lecture 1 Flashcards
is the most complex system in our
body, which is composed of neurons or nerve cells with their processes, neuroglia cells, and blood vessels
Nervous System
Functions of the nervous system
regulate, initiate, process
Ability of the nervous system
Receive Conduct Process Store Release
It forms a slipper-shaped plate
neural plate
nervous system develops from
ectoderm
lateral edges soon become elevated to form the
neural folds
caudal portion of the neural tube becomes the
Spinal Cord.
wall of the neural tube consist of
neuroepithelial cells
give rise to the primitive nerve cells,
Neuroblast
neuroblast cells accumulate around the
neuroepithelial layer and form the so-called
Mantle layer
The lateral layer of the spinal cord is known as the
Marginal layer
which gives this layer the significant white color and therefor this part is called the
white matter
thin wall region that overlies the notochord.
Floor plate
both floor plate and notochord produce
protein Sonic hedgehog (Shh)
thick wall region lying either side of the floor plate lying either side of the floor plate
Basal plate
develop here and extend axons out of the spinal cord to innervate developing skeletal muscle
ventral horn motor neurons
thick wall region lying either side of the roof plate
Alar plate
develop there and receive axons from the sensory
structures outside the spinal cord.
sensory dorsal horn neurons
thin wall region that underlies the dorsal ectoderm epithelium
Roof plate
Dorsal patterns the spinal cord, the roof plate produces
Bone morphogenetic proteins
neuroepithelium lined fluid-filled space continuous with the brain ventricular system.
Lumen
peripheral nervous system
It connects the central nervous system to the organs or viscera
those that carry impulses from peripheral receptor to the central nervous system
Afferent (sensory, centripetal) fibres
these carry impulses from the peripheral receptor (skin, skeletal musculature and bones) to the central nervous system
Somatic afferent (somatic sensory) fibres
carry impulses from the internal organs to the central nervous system
Visceral afferent (visceral sensory) fibres
those that carry impulses from the C.N.S to the muscles or glands
Efferent (motor, centrifugal) fibres:
carry impulses from the C.N.S to the skeletal muscles
except the pharyngeal arch musculature
Somatic efferent (somatic motor) fibres:
carry impulses from the C.N.S to the smooth muscle of the body, cardiac muscle and glands (including pharyngeal arch muscles)
Visceral efferent (visceral motor) fibres
is the part of the nervous system concerned with the innervation of voluntary structure skeletal muscle
somatic (voluntary) nervous system
is the part of the nervous system concerned with the
innervation of the involuntary structure, such as the heart, smooth muscle and glands within the body
autonomic (visceral or vegetative) nervous system
is the primitive organization, is the part of the nervous system that has direct afferent and efferent relation with the rest of the organism
Segmentary nervous system
is a new organization, as a result of develop of the encephalon, and the senses organs
Suprasegmentary nervous system:
is the part of the C.N.S that has
direct afferent and efferent relation with the segmentary nervous system. It is formed by
cerebellum and cerebrum.
Types of cells
The neuron
The neuroglia
is the structural and functional unit of the
nervous system, are excitable cells that are specialized for the reception of stimuli and the conduction of the nerve impulse
Neuron
consists of a single large rounded euchromatic and usually centrally located nucleus surrounded by
cytoplasm.
Cell body or perikaryon
cytoplasm contains all the usually cellular organelles
but abundant
rough endoplasmic reticulum and free ribosomes
under the light microscope appear as basophilic granular areas called
Nissl bodies
At the beginning of an axon and the axon itself
there is no Nissl body or substance
Axon Hillock
are usually short and divide like branches of the tree, they have a similar structure to the cell body except that they contain no or few Golgi apparatus
Dendrites
is a cylindrical process that varies in length and diameter according to the type of neuron
Axon
in myelinated fibers the portion of the axon between the axon hillock and the point at which myelination begin is thinner and it is called
Initial segment
Types of nerve cells
- Apolar.
- Unipolar.
- Bipolar.
- Pseudounipolar.
- Multipolar nerve cell.
have no processes e.g. neuroblasts, taste buds, cell in
the inner ear
Apolar
they contain only one axon but no dendrites, e.g.
neuroblast, rod and cons of the retina and olfactory cell.
Unipolar:
they contain one axon and one dendrite, e.g. second
neurons in the retina, ganglion cells VIII cranial nerve
Bipolar
contains only one process that after a short
distance from the cell body divides in to two in the form of “T”, e.g. sensory neuron of spinal ganglion
Pseudounipolar
they contain an axon and numerous dendrites. Tow types of multipolar nerve cell can be recognized
Multipolar nerve cell
the area that receives the information to be propagated.
Input component
the trigger or spike initiation zone is the area of the neuron where the all or none action potential is generated
Trigger component
the area responsible for propagating the action potential
Conductive component
the area responsible for the release of neurotransmitters
Output component
No excitable cell, forms the major component of nervous tissue. It serves as supporting, insulating and nourishing the neuron
Neuroglia
Type of neuroglia
Oligodendrocyte Astrocytes Ependymal cells Microglia Neurolemma or Schwann cells
Mononuclear phagocytes derived from macrophages
Microglia
Produce myelin in the central nervous system.
Oligodendrocytes
Produce myelin in the peripheral nervous systemenvelop 1 internode and they produce and support the sheath
Schwann Cells
Line the ventricles and choroid plexus
• Ventricles: cavities in the CNS filled with CerebroSpinal Fluid
• Choroid plexus: a collection of vessels within the ventricles
that secrete CSF
Ependyma/Choroidal Cells
are found mainly in the white matter, has small cell bodies, their processes are long, slender, smooth and not much branches
Fibrous astrocytes:
are found mainly in the gray matter, has cell bodies, their processes are shorter, thicker, and more branched
Protoplasmic astrocyte
Fibrous and protoplasmic types.
• Influence embryonic growth or retraction of neurites.
• Regulate chemical contents in the extracellular space.
• Restrict the spread of neurotransmitters
• Regulate the concentration of potassium
• Possess neurotransmitter receptors.
• Extend end feet on CNS neurons to form glial limiting membranes which regulate nutrient passage
Astrocytes-star-shaped cell
Consist mainly of nerve cell bodies (corpus neuronal), with their dendrites and synaptic contacts.
Gray matter or substance
is composed of myelinated nerve fibers, glial cells and blood vessels (it has a white color due to the presence of lipid material in the myelin sheaths)
White matter or substance
Each myelinated neuron is covered by a connective
tissue layer called
endoneurium
Groups of nerve fibers form fascicles which are
covered by
perineurium
Fascicles bound together form a nerve which is
covered by
epineurium
The reflexes are mediated by chains of neurons called
Reflex Arch
defined as rapid, automatic motor responses to stimuli
reflexes
this is the site where the stimulus acts and is transformed into nerve impulse
receptor
this transmits the afferent impulses to the C.N.S
sensory neuron
lies in the C.N.S can be a single synapse between the sensory and motor neurons or multiple synapses in more complex reflex
integration center
This conducts efferent impulses from the integration center to an effector.
motor neuron
this is the muscle or gland cell that responds to the efferent impulses by contracting or secreting
effector
