Neuronal Anatomy Flashcards
to understand the anatomy of neuron
What is a neuron?
A neuron is a specialized cell of the nervous system that receives, processes, and transmits information through electrical and chemical signals. It is the basic functional unit of the nervous system responsible for communication within the body.
What are the three main parts of a neuron?
- Cell body (soma)
- Dendrites
- Axon
What is the cell body (soma) of a neuron?
The cell body or soma is the central part of the neuron containing the nucleus and most of the cell’s organelles. It is responsible for maintaining the cell’s life processes and synthesizing materials needed for dendrites and axons.
What are dendrites?
Dendrites are branched extensions of the neuron that receive signals from other neurons. They increase the surface area of the cell body to maximize the number of synaptic contacts that can be made with other neurons.
What is an axon?
An axon is a long, slender projection of a neuron that conducts electrical impulses away from the cell body to target cells. Axons can extend from less than a millimeter to more than a meter in length.
What is the myelin sheath?
The myelin sheath is a fatty insulating layer that surrounds many axons, formed by specialized cells called oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. It increases the speed of electrical impulse transmission.
What are nodes of Ranvier?
Nodes of Ranvier are gaps in the myelin sheath that occur at regular intervals along myelinated axons. They allow for saltatory conduction, where the action potential “jumps” from node to node, increasing the speed of nerve impulse transmission.
What is an axon terminal?
Axon terminals are small branches at the end of an axon that form synapses with other neurons, muscles, or glands. They contain synaptic vesicles filled with neurotransmitters for chemical signal transmission.
What are synaptic vesicles?
Synaptic vesicles are small membrane-bound spheres found in axon terminals that contain neurotransmitters. When an action potential reaches the axon terminal, these vesicles fuse with the cell membrane and release neurotransmitters into the synaptic cleft.
What is the synaptic cleft?
The synaptic cleft is a tiny gap between the presynaptic axon terminal of one neuron and the postsynaptic membrane of another cell. Neurotransmitters diffuse across this space to transmit signals from one neuron to another.
What is the function of neurotransmitters?
Neurotransmitters are chemical messengers released from axon terminals that travel across the synaptic cleft and bind to receptors on the postsynaptic cell, either exciting or inhibiting the receiving cell
What is the difference between myelinated and unmyelinated axons?
Myelinated axons are covered by a myelin sheath, which increases the speed of impulse conduction through saltatory conduction. Unmyelinated axons lack this insulating layer and therefore conduct impulses more slowly but continuously along their entire length.
What is an action potential?
An action potential is a brief reversal of electrical polarization of a neuron’s membrane, resulting from rapid changes in membrane permeability to sodium and potassium ions. It is the basic mechanism for signal propagation along axons.
What is the axon hillock?
The axon hillock is the region where the axon emerges from the cell body. It has a high concentration of voltage-gated sodium channels and is typically the site where action potentials are initiated.
What are the three types of neurons based on their function?
- Sensory neurons (afferent): Transmit signals from sensory receptors to the CNS
- Motor neurons (efferent): Transmit signals from the CNS to muscles and glands
- Interneurons: Connect neurons within the CNS and process information
What are the four types of neurons based on their structure?
- Multipolar neurons: Multiple dendrites and one axon (most common in CNS)
- Bipolar neurons: One dendrite and one axon (found in sensory organs)
- Pseudounipolar neurons: One process that divides into central and peripheral branches (sensory neurons)
- Unipolar neurons: One process extending from the cell body (rare in vertebrates)
What is the resting membrane potential of a neuron?
The resting membrane potential is the electrical potential difference across a neuron’s membrane when it is not transmitting signals, typically around -70 millivolts (inside negative relative to outside). It is maintained by the sodium-potassium pump and differential permeability of the membrane
What is the direction of signal transmission in a typical neuron?
Signals typically travel in one direction in neurons: received by dendrites → processed in the cell body → transmitted down the axon → released at axon terminals to target cells.
What is the difference between the central nervous system (CNS) and peripheral nervous system (PNS)?
The CNS consists of the brain and spinal cord, while the PNS includes all neural tissue outside the CNS. The PNS connects the CNS to organs, limbs, and external environment.
What are neural circuits?
Neural circuits are interconnected neurons that work together to perform specific functions. They process information through converging, diverging, or feedback pathways and form the basis of more complex neural networks in the nervous system.
