Overview of the Nervous System Flashcards
Composed of cells whose function is to receive sensory stimuli, process the stimuli (in the integration center: brain and spinal cord) and transmit them to effector organs (muscular or glandular)
Nervous System
It functions to maintain homeostasis.
Nervous System
Summary of Nervous System function
Sensory input -> Integration in the brain or spinal cord ->
Output to effector organs
2 types of nerve cells
Neuron and neuroglia
Name given to nerve cells and all its processes
Neurons
Function of neurons
reception of stimuli and conduction of nerve impulses
T or F: Neurons do not undergo division and replication.
T
Parts of neuron
Cell body
Neurites/Nerve processes/Nerve fibers
Part of neuron: consists of nucleus and organelles
Cell body (Soma/Perikaryon)
afferent (entry point), shorter, receives stimuli from the environment
Dendrite
2 Neurites
Dendrite and Axon
efferent (exit point), longer, provides stimulation to other nerves or effector organs
Axon
Gap between the myelin sheaths of the axon
Node of Ranvier
Insulating coat made up of phospholipids, speeds up transmission of signals through saltatory transmission
Myelin sheath
Color of neuron:
- Myelinated
- Unmyelinated
- White
2. Gray
The propagation of action potential along myelinated axons (by leaping) from one node of Ranvier to another.
Saltatory transmission
Problem with myelin sheath (de-myelination), longer transmission of impulses
Multiple sclerosis
Space/cleft in between the axon of one neuron to the dendrite of another neuron; Connects one neuron from another
Synapse
Neurons according to function
Motor
Sensory
Interneuron
Neuron:
Transmits impulses from the CNS to effector organs
Motor
Neuron:
Receives input from peripheral structures (skin, muscles, joints, sense organs) and transmit it to the CNS
Sensory
Neuron:
Connects sensory to motor neurons
Interneuron
T or F: 95% of the neurons in CNS are interneurons
F. 90% only
Neurons accrdg to branching of neurites
Unipolar
Bipolar
Multipolar
Neuron:
A single process/neurite arises from the cell body, which branches into 2 axons/dendrites.
Unipolar
Neuron:
2 neurites arise from each end of an elongated cell body (1 dendrite, 1 axon)
Bipolar
Neuron:
Most common type in the CNS; With a number of neurites arising from the cell body (many short dendrites, 1 long axon)
Multipolar
Location of unipolar
Spinal and Cranial Ganglia
Location of bipolar
Sensory cochlear
vestibular ganglia
Retinal bipolar cells
Location of multipolar
Fiber tracts of brain
spinal cord
Peripheral nerves
motor cells of spinal cord
Neurons accrdg to size
Golgi Type I and Type II
Neuron:
Form the long fiber that extends from the cortex of the brain to spinal cord, and peripheral nerves
Golgi Type I
Location of Golgi Type I
Pyramidal cells of cerebral cortex
Purkinje cells of the cerebellar cortex
Motor cells of the spinal cord
Neuron:
Short axons and short dendrites; star shaped due to dendrite spread
Golgi Type II
Location of Golgi Type II
cerebral and cerebellar cortices
Neuron:
Often inhibitory in function; Functions as interneurons, only interconnect (one part of hemisphere to another part of the same hemisphere)
Golgi Type II
Non excitable cells, do not transmit signals; Supporting neurons
Neuroglia
Types of Neuroglia
Astrocytes
Myelin sheath-producing cells
Microglia
Ependymal cells
Neuroglia:
Star-shaped due to dendrite spread; branching processes serve
as the framework for the nerve cells and fibers
Astrocytes
Neuroglia:
Play an important role in the structure of the blood-brain barrier
Astrocytes
Neuroglia:
In the embryo, serve as scaffolding for the migration of immature
neurons
AStrocytes
Neuroglia:
Take up excess K+ (electrolyte balance) from the extracellular
space and stores glycogen within the cytoplasm
Astrocytes
2 types of astrocytes
Fibrous and protoplasmic
Astrocyte:
Provide supporting framework, electrical
insulators, limit spread of neurotransmitters, take up K+ ions
Fibrous astrocyte
Astrocyte:
mainly white matter; Small cell bodies, long slender processes,
smooth, not much branched
Fibrous astrocyte
Astrocyte:
store glycogen, with phagocytic function, take
place of dead neurons, conduit for metabolites or raw
materials, produce trophic substances
Protoplasmic astrocyte
Astrocyte:
mainly gray matter; small cell bodies, short thick processes, more
branched
Protoplasmic astrocyte
2 myelin sheath-producing cells
Oligodendrocytes
Schwann cells
Form several intermodal segments of myelin on
the same or different axon in CNS
Oligodendrocytes
Myelin sheath producing cells in the PNS
Schwann cells
Neuroglia:
Proliferate in disease and are actively phagocytic (eats
toxins, debris, dirt in CNS); In inflammatory and degenerative
lesions of the CNS, they migrate to the site of lesion
; Can be generated from WBC
Microglia
Neuroglia:
Scattered throughout CNS
; Smallest of the neuroglial cells, wavy branches with
spines
Microglia
Neuroglia:
Assist in circulation of the CSF by the movement of the cilia; ensure proper CSF circulation
Ependymal cells
Neuroglia:
Line the ventricles and the central canal of spinal cord
; Single layer of cuboidal/columnar cells with microvilli and cilia
Ependymal cells
3 types of ependyma
Ependymocytes
Tanycytes
Choroidal Epithelial Cells
Location: line the ventricles of the brain and central canal of the spinal cord
Structure: Cuboidal or Columnar in shape with villi and microvilli, gap junctions
Function: Circulsae CSF, absorb CSF
Ependymocytes
Location: line the floor of the third ventricle overlying the
median eminence of hypothalamus
Structure: has long basal processes
Function: transport substances to CSF to hypophysealportal system
Tanycytes
Location: cover the surfaces of choroid plexuses
Structure: sides and bases thrown into folds, tight junctions
Function: produce and secrete CSF
Choroidal epithelial cells
Consists of brain and spinal cord; protected by skull and vertebral column respectively.
