Chapter12 Study guide

What are the three zones of a neuron and their functions?

1. Receptive Segment: Receives and integrates incoming signals (graded potentials). 2. Axon Hillock: Generates action potentials (brief). 3. Transmissive Segment: Releases neurotransmitters to communicate with other neurons (short duration).

What types of cells form myelin in the CNS and PNS?

Oligodendrocytes form myelin in the CNS; Schwann cells form myelin in the PNS.

What is the order of events during an EPSP?

1. Excitatory neurotransmitter release from presynaptic neuron. 2. Neurotransmitter diffuses across synaptic cleft. 3. Neurotransmitter binds to receptors on postsynaptic neuron. 4. Ion channels open, allowing influx of positive ions. 5. Depolarization of the postsynaptic membrane (EPSP).

Define the synaptic cleft.

The synaptic cleft is the narrow gap between the presynaptic neuron and the postsynaptic cell, across which neurotransmitters diffuse.

What are examples of E-factors that influence reaction rate?

Examples include enzyme concentration, substrate concentration, temperature, pH, and the presence of cofactors or inhibitors.

What are the structural classifications of nerves?

Cranial nerves (from the brain) and spinal nerves (from the spinal cord).

What ions are primarily involved in establishing resting potential?

Primarily potassium (K+) and sodium (Na+).

Which ion has a greater diffusion flow at resting potential?

Potassium (K+) has a greater diffusion flow due to more leaky potassium channels.

What is meant by electrochemical gradient?

The electrochemical gradient is the combination of the concentration gradient and the electrical gradient affecting ion movement across the membrane.

When is the electrochemical gradient for sodium high?

The electrochemical gradient for sodium is high at resting potential due to a strong concentration gradient and a strong electrical gradient.

What is the function of the sodium-potassium pump?

The sodium-potassium pump maintains resting potential by pumping 3 Na+ ions out and 2 K+ ions into the cell, crucial for preventing excessive sodium influx.

What are characteristics of graded potentials?

Graded potentials are local changes in membrane potential that can be depolarizing or hyperpolarizing, vary in amplitude with stimulus intensity, summate, and do not have a refractory period.

Define temporal summation.

Temporal summation is the process where repeated stimuli at the same location occur in rapid succession, building upon each other to reach threshold for an action potential.

What is the function of the somatic sensory division?

The somatic sensory division transmits sensory information from skin, muscles, and joints to the CNS for awareness of sensations like touch, temperature, and pain.

What do astrocytes do in the CNS?

Astrocytes support, form the blood-brain barrier, and regulate the chemical environment in the CNS.

Define hyperpolarization.

Hyperpolarization is when the membrane potential becomes more negative than the resting potential, making it less likely for the neuron to fire an action potential.

What happens physiologically when voltage-gated sodium channels don't inactivate?

Prolonged depolarization phase, suppressed repolarization, extended action potential duration, and increased refractory period.