Block 2 - Nerve Tissue Flashcards
How is the extra plasma membrane removed for the presynaptic knob membrane?
Through clathrin-coated vesicles via endocytosis
Why are neurons known as electric capacitors?
The voltage across their plasma membrane is not constant and therefore they conduct signals via electricity down their axons.
What are the 5 morphological differences bewtween an axon and a dendrite?
Axon - no Nissl bodies, myelin sheath, constant diameter, restricted branching, smooth surface
Dendrite - Nissl bodies, no myelin sheath, tapered, branches profusely, rough surface
How many neurons are contained in the body, on average?
100,000,000
What are the two major components of nerve tissue?
Neurons and Neuroglia (glial cells)
What are the three functional categories of neurons?
Sensory, interneurons, and motor
What type of cell lines the ventricles of the brain and produce/absorb CSF?
Ependymal cells
What is absent from the axon hillock?
Nissl bodies
Describe a neuron’s nucleus
Large, rounded typically with a euchromatic nucleus and prominent nucleolus
How are neurotransmitters deactivated in the synaptic cleft?
Recapture or degradation
What two processes are found in pseudounipolar neurons? How do they work together?
Peripheral process collects information and Central process delivers it to central nervous system
Which cells form a lipid layer surrounding PNS axons and envelop unmyelinated axons?
schwann cells
What 4 supports cells are found in the CNS?
Astrocytes
Oligodendrocytes
Microglial cells
Ependymal cells
With high-affinity reuptake aside, how are the other 20% of neurotransmitters broken down?
Through enymes associated with the synpatic membrane. Ex. acetylcholine broken down into acetate and choline
What are two types of somesthetic receptors? Where are each found?
Free nerve endings - mediate pain
Encapsulated nerve endings - Meissner’s corpuscle, Pacinian corpuscle, etc.
How was can action potentials travel down an axon?
120 m/sec
What are two types of anterograde transport? How long does each one take?
Slow axonal transport and fast axonal transport
Slow: 1-6mm/day
Fast: 100-400mm/day
Where does an axon begin from the cell body?
The axon hillock
What are two types of astrocytes? Where are they found?
Protoplasmic astrocytes found in gray matter, numerous short branching processes called perivascular feels along blood capillaries.
Fibrous astrocytes have prominent cytoskeleton and are found in white matter. Have fewer processes with less branching
How does botulinum (neurotoxic) affect the axon terminal of neurons?
Prevents release of acetylcholine from synaptic vesicles
Where are satellite cells found?
In ganglia of PNS, surrounding individual cell bodies of neurons. The provide pathways for metabolic exchange and provide electrical insulation
Are ependymal cells true epithelial tissue?
No, while they are a form a simple cuboidal, they have no basil lamina. Covered in microvilli
Describe the steps in a chemical synapse
1) An action potential reaches the axon terminal
2) This causes opening of Ca++ channels
3) Ca++ in the axon temrinal causes the release of neurotransmitters into the synaptic cleft
4) These neurotransipers bind to post synaptic membrane proteins and cause local depolarization
What are two types of sensory nerve endings?
Special sense nerve endings (smell, sight, hearing, and equilibrium)
Somesthetic receptors
What is the role of astrocytes?
Moving metabolic substances between blood and nerve cells, forming the BBB.
Numerous mitochondria and large nuclei
What are the two major types of synapses?
Electrical and Chemical