NERVOUS REGULATION OF FUNCTIONS . EXCITATION AND INHIBITION IN CNS

1. Nervous regulation of functions.
Excitation and inhibition in CNS
Lecture 2
BY DEEP PATEL
CRIMEA STATE MEDICAL UNIVERSITY
RUSSIA

2. Questions:
• General principles of function regulation.
• Functional systems. Positive and negative
feedback.
• Nervous regulation of functions. Neuron as
the structural and functional unit.
• Nervous centers and their properties.
• Reflex, reflex arch, its structure.
• Principles of reflex coordination

3. Regulation
process of the maintenance of
homeostasis
Homeostasis – maintenance of static
(or constant) conditions in the internal
environment
Internal environment – liquid environment of
human body (blood, lymph, extracellular fluid
etc.)

4. Regulation is realized by control
systems
• There are thousands control systems
• Example: respiratory system together with
nervous system regulates concentration of
carbon dioxide

5. Biological regulation
• Levels:
cellular (local regulation)
organ (local into organ)
system and organism (central)

6. Regulation of body functions
is provided by regulatory systems
• Nervous system
• Hormonal system

7. Central regulation
• Realizes by means:
central nervous system
endocrine system

8. Functional system
• Functional association some structures
activity of which aimed to regulation some
homeostatic parameters

11. Regulatory apparatus (feed-back
mechanism) includes:
• Positive and negative feedback loops.
• Positive: the more parameter the more
functional activity of organ
• Negative: the more parameter the lesser
functional activity of organ

12. Role of feedback
mechanism
• When a homeostatic constant of
internal environment deviates
significantly from normal range,
through feedback mechanism the
deviation is corrected to
maintain homeostasis

13. Importance
• Autoregulation is possible
• negative feedback loop is typical for healthy
human body

14. Nervous regulation of functions
• NS provides the control of functions of
the body: the rapid activities of the body
(muscular contractions, rapidly changing
visceral events and the rates of secretion
of some endocrine glands).

16. NS
•Central nervous system (CNS) - brain and spinal
cord
•Peripheral nervous system (PNS) – cranial nerves
(I-XII), spinal nerves, ganglia, enteric plexuses

18. Functions
• Sensory
• Integrative
• Motor

19. Neuron
• is a basic structural and functional unit of
the nervous system. As well as the NS in
whole a neuron receives information from
the different sensory organs and integrates it
producing body’s response.

20. Structure of neuron
• Has dendrites (reception of information),
cell body (processing and analysis of
information) and trigger zone – axon hillock
(AP initiated – efferent command)

22. Functions of neuron:
• Receptive
• Analysis and synthesis of information
(integrative function)
• Motor function (generation of AP)

23. Classification of neurons:
is based on functions (a), number of
processes (b), neurotransmitters (c),
shape and size.
(a) sensory (afferent), contact
(intraneuron), motor (efferent);
(b)unipolar, bipolar, multipolar;
Cholinergic, adrenergic

26. Neuroglia
• Astrocytes
• Oligodendrocytes
• Microglia
• Ependymal cells (only in CNS)
• Schwann cells and sattelite cells in PNS

28. Functions of neuroglia
• Trophic: provides nutrients to neurons
• Homeostatic (helps to maintain appropriate
chemical environment);
• Supporting function (network around CNS
neurons);
• Protective (from microbe diseases) etc.

29. Nervous center
• Is a association (group) of neurons which
together regulate a definite function
(respiratory center, hemodynamic center
etc).

