Additions

Question 1

What is the effect of hyperkalemia on membrane potential?

Answer 1

i) Mild hyperkalemia: decrease K efflux → decrease the negativity of RMP i.e. less than - 70 mV (e.g. – 60 mV)→↑ excitability of nerve fibers
ii) Marked hyperkalemia: make the resting membrane potential to be more negative → inactivation of Na channels by h gates which close within 0.5 -1.0 m.sec of opening of m gate → decrease membrane excitability

Question 2

What is the number of neurons?

Answer 2

1 trillion

Question 3

What is the function of neuroglia?

Answer 3

Support & protect neurons.

Question 4

What is the number of neuroglia?

Answer 4

10: 50 times more than neuron

Question 5

CHARACTERISTICS of interneurons

Answer 5

 Small size.
 Inside CNS.
 99% of neurons. 
 Integrative function
 Connect afferents with efferents.

Question 6

What are the characters of the cell body?

Answer 6

 Enlarged part of the nerve that contains Contain nucleus, microfilament, and microtubule.
 Control metabolism and nutrition of nerve fibers.

Question 7

What is a collection of cell bodies called?

Answer 7

 Collection of cell bodies inside CNS called: centre = synapse = nucleus
 Collection of cell bodies outside CNS called: ganglia.

Question 8

What are the cell processes?

Answer 8

a) Axon (axis cylinder).

b) Dendrites.

Question 9

What are the characters of myelin or medullary sheath?

Answer 9

 Lipoprotein complex.
 Electric insulator.
 White in color
 Envelop all axon except axon terminal and nodes of ranvier
 Interrupted at every (.1-1mm) which is the site of exchange of ions and water.

Question 10

What are the characters of Schwan or cellular sheath?

Answer 10

 Not found inside CNS.
 Glia like.
 Its outer layer is called neurolemma.
 Regenerate damaged nerve fiber by the formation of the myelin sheath, only outside CNS.

Question 11

What is the nerve trunk formed from?

Answer 11

 Formed of multiple nerve fibers.
 Bundles of nerve fibers are surrounded by perineurium
 Inside the bundles: each nerve fiber is surrounded by endoneurium.
 The nerve is surrounded by loose connective tissue called epineurium and supplied by blood vessels.

Question 12

What is the function of the nerve trunk?

Answer 12

a) Sensory nerve: carry sensation from receptor to CNS.

b) Motor nerve: carry motor orders from CNS to the effector organ.