How a nerve works

Question 1

The spinal chord is made up of 31 pairs of spinal nerves. What are they ?

Answer 1

8 cervical (neck, shoulders & arms)
12 thoracic (chest & abdomen)
5 lumbar (hips & legs)
5 sacral (genitalia/gastrointestinal tract)
1 coccygeal

Question 2

Explain how a common spinal nerve works

Answer 2

Sensory neurone travels into spine via dorsal root and motor info travels out via ventral root.

Question 3

Neurones are made up of what?

Answer 3

• Cell body (soma)
• Dendrite
• Initial segment
• Axon
• Axon (pre-synaptic) terminals

Question 4

Dendrite function

Answer 4

Receives information from other neurones

Question 5

Initial segment function

Answer 5

Triggers action potential, by arranging all the information

Question 6

Axon function

Answer 6

Sends action potential

Question 7

Axon terminals function

Answer 7

release action potential, by acting on receptors of next cell to create electrical signal

Question 8

What are the three types of neurones and which nervous system are they in ?

Answer 8

Afferent (sensory): PNS
Interneurones: CNS
Efferent (motor): PNS

Question 9

REVIEW DIAGRAM of normal nerve

Answer 9

sec-c

Question 10

What is Glia?

Answer 10

connective tissue of the nervous system

Question 11

Name thee types of glia

Answer 11

oligodendrocytes, astroglia, microglia

Question 12

What is the normal resting membrane potential?

Answer 12

-70mV

Question 13

What is the equilibrium potential?

Answer 13

The equilibrium potential is the membrane potential at which the electrical gradient is exactly equal and opposite to the concentration gradient. ie the concentration gradient determines the equilibrium potential.

Question 14

When does a cell become depolarised?

Answer 14

When RMP goes above or at 0mV.

Question 15

When does a cell become hyperpolarised?

Answer 15

When the RMP goes below -70mV, ~ -90mV

Question 16

Explain leaky K+ channels

Answer 16

The leak channels allow Na+ and K+ to move across the cell membrane down their gradients (from a high concentration toward a lower concentration). With the combined ion pumping and leakage of ions, the cell can maintain a stable resting membrane potential.

Question 17

What role does a graded potential play?

Answer 17

determine when an action potential is fired

Question 18

Name different graded potentials and where they are located

Answer 18

• Generator potnetials: at sensory receptors
• Postsynaptic potnetials: at synapses
• Endplate potentials: at NMJ
• Pacemaker potntials: in pace maker tissues

Question 19

What are the desired qualities of a graded potential?

Answer 19

• graded
• decremental
• depolarising
• hyperpolarising
• non-propagating
• can summate

Question 20

What does it mean that graded potentials are graded?

Answer 20

The stronger the stimulus, the more channels are opened, bigger current flow and therefore bigger potential.

Question 21

REVIEW DIAGRAMS of IPSP and EPSP

Answer 21

8////} ~~

Question 22

What do ligand gated ion channels produce when neurotransmitters open/close these channels?

Answer 22

Postsynaptic potentials

Question 23

What do voltage gated ion channels produce when depolarisation of membrane potential occurs

Answer 23

an action potential is generated

Question 24

EPSP channels

Answer 24

Open Na+/K+ channels

close k+ channels

Question 25

IPSP channels

Answer 25

opening Cl- channels or opening K+ channels (Review big diagram)

Question 26

Main properties of an action potential include:

Answer 26

- All or none - Encode by frequency - Cannot summate - Evoked at threshold - Refractory period - Self-propagating - Depolarising - Voltage-gated channels - Sends electrical signal over long distances