Nervous Tissue Histo

Question 1

functions of the NS

Answer 1

1. gather info/sensory input via sensory receptors
2. process and interpret sensory input and decide what action to take (integration)
3. produce response or motor output activating effector organs

Question 2

divisions of the NS

Answer 2

CNS: integrative and control centers of body, brain and SC
PNS: communication btwn CNS and rest of body, all structures outside of CNS (CN, spinal nerves, ganglia, plexuses)

Question 3

types of cells found in nervous tissue

Answer 3

1. nerve cells/neurons

2. neuroglia/glia/supporting cells

Question 4

characteristics of nerve cells/neurons

Answer 4

excitable, irritable (can produce/transmit APs), cannot undergo mitosis

Question 5

characteristics of neuroglia

Answer 5

don’t produce APs, more numerous than neurons, do mitosis

Question 6

special characteristics of neurons

Answer 6

1. extreme longevity: last over 100 years
2. most are amitotic: lose ability to divide as they set up synapses
3. high metabloic rate: dead w/in a few min w/out O2

Question 7

structural components of neurons

Answer 7

1. neuron cell body

2. processes

Question 8

types of processes on neurons

Answer 8

1. dendrites

2. axons

Question 9

neuron cell bodies

Answer 9

• perikaryon*
• fnctn as biosynthetic center of neuron
• no centrioles (no mitosis)
• always unmyelinated (no APs
• have Nissl bodies

Question 10

Nissl bodies

Answer 10

dark spots of RER and free ribosomes, only visible with hematoxylin

Question 11

dendrites

Answer 11

• fnctn as main receptive/input region of neuron
• always unmyelianted (no APs)
• neurons can have 1 or more
• dendritic spines give lots of surface area

Question 12

axons

Answer 12

(nerve fiber)

• fnctn to conduct signal/generate and transmit APs
• can be myelinated
• neurons only have 1
• axon terminals release NT (after influx of Ca and depolarization) onto another neuron or effector cell
• anterograde or retrograde transport

Question 13

structural classes of neurons

Answer 13

1. multipolar: 3 or more processes (most abundant)
2. bipolar: 2 processes (rare, in special senses)
3. unipolar: 1 process (mainly in PNS)

Question 14

functional classes of neurons

Answer 14

1. sensory/afferent: toward CNS
2. motor/efferent: away from CNS
3. interneurons/association: found between motor and sensory

Question 15

function of multipolar neurons

Answer 15

sensory, motor, or interneuron

Question 16

function of bipolar neurons

Answer 16

motor/efferent only

Question 17

function of unipolar neurons

Answer 17

motor/efferent only

Question 18

synapse classifications

Answer 18

1. axodendritic: axon terminal -> dendrite
2. axosomatic: axon terminal -> cell body
3. axoaxonic: between axons
4. dendrodendritic: between dendrites
5. dendrosomatic: dendrite -> cell body

Question 19

varieties of synapses

Answer 19

1. electrical

2. chemical

Question 20

electrical synapses

Answer 20

• AP conducted directly btwn adjacent cells via gap jnctns

- found where fast responses are required

Question 21

chemical synapses

Answer 21

• slower than electrical

- have to go electrical - chem - electrical

Question 22

steps in chemical synapse

Answer 22

1. impulse arrives at presynaptic axon
2. depolarization, voltage gated Ca channels open
3. Ca signals for release of NT via exocytosis
4. NT binds to NT receptor at postsynaptic membrane (part of ligand gates channel)
5. binding of NT opens channels, ions flow across mem
6. local changes in mem potential (post synaptic potential)

Question 23

how can NT be removed from postsynaptic receptor?

Answer 23

1. degradation by enzymes
2. reuptake by astrocytes or presynaptic terminal
3. diffusion away from synapse

Question 24

types of neuroglia

Answer 24

1. oligodendrocytes
2. astrocytes
3. ependymal cells
4. microglia
5. schwann cells
6. satellite cells

Question 25

oligodendrocytes

Answer 25

- line up in rows - have condensed round nuclei and unstained cytoplasm - have processes that wrap around a couple different axons in CNS -> myelination

Question 26

astrocytes

Answer 26

- star shaped - in CNS - lots of functional diversity - patrol ionic environment around neurons, regulate [K] - helps w/ BBB (transfers substances between vessels and neurons

Question 27

ependymal cells

Answer 27

- low columnar/cuboidal - line ventricles and central canal of SC - have cilia to flow CSF - make up choroid plexuses that make CSF

Question 28

microglia

Answer 28

- in grey and white matter - can see spikes w/ special staining - elongated nucleus - originate as monocytes - can proliferate - analyze tissue for damaged cells

Question 29

schwann cells

Answer 29

* neurolemmocytes* - produce myelin in PNS - 1 cell = 1 myelin sheath

Question 30

satellite cell

Answer 30

- in PNS - surround cell bodies of neurons in gnaglions - fnctn in metabolic exchange and structural support

Question 31

white matter

Answer 31

composed primarily of myelinated axons and some neuroglia

Question 32

grey matter

Answer 32

composed of neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia grey bc Nissl bodies and no myelin

Question 33

what is a bundle of neuronal axons in PNS?

Answer 33

nerve

Question 34

what is a bundle of neuronal axons in CNS?

Answer 34

tract

Question 35

what is a cluster of neuronal cell bodies in PNS?

Answer 35

ganglion

Question 36

what is a cluster of neuronal cell bodies in CNS?

Answer 36

nucleus

Question 37

what are the components of a nerve?

Answer 37

1. neuron processes 2. schwann cells 3. CT 4. BVs 5. lymphatic vessels

Question 38

what is the organization of a nerve?

Answer 38

1. endoneurium: surrounds nerve fibers 2. perineurium: forms fascicles 3. epineurium: surround entire nerve

Question 39

fnctn of myelin

Answer 39

1. protect/electrically insulate axons | 2. increase speed of nerve impulse transmission

Question 40

node of ranvier

Answer 40

where AP is regenerated between sections of myelin

Question 41

factors for impulse propagation rate

Answer 41

1. axon diameter: larger = faster | 2. myelination: continuous = unmyelinated, saltatory = myelinated