30. Properties
• Summation of excitation
• Occlusion
• One-way conduction
• Delayed conduction
• Prolongation (post-action)
• Transformation
• Divergence
• Convergence

31. Summation
• Generation of AP in response to
subthreshold impulses when they come to
the center one after another at short interval
along one nerve fiber
• Or
• when they come to the center
simultaneously from different fibers

32. Types of summation
• Temporal (consecutive) summation
• Spatial summation

34. Occlusion
• Decreased reaction response (effect) on
simultaneous stimulation

35. This phenomenon can be explained as two nervous centers
can have some common neurons that belong on both centers

36. One-way conduction
• In CNS the impulses can be conducted only
in one direction (from afferent neuron to
efferent neuron)

38. Delayed conduction
• The impulses pass through the nervous
center more slowly than along nerve
because the chemical processes in the
synapses take some time – synaptic delay

39. Prolongation
• Reflex can continue after end of
stimulation.

40. Transformation
• Change of the rhythm of excitation

41. Divergence (or irradiation)
• Excitation can spread increasingly and
involving more and more neurons

42. Convergence
• Excitation spreads from multiple neurons to
single neuron

43. Neurons circuits (chains)
• Diverging
• Converging
• Reverberating
• Parallel after-discharge etc

44. Neurons circuits

45. Reflectory principle
• Reflex is response of organism on external
stimulation (R.Decart, 17th century)
For CNS: “Reflexes of brain” M.Sechenov
(1869)

46. Links of reflex arc
• Afferent (receptor, afferent fiber, afferent
neuron) – Receptive field : group of
receptors which send sensory information to
one afferent neuron
• Central (contact (inter-) neurons)
• Efferent (efferent neuron, efferent fiber,
effector organ)

48. Classification of reflexes (based
on localization of chains of reflex
arcs)
• Exteroceptive
• Interoceptive (visceral)
• Proprioceptive

49. Central chains
• Spinal
• Bulbar
• Mesencephalic (mid-brain)
• Diencephalic (interbrain)
• Cortical

50. Efferent chain
• Motor (muscles)
• Secretory (glands)

51. Structure of reflex arc
• Monosynaptic
• Bisynaptic
• Polysynaptic
• Reflex time depends on number of synapses
in reflex arc

52. Other classifications
• Physiological: cardiovascular, respiratory,
digestive, excretory, locomotor, stato-
kinetic
• Biological: nutritive, defensive, sexual
• Somatic, autonomic
• Conditioned, unconditioned

53. Principles of coordination

54. Coordination
• Interaction of neurons and neuron processes
(reflexes)

55. Principles of reflex coordination
• Reciprocal innervation
• Common final path
• Dominant

57. Principle of common final path
(by CH.S. Sherrington)

59. Domimant (by Ukhtomsky)
• In definite conditions one nervous center
always is the most active (higher tonus)
than other centers. And even more, this
center inhibits other centers. It is important
because iy permits to focus brain only on
one action, realization of which is the most
important in concrete situation.

60. Excitation end inhibition in CNS.
Central synapses

61. Inhibition
• Is the nervous process, opposite excitation
• It archives by means hyperpolarization on
the postsynaptic membrane (postsynaptic
inhibition) or as result of inhibition of
mediator secretion in the synaptic cleft from
presynaptic membrane (presynaptic
inhibition).

63. Central synapses
• Excitatory neurotransmitters (acetylcholine,
amino acids, biogenic amines, ATP and
other purines, nitric oxide)
• Inhibitory neurotransmitters (glycine,
gamma aminobutyric acid - GABA).
• About 100 chemical substances

64. Bioginic amines:
• Norepinehrine – in the brain a smaller
number of neurons use - awakening from
deep sleep, dreaming and regulating mood;
• Dopamine – emotional responses, addictive
behaviors and pleasurable experiences,
tonus of skeletal muscles (Parkinson
desease, one form of schizophrenia)

65. Biogenic amines:
• Serotonin – sensory perception, temperature
regulation, control of mood, appetite,
induction of sleep

66. ATP and other purines
• Excitatory NT in CNS and PNS act with NE

67. Neuropeptides
• Enkephalins analgetic action stronger than
morphin
• Opioid peptids (endorphyns) – analgesia
(loss of pain sensation, improving of
memory and lesrning, feelings of plesure or
euphoria, sexual drive etc. and depression
and schizophrenia.
• Substance P – pain sensations

68. Nitric oxide
• Has widespread effects throughout the
body.
• Main effects – vasodilatation, m.b.memory
and learning (Viagra).

