The document provides an overview of the central nervous system. It discusses the main components and functions of the CNS, including the brain stem, cerebellum, basal ganglia, thalamus, hypothalamus, hippocampus, and amygdala. It also covers topics like neuron types, neuroglia, CSF circulation, spinal cord levels, lower and higher brain functions, speech pathways, and neurodegenerative diseases. The central topics covered are the structure and functions of the key parts of the CNS and their roles in motor control, sensory processing, memory, emotion and other higher cognitive functions.

1. CENTRAL NERVOUS SYSTEM
Ahmed H. Ahmed
Cell Physiologist
Biology department-College of Science- Salahaddin University
2023-2024
for 2nd year dental students
Nervous system

3. CNS vs. PNS

6. V

7. NEURON TYPES

8. NEUROGLIA & NEURONAL CELLS

9. CSF CIRCULATION

12. PNS

13. GANGLIA

14. CRANIAL NERVES GANGLIA

15. CRANIAL NERVES GANGLIA
LOCATIONS

16. MAJOR LEVELS OF CENTRAL NERVOUS
SYSTEM FUNCTION
• Higher brain or cortical level
• Lower brain or subcortical level
• Spinal cord level

17. SPINAL
CORD
LEVEL

18. SPINAL CORD LEVEL

19. LOWER BRAIN
LEVEL

20. LOWER BRAIN LEVEL

21. CONDITIONAL RESPONSE: PAVLOVIAN CONDITIONING
Pavlovian conditioning refers to the behavioral
and physiological changes brought about by
experiencing a predictive relationship between
a neutral stimulus and a consequent biologically
significant event (Pavlov, 1927).

22. LOWER BRAIN LEVEL

23. SPINAL CORD LEVEL
• Walking movements.
• Reflexes that withdraw portions of the body from
painful objects.
• Reflexes that stiffen the legs to support the legs
against gravity.
• Reflexes that control local blood vessels,
gastrointestinal movements, or urinary excretion.

24. LOWER BRAIN OR SUBCORTICAL LEVEL
• subconscious control of arterial pressure and
respiration is achieved mainly by Medulla and pons .
• Control of Equilibrium is a combined function of the
older portions of the cerebellum and the reticular
substances of the medulla, pons.

25.  Feeding reflexes, such as salivation and licking of
the lips in response to the taste of food, are
controlled by areas in the medulla, pons,
amygdala, and hypothalamus.
 many emotional patterns, such as anger,
excitement, sexual response, reaction to pain,
and reaction to pleasure, can still occur after
destruction of much of the cerebral cortex.

26. CENTRAL NERVOUS SYSTEM OVERVIEW
 It is estimated that the CNS contains about a
hundred billion (1011) neurons and a
hundred trillion (1014) synapses, all within
the brain and the spinal cord.

27. CENTRAL NERVOUS SYSTEM OVERVIEW
90% of the CNS is composed of Glial cells (neuroglia):
1. Oligodendrocytes
2. Microglia
3. Ependymal cells
4. Astrocytes
They are not merely supportive cells.

28. NEUROGLIA
Astrocytes:
▪ Are most diverse of the glial cells.
▪ Function in development of neuronal connections.
▪ Guide developing neurons to their correct destinations and regulate development and
maintenance of synapses.
▪ Some astrocytes are wrapped around synapses, seemingly, they modulate synaptic
activities.
▪ astrocytes remove neurotransmitters, such as glutamate and biogenic amines
from the synaptic cleft. Because high levels of glutamate are toxic.
▪ Astrocytes release neurotransmitters that communicate to neurons and
affecting the synaptic communications between two neurons.
▪ Astrocytes maintain normal electrolyte compositions of the extracellular fluids,
the necessary to maintain normal neuronal excitability.
▪ Astrocytes also protect neurons from oxidative stress and help remove cellular
debris.
▪ Astrocytes contribute to blood-brain barrier (BBB)

29. GLIAL CELLS IN NEURODEGENERATIVE
DISEASE
Glial cells
contribute to neurodegenerative diseases such
as; multiple scleroses, Alzheimer’s disease,
and Parkinson’s disease.

