L2: Nervous Tissue

Question 1

Describe nervous tissue

Answer 1

cells specialized for conductivity and irritability- very responsive to stimuli

nervous system - communication system of body.
Divided into 3 parts: CNS, PNS, autonomic nervous system

Question 2

What are the 4 steps of nervous system communication

Answer 2

Receptor collects stimulus, transforms to electrical signals, passes signal to CNS (interpretation), and finally passes to effectors (response).

Question 3

CNS

Answer 3

brain and spinal cord

Question 4

PNS

Answer 4

spinal and cranial nerves and ganglia

Question 5

autonomic nervous system

Answer 5

viscerosensory nerves, ganglia and visceromotor nerves; two divisions: sympathetic and parasympathetic

Question 6

Unipolar neuron example

Answer 6

cell body and axon only (photoreceptor of the eye, embryonically)

Question 7

Bipolar neuron example

Answer 7

single axon and single dendrite

retina of eye, ganglia of auditory nerve

Question 8

Pseudounipolar neuron example

Answer 8

proximal regions of axon and dendrite fuse t oform single common segment leaving cell body

(spinal ganglia)

Question 9

multipolar neuron example

Answer 9

numerous dendrites and one axon (by far the most common)

Question 10

Nissl bodies

Answer 10

ribosome-rich regions of neuron cell body, active in protein synthesis; many mitochondria are also present indicating energetically active cell.

Question 11

Histological identifier of axon

Answer 11

no ribosomes. Pale staining axon hillock.

Question 12

Histological identifiers of dendrites

Answer 12

shorter and highly branched, larger regions with same subcellular components as cell body. Dark staining region for nissl bodies.

Question 13

histological identifiers of neuron cell body

Answer 13

usually large (4 um in retina, 120 um in motor neuron)

nucleus lies near center of cell body and is pale-staining but has single dark-staining nucleolus

within cytoplasm of cell body and proximal cell processes (dendrites only) are Nissl bodies.

Question 14

neurilemma

Answer 14

tough inelastic membrane formed by associated interstitial cells of axons (schwann cells in PNS, glial cells in CNS)

Question 15

Node of ranvier

Answer 15

act to increase velocity of conduction by allowing nerve impulse to jump from node to node (saltatory conduction) rather tha nproceed slowly down the plasma membrane as in unmyelinated neuron

Question 16

Describe the arrangement of fibers into nerves

Answer 16

endoneurium (areolar CT)
perineurium (makes a fascicle; dense lamellated CT)
epineurium (areolar CT) makes nerve.

Question 17

Invertebrate synapse

Answer 17

electrical, gap junctions through which ions may freely pass.

Question 18

vertebrate synapses

Answer 18

chemical, involves chemical mediators- NT

Question 19

Presynaptic terminal

Answer 19

portion which delivers impulse, usually is a terminal expansion of axon

Question 20

postsynaptic terminal

Answer 20

portion which receives impulse, usually a dendrite or less commonly a cell body and very rarely another axon; also can be an effector cell membrane (as in the neuromuscular junction)

Question 21

synaptic cleft

Answer 21

narrow space between pre- and postsynaptic terminals. (20 nm)

neurotransmitters - may have excitatory (depolarizing) or inhibitory (hyperpolarizing) effects

Question 22

cholinergic fibers

Answer 22

release acetylcholine

Question 23

adrenergic fibers

Answer 23

release norepinephrine;