1. IV] THE NERVOUS SYTEM

2. dendrites
receptors of stimuli 1
body of cell
source of ions 2 3
nucleus
source of proteins eg. pumps 4
Schwann cells
fats that insulate the neuron 5
Nodes of Ranvier
gaps in the insulation 6
axon
path of electrical signal

3. 1. Dendrite 5. Nodes of Ranvier 2. Cell body 4. Schwann cells
8. Terminal Bouton
7. Axon Terminal
5. Nodes of
Ranvier
2. Cell body
4. Schwann cells
9. Axon Hillock
3. Nucleus
6. Axon

4. K+ K+ Na+ Na+ Na+ Na/K pump K+ gate Na+ gate Na+ Na+ K+ K+ K+ K+
inside of neuron
Na+ Na+
Na Na+
Na+
outside of neuron

5. 1. The Na/K pump - pumps 2 K+ in and 3 Na+ out of the neuron
2. The K+ gate - allows K+ to freely move out of neuron
3. The Na+ gate - usually these are partly closed, and so only allows some of Na+ to move back into neuron

6. 4. The result
- there are more Na+ ions outside of neuron which gives it a positive charge outside
- because there are Cl- ions equally inside and out, the inside of the neuron now has a negative charge after some of the Na+ ions have moved outside
- the net result is a -70 mV negative charge inside the neuron compared to outside

10. A. Resting potential

11. B. Stimulus
Na+

12. C. Propagating signal
Na+
Na+

13. D. Further propagation of signal

14. 4. ACTION POTENTIAL
                                                                            

15. +40 mV 0 mV -70 mV MILLISECONDS C. REPOLARIZING B. DEPOLARIZING A
A. RESTING POTENTIAL
D. HYPERPOLARIZATION
E. REFRACTORY PERIOD

16. 4. ACTION POTENTIAL A. RESTING POTENTIAL - the Na/K pumps are ON
- Na+ gates are CLOSED
B. DEPOLARIZING
- the Na/K pumps are OFF
- the Na+ gates are OPEN
C. REPOLARIZING
- the Na/K pumps are ON
- the Na+ gates are CLOSED

17. D. HYPERPOLARIZATION
- the Na/K pumps are ON
- the Na+ gates are CLOSED
- extra positive ions are pumped out, making a larger electrical difference
E. REFRACTORY PERIOD
- the time during which the neuron can NOT respond to a new signal

19. F. THRESHHOLD VALUES
- a neuron is either ON or OFF, there are no part signals
if a stimulus does not reach the threshold level, the neuron is not activated
- a stronger stimulus results in the sending of MORE signals
or more neuron sending the same signals

20. 5. SALTATORY CONDUCTION - in mylenated cells

21. A. RESTING POTENTIAL

22. B. STIMULUS
Na+

23. C. PROPAGATING THE SIGNAL

24. D. FURTHER PROPAGATION OF SIGNAL

25. mylenated neurons send the signal faster
mylenated neurons send the signal faster as the signal jumps under the Schwann cells
thicker neurons have more pumps and more ions and so they can depolarize and repolarize faster

26. Synapses between neurons

27. 6. PROPAGATING A SIGNAL ACROSS A SYNAPSE
synaptic cleft
Ca2+
axon
dendrite

28. 1. INCOMING ELECTRICAL SIGNAL-arrives at the axon end of the synapse2
1. INCOMING ELECTRICAL SIGNAL-arrives at the axon end of the synapse
axon 3 1
2. CALCIUM CHANNELS -are triggered to open and let Ca2+ ions enter the axon
Ca2+ 2
3. PRE-SYNAPTIC VESICLES
-the Ca2+ causes pre-synaptic vesicles to move to the end of the axon

29. RECEPTORS -the neurotransmitter binds to receptors in the dendrite
-the pre-synaptic vesicles release neurotransmitter [acetylcholine] into the synaptic cleft [space]
synaptic cleft
RECEPTORS -the neurotransmitter binds to receptors in the dendrite 7
dendrite 4
6. OUTGOING ELECTRICAL SIGNAL
-the neurotransmitter / receptor complex [N/R complex]initiates an electrical signal in the dendrite 6 5
7. ENZYME
- an enzyme [acetylcholinesterase] is released from the dendrite to get rid of acetylcholine and stop the N / R complex from initiating another electrical signal

30. responsible for muscle contractions nerve / muscle synapses
neurotransmitter
location
function
ACETYLCHOLINE
responsible for muscle contractions
nerve / muscle synapses
role in emotions such as depression, aggression, impulsive behaviour
SEROTONIN
in brain synapses
role in dreaming, arousal, moodiness
NOREPINEPHRINE
in brain synapses
modifies nerve signals eg reduces pain sensitivity
BETA-ENDORPHINS & ENKEPHALINS
in all synapses
affects control of movement, emotions, pleasure , pain
DOPAMINE
in brain synapses
GLYCINE & GABA
in brain synapses
inhibit signals
in brain synapses
most common
involved in memory
GLUTAMINE
too much kills brain cells

31. mylenation proceeds from the back to the front as you age

32. “Problems with neurons”
Now work on…………
“Problems with neurons”