30. GLIAL CELLS IN NEURODEGENERATIVE DISEASE
 Multiple sclerosis: is an autoimmune disease (in which the immune
system attacks a part of the body ), that attacks oligodendrocytes.
 The loss of myelin and some axons in the CNS slows down or stops
communications along certain neural pathways.
 Symptoms include blurred vision, muscle weakness, and difficulty
maintaining balance.

31. GLIAL CELLS IN NEURODEGENERATIVE DISEASE
 Alzheimer’s disease; is caused by the loss of cholinergic neurons in
certain brain areas and replacement of the lost neurons with scar tissue
called plaques.
 During the degeneration of cholinergic neurons, astrocytes and
microglia become overly active that release inflammatory chemicals
that enhance further degeneration of cholinergic neurons.

32. GLIAL CELLS IN NEURODEGENERATIVE DISEASE
 Early signs of Alzheimer’s disease include loss
of memory and confusion.
 Later signs include motor dysfunction, loss of
communication skills, and decrease in cognitive
functions.

36. BRAIN PLACES WITHOUT BBB

37. PHYSICAL SUPPORT OF THE CNS
 Bony skull (cranium), Vertebral column; protects CNS
against outside hazard
 Meninges protect CNS against inside hazard; such
as crashing into hard inner surface of the skull or
vertebral parts during, for example, a sudden stop
in a car moving at freeway speeds.
 Cerebrospinal fluid (CSF); bathes the CNS and
provides a cushion background.

38. HOW BRAIN CELLS STORE INFORMATION

39. NERVE NETWORKS INTEGRITY

41. Floating brain

42. HIGHER BRAIN
 Extremely large memory storehouse.
 The cortex never functions alone but always in association
lower centers of the nervous system.
 Lower brain functions, without cerebral cortex, are often
imprecise.
 Essential for most of our thought processes.
 Lower brain centers initiate wakefulness in the cerebral cortex,
thus opening its bank of memories to the thinking machinery of
the brain.

45. CEREBRAL CORTEX
1. Sensory perception
2.Voluntary control of movement
3. Language
4. Personality traits
5. Sophisticated mental events, such as thinking, memory, decision
making, creativity, and self-consciousness

46. BASAL NUCLEI
1. Inhibition of muscle tone
2. Coordination of slow, sustained movements
3. Suppression of useless patterns of movement

47. THE BASAL NUCLEI PLAY AN IMPORTANT INHIBITORY
ROLE IN MOTOR CONTROL
The basal nuclei play a complex role in controlling
movement. In particular, they are important in
(1) inhibiting muscle tone throughout the body (proper
muscle tone is normally maintained by a balance of
excitatory and inhibitory inputs to the
neurons that innervate skeletal muscles),
(2) selecting and maintaining purposeful motor activity
while suppressing useless or unwanted patterns of
movement, and
(3) helping monitor and coordinate slow, sustained
contractions, especially those related to posture and
support

48. The importance of the basal nuclei in motor control
is evident in Parkinson’s disease (PD). This
condition is associated with a gradual
destruction of neurons that release the
neurotransmitter dopamine in the basal nuclei.
Because the basal nuclei lack enough dopamine to
exert their normal roles, three types of motor
disturbances characterize
PD:
(1) increased muscle tone, or rigidity;
(2) involuntary, useless, or unwanted movements,
such as resting tremors (for example, hands
rhythmically shaking, making it difficult or
impossible to hold a cup of coffee); and
(3) slowness in initiating and carrying out different
motor behaviors

49. THALAMUS
1. Relay station for all synaptic input
2. Crude awareness of sensation
3. Some degree of consciousness
4. Role in motor control

50. HYPOTHALAMUS
1. Regulation of many homeostatic
functions, such as temperature
control, thirst, urine output, and
food intake
2. Important link between nervous
and endocrine systems
3. Extensive involvement with
emotion and basic behavioral
patterns
4. Role in sleep–wake cycle

51. CEREBELLUM
1. Maintenance of balance
2. Enhancement of muscle tone
3. Coordination and planning of
skilled voluntary muscle
activity

52. BRAIN STEM
1. Origin of majority of
peripheral cranial
nerves
2. Cardiovascular,
respiratory, and
digestive control centers
3. Regulation of muscle
reflexes involved with
equilibrium and posture
4. Reception and
integration of all
synaptic input from
spinal cord; arousal and
activation of cerebral
cortex
5. Role in sleep–wake
cycle

55. ASYMMETRIC VS. SYMMETRIC BRAIN

57. AMYGDALAE
The amygdalae ,Latin, from Greek ἀμυγδαλή, amygdalē, 'almond', 'tonsil',
are almond-shaped groups of nuclei located deep and medially within
the temporal lobes of the brain in complex vertebrates, including
humans. Shown in research to perform a primary role in the processing
of memory and emotional reactions, the amygdalae are considered
part of the limbic system.

