Chp 11: Fundamentals of Nervous System and Nervous Tissue

Question 1

Basic fxns of the nervous system

Answer 1

Complex network for communication btwn external environment and body homeostasis mechanisms & btwn internal environments and homeostasis mechanisms

Question 2

5 basic components of nervous system fxns

Answer 2

1. sensor
2. sensory neuron pathway (sensory input)
3. integration center
4. motor neuron pathway (motor output)
5. effector

Question 3

Structural divisions of nervous system

Answer 3

CNS: brain and spinal cord
PNS: mostly cranial and spinal nerves

Question 4

Functional divisions of nervous system

Answer 4

Sensory/Afferent division of PNS: conveys impulses to CNS
Motor/efferent division of PNS: conveys impulses from CNS; efferent division includes somatic (voluntary) and autonomic (involuntary) systems

Question 5

Neuron

Answer 5

functional cell of the nervous system
cell body/soma 5-140 µm
specialized, slender processes:
dendrites: input region
axon: conducting component
secretor/output region: axon terminal

Question 6

Structural classes of neurons: multipolar

Answer 6

many dendrites, one axon
most common class of neuron

Question 7

Structural classes of neurons: bipolar

Answer 7

one dendrite, one axon

in special sensory organs

Question 8

Structural classes of neurons: unipolar

Answer 8

one short, single process
dendrite, axon continuous
afferent neurons

Question 9

Functional classes of neurons: sensory/afferent

Answer 9

conduct action potential from PNS toward CNS

Question 10

Functional classes of neurons: motor/efferent

Answer 10

conduct action potential away from CNS to PNS

Question 11

Neuroglia: Satellite cells

Answer 11

PNS
Surround neuron cell bodies in ganglia
Regulate 02, CO2, nutrient,and neurotransmitter levels around neurons in ganglia

Question 12

Neuroglia: Schwann cells

Answer 12

PNS
Surround axons in PNS
Are responsible for myelination of peripheral axons
Participate in repair process after injury

Question 13

Neuroglia: Oligodendrocytes

Answer 13

CNS
Myelinate CNS axons
Provide structural framework

Question 14

Neuroglia:astrocytes

Answer 14

CNS
Maintain blood-brain barrier
Provide structural support
Regulate ion, nutrient, and dissolved gas concentrations
Absorb and recycle neurotransmitters
Form scar tissue after injury

Question 15

Neuroglia: microglia

Answer 15

CNS

remove cell debris, wastes, and pathogens by phagocytosis

Question 16

Neuroglia: ependymal cells

Answer 16

CNS
line ventricles (brain) and central canal (spinal cord)
Assist in producing, circulating and monitoring of cerebrospinal fluid

Question 17

Myelin sheath: PNS

Answer 17

Formed by Schwann cells
Neurilemma: outermost layer of Schwann cell, bulge of Schwann cell’s nucleus and most of the cytoplasm
Nodes of Ranvier: myelin sheath gaps (adjacent Schwann cells do not touch each other)

Question 18

Myelin sheath: CNS

Answer 18

Formed by oligodendrocytes that have multiple flat processes and can coil around 60 axons at same time
Lacks neurilemma

Question 19

Myelination

Answer 19

Whitish, fatty sheath along length of axon
Electrically insulates axon
Increases speed of nerve impulse transmission
Helps neural regeneration in PNS
Amount of myelination increases from birth to maturity

Question 20

Destruction of myelin sheath (demyelination)

Answer 20

multiple sclerosis

Question 21

Tracts

Answer 21

Bundles of neuron processes in CNS

Question 22

Nerves

Answer 22

Bundles of neuron processes in PNS

Question 23

Nuclei/Nucleus

Answer 23

Clusters of cell bodies in CNS

Question 24

Ganglia/Ganglion

Answer 24

Clusters of cell bodies in PNS

Question 25

Resting membrane potential

Answer 25

Potential difference in resting neuron cytoplasmic charge (inside) of the membrane is negatively charged (-70 mV)

Question 26

Graded potentials

Answer 26

short-lived, localized changes in membrane potential that cause current flows
Either hyperopolarizations or depolarizations
Magnitude varies directly with stimulus strength
Triggered by stimulus in neuron’s environment that opens gated ion channels

Question 27

Action potential

Answer 27

Brief reversal of membrane potential with total amplitude of about 100 mV (-70 to +30 mV)
Only generated by cells with excitable membranes (neurons and muscle cells)

Question 28

Synapse

Answer 28

site of communication between 2 neurons or a neuron and an effector

Question 29

Presynaptic neuron

Answer 29

nerve conducting impulses toward the synapse (sends info)

Question 30

Postsynaptic neuron

Answer 30

Neuron transmitting electrical signal away from synapse (receives info)
Outside CNS, postsynaptic cell may be neuron or effector cell (muscle cell or gland cell)

Question 31

Neurotransmitters

Answer 31

Signaling chemicals usually stored in vesicles that are released into extracellular space (synapse)
Can either excite or inhibit neurons (or effector cells)

Question 32

Direction of nerve signal travel

Answer 32

Can only go in one direction

Dendrite –> cell body –> axon –> axon bulbs –> next neuron/effector