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
8. Functional system
• Functional association some structures
activity of which aimed to regulation some
homeostatic parameters
9.
10.
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
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).
15.
16. NS
•Central nervous system (CNS) - brain and spinal
cord
•Peripheral nervous system (PNS) – cranial nerves
(I-XII), spinal nerves, ganglia, enteric plexuses
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)
21.
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
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).
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
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)
37.
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
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)
47.
48. Classification of reflexes (based
on localization of chains of reflex
arcs)
• Exteroceptive
• Interoceptive (visceral)
• Proprioceptive
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.
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).
62.
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
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
76.
77.
78.
79. Functions of the Spinal cord
reflectory (motor, autonomous)
conductive
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
87.
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
89.
90.
91. Receptors
• Muscle spindle reacts to changes of a
muscle length
• Golgi Tendon Organ – to changes of tension
92.
93. Control of Gamma Efferent
Discharge (gamma-loop)
• Length of muscle spindles regulates a
length of this muscle
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
103. Convergence
• The motor neurons in the spinal cord
constitute the common final path – the root,
by which all central activity influences
motor neurons
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
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)
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)
133.
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
136.
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
•
141.
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
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
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)
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
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)
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
171. Basal ganglia
• caudate nucleus
• Putamen
• Globus pallidus
• But
• Functiomally subthalamic nuclei and s.nigra
belong on basal ganglia
172.
173.
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