Neuro Objectives 2

Neuro Objectives 2

1.

Dendrites

(signal input)

Axon Hillock Axon Terminal

(decision for AP) (transmission of AP)

Soma

(production of proteins)

Axon

Neurotransmitters

(Signal transducer in periphery)

2.Reason for resting membrane potential: Electrochemical equilibrium whereby inside is negatively charged. Since 3 Na+ are pumped out of the cell while 2 K+ are pumped in, the inside of the cell loses more positive charge than it gains (thus the inside is negatively charged)

3.Dendrites: receive input from external synaptic input, receive slow potentials

Slow (graded) potential: small potential, summation of multiple graded potentials can lead to an action-potential, long lived but over a small area (think pebble thrown into a pond)

Axons: transmit an action potential from axon hillock if axon hillock has depolarized to threshold potential, often surrounded by myelin to help electrical transduction of signal

Action potential: large wave of depolarization (influx of Na+) followed by hyperpolarization (outflux of K+), only one can occur at a time, lasts around 1-2 ms, etc.

4.Digital: differences in summation of graded potentials

Analog (one signal): when threshold potential is reached, action potential moves down axon and releases neurotransmitters, once neurotransmitters are released, signal will be received in the form of a graded potential (and the signal goes back to digital)

5.Chemical synapse: Where neurotransmitters are released from vesicles in the pre-synaptic cell. In post-synaptic cells, there are often ligand-gated ion channels that will alter the permeability to a single ion. EPSPs (excitatory post-synaptic potentials) are caused when the ion permeability causes depolarization of the post-synaptic cell. IPSPs (inhibitory post-synaptic potentials) are caused when hyperpolarization occurs and moves the potential further from the threshold potential.

6.Myelin: Insulates neurons so that action potential does not need to be constantly regenerated (sans the Nodes of Ranvier)

CNS: oligodendrocytes. These cells can myelinate more than one axon

PNS: Schwann cells. These cells can only myelinate one axon.

• both work by wrapping their cell membranes around the axon like a pig in a blanket

7.All in the CNS

Astrocytes: “star” cells – repair and support of metabilism

Microglia: similar to macrophages, phagocytic injury cleaners

Ependyma: line ventricles and buffer CSF

8.Summation is useful because it helps the cell reach an action potential more rapidly

Spatial summation: summation of signals brought to points close in proximity in the post-synaptic cell.

Temporal summation: summation of signals brought at or near the same time in the post-synaptic cell.

9.Convergence: signals from many sources can influence one neuron

Divergence: signals from one neuron can branch and influence many sources

10.

MuscleConversion to action potential Spinal Cord

Graded potential

Conversion to graded potential

Conversion to action potential