This lesson material includes essential information about neurological foundations of behavior. This tackles the brain specifically the nervous system and neurons.

1. UNIT II: NEUROLOGICAL
FOUNDATIONS OF
BEHAVIOR

2. The Nervous System
• Is the complex arrangement throughout
the body of highly specialized cells, the
nerve cells or neurons, which act as
communication system, enabling the
organism to respond to external and
internal stimuli.

3. The function of a nervous system is to
gather and process information, produce
responses to stimuli, and coordinate the
working of different cells.

4. • Even the simplest tasks require smooth
functioning of the communications system
that we call nervous system.
• When there is a problem in the
communication process, people have
trouble.
• It underlies all behavior, including tasks
like reading, writing, and talking.

5. • In some ways, the nervous system acts
like the conductor of a symphony
orchestra, sending, receiving, processing,
interpreting, and storing vital information.
• Studying how the nervous system’s
components work together and how they
are integrated, help a great deal in
learning about the nature and diversity of
human behavior.

6. Nervous System
Central Nervous
System
Peripheral Nervous
System
brain spinal cord somatic
nervous system
(controls voluntary movements
of skeletal muscles)
autonomic
nervous system
(controls involuntary
muscles like internal
organs and glands)
sympathetic
nervous system
(emergency & stressful situations)
parasympathetic
nervous system
(calming or at rest)

7. Central Nervous System
• Consists of the brain and spinal cord
• The spinal cord is a narrow column that
starts at the base of the back and extends
up through the neck and into the base of
skull. It is the main pathway to and from
the brain.
• The brain is the location of most
information processing.

8. • Receives, processes, interprets, and
stores incoming sensory information-
information about tastes, sounds, smells,
color, pressure on the skin, the state of
internal organs, and so forth.

9. The Peripheral Nervous System
• Handle’s the central nervous system’s
input and output
• Contains all portions of the nervous
system outside the brain and spinal cord,
right down to the nerves in the tips of the
fingers and toes.

10. Somatic Nervous System
• Sometimes called the skeletal nervous
system
• Consists of nerves that are connected to
sensory receptors – cells that enable you
to sense the world
• Skeletal muscles that permit voluntary
action

11. Autonomic Nervous System
• Regulates the functioning of blood
vessels, glands and internal (visceral)
organs such as the bladder, stomach and
heart.

12. The Nervous System

13. NEURONS-NERVE CELLS
• cells that are the basic unit of the nervous
system
• responsible for conducting information
throughout the nervous system
• the building blocks of the brain
• gives that brain its unique characteristics,
such as the ability to sense the environment,
to think and learn, and to control the muscles
of the body
• the brain contains between 100 and 200
billion neurons in the brain alone
• each neuron can communicate with about
1000 other neurons
 This number of cells is necessary to support the
complexities of human behavior

14. Glial Cells
The nervous system is consist of a large
number of non neural cells called glial
cells and often surround neurons.
• Greek word “glia” meaning glue because of
their function which is to hold neurons in place.
• It supply, support and transport nutrients to the
neurons. It is 10 times as numerous as
neurons.
• They are not specialized to receive or transmit
signals rather they provide structural and
metabolic support, and serve in other ways to
ensure that neurons can perform their
functions.

15. Parts of the Neuron

16. dendrites- Greek word for “tree” because they looked
like tree branches. It is the receiving end of the neuron.

17. soma or cell body – lies between the dendrites
and the axon.

18. axon - the sending portion of a neuron.

19. myelin sheath

20. Axon terminal or terminal button

21. Parts of the Neuron

22. Types of Neuron
• Sensory/Afferent Neurons
• Association Neurons or Interneurons
• Motor/Efferent Neurons

23. Sensory/Afferent Neuron
INPUT From sensory organs to the brain and spinal cord.
Responds directly to external stimuli such as light, sound
Spinal
Cord
Brain
Sensory
Neuron

24. Association Neurons/ Interneurons
Nerve cells in the brain and spinal cord responsible for
processing information related to sensory input and motor
output
Spinal
Cord
Brain
Sensory
Neuron

25. Motor/Efferent Neurons
OUTPUT From the brain and spinal cord to the
muscles and glands.
Spinal
Cord
Brain
Sensory
Neuron
Motor
Neuron

26. A Neural Chain

27. A Neural Chain

28. A Neural Chain

29. A Neural Chain

30. A Neural Chain

31. Communication
Between Neurons

32. Neural
Communication:
The Neural Impulse

33. Neural Impulse/Action Potential
• A message carried by a neuron
• Information in the nervous system is
principally encoded through a series of
signal.
Imagine yourself watching a neural impulse travel
down the neuron you would see the impulse start at
the dendrite, flash through the cell body, and then
burst down the axon. The entire event take place in a
fraction of a second.

