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MBBCh 1- APES1001A > The Nervous System > Flashcards

The Nervous System Flashcards

1
Q

Nerves emanate from the ____ and ___ ___ and repeatedly branch to innervate the body.

A

brain
spinal cord

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2
Q

What are Neurons/Nerve cells? (2)

A
  • Functional cell responsible for nervous system signalling
  • Cells specialised for communication
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3
Q

How do neurons function?

A

By sending either:
- Long-distance electrical signals → electrical impulses OR action potentials from part of the body to another
- Short-distance chemical signals

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4
Q

Where is higher-order processing done?

A

Higher-order processing is done in the brain + ganglia (Process nerve impulses as groups of neurons organised in the brain or simpler clusters)

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5
Q

CNS (Central Nervous System) – neurons that carry out ____.
PNS (Peripheral Nervous System) – neurons that carry ____ into and out of the ____.

A

integration
neurons
CNS

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6
Q

Cell body:

A

→ main body, integration centre, organelles including nucleus (DNA) + mitochondria

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7
Q

Dendrites:

A

→ cytoplasmic branched extensions of cell body, receive
information from receptors or other neurons

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8
Q

Axon:

A

→ slender tube of the cell membrane, a small amount of cytoplasm, enclosed in a myelin sheath, is specialised to transmit action potential away from the cell body

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9
Q

Axons are longer than ____.

A

dendrites

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10
Q

Axon Hillock:

A

→ cone-shaped area of the cell body, an area where signals that travel down axon are generated

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11
Q

Axon terminal:

A

→ extensions of axon branches

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12
Q

Presynaptic cells + postsynaptic cells:

A

→ synapse terminal, 100 000 synapses with highly branched dendrites

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13
Q

Presynaptic cell:

A

→ transmitting neuron

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14
Q

Postsynaptic cell:

A

→ receiving neuron, muscle, or gland cell, receive signal
from synaptic terminal of presynaptic cell

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15
Q

Synaptic terminal:

A

→ part of axon branch that forms specialised junction

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16
Q

Synapse:

A

→ branched end of axon/junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter of an electrical coupling

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17
Q

Neurotransmitter:

A

→ a chemical messenger/molecule released form the
the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft and binds to the postsynaptic cell, triggering a response

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18
Q

What is the structure of a neuron?

A
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19
Q

How do neurons function in receiving and transmitting information? (5)

A
  • The cell body houses the organelles + nucleus. The cell body is studded with highly branched extensions called Dendrites (short) which receive signals.
  • Has a single Axon (long) which transmits signals by using pulses of electrical current to transmit information.
  • Axon Hillock is the cone-shaped base of an Axon, site where signals are generated before going down the Axon.
    At the end of an Axon, the Axon branches. Each branched end transmits information to another cell at a junction called a Synapse.
  • The part of each Axon branch that forms this specialized junction is a Synaptic Terminal.
  • Chemical messengers called Neurotransmitters pass information from the transmitting neuron cell to the target cell.
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20
Q

What are Schwann cells?

A
  • Main glial cells* of the PNS which wrap around axons of motor + sensory neurons to form the myelin sheath +
    *Glial cells → function to support neurons
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21
Q

How do you myelinate Schwann cells? (3)

A
  • Wrap around axons of motor + sensory neurons to form myelin sheath
  • Sheath is not continuous
  • Gaps between adjacent Schwann cells = Nodes of Ranvier
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22
Q

What is myelin?

A

Schwann cells produce myelin → Myelin is a lipid-rich (fatty) a substance formed in the central nervous system (CNS) by glial cells called oligodendrocytes, and in the peripheral nervous system (PNS) by Schwann cells.

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23
Q

The myelinated axon can be likened to an electrical wire (the axon) with _____ material (myelin) around it.

A

insulating

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24
Q

What is the function of myelin?

