Nerve Tissue Flashcards
(128 cards)
Nerve Tissue function
-provides rapid and specific communication between organs and body
Neurons
Neuroglia
- highly speacialized cells. Similar to muscle cells they are electrically excitable
- support cells, also called glial cells
Number of Neurons in the body
100,000,000 neurons
Sensory neurons
-gather information from receptors
Interneurons
-form a communicating network between neurons
Motor neurons
-convey impulses from the nervous system to the effector cells
Neuron nucleus
-large, rounded usually euchromatic nucleus with prominent nucleolus(i)
Perikaryon
- cell body
- varies in size between 5-135 micrometers
Rough ER of neurons
- extremely well developed
- forms dense structure, visible in the light microscope called Nissl bodies.
Nissl bodies
-parallel arrays of RER cisternae
Golgi complex of Neurons
Well-developed
-well developed RER and Golgi reflect the need for the neuron to produce membrane and neurotransmitter in large quantities.
Mitochondria
Neurons have many mitochondria
Lysosomes
-usually present in the cytoplasm of neurons
Neurons and centrioles
- neurons usually lack the centrioles
- mature cell is not capable of cellular division
- some neurons retain the centrosome, which may play a role in nucleation of microtubules
Neuroblast
- few neuroblasts that are able to divide and reproduce in small numbers.
- only neurons that are replaced in an adult body on a regular basis are the olfactory neurons
Neuron cytoskeleton
-very well developed and consists of neurofilaments (type of intermediate filaments), microfilaments (composed of actin), and microtubules
Two processes of neurons
Axon and dendrite
-neurons form synapses, which are used for communication with other neurons, muscle cells, and glandular cells
Axon
- one axon per cell
- convey signals from the perikaryon to the next neuron or to the effector cell.
- end with an axon terminal
Size of axon
-usually fairly long (up to 1 meter), and have more or less constant diameter throughout their length
Axon Hillock
- begin from an elevated platform on the perikaryon.
- Nissl bodies are absent from the axon hillock
Myelin sheath
- insulation sheath that covers axons
- allows electric impulse to travel rapidly through the axons.
- abnormalities in the formation of the myelin sheath result in severe disorders
Axolemma
-continuation of the plasma membrane that encloses the axon
Axoplasm
- cytoplasm of the axon
- does not contain Nissl bodies or ribosomes, but has well developed SER.
Axon cytoskeleton
-formed by numerous microtubules and neurofilaments