1. Ch. 43 Review Warm-Up Contrast the functions of B cells and T cells.
What are memory cells?
How do vaccines work?
How does HIV affect the immune system?

2. Warm-Up Draw and label the parts of a neuron.
Describe saltatory conduction.
Explain how a nerve impulse is transmitted across a neuron.

3. Warm-Up What happens at the synapse?
Choose 1 neurotransmitter. Describe its action.
What is the role of the following structures in the human brain?
Brainstem
Cerebellum
Cerebrum
Corpus callosum

4. Chapters 48 & 49 Campbell Biology – 9th ed.
Nervous Systems
Chapters 48 & 49
Campbell Biology – 9th ed.

5. You must know The anatomy of a neuron.
The mechanisms of impulse transmission in a neuron.
The process that leads to release of neurotransmitters, and what happens at the synapse.
How the vertebrate brain integrates information, which leads to an appropriate response.
Different regions of the brain have different functions.

6. Organization of the Nervous System
Central nervous system (CNS) = brain + spinal cord
Peripheral nervous system (PNS) = nerves throughout body
Sensory receptors: collect info
Sensory neurons: body  CNS
Motor neurons: CNS  body (muscles, glands)
Interneurons: connect sensory & motor neurons
Nerves = bundles of neurons
Contains motor neurons +/or sensory neurons

7. Neuron Functional Differences
Integrates and coordinates info from afferent, sends out response to efferent

11. Peripheral Nervous System
Somatic
nervous
system
Autonomic
nervous
system
Sympathetic
division
Parasympathetic
division
Enteric
division

13. Neuron = dendrite + cell body + axon

14. Neuron cell body: contains nucleus & organelles
dendrites: receive incoming messages
axons: transmit messages away to other cells
myelin sheath: fatty insulation covering axon, speeds up nerve impulses
synapse: junction between 2 neurons
neurotransmitter: chemical messengers sent across synapse
Glia: cells that support neurons
Eg. Schwann cells (forms myelin sheath)

15. Schwann cells and the myelin sheath

16. Myelin sheath Axon coated with Schwann cells
Insulation material (lipid)
speeds up signal
saltatory conduction
Signal “jumps” between gaps in myelin sheath
150 m/sec vs. 5 m/sec (330 mph vs. 11 mph)
signal
direction
myelin sheath

17. Multiple Sclerosis action potential saltatory conduction Na+ myelin +–
axon + + + + –
Na+
Multiple Sclerosis
immune system (T cells) attack myelin sheath
loss of signal

18. BioFlix: How Neurons Work

19. Membrane Potential: difference in electrical charge across cell membrane
Microelectrode
–70 mV
Voltage
recorder
Reference
electrode

20. Neuron at Resting Potential
Opposite charges on opposite sides of cell membrane
membrane is polarized
negative inside; positive outside
charge gradient (-70mv)
stored energy (like a battery) +
This is an imbalanced condition.
The positively + charged ions repel each other as do the negatively - charged ions. They “want” to flow down their electrical gradient and mix together evenly.
This means that there is energy stored here, like a dammed up river.
Voltage is a measurement of stored electrical energy. Like “Danger High Voltage” = lots of energy (lethal). – – +

21. What makes it polarized?
Cells live in a sea of charged ions
anions (negative)
more concentrated within the cell
Cl-, charged amino acids (aa-)
cations (positive)
Na+ more concentrated in the extracellular fluid
Salty Banana!
channel leaks K+ K+
Na+ K+
Cl-
aa- + – K+

22. The Na+/K+ pump (using ATP) maintains a negative potential inside the neuron.

23. Action potentials (nerve impulses) are the signals conducted by axons
Resting potential: membrane potential at rest; polarized
Na+ outside, K+ inside cell
Voltage-gated Na+ channel = CLOSED
Nerve impulse: stimulus causes a change in membrane potential
Action potential: neuron membrane depolarizes
All-or-nothing response
Na+ channels open
K+ channels open
Na+ enters cell
K+ leaves cell

24. How does a nerve impulse travel?
Stimulus: nerve is stimulated
reaches threshold potential
open Na+ channels in cell membrane
Na+ ions diffuse into cell
charges reverse at that point on neuron
positive inside; negative outside
cell becomes depolarized
The 1st domino goes down! – +
Na+

25. Depolarization Wave: nerve impulse travels down neuron – +
change in charge opens next Na+ gates down the line
“voltage-gated” channels
Na+ continues to diffuse down neuron
“wave” moves down neuron = action potential
Gate + –
channel closed
channel open
The rest of the dominoes fall! – +
Na+
wave 

26. Voltage-gated channels
Ion channels open & close in response to changes in charge across membrane
Structure & function!
Na+ channel closed when nerve isn’t doing anything.

27. Repolarization Re-set: 2nd wave travels down neuron + –
K+ channels open
K+ channels open up more slowly than Na+ channels
K+ ions diffuse out of cell
charges reverse back at that point
negative inside; positive outside
Set dominoes back up quickly! + –
Na+ K+
wave 
Opening gates in succession =
- same strength
- same speed
- same duration

28. How does a nerve impulse travel?
wave of opening ion channels moves down neuron
flow of K+ out of cell stops activation of Na+ channels in wrong direction
Animation
Ready for next time! + –
Na+
wave  K+

29. How does the nerve re-set itself?
Sodium-Potassium pump
active transport protein in membrane
requires ATP
3 Na+ pumped out
2 K+ pumped in
re-sets charge across membrane
ATP
Dominoes set back up again.
Na/K pumps are one of the main drains on ATP production in your body. Your brain is a very expensive organ to run!
That’s a lot of ATP !
Feed me some sugar quick!

