Chapter 9 - Nerve Tissue

Question 1

What is the function of nervous tissue?

Answer 1

• reception, processing and transmission of electrical and chemical signaling

Question 2

How many neurons do humans have?

Answer 2

> 100 bullion

Question 3

What are the functional divisions of the nervous system?

Answer 3

• autonomic - automatic responses, generally outside of your control
• voluntary - things we control

Question 4

What are the anatomical divisions of the nervous system?

Answer 4

• CNS - brain and spinal cord
• PNS - nerves and ganglia

Question 5

What is the PNS mainly responsible for?

Answer 5

• afferent(sensory) nerves receive info from the environment
• touch, vision, audition

Question 6

Neurons in the sensory ganglia have a slightly diff histological appearance than those in the CNS. True or false?

Answer 6

True

Question 7

What is the basic circuitry of an impulse?

Answer 7

• PNS axons have synapses in the sensory ganglia or CNS, info is then processed, then a response is then sent back into the PNS from the efferent neurons

Question 8

White matter

Answer 8

• axons/dendrites, neuroglia
• white due to myelin sheaths on some axons
• appear clear on a slide bc myelin is destroyed during fixing/staining

Question 9

Gray matter

Answer 9

neurons cell bodies and neuroglia

Question 10

Basic properties of neurons

Answer 10

• irritability, propagation of impulses
• very large cell body w/ prominent nucleus and nucleolus
• much larger than glial cells
• ribosomes are present
• nonmitotic

Question 11

What are the cell processes of neurons?

Answer 11

• axons - conduct signals (can be very long, and are (un)myelinated)
• dendrites - increase surface area, receive signals from other neurons

Question 12

What organelles are abundant in neurons? What type are well developed?

Answer 12

• RER, golgi
  
  • possess ribosomes, which are useful for making NTs

Question 13

What becomes visible in aged neurons? What is it?

Answer 13

• lipofuscin
• brownish pigment consisting of secondary lysosomes that have digestive material that have not been released from the cell

Question 14

Where do neurons communicate with each other?

Answer 14

• synapses
• place of chemical signaling through NTs

Question 15

What special stains are used for neurons?

Answer 15

• Nissl stains - rough ER
• osmium stain - myelin sheath
• silver stain

Question 16

What are the types of neurons?

Answer 16

• bipolar - 1 axon, 1 dendrite - located in retina, olfactory cells, cochlear and vestibular ganglia
• multipolar - 1 axon, many dendrites that branch from soma - most numerous
• unipolar - soma w/ single process that branches immediately - dorsal root ganglia and cranial ganglia

Question 17

Where are neuroglia more numerous than neurons?

Answer 17

• CNS

Question 18

Basic traits of neuroglia

Answer 18

• structural and nutritional support for neurons
• role in defense system of CNS
• most will die w/o glia
• do not transmit APs
• do not form synapses
• capable of mitosis
• all express glial fibrillary acidic protein (GFAP) - unique to glial cells (markers for immunohistochemcial staining)

Question 19

Oligodendrocytes

Answer 19

• glial cell in CNS
• makes myelin sheath
• allows for saltatory conduction of APs

Question 20

Astrocytes

Answer 20

• glial cell in CNS
• generally star shaped, most numerous of the glial cells
• necessary for controlling extracellular movement
• ## have end feet that envelop capillaries in the CNS - help to form BBB - protects brain

Question 21

BBB

Answer 21

• blood brain barrier
• composed of endothelial cells (tight junctions) and astrocyte processes
• restricts passage of molecules and pathogens into brain tissue

Question 22

Ependymal cells

Answer 22

• glial cells in CNS
• form and assist in circulation of CSF
• line ventricles of brain and central canal of spinal cord
• usually cuboidal

Question 23

Microglia

Answer 23

• glial cells in CNS
• phagocytic cells that are derived from monocytes
• short, branched processes

Question 24

Schwann cells

Answer 24

• glial cells in PNS
• form myelin sheaths in PNS, wrap numerous times around axons
• provides support to unmyelinated axons
• space btwn adjacent schwann cells are nodes of ranvier

Question 25

CT in PNS

Answer 25

- peripheral nerves are large bundles of nerve fibers (axons) - appear white due to myelin

Question 26

Epineurium

Answer 26

- external layer of dense CT in PNS

Question 27

Perineurium

Answer 27

- surrounds the smaller bundles of fibers (fascicles) in PNS

Question 28

Endoneurium

Answer 28

- surrounds each nerve fiber (very thin); reticular fibers, made by schwann cells in PNS

Question 29

What is the CNS protected/cushioned by?

Answer 29

- skull, vertebral column, meninges

Question 30

Meninges

Answer 30

- dura mater - dense regular CT - arachnoid - spider like with space beneath is filled by CSF - pia mater - innermost layer, processes of glial cells contact it

Question 31

CSF

Answer 31

- cushions bran and spinal cord - produced by ependymal cells in the 3rd and 4th ventricles - high in glucose, low in protein, has no cells other than occasional lymphocytes - reabsorbed by arachnoid into venous system

Question 32

Where are soma in the CNS and PNS?

Answer 32

- CNS - gray matter - PNS - ganglia and in specialized sensory regions (olfactory mucosa, vestibular ganglia)

Question 33

Synapses

Answer 33

- points of contact btwn neurons - NTs released here and bind to receptors in the post-synaptic membrane

Question 34

Neuronal regeneration

Answer 34

- do not divide in CNS - peripheral nerves can regenerate if the soma is not destroyed - upon injury, distal portion degenerates - Schwann cells proliferate and the proximal portion of an axon can regenerate - function can return is it reconnects with the correct schwann cells

Question 35

Polio

Answer 35

- poliomyelitis - virus enters motor neurons in ventral horns of SC - paralysis occurs if virus kills neurons - symptoms: weakness in arms and legs, tremor, trouble speaking and swallowing, post polio syndrome

Question 36

Glioma

Answer 36

- tumor arising from glial cells - resistant to many chemotherapeutic agents - Avg survival time ~ 12 months, rarely survive more than 3 yrs

Question 37

Alzheimers

Answer 37

- neurodegenerative disease that affects memory, coordination and eventually the individuals ability to function -

Question 38

What is AZ characterized by?

Answer 38

- amyloid plaques - extracellular deposits of beta amyloid, derived from abnormal proteolysis of amyloid precursor protein - Neurofibrillary tangles - tau, a microtubule stabilizing protein, forms abnormal clumps that interfere w/ the cytoskeleton's microtubules