the brain, divisions of the nervous system, and neurons

1. The Nervous System

2. Objectives
Content
Label and describe the
major divisions of the
nervous system
Skill
Use models and
representations

3. The command
center of the body
The brain contains over 100 billion neurons (nerve
cells)
Each one of those connected to 100s of others
Incredibly complex
MRIs have allowed scientists to “see” into the brain
Have found that certain regions dedicated to certain tasks

4. Evolution of the Nervous System
All animals (except sponges) have some sort of
nervous system

5. 7 Characteristics of Life
Cells
DNA
Grow and develop
Maintain homeostasis
Respond to the environment
Reproduction
Use materials and energy

6. Quick Think
All living things are able to RESPOND TO THEIR
ENVIRONMENT
With a partner – come up with at least 3With a partner – come up with at least 3
different organisms and how theydifferent organisms and how they respondrespond
to their environmentto their environment
Be prepared to share

9. hibernation
estivation
migration

12. Nervous system in mammals
1. Central Nervous
System (CNS)
1. Brain + spinal cord
2. Peripheral
Nervous System
(PNS)
1. All the nerves that run
throughout the body

13. THE CENTRAL NERVOUS
SYSTEM

14. The Brain
Cerebrum - 2 hemispheres, controls your
senses (seeing, hearing, tasting, feeling,
smelling), learning and memory.

15. Each side has 4 lobes:
Frontal Temporal
Occipital Parietal

16. Cerebellum - coordination, decision
making, consciousness, awareness of
surroundings

17. Brainstem - Controls breathing rate,
arousal & sleep, swallowing, digestion

18. Quick Think
Identify the 3 major regions of the
human brain
Give 1 specific function of each region

19. Can you identify the lobes of
the brain?
1.
2.
3.
4.

20. Spinal Cord
Controls reflexes
Examples:
tickling  laughter/twitching
Pupil constriction
Cough and sneeze reflex
Infants grasp and root
Withdraw reflex

22. Peripheral Nervous System
Somatic nervous
system – parts you
control
Autonomic
nervous system –
parts controlled
automatically
Sympathetic
division - increased
heart rate, adrenaline,
fight-or-flight
Parasympathetic
division - opposite
effect, calming

23. Quick think
You have to give a speech to a large
audience and feel nervous. What parts
of the nervous system would be
especially active in this case?

24. Sensory Organs

25. Taste
Tastebuds –
food molecules
trigger a message
to the brain

27. Nose – olfactory bulb sends
message to brain

28. Eyes
Compound eyes
(insects,crustaceans) - have 1000s of
light detectors and lenses
Single lens eye (vertebrates, some
inverts)

29. Pupil - hole in center of iris
Retina - contains photorecptor
cells
Rods - very light sensitive cells
Cones - cells that distinguish color
Optic nerve –
exits the eye
and creates a
blind spot

30. Your Blind Spot
Draw a small X on the right side of
your paper
Measure 5 inches from the left of the
X and make a dot the size of a penny
Hold the paper in front of you and
close your right eye. Look at the X.
Can you still see the dot?
Slowly move the paper, while always
looking at the X. When the dot
disappears, you have found your
blind spot.

31. Ears
Outer ear – pinna
Collects sounds & direct them to tympanic
membrane (eardrum)

32. Middle ear - 3 small bones vibrate
(malleus, incus, stapes)
Inner ear - cochlea – tiny hairs vibrate and
send message to the brain

33. Skin – many different kinds of
sense receptors

34. Senses and your brain
Your brain interprets messages –
sometimes in a strange way

35. Neurons – the cells of the
nervous system

36. Neurons
Cell body – contains nucleus & organelles

38. Neurons
Dendrites –receive incoming messages

40. Neurons
Axon – conveys message to the next cell

42. Myelin Sheath – covers axon and helps
messages travel faster

44. Synapse – the space at
the end of the axon
where the message is
passed with a chemical
neurotransmitter

45. Synapse

46. Messages
always travel in
one direction
Message is
electrical inside
the neuron, then
chemical at the
synapse
https://www.youtube.com/watch?v=dSkxlpNs3tU
Synapse
Electrical

47. Neurons
There are 3 types of
neurons
They must work together
to pass messages

48. Neuron #1
SENSORY Neuron
Found throughout the body
Take in information
They “sense”
Examples:
Temperature around you
Temperature inside you
Amount of light in the room
Your blood sugar level
Pain
Tickles
Others?

49. Neuron #1
SENSORY Neuron
What information is this
neuron sensing?
Draw in a sensory neuron on
your diagram in red.
Add an arrow to show the
direction the message is
traveling.

