Lecture 7: Electrical Signalling

Question 1

Ohm’s Law

Answer 1

The current that flows through most substances (metal wire) is directly proportional to the voltage applied.

Question 2

Resistance

Answer 2

Electrical property that impedes current.
It is inversely proportional to current.
Unit = Ohm

Question 3

Neuron

Answer 3

Nerve Cells
Each has a cell body (soma) which contains a nucleus, rough and smooth ER, Golgi apparatus, mitochondria etc.

Question 4

Neurogenesis

Answer 4

The birth of new neurons

Question 5

Dendrites

Answer 5

Tree-like structures that extend away from the cell body to receive messages from other neurons at specialized junctions called synapses.
Some have dendritic spines which further increase the surface area for possible synaptic connections.
Some neurons don’t have dendrites and others may have multiple.

Question 6

Axon Hillock

Answer 6

Specialized structure in cell body which integrates signals from multiple synapses and serves as a junction between the cell body and an axon.

Question 7

Axon

Answer 7

Tube-like structure that propagates the integrated signal to specialized endings called axon terminals.
Neurons usually have one or two but some like amacrine cells in the retina don’t have any.

Question 8

Myelin

Answer 8

Covers some axons
Acts as an insulator to minimize dissipation of the electrical signal as it travels down the axon, greatly increasing the speed of conduction.
Produced by Gilal cells

Question 9

Nodes of Ranvier

Answer 9

Periodic gaps in the myelin sheath
Sites where the signal is recharged as it travels along the axon.
Contain voltage gated k+ and Na+ channels

Question 10

Types of Neurons

Answer 10

Unipolar
Bipolar
Multipolar
Pseudounipolar

Question 11

Unipolar Neurons

Answer 11

Have one structure that extends from the soma.
Not found in vertebrates but found in insects.

Question 12

Bipolar Neuron

Answer 12

Has one axon and one dendrite extending from the soma.
Example is retinal bipolar cell

Question 13

Multipolar Neuron

Answer 13

Most common type of neuron
Contains one axon and multiple dendrites.
Found in the central nervous system
Example is Purkinje cell in the cerebellum.

Question 14

Pseudounipolar Neuron

Answer 14

Share characteristics of both unipolar and bipolar cells.
Has a single process which extends from soma but later branches into 2 distinct structures.
Includes most sensory neurons

Question 15

Ion channels

Answer 15

Span lipid bilayer membrane
Passageway for ions
Have different configurations: open, closed, inactive

Question 16

Resting Membrane Potential

Answer 16

Voltage of a neuron at rest
-70mV
Caused by differences in the concentrations of ions inside and outside the cell.
Dominated by difference between the number of K+ ions inside and outside the cell.
Maintained by increasing the concentration of cations outside the cell.

Question 17

Action Potential

Answer 17

Brief reversal of the resting membrane potential

Question 18

Refractory Period

Answer 18

Period where neuron cannot produce another action potential because its sodium channels will not open.

Question 19

Nerve Impulse

Answer 19

The propagation of an action potential along a cell membrane

Question 20

Saltatory conduction

Answer 20

Jumping of the action potential from one node to the next.

Question 21

Glial Cells in the CNS

Answer 21

Ependymal Cells
Microglia
Astrocytes
Oligodendrocytes

Question 22

Ependymal Cells

Answer 22

Assist in producing, circulating and monitoring cerebrospinal fluid that fills spaces/passages

Question 23

Microglia

Answer 23

Mobile phagocytic cells that remove cellular debris, waste products and pathogens

Question 24

Astrocytes

Answer 24

Maintains the blood-barrier
Structural Support
Regulates ion, nutrient and gas concentrations in interstitial fluid around neurons
Absorbs/recycles neurotransmitter
Forms scar tissue after injury

Question 25

Oligodendrocytes

Answer 25

Provide CNS framework by stabilizing axons.
Produces myelin
Wraps axon with layers of myelin and plasma membrane creating a myelin sheath.

Question 26

Neuroglia in the PNS

Answer 26

Schwann Cells
Satellite Cells

Question 27

Schwann Cells

Answer 27

Neurolemmocytes
Cover peripheral axons
Participate in axon repair

Question 28

Satellite Cells

Answer 28

Surround peripheral cell bodies
Regulate environment around neurons

Question 29

Synapse

Answer 29

Gap/place where information is transmitted from one neutron to another.

Question 30

Presynaptic Neuron

Answer 30

Neuron transmitting the signal

Question 31

Postsynaptic Neuron

Answer 31

Neuron receiving the signal

Question 32

Signal Summation

Answer 32

Net change in the postsynaptic membrane voltage determines whether the postsynaptic cell has reached the threshold required for an action potential.
Synaptic summation and the threshold for excitation act as a filter so that random noise in the system is not transmitted as important information.

Question 33

Repolarization

Answer 33

Membrane potential returns to resting value

Question 34

Hyperpolarization

Answer 34

Membrane potential becomes more negative

Question 35

Depolarization

Answer 35

Membrane potential becomes more positive

Question 36

Graded Potential

Answer 36

A specific input produces a change in membrane potential which is proportional to the length and magnitude.
Low Neurotransmitter: Less ion channels open, Smaller magnitude of graded potential
High Neurotransmitter: More ion channels open, Larger magnitude of graded potential

Question 37

Neurotransmitters

Answer 37

A chemical compound released by a neuron at a synapse and affects the transmembrane potential of another cell.

Question 38

Neuromodulators

Answer 38

A chemical compound released by a neuron that adjusts the sensitivities of another neuron to specific neurotransmitters.
Typically neuropeptides such as opioids