Nervous Tissue, Types & Properties of Neurons Flashcards
The nervous tissue originates from the…
…ectoderm
What are glia cells?
Glia cells serve to support neurons; they are not neurons
Approximate number of neurons in the human brain:
10E11
Two common histological procedures are:
- tissue fixation
- staining
System classification of neurones:
- Sensory neurone (detects stimuli; first neurone in the input-output path)
- CNS neurones (process signals; lie between sensory & motor neurones)
- Motor neurone (controls the output; last neurone in the input-output path)
Functional classification of neurones (always relative to a particular structure):
- Afferent neurone (first neurone in a sequence of neurones along the signal propagation pathway) - Interneurone (neurone between the entry point and the output) - Efferent neurone (output neurone)
Structural classification of neurones:
- Unipolar (has only one axon and no dendrites; this is typical for sensory neurones) - Bipolar (has one axon and one branching dendrite) - Multipolar (has one axon and many branching dendrites; majority of CNS neurones are of this type)
Morphological classification of neurones:
- Pyramidal cell
- Stellate cell
- Basket cell
- Granule cell
- Chandelier cell, etc. etc.
Do neurones reproduce?
Neurones do not reproduce (in the sense that they do not divide).
A typical neurone has…
…a cell body, dendrites, and one axon
Myelinated segments of axons are separated by…
…nodes of Ranvier
The typical resting potential of a neurone:
Cytoplasm is negatively loaded relative to the extracellular liquid (-70mV)
The resting potential is maintained by…
…the sodium-potassium pump (Na+, K+)
How does the sodium-potassium pump function?
It moves 3 Na+ out and 2 K+ in at the expense of 1 molecule of ATP
What is the threshold for creating an action potential?
-55 mV
Depolarization is mainly due to…
…the inward current of Na+ ions
Repolarization is mainly due to…
…the outward current of K+ ions
Repolarization is followed by…
…hyperpolarization
Only which parts of the plasma membrane can generate action potential?
Only those that haven’t been recently excited.
The speed at which myelinated axons conduct action potential:
up to 120 m/s
Axon terminals connect to dendrites via…
…chemical synapses
Electrical synapses are called:
gap junctions
Gap junctions are…
…connections between two dendrites. They are fast and bidirectional but produce weak signal.
