TOPIC III: Nervous System I – Neurons, Impulse generation & Transmission Flashcards
What is the primary function of the nervous system?
To monitor internal and external changes, integrate information, and generate precise responses
What are neurons?
Excitable cells that can generate and propagate electrical impulses
What initiates an electrical impulse in a neuron?
Stimulation of the cell body or dendrites
What are electrochemical gradients?
Differences in ion and molecule concentration between intracellular and extracellular fluids used for signaling
Which ions are important for the electrical properties of cells?
- K+
- Na+
- Cl-
- Ca++
- Large negatively charged organic ions (org-)
What is the role of the Na+/K+-ATPase pump?
Maintains concentration gradients of Na+ and K+ by pumping 3 Na+ out and 2 K+ in
What is the resting membrane potential (RMP)?
The charge difference across the cell membrane in a resting cell, approximately -70 mV
Which ion is primarily responsible for establishing the RMP?
K+
What occurs during depolarization?
Membrane potential becomes more positive due to Na+ influx
What are graded potentials (GPs)?
Small changes in RMP caused by stimulus, resulting in depolarization or hyperpolarization
What is the threshold potential for triggering an action potential (AP)?
-55 mV
What is the all-or-none principle of action potentials?
If threshold is reached, an AP is produced; if not, no AP occurs
What is the absolute refractory period?
A period during which no action potential can be generated, regardless of stimulus size
What is the role of myelination in action potential propagation?
Increases speed of propagation by allowing saltatory conduction at nodes of Ranvier
What are the characteristics of Type A fibers?
Large diameter, myelinated, propagate APs at ~130 m/sec
What neurotransmitter is commonly involved in excitatory postsynaptic potentials (EPSPs)?
Acetylcholine (ACh) or glutamate
What is the result of inhibitory postsynaptic potentials (IPSPs)?
Hyperpolarization of the neuron
Fill in the blank: Graded potentials are _______ signals.
short-distance
What happens during the repolarization phase of an action potential?
Na+ channels close and K+ channels open, causing K+ to diffuse out
What is the difference between graded potentials and action potentials in terms of summation?
GPs can summate; APs cannot
What is a postsynaptic potential (PSP)?
A graded potential created on the postsynaptic membrane due to neurotransmitter binding
What triggers the release of neurotransmitters at the synaptic junction?
An action potential arriving at the axon terminal
What is the main neurotransmitter released at the neuromuscular junction?
Acetylcholine (ACh)
