Ch. 4: The Nervous System

Question 1

Neurons

Answer 1

Highly specialized cells responsible for the conduction of impulses
- Communicate both electrically and chemically

Question 2

Electrical Communication

Answer 2

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

Question 3

Chemical Communication

Answer 3

Via neurotransmitter release from the presynaptic cell and the binding of these neurotransmitters to the postsynaptic cell

Question 4

Dendrites

Answer 4

Appendages that receive signals from other cells

Question 5

Soma

Answer 5

Cell body; location of the nucleus as well as organelles such as the endoplasmic reticulum and ribosomes

Question 6

Axon hillock

Answer 6

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

Question 7

Axon

Answer 7

Long appendage down which an action potential travels

Question 8

Nerve terminal or Synaptic Bouton

Answer 8

End of the axon from which neurotransmitters are released

Question 9

Nodes of Ranvier

Answer 9

Exposed areas of myelinated axons that permit saltatory conduction (signals hop from node to node)

Question 10

Synapse

Answer 10

Consists of the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two

Question 11

Synaptic Cleft

Answer 11

Space between the nerve terminal of the presynaptic neuron and the membrane of the postsynaptic cell

Question 12

Myelin:

Answer 12

Many axons are coated in myelin; an insulating substance which prevents signal loss– prevents dissipation of the neural impulse and crossing of neural impulses from adjacent neurons

Question 13

Oligodendrocytes

Answer 13

Create myelin in the central nervous system

Question 14

Schwann cells

Answer 14

Create myelin in the peripheral nervous system

Question 15

Nerves

Answer 15

• individual axons and bundled into nerves or tracts
• a single nerve may carry multiple types of info including sensory, motor, or both
• cell bodies of neurons of the same type within a nerve cluster in ganglia in the peripheral nervous system

Question 16

Tracts

Answer 16

• individual axons and bundled into nerves or tracts
• tracts contain only one type of info
• cell bodies of the individual neurons within a tract cluster in nuclei in the central nervous system

Question 17

Neuroganglia or Glial Cells

Answer 17

Other cells within the nervous sys in addition to neurons. Include astrocytes, ependymal cells, microglia, oligodendrocytes, and Schwann cells

Question 18

Astrocytes

Answer 18

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

Question 19

Ependymal cells

Answer 19

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

Question 20

Microglia

Answer 20

Phagocytic cells that ingest and break down waste products and pathogens in the central nervous system

Question 21

Resting membrane Potential

Answer 21

70 mV; maintained using selective permeability of ions as well as the Na+/K+ ATPase

Question 22

Na+/K+ ATPase

Answer 22

Pumps 3 Na ions out of the cell for every 2 K+ ions pumped in; K+ leak channel leaks K+ ions out causing negative potential

Question 23

Excitatory signals

Answer 23

Cause depolarization of the neuron

Question 24

Inhibitory signals

Answer 24

Cause hyperpolarization of the neuron

Question 25

Temporal Summation

Answer 25

Refers to the addition of multiple signals near each other in time

Question 26

Spatial Summation

Answer 26

Refers to the addition of multiple signals near other in space

Question 27

Action Potential

Answer 27

Used to propagate signals down the axon. Relay electrical impulses down the axon to the synaptic bouton

Question 28

Depolarization

Answer 28

When enough excitatory stimulation occurs, the cell is depolarized to the threshold voltage and voltage gated sodium channels open

Question 29

Sodium Flow

Answer 29

Sodium flows into the neuron due to its strong electrochemical gradient to continue depolarizing the neuron

Question 30

Peak of the Action Potential

Answer 30

+35 mV; sodium channels are inactivated and potassium channels open

Question 31

Potassium Flow

Answer 31

Potassium flows out of the neuron due to its strong electrochemical gradient, repolarizing the cell. Potassium channels stay open long enough to overshoot the action potential, resulting in a hyperpolarized neuron; then the potassium channels close

Question 32

Return to Resting Potential

Answer 32

Na+/K+ ATPase bring the neuron back to the resting potential and restores the sodium and potassium gradients

Question 33

Refractory Period

Answer 33

While the axon is hyperpolarized

Question 34

Absolute Refractory Period

Answer 34

Cell is unable to fire another action potential

Question 35

Relative Refractory Period

Answer 35

The cell requires a larger than normal stimulus to fire an action potential

Question 36

How does an impulse propagate down the length of an axon?

Answer 36

The influx of sodium in one segment of the axon brings the subsequent of the axon to threshold. The fact that the preceding segment of the axon is in its refractory period means that the action potential can only travel in one direction

Question 37

Nerve Terminal

Answer 37

Site where neurotransmitters are released into the synapse; when the action potential arrives at the nerve terminal, voltage gated calcium channels open. The influx of calcium causes fusion of vesicles filled w neurotransmitter with the presynaptic membrane, resulting in exocytosis of neurotransmitter into the synaptic cleft. Neurotransmitters bind to receptors on the postsynaptic cell which may be ligand-gated ion channels of G protein-coupled receptors

Question 38

Stopping the Propagation of the signal

Answer 38

Neurotransmitters must be cleared from the postsynaptic receptors to stop the propagation of the signal. Neurotransmitter can be enzymatically broken down. Neurotransmitter can be absorbed back into the presynaptic cell by reuptake channels. Neurotransmitter can diffuse out of the synaptic cleft

Question 39

Types of neurons in the nervous system

Answer 39

Motor (efferent) neurons, Interneurons, and sensory (afferent) neurons

Question 40

Sensory neurons

Answer 40

Transmit sensory info from receptors to the spinal cord and brain

Question 41

Motor neurons

Answer 41

Transmit motor information from the brain and spinal cord to muscles and glands

Question 42

Interneurons

Answer 42

Found between other neurons and are the most numerous of the 3 types. Located in the mostly brain and spinal cord and are often linked to reflexive behavior

Question 43

The nervous system is made up of

Answer 43

Central nervous system (CNS) and the Peripheral Nervous system (PNS)

Question 44

Central Nervous system

Answer 44

Brain and spinal cord, white matter and gray matter

Question 45

White Matter

Answer 45

Consists of myelinated axons; in the brain, white matter is deeper than gray matter. In the spinal cord gray matter is deeper than white matter.

Question 46

Gray matter

Answer 46

Unmyelinated cell bodies and dendrites

Question 47

Peripheral Nervous System

Answer 47

Cranial and Spinal nerves; Divided into somatic (voluntary) and autonomic (involuntary) nervous systems

Question 48

Autonomic nervous system

Answer 48

Further divided into parasympathetic (rest and digest) and sympathetic (fight or flight) branches

Question 49

Reflex Arcs

Answer 49

Use the ability of interneurons in the spinal cord to relay info to the source of a stimulus while simultaneously routing it to the brain

Question 50

Monosynaptic reflex arc

Answer 50

Sensory (afferent, presynaptic) neuron fires directly onto the motor (efferent, postsynaptic) neuron

Question 51

Polysynaptic reflex arc

Answer 51

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