Nervous Tissue Flashcards
Functional categories of neurons
Sensory, Interneurons, Motor
Prominent organelles in neurons
RER, Golgi body, Euchromatin, large nucleolus, mitochondria, Nissl Bodies
Perikaryon
Cell body of a neuron, 5-135 µm
Only neurons that are replaced regularly in the body
olfactory neurons
Axon cell structure
Can have myelin sheath, no nissl bodies, well-developed SER, microtubules & neurofilaments make up the cytoskeleton
Off of what structure does the axon arise from off of the perikaryon?
Axon hillock
Anterograde flow
Uses kinesin to transport things from the perikaryon to the axon
Slow axonal transport
Moves tubular molecules, actin molecules, proteins (things that form neurofilaments)
Fast axon transport
Moves membrane-bound organelles (SER, synaptic vesicles, mitochondria)
Fast retrograde transport
Moves endocytosed things to the perikaryon, uses dynein
Dendritic spines
Where synapses with axonal processes of other neurons are formed
Are dendrites myelinated?
dendrites are NOT myelinated
Dendrite cell structure
Nissl bodies, tapered, branches profusely, rough surface, no myelin sheaths
Types of neurons
Pseudounipolar, Bipolar, multipolar
Pseudopolar neurons
Primary sensory neurons, peripheral and central processes
Typically in dorsal root ganglia and cranial nerve ganglia
Peripheral processes of pseudounipolar neurons
Reaches into the sensory area and transmits its information
Central process of pseudounipolar neurons
Delivers info to the CNS
Bipolar neurons
sensory neurons to major sense organs
Have 2 processes: dendrite and axon
Multipolar neurons
Most common type of neurons, both motor and interneurons
One axon and many dendrites
Golgi type I cells
Long axon multipolar neurons
Large motor neurons in the CNS
Golgi type II cells
Short axon multipolar neurons
Smaller interneurons in the CNS
What ion creates the negative cell membrane potential?
Na+
How do excitatory chemical synapses affect the postsynaptic membrane?
depolarizes the membrane
How do inhibitory chemical synapses affect the postsynaptic membrane?
hyperpolarize the membrane
Presynaptic knob
Contains synaptic vesicles about 40-60nm in diamete w/ neurotransmitters, has Ca++ channels that initiate the movement of synaptic vesicles to the membrane
Synaptic cleft
Space between pre and postsynaptic membrane
Postsynaptic membrane
Receptor sites for the neurotransmitters
High-affinity reuptake
Extra neurotransmitters are endocytosed back into the presynaptic membrane
Degradation of neurotransmitters
Enzymes breakdown neurotransmitters left in the synaptic cleft
What treatment involving neurotransmitters has been shown to help with depression?
Inhibition of the enzyme that breaks down norepinephrine/ inhibition of high-affinity reuptake
Motor-end plate
Neuromuscular junction that uses acetylcholine
Junctional folds
In the sarcolemma of a muscle cells that contain the receptor sites for acetylcholine
Curare toxin
Binds to acetylcholine receptor and acts as a muscle relaxant
Botulinum toxin
Aka Botox, prevents the release of acetylcholine from synaptic vesicles, relaxes the muscle
Myasthenia gravis
Antibodies attack the acetylcholine receptors, weakening the response to stimuli, characterized by extreme muscle weakness
What area does the rabies virus affect?
The virus enters the CNS via synaptic terminals, causing serve inflammation, seizures, and death
Peripheral Nervous System support cell types
Schwann cells and satellite cells
Which cells form the myelin sheaths in the PNS?
Schwann cells
How do the action potentials travel in myelin?
Saltatory conduction
What is present in high numbers in the nodes of Ranvier that perpetuate the action potential?
Na+ channels
How are unmyelinated nerve fibers packed in the PNS?
Multiple nerve fibers surround one Schwann cell
Where are satellite cells mainly found?
Ganglia of PNS surrounding individual cells
What do satellite cells do for neurons?
Create microenvironments, provide electrical insulation/metabolic exchange necessary for neurons
Neuroglia
Forms the intermediate filament cytoskeleton for the cells
Astrocytes
Largest neuronal cell (8-10µm), supports the neuron/vascular structures of the CNS, gradual cytoplasm/large nuclei/numerous mitochondria, processes extend between neurons and blood vessels, forms the blood-brain barrier
Types of astrocytes
Protoplasmic and Fibrous
Protoplasmic astrocytes
Found in grey matter, have perivascular feet along blood capillaries
Fibrous astrocytes
Have more prominent cytoskeletons, are primarily found in white matter
Astrocytomas
Tumors from astrocytes, 20% of all brain tumors, 80% of tumors that originate in the brain
Glial Scar
Formed by astrocytes after brain tissue damage has been done
Oliodendrocysts
The most common neuroglia (6-8µm), Small nuclei/abundant SER/prominent Golgi, form myelin sheaths in the CNS
Multiple Sclerosis
Damage to CNS myelin sheaths via the immune system
