Chapter 5.2: Central Nervous System Flashcards
the CNS receives input about external and internal environments from the ___ neurons
afferent
___ cells serve as connective tissue in the CNS.
glial
T/F: glial cells are less branched than normal neurons
true
Discuss glial cell concentration and brain size relationship
densities of glial cells positively correlate with brain size. increase brain size = increase glial density.
2 ways glial cells modulate synaptic function
1) takes up and destroys neurotransmitters
2) invovled in memory and learning.
generally, how do glial cells support the neurons metabolically?
the help maintain the composition of the specialized extracellular environments.
4 Major types of glial cells
1) astrocytes
2) oligodendrocytes
3) ependymal cells
4) microglia
most abundant type of glial cell
astrocyte
which cell helps establish blood brain barrier?
astrocyte
6 roles of astrocytes
1) act as main glue of CNS; maintain proper spatial relationships
2) help establish blood brain barrier
3) important for neural scar formation: help repair brain injuries
4) take up excess K+ from the brain ECF when there is HIGH ACTION POTENTIAL activity
5) enhances synapse formation and modifies synaptic transmission
6) neurotransmitter modulation.
How do astrocytes communicate with other neurons?
through gap junctions.
what is the role of astrocytes during fetal development
guides neurons to proper final destination during featal brain development.
T/F: Astrocytes store glycogen
true
how do astrocytes air in neurotrasmitter modulation?
helps takes up GABA and Glutamate.
Why is it so important that excess ECF K+ is taken up by astrocytes when there is high action potential activity? What happens if there is a deficiency in astrocytes?
- there is excess K+ becuase the Na+/+ATPASE pump is out paced and cannot work fast enough to pump K+ back into the neuron/
- helps maintain proper ion concentration in brain ECF
- prevents cell from getting closer to threshold potential during periods of increase activity.
- astrocytes deficiency linked to epilepsy
how do astrocytes create new synapses?
extensions from astrocytes wedge themselves between pre and post synaptic neurons and has the ability to retract extensions using actin filaments.
also can release a large protein that can trigger synapse formation when stimulated by Ca2+ influx into the cell.
main functions of oligodendrocytes
an oligodendrocyte contains projections which wrap spirally around a section to form a MYELIN. only one oligodendrocyte per neuron.
MS arises due to a deficiency of which type of glial cell?
oligodendrocytes.
Where can you find ependymal cells? What do they do?
Ependymal cells line internal cavities of the vertebrate CNS and brain ventricles.
- forms cerebrospinal fluid
- propels CSF through ventricles using cilia
- acts as neural stem cells: forms both new neurons and glial cells.
Microglia are formed by _____. What are they?
formed by MONOCYTES: type of white blood cell that exits the blood and set up residence as the frontline defense agents in various bodily tissue.
Differences between inactive and active states of microglia
inactive state: microglia appear wispy with radiations of branches. They secrete NERVE GROWTH FACTOR: helps neurons and other glial cells survive and thrive
active state: branches retract and they become MOBILE. the move to affected area and remove foreign invaders or tissue debris by releasing destructive chemicals.
Characteristics of ganglia
1) serves limited regions or segments
2) homogenous mixture of neurons and fibers
3) few interneurons
4) predominately MONOSYNAPTIC
5) all neurons and fivers in ganglia serve a similar function.
4 Major features that protect vertebrate CNS
1) CNS is enclosed by bone structures
2) meninges
3) CSF
4) blood brain barrier.
the brain is enclosed by the ___, the ___ __ surrounds the spinal cord
brain enclosed by cranium
vertebral column surrounds the spinal cord.
two parts of the cranium
1) cranial vault: superior, lateral and posterior aspects of the skull
2) cranial base: inferior aspect of the skull
3 parts of the meninges
1) dura mater: most outer layer, attached to the inner skull
2) arachnoid layer: middle later.
3) pia mater: delicate inner most tissue.
which part of the meninges has the most blood vessels?
the pia mater
How is the brain able to float in the CSF?
CSF actually has the same density as the brain
ionic makeup of CSF.
lower in K+ and higher in Na+ compared to blood. allows for gradient movement.
T/F: there is plasma in CSF
false
What makes CSF? What js this region made of?
CSF made by transport mechanisms across the membranes of the choroid plexus of the ventricular regions
the choroid plexus itself is made up of vascularized PIA MATER, which was formed by EPENDYMAL CELLS.
Anatomical features of the BBB
SINGLE LAYER of ENDOTHELIAL cells forms capillary walls and joined by TIGHT JUNCTIONS that seal the capillary walls so nothing can be exchanged.
Transport across brain capillary walls between endothelial cells is prevented ____, and transport through cells is restricted _____.
Transport across brain capillary walls between endothelial cells is prevented ANATOMICALLY (tight junctions), and transport through cells is restricted PHYSIOLOGICALLY (only possible way to passively exchange something is through the capillary bed itself.
What is neuroglobin
a protein (like Hb) that binds O2 and aids with diffusion and storage of O2 in neurons
Why is hypoxia detrimental? outline the process of neuronal death
O2 depletion prevents respiration and the formation of ATP. No ATP = no pumping of neurotransmitters or maintenance of gradients.
- if the gradients are not maintained, the neurons will DEPOLARIZE and release excessive levels of excitotoxic NTs such as glutamate.
