Grover - Neuronal Integration

Question 1

Frequency Coding

Answer 1

Conversion from amplitude modulated (graded potentials) to frequency modulated signals (all-or-none potentials)

Question 2

Divergence

Answer 2

Axon from single neuron branches many times, hitting multiple targets.

Allows mass recruitment and coordination

Question 3

Convergence

Answer 3

Single cell receives input from many presynaptic neurons

Allows integration of many sources of information

Question 4

What is the resting state of most neurons in the CNS?

Answer 4

Spontaneously active

Inhibitory Circuits suppress firing, fine tine firing patterns

Question 5

Presynaptic Inhibition

Answer 5

Used to gate information flow, such as inhibit reflex, inhibit pain sensation

Question 6

Disinhibition

Answer 6

Inhibition of an inhibitory neuron

Can be pre or post synaptic

Results in net excitatory effect

Question 7

Lateral Inhibition

Answer 7

Interneurons create inhibitory receptive field adjacent to excitatory receptive field

Enhance detection of contrast

Ex: Circular Center-Surround fields in the retina

Question 8

Feedback Inhibition

Answer 8

Requires recurrent pathway

Usefule for self regulation to control duration activity of in circuit

Ex: Renshaw Cells

Question 9

Feedforward Inhibition

Answer 9

Requires Divergent pathway

Useful for controlling antagonistic pathways

Ex: Reflex pathways controlling antagonistic muscles

Prevents competing activity

Question 10

Reverberating Circuits

Answer 10

Constructed from feedback excitatory connections

Allow for persistent activity–response can outlast stimulus, can allow information to be stored as short term memory

Question 11

What type of inhibition can cause seizures in the brain?

Answer 11

Deficit in runaway excitation in reverberating circuits that go uninhibited

Question 12

Central Pattern Generators

What type of calcium channels are found in these neurons?

Answer 12

Thythmically alternating activity can be created by several types of neural circuits

Useful for movements like walking, breathing

May have reciprocal inhibitory connections

- - -

T-type Calcium Channels

Question 13

Where is the critical region for information encoding in neural cells?

Answer 13

Integration (trigger) zone

Question 14

What signals enter the input zone?

Answer 14

Graded potentials

Encode by amplitude

Question 15

What conversion occurs at the integration zone?

Answer 15

Graded potentials are converted to all-or-none potentials (action potentials)

Amplitude Modulation is converted to Frequency Modulation

Question 16

What types of structures in the integration zone play a role in conversion to frequency modulation?

Answer 16

Voltage-Gated Calcium Channels:

1. High Voltage-Activated (HVA) calcium channels require strong depolarization
2. Low Voltage-Activated (LVA) or transient (T-Type) calcium channels open between resting potential and action potential threshold–rapidly inactivate (inactive @ resting potential)

- Inactivation removed if membrane potential is hyperpolarized

Calcium Activated Potassium Channels:

Opened by rise in intracellular calcium

Question 17

What is role of HVA calcium channels?

Answer 17

Slow Adaptation, firing rate greadually slows

Question 18

If integration zone contains LVA (T-Type) Voltage Gated Calcium channels, what can occur?

Answer 18

Burst Firing , Rebound Firing

T-Type activate below action potential threshold, open transiently–inactivate rapidly