Intro to NS but better Flashcards
What does the NS do?
responds to stimuli
transmits impulses
controls every function in the human body
What are the basic functional units of the NS?
neurons
What does the NS tissue consist of?
neurons (signaling)
glial cell (support)
What is the function of a neuron?
respond to stimuli, convey signals, process info
Awareness of self and surrounding, memory, learning, speech, regulation of muscle contraction and gland secretion
Describe the 3 parts of a neuron?
dendrite- receives and transmits impulses to cell body
cell body- receives impulses from dendrties
axon- transmits impulses away from cell body
Describe the neuronal cell body? What do they contain?
part of neuron that contains nucleus
Maintains neurons integrity
What 2 special organelles are contained in the cytoplasm of a neuron?
nissl bodies- ER, in cytoplasm except where axon emerges, produce proteins
neurofibrils- arranged longitudinally, involved in transport
What part of the neuron can have variable length?
axon
Describe unipolar neurons. Where can they be found?
axon is a single protoplasmic process
mainly in spinal nerves, come cranial nerves
cell bodies in ganglia
Describe bipolar neurons. What pathways is it involved in?
axon and 1 dendrite
visual, auditory, and vestibular pathways
Describe multipolar cells. Where can they be found?
axon and multiple dendrites
everywhere else in NS
What are synapses? What do they rely on?
Junction between axonal ending and a muscle cell, gland, or other neuron.
relies on polarization (always travels away from axon)
What are neurotransmitters? What is their function/effect?
manufactured and released by neurons
released into synaptic cleft to affect postsynaptic neurons, muscle or gland cell
excitatory or inhibitory
Describe the excitatory synapses on neurons.
enhances the production of the impulse
Describe the inhibitory synapses on neurons.
hinders production of the impulse
What types of synapses are excitatory synapses involved in?
neuromuscular
neuro-glandular
neuronal
What types of synapses are inhibitory synapses involved in?
neuronal
What is axoplasmic transport? What are its 2 components?
bidirectional movement within the neurons towards and away from the cell body
Anterograde and retrograde
Describe anterograde axoplasmic transport.
cell body nutrients are carried in a forward direction from the cell body to the termination of the axon
away from CB
Describe retrograde axoplasmic transport.
occurs from the distal end of the axon back to the cell body
enable return of used or worn out materials for restoration or degradation
towards cell body
What is the clinical significance of retrograde axonal transport?
it is the route by which toxins and viruses are transported into the CNS from the PNS
Describe the axoplasmic transport mechanism involved in rabies.
virus enter bloodstream
travels into muscles then nerves where it hijacks the retrograde axonal transport system and travels from PNS to CNS
Muscle, nerve, spine, brain
What is the support tissue (macroglia or glia) of the CNS?
astrocytes
oligodendrocytes
What is the support tissue (macroglia or glia) of the PNS?
schwann cells
capsular cells
Describe astrocytes.
most numerous
vascular end feet form blood-brain barrier, electrolyte balance, neurotrophic factors, removal of neurotransmitters from synaptic cleft (CNS)
control passage of materials into CNA via circulatory system
Describe oligodendrocytes.
forms and maintains the myelin sheath (CNS)
Processes wrap around many axons to form tight spiral
surround cell bodies (no myelin)
produces neurotrophic factors tp promotes growth of damaged axons
Describe Schwann cells
forms the myelin sheath (PNS) enveloped only part of one myelinated axon
Describe capsular cells (satellite cells)
Regulate the neuronal environment (PNS)
surround neuronal cell bodies in sensory autonomic ganglia
describe the shape of the astrocytes that aid in its function.
star-shaped cell body with irregular cellular processes
Cover as much space as possible
Describe the blood brain barrier.
permeability control system governing the passage between capillaries and the CNS parenchyma (tissue)
Tight junctions between endothelial cells
Describe the neurotrophic factors of the astrocytes.
promotes growth of developing and damaged axons
necessary for survival
What are astrocytes highly susceptible to?
formation of neoplasms (abnormal mass of tissue as cells divide and grow
how does the amount of glial cells compare to amount of neurons?
glial cells outnumber neurons 50:1
Describe the central nervous system.
brain and spinal cord
receives, processes and acts on info in the environment
Describe the peripheral nervous system.
connects the CNS to areas outside the NS
Connections made via cranial nerves and spinal nerves
Describe the brain (size, development, peripheral extension).
weighs 3lbs
Reaches max size at age 6
Development complete in early 20s
Peripheral extensions are cranial nerves
Describe the spinal cord (location, peripheral extensions)
extends from brain stem through the neck and back
peripheral extension are spinal nerves
Describe afferent pathways. What are the 3 types of senses?
carry info to brain and spinal cord
sensory
general sense: pain, temp, position
visceral: organs
special: 5 senses
Describe efferent pathways. What are the 2 branches?
controls function
Motor: muscles (somatic)
Visceral: glands (autonomic)
Compare the somatic and autonomic nervous system.