- overstimulation of glutamate receptors increases Ca2+ levels and triggers internal cascades that result in cell damage and death.
Themes in Hypoxic Brains
1) key mechanism is to enter a hypo-metabolic state
2) Functional nature of specialization:
a) improved O2 delivery or using O2 buffers like NEUROGLOBIN to reduce hypoxic effects
b) reduction of energy consumption
c) alterations of cellular metabolism in glia and neurons
d) protection against excitotoxic damage
e) protection against anoxic stress induced necrosis and apoptosis
f) prevention of oxidative stress during re-oxygenation
g) promotion of restorative processes
MEMORIZE ONE HYPOXIC ANIMAL CHARACTERISTIC
Turtles that spend winter under the ice
1) they enter a state of deep reversible HYPOMETABOLSIM using ANAEROBIC GLYCOLYSIS
2) increased neural inhibiton: GABA interneuron activation depresses glutaminergic neurons.
3) Increases in neural protection such as antioxidant production, heat shock proteins and antiapoptotic factors
4) Ca2+ IN SHELL CAN BE USED TO BUFFER BLOOD AGAINST pH CHANGES FROM ANAEROBIC METABOLISM
Primary regions of the brain with plastic features retained in adulthood
1) hippocampus. Agranular surrounding tissue are sites of cell proliferation
2) subventricular zone. site of neurogenesis that is associated with the lateral ventricles
3) Hypothalamus: grows in response to environmental signals
4) spinal cord. Capable of neurogenesis and can repair itself to an extent after injury
3 distint areas of the brain. How were they formed relative to each other?
1) hindbrain
2) midbrain
3) forebrain
newer and more sophisticated regions are piled on top of older and more primitive regions.
2 hypotheses to explain brain size in primates
1) expensive tissue hypothesis: neural tissue is energetically costly. The costs need to be offset; big brained primates must eat higher quality food
2) maternal investment hypothesis: ultimate brain size depends on the allocation of maternal resources to fetal and post natal development.
Main function of brain stem
coordinates reflex responses to sight and sound. Plays role in sleep wake cycle and receives and integrates all synaptic input from the spinal cord.
which brain region to cranial nerves stem from
the brain stem
2 regions of the forebrain
1) diencephalon: includes thalamus and hypothalamus
2) cerebrum: includes cerebral cortex and basal nuclei
the spinal cord extends from the __ ___ and is enclosed by the protective ___ ___ that extends through the ___ ___
the spinal cord extends from the BRAIN STEM and is enclosed by the protective VERTEBRAL COLUMN that extends through the VERTEBRAL CANAL
We have 31 paired human nerves. How are they allocated?
8 cranial nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygeal nerve (cauda equina)
white matter of spinal cord is organized into ____
tracts
white matter tracts relay messages from ___ to ____
from brain to efferent neurons
each horn of grey matter houses a different ___ ___ ___
neuronal cell body
3 primary grey matter horns
1) dorsal root
2) ventral horn
3) lateral horn
what cell body does the dorsal horn house
the cell body of INTERNEURON on which afferent enruons terminate. Posteriorly positioned. Recall that the afferent neuron cell body is not actually in the CNS
what cell body does the ventral root horn house
the efferent cell body, outgoing signals. Anteriorly positioned.
what cell body does the lateral horn house
autonomic nerve fibers supplying cardiac and smooth muscle.
___ matter is made of tightly packed cell bodies, dendrites and glial cells that are divided into dorsal, ventral and lateral horns
GREY MATTER
____ matter is bundled into tracts of myelinated nerve fibers and are both ascending and decending
WHITE MATTER
What is a dermatome? what’s its role in referred pain?
a specific region of the body surface supplied by a particular spinal nerve.
sometimes the same spinal nerve also branches off to internal organs, and sometimes pain originating from an organ might by referred to the dermatome (ex/ heart pain felt in arm)
most spinal reflexes are ___ and ___ movement.
patterned and stereotyped movement. response is predictable because pathway between receptor and effector is always the same.
___ ___ and ____ integrate basic reflexes
spinal cord and brainstem
In the withdrawal reflex, when the afferent neuron gets stimulated and propagates the signal to the spinal cord, what are the 3 interneurons it diverges on?
1) the excitatory interneuron that stimulates the effent bicep motor neuron to withdraw the hand
2) the inhibitory interneuron that inhibits the antagonistic muscle of the bicep (the tricep) to facilitate movement in appropriate direction
3) interneurons that carry signal up the spinal cord to the brain via an ascending pathway.
____ synaptic stretch reflexes utilize an interneuron between afferent and efferent neurons in the spinal cord
polysynaptic.
reciprocal innervation:
a neuronal connection type involving stimulation of nerve supply to one muscle and simultaneous inhibition of the nerves to its antagonistic muscle.
what is the crossed extensor reflex?
coupled with the withdrawal reflex, there are two additional interneurons that the afferent neuron innervates which allows the animal to put weight on the other limb while withdrawing the affected limb from the aversive stimulus
the two additional interneurons are involved in reciprocal innervation of the other leg to bear weight.
What is a fixed action pattern?
instinctive behavrioal sequence that is generated in response to specific stimuli. Once activated, the complete sequence of movement is carried out.
