The nervous system has two main divisions - the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord and is responsible for most information processing. The peripheral nervous system connects the brain and spinal cord to other organs of the body and has sensory, motor, and complex nerves. The nervous system uses neurons and neurotransmitters to transmit signals as electrical or chemical impulses in order to coordinate bodily functions and responses.

1. Nervous
System
Do not get nervous to nervous system 
Shohrat Meredow R

2. Homeostasis
• Constant internal balance of an organism.
• There are two systems that control homeostasis:

3. • There are two systems that control homeostasis:
• 1. Hormonal system
• 2. Nervous system

4. Nervous system
• Communication system of body
• Only animals have nervous systems, not plants

5. Neurons
• Neurons are specialized cells of nervous system.

8. Nervous system
• Event
• Receptor-Sense
• Signal
• Neurons
• Effector organs
• Response

9. Nervous system
• The nervous system connects the receptors to the
effectors, evaluates messages and transmits a
suitable signal

10. Stages of nervous system
• Reception
• Transmission
• Interpretation
• And response

11. Neurons

12. Structure of Neurons
• A nerve cell is composed of following components:
• Dendrites
• Cell body
• Axon

13. Dendrites
• They are short, thin projections extending from the
cell body.
• Their function is to receive information from other
neurons.

14. Cell body
• Largest part of neurons
• Cell body contains nucleus of the cell

15. Axon
• Same to dendrite
• But it is single and long and thick.
• Length varies
• Axon of giraffe is 3 meters
• Axon of mouse is about 10-15 cm

16. Structure of an axon

17. • Schwann cells: surround axons and protects them
• Myelin layer: insulating material, contains neuroglial
cell membrane
• Nodes of Ranvier: accelerate the speed of impulse
transmission.

18. Classification of Neurons
• 1. According to morphology (structure)
• 2. According to function

19. Structural classification
• Unipolar neuron: only one short projection extends
from the cell body.
• Bipolar neuron: two parallel projections extend from
the cell body. One is axon, the other is dendrite.
• Multipolar neuron: more than two projections
extend. Generally only one axon is present.

21. Functional classification
• Sensory neurons: transmit stimuli from sensory organs
to the CNS. They are unipolar or bipolar.
• Inter neurons: are commonly found in the CNS and
interconnect sensory and motor neurons. Main
function is interpretation of information. They are
multipolar in structure.
• Motor neurons: transmit the information from CNS to
the muscles or glands. They are also multipolar in
structure.

23. Video
• http://www.youtube.com/watch?v=rqtcecWa8aQ

24. Transmission of impulse
• Nerve impulses are electrical signals produced by
plasma membrane of a neuron.

25. • Impulses are unidirectional.
From dendrites to axons.

26. Threshold level
• The impulse is generated if the voltage reaches a
certain critical point, called threshold level.
• If signal is lower than threshold level, no impulse is
generated. This is called all-or-non law.

28. Generation of an impulse
• There are three phases:
1. Polarization
2. Depolarization
3. And repolarization

29. 1. Polarization
• In a resting nerve, the outside of axon is positively
charged, and inside is negatively charged. This
situation is called polarization.

30. Gates
• Ion gates:
1. Na gates
2. K gates
• Na-K pump

31. 2. Depolarization
• A stimulus that reaches the threshold level opens
the Na gates first.
• Na goes inside the axon.
• This is depolarization.

33. 3. Repolarization
• Then, Na gates are closed
and K gates are open.
• K goes out of the cell,
so the action potential returns
to the resting potential.

36. Video
• Nerve impulse:
• http://www.youtube.com/watch?v=9euDb4TN3b0

37. Video
• Animation
• http://www.youtube.com/watch?v=9euDb4TN3b0

38. The Synapses
• In the nervous system, a synapse is a structure that
permits a neuron to pass an electrical or chemical
signal to another cell (neural or otherwise).

41. 1. Presynaptic cell: the neuron that carries the
impulse to the synapse.
2. Postsynaptic cell: the cell that receives
impulse, and it is located after the signal.
• Synaptic cleft: a little gap between 1 & 2

43. Neurotransmitters
• Neurotransmitters are chemicals that transmit
signals from a neuron to a target cell across
a synapse.

45. Video
• http://www.youtube.com/watch?v=90cj4NX87Yk

46. Quiz:
1. Write the types of neurons according to function:
Functional classification:
A:
B:
C:
2. What are the three stages of an impulse? Explain briefly.

47. Human Nervous System
• Two main divisions:
1. Central nervous system
2. Peripheral nervous system

48. Central Nervous System
• It consists of the brain and spinal cord.
• These two structures are responsible for most the
information processing.

49. The Brain
• Most important organ of nervous system.
• Average brain weights about 1200-1350 in
males, and 1000-1250 in females.

50. The Brain
• Protection of the CNS:
There are three levels of protection:
1. Bony protection
2. Membrane protection
3. Fluid protection

51. The Brain
1. Bony protection:
Brain: skull
Spinal cord: vertebral column

52. Skull

53. The Brain
2. Membrane protection:
Both brain and spinal cord is protected with three
main layers called meninges.
3. Fluid protection: Cerebrospinal fluid functions as a
shock absorber.

