Synapses

What is a synapse?

A synapse is a gap 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.

Who is Charles Scott Sherrington?

He was a neuroscientist who studied reflex arcs and the transmission of signals in the nervous system.

What did Sherrington find about reflex arcs?

The circuit from sensory neuron to muscle response.

What is temporal summation?

Repeated stimuli in the same location in rapid succession.

What is spatial summation?

Stimuli in several close locations at one time.

What is a graded potential?

A small stimulus that changes the voltage in the membrane but does not activate the threshold of excitation.

What are excitatory synapses?

They make a neuron more likely to fire.

What are inhibitory synapses?

They make a neuron less likely to fire.

What is an excitatory postsynaptic potential (EPSP)?

A graded depolarization caused by positively charged sodium entering the neuron.

What is an inhibitory postsynaptic potential (IPSP)?

A graded hyperpolarization caused by negatively charged chloride ions entering the neuron.

What is spontaneous firing rate?

Neurons are always firing at different rates even without synaptic input.

Who is Otto Loewi?

He was a neuroscientist known for his research demonstrating that nerves send messages through chemicals.

What is a neurotransmitter?

Chemical messengers that carry chemical signals.

What is the synaptic cleft?

The space between presynaptic and postsynaptic membranes.

What happens when an action potential arrives at the axon terminal?

Voltage gated calcium channels open and calcium (Ca) enters the axon terminal.

What is exocytosis in the context of synaptic transmission?

The process where neurotransmitter-containing synaptic vesicles release their contents.

What happens after neurotransmitter binds to ligand-gated ion channels?

Binding opens ligand-gated ion channels, resulting in graded potentials.

What terminates the signal in a synapse?

Reuptake by the presynaptic neuron, enzymatic degradation, and diffusion reduce neurotransmitter levels.