Neuroscience Lecture #2

Front 1

Major cell types in nervous system (2)

Back 1

Glial cells and neurons

Front 2

Classes of glial cells (2)

Back 2

Microglia and Macroglia

Front 3

Function of Glial Cells

Back 3

-Surround and support neurons
-Produce Myelin
-Occasionally take up neurotransmitters
-Scavenger function
-Guidance of migrating neurons during development
-Help for blood-brain barrier
-Nourish neurons (growth factors)

Front 4

Microglia

Back 4

-Phagocytes which are mobilized after injury, infection, disease
-Secrete signaling molecules that modulate local inflammation
-Increase following neural injury

Front 5

Diseases Microglia are involved in

Back 5

AIDS related dimentia, Parkinson's, Alzheimer's, MS

Front 6

Macroglia Types (Small and Large)

Back 6

Small - Oligodendrocytes and Schwann Cells
Large - Astrocytes

Front 7

Where Macroglia Are Found

Back 7

Oligodendrocytes - CNS
Schwann Cells - PNS

Front 8

Astrocytes

Back 8

-Most numerous
-Potential role in nutrion of neurons
-Help maintain proper ion concentration in extra-cellular space (K+)
-Take up Neurotransmitters from synaptic zone

Front 9

Action Potential

Back 9

Rapid, transient, all-or-none impulses w/constant amplitude of 100mV and duration of 1ms

Front 10

Myelin Sheath

Back 10

-Increase speed of conduction
-Nodes of Ranvier

Front 11

Principle of Dynamic Polarization

Back 11

-Unidirectional flow of electrical signals within neurons
-from dendrites to axon hillock
-from trigger region, action potential propagated through length of axon to presynaptic terminals

Front 12

Principle of Connectional Specificity

Back 12

-Each cell makes specific connections wiht certain postsynaptic target cells
-Specific pattern of connections mediate function

Front 13

Unipolar Neuron

Back 13

-Simplest, single process that serves as receptor and releasing terminal
-Afferent and efferent
-Autonomic Nervous System

Front 14

Biopolar Neuron

Back 14

-Two processes (Dendrite and axon), seen in sensory system

Front 15

Pseudo-unipolar Neuron

Back 15

-Develops as bipolar cells; processes fuse to form one axon, one peripheral and one central (Seen in mechanoreceptors)
-Somatosensory system

Front 16

Multipolar Neuron

Back 16

Single axon, many dendrites; most common

Front 17

Sensory Neurons

Back 17

-Afferent
-Monitoring of internal state of body
-Monitoring external environment (Perception and motor coordination)
-Away from stimulus

Front 18

Motor Neuron

Back 18

-Efferent
-Carry signals TO muscles and glands
-Cause muscular contraction

Front 19

Interneurons

Back 19

-Largest class of cells
-Local information processing
-Axons remain within CNS
-Two types - Projection and Local

Front 20

Projection Interneuron

Back 20

-Golgi Type I
-Connect to regions in CNS
-Relay information across great distances

Front 21

Local Interneuron

Back 21

-Golgi Type II
-Relay information locally
-Example: within same segmental level

Front 22

Principle of Divergence

Back 22

-Each sensory neuron connects with 100-150 motor neurons
-Common input stage of nervous system

Front 23

Principle of Convergence

Back 23

Single motor neuron recieves input from many sensory neurons

Front 24

Feed-Forward Inhibition

Back 24

-Inhibitory connection of sensory neuron with antagonist of quadriceps
-Inhibit muscles so only appropriate muscles are recruited

Front 25

Feedback Inhibition

Back 25

-Excitatory connection between sensory neuron and motor neuron innervating quadriceps dampened by inhibitory connection to pathway
-Self regulation to ensure stimulation does not have prolonged motor output

Front 26

Resting Membrane Potentail

Back 26

-Negative potential inside neuron at rest compared to outside of cell
-Typically between -40 to -90mV (-65mV)

Front 27

Ionic Basis of Resting Membrane Potential is Based on Two Factors:

Back 27

-Unequal distribution of positive (Na+/K+) ions and negatively charged amiono acids and proteins across membrane
-Selective permeability of membrane to K+

Front 28

Unequal Distribution of Ions Maintained By:

Back 28

-Na+/K+ Pump that pumps Na+ Out and K+ In.

Front 29

Negative Resting Potential is Due to?