54. The Brain
• The brain consists three main parts:
1. Forebrain
2. Midbrain
3. Hindbrain

55. 1. Forebrain
• It is largest portion of brain.
• Composed of:
a. The cerebrum
b. The diencephalon

56. 1. Forebrain
1.a. Cerebrum: Most active and largest part of the
brain.
• Cerebral cortex
• Corpus callosum

57. 1. Forebrain
Cerebral cortex has four main sections:
• Frontal lobe
• Temporal lobe
• Parietal lobe
• Occipital lobe

58. 1. Forebrain
• There are three major activities of cerebral cortex:
1. Motor area: related to movement of body parts
2. Sensory area: receive information.
3. Association area: mental activities.

59. 1. Forebrain
1.b. Diencephalon
• Consists of thalamus and hypothalamus.
Thalamus: relay station of information
Hypothalamus: regulation of body temperature,
control of feelings. (anger, pain, pleasure, thirst,
hunger)

60. 2. Midbrain
• Responsible for the head
and eye movement.

61. 3. Hindbrain
• Composed of:
1. Medulla oblongata
2. Cerebellum
3. Pons

62. 3. Hindbrain
1. Medulla oblongata:
It regulates respiratory, circulatory and excretory
activities and many involuntary activities such as
glucose metabolism, vomiting, sneezing.

63. 3. Hindbrain
2. Cerebellum: it is connected to midbrain and
medulla oblongata.
• It coordinates the movement of voluntary muscles
• It is the center of locomotion and balance.
• No cerebellum, no walk.

64. 3. Hindbrain
3. Pons: it controls certain respiratory functions.

65. 2. The Spinal Cord

66. 2. The Spinal Cord
• It is a brain extension.
• Protected by:
1. Spinal bond
2. Meninges
3. Cerebrospinal fluid

67. 2. The Spinal Cord

68. 2. The Spinal Cord
• Functions:
1. Transmission of impulses to
the brains and tissues
2. Facilitation of reflex actions
Reflex is an automatic response to nerve stimulation.

69. The spinal nerves:

70. The spinal nerves:
• There are 31 spinal nerves, each one is called a
segment.
• They are classified according to the area of body
with which they communicate

72. The spinal nerves:
• Cervical nerves: 8
• Thoracic nerves: 12
• Lumbar nerves: 5
• Sacral nerves: 5
• Coccyx: 1

73. Reflex
• Next lecture 

74. Reflex
• Is a transmission of impulses, generated by
receptors, to the target, where a sudden response is
generated.
• Reflex is an automatic response to nerve
stimulation.

75. Reflex
• Example

76. Reflex
• Knee-jerk reflex

78. Types of reflexes
1. Withdrawal reflex: is inherited, not gained from
experience.
Eg: stepping on a nail.

79. • 2. Conditional reflexes: stored by the brain after the
experience.

80. The Peripheral Nervous System

81. The Peripheral Nervous System
• PNS consists of nerves that connect the brain and
spinal cord to the other organs of the body.
• It has sensory nerves, motor nerves and complex
nerves.

82. • PNS originates from brain and spinal cord.
• It is composed of 12 pairs of cranial (coming from
brain) and 31 pairs of spinal (coming from spinal
cord) nerves.

84. Classification of PNS
• It is divided into two systems:
1. Somatic nervous system
2. Autonomic nervous system

85. 1. Somatic nervous System
• It consists of both motor and sensory nerves.
• This system controls and coordinates the voluntary
actions of the body.
• Running
• Writing
• Talking
• Painting

86. 1. Somatic nervous System

87. 2. Autonomic nervous system
• It regulates the involuntary activities of internal
organs and basically involved in the maintenance
of homeostasis.
• Regulation of:
• Respiration
• Circulation
• Excretion
• Digestion
• Nutrition
• Reproduction
• Adaptation

88. • The effector organs
of ANS are smooth
muscles of internal
organs, cardiac
muscles and glands.

89. Classification of ANS
1. The sympathetic system
2. The parasympathetic system
They function antagonistically.

90. Sympathetic NS
• It initiates the fight-or-flight response.
• It is especially important for emergency. It
accelerates the heart beat and dilates bronchi.
• It inhibits the digestive activity. Because we do not
need it in emergency
• The primary neurotransmitter is epinephrine.

92. Parasympathetic NS
• It is called “housekeeper system”
• This system prepares the body to relaxation and
digestion of food.
• Retards heartbeat.
• The main neurotransmitter is acetylcholine.

94. Nervous system disorders
• akinesia - no movement.
• Alzheimer's disease - A progressive, degenerative
disease that occurs in the brain and results in
impaired memory, thinking, and behavior.
• ataxia - loss of balance
• athetosis - slow, involuntary movements of the
hands and feet.
• stroke (also called brain attack) - happens when
brain cells die because of inadequate blood flow to
the brain.
• meningitis - an inflammation of the meninges, the
membranes that cover the brain.

95. Akinesia

96. Alzheimer's disease

97. Ataxia

98. Athetosis

99. Stroke

100. Meningitis

101. AVOID!!!
• Alcohol
• Cigarettes
• Drug

104. Review?

105. • Shohrat Meredov R