69. Inhibitory neurotransmitters
• Inhibitory NS cause IPSP by opening Cl
ions. Antianxiety drugs such as diazepam
(Valium) enhance the action of GABA.
• GABA is found only in CNS. In spinal cord
about half of inhibitory synapses use amino
acid glycine and half use CABA

70. Iontropic receptors

71. Metobotropic receptors

72. Serotoninergic synapse

73. AcH transmission

75. Questions
1. Spinal cord in regulation of the motor
function
2. Brain stem. Role of the Reticular
Formation in control of motor function
3. Function of Cerebellum in controlling of
movements
4. The Basal Ganglia and motor control
5. Motor functions of the Cerebral Cortex

79. Functions of the Spinal cord
reflectory (motor, autonomous)
conductive

82. Bell-Magendie law
• Posterior roots contain centripetal, afferent
fibers
• anterior roots contain centrifugal, efferent
fibers

83. Neuronal organization of s.c.
• Dorsal horns: afferent centers
• Lateral horns: vegetative centers
• Ventral horns: motor centers

84. • Sensory
• Integrative
• Motor

85. Sensory f.
• 12 laminas (1-YI – in dorsal horns; 2-3 –
substantia gelatinosa) - reception of
information from mechanoreceptors
(Aβ,Aδ, C), nociceptors (Aδ,C), cold
receptors(Aδ), thermoreceptors ©.

86. Integrative function
• Interneurons are present in all areas of the
cord gray matter
• Renshaw cells –inhibitory cells – transmit
inhibitory signal to the nearby motor neuron

88. Motor function
• 2 types of motor neurons:
• Α-motoneurons regulate the extrafusal
muscle fibers (contraction of muscle)
• γ-motoneurons provide dynamic and static
reactions in response on information from
intrafusal muscle fibers

91. Receptors
• Muscle spindle reacts to changes of a
muscle length
• Golgi Tendon Organ – to changes of tension

93. Control of Gamma Efferent
Discharge (gamma-loop)
• Length of muscle spindles regulates a
length of this muscle

95. Gamma coactivation
(during voluntary movements)

96. Spinal motor reflexes
• Stretch (myotatic, tendon) reflexes regulate
muscular tone and posture – fast stretch of
muscle
• Phasic reflexes - skin reflexes
(exteroceptive reflexes)

97. Myotatic (muscle stretch) reflex
(Fast change of posture)

98. Inverse stretch reflex (active
muscle contraction)
• Receptors – Goldgi tendon organ (unlike the
spindles) are stimulated by both passive and
active contraction of the muscle.
• Stretch stimulates the spindle – Ia fibers -motor
neurons
• It stimulates also Golgi tendon organ, Ib fibers
activate the interneuron to release inhibitory
mediator glycine
• Strong stretch stops discharging

99. Phasic reflexes (withdrawal reflex, skin
reflexes)

100. Clinical reflexes
• flexion-extension reflexes (biceps reflex,
triceps reflex, Achilles reflex)
• Knee-jerk reflex
• Abdominal reflexes

102. Mechanisms of coordination
• Convergence
• Divergence
• Reciprocal inhibition
• Inverse (recurrent) inhibition

103. Convergence
• The motor neurons in the spinal cord
constitute the common final path – the root,
by which all central activity influences
motor neurons

104. Convergence

105. Divergence
• Spreading of impulses from 1 neuron to
some neurons

106. Divergence

107. Reciprocal inhibition
• Collateral branches of type Ia axons inhibit
the motor neurons of antagonist muscles

108. Reciprocal inhibition

109. Recurrent inhibition
• Stimulation of one neuron causes the
inhibition of surrounding motor neurons

110. Autonomous reflexes
• Vessels
• Smooth muscles of visceral organs (act of
urination, defecation, erection etc)

111. Ascending tracts
spinocerebellar
spinotalalamic
fasciculus gracilus and fasciclus cuneatus
Descending tracts
corticospinal
rubber-spinal
tecto-spinal
reticular-spinal
vestibulo-spinal

112. • Proprioceptors of the muscles, tendons –
spinal ganglia - medulla oblongata –
thalamus – cerebral cortex
Fasciculus gracilus and fasciclus
cuneatus (Goll’s and Burdach’s)