34. Synapse
• Greek word meaning “point of contact”
• The tiny, fluid filled space or gap between the
axon terminals of one neuron and the dendrites
of another neuron
Having a synapse between two neurons is similar to
unplugging two extension cords where electricity
cannot flow. So if there are synapses between
neurons, impulses cannot jump the gap. So how
does the impulse bridge the synapse?
Ans.: The synapse is bridged by chemicals called
Neurotransmitters

35. Synapse

36. Neurotransmitters
• so called because they transmit energy from one
neuron to the next.
• A chemical messenger that travels across the
synapse from one neuron to the next
Where are the neurotransmitters located?
Neurotransmitters are found in the axon terminal or
terminal button.

37. Axon terminal or terminal button
• It is located at the end of the axon. Here the
molecules of the neurotransmitter group
together in the synaptic vesicles.
Synaptic vesicles – small, hollow, pear-shaped
structures located in the axon terminals.
Receptor – the portion of the dendrite into which
a neurotransmitter fits.

38. Neurotransmitters

42. Neural Impulses
The speed of the neural impulses as it travels down
the axon can vary from about 2 to 200 miles per
hour. Here are some factors that influence its
speed
• depending on the diameter of the axon with large ones
generally being faster.
• Conditions of the fiber – being altered or if drugged,
deprived of oxygen, fatigue or in an abnormal state.
• The speed can also be affected by whether or not the
axon is covered with myelin sheath.

43. Myelin Sheath
• consists of specialized glial cells that wrap themselves
around the axon one after another, with small gaps
between one and the next.
• White fatty casing on axon that acts as an electrical
insulator
• Not present on all cells
• When present increases the speed of neural signals
down the axon.
• The insulating function of the myelin sheath allows the
nerve impulse to virtually jump from gap to gap, thus
greatly increasing the speed of transmission.

44. Phases in the Neural
Communication

45. Action Potential
• A neural impulse
• A brief electrical charge that
travels down the axon of the
neuron.
• Considered an “on” condition of
the neuron
Phases in the Neural Communication

46. Refractory Period
• The “recharging phase” when a
neuron, after firing, cannot
generate another action potential
• Once the refractory period is
complete the neuron can fire again
Phases in the Neural Communication

47. • absolute refractory period – the period
during which the cell cannot fire again
regardless of how strongly it is stimulated.
• Relative refractory period – the cell will
fire if stimulated, although it take more
than the usual level of stimulation to fire.
Fired neurons usually recover fully in about
1/10th of a second.

48. Resting Potential
• The state of a neuron when it is at
rest and capable of generating an
action potential
• The neuron is set and ready to fire
Phases in the Neural Communication

49. All-or-None Principle
• the rule which states that the neuron either
responds completely or not at all depending
upon whether or not the stimulus has reached a
certain minimum strength, referred to as
threshold.
Ex. A scream is heard more intensely than a
whisper. A weak stimulus will excite a few fibers
and therefore may not result in a sensory
experience at all.

50. • The principle that if a neuron fires it will
always fire at the same intensity
• All action potentials are of the same
strength.
• A neuron does NOT fire at 30%, 45% or
90% but at 100% each time it fires.
All-or-None Principle

54. Neuron firing like a Toilet
1. Like a Neuron, a toilet has an action
potential. When you flush, an
“impulse” is sent down the sewer
pipe

55. Neuron firing like a Toilet
2. Like a neuron, a toilet has a
refractory period. There is a short
delay after flushing when the toilet
cannot be flushed again because the
tank is being refilled

56. Neuron firing like a Toilet
3. Like a Neuron, a toilet has a
resting potential. The toilet is
“charged” when there is water in
the tank and it is capable of being
flushed again
4. Like a Neuron, a toilet operates
on the all-or-none principle – it
always flushes with the same
intensity, no matter how much
force you apply to the handle

57. Neurotransmitters
• Over 50 different neurotransmitters
have been identified, moreover, some
neurotransmitters can bind to more
than one type of receptor molecule,
causing different effects.

