- Work as immune system of CNS - function as phagocytes - activate during nervous system development - activate after injury or infection

Neuroanatomy And Neurocytology Flashcards by Patrick Dinh

What are Neurons?

Anatomical and functional units for signal transmission

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What are Glia?

(Non-neuronal cells)
- supportive structural matrix, maintains homeostasis, nourishment, regulation of neuronal functions

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What are the anatomical components of a neuron?

Dendrites, Soma (cell body), Axon, Presynaptic axon terminal

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Bipolar Neuron

1 dendrite root and 1 axon

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Pseudounipolar neuron

Subclass of bipolar

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Multipolar neuron

Multiple dendrites and 1 axon
(Most common)

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3 functional classifications of neurons?

Motor neurons, sensory neurons, interneurons (between sensory and motor neurons)

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Types of macroglia and their functions

Astrocytes (CNS): star shaped cells that include neuronal signaling (liaison, communications, pathways for neuronal migration), housekeeping, nutritive functions for neurons

Oligodendrocytes ( Schwann cells

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What are Microglia?

Work as immune system of CNS
function as phagocytes
activate during nervous system development
activate after injury or infection

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Which cells contribute to myelination of neurons in CNS and PNS?

Oligodendrocytes and schwann cells

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What is Myelin?

An effective insulator, shielding neurons from extracellular environment (think of the rubber around an electrical wire)

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Which cells are the only supporting cells of the PNS?

Schwann cells

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Sequence of events for neural transmission?

Receptor is stimulated -> Local potential -> Action potential -> Synapses

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What is a local potential?

Small graded potential in amplitude and duration
- receptor or synaptic potential
- spreads passively and confined to small area of neuron membrane

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What is an Action Potential?

Large “all or none”, depolarizing signal
Actively propagates along neuron axon, traveling 1-way to presynaptic terminal

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What happens at the Synapses?

Transports signal to other neurons by release of neurotransmitters

What kind of membranes do neurons have?

Selectively permeable

What is the membrane potential and what ions are associated?

Separation of different charges across the membrane creating electrical potential of -70mV
Caused by uneven distribution of Na+, K+, and Anions
Cell membrane is more permeable to K+ than to Na+

What happens when the protein ion channels are open at the membrane?

Influx of Na+ into the cell since Na+ is normally in a higher concentration out of the cell

When at resting membrane potential, which side is more + and which side is more -?

Extracellular fluid is more positively charged than (+) and intracellular fluid is more negatively (-) charged at resting membrane potential

What is a Leak channel?

(Non-gated): small amount of ions that diffuse through the membrane at a slow continuous rate

What is a Modality-gated channel?

(Sensory neurons only) and they open in reaction to mechanical stimulation, temperature, or chemicals

What is a Ligand-gated channel?

Opens when neurotransmitter binds to post-synaptic receptors, generating local potentials

What is a Voltage-gated channel?

opens in reaction to change in electrical potential, generating action potentials

At resting membrane potential what are the relative charges of each side and where are the ions concentrated?

At rest, inside of the neuron is more - than outside - inside has more K+ and Anions - Outside with more Na+ and Cl-

How is Dynamic equilibrium during the resting potential maintained?

- Charged anions trapped inside the neuron - Passive diffusion of K+ and Na+ through leak channels - Na+/k+ pump requires ATP

What is the ratio of molecules for the sodium-potassium pump?

- 2 K+ into the cell for every 3 Na+ out

What stimulus threshold intensity is required to produce an action potential?

-55mV, though google says -50mV to -55mV (INCREASING THE STIMULUS INTENSITY WILL NOT CHANGE THE AMPLITUDE OFR DURATION OF THE ACTION POTENTIAL)

what are the 3 stages of an Action potential?

- Rising depolarizing phase: more+ from -70 to +30mV - Falling repolarizng phase: more - from +30 to -70mV - Re-setting/hyperpolarizing phase:

What is depolarization?

- small change in membrane voltage depolarizes it enough to open Na+ channels (voltage gated Na+ channels) - AS more Na+ moves into the neuron, more and more Na+ channels open - Polarity rapidly changes from - to + to produce action potential

What causes repolarization?

Na+ channels start to close, and K+ voltage-gated channels start to open (K+ channels are slower to respond to the AP’s depolarization) - K+ ions exit and membrane potential falls toward RP from + to - toward -70mvs

What causes hyperpolarization?

K+ channels remain open during repolarization leading to hyperpolarized membrane potential (below -70mv)

How does the neuron get back to RP/Resting potential?

Gradually active Na+/K+ pumps the ions to restore RP of -70mv

What is the ratio in/out of sodium potassium pump?

2 potassiums in for 3 sodiums out (against their concentration gradients) an easy way to remember is bananas with potassium are better for you than fries which have sodium

What is the refractory period?

Absolute: completely unresponsive to stimuli - Na+ channels open and not yet reset Relative: may respond to stronger stimuli - Most of Na+ channels are reset Refractory periods advantageous for promotion of fwd propagation of AP and preventing backward flow

What factors influence an action potential?

- Diameter of axon (larger means faster) - Myelin (prevents current flow across membrane, preserves amplitude of impulse) - Temperature (warm proteins react faster)

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