Electrical vs Chemical Synapse and Graded Potential Notes

Flashcards covering electrical vs chemical synapses, graded potentials, and muscle force modulation.

What is a presynaptic cell?

The cell sending the signal at a synapse.

What is a postsynaptic cell?

The cell receiving the signal at a synapse.

What is the synaptic cleft?

The tiny gap between the presynaptic and postsynaptic cells at a synapse.

What are gap junction channels?

Channels connecting presynaptic and postsynaptic cells in electrical synapses, allowing cytoplasmic continuity.

What are connexons?

Each gap junction channel consists of two of these.

What are connexin proteins?

Each connexon is composed of six of these.

What do gap junctions allow to pass?

Allow electrical current, metabolic signals, and ions to pass directly between cells.

What factors can cause gap junctions to close?

Low pH, high calcium, phosphorylation, and voltage changes.

Where are chemical synapses found?

Found between neurons and lack cytoplasmic continuity.

What happens when an action potential reaches the presynaptic terminal in a chemical synapse?

Voltage-gated Ca²⁺ channels open, Ca²⁺ floods in, triggering vesicle fusion and neurotransmitter release.

What are the two main types of receptors on the postsynaptic membrane in a chemical synapse?

Ionotropic receptors (ligand-gated ion channels) and metabotropic receptors (work through second messengers).

What are ionotropic receptors?

Ligand-gated ion channels that cause fast, short-lasting effects by changing the membrane potential.

What are metabotropic receptors?

Receptors that work through second messengers, activating protein kinases and leading to longer-lasting effects.

What is a graded potential?

A small change in the electrical charge of a neuron, occurring in dendrites or the cell body.

What are the two key neurotransmitters involved in graded potentials?

Glutamate and GABA

What is the function of Glutamate?

Excitatory - Opens sodium or calcium channels, making the inside of the neuron more positive.

What is the function of GABA?

Inhibitory - Opens chloride channels, making the inside of the neuron more negative.

What is spatial summation?

Multiple excitatory inputs from different places at the same time.

What is temporal summation?

One input happens repeatedly over time.

AMPA receptors are what type of channels?

Sodium channels

NMDA receptors are what type of channels?

calcium channels.

GABA-A receptors are what type of channels?

chloride channels (inhibitory).

What is tetany?

Muscle contracting continuously without relaxing between contractions.

How can skeletal muscle modulate force?

Recruiting more motor units, using different types of motor units, and muscle geometry.

What will a muscle contraction look like with a faster Ca++ pump?

The twitch will be shorter and return to baseline more quickly.

Which muscle cells are most likely to reach tetany?

A muscle cell with a slow Ca++ pump.