L13 and L14 - CNS Flashcards
General purpose of glial cells?
- serve as CONNECTIVE TISSUE of the CNS (thus support the neurons)
- provide physical, metabolic, and functional support to neurons
- maintain composition of extracellular environment surrounding neurons
- modulate synaptic functions (take up/destroy NTs)
T/F glial cells can initiate and conduct action potentials?
FALSE
4 major types of glial cells
astrocytesm oligodendrocytes, ependymal cells, and microglia
Which is the most abundant glial cell in the CNS?
astrocytes
Key astrocyte functions you should know:
- holds neuron together (like scaffolding)
- takes up GABA
- trasnfers nutrients from blood to neurons
- store glycogen
- Helps maintain proper ion concentration in the ECF:
- —–>takes up excess K+ from the brain ECF when high AP activity outpaces the ability of the Na+/K+ pump to return K+ to the neuron.
- Enhances synapse formation and modifies synaptic transmition:
- ——> extensions from astrocytes wedge themselves between pre- and postsynaptic portions of nearby neurons.
- ——->have the ability to retract extensions using actin filaments to CREATE NEW SYNAPSES.
- Communication with neurons (by passing chem signals through gap junctions w/o them entering the ECF)
- secrete thrombospondin (large protein) to trigger synaptic formation.
Oligodendrocytes form the ______ around _____ in the CNS
Oligodendrocytes for the MYELIN SHEATS around AXONS in the CNS
the disease MS is related to the injury of ____
oligodendrocytes.
Where are ependymal cells located?
ependymal cells line internal cavities of vertebrate CNS and ventricles of the brain.
Microglia are similar to ____ but in the CNS
white blood cells
When are microglia activated?
Microglia remain stationary in the CNS until activated by an infection or injury
Describe the resting and active structure of microglia
In their resting state, microglia are wispy cells with long radiating branches.
When active, microgia retract their branches, round up, and become highly mobile. Move toward affected area to remove foreign invaders or tissue debris
Microglia release ________ to promote neuron ___
Microgia release NERVE GROWTH FACTOR to promote neuron HEALTH.
oligodendrocytes are similar to ______ in the PNS
Schwann cells
Cerebra palsy is associated with which glial cells?
oligodrendrocytes
ependymal cells contribute to the formation of _____
cerebrospinal fluid
which glial cell has a neural stem which can produce new glial cells and neurons?
ependyma cells
ependymal cells have ___ that help move ____ through _____
ependymal cells have -CILIA that help move FLUID through VENTRICLES
The vertebrate brain is organized into 3 distinct regions which form from three successive portions of the embryonic neural tube:
- hindbrain
- midbrain
- forebrain
Simply put, what is a ganglion?
cluster of neurons
What animal does not have neurons?
sponges
What animals have neruons, but not in clusters (ganglions)?
hydras, jellyfishes and anemones
Flatworms have an aggregate of nerve cells in the head called ________
cephalic ganglion
List the 5 characteristics of ganglia
- serves limited regions or segments
- homogenous mixture of neurons and fibers
- few interneurons
- monosynaptic relays are predominant
- no local specialization of function
Bilaterian characteristics:
- head and tail (anterior/posterior)
- back and belly (dorsal/ventral)
- most bilateral embryos have three germ layers
- most are bilaterally symmetrical (exception: echinoderms)
- most have a mouth and anus
Annelida (segmented worms ) have a brain T/F?
TRUE
Function of the forebrain
receives, integrates sensory info from nose, eyes, and ears.
Function of the midbrain
coordinates reflex responses to sights and sounds
Function of hindbrain
reflex control of respiration, blood circulation, other basic tasks.
Coordination of sensory input, motor dexterity, and possibly mental dexterity
Which have bigger brains? perching birds or migratory birds?
Perching birds.
primates who consume leaves generally have ____ brains than those that eat fruit
primates who consume leaves generally have SMALLER brains than those that eat fruit
Carnivores tend to have ____ brains than herbivores
LARGER
Expensive-tissue hypothesis
- explains relative brain size
- in this model, the cost of maintaining increasingly larger brains is offset by a corresponding reduction in the size of the intestinal tract.
- Therefore, big-brained primates therefore must eat high quality food
Maternal investment hypothesis
- states that ultimate brain size depends on the allocation of maternal resources to fetal and postnatal development.
- resources provided by the mother can be directly linked to brain deveopment in her offspring
4 ways in which the brain is protected:
- CRANIUM (skull) encases the brain and VERTEBRAL COLUMN surrounds the spinal cord
- 3 membranes: meninges (MENINGES): dura mater, arachnoid mater, and pia mater.
