Download Visceral Nervous System

NERVOUS SYSTEM
Anatomical and functional interacting structures able to
recognize external and internal signals and able to elycite a
proper response.
Somatic Nervous System (S.N.S.): it collects sensory
signals from the perifery of the body and from the
locomotor system and it controls the muscolar system on a
conscious or not conscious basis. Furthermore it perform
complex functions like memory, creativity, judgement.
Visceral Nervous System (V.N.S.): it collects sensory
signals from the internal organs (digestive, circulatory,
respiratory, urinary…) but also from periferal signals
(sigth, odor, tact…) and it controls visceral organ functions
on a not conscious basis. It is able to adapt the organism to
changing conditions and it interacts with the S.N.S
ANATOMICAL PARTITION
Peripheral nervous system (P.N.S.) transports
afferent signals (sensory), and efferent signals
(motor) to and from the…
CentraL Nervous System (C.N.S.) where a) direct
connections between sensory and motor nerves allow
reflexes, or b) interpretation of the signals occurs
and proper conscious responses are organyzed.
NERVOUS SYSTEM:
C.N.S. in blue;
P.N.S. in yellow
NERVOUS SYSTEM
P.N.S. is represented by NERVES containing:
-SENSORY AFFERENT FIBERS connected with
RECEPTORS.
Their cell body is in SPINAL and
ENCEPHALIC GANGLIA;
-MOTOR EFFERENT FIBERS ending into TARGET
CELLS. Their cell body is in the SPINAL CORD or in the
BRAIN STEM.
C.N.S. is made up by
-SPINAL CORD in the vertebral canal;
-BRAIN STEM, ENCEPHALON (Cerebellum and
Telencephalon) and DIENCEPHALON inside the skull,
Spine and brain stem are continuos one another at the
level of the foramen magnum of the occipital bone.
Posterior view
of the C.N.S.
and of the origins
of the P.N.S.;
Spinal ganglia and
Spinal Nerves
CLASSIFICATION OF SENSORY RECEPTORS
BASED ON THE TYPE OF STIMULUS:
Mechanoceptors (pressure, earing, stretch)
Chemoceptors (taste, smell, dolor, salt concentration)
Photoceptors (sight)
Thermoceptors (cold, heat)
DISTRIBUTION:
Esteroceptors: positioned at the surface of the
body, stimulated by external signals.
Interoceptors: in the digestive, urinary, circulatory systems
Propioceptors: in the locomotor and vestibular systems
STRUCTURE: Free terminals (temperature and dolor)
Associated to epithelia (Merkel cells, hair follicles)
Encapsulated (Meissner, Pacini, Ruffini tendon organs)
Neuromuscolar spindles (scheletal muscle)
Modified neurons (sight and smell).
SENSORY RECEPTORS
THE QUANTITATIVE AND QUALITATIVE
DISTRIBUTION OF THE SENSORY
RECEPTORS VARIES IN DIFFERENT TISSUES
AND ORGANS, THUS CONFERRING
REGIONAL SPECIALIZATION.
CENTRAL NERVOUS SYSTEM
AXIAL STRUCTURES:
SPINAL CORD
BRAIN STEM
Medulla Oblongata
Pons
Midbrain
SOVRAXIAL STRUCTURES
CEREBELLUM
DIENCEPHALON
TELECEPHALON (CEREBRAL EMISPHERES)
CENTRAL NERVOUS SYSTEM
BASIC TERMS AND STRUCTURE OF THE
NERVOUS SYSTEM
GREY METTER: concentration of cell bodies.
WHITE METTER: concentration of mielinated fibers.
NUCLEUS: a group of neurons in the C.N.S performing a
coordinated function.
GANGLION: a group of neurons OUTSIDE THE C.N.S.
1. Sensory (associated to spinal and cranial nerves)
2. Motor (part of the autonomic nervous system).
GREY MATTER, WHITE MATTER, BASAL GANGLIA
GREY MATTER IN SPINAL CORD AND BRAIN STEM
BASIC TERMS AND STRUCTURE OF THE
NERVOUS SYSTEM
TRACT, FASCICULUS: a group of parallel fibers, that
appears as white matter at macroscopic observation,
transporting a given information to a common destination:
Motor signals, represented by fasciculi descending from
higher centers (cerebrum, cerebellum, brain stem) to
motor neurones, and
Sensory signals, originating from receptors, represented
by fasciculi ascending from the spine or brain stem to
higher centers.
Anatomical basis of
the formation of a
sensory fasciculus
(also the basis for
the somatotopic
organization of
the white metter)
Fibers from
cervical posterior
roots
Fibers from
lumbar posterior
roots
NEURONAL CHAINS
-The simplest chain is the REFLEX ARCH composed
of a SENSORY NEURON (PROTONEURON) and a
MOTOR NEURON. the reflex arch does not involve
sovraxial centers. It is RESTRICTED to spinal cord
and brain stem.
-POLYNEURONIC CHAINS are needed to involve
SOVRAXIAL CENTERS (diencephalon, cerebellum,
telencephalon) in the complex elaboration for the
signal interpretation and response.
BINEURONIC CHAIN
POLYNEURONIC CHAIN
MENINGES
DURA MATER: external fibrous layer
ARACHNOID: intermediate layer
SUBARACHNOIDAL SPACE → LIQUOR
PIA MATER: internal layer
MENINGEAL LAYERS
Overview of the Central nervous system
The brain-lateral view
The brain, the cerebellum and brain stem
The brain-basal view
The brain-sagittal section
SPINAL CORD
Spinal cord, nerve roots and the vertebral column
CAUDA EQUINA
Spinal cord-the neuromere
DERMATOMERES
dermatomeres
Development of harm
and leg dermatomeres
GREY MATTER OF THE SPINE
NEURONS IN GREY METTER OF
THE AXIAL C.N.S.
RADICULAR NEURONS: they form the anterior roots.
In the spinal cord the cell body is in the anterior horn
of the grey metter; in the brain stem in motor nuclei.
FASCICULAR NEURONS: they represent the second
neuron of a sensory pathway. In the spinal cord the
cell body is in the posterior horn of the grey metter; il
the brain stem in the sensory nuclei.
INTERNEURONS: they never leave the grey metter
and connect different cells inside the grey metter.
GROUPS OF
NEURONS IN
THE GREY
MATTER OF
THE SPINAL
CORD
ORGANIZATION OF THE WHITE
MATTER OF THE SPINE
Conscious
Sensory signals.
-Three neuronic
-controlateral
Sensory
proprioceptive
Pathways:
Conscious
three-neuronic
controlateral
component
Non conscious
bi-neuronic
homolateral
component:
Not conscious
sensory signals.
-bineuronic
homolateral
Voluntary motor
Signals (pyramidal
system)
-Crossed and
direct,
Bi-neuronic.
Rapresentation
of the homunculus
Not voluntary
motor signals
(Extrapyramidal)
-homolateral
and bi-lateral,
multineuronic.
.
An example of the loss of functions
following a lesion of the spine. An emisection.