Neurons and muscles - Nervous system Flashcards
What are the two basic types of cells in the nervous system?
Neurons (communicate using electrical potentials) and Glial cells (support neurons but do not produce electrical impulses)
What is a neuron?
A specialized cell that communicates using electrical potentials, characterized by irritability (unstable voltage across the membrane) and conductivity (ability to change voltage)
What is the function of glial cells?
They provide structural and functional support to neurons, including nutrient supply, waste removal, and maintaining the ionic environment
What are the two main divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
What is a nerve?
A bundle of axons that transmits signals between different parts of the body
What are the three main types of neurons?
- Sensory neurons (afferents): Bring information into the nervous system
- Motor neurons (efferents): Carry information away from the nervous system to muscles or glands
- Interneurons: Process and integrate information within the nervous system
What are the structural classifications of neurons?
- Multipolar neurons: Have multiple connections (e.g., interneurons).
- Bipolar neurons: Have two connections (e.g., sensory neurons).
What is the axon’s function?
It passes electrical signals in one direction to transmit information
What is the function of Schwann cells?
They form the myelin sheath in the Peripheral Nervous System (PNS), which helps in electrical conduction and neuron regeneration
What are Nodes of Ranvier?
Gaps between Schwann cells that allow faster nerve signal transmission and aid in neuron regrowth
What are the three types of electrical potentials in neurons?
- Resting potential: Baseline electrical charge of the neuron
- Graded potential: Small changes in membrane voltage due to stimuli
- Action potential: A large, all-or-nothing electrical impulse that propagates along the neuron
What is the resting membrane potential?
The electrical charge difference across a neuron’s membrane when inactive, typically -70mV (polarized state)
What is the role of the Na+/K+ ATPase pump in resting potential?
It actively pumps 3 Na⁺ ions out and 2 K⁺ ions in, maintaining the ion concentration gradient using ATP
What are the key ion concentrations in neurons?
- Inside the neuron (ICF): High K⁺ concentration.
- Outside the neuron (ECF): High Na⁺ concentration.
What are electrochemical gradients?
The combined force of concentration and electrical gradients that influence ion movement
How do Na+ and K+ move across the membrane?
- Na+ moves in, driven by concentration and electrical gradients.
- K+ moves out, driven by concentration gradient but partially opposed by electrical gradient.
What is the equilibrium potential of Na+ and K+?
- Na⁺ equilibrium potential: +60mV.
- K⁺ equilibrium potential: -90mV.
Why is the resting potential closer to -70mV?
The membrane is more permeable to K⁺, leading to a negative resting potential
What are the two types of electrical impulses in neurons?
- Graded potentials: Small, localized voltage changes proportional to stimulus strength.
- Action potentials: Large, all-or-nothing impulses that propagate along the axon.
What is depolarization?
A positive shift in membrane potential due to Na⁺ influx
What is repolarization?
A negative shift in membrane potential due to K⁺ efflux
What are voltage-gated ion channels?
Channels that open or close in response to voltage changes, allowing ion flow to generate action potentials
Where do action potentials originate?
In the axon hillock, where the neuron integrates incoming signals
What are the steps of an action potential?
- Resting state (-70mV): All voltage-gated channels closed.
- Depolarization (+30mV): Na⁺ channels open, Na⁺ enters.
- Repolarization (-70mV): K⁺ channels open, K⁺ exits.
- Hyperpolarization (-90mV): Excess K⁺ leaves before channels close.
- Return to resting state (-70mV): Na+/K+ ATPase restores ion balance.
