Biology Chapter 4: The Nervous System

Question 1

What are neurons?

Answer 1

Highly specialized cells responsible for conduction of impulses.

Question 2

How do neurons communicate using electrical communication?

Answer 2

Via ion exchange and the generation of membrane potentials down the length of the axon.

Question 3

How do neurons communicate using chemical communication?

Answer 3

Via neurotransmitter to the postsynaptic cell and the binding of these neurotransmitters to the postsynaptic cell

Question 4

What are dendrites?

Answer 4

Appendages that receive signals from other cells

Question 5

What is the soma?

Answer 5

location of the nucleus as well as organelles, including the ER and ribosomes

Question 6

What is the axon hillock?

Answer 6

Where the cell body transitions to the axon and where action potentials are initiated

Question 7

What is the axon?

Answer 7

It is a long appendage down which an action potential travels.

Question 8

What is the nerve terminal or synaptic bouton?

Answer 8

End of the axon from which neurotransmitters are released.

Question 9

What are nodes of ranvier?

Answer 9

exposed areas of myelinated axons that permit saltatory conduction.

Question 10

What is the synapse?

Answer 10

nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell and the space between called the synaptic cleft

Question 11

What is myelin?

Answer 11

It is an insulating substance that prevents signal loss. Prevents dissipation of the neural impulse and crossing of neural impulses from adjacent neurons.

Question 12

What is myelin created by?

Answer 12

oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system

Question 13

What are axons bundled into?

Answer 13

Nerves or tracts

Question 14

What is the difference between nerves and tracts?

Answer 14

Nerve may carry multiple types of information - cell bodies of the same type cluster in ganglia in the PNS
Tracts contain only one type of information - cluster in nuclei in the CNS

Question 15

What are neuroglia?

Answer 15

cells within the nervous system in addition to neurons

Question 16

What are astrocytes?

Answer 16

nourish neurons and form the blood-brain barrier , which controls the transmission solutes from the bloodstream into the nervous tissue

Question 17

What are ependymal cells?

Answer 17

line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.

Question 18

What are microganglia?

Answer 18

phagocytic cells that ingest and break down waste products and pathogens in the CNS

Question 19

What is the resting membrane potential of neurons?

Answer 19

-70 mV

Question 20

What maintains the resting potential of neurons?

Answer 20

Maintained using selective permeability of ions as well as the Na+/K+ pump, which pumps three sodium ions out of the cell for every two potassium in

Question 21

What are the two types of incoming signals?

Answer 21

Excitatory signals that cause depolarization of the neuron

Inhibitory signals that cause hyperpolarization of the neuron

Question 22

What is temporal summation?

Answer 22

the addition of multiple signals near each other in time

Question 23

What is spatial summation?

Answer 23

the addition of multiple signals near each other in space

Question 24

What is an action potential?

Answer 24

It is used to propagate signals down the cell

Question 25

What is the process of an action potential?

Answer 25

1. Cell is depolarized when it reached a threshold voltage & sodium channels open
2. Sodium flows into the cell
3. At the peak, sodium channels are inactivated and potassium channels are opened
4. K+ flows out to repolarize, overshoot resulting in a hyperpolarized neuron, then the K+ channels close
5. The Na+/K+ pump beings the neuron back to resting potential and restores the gradient

Question 26

What is the refractory period? absolute? relative?

Answer 26

refractory - when it is hyperpolarized
absolute - unable to fire another action potential
relative - needs a larger than normal stimulus to fire an action potential

Question 27

What is the process of neurotransmitters activating?

Answer 27

1. action potential arrives at the nerve terminal, voltage gated Ca2+ channels open
2. Ca2+ causes vesicles with neurotransmitters with the presynaptic membrane, resulting in exocytosis into the synaptic cleft.
3. N.T. bind to receptors on the postsynaptic cell, which may be ligand-gated ion channels or G protein-coupled receptors

Question 28

What are 3 ways the neurotransmitters can be cleared out of the postsynaptic cleft?

Answer 28

enzymatically broken down.
absorbed back into the presynaptic cell
diffuse out of the cleft

Question 29

What are the three types of neurons?

Answer 29

Motor (efferent)
Interneurons
Sensory (afferent)

Question 30

In the CNS, what is white matter?

Answer 30

myelinated axons

Question 31

In the CNS, what is grey matter?

Answer 31

unmyelinated cell bodies and dendrites.

Question 32

What type of matter is deeper in the brain? spinal cord?

Answer 32

brain - white

spinal - grey

Question 33

What is the PNS divided into?

Answer 33

somatic and autonomic

Question 34

What is the autonomic split into?

Answer 34

parasympathetic (rest and digest)

sympathetic (fight or flight)

Question 35

What are reflex arcs?

Answer 35

use the ability of the interneurons in the spinal cord to relay information to the source of stimuli while simultaneously routing it to the brain.

Question 36

What is a monosynaptic reflex arc?

Answer 36

the sensory neuron fires directly into the motor neuron

Question 37

What is a polysynaptic reflex arc?

Answer 37

sensory neuron may fire onto a motor neuron as well as interneurons that fire onto other motor neurons.