31. Conduction of an action potential

32. Action potential graph
Resting potential
Stimulus reaches threshold potential
Depolarization Na+ channels open; K+ channels closed
Na+ channels close; K+ channels open
Repolarization reset charge gradient
Undershoot K+ channels close slowly
40 mV 4
30 mV
20 mV
Depolarization
Na+ flows in
Repolarization
K+ flows out
10 mV
0 mV
–10 mV 3 5
Membrane potential
–20 mV
–30 mV
–40 mV
Hyperpolarization
(undershoot)
–50 mV
Threshold
–60 mV 2
–70 mV 1
Resting potential 6
Resting
–80 mV

33. All or nothing response
Once first one is opened, the rest open in succession
a “wave” action travels along neuron
have to re-set channels so neuron can react again
How is a nerve impulse similar to playing with dominoes?

34. Nerve Impulse Animation

35. Saltatory conduction speed: 120 m/sec
Saltatory conduction: nerve impulse jumps between nodes of Ranvier (unmyelinated gaps)  speeds up impulse
Saltatory conduction speed: 120 m/sec

36. BioFlix: How Synapses Work

37. Cell communication: neurotransmitter released at synapses Axon (presynaptic cell)  Dendrite (postsynaptic cell)

38. The Synapse ion-gated channels open
Action potential depolarizes membrane
Opens Ca++ channels
Neurotransmitter vesicles fuse with membrane
Release neurotransmitter to synapse  diffusion
Neurotransmitter binds with protein receptor
ion-gated channels open
Neurotransmitter degraded or reabsorbed
axon terminal
action potential
synaptic vesicles
synapse
Ca++
Calcium is a very important ion throughout your body. It will come up again and again involved in many processes.
neurotransmitter acetylcholine (ACh)
receptor protein
muscle cell (fiber)
We switched…
from an electrical signal
to a chemical signal

39. Neurotransmitters
Chemicals released from vesicles by exocytosis into synaptic cleft
Diffuse across synapse
Bind to receptors on neurons, muscle cells, or gland cells
Broken down by enzymes or taken back up into surrounding cells
Types of neurotransmitters:
Excitatory: speed up impulses by causing depolarization of postsynaptic membrane
Inhibitory: slow impulses by causing hyperpolarization of postsynaptic membrane

41. Examples of Neurotransmitters
Acetylcholine (ACh): stimulates muscles, memory formation, learning
Epinephrine: (adrenaline) fight-or-flight
Norepinephrine: fight-or-flight
Dopamine: reward, pleasure (“high”)
Loss of dopamine  Parkinson’s Disease
Serotonin: well-being, happiness
Low levels  Depression
GABA: inhibitory NT
Affected by alcohol

42. Weak point of nervous system
Any substance that affects neurotransmitters or mimics them affects nerve function
Ex: Gases, drugs, poisons
Acetylcholinesterase inhibitors = neurotoxins!
Ex: snake venom, insecticides
Selective serotonin reuptake inhibitor
Snake toxin blocking acetylcholinesterase active site

43. Mouse Party

44. Reflexes Simple, automatic response to a stimulus
Conscious thought not required
Reflex arc:
Stimulus detected by receptor
Sensory neuron
Interneuron (spinal cord or brain stem)
Motor neuron
Response by effector organ (muscles, glands)

45. Knee-jerk reflex

46. Vertebrate Brains Evolutionary trends towards “Cephalization”
Central region for integrating and coordinating information.
Different regions have different functions:

47. Forebrain  cerebrum
Midbrain  brainstem
Hindbrain  cerebellum

48. Human Brain Structure Function Cerebrum Brainstem Cerebellum
Information processing (learning, emotion, memory, perception, voluntary movement)
Right & Left cerebral hemispheres
Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
Basic, autonomic survival behaviors
Medulla oblongata –breathing, heart & blood vessel activity, digestion, swallowing, vomiting
Transfer info between PNS & CNS
Cerebellum
Coordinate movement & balance
Motor skill learning

49. Human Brain Structure Function Cerebrum Brainstem Cerebellum
Information processing (learning, emotion, memory, perception, voluntary movement)
Right & Left cerebral hemispheres
Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
Basic, autonomic survival behaviors
Medulla oblongata –breathing, heart & blood vessel activity, digestion, swallowing, vomiting
Transfer info between PNS & CNS
Cerebellum
Coordinate movement & balance
Motor skill learning

50. Human Brain Structure Function Cerebrum Brainstem Cerebellum
Information processing (learning, emotion, memory, perception, voluntary movement)
Right & Left cerebral hemispheres
Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
Basic, autonomic survival behaviors
Medulla oblongata –breathing, heart & blood vessel activity, digestion, swallowing, vomiting
Transfer info between PNS & CNS
Cerebellum
Coordinate movement & balance
Motor skill learning

51. Human Brain Structure Function Cerebrum Brainstem Cerebellum
Information processing (learning, emotion, memory, perception, voluntary movement)
Right & Left cerebral hemispheres
Corpus callosum: connect hemispheres
Brainstem
*Oldest evolutionary part*
Basic, autonomic survival behaviors
Medulla oblongata –breathing, heart & blood vessel activity, digestion, swallowing, vomiting
Transfer info between PNS & CNS
Cerebellum
Coordinate movement & balance
Motor skill learning

52. Grey matter: neuron cell bodies, unmyelinated axons White matter: fatty, myelinated axons

53. Discovery Video: Teen Brains