Neurology Flashcards
Astrocytes (Glial Cell)
Work in healing, tissue repair; regulate ion concentrations, synapse formations and more; Create a supportive framework for neurons - VERY DIVERSE!
Ogliodendrocytes (Glial Cell)
Form and maintain myelin in the CNS
Microglia (Glial Cell)
CNS macrophages; Important immune system workers of the CNS
Ependymal Cells (Glial Cell)
Create cerebral spinal fluid in the CNS
Schwann Cells (Glial Cell)
Create myelin in the PNS
What does amitotic mean?
It doesn’t divide
Why do neurons need a lot of glucose and have a lot of ATP?
They have a very high metabolic rate
Are neurons the most abundant cell in the CNS?
No, glial cells are.
What is the function of an afferent neuron?
Transmit information INTO the central nervous system from receptors at their peripheral endings
What is the function of an efferent neuron?
Transmit information OUT of the central nervous system to effector cells, particularly muscles, glands, or other neurons
Where are interneurons located?
Entirely within the CNS
Where is an afferent neuron located?
Cell body and long peripheral process of axon - PNS
Short central process of axon - CNS
Where is an efferent neuron located?
Cell body, dendrites, a small segment of the axon - CNS
Majority of the axon - PNS
Which neuron accounts for greater than 99 percent of all neurons?
Interneurons
If axons are severed, can they repair themselves?
It depends; Only if the damage occurs outside of the CNS and does not affect the neuron’s cell body
How quickly does axon regrowth occur?
Only 1 mm per day
What happens (at the cellular level) with a crush injury to the spinal cord?
Apoptosis (cell death) of the oligodendrocytes (myelin-producing cells)
What is the Resting Membrane Potential?
The difference in the charge between the outside of the cell and the inside of the cell
How is membrane potential established?
Neurons use a Na+/K+ pump to pump 3 Na+’s OUT for every 2 K+’s IN (creates a relatively negative interior)
What happens during depolarization?
Na+ channels open, Na+ comes in, and the interior cell becomes less negative
What happens during Summation?
The EPSP’s and the IPSP’s add up to a depolarization of 15mV or more, threshold potential has been reached
What happens at Threshold potential?
Sodium channels are open; signal fires
What are the steps of an Action Potential?
- Resting Membrane Potential
- Threshold Reached
- Depolarization - Na+ fly into cell
- Na+ channels close (signal can’t go backwards), slower K+ channels open
- Membrane Repolarizes
- Hyperpolarization (makes it even more difficult for signal to transmit backwards)
- K+ channels close, Na+ channels are reactivated
How do Lidocaine, Procaine, and Marcaine inhibit an action potential?
By blocking the voltage-gated Na+ channels
What is the absolute refractory period?
When the plasma membrane cannot respond to another stimulus (another action potential cannot be sent at this time)
What is the relative refractory period?
When another action potential can be sent ONLY if it’s strong enough to overcome hyperpolarization AND the normal amount of depolarization
Where do action potentials occur?
The nodes of Ranvier
What is saltatory conduction?
- When myelin acts as an insulator that allows ions to flow between segments rather than along the entire length of the membrane
- This results in increased velocity of neuronal conduction
What are three benefits of myelin?
- Add speed
- Reduce metabolic cost
- Save room in the nervous system because axons can be thinner
What are synapses?
When nerves reach out and almost touch each other
How can synapses pass information?
- Chemically
2. Electrically
Can synapses be excitatory and inhibitory?
Yes (depends on what neurotransmitter is being used)
What happens during an electrical synapse?
Pre and post synaptic cells are connected via gap junctions
What happens during a chemical synapse?
- Pre-synaptic neurons release neurotransmitters from their axon terminals
- Neurotransmitter binds to receptors on post-synaptic neurons
Where are neurotransmitters produced and stored?
In the vesicles of the axon terminal
What steps occur during docking of the vesicles and release of neurotransmitters?
- Action potential reaches terminal
- Voltage-gated calcium channels open
- Calcium enters axon terminal
- Neurotransmitter is released and diffuses into the cleft
- Neurotransmitter binds to post-synaptic receptors
- Neurotransmitter is removed from synaptic cleft
What makes it possible for the vesicles to bind to the plasma membrane?
