Action potential, Synaptic transmission and CSF

Flashcards about action potentials, synaptic transmission and CSF

What are the two main phases of a nerve impulse?

Depolarizing phase and repolarizing phase

What happens during the depolarization phase of an action potential?

Voltage-gated Na+ channels open, allowing Na+ to diffuse into the cell

What causes repolarization in an action potential?

Na+ channels inactivate, K+ channels open, allowing K+ to diffuse out of the cell

What is the role of the Na+/K+ pump in the resting membrane potential?

It reestablishes the resting membrane potential by pumping Na+ out and K+ in.

Why does action potential propagation occur in only one direction?

Because the absolute refractory period prevents another action potential in the reverse direction.

What is saltatory conduction?

The rapid propagation of action potentials in myelinated axons due to the action potentials being produced at successive nodes of Ranvier.

What is a synapse?

A region where communication occurs between two neurons or between a neuron and an effector cell.

What is the role of the presynaptic neuron?

It carries a nerve impulse toward a synapse and sends the signal.

What is the role of the postsynaptic neuron?

It receives the signal from the presynaptic neuron and carries the nerve impulse away from the synapse.

What are axodendritic synapses?

Synapses from axon to dendrite.

What are axosomatic synapses?

Synapses from axon to cell body.

What are axoaxonal synapses?

Synapses from axon to axon.

What are the two main types of synapses?

Electrical and chemical synapses.

What are gap junctions?

Structures that connect the cytosol of adjacent cells in electrical synapses, allowing action potentials to conduct directly.

What are the advantages of electrical synapses?

Faster communication and synchronization of neuronal activity.

What type of muscle can be connected with electrical synapses?

Cardiac muscle cells

What is the synaptic cleft?

The space between the presynaptic and postsynaptic neurons in a chemical synapse.

How does communication occur across the synaptic cleft?

Through the release of neurotransmitters from the presynaptic neuron, which bind to receptors on the postsynaptic neuron.

What is a postsynaptic potential?

A type of graded potential produced in the postsynaptic neuron in response to a neurotransmitter.

What is synaptic delay and why does it occur?

The time required for processes at a chemical synapse, about 0.5 msec; it occurs because of the time needed for neurotransmitter release and binding.

What role do voltage-gated Ca2+ channels play in synaptic transmission?

They open in response to the depolarizing phase of the nerve impulse, allowing Ca2+ to flow into the presynaptic neuron, triggering exocytosis of synaptic vesicles.

What triggers exocytosis of synaptic vesicles?

An increase in the concentration of Ca2+ inside the presynaptic neuron.

What is the role of neurotransmitter receptors?

To bind neurotransmitters and open ion channels, allowing ions to flow across the membrane and change its voltage.

What is the functional difference between an EPSP and an IPSP?

EPSPs cause depolarization (excitation), while IPSPs cause hyperpolarization (inhibition).

What effect does opening Na+ channels have on the postsynaptic membrane potential?

It causes depolarization because Na+ inflow occurs.

What effect does opening Cl- or K+ channels have on the postsynaptic membrane potential?

It causes hyperpolarization, because Cl- diffuses in or K+ diffuses out.

What is the difference between an excitatory and inhibitory neurotransmitter?

An excitatory neurotransmitter causes depolarization, while an inhibitory neurotransmitter causes hyperpolarization.

What determines whether a neuro transmitter will have an EPSP or IPSP?

The structure of the neurotransmitter receptor to which it binds.

What are ionotropic receptors?

Neurotransmitter receptors that contain a neurotransmitter binding site and an ion channel.

What are metabotropic receptors?

Neurotransmitter receptors that contain a neurotransmitter binding site and are coupled to a separate ion channel by a G protein.

What is cerebrospinal fluid (CSF)?

A clear, colorless liquid that protects the brain and spinal cord from chemical and physical injuries.

What are the functions of cerebrospinal fluid?

Mechanical protection, chemical protection and circulation

Where is cerebrospinal fluid located?

In cavities within the brain and spinal cord, and around the brain and spinal cord in the subarachnoid space.

What are ventricles?

Cavities within the brain that are filled with cerebrospinal fluid.

What are the three basic functions of CSF?

Mechanical protection, chemical protection, and circulation.

How does CSF provide mechanical protection?

It acts as a shock-absorbing medium and buoys the brain, protecting it from jolts.

How does CSF provide chemical protection?

It maintains an optimal chemical environment for neuronal signaling.

How does CSF facilitate circulation?

It serves as a medium for minor exchange of nutrients and waste products between the blood and adjacent nervous tissue.

Where is CSF produced?

Choroid plexuses in the ventricles.

List some substances that CSF contains.

Small amounts of glucose, proteins, lactic acid, urea, cations (Na+, K+, Ca2+, Mg2+), and anions (Cl− and HCO3−)