Back 29

-Membrane potential more permeable to K+ at rest; causes leakage of K+ from inside to outside of cell
-More negative charge inside

Front 30

Depolarization

Back 30

-Reduction in membrane potential from -65mV (to -55mV)
-Enhances ability of cell to generate action potential
-Excitatory

Front 31

Hyperpolarization

Back 31

-Increases in membrane potential from -65mV (to -75mV)
-Decreases ability to generate action potential
-Inhibitory

Front 32

Receptor Potentials

Back 32

-Occur in Sensory Neurons
-Response to stimuli
-Resting potential changed for fraction of a second
-Response is graded-depends on stimulus amplitude
-Local signal-decays within certain distance (1-2mm)

Front 33

Synaptic Potentials

Back 33

-Receptors on receiving neuron uptake neurotransmitters from synaptic cleft
-Brief change in resting membrane potential
-Response graded-depends on number of synapses activated

Front 34

Conductile Component

Back 34

-Action Potential
-All-or-None
-Brief (1ms), Fast (100m/s)
-Does not decay with travel due to regeneration
-AP is stereotypical

Front 35

How Action Potentials Differ?

Back 35

Number of potentials per unit time (frequency) and overall duration of stimulation

Front 36

Multipolar Neuron

Back 36

Single axon, many dendrites; most common

Front 37

Sensory Neurons

Back 37

-Afferent
-Monitoring of internal state of body
-Monitoring external environment (Perception and motor coordination)
-Away from stimulus

Front 38

Motor Neuron

Back 38

-Efferent
-Carry signals TO muscles and glands
-Cause muscular contraction

Front 39

Interneurons

Back 39

-Largest class of cells
-Local information processing
-Axons remain within CNS
-Two types - Projection and Local

Front 40

Projection Interneuron

Back 40

-Golgi Type I
-Connect to regions in CNS
-Relay information across great distances

Front 41

Local Interneuron

Back 41

-Golgi Type II
-Relay information locally
-Example: within same segmental level

Front 42

Principle of Divergence

Back 42

-Each sensory neuron connects with 100-150 motor neurons
-Common input stage of nervous system

Front 43

Principle of Convergence

Back 43

Single motor neuron recieves input from many sensory neurons

Front 44

Feed-Forward Inhibition

Back 44

-Inhibitory connection of sensory neuron with antagonist of quadriceps
-Inhibit muscles so only appropriate muscles are recruited

Front 45

Feedback Inhibition

Back 45

-Excitatory connection between sensory neuron and motor neuron innervating quadriceps dampened by inhibitory connection to pathway
-Self regulation to ensure stimulation does not have prolonged motor output

Front 46

Resting Membrane Potentail

Back 46

-Negative potential inside neuron at rest compared to outside of cell
-Typically between -40 to -90mV (-65mV)

Front 47

Ionic Basis of Resting Membrane Potential is Based on Two Factors:

Back 47

-Unequal distribution of positive (Na+/K+) ions and negatively charged amiono acids and proteins across membrane
-Selective permeability of membrane to K+

Front 48

Unequal Distribution of Ions Maintained By:

Back 48

-Na+/K+ Pump that pumps Na+ Out and K+ In.

Front 49

Negative Resting Potential is Due to?

Back 49

-Membrane potential more permeable to K+ at rest; causes leakage of K+ from inside to outside of cell
-More negative charge inside

Front 50

Depolarization

Back 50

-Reduction in membrane potential from -65mV (to -55mV)
-Enhances ability of cell to generate action potential
-Excitatory

Front 51

Properties of Action Potential

Back 51

-Active influx of Na+ at Nodes of Ranvier leading to depolarization
-Passive flow of Na+ ions along axon towards axon terminal
-Since node of Ranvier is only point of Na+ influx, action potential seems to jump from node to node

Front 52

Electrical Synapse

Back 52

-Presynaptic and postsynaptic cells linked at gap junction
-Gap junction have aligned channels in both cells
-Allow for flow of passive ionic current
-Flow of current is bidirectional

Front 53

Gap Junction

Back 53

-Transmission is very fast
-Help in synchronizing activity across neurons
-Gap junctions used by glial cells

Front 54

Neurotransmitters

Back 54

-Either small molecule or peptides
-Small molecules synthesized in axon terminal
-Peptides synthesized in cell body
-Both can be released from same axon terminal

Front 55

Release of Neurotransmitter

Back 55

-At neuromuscular junction - specialized region of muscle fiber called end plate - motor neuron axon terminal contact
-Action potential in motor neuron causes depolarization of muscle fiber (end plate potential)

Front 56

Role of Calcium

Back 56

-Action potential causes opening of Ca++ channels
-Increase of Ca++ causes binding of vesicles to membrane and release of neurotransmitters
-Decrease of presynaptic Ca++ decreases the amount of neurotransmitter released