113. spinotalalamic
• Pain and temperature receptors – lateral
spinotalamic tract – thalamus- cortex
• Tactile receptors of the skin – ventral
spinothalamus tract – cerebral cortex

114. spinocerebellar
(Gowers’ and Flechsig’s)
• Proprioceptors - cerebellum

116. Descending tracts
• corticospinal
rubber-spinal
tecto-spinal
reticular-spinal
vestibulo-spinal

117. Spinal shock
• Transsection of s.c. in the upper neck causes
depression all reflexes.
• After a few hours to a few weeks (months)
the reflexes recover

119. Brain stem
• Medulla
• Pons
• mesenchephallon

120. Hind brain and cerebellum

121. Diencephalons
• Thalamus
• Hypothalamus

124. Functions
• 1. sensory and motor functions of face and
head regions which are provided by
cranial nerves (afferent and efferent as in
spinal cord)
• 2. many special control functions by means
own nuclei:

125. Nuclei which provide
• Respiration
• The cardio-vascular system
• The gastrointestinal system
• Many stereotyped movements of the body
• Control of equilibrium
• Control of eye movement

126. Medulla oblongata
• XII –n.hypoglossus (motor)
• XI – n.accessorius (motor)
• X –n.vagus (sensory and motor)
• IX – n.glossopharingeus (sensory and
motor)
• YIII – n.vestibulo-cohlearis (sensory and
motor)

127. Pons
• YII – n.facialis (sensory and motor)
• YI – n.olfactoris (sensory and motor)
• Y – n.trigeminus (sensory and motor)

128. Mesencephalon
• III – n.oculomotoris
• IY – n. trochlearis

130. Cranial nerves

131. Sensory and motor nuclei

132. Vital and other centers in medulla
and pons
• Inspiratory, expiratory, pneumotaxic centres - (vital
centers of the respiratory system and centers of the
coughing and sneezing)
• Hemodynamic center – vital center of the
cardiovascular system (pressor and depressor)
• Centers of the chewing, sucking, swallowing, vomiting
– the digestive system
• Vestibular n. (Deiter’s n. in pons)
• Reticular n.
• Olivar n.
• Fasciculus gracilus and fasciclus cuneatus (Goll’s and
Burdach’s tracts)

134. Functions of hind brain
• Sensory (from receptors along aff.cranial nerves)
• Vegetative (autonomous regulation of the vital
centers)
• Motor function: a)participation in the regulation of
the static and stato-kinetic reflexes together with
midbrain; b) reticular (regulation of the spinal
centers tone) and vestibular (regulation of the
tonic reflexes of the position of the body) nuclei
• Conductive function (Goll’s and Burdach’s tracts
etc.)

135. Nuclei in the Midbrain
• N. lamina (tecti) quadrigemina: superior
(anterior)quadrigeminal bodies– primary optic
centers; inferior – acustic center
• S.nigra – regulation of tone, delicate
movements of fingers requiring great accuracy,
coordination of the complex acts of deglutition
and mastication
• N.ruber – regulation of muscular tone

137. Motor functions of the brain
stem
• the static reflexes : regulation of the
posture and equilibrium
• statokynetic reflexes: regulation of the
pose and equilibrium during movement

138. Static reflexes
• Support of the body against gravity are
provided by reticular and vestibular nuclei.
• Reticular nuclei include: the pontine reticular
n. and medullary reticular n. (reciprocal
relations)
• Descending Reticular spinal tract (medial and
lateral) - regulation of the tone of the axial
muscles (vertebral column and the extensor
muscles of the limbs), which support the body
against gravity

139. Vestibular n.
• Afferent information - from vestibular
apparatus
• vestibular nuclei (Deiter’s n. activates the
tone of extensor muscles)
• Efferent signals maintain equilibrium by
means descending vestibular-spinalis tract

140. Decerabrate rigidity
• Exclusion influence of the red n. on hind
brain (Deiter’s n. ) causes to increasing of
extensor muscles tone
•

