M2 Topic 3: Neurons Flashcards
(15 cards)
Parts of a neuron
- Cell body (soma)
- Dendrites
- Axon
Cell body (soma)
Where nucleus and most other organelles are located
Dendrites
Receives signals from other neurons or sensory receptors
Axon
Carries the nerve impulse towards another structure
How are neurons classified?
- Structurally (what it looks like)
- Functionally (direction the AP’s travel in)
Structural classifications
Classified structurally according to how many processes extend from the soma of the neuron
- Multipolar neurons = more than two processes extending
- Bipolar neurons = two processes extending
- Pseudounipolar neurons = looks like one extending but actually two extending
Functional classifications
Derived from direction AP is travelling
- Sensory neurons (afferent neurons)
- Motor neurons (efferent neurons)
- Interneurons
Sensory (afferent) neurons
Impulses travel from periphery to the CNS and usually up to a certain part of the brain
- Most are pseudounipolar neurons, some are bipolar neurons
Motor (efferent) neurons
Impulses travel from the CNS out towards the periphery of the body
- All are multipolar neurons
Interneurons
Integrate (process) incoming information from sensory neurons and then elicit a response by stimulating a motor neuron
- Only found in CNS
- All are multipolar neurons
Associated structures which aid neurons
- Myelin sheaths
- Sensory receptors
Myelin sheaths
Wrapping of fat that encircles axon to provide it with electrical insulation
- Helps speed up transmission rate of AP’s (neural impulse) along axon, and messages are conveyed more quickly around body
- Oligodendrocytes (for CNS) and Schwann cells (for PNS) are types of glial cells that make myelin sheath, which wrap layers of their PM around axon to form fatty covering
Sensory receptors
Help sensory neurons detect stimuli
- Can be part of the sensory neuron’s dendrites, or a completely different structure
3 types of sensory receptors
- Encapsulated endings
- Free ‘nerve’ endings = neuron with bare dendrites
- Specialised receptor cells
Nerves vs neurons
Neuron
- Cell within nervous tissue
Nerves
- Largely a PNS structure (no nerves in CNS, with exception of two nerves in the head)
- Made up of axons of many neurons, often with myelin sheaths that surround these axons, connective tissue sheaths that bind the axons together, and blood vessels that supply these cells/tissues
- Considered an organ
