MNSR12 Flashcards
The function of a nervous system is:
- To coordinate the activity of the muscles
- To monitor the organs
- To construct and stop input from the senses (sight,
hearing, touch, smell, taste) - To initiate actions
Cells that receive sensations are called
receptors
Cells that make the appropriate response are called
effectors
what is the nervous system divided into
-Central Nervous System (CNS)
*Brain
*Spinal cord
-Peripheral Nervous System (PN.
* All other nerves and neurons
that do not lie within the CNS
Tissues of the body develop from three primary germ layers:
Ectoderm, Endoderm, and Mesoderm
Central Nervous System (CNS)
-Develops from a specialized
region of _______ called the
_______. developement of neural system called ______.
ectoderm,
neural plate
neurulation
Some ______ cells form a hollow
tube in the midline which by day 22-24
forms a solid cylinder of cells (notochord)
mesodermal
the notochord drives
neurulation
what is neurulation
induction of overlying ectoderm to form the neural tube
Malformations of the neural tube are
known as
Neural Tube Disorders (NTDs)
3 Most common tube defects
—Anencephaly (head)
—Encephalocele (Head)
—Spina bifida (spine)
what prevents NTDs
Folic Acid Supplements
what is folic acid supplements
- Supplementation prevents neural
tube defects. - Also known as Natural B vitamin
(vitamin B9). - First isolated from spinach leaves.
- Needed to synthesize DNA bases.
- ~70% reduction in NTDs with
400mg/daily (100% RDA)
periconceptional use. - Also used to alleviate side-effects
of some immunosuppressant
drugs.
what time period is folic acid supplements used
1 month before conception to 12
weeks post-conception.
what does PNS split into
autonomic and somatic
what does autonomic nervous system split into
sympathetic, parasympathetic and enteric
what does somatic nervous system consist of
- Includes all neurons connected with
the muscles, sense organs and skin
which information does somatic nervous system deal with
sensory from sense receptors to spinal chord
where does somatic nervous system control the body movements from
from spinal chord to muscles
neuron Consists of four parts:
- Dendrites
- Soma (cell body)
- Axon
- Synaptic terminal
where is the nucleus located in neuron
soma
what is cytoplasm called in neuron
perikarvon
what does nissl bodies consist of
- Formed of large aggregations
of rough ER - Site of protein synthesis
what are microfilaments and microtubule called in neuron
neurofilaments and neurotubules
where are neurotubules found
Found in the axons and
dendrites
dendrite size
<1 mm
axon size
up to 1 meter
- Longest nerve is the
Sciatic
nerve (ischiatic nerve).
Damage to the Sciatic nerve
called.
sciatica
3 types of neurons+describe them
Pseudo-unipolar - sensory.
Bipolar - specialised. sensory
neurons found in the retina,
inner ear and olfactory
mucosa.
Multipolar - the most
common.
Pseudounipolar structure and function
- Sensory neuron in the PNS
Connects sensory organ to the spinal cord - A single process extending from the soma
- One long dendrite (exception!)
- One short axon
-Connects to the spinal cord - The dendrite of a pseudo-unipolar neuron is structurally and
functionally an axon
-Myelinated
bipolar structure and function
Transmission of specialized senses (e.g. eye)
One dendrite
One axon
Part of the sensory pathway
Smell, sight, taste, hearing and vestibular functions
multipolar structure and function
- Many dendrites
- One single axon (usually long and
may branch) - Large amounts of information
received - Largely based in the CNS
- Motor neurons (efferent)
- Interneurons
what is a ganglia
a mass of
nerve cell bodies and dendritic structures outside of CNS walls
is brain a fusion of many ganglia?
yes
what is a plexus
interconnections between ganglia
to form a complex system of ganglia.
what does a ganglia contain
mainly of somata and
dendritic structures.
what does a galgia network provide
Provide relay points and
intermediary connections between
different neurological structures in
the body, such as the peripheral and
central nervous systems.
what is the Brachial Plexus
Nerve supply to shoulders and upper
limbs.
when do Brachial Plexus injuries happen
during birth
what happens during Brachial Plexus injury
-The baby’s shoulders may become
impacted (compressed) during the birth
process causing the brachial plexus
nerves to stretch or tear.
Limp or paralyzed arm, lack of muscle
control in the arm, hand, or wrist, and
lack of feeling or sensation in the arm of hand.
Prognosis depends on grade of injury:
—Physiotherapy
—Occupational therapy
—Surgery
what do the cellular and fibrous structures in neuron of CNS divide into
Grey matter and white matter
what does the grey matter consist of
somata dendrites and few axons
what does the white matter of CNS consist of
exclusively of axons
nerve cells (and their extensions) are surrounded by non-nervous cells called
glial cells/neuroglia
In the PNS the glial cell is called the
Schwann cell
- This may wrap around the axon
- Forms a myelin sheath
The _____ is a layer of myelin and
connective tissue that surrounds and insulates
fibres in the peripheral nerves.
nerve sheath
describe the thickness of the nerve sheath
This sheath is usually as thick as the axon but may be up to 2.5um thick in large fibres.
what is the nerve sheath composed of
Largely composed of a lipid (sphingomyelin), which forms much of the concentric wrappings of the Schwann cell membrane.
In the CNS, a neuroglial cell called the
___________ forms the myelin sheath,
usually around several axons.
oligodendrocyte
purpose of myelin in Myelinated Nerve Fibres
provide insulation to axon
when does myelination begin
starts during foetal life in the fourth
month, and continues for a considerable time after birth.
know this as well:
As the process continues the cytoplasm is excluded so at maturity the sheath consists of many regular layers of plasma membrane.
what are the nodes of ranvier
Gaps between the adjacent Schwann
cells in myelinated fibres.
what is an axolemma
plasma membrane of axon
size of gaps in nodes of ravier
The internodal distance varies
proportionally with the diameter of
the fibre from 0.3 to 1.5 mm in the
PNS.