Somatic: voluntary control via skeletal muscles
Autonomic: involuntary, smooth muscle etc
What are the 2 division of the autonomic NS?
sympathetic: stress, fight or flight
parasympathetic: active at rest, rest and digest
Describe the 3 stages of the development of the NS.
blastulation: single-layered
gastrulation: multilayered
neurulation: neural tube
What are the 3 layers of cells formed during gastrulation?
ectoderm- outer, skin and NS
Mesoderm- middle layer, muscle
Endoderm- inner, internal organs
Describe the process of neurulation.
Neural plate into neural tube
notochord is source of midline signals
What will occur if there is a development issue at the stage of neurulation?
midline structures of CNS will not develop properly
ex: cleft palates, midline, skull base
Do midline cranial structures affect the eyes?
Yes
Describe the further development that leads to brain formation and CSF after neurulation.
swellings and outpouching form the parts of the brain
fluid-filled cavities develop into ventricles with CSF
Describe the 2 parts of the prosencephalon (forebrain)
telencephalon- cerebrum
diencephalon- deeper structures, optic nerves enter
What is the mesencephalon?
midbrain
Describe the 2 parts of the rhombencephalon (hindbrain)?
metencephalon- pons/cerebellum
Myelencephalon- medulla
Define anatomical terminology (ventral, dorsal, rostral, caudal)
ventral- front
dorsal- back
rostral- head or anterior
caudal- tail or posterior
Describe the directional terminology of the brain (anterior, posterior, ventral, dorsal). How does this develop?
anterior- front of skull
posterior- back of skull
ventral (inferior)- base of skull
dorsal (superior)- top of skull
takes orientation as neural tube evolves into the brain
Describe the orientation of the forebrain (prosencephalon).
partially sits in middle and anterior cranial fossa
largest part of brain
Describe the telencephalon.
paired cerebral hemispheres (cerebrum)
functional center (sensoryand motor)
integrate highest mental function
(sensory, motor, association)
Describe the diencephalon.
deep nuclear sturctures
Thalamus: relay
Hypothalamus: involuntary, emotions and hormones
Basal ganglia: movement refinement
(relay, functional, integration)
In what area of the brain is involuntary control of the CNS present?
diencephalon
Is the eye part of the CNS? Describe the way the eye is connected to brain.
yes (direct extension)
eye is outpouching of diencephalon
optic nerve transmits info to thalamus
What 2 structural components are involved in the development of the cerebral hemispheres?
gryri (elevated)
sulci (depression)
brain growth limited to cranial cavity so brain folds
What is lissencephaly?
smooth brain (delays at 6-9 months)
abnormal function
What is microcephaly?
arrested brain growth resulting in small brain
can be normal or disabled
What is polymicrogyria?
excessive folding, gyri
thick cortex
disabilities and delays, seizures
What is porencephaly?
cyst or cavity of CSF develops in the brain
What is schizencephally?
abnormal slits or clefts
Do all optic nerves look the same?
no
some may look bad but are completely normal
Can midline cranial defects effect the eye?
yes!!!
affects optic nerve
How are visual system and general developmental abnormalities related?
developmental delay or abnormality may be accompanied by abnormalities in visual system
What are the parts of the cerebral hemisphere?
frontal, temporal, parietal, occipital lobes
What are brodmann’s areas?
over 50 different functional areas of classification in the brain
Describe the function of the frontal lobe.
voluntary movement
personality
initiative and judgement
connection to limbic system
Describe the fissures and sulci that define the frontal sulcus.
in front of central sulcus
lateral fissure between frontal and temporal lobe
sits in anterior cranial fossa
Describe the parietal lobe.
perception of general sensation
Describe the borders of the parietal lobe.
central sulcus separate frontal and parietal
parieto-occipital sulcus midline boundary that separates parietal and occipital lobe
Describe the temporal lobe.
hearing, learning, language
memory, emotion
Describe the borders of the temporal lobe.
sits below lateral fissure
base lies in middle cranial fossa
Describe the occipital lobe.
visual information
primary and secondary areas
What does the parieto-occipital sulcus divide? At what cross-section of the brain can it be seen?
medial view
pareital and occipital
The cerebral hemispheres contains what two tissue types.
Gray and white matter
What is contained in the gray matter?
cell bodies
dendrites
axon terminals
all synapses
What is contained in the white matter?
made of axons connecting the parts of the gray matter to each other and to the rest of the CNS
white because of myelinated axons
What is the correct and incorrect use of the term cerebral cortex?
gray matter (correct)
cerebrum (incorrect)
What do commissional fibers connect? What are the 2 commissional fibers?
right and left halves of the brain
corpus callosum
anterior commissure
What are association fibers?
connect within the same hemisphere (thick neighbors associate)
help the various lobes communicate with each other on same side of brain
What are projection fibers?
connect the cortex with deeper underlying regions of the brain, brainstem and spinal cord
What are the 3 parts of the corpus callosum?
genu- connects homologous parts of frontal lobes
trunk- connects homologous parts of parietal lobe
splenium- connects homologous parts of occipital lobe
Describe the corpus callosum
tough body
connects all lobes on both sides
individual bundles connect frontal, parietal, temporal (superior and occipital lobes
Describe the anterior commissure.
only temporal
connect temporal lobes at midline
interhemispheric transfer of visual. auditory, and olfactory info between temporal lobes
How do seizures occur in the brain?
nerve cells are disturbed causing excessive activity
depending on area of brain excessive motor or sensory could occur
seizure activity can spread within or across hemispheres due to neuronal connection
Describe the procedure of a corpus callosotomy.
cuts the corpus callosum interrupting the spread of seizures from hemispheres to hemispheres
Through what connections can interhemispheric communication remain following a corpus callosotomy?
commissural routes
Why is crawling an important development milestone in babies?
requires coordination of motor between right and left sides of body
What are projection fibers?
connect the cortex with deeper underlying regions of brain, brainstem and spinal cord
Describe the internal capsule.
gathering of cortical projection fibers as they travel between thalamus and deep cortical nuclei
A stroke would be a big deal
Does the internal capsule contain motor sensory or both?
both ascending afferent and descending efferent fibers going to and coming from cerebral cortex
Motor in 1/2, sensory in the other
Describe the organization of the cortical gray matter.
organized into layers to facilitate communication
incoming, outgoing, and commissural info have dedicated layers
Describe the cortical layers.
incoming projection fibers go to layer 4
outgoing arise from layers 5 and 6
commissural fibers originate and project from layer 3
What is the brainstem? What are the 3 parts?
continuous with the spinal cord at the foramen magnum
midbrain
pons
medulla
Describe the white matter of the brainstem.
tracts that transmit sensory and motor between cerebrum and rest of brain/body
Describe the gray matter of the brainstem.
nuclei and functional centers associated with cranial nerves
Describe reticular formation of the brainstem,
network that integrate and controls all activity
run through core of brainstem
maintains level of arousal and sleep
autonomic
What is a tract?
pathways that conveys info from one place to another
input/output
can have overlapping pathways
What are functional paths? How do they relate to tracts?
contain axons of neurons
axons of neurons form bundles called tracts, fasciculi or nerves makes up NS
What cranial nerves are associated with the cerebrum? brainstem?
CN 1 and 2- cerebrum
CN 3-12- brainstem
How do cranial nerves work?
each nerve has one or more nuclei
receive sensory info for cortex and motor for pathways
work with each other
What eye movement does CN 3 coordinate?
SR, SO, MR, IR
What eye movements does CN 4 coordinate?
SO
What eye movements does CN 6 coordinate?
reticular formation connects all CN to ensure coordination in all directions of gaze
Describe the cerebellum (little brain).
receives sensory, limb, and eye movement
input for brainstem, cortical pathways for limb, trunk, and eye movement
smooth coordinated movements
What are cerebellar peduncles?
connect cerebellum to other parts of CNS
Describe the spinal cord.
lowest part of CNS
medulla to neck to back
Functions below the head
Where does the spinal cord begin? End?
foramen magnum
lumbar spine L1 and L2
Describe the direction of function in the spinal cord.
two-way traffic afferent ascending. efferent descending
What two components come together to form one spinal nerve?
ventral and dorsal roots
What 2 pairs of nerves extend from each segment of the spinal cord?
ventral roots: anterior, efferent exit the spinal cord
dorsal roots: posterior, afferent enter the spinal cord
What are dermatomes?
sensory region of the skin innervated by a sensory nerve root
What are myotomes?
muscles innervated by a single nerve root
Does the spinal cord contain white and gray matter?
yes
What are the 3 divisions of white matter in the spinal cord?
posterior (dorsal) funiculus
lateral funiculus
anterior (ventral) funiculus
What is neuropil?
Contained in the gray matter
cell bodies, unmyelinated axons, dendrites, axons, capillaries, glia
Describe the organization of the gray matter.
posterior (dorsal horns: sensory
anterior (ventral) horns: motor
Lateral horns: cell bodies of sympathetic NS
intermediate zones: between anterior and posterior
Is gray matter also in layers for the spinal cord?
Yes
