Chapter 7 - Nervous System I (Neurons)

Question 1

Afferent (Sensory )Neurons Definition

Answer 1

Neurons carrying messages TO the CNS

*Located in Dorsal Root Ganglion

Question 2

Efferent (Motor) Neurons Definition

Answer 2

Neurons carrying messages FROM the CNS

*Located in grey matter of spinal cord
(leaves CNS and goes to skeletal muscle)

Question 3

Dendrites Definition

Answer 3

Projection from cell body that carry messages TO cell body

Question 4

Axons Definition

Answer 4

Large projection that carry messages AWAY from cell body

Question 5

Interneuron Definition

Answer 5

Located between sensory and motor neurons , within the CNS

• Integrate and interpret sensory signals

Question 6

Myelin Definition

Question 7

Myelin Sheath Definition

Question 8

Myelinated Neurons Definition

Answer 8

Neurons with axons covering neuroglial cells that contain protein myelin

*Carry messages faster than non-myelinated neurons

Question 9

Schwann Cells Definition

Answer 9

Form myelin sheaths

*Found in PNS

Question 10

Oligodendrocytes Definition

Answer 10

Form myelin sheaths

*Found in CNS

Question 11

Nodes of Ranvier Definition

Answer 11

Spaces on axon between glial cells

Question 12

Ions Definition

Question 13

Ion Channels Definition

Question 14

Action Potential Definition

Answer 14

Sodium ions and Potassium ions crossing cell membrane through Ion channels

• Ion channel designed to only allow certain ions to pass through

Question 15

Repolarization Definition

Answer 15

Caused by potassium ions leaving axon

*When potassium ions open up and allow K+ OUT of the axon, making the inside negative

(action potential travels down the axon)

Question 16

Depolarization Definition

Answer 16

Caused by Sodium ions entering the axon

• When sodium ions open and sodium rushes in, making the INSIDE positively charged

Question 17

Membrane Potential Definition

Answer 17

Difference in charge between inside and outside of neuron

Question 18

Resting Potential Definition

Answer 18

A neuron not conduction a message

*When a neuron is resting, there is MORE Sodium OUTSIDE cell and MORE Potassium INSIDE cell

*Inside of the cell has a negative charge compared to the outside cell

Question 19

Sodium Potassium Pump Definition

Answer 19

To maintain a resting membrane , neurons pump Sodium OUT of the cell and Potassium INTO the cellf

(this is active transport = requires ATP)

Restores original conditions of pumping sodium OUT of the cell and potassium back IN

Question 20

Synapse Definition

Answer 20

Junction between two neurons or between neuron and muscle

Question 21

Synaptic Cleft Definition

Answer 21

The gap between presynaptic neuron and post-synaptic neuron

Question 22

Synaptic Vesicles Definition

Answer 22

Small vesicles that are clustered at presynaptic terminals

*Store neurotransmitters and release them by calcium triggered exocytosis

Question 23

Neurotransmitters Definition

Answer 23

A chemical messenger that the body can’t function without

Question 24

Acetylcholine Definition

Answer 24

Acts in both PNS and CNS as a neurotransmitter

*Causes voluntary muscles to contract

Question 25

Central Nervous System (CNS) Definition

Answer 25

Brain and Spinal Cord

Question 26

Peripheral Nervous System (PNS) Definition

Answer 26

Nervous tissue outside brain and spinal cord *Sense organs

Question 27

Neurons Definition

Answer 27

Cells responsible for transmitting messages

Question 28

Neuroglial Cells Definition

Answer 28

Cells that support the neurons

Question 29

Microglia Definition

Answer 29

Immune system cells, engluf bacteria and cellular debris

Question 30

Cell Body Definition

Answer 30

Contains the nucleus, main body of cell

Question 31

Functions of Myelin Sheaths

Answer 31

1. The main benefit of myelin sheaths is that myelinated neurons are able to carry messages faster than non-myelinated neurons 2. Myelin sheaths from Schwann cells also help regenerate injured PNS neuron axons

Question 32

Multiple Sclerosis (MS) Definition

Answer 32

Destruction of Myelin Sheath that surrounds axons in CNS *Results in : Paralysis , loss of sensation , loss of vision

Question 33

Refractory Period Definition

Answer 33

Sodium channels inactive for awhile after action potential passess

Question 34

Transmission across the synaptic cleft

Answer 34

1. The action potential gets to the end of the presynaptic axon 2. The action potential triggers Ca2+ to enter the presynaptic axon terminal 3. The Ca2+ triggers synaptic vesicles located at the axon terminal to merge with the neural membrane Transmission across the synaptic cleft 4. The synaptic vesicles release the neurotransmitters into the synaptic cleft 5. These neurotransmitters travel across the synaptic cleft to the postsynaptic neuron (or the muscle) 6. Neurotransmitter binds to receptors on the postsynaptic neuron (or muscle) 7. These receptors are ligand-gated sodium ion channels that allow Na+ to enter the postsynaptic neuron (or muscle) and trigger an action potential in the postsynaptic neuron (or muscle contraction) 8. Once the neurotransmitters are released they need to be destroyed or contained quickly or they will continue to stimulate the nerve

Question 35

Myasthenia Gravis Definition

Answer 35

Autoimmune disease that attacks the acetylcholine receptors, resulting in reduced muscle strength