58. HIPPOCAMPUS
The hippocampus (named after its resemblance to the seahorse, from
the Greek hippos meaning "horse" and kampos meaning "sea
monster") is a major component of the brains of humans and other
vertebrates. It belongs to the limbic system and plays important roles
in the consolidation of information from short-term memory to long-
term memory and spatial navigation. Humans and other mammals
have two hippocampi, one in each side of the brain.

59. EMOTION, BEHAVIOR, AND MOTIVATION
The limbic system is not a separate structure but a ring of
forebrain structures that surround the brain stem and are
interconnected by intricate neuron pathways. It includes portions
of each of the following: the lobes of the cerebral cortex
(especially the limbic association cortex), the basal nuclei, the
thalamus, and the hypothalamus. This complex interacting
network is associated with emotions, basic survival and
sociosexual behavioral patterns, motivation, and learning.

60. WERNICKE’S AREA
 Wernicke’s area is highly developed in the dominant side of the
brain – the left side in almost all right-handed people.
 Wernicke’s area plays the greater role for higher
comprehension levels of the brain that we call “intelligence”.
This area was first
described in 1874 by
German
neurologist Carl
Wernicke

61.  Severe damage in Wernicke’s area causes
inability to arrange words into coherent
thoughts, that means reading words without
knowing the thought they conveyed.
 Activation of Wernicke’s area can call forth
complicated memory patterns else where.

62. BROCA’S AREA
 Broca’s area initiates and
executes plans and motor
patterns for expressing
individual words or even
short phrases.
 Broca’s area works in close
association with the
Wernicke’s language
comprehension center.
Paul Broca was born on 28 June
1824 in Sainte-Foy-la-
Grande, Bordeaux, France

63. SPEECH PATHWAYS

64. CORPUS CALLOSUM
Manly, makes information stored in the cortex of one hemisphere available
to corresponding cortical areas of the opposite hemisphere .
Corpus callosum, a thick band consisting of an estimated 300 million
neuronal axons that connect the two hemispheres .The corpus callosum is
the body’s “information superhighway.”The two hemispheres
communicate and cooperate with each other by means of constant
information exchange through this neural connection

65. FACIAL RECOGNITION AREA
• Prosopagnosia is inability to
recognize faces.
• This occurs in people who have
extensive damage on the medial
undersides of both occipital lobes
and along the medioventral
surfaces of the temporal lobes.
• But why so much of the cerebral
cortex should be reserved for the
simple task as face recognition?

66. ANGULAR GYRUS
INTERPRETATION OF WRITTEN INFORMATION
 Located between Wernicke’s area and visual area of the occipital
lobe
 Damage to this area causes difficulty in interpreting words meanings a
state called dyslexia or “ word blindness”

67. THE DOMINANT HEMISPHERE
• The cerebral hemisphere that is more involved than the other
in governing certain body functions, such as controlling the
arm and leg used preferentially in skilled movements.

68. CEREBRAL HEMISPHERE

70. COMA
 Coma Is defined as unconsciousness from which the
person cannot be aroused.

71. DEPRESSION
Depression is among the psychiatric disorders
associated with defects in limbic system
neurotransmitters. (As a distinction, psychiatric
disorders involve abnormal
activity in specific neurotransmitter pathways in the
absence of detectable brain lesions, whereas
neurological disorders are associated with specific
lesions of the brain and may
or may not involve abnormalities in
neurotransmission

72. THE LAZY BRAIN

73. THE LAZY BRAIN
• A lazy brain is a shrinking brain
• Those who don't engage in
complex mental activity over
their lifetime have twice the
shrinkage in a key part of the
brain in old age.

75. NEXT LESSON
Neuronal communication