50. Quick Check
1s answer this question:
What does a SENSORY
neuron do?
2s answer this question:
What are some things it
might SENSE?
Answer on whiteboards

51. Neuron #2
INTERNEURONSINTERNEURONS
These are in the brain and
spinal cord
They receive the message
from the sensory neuron
and interpret it
They “think”

52. Neuron #2
INTERNEURONSINTERNEURONS
Add these neurons in
yellow to your diagram
Add a light bulb to show
they “think”

53. Quick Check
What is the role of interneurons in the
nervous system?
Fronts tell behinds . Behinds will
answer.

54. Neuron #3
MOTOR Neurons
Send message from brain
to an effector cell (muscle
or gland)
This causes a response in
the body
The “run the motor” of your
body

55. Neuron #3
MOTOR Neurons
Before we draw in a motor
neuron…
Where will it START?
Where will it END?
Draw in the motor neuron
in blue
Add in an arrow to show
the direction the message
is traveling

56. Quick Check
What does a motor
neuron do?
Everyone answer on whiteboards

58. 3 main types of neurons
Sensory neurons –
collect info from inside
(blood pressure, blood
CO2 levels, etc) &
outside the body (light,
temperature, taste, etc)

59. Interneurons
– neurons in
CNS that
analyze &
interpret the info
from the
sensory neuron
and connect to
motor neurons
to elicit a
response

60. Motor neurons – send signals
from the CNS to the body
Messages sent to effector cells
Effector cells are muscle cells or
gland cells that carry out a particular
response

61. An example of a nerve circuit
The reflex arc – a
reflex is a body’s
automatic response
to stimuli
Sensory neuron
receives info
Passes message to
spinal cord
(interneurons)
Message passed to
motor neuron
Motor neuron signals
an effector cell
Response is initiated

62. Dendrites, cell body, axon,
sensory neuron, interneuron,
motor neuron, stimulus, effect

63. How neurons send messages
Part 1: Electrical message within
the neuron

64. Q: What is membrane potential?

65. All cells maintain an
electrical potential
difference (voltage)
across their plasma
membrane
The membrane
potential is maintained
by a difference in ionic
composition on either
side of the membrane
For neurons- the
resting potential is the
membrane potential
when the cell is not
transmitting a signal

66. Q: What is membrane potential?
A: A difference in charge between the
inside and outside of the cell
membrane

67. Q: How is this membrane potential created?

68. Neurons have ion
channels in the membrane
The sodium/potassium
pump protein (Na+
/K+
) uses
active transport (ATP) to
maintain the resting
potential

69. Q: How is this membrane potential created?
A: by proteins in the cell membrane called
sodium/potassium (Na+
/K+
) pumps

70. Q: Why “potential”? I get “membrane”…but
what does the “potential” part mean?
A: It refers to potential energy – the
potential to do work for the cell

71. Q: So how do Na+
/K+
pumps work?
A: they move 3 Na+
out of cell and 2 K+
into cell so there is an overall negative
charge inside the cell

72. Q: What is “resting” potential?
A: normal voltage (~-70 mV) when a
neuron is inactive

73. A stimulus of some
sort affects the
permeability of the
membrane to
certain ions
This gives rise to a
nerve impulse we
call an action
potential

74. Q: What is an “action” potential?

75. The Action PotentialAction Potential (aka
nerve impulse)
They are the signals
conducted by the
axons
An all or none
reaction
It starts with a
stimulus that causes
the depolarization
of the neuron
Na+
ion channels
open and Na+
enters
the cell
This reverses the
charges (+ inside
and – outside)

76. The action
potential ends as
Na+
channels are
closed and K+
channels are
opened
This helps return
the neuron to its
resting potential

77. Action potentials move down the axon
Saltatory conduction is the jumping
of the nerve impulse between the
nodes of Ranvier
This speeds up nerve impulses

78. Q: What is an “action” potential?
A: a stimulus opens ion
channels in cell
membrane that allow Na+
to rush into cell, reversing
electrical potential. This
impulse jumps from node
of Ranvier to node of
Ranvier until it reaches
the synapse

79. Q: How does it all go back to normal?
A: The Na+
/K+
pump

80. How the message is passed
to the next neuron
From the axon of one
cell to the dendrites of
then next through the
synapse
Electrical
synapse (a few) -
electrical current
flows from cell to cell
via gap junctions
Chemical synapse
(most) - the release
of a neurotransmitter

81. The Chemical Synapse
Neurotransmitter
binds to receptors on
the plasma
membrane of the next
neuron
This triggers an
action potential in the
next neuron