Almost all axons greater than ____________ are myelinated.
Almost all axons greater than [2
um in diameter] are myelinated.
usual size of non myelinated nerve fibres
<2 um in diameter
true/false. can multiple axons share schwann cell?
True
describe a mesaxon
a pair of parallel plasma membranes of a Schwann cell, marking the point of Schwann cell encircling the axon.
in non myelinated axons, The axons are not wrapped in myelin, so where are they
embedded in a
groove in the Schwann cell cytoplasm, which fuses forming
the mesaxon
describe the peripheral nerves
the Peripheral Connect the brain and spinal cord (=CNS) to the entire body. anatomical structures consisting of many nerve fibres.
The cell bodies or somata of
these fibres are located either in
the CNS or in cranio-spinal
ganglia.
what is a bundle of nerve fibres called
fascicles
describe the structure of Peripheral nerves
- consists of nerve
fibres called the FASCICLE
fibres in a matrix of loose collagen
fibres and blood capillaries the
ENDONEURIUM.
Each fascicle is bound by a dense
layer of collagen called the
PERINEURIUM.
In large nerve trunks, such as the
sciatic nerve, several fascicles may
be found.
they are bound within an outer
layer of connective tissue called
the EPINEURIUM.
what causes multiple sclerosis
loss of myelin sheath
what demographic do most cases of multiple sclerosis happen
between 2nd and 5th decade of life
80/100,000 of population
higher in
temperate climates and
among European populations
with a male:female ratio of
1:1.5
what happens during multiple sclerosis
The oligodendrocytes in the CNS
which produce myelin are the target
of recurrent autoimmune cell-
mediated attack.
It may affect any myelinated tract
(containing sensory, motor,
interneurons).
Loss of myelin is selective and
patchy:
*Characteristic lesions or plaques of
demyelination
*The ‘denuded’ axons also undergo
large-scale degeneration
multiple sclerosis symptoms
This may lead to;
* Partial or complete
blindness
* Mild to severe sensory or
motor disorders of limbs
causing spastic paralysis
Chronic remitting disease
* 80% of cases may
eventually lead to total
disability.
what does neurogenesis refer to
growth and development of neurons from neural stem cells and progenitor cells (=a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its “target” cell.)
Most active while a baby is developing in the womb and is responsible
for the production of the brain’s neurons.
3 regions of mammalian brain where neurogenesis occurs in
- In the hippocampus, which is a region that is involved in regulating learning
and memory - the sub-ventricular zone (SV), which is situated throughout the lateral walls
of the brain’s lateral ventricles - the Amygdala
how does voltage gated ion channels work
- Usually closed at resting membrane potential
- A change in the membrane potential near the channel causes a
conformational changes that result in the opening of the channel
(voltage-dependent activation), followed by conformational change
(inactivation) that closes the channel.
which inorganic ions are commonly transported via ion channels
Na+, K+, Ca2+, or Cl-.
lon channels are “gated”, i.e. they open in response to a
specific stimulus, such as a ________________
(voltage-gated ion channels) or the ______________
(ligand-gated ion channels).
change in membrane potential
binding of a neurotransmitter
what are the 2 types of ion channels
Ligand-gated and Voltage gated ion channels
how does Ligand-gated ion channels (LGICs) function
The ion channel undergoes a conformational change following the
binding of an extracellular ligand to its site on the channel.
This conformational change allows for opening of the ion pore.
This gating will cease when the ligand disassociates from the
binding site.
The LGIC group includes the nicotinic acetylcholine receptor
(nAChR).
what are Voltage gated ion channels
class of transmembrane proteins that form ion channels.
responsible for generation and propagation of action
potentials in excitable tissue.
where does LGIC function
in the nervous system and somatic neuromuscular junction.
in LGIC. Ion flux is passive and driven by the ____________
gradient for the ions.
electrochemical
what are ion transporters
Transmembrane proteins that actively move ions and/or
solutes against a concentration or electrochemical
gradient across biological membranes.
pumps generate membrane potential by creating an electrochemical gradient across membrane
Primary active transporters are usually
transmembrane ATPases, that hydrolyse ATP to produce energy in order to transport ions up a concentration gradient. - Secondary active transporters, also known as co-
transporters, pump ions against the concentration gradient by using the electrochemical gradient created across the membrane by pumping ions in or out of the cell.
- Secondary active transporters, also known as co- transporters,
pump ions against the concentration
gradient by using the electrochemical gradient created across the membrane by pumping ions in or out of the cell.
describe antiport
pump two different ions or solutes in
opposite directions across the membrane. One moves
with the concentration gradient (high to low) which powers
the movement of the other against the gradient (low to
high). Examples: CLCN3, NHE3.
describe symport
two different ions or solutes in the
same direction, moving one with the concentration gradient (high to low), and the other against the concentration gradient (low to high). Examples: KCC2,
NCC, NIS, NKCC2.
examples of symport transporters
- Na*/glucose co-transporter
- Na+/K+/2CI cotransporter
- Nat/iodide symporter
- Nat/phosphate co-transporter
(sodium-dependent co-ntransporters)
example of antiport transporters
— Na+/H† exchanger
— Na+/Ca?+ exchanger
Both of these transporters use the chemical gradient of
Na+ to transport substances out of the cell.