142. Static reflexes
- of position – regulation of pose (redistribution of
muscle tone) in response on:
impulsation from neck proprioceptors – neck
tonic reflexes
from vestibular apparatus –
labyrinth tonic reflexes
- of righting – recover of pose after its change

144. Stato-kinetic reflexes
• Arise during change of a movement
velocity

145. labyrinth
reflexes
•Lift reflexes

146. Nystagmus of the eye
(during stato-kynetic reflexes)
• During rotation the eyes turns slowly as far
as possible to the side opposite to the
direction of rotation, then is reversed by a
quick motion to a normal position in
relation to the trunk

147. Postural reflexes
• Maintain equilibrium and posture in
response on sudden changes in the
orientation of an animal in space

148. Orientation reflexes
• turning of the head and body towards a new or
strong or sudden sound or light stimulation

149. Reticular formation
• Diffuse aggregations of cells of various types and
sizes, which are thickly interlaced by numerous
fibers passing in different directions
• Function: regulation the excitability and tone of all
divisions of the CNS (activation influence on the
cerebral cortex - Megoun, Morutzi; activation and
inhibition of the spinal centers (Sechenov)

150. Ascending activating influence of
the reticular formation

151. Thalamus

152. Functions
• Collect all sensory information: specific,
non-specific, associative, relay nuclei

153. Controlling stereotyped
movements
• Flexion, extension, rotation, turning
movements of the entire body by nuclei of
mesencephalic and lower diencephalic
region

154. Connections of the thalamus

155. Specific n.
• Connect with specific sensory areas of
neocortex.
• It provides a fast analysis of sensory
information and fast reaction on it

156. Nonspecific n.
• Connect with associative areas of
neocortex.
• It provides slow but detailed analysis of the
information

157. Associative n.
• Provide interaction of the thalamic neurons
• It is reputed that analysis of the sensory
information on thalamic level causes
formation unconscious sensations

158. The Cerebellum

161. Nucleus emboliformis
Nucleus dentatus
Nucleus globosus
Nucleus fastigii

163. 3 layers of cortex

165. Functions of Cerebellum
Posture - paleocerebellum (aff.pathways from
vestibular analizer)
Control of rapid muscular activities, such as
running, typing, sequence the motor activities,
monitors and makes corrective adjustments in the
motor activities elicited by other parts of the brain
-acheocerebellum (from spinal cord)
Fast movements in accordance with “command”
from brain cortex and basal ganglia (from
neocortex)

166. Inretaction of cerebellum with
cortex

167. Symptoms
Disequilibria – lack of balance
Asthenia – quick tiredness
Ataxia – disturbance of walking
Atonia – lack of muscular tonus
Adiadohokines – inability to perform some
simultaneous movement
Dismetria – wrong of measurement

169. Hypothalamus

171. Basal ganglia
• caudate nucleus
• Putamen
• Globus pallidus
• But
• Functiomally subthalamic nuclei and s.nigra
belong on basal ganglia

174. Functions
• Aff.from sensory and associative areas of
cortex,s.nigra - striatum-pallidum, s.nigra –
thalamus – motor zone, nuclei of brain
stem/
• Through pyramidal tract (cortico-spinalis)
the basal ganglia tonic influence on alfa-
motoneurons of flexor muscles
• Through the reticular formation - influence
on tone flexor and extensor muscles

175. Functions
• Together with s.nigra – inhibition of the
spinal motor reflexes (alfa- and gama-
motoneurons
• Disturbance a connection between s.nigra
and basal ganglia (lack of DOFA) –
Parkinson’s des.
• Together with cerebellum – memorization
of motor program

176. Clinical syndromes resulting
from damage to the basal ganglia
Caudate nucleus
and putamen
Hyperkinesia
Hypotonus
Globus pallidus
Hypokinesia
Hypertonus

177. Motor zone of neocortex
• Associative zones– plan of the future
movement
• Precentral gyrus – program of the future
movement

178. The primary somatic area is
located in the postcentral gyrus.

180. Both (somatic and motor) areas have the detail topography
(homunculus), a hand and a face take the most place on
surface of these areas.

181. Different parts of body are represented
in different groups of neurons