Lecture 2 Flashcards
What is action potential ?
- Electrical charge that runs down the axon from the axon hillock to the terminal buttons
- A brief electrical signal that provides the basis for conduction of information along an axon
What is the Sodium Potassium Pump ?
- protein complex
- continually pumps out 3 sodium ions and draws in 2 potassium ions
What is resting potential ?
The difference in electrical charge between the inside and the outside of a neuron when the cell is in a non-excited state
What is a electrical gradient ?
Difference in electrical charge between the inside and outside of the cell
What is a concentration gradient ?
The difference in distribution of ions across the membrane
What is the All-or-none Law ?
Once an action potential is triggered in an axon, it is propagated without growing or diminishing to the axon terminal buttons
What is the Rate Law ?
Variations in the intensity of a stimulus or other information being transmitted along an axon are represented by variations in the rate at which that axon fires
What is a Saltatory Conduction ?
Jumping of action potential from node to node
What is the synapse ?
The place where information is transmitted from one neuron to another
What is a presynaptic neuron?
Neuron transmitting signal
What is a postsynaptic neuron ?
Neuron receiving signal
What is a reflex arc ?
Circuit from sensory neuron to a muscle response
What were Sherringtons observations ?
- Reflexes are slower than conduction along an axon
- Several weak stimuli presented at slightly different times or locations produce a stronger reflex than a single stimulus
- As one set of muscles becomes excited, another set relaxes
What is temporal summation ?
A cumulative effect of a repeated stimuli within a brief time
several impulses from one neuron over time
What is spatial summation ?
Combination of effects of activity from 2 or more synapses onto a single neuron
impulses from several neurons at the same time
What occurs in inhibitory synapses ?
input from an axon hyperpolarizes the postsynaptic cell, moving the cell’s charge farther from the threshold and decreasing the probability of an action potential
Reduce neuron activity
What occurs in excitatory synapses ?
Increase the activity of receiving a neuron
What is EPSP ?
- Excitatory postsynaptic potential
- Caused by positively charged sodium entering the neuron
- a graded depolarization
What is IPSP ?
- Inhibitory postsynaptic potential
- Caused by negatively charged chloride ions entering the neuron
- A graded hyperpolarization
At what 3 places can synapses occur at ?
- On dendrites: axodendritic synapse
- On the soma: axosomatic synapse
- On other axons: axoaxonic synapse
What is the presynaptic membrane ?
The membrane of axon terminal
where neurotransmitter is released
What is the postsynaptic membrane ?
The membrane opposite of the axon terminal button in a synapse
receives the message
What is the synaptic cleft ?
space between presynaptic and postsynaptic membrane
What is the synaptic vesicle ?
A small, spherical hollow organelle; contains molecules of a neurotransmitter
What is a neurotransmitter ?
Chemical messengers that carry chemical signals
What is a ligand ?
A neurotransmitter that binds
What are Ligand-Gated Ion Channels ?
Transmembrane ion-channel proteins which open to allow (e.g. Na, K, Cl) to pass through membrane in response to the binding of a chemical messenger
What is a ionotropic receptor ?
A receptor that contains a binding site for a neurotransmitter and an ion channel that opens when a molecule of the neurotransmitter attatches to the binding site
Fast acting
What is a metabotropic receptor ?
A receptor that contains a binding site for a neurotransmitter which then activates an enzyme that begins a series of events that opens an ion channel elsewhere in the membrane of the cell
Slow but amplified
What is neural integration ?
The process by which inhibitory and excitatory postsynaptic potentials summate and control the rate of firing of a neuron
What are 8 neurotransmitters ?
- Adrenaline (fight or flight )
- GABA (calming)
- Noradrenaline (concentration)
- Acetylcholine (learning)
- Dopamine (pleasure)
- Glutamate (memory)
- Serotonin (mood)
- Endorphins (euphoria)
What are agonists ?
Bind to receptor, producing a similar response to the intended chemical
What are antagonists ?
Bind to receptor either on the primary site, or another site, which stops the receptor from producing a response
What occurs at the synapse?
- Action potential arrives at axon terminal
- Voltage-gated Ca channels open and Ca enters the axon terminal
- Ca entry causes neurotransmitter-containing synaptic vesicles to release contents by exocytosis
- Neurotransmitter diffuses across the synaptic cleft and binds to ligand-gated ion channels on the postsynaptic membrane
- Binding of neurotransmitter opens ligand-gated ion channels, resulting in graded potentials
- Reuptake by the presynaptic neuron, enzymatic degradation and diffusion reduce neurotransmitter levels, terminating the signal