SNARE proteins
How is the neurotransmitter released?
Through exocytosis
What is the function of autoreceptors?
- Neurotransmitters will bind to autoreceptors and turn off further release from pre-synaptic cell
- Build-in break system
- Negative feedback!
- Autocrine cell signaling
How are Neurotransmitters removed from the synapse?
- Diffusion of the transmitter from the cleft
- Degredation of the transmitter by enzymes
- Reuptake into the pre-synaptic cells for reuse
- Removal of the receptors in the post-synaptic cell’s membrane
Which neurotransmitter is ALWAYS the first signaler on efferent pathways to the peripheral nervous system?
Acetylcholine
What enzyme is responsible for breaking down Acetylcholine into AcCoA and Choline?
Acetylcholinesterase (AChE)
Which neurotransmitters are made from the amino acid tyrosine?
- Dopamine
- Epinephrine
- Norepinephrine
Which neurotransmitters are important in the Sympathetic Nervous System?
Norepinephrine and Epinephrine
If dopamine, epinephrine, and norepinephrine aren’t taken back up into the pre-synaptic neuron, how are they destroyed?
By monoamine oxidase (MAO)
Which neurotransmitter is made from the amino acid Tryptophan?
Serotonin
This neurotransmitter acts more like a modulator than a true transmitter.
Serotonin
Serotonin excites what pathway?
Muscle
Serotonin inhibits what pathway?
Sensory
What are Endogenous Opioids?
Short polypeptides (15 to 25 amino acids long)
How are Endogenous Opioids different from other transmitters?
Made in the cell body, put into vesicles, and transported all the way down the axon for release
How are Endogenous Opioids broken down?
Peptidases
“Runner’s High” has been attributed to what neurotransmitter?
Endogenous Opioid
What do Endogenous Opioids have an effect on?
Appetite, mood, and emotion
How does Clostridium tetani affect synaptic mechanisms?
Prevents vesicle fusion with the membrane, inhibiting release of GABA– a neurotransmitter that would normally inhibit muscle contraction
How does Clostridium botulinum affect synaptic mechanisms?
Interferes with actions of SNARE proteins at excitatory synapses that activate muscles
What does the Forebrain contain?
Cerebrum and Diencephalon (thalamus, hypothalamus, epithalamus)
Subcortical nuclei are interneurons that…
- Bring information into the cerebrum
- Carry information out
- Connect different areas within a a hemisphere
Each hemisphere of the brain contains…
- Cerebral cortex (outer shell of gray matter composed mostly of cell bodies that give the area a gray appearance)
- Inner layer of white matter (area that contains myelin)
What is the corpus callosum?
A massive bundle of nerve fibers that connects the cortex layers of the right and left hemispheres
Why is the cortex highly folded?
To increase surface area - increasing volume of the brain (4 times larger)
What are the four lobes of the brain?
- Frontal
- Parietal
- Temporal
- Occipital
What are the functions of the frontal lobe?
Reasoning, planning, parts of speech, movement*, emotions, and problem solving
What are the functions of the parietal lobe?
Movement, orientation, recognition, perception of stimuli
What is the function of the occipital lobe?
Visual processing
What are the functions of the temporal lobe?
Perception and recognition of auditory stimuli, memory, and speech
What are upper motor neurons?
The brain’s neurons that direct voluntary movements and integrate signals to create many involuntary muscle activities
What are lower motor neurons?
Neurons that go to a muscle
cell body is in the spinal cord, axon is in the periphery
What is the function of basal ganglia?
Control movement and posture; complex aspects of behavior
What are the functions of the cerebral cortex?
- Integration
- Collecting afferent information and processing it
- Effects motor and endocrine systems based on that info
What is the function of the thalamus?
Arousal and focusing attention
What is the function of the hypothalamus?
- Master commander for neural-endocrine coordination
- Eating, drinking, reproduction
What is the function of the epithalamus?
Regulate biological rhythms
What is the limbic system?
A “coalition” of forebrain areas (parts of cerebrum, thalamus, and hypothal) which coordinates emotional centers and and endocrine signals
