Module 3

Question 1

Afferent vs Efferent neurons

Answer 1

Afferent neurons carry information towards the central nervous system.
Efferent neurons carry information away from the central nervous system.

Question 2

What are the components of the central nervous system?

Answer 2

The brain and spinal cord

Question 3

What are the components of the peripheral nervous system?

Answer 3

The peripheral nervous system consists of nerve tissue outside the CNS: cranial nerves and branches, spinal nerves and branches, ganglia, plexuses, and sensory receptors.

Question 4

What are the subdivisions of the peripheral nervous system?

Answer 4

The afferent division, which consists of somatic sensory, visceral sensory, and special sensory.
The efferent division, which consists of the somatic motor and autonomic (sympathetic and parasympathetic).

Question 5

What is the function of the cell body?

Answer 5

The cell body is the control centre, with processes that extend outwards (dendrites and axons).

Question 6

What is the function of dendrites?

Answer 6

Receives incoming signals from neighbouring cells.

Question 7

What is the function of axons?

Answer 7

Carry outgoing signals from the integrating centre to target cells.

Question 8

What does the presynaptic terminal contain?

Answer 8

Contains transmitting elements (usually chemical transmission).

Question 9

What do afferent sensory neurons do?

Answer 9

Carry information about temperature, pressure, light, and other stimuli to the CNS.
Have specialized receptors that convert stimulus into electrical energy.

Question 10

What are interneurons?

Answer 10

Complex branching neurons that facilitate communication between neurons.

Question 11

What do efferent motor neurons control? What do they usually contain?

Answer 11

Control skeletal muscles.

Usually have axon terminals and varicosities.

Question 12

What do autonomic neurons do? What do they usually contain?

Answer 12

Influence many organs.

Usually have axon terminals and varicosities.

Question 13

What is axonal transport?

Answer 13

The movement of materials between the axon terminal and the cell body of a neuron.

Question 14

What are the 6 steps of axonal transport?

Answer 14

1. peptides are synthesized on the rough ER and packaged by the golgi apparatus
2. fast axonal transport walks vesicles and mitochondria along the microtubule network
3. vesicle contents are released via exocytosis
4. synaptic vesicle recycling
5. retrograde fast axonal transport
6. old membrane components digested in lysosomes

Question 15

What is fast axonal transport? What is the difference between anterograde and retrograde?

Answer 15

Fast axonal transport transports membrane bound proteins and organelles.
Anterograde: cell body to axon terminal, up to 400mm/day.
Retrograde: axon terminal to cell body, 200mm/day.

Question 16

What does slow axonal transport move?

Answer 16

Transports cytoplasmic proteins (enzymes) and cytoskeleton proteins.
Anterograde: up to 8mm/day

Question 17

Why is slow axonal transport believed to be slower?

Answer 17

Slower due to frequent periods of pausing of movement.

Question 18

Kinesins vs Dyneins

Answer 18

Kinesins are used in anterograde transport and are believed to follow positive charge.
Dyneins are used in retrograde transport.

Question 19

What drives movement of proteins to walk along filaments?

Answer 19

ATP hydrolysis

Question 20

What do synapses contain?

Answer 20

Extracellular matrix (proteins and carbohydrates) that hold the pre and post synaptic cells in close proximity.

Question 21

What are growth cones? What do they depend on?

Answer 21

Growth cones are found on axons of embryonic nerve cells and sense and move toward particular chemical signals.
They depend on growth factors, molecules in the extracellular matrix, and membrane proteins.

Question 22

What is myelin? What does it do?

Answer 22

Myelin is a substance composed of multiple concentric layers of phospholipid membrane wrapped around an axon.
It provides structural support, insulation to speed up electrical signals, and supplies trophic factors.

Question 23

What are oligodendrocytes?

Answer 23

Forms myelin. Wraps the axons of multiple neurons in the CNS - up to 50.

Question 24

What are Schwann Cells?

Answer 24

Forms myelin in the PNS. One cell wraps around a segment of one neuron.

Question 25

Where are satellite glial cells found? What do they do?

Answer 25

Found within ganglia in the PNS. Form a supportive capsule around the cell bodies of neurons (sensory and autonomic). Also provide nutrients and structural support.

Question 26

What are astrocytes? What are their functions?

Answer 26

Astrocytes are highly branched glial cells in the CNS. Functions: - take up and release chemicals at synapses - provide neurons with substrates for ATP production - help maintain homeostasis in the extracellular fluid (take up K+ and H2O) - surround vessels (part of blood brain barrier)

Question 27

What are microganglia? What diseases can arise when mictroganglia display detrimental properties?

Answer 27

Microganglia are specialized immune cells in the CNS. They protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults. When showing detrimental properties, Alzheimer's disease, ALS, and neuropathic pain can occur.

Question 28

What are ependymal cells? What do they do?

Answer 28

Ependymal cells line fluid filled cavities in the brain and spinal cord, and are a possible source for neural stem cells. They help to circulate cerebral spinal fluid for protection, chemical stability, and clearing wastes.

Question 29

What happens when a neuron is injured?

Answer 29

In the CNS, repair is less likely to occur naturally, glia tend to seal off and form scar tissue. When the axon is cut, the section attached to the cell body continues to live while the section distal to the cut begins to disintegrate.

Question 30

What is the resting membrane potential equal to? What is it due to?

Answer 30

Equal to -70mV in most neurons. | Mostly due to K+, but Na+ contributes slightly.

Question 31

What causes mechanically gated channels to open? Where are they found?

Answer 31

Open in response to physical forces such as pressure or stretch. Found in sensory neurons.

Question 32

What do chemically gated ion channels respond to?

Answer 32

In neurons, they respond to ligands including extracellular neurotransmitters and neuromodulators or intracellular signalling molecules.

Question 33

What do voltage gated channels respond to?

Answer 33

Respond to changes in the cell's membrane potential.

Question 34

What are channelopathies? What do they do?

Answer 34

Channelopathies are a mutation in the DNA responsible for creating ion channels. Can disrupt how ions normally flow through the ion channel and can alter channel activation and inactivation. (cystic fibrosis, congenital insensitivity to pain, muscle disorders).

Question 35

What are two sources of resistance in a cell?

Answer 35

1. membrane resistance: resistance of the phospholipid bilayer. 2. internal resistance of the cytoplasm: cytoplasmic composition and size of cell.

Question 36

What are graded potentials? What are they generated by?

Answer 36

variable strength signals that travel over short distances and lose strength as they travel. They can be depolarizing or hyperpolarizing. Generated by chemically gated ion channels or closure of leak channels.

Question 37

What are action potentials?

Answer 37

Very brief, large depolarizations that travel for long distances through a neuron without losing strength.

Question 38

Excitatory vs Inhibitory graded potentials

Answer 38

Excitatory: depolarization, increase the chance of generating an action potential. Inhibitory: hyperpolarization, prevents an action potential from being generated.

Question 39

What is there a high concentration of on the axon hillock (trigger zone)?

Answer 39

High concentration of voltage gated Na+ channels

Question 40

How many mV must the membrane potential be for an action potential to be generated?

Answer 40

-55mV