CNS
composed of soma (cell body of neurons)
Gray matter
composed of myelinated neurites, processes of soma, white due to presence of lipid material in myelin sheath.
White matter
3 layers of meninges
Dura mater
Arachnoid
Pia mater
Lies in the cranial cavity and continuous with Spinal cord through Foramen Magnum
Brain
3 Major divisions of brain
Forebrain
Midbrain
Hindbrain
Meninges:
- outermost; dense, strong, fibrous
- space which contains the CSF; resembles a spider web
- innermost; thin, delicate vascular membrane
Dura mater
Arachnoid
Pia mater
2 structures in Forebrain
Cerebrum and Diencephalon
Largest part of the brain
Cerebrum
A mass of white matter that connects L and R hemisphere of forebrain
Corpus collusum
surface layer of the cerebral hemispheres, arranged into convolutions.
Cerebral cortex
cavity present within each hemisphere; communicates with the 3rd ventricle through the interventricular foramina.
Lateral ventricle
Folds or convulutions of the cerebrum
Gyrus
Fissures of the cerebrum
Sulcus
separates frontal lobe from the parietal lobe
CEntral sulcus of Rolando
separates the temporal lobe from the frontal and parietal lobes
Horizontal fissure of Sylvius/Lateral Sulcus
separates the parietal and occipital lobes
Parieto-occipital fissure
separates the cerebrum and cerebellum
Transverse fissure
divides cerebrum into 2 hemispheres
Longitudinal fissure
Almost completely hidden from the surface of the brain; Consists of thalamus (posterior), hypothalamus (anterior
Diencephalon
Parts of diencephalon
Thalamus and hypothalamus
Connects the forebrain to the hind brain
Midbrain
narrow cavity that connects the 3rd and 4th ventricles
Cerebral aqueduct
part of midbrain posterior to cerebral aqueduct
Tectum
2 swellings of tectum
superior and inferior colliculi
Cerebral peduncles parts
Crus cerebri
Tegmentum
Substantia Nigra
situated in the tegmentum of each side, color red because it is vascular
Red nucleus
Conical in shape, connects the pons superiorly to the spinal cord inferiorly (in the foramen magnum)
Medulla oblongata
Midbrain + Pons + Medulla Oblangata = ?
Brainstem
Parts of hindbrain
Medulla oblongata
Pons
Cerebellum
Parts of medulla oblongata:
- posterior to pyramids
- posterior to olives
- 2 structures found on the posterior surface
- Olives
- Inferior Cerebellar Peduncle
- Nucleus gracili and Nucleus cuneatus
“bridge” situated on anterior of cerebellum; connects the 2 cerebellar hemispheres
Pons
connective tissue from the dura mater which separates the cerebellum and cerebrum
Tentorium cerebelli
Connections of the Cerebellum:
- Superior Cerebellar Peduncle
- Middle Cerebellar Peduncles
- Inferior Cerebellar Peduncles
- midbrain
- Pons
- Medulla oblongata
Communicating network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma
Ventricular system
Ventricular system:
- connects the lateral ventricles to the 3rd ventricle
- connects the 3rd and 4th ventricle
- Interventricular ventricle/Foramen of Monro
2. Aqueduct of Sylvius
Cushions and protects CNS from trauma; Provides mechanical buoyancy; Serves as reservoir and assist in regulation of contents; Nourishment of cells; Removes Metabolites from CNS
CSF
CSF is secreted by?
Choroid plexus
Roughly cylindrical in shape, located within the vertebral canal;
Begins at foramen magnum where it is continuous with the Medulla Oblongata;
Terminates in the lumbar region (L1 for adults, L3 for children)
Spinal cord
conical distal (inferior) end of the spinal cord
Conus medullaris
prolongation of pia mater from the spinal cord
Filum Terminale
collective term for the nerve roots below the spinal cord, resembling a horse tail
Cauda equina
Consists of cranial and spinal nerves and their associated ganglia; Conducts information to and from CNS
PNS
No. of pairs of cranial nerves
12
No. of pairs of spinal nerves
31
Spinal cord motor function
anterior spinal cord
spinal cord on sensory function
posterior spinal cord
Leave the brain and pass through foramina in the skull; Distributed in the head and neck, except cranial nerve X (extends to thorax and abdomen)
Cranial nerves
Made up of a mixture of motor and sensory fibers; Leave the spinal cord and pass through intervertebral column with which they are associated
Spinal nerves
T or F. After emerging from the intervertebral foramen, each spinal nerve immediately divides into a large anterior ramus and a smaller posterior ramus, each containing both motor and sensory fibers.
T
No. of nerves in:
- Cervical vertebra
- Thoracic vertebra
- Lumbar vertebra
- Sacral vertebra
- Coccygeal vertebra
- 8
- 13
- 5
- 5
- 1
They are often irregular in shape and are situated along the course of efferent nerve fibers of the autonomic nervous system.
Ganglia
Fusiform swellings situated on the posterior root of each spinal nerve just proximal to the root’s junction with a corresponding anterior root (posterior root ganglia) and are also found along the course of cranial nerves V, VII, VIII, IX, and X (sensory ganglia of these nerves).
Sensory ganglia
Enumerate cranial nerves
(I-XII) Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal accessory Hypoglossal