Neurons and Glial cells Flashcards
What is the basic unit of organization of the nervous system? How do these cells communicate with other cells?
What percentage of overall cells of the CNS do these basic cells make up?
Neurons are the basic unit. They communicate with other neurons and organs via synaptic transmission.
Neurons make up 10-20% of the cells within the CNS.
What part of a neuron contains the nucleus and genetic information for protein synthesis?
What is Nissl substance?
The cell body or soma contains the nucleus and genetic info for protein synthesis.
Nissl substance is the endoplasmic reticulum (ER) of the cell body.
How do materials move within the neuronal cell body?
Can materials move from within the neuronal cell body to outside? How about from outside into the cell?
Materials move along microtubules and neurofilaments via “axoplasmic transport”.
Yes, materials can move from within neuronal cell bodies to the outside (“anterograde”), and they can even move “retrogradely” from outside into the neuron (ex: muscle cell).
The surface area of dendrites accounts for what percentage of total neuronal surface area available for synaptic contact?
What other part of the neuron accounts for most of the remaining 10%?
The surface area of dendrites accounts for over 90%.
The cell body comprises most of the remaining 10%.
Together the cell body and dendrites are where most signals for synapses are received.
What do axons do?
Axons carry action potentials away from the cell body and may have considerable branching.
Which types of axons conduct action potentials at a higher velocity: myelinated or unmyelinated axons?
Myelinated axons conduct action potentials at a higher velocity.
What type of cells forms myelin?
What do you call the space between myelin-forming cells? What types of channels exist at that space?
Glial cells form myelin.
The space between glial cells are called Nodes of Ranvier. These spaces have voltage-gated Na+ and K+ channels for propagation of action potentials.
What are axon collaterals?
They are branches of axons which enable the neuron to activate more than one effector cell at a time (such as activating another neuron, muscle cell, or gland).
Axon terminals contain what chemicals inside of them?
Axon terminals contain neurotransmitters, which are stored in synaptic vesicles.
Can a neurotransmitter be excitatory for some cells and inhibitory for others?
Yes, the post-synaptic receptor for a NT on a cell is what ultimately determines the action relationship between cell types.
Ex: ACh generates EPSP for skeletal muscle, but does IPSP for cardiac.
“Spatial and temporal summation of inputs also determines output of the post-synaptic cell.”
Ion channels that allow negatively charged ions to flow into the cell do WHAT to the cell?
These ion channels hyperpolarize or inhibit the cell (IPSP).
Typically Cl- channels will inhibit.
Ion channels that allow positively charged ions to flow into the cell do WHAT to the cell?
These ion channels depolarize or excite the cell (EPSP).
Typically Na+ channels will excite.
What are the four types of neurons?
- Unipolar neurons (found in invertebrates - not discussed further)
- Pseudounipolar neurons
- Bipolar neurons
- Multipolar neurons
Psuedounipolar neurons
- What function do they serve?
- How many axons do they have?
- They make up peripheral sensory afferents (tendon organs, muscle spindles, and cutaneous and joint receptors). Their soma is a first order sensory neuron.
- They have two axons (1 central and 1 peripheral).
Be sure to be able to identify an image of one.
Bipolar neurons
- What function do they serve?
They function in special sensory systems (sight, smell, balance, hearing, taste)
Be sure to be able to identify an image of one.