- Cushioning fluid: CEREBROSPINAL FLUID
- BLOOD-BRAIN BARRIER (highly selective)
2 parts of the cranium:
- Cranial vault: superior, lateral and posterior aspects of the skull.
- Cranial base: inferior aspects of the skull.
3 meninges:
- dura mater
- arachnoid mater
- pia mater
Dua mater:
tough, leathery membrane attached to the inner skull
Arachnoid mater:
- middle layer
- loose brain covering
- connected to pia mater through spiderweb-like extensions
pia mater:
- delicate connective tissue with lots of tiny blood vessels.
- clings tightly to the brain (like plastic wrap)
Function of CSF
- surrounds and cushions the brain and spinal cord
- serves as shock-absorbing fluid
- key for MATERIAL EXCHANGE between neural cells and interstitial fluid
CSF is ____ in K+ and ____ in Na+ than blood, making it ideal for __________
CSF is LOWER in K+ and HIGHER in Na+ than blood, making it ideal for MOVEMENT OF THESE IONS DOWN THEIR CONC. GRADIENTS
if K+ concentration were to double in the blood, what would happen to its level in the brain interstitial fluid?
there would be little change in K+ due to the BBB
in brain capillaries, cells are joined by ____ ____, which seal the capillary wall and nothing can cross the wall by passing between cells
TIGHT JUNCTIONS
How do lipid soluble substances (ex: O2, CO2, alcohol, and steroid hormones penetrate capillary cells in BBB?
by dissolving in the lipid plasma membrane
How are substances such as glucose, amino acids, and ions transported across the BBB?
via highly selective membrane-bound carriers
Only possible exchange of materials to brain is through __________-
capillary cells
Vertebrate brains cannot produce ATP in the absence of ___
Oxygen
What is the cell which plays a key role in O2 diffusion and storage in neurons?
neuroglobin
Under normal conditions, brain use only ____ as fuel
glucose
Under starvation, the brain uses ___ and _____ as fuel
glucose and ketone bodies
What do fish and turtles do to cope with low oxygen levels in the winter due to frozen surface of water?
Their cells consume ATP at a much lower rate and thus require less O2.
What percentage of oxygen is needed for the brain in humans?
20%
what is it called when there is a low level of oxygen available in the environment?
hypoxia
Why is oxygen deprivation bad?
- because ATP-dependent processes (including ion transportand NT reuptake) decline sharply.
- without pumping, ion gradient fails and neurons depolarize. This causes excess release of NT such as glutamate and dopamine.
- overstimulation of glutamate receptors increases intracellular calcium levels leading to cell damage and death
give examples of vertebrates which experience chronic hyopxia:
naked mole rates (all life) freshwater turtles (seasonal) ground squirrels (seasonal)
give examples of vertebrates which experience behavioural/acute hypoxia
seals and whales (minutes to hours): hold breaths during diving events.
how do insects and carp survive in hypoxic conditions?
Their brains store more glycogen in glial cells.
The glycogen is converted to glucose, to pyruvate, to ALANINE, which is transported to nerve cells.
How do moths survive in ow oxygen?
they have a high capacity to oxidize fatty acids into fuel.
list some adaptations that make turtles tolerant to anoxia
- enter a state of deep, reversible hypo-metabolism (only use ANAEROBIC glycolysis).
- GABA causes presynaptic inhibition of glutamate release (reduction of release of excitatory NTs) - reduced ion permeablity and suppression of actions potentials to save energy
- increase neuron protection (anti-oxidants, heat shock protection, anti-apoptotic factors)
- Calcium in shell can be used to buffer blood against pH changes from anaerobic metabolism (due to buildup of lactic acid)
A key mechanism in hypoxic brains is to enter a _______ state
hypo-metabolic
Functional nature of specialization:
a. improved O2 delivery or using molecular O2 buffers (eg. neuroglobin) reduces effects of hypoxia on brain
b. reduction or restriction of energy consumption
c. alterations of cellular metabolism in glia and neurons
d. protection against excitoxic damage
e. protection against anoxic stress-induced necrosis and apoptosis
f. prevention of oxidative stress during re-oxygenation
g. promotion of restorative processes
6 brain components we need to know:
brainstem cerebellum cerebral cortex basal nuclei thalamus hypothalamus
most ancient brain component
brain stem
2 subdivisions of the forebrain
diencephalon and cerebrum
