Cells of the Nervous System Flashcards
What do neurons do?
receive stimuli and;
transmit signals to other neurons or effector organs
Dendrites
receive input and can interact w axons of other neurons
Trigger zone composed of what?
Why is this important
Initial segment: part after axon hillock
axon hillock : cone shaped part, closer to dendrite end
Important bc it is the region where action potentials are generated
Axonal transport
- how diseases end up in CNS, bypasses BBB
ex. rabies, herpes - uses neurotransmitters, stores and transported in vesicles
neurotransmitters
chemicals that create stimulus or inhibitory response in effector tissue/ gland
3 types of neurons
sensory
motor
interneurons
Sensory neurons
afferent: transmit action potentials to CNS
Motor neurons
efferent: transmit action potentials away from CNS
Interneurons
association: w/in CNS
carry info from 1 neuron to another
3 types of neuron structure
Multipolar
Bipolar
Unipolar
Neuroglia
nerve glue
numerous: >50% of the brain’s mass
4 types in CNS
2 types of PNS
Types of neuroglia in CNS
Astrocytes
microglia
ependymal cells
oligodendrocytes
Types of neuroglia in PNS
Schwann cells
satellite cells
Types of neuroglia in PNS
Schwann cells
satellite cells
astrocytes
star shaped, largest and most numerous
- cytoplasmic extensions cover surfaces of blood vessels, neurons, pia mater
- release chemicals from tight junctions b/w endothelial cells of capillaries
BBB- regulate movement of substances into and out of the brain
ependymal cells
- line ventricles of the brain & central canal of spinal cord
- helps choroid plexuses produce CSF
- some ciliated patches help circulate CSF
Microglia
protection
- specialized microphages that digest damaged tissues, foreign materials, microorganisms that enter CNS
oligodendrocytes
cytoplasmic projections reach our and wrap around (multiple times) portions of axons, creating myelin sheaths
Schwann cells
wrap around and from myelin sheath around axons
phospholipid bilayer folds on itself multiple times and becomes v thick layer of fatty proctection
satellite cells
flattened cells
surround cell bodies in ganglia
provide nutrients to cell body
myelinated axons
- conduct signals faster via nodes of ranvier
- better insulated, protected
unmyelinated axons
- slower transmission of action potentials
- multiple axons push through schwann cell memebrane and it wraps around them 1 layer (vs multiple)
tract
bundle of myelinated axons in CNS
nucleus (pl: nuclei)
collection of neuron cell bodies in CNS
white matter
- myelinated axons
- nerve tracts transmit action potentials bw one area of the CNS and another
gray matter
- unmyelinated axons, cell bodies, neuroglia
- cell bodies come in contact with oneanother
- where synapses are, decision being made here
white and gray matter in spinal cord
white is outer
gray is deeper
white and gray matter in brain
gray is outer + inner nuclei are gray matter inside brain
white in deeper
brainstem
connects spinal cord to brain
3 regions: midbrain, pons, medulla oblongata
cerebellum
little brain
only attached through brainstem
controls locomotion, balance, posture, coordination
diencephalon
thalamus, epithalamus, hypothalamus
located right on top of midbrain
cerebrum
higher order processing
conscious thought
coordination of diff regions of brain
Protection of brain
- cranial bones (8)
- cranial meninges:
dura, arachnoid, pia mater - CSF
Dura Mater
in brain 2 layers, in spinal cord only 1
composed of dense irregular connective tissue
Falx Cerebri
- double layer of meningeal layer sits in longitudinal fissure
- keeps brain anchored
Outer layer of dura mater
periosteal layer
connects to bone
Inner layer of dura mater
meningeal layer
folding of this layer creates a dural venous sinus
ex. super sagittal sinus where all capillaries of the brain drain to
Arachnoid Mater
creates weblike projections that help secure brain in place?
subarachnoid space
space bw layers where CSF circulates
Pia Mater
goes in every groove of brain
what do the ventricles of the brain do?
choroid plexus creates CSF
how many ventricles of the brain are there?
there are four:
2 lateral (bilareral)
3rd ventricle
4th ventricle
What is CSF
cerebrospinal fluid
provides shock absorption for your brain
creates optimal chemical env’t for brain (chem conc, pH)
a filtrate of blood
What are the components of a choroid plexus?
How is CSF synthesized?
blood capillary flows through choroid plexus.
double filter action:
endothelial cells of capillary and specialized ependymal cells from tight junctions, removing all blood cells, proteins
leaves serum like fluid w glucose, dissolved oxygen & some ions
Path of CSF flow
- produced in choroid plexuses of bilateral, 3rd, 4th ventricles
lateral vent > interventricular foramen > 3rd vent > cerebral aqueduct > 4th vent > lateral and medial apertures > subarachnoid space > arachnoid villi of dural venous sinuses > venous circulation > heart, lungs
Medulla Oblongata
attaches to spinal cord & changes from H shape to diff shape: more gray matter, white matter pushed to outside
- gray matter: centre for vital reflexes ex. respiration, BP
- nuclei of cranial nerves VIII, IX, X, XI, XII
Pyramids
2 columns of white matter
motor nerve tracts of somatic nervous system (skeletal muscle, descending axons only)
Decussation of pyramids
where 2 pyramids cross (90% of the axons in them)
the reason why L side of brain controls R side of body and vice versa
Olives
gray matter, nuclei involved in balance, coordination, sound modulation
What is hydrocephalus?
- caused by narrowing of cerebral aqueduct; 3rd and lateral ventricles become enlarged
- infant brain (head) keeps growing bc fissures on cranium have not yet fused
treatment of hydrocephalus
Shunt put into lateral ventricles and excess CSF diverted to peritoneal space or right atrium of the heart
- usually as children grow the cerebral aqueduct also grows and they no longer need this shunt system (25% need this for life)
