13-Nervous Flashcards
The most complex system
NERVOUS SYSTEM
Components of the Nervous System
network of nerve cells (neurons)
supporting glial cells
nerve tissue
is distributed throughout the body as an integrated communications network
Nerve tissue
Structural Divisions of the NS
Central nervous system (CNS)
Peripheral nervous system (PNS)
overall “command center,” processing and integrating information
Central nervous system (CNS)
Central nervous system (CNS) components
brain
spinal cord
division of the nervous system in charge of relaying messages to and from the command center
Peripheral nervous system (PNS)
Peripheral nervous system (PNS) components
cranial, spinal, and peripheral nerves
ganglia
conduct impulses to and from the CNS (motor and sensory nerves respectively)
cranial, spinal, and peripheral nerves
which are small groups of nerve cells outside the CNS
ganglia
Functional Divisions of the NS
Sensory Nervous System
Motor Nervous System
Sensory Nervous System components
Some CNS and PNS components
Somatic sensory
Visceral sensory
FUNCTIONAL DIVISION - Includes all axons that transmit impulses from a peripheral structure to the CNS
Some CNS and PNS components
FUNCTIONAL DIVISION - Transmits input from skin, fascia, joints, and skeletal muscles
Somatic sensory
FUNCTIONAL DIVISION - Transmits input from stomach and intestines (viscera)
Visceral sensory
Motor Nervous System components
Motor Nervous System
Somatic motor (somatic nervous system)
Autonomic motor (autonomic nervous system)
FUNCTIONAL DIVISION - Includes all axons that transmit nerve impulses from the CNS to a muscle or gland
Some CNS and PNS components
FUNCTIONAL DIVISION - Voluntary control of skeletal muscle
Somatic motor (somatic nervous system)
FUNCTIONAL DIVISION - Involuntary control of smooth muscle, cardiac muscle, and glands
Autonomic motor (autonomic nervous system)
ionic gradient that exists between the inner and outer surfaces of their membranes
Altered by neurons in respo nse to stimuli
Electrical potential
cells that can rapidly change this potential in response to stimuli (eg, neurons, muscle cells, some gland cells)
Excitable or irritable cells
is capable of traveling long distances along neuronal processes, transmitting such signals to other neurons, muscles, and glands
action potential, the depolarization wave, or the nerve impulse
steps of Neurulation in the Embryo
- Neural folds and neural groove form from the neural plate
- Neural folds elevate and approach each other
3.Neural crest cells loosen and become mesenchymal
- Neural folds merge creates neural tube, neural crest lies atop newly made tube
functional unit of the nervous system
NEURONS
NEURONS consist of three parts :
Cell body (perikaryon)
Dendrites
Axon
synthetic or trophic center for the entire nerve cell and is receptive to stimuli
Cell body (perikaryon)
many elongated processes specialized to receive stimuli from the environment, sensory epithelial cells, or other neurons
Dendrites
a single process specialized in generating and conducting nerve impulses to other cells (nerve, muscle, and gland cells)
Axon
distal portion of the axon is usually _________ as the terminal arborization
branched
part of the axon that interact with other neurons or nonnerve cells at structures called synapses
end bulbs (boutons)
CLASSIFICATION OF NEURONS according to the number of processes extending from the cell body:
Multipolar neurons
Bipolar neurons
Unipolar or pseudounipolar neurons
CLASSIFICATION OF NEURONS according to the number of processes extending from the cell body:
one axon and; two or many dendrites
**Most neurons are ________
Multipolar neurons
CLASSIFICATION OF NEURONS according to the number of processes extending from the cell body:
one dendrite
one axon
Bipolar neurons
CLASSIFICATION OF NEURONS according to the number of processes extending from the cell body:
have a single process that bifurcates close to the perikaryon, with the longer branch extending to a peripheral ending and the other toward the CNS
Unipolar or pseudounipolar neurons
Bipolar neurons are found in
retina
olfactory mucosa
and the (inner ear) cochlear and vestibular ganglia
where they serve the senses of sight, smell and balance respectively.
Unipolar or pseudounipolar neurons are found in the
spinal ganglia (the sensory ganglia found with the spinal nerves)
and in most cranial ganglia.
CLASSIFICATION OF NERVES according to function
Motor (efferent) neurons
Sensory (afferent) neurons
CLASSIFICATION OF NERVES according to function
control effector organs such as muscle fibers and exocrine and endocrine glands
Motor (efferent) neurons
CLASSIFICATION OF NERVES according to function
involved in the reception of sensory stimuli from the environment and from within the body
Sensory (afferent) neurons
contains the nucleus and surrounding cytoplasm, exclusive of the cell processes
it is primarily a trophic center
CELL BODY (PERIKARYON)
nucleus of nerve cells are
spherical
unusually large
euchromatic (pale-staining)
prominent nucleolus
most neurons are single nucleated but sometimes bi nucleated neurons are sometime found in
sympathetic and sensory ganglia
Chromatin of neurons are _________, reflecting the intense synthetic activity of these cells
finely dispersed
Cell bodies of neurons contain a (describe the organelles)
highly developed rough ER organized into aggregates of parallel cisternae.
chromatophilic substance made of basophilic clumps of RER and free ribosomes which can be seen under LM with appropriate stains
abundant in large nerve cells such as motor neurons
Nissl bodies
Golgi apparatus of the neuron is only found in the
cell body
Mitochondria- found throughout the cell and usually abundant in the
axon terminals
intermediate filaments are abundant both in
perikarya and processes
neurofilaments cross-linked with certain fixatives becoming visible with the light microscope when impreganated with silver salt
Neurofibrils
Neurons also contain microtubules and may also contain pigmented materials like_______ (consists of residual bodies left from lysosomal digestion)
lipofuscin
are usually short and divide like the branches of a tree
often covered with many synapses and are the principal signal reception and processing sites on neurons
Dendrites
sites of synapses with other neurons
found on dendrites surfaces
length and morphology are dependent on actin filaments and are highly plastic
Dendritic spines
are cylindrical process that varies in length and diameter according to the type of neuron.
Axon
All axons originate from a pyramid-shaped region, the ________, arising from the perikaryon
axon hillock
plasma membrane of the axon
Axolemma
cytoplasm of the axon
Axoplasm
Bidirectional Transport of Molecules along the Axon
Anterograde transport
Retrograde transport
movement of organelles and macromolecules synthesized in the cell body along the axon from the perikaryon to the synaptic terminals
Anterograde transport
macromolecules, such as material taken up by endocytosis (including viruses and toxins), are taken from the periphery to the cell body
Retrograde transport
Bidirectional Transport of Molecules along the Axon
both directions utilizes
motor proteins attached to microtubules
a microtubule-activated ATPase, attaches to vesicles and allows them to move along microtubules in axons away from the perikarya
kinesin
is a similar ATPase that allows retrograde transport in axons, toward the cell bodies
dynein
anterograde and retrograde transport both occur fairly rapidly, at rates of
50 to 400 mm/day.