Nervous System Flashcards
What are the cells of the nervous system?
Neurons and glial cells
What are the four basic types of neurons?
Sensory, motor, interneurons and neurosecretory
What are somata?
The cell bodies of sensory neurons
What is the difference between the somata of sensory neurons and the somata of all other neurons?
The somata of sensory neurons are peripheral and lie adjacent to the sense organs. The somata of all other neurons are located within the ganglia.
What is meant by motoneurons and interneurons being unipolar?
Each somata gives rise to a single elongate primary neurite.
How do insect neurons compare to vertebrate neurons?
Insect neurons somata do not have dendritic branches like vertebrate’s neurons do and insect sensory neurons lie adjacent to the sense organs whereas vertebrates sensory neurons lie within the ganglia.
What are the junctions contained in neurites?
Presynaptic and postsynaptic junctions
What innervation do insect muscle fibres have and how does it compare to vertebrates?
Insect muscle fibres have multiterminal innervation - due to each motor neuron giving rise to a number of neuromotor junctions (motor end-plates) on an individual muscle cell as well as other muscle cells. This contrasts with vertebrates where each muscle cell has a single motor end-plate at the end of one neuron.
What are the functions of glial cells?
To support the neurons, aid in their nutrition and form a ‘blood-brain’ barrier around neurons.
What is the purpose of the blood-brain barrier in glial cells?
Insect blood is poorly regulated and is in direct contact with tissues and organs and in some cases, the ionic composition of the blood is such that it would be inhibitory to nerve impulses if it came in contact with nerves. It sometimes contains high concentrations of potassium ions for example which interfere with nerve impulses. Therefore, the barrier keeps them separate.
Do glial cells protect muscle tissue?
No.
What is the neural lamella?
The chemically permeable thickened membrane that binds ganglia.
What is the outer cell layer called in ganglia? How does it function?
The neuroglia, which consists of a few ‘braclet-shaped’ glial cells fastened together side-by-side by tight junctions. These junctions prevent chemical diffusions between cells and help the neuroglia form a outer chemical barrier around the ganglion.
What is the cortex of the ganglion?
The somata of all neurons lying peripherally beneath the neuroglia.
What is the central portion of the ganglion called?
The neuropile