58. If a neurotransmitter does not fit into a site on the
receiving neuron, the chemical message it delivers
is basically one of two types: Excitatory messages
and Inhibitory messages.
• Excitatory Message: A chemical message that
makes it more likely that the receiving neuron will
fire and an action potential will travel down its axon
(e.g. closing of hands).
• Inhibitory Message: A chemical message that
prevents or decreases the likelihood that a
receiving neuron will fire.
SYNAPSE AND NEUROTRANSMITTERS

59. Acetylcholine (ACh)
• widely used in peripheral nervous system as
either an excitatory or inhibitory
neurotransmitter
• In general, it is an excitatory transmitter but it
can be inhibitory depending on the type of
receptor molecule in the membrane of the
receiving neuron
• Affects neurons involved in muscle action,
cognitive functioning , memory and emotion

60. Acetylcholine (ACh)
• important for learning and memory
• prevalent in the area of the brain called
hippocampus – plays an important or key role
in the formation of new memories.
• drugs that increase acetylcholine seem to
facilitate learning and those that decrease it
appear to disrupt learning and memory.

61. • Acetylcholine is a very widely distributed
excitatory neurotransmitter that triggers
muscle contraction and stimulates the
excretion of certain hormones. In the
central nervous system, it is involved in
wakefulness, attentiveness, anger,
aggression, sexuality, and thirst, among
other things.

62. Acetylcholine (ACh)
ALZHEIMER’S DISEASE, a devastating
disorder that affects many older people,
involves impairment of memory and other
cognitive functions.
it has been demonstrated that brain cells producing
ACh tend to degenerate in Alzheimer’s patients
and the brain cells production of ACh is reduce,
the less ACh the brain produces, the more severe
the memory loss.

63. Norepinephrine (NE)
• helps controls alertness and arousal
• A norepinephrine deficiency may lead to a
depressed state and an excess may lead to a
manic state.
Two well known drugs cocaine and amphetamines prolong
the action of (NE) by slowing down the reuptake process.
Because of the delay in the reuptake the receiving neurons
are activated for a longer period of time, thus causing the
stimulating psychological effects of these drugs. In contrast,
lithium is a drug that speeds up the reuptake of NE, causing
a person’s mood level to be depressed.

64. • Affects neurons involved in increased
heart rate and the slowing of intestinal
activity during stress, and neurons
involved in learning, memory, dreaming
walking from sleep, and emotion

65. • Norepinephrine is a neurotransmitter that
is important for attentiveness, emotions,
sleeping, dreaming, and learning.
Norepinephrine is also released as a
hormone into the blood, where it causes
blood vessels to contract and heart rate to
increase.

66. Gamma-Aminobutyric Acid (GABA)
• one of the major inhibitory transmitter in
the nervous system.
• may be involved in the modulation of
anxiety
• Valium – increases the activity of GABA,
reducing anxiety

67. • GABA (gamma-aminobutyric acid) is an
inhibitory neurotransmitter that is very
widely distributed in the neurons of the
cortex. GABA contributes to motor control,
vision, and many other cortical functions.

68. Dopamine
• Affects neurons involved in voluntary
movement, learning, memory, and emotion
• associated with the thought and mood
disturbances of some psychological disorders,
as well as impairment of movement

69. Dopamine
• Too much dopamine at the synapse may cause
schizophrenia;
Chlorpromazine – a drug used to treat schizophrenia
blocks the receptors for dopamine and allows fewer
message to get through.
• too little results in PARKINSON’S DISEASE - a
neurological disease resulting in muscle
tremors

70. Serotonin
• Affects neurons involved in sleep, sensory
perception, temperature regulation, pain
suppression and mood.

71. Serotonin
• related to behaviors such as
sleep/wake cycle, and plays a role in
depression and aggression
• important in the sleep process
 A serotonin deficiency in the brain
produces insomnia

72. • Depression, suicide, impulsive behaviour,
and agressiveness all appear to involve
certain imbalances in serotonin

73. Glutamate
• Glutamate is a major excitatory
neurotransmitter that is associated
with learning and memory.

74. Endorphins
• Hypothesized to be involved in a variety of
behaviors including feeding, sexual
activity, blood pressure, mood, learning
and memory
• these chemicals also relieve pain and
promote pleasure, but they occur naturally
in the brain.
• “morphine within”

75. Endorphins
• Endorphin levels shoot up when an animal
or a person is afraid or under stress.
• making pain bearable in such situations

76. Synapse
Axon terminal of the
sending neuron
Dendrite of the
receiving neuron
Synapse