PREFI: NERVOUS SYSTEM Flashcards
Most complex system formed by a network of nerve cells (neurons) assisted by many more supporting cells (glial cells)
NERVOUS SYSTEM
CNS IS CONSIST OF?
BRAIN AND SPINAL CORD
white matter?
axons predominate
grey matter?
neuronal perikaryal predominates
PERIPHERAL NERVOUS SYSTEM IS CONSIST OF?
cranial, spinal, and peripheral nerves; ganglia
FUNCTIONAL DIVISION
a. Somatic: sensory input perceived
consciously
b. Visceral: sensory input not perceived
consciously
SENSORY DIVISION (afferent)
FUNCTIONAL DIVISION
a. Somatic: motor output controlled
consciously or voluntarily
b. Autonomic: motor output not
controlled consciously
MOTOR DIVISION (efferent)
gathers information
SENSORY INPUT
process and interpret sensory input; decides if action is needed
INTEGRATION
RESPONSE to integrated stimuli by activating muscles or glands
MOTOR INPUT
- Develops from the ectoderm
- Begins in 3rd-4 th week of development
NERVE TISSUE
gives rise to both spinal cord and brain
Neural plate
functional unit of nervous system
NEURONS
has one axon and two or more dendrites; most common
MULTIPOLAR NEURON
has one axon and one dendrite
BIPOLAR NEURONS
has all other sensory neurons with each having a single process
UNIPOLAR OR PSEUDOUNIPOLAR NEURONS
has many dendrites but no true axon
ANAXONIC NEURONS
- SUPPORT NEURONAL SURVIVAL and activities
- Share the same development with
neurons, from the embryonic neural plate
GLIAL CELLS
GLIAL CELLS IN THE CNS
* Unique feature: proximal regions are
reinforced with bundles of intermediate filaments (glial fibrillary acid protein)
a. Helps form the blood-brain barrier
b. Regulates the ISF composition
c. Provides structural support and
organization to the CNS
d. Assists the neuronal development
e. Replicates to occupy space of dying neurons
ASTROCYTES
TYPE OF ASTROCYTES
- long processes, ABUNDANT IN WHITE MATTER
FIBROUS ASTROCYTES
TYPE OF ASTROCYTES
- short processes, abundant in gray matter
PROTOPLASMIC ASTROCYTES
GLIAL CELLS IN THE CNS
- Lines ventricles of brain and central canal of spinal cord
- Assists in production and circulation of CSF
EPENDYMAL CELLS
GLIAL CELLS IN THE CNS
* EVENLY DISTRIBUTED within WHITE and GRAY MATTER
* Originate from circulating blood monocytes
a. Phagocytic cells moving through CNS
b. PROTECTS CNS by engulfing infectious
agents and other potentially harmful
substances
MICROGLIAL CELLSL
GLIAL CELLS IN THE CNS
* PREDOMINANT glial cell in white matter
* White color: due to lipid concentrated in the wrapped myelin sheaths
a. Myelinates and insulates CNS axons
b. Allows faster action potential propagation along axons in the CNS
OLIGODENDROCYTE
GLIAL CELLS IN THE PNS
- Electrically insulates PNS cell bodies
- Regulates nutrient and waste exchange for cell bodies in ganglia
SATELLITE CELLS
GLIAL CELLS IN THE PNS
* Found only in the PNS
* Named after Theodor Schwann
a. Surround and insulate PNS axons and myelinate those with large diameters
b. Allows faster action potential propagation along an axon in the PNS
NEUROLEMMOCYTE (SCHWANN CELLS)
Clinical Significance
- Brain tumor originating from fibrous
astrocytes - Symptoms: headaches, seizures,
nausea, vomiting, vision problems,
cognitive and behavioral changes
ASTROCYTOMA
CLINICAL SIGNIFICANCE
- Common type of dementia in the elderly, affecting both neuronal perikaryal and synapses within the cerebrum
* Functional defects are caused by neurofibrillary tangles (accumulation of
tau protein) and neuronal plaques (dense aggregates of β-amyloid protein)
Alzheimer’s disease
GLIAL CELL TYPE
Origin: neural tube
Location: CNS
Main functions: myelin production, electrical insulation
OLIGODENDROCYTE
GLIAL CELL TYPE
Origin: neural type
Location: CNS
Main functions: structural and metabolic support of neurons, especially at synapses; repair processes
ASTROCYTE
GLIAL CELL TYPE
Origin: neural type
Location: line ventricles and central canal of CNS
Main functions: aid production and movement of CSF
EPENDYMAL CELL
GLIAL CELL TYPE
Origin: bone marrow (monocyte)
Location: CNS
Main functions: defense and immune-related activities
MICROGLIA
GLIAL CELL TYPE
Origin: neural crest
Location: peripheral nerves
Main functions: myelin production, electrical insulation
SCHWANN CELL
GLIAL CELL TYPE
Origin: neural crest
Location: peripheral ganglia
Main functions: structural and metabolic support for neuronal cell bodies
SATELLITE CELLS (of ganglia)
- Gradual destruction of myelin sheaths
around the axons by an autoimmune
mechanism - Myelin sheaths are converted into
hardened sheaths or scleroses
MULTIPLE SCLEROSIS
- Electrical charge travelling along the
membrane of a neuron - Converts electrical signal from the presynaptic cell into a chemical signal that affects postsynaptic cell
NERVE IMPULSE/ ACTION POTENTIAL
sites where nerve impulse are transmitted from one neuron another or to effector cells
SYNAPSES
action of nerve impulse
release NEUROTRANSMITTERS
used at neuromuscular junctions
ACETYLCHOLINE
CAUSES Na CHANNELS TO OPEN = Na influx initiates depolarization wave
Excitatory synapses
CAUSES Cl OR OTHER ANION CHANNELS TO OPEN= anions influx and hyperpolarization ofthe postsynaptic cell
Inhibitory synapses
Clinical Significance
* GRADUAL LOSS BY APOPTOSIS of DOPAMINE producing neurons whose cell bodies lie within the nuclei of the CNS (substantia nigra)
* Slowly progressing disorder AFFECTING MUSCULAR ACTIVITY
* TREMORS, , reduced activity of the facial
muscles, loss of balance, postural stiffness
* Treatment: ʟ-dopa (L-3,4 dihydroxyphenylalanine): precursor of
dopamine augmenting the declining production of this neurotransmitter
Parkinson’s disease
- Neuronal pathway by which a REFLEX OCCURS
REFLEX ARC
stimulate the SKELETAL
muscles
Somatic reflex
regulate the activity
of SMOOTH muscles, heart, and glands
Autonomic reflex:
CNS
- found in DEEPER REGIONS with myelinated axons (tracts) and oligodendrocytes
White matter:
CNS
- makes up the CORTEX or the SURFACE LAYER OF THE BRAIN with
unmyelinated axons, abundant cell
bodies, dendrites, astrocytes, and
microglial cells
Gray matter
DARKER AREA OF THE BRAIN containing large numbers of cell bodies
CEREBRAL NUCLEI
REGIONS OF THE BRAIN:
o “cerebrum”, “seat of intelligence”
o Largest part of the brain
o Cortex: superficial, gray matter
o White matter: internal area
o Basal nuclei: islands of gray matter deep within the white matter
CEREBRAL HEMISPHERE
REGIONS OF THE BRAIN:
o Deep within the brain
o Responsible for relaying sensory
information between brain regions
Diencephalon “interbrain”
Diencephalon “interbrain”:
- RELAY STATION for sensory impulses passing upward to the
sensory cortex
THALAMUS
Diencephalon “interbrain”:
- REGULATES BODY
TEMPERATURE, WATER BALANCE , and
METABOLISM
- center for many drives
and emotions
- REGULATES PITUITARY GLAND and produce two hormones of its own
HYPOTHALAMUS
Diencephalon “interbrain”:
- : forms the ROOF of the 3rd ventricle
▪ Important parts: pineal gland and choroid plexus of the 3rd ventricle
EPITHALAMUS
REGIONS OF THE BRAIN:
o Attached to the spinal cord
o Responsible for controlling many VITAL FUNCTIONS needed for SURVIVAL: heart
rate, breathing, and blood pressure
o Important parts: midbrain, pons, and
medulla oblongata
BRAIN STEM
BRAIN STEM IMPORTANT PARTS:
- contains VISUAL and AUDITORY reflex centers
- contains subcortical motor centers
MIDBRAIN
BRAIN STEM IMPORTANT PARTS:
- relays information from the cerebrum to the cerebellum
- cooperates with the medullary centers to control respiratory rate and depth
PONS
BRAIN STEM IMPORTANT PARTS:
- relays ASCENDING SENSORY PATHWAY impulses from skin and proprioceptors
- contains nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, etc
- relays sensory information to the cerebellum
MEDULLA OBLONGATA
REGIONS OF THE BRAIN:
o Has two hemispheres and a convoluted surface
o Provides INVOLUNTARY COORDINATION of body movements, controlling BALANCE & EQUILIBRIUM
CEREBELLUM
Clinical Significance
* Inflammation of the meninges
* May be caused by viruses, bacteria, or
other microorganisms
Meningitis
inflammation due to
spread of meningitis to the nervous tissue of CNS
Encephalitis
- Neurological disorder characterized by
CLUMSY or DISORGANIZED MOVEMENTS - May be a result of DAMAGED CEREBELLUM
- Individuals cannot keep their balance
and may appear to be drunk because of
the loss of muscle coordination
Ataxia
- Genetic disease leading to MASSIVE DEGENERATION OF THE BASAL NUCLEI and later
of the CEREBRAL CORTEX - Initial symptoms: wild, jerky movements,
and chorea - Later symptoms: marked mental
deterioration occurs - Terrible three: along with Alzheimer’s
disease and Parkinson’s disease
Huntington’s disease
Protection of the CNS:
- Connective tissue between the bone and
nervous tissue
Meninges
Thick EXTERNAL LAYER made of dense
irregular connective tissue
Dura mater
o WEBLIKE MIDDLE LAYER with avascular
connective tissue
o Has two components:
▪ Sheet of connective tissue in
contact with the dura mater
▪ System of loosely arranged
trabeculae that is continuous with
the pia mater layer
o Subarachnoid space: large, spongelike cavity filled with CSF surrounding
the trabeculae
Arachnoid
o INNERMOST LAYER
o Does not directly contact nerve cells
or fibers, clings to the brain surface
Pia mater
- Functional barrier designed to PROTECT THE BRAIN AND SPINAL CORD from potentially
harmful substances and microorganisms - Useless against fats, respiratory gases,
and fat-soluble molecules: alcohol,
nicotine, anesthesia
Blood-Brain Barrier
Main structural component of Blood-Brain Barrier
capillary endothelium
- REMOVES WATER FROM BLOOD and release it as CSF
- Consists of highly vascular tissue,
elaborately folded and projecting into the large ventricles of the brain - Found in the roofs of the 3rd and 4th ventricle and in parts of the two lateral ventricular walls
Choroid Plexus
similar to blood plasma in composition and forms a WATERY CUSHION to protect the brain
CSF
contains a THIN LAYER of WELL VASCULARIZED PIA MATER covered by cuboidal ependymal cells
Villus
Clinical Significance
- DECREASE IN THE ABSORPTION OF CSF or
excess accumulation of CSF in the ventricles during fetal or postnatal
development
* Promotes progressive enlargement of the head followed by mental impairment
* Treatment: surgery by INSERTING SHUNT to drain excess fluid
Hydrocephalus
Consists of nerves, ganglia, and nerve
endings
PNS (Peripheral Nervous System)
- BUNDLE OF NEURON FIBERS
- Contains axons enclosed with sheaths of glial cells specialized to facilitate axonal
function
NERVES
Connective tissue sheath:
- surrounds each FIBER
Endoneurium
Connective tissue sheath:
- surrounds EACH
fascicle
Perineurium
Connective tissue sheath:
- surrounds ALL
fascicle
Epineurium
CLASSIFICATION OF NERVES:
- carry impulses
TOWARDS CNS
Afferent (sensory) nerve:
CLASSIFICATION OF NERVES:
- carry impulses AWAY
from the CNS
Efferent (motor) nerve
CLASSIFICATION OF NERVES:
- both sensory and motor fibers
Mixed nerve
Autonomic Nervous System:
o “fight-or-flight” response:
▪ Response to unusual stimulus
▪ Takes over to increase activities
o “E” division: exercise, excitement, emergency, and embarrassment
Sympathetic division
Autonomic Nervous System:
o Allows us to UNWIND and CONSERVE ENERGY
o “resting-and-digesting” system:
▪ Response to usual stimulus
▪ Maintains daily necessary body
functions
o “D” division: digestion, defecation,
and diuresis (urination)
Parasympathetic division
