Week 2 Vocabulary Flashcards
Electron
A negatively charged subatomic particle
Proton
A postively charged subatomic particle
Ions
Atoms that do not have an equal number of protons and electrons. If an atom loses an electron, it will be positively charged, an example being potassium (K+). In an atom gains an electron, it will be negatively charged, an example being chloride (Cl-).
Electrical Potential
The difference in voltage between the inside and outside of the cell.
Volt
The unit of electrical potential. In neurons, voltage is always in millivolts (mV).
Current
The flow of electrical charge. In neurons, current is carried by ions flowing across the cell membrane.
Resistance
The impedance to current flow in a system. In neurons, the cell membrane creates resistance by preventing free ion flow, while open ion channels in the membrane reduce resistance by creating a path for ion flow.
Insulator
A substance with a high resistance to current flow. Myelin acts as an insulator by wrapping axons and preventing ions from flowing out, forcing them to take the path of least resistance, which is down the axon towards the synaptic terminal.
Cell/Plasma Membrane
A barrier of fat (lipids) surrounding all parts of the cell. The inside of the cell is known as intracellular, or cytoplasmic. The outside of the cell is known as the extracellular space. The integrity of the cell membrane is essential to maintaining resting membrane potential in neurons.
Ion Channel
A protein complex within the cell membrane that allows ions to pass between the inside and outside of the cell.
Resting Membrane Potential
The steady state voltage of the inside of the cell relative to the extracellular space, which is approximately -65 mV. This is maintained by three ions: potassium (K+), sodium (Na+), and chloride (Cl-). At rest, K+ is at a higher concentration inside the cell, while Na+ and Cl- are at a higher concentration outside the cell.
Chemical Force
This refers to the chemical gradient between the inside and outside of the cell that causes molecules to move. Molecules want to move towards areas of lower concentration. For example, potassium is at a higher concentration inside the cell, so the chemical force pushes potassium out.
Electrical Force
This refers to the electrical potential difference between the inside and outside of the cell that causes ions to move. Ions are attracted to the opposite charge. As the inside of the cell is more negative, electrical forces will push positively charged ions like potassium into the cell. At rest, the chemical and electrical forces working on potassium are perfectly opposed, resulting in zero net movement (this doesn’t mean no movement at all though!)
Ground
This refers to the reference point of voltage (0 mV), which in the case of neurons is the extracellular space.
Demyelinating Disease
A disease that is caused by a loss of myelin. These disease can affect central neurons, peripheral neurons, or both. Importantly, the symptoms are dependent on which type(s) of neurons are affected, and are often different between patients with the same disease.
Diabetes
A disease in which patients can no longer control their blood sugar. High blood sugars in diabetic patients can lead to demyelination of sensory nerves in the peripheral nervous system.
Multiple Sclerosis
A demyelinating disease of the central nervous system.
Charcot-Marie-Tooth Disease
A demyelinating disease of the peripheral nervous system.
Synaptic Cleft
The small space between the presynaptic and postsynaptic cell, across which neurotransmitters diffuse.
Presynaptic Terminal
The site of release of neurotransmitters.
Postsynaptic Terminal
The site of binding of neurotransmitters to receptors.
Neuromuscular Junction
The synapse where a motoneuron contacts a muscle.
Constitutive
Always active. In the synapse, constitutive release of neurotransmitters is suppressed.
Organelle
A subunit within a cell that is surrounded by its own membrane.
Vesicle
A small organelle that carries specific molecules, such as neurotransmitters.
SNARE Pin Complex
Proteins that anchor neurotransmitter-containing vesicles to the cell membrane.
Calcium (Ca++)
The ion that flows into the presynaptic terminal following the arrival of an action potential, leading to fusion of the vesicle and cell membranes, and thus release of neurotransmitters into the synaptic cleft.
Clostridial Toxins
Proteins released by the Clostridium genus of bacteria. These include botulinum toxin, tetanus toxin, as well as others involved in serious gastrointestinal illness.
Botox
The pharmaceutical name for botulinum toxin. It functions by cleaving the SNARE proteins, impairing release of acetylcholine at the neuromuscular junction, and thus paralyzing the muscle.
Dopaminergic Neuron
A neuron that releases dopamine.
Parkinson’s Disease
A neurodegenerative disease characterized by the death of some dopaminergic neurons, specifically in the substantia nigra pars compacta of the basal ganglia.
Substrate
A building block used by a cell to create a product. For example, the substrate for dopamine can be given to Parkinson’s patients so the surviving dopaminergic neurons can produce enough dopamine to make up for the loss of other neurons.
Focal dystonia
A condition where patients suffer from localized, involuntary and sustained muscle contractions.
Diffusion
The natural spread of molecules from high concentration to low concentration. An important method of terminating the signal between two neurons.
Reuptake
The transport of neurotransmitters from the synaptic cleft back into the presynaptic terminal, for signal termination and recycling.
Acetylcholinesterase (AChE)
The enzyme responsible for breaking down acetylcholine (ACh) at the neuromuscular junction, the primary means of terminating ACh signaling.
Receptor
The “ears” of the postsynaptic neuron. Neurotransmitter binds these to transmit a signal, often leading to the opening of an ion channel.
Excitatory
A response to a stimulus that leads to the membrane potential becoming more positive. For example, an ion channel opening that allows sodium to flow into the cell.
Glutamate
The most common excitatory neurotransmitter.
Inhibitory
A response to a stimulus that leads to the membrane potential becoming more negative. For example, an ion channel opening that allows chloride to flow into the cell.
GABA
The most common inhibitory neurotransmitter.
Myasthenia Gravis
A disease where the patient’s immune system inappropriately destroys acetylcholine receptors at the neuromuscular junction, leading to weak and unsustainable muscle contraction. Treatment involves either inhibiting AChE to maintain a high concentration of acetylcholine in the synaptic cleft, and/or suppressing the patient’s immune system.