A

Myelin insulates nerve cell axons to increase the speed at which information (encoded as an electrical signal) travels from one nerve cell body to another (as in the CNS) or, for example, from a nerve cell body to a muscle (as in the PNS)

Unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon.

Rather, each myelin sheath insulates the axon over a long section and each axon comprises multiple long myelinated sections separated from each other by short gaps.

Each myelin sheath is formed by the concentric wrapping of an oligodendrocyte or Schwann cell process around the axon.

25
Q

What is demyelination?

A

Demyelination is the loss of the myelin sheath insulating the nerves and is the hallmark of some neurodegenerative autoimmune diseases, including:
- multiple sclerosis (MS),
- acute disseminated encephalomyelitis and
- Guillain–Barré syndrome.

26
Q

What happens when myelin degrades?

A

When myelin degrades → conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. The immune system may play a role in demyelination associated with such diseases.

27
Q

With ___ _____ (MS), the body’s own system of defence, known as the immune system, malfunctions. It sends disease-fighting cells into the central nervous system (CNS) that may destroy the body’s own myelin.

A

multiple sclerosis

28
Q

What is Multiple Sclerosis (MS)?

A
  • An autoimmune condition in which the immune system attacks the CNS leading to demyelination Multiple sclerosis (MS) is a demyelinating disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This damage disrupts the ability of parts of the nervous system to communicate, resulting in a range of signs and symptoms, including physical, mental, and
    sometimes psychiatric problems.
  • While the cause is not clear, the underlying mechanism is thought to be either destruction by the immune system or failure of the myelin-producing cells. There is no known cure for multiple sclerosis.
29
Q

Multiple sclerosis is the most common immune-mediated disorder affecting the CNS

MS involves the loss of ______, the cells responsible for creating and maintaining a fatty layer—known as the myelin sheath—which helps the neurons carry electrical signals (action potentials).

  • results in a ____ or complete loss of myelin and, as the disease advances, the breakdown of the axons of neurons.
A

oligodendrocytes
thinning

30
Q

When the myelin is lost → a neuron can no longer effectively ____ electrical signals.

A

conduct

31
Q

What is remyelination?

A

A repair process, called re-myelination, takes place in the early phases of the disease, but the oligodendrocytes are unable to completely rebuild the cell’s myelin
sheath.

  • Repeated attacks lead to successively less effective remyelination until a scar-like plaque is built up around the damaged axons → These scars are the origin of the symptoms.
32
Q

How is MS diagnosed?

A

MS is typically diagnosed based on the presenting signs and symptoms, in combination with supporting medical imaging and laboratory testing.

It can be difficult to confirm, especially early on since the signs and symptoms may be similar to those of other medical problems.
- Clinical data alone may be sufficient for a diagnosis of MS if an individual has had separate episodes of neurological symptoms characteristic of the disease.

33
Q

In those who seek medical attention after only one attack, another testing is needed for the diagnosis:
The most commonly used diagnostic tools are: (3)

A

neuroimaging
analysis of cerebrospinal fluid
evoked potentials

Magnetic resonance imaging of the brain and spine may show areas of demyelination (lesions or plaques).

34
Q

_____ can be administered intravenously as a contrast agent to highlight active plaques and, by elimination,
demonstrate the existence of historical lesions not associated with symptoms at the moment of the evaluation.

A

Gadolinium

35
Q

Testing of CSF obtained from a ___ ____ can provide evidence of chronic inflammation in the CNS

  • The CSF is tested for _____ bands of IgG on electrophoresis, which are inflammation markers found in 75–85% of people with MS.
A

lumbar puncture
oligoclonal

36
Q

The nervous system in MS may respond less actively to stimulation of the optic nerve and sensory nerves due to _______ of such pathways → These brain responses can be examined using ____ and sensory-evoked potentials.

A

demyelination
visual

37
Q

What are the white spots?

A

The white spots are lesions showing damaged neurons undergoing demyelination.

38
Q

Columns