Action potentials “jump” between the nodes of Ranvier, where ion channels are concentrated, rather than occurring along the entire axon membrane as in unmyelinated fibers.
Describe the steps involved in synaptic transmission at a neuronal junction.
An action potential arrives at the axon terminal, causing voltage-gated Ca2+ channels to open and Ca2+ to enter. This triggers the exocytosis of neurotransmitters into the synaptic cleft, where they bind to receptors on the postsynaptic membrane, leading to a graded potential.
Explain the difference between generator potentials and receptor potentials.
Generator potentials are graded potentials that occur in the dendrites of a first-order sensory neuron and directly generate an action potential on the axon of that same neuron. Receptor potentials are graded potentials that occur on specialized receptor cells separate from the sensory neuron, causing the receptor cell to release neurotransmitter onto the dendrites of the sensory neuron.
Distinguish between phasic and tonic receptors, providing an example of each and explaining the adaptive significance.
Phasic receptors respond to changes in stimulus intensity and adapt quickly, decreasing their firing rate with a constant stimulus. An example is the touch receptors in the skin, allowing us to ignore the constant pressure of clothing. Tonic receptors respond to stimulus and maintain a sustained firing rate with a constant stimulus, providing continuous information. An example is proprioceptors, which continuously monitor posture.
Outline the three types of neurons found in sensory pathways.
Sensory pathways typically involve three neurons: a first-order neuron that carries the signal from the receptor to the spinal cord or brainstem, a second-order neuron that relays the signal to the thalamus, and a third-order neuron that carries the signal from the thalamus to the sensory cortex.
Explain the concept of reciprocal inhibition and its role in coordinating movement.
Reciprocal inhibition is the inhibition of somatic lower motor neurons to antagonist muscles during the contraction of an agonist muscle. This ensures smooth and coordinated movements by allowing the agonist muscle to contract while the antagonist muscle relaxes.
Describe the roles of Wernicke’s area and Broca’s area in language.
Wernicke’s area is responsible for language comprehension, allowing individuals to understand spoken and written words. Broca’s area is responsible for motor control of speech production, coordinating the muscles needed for speaking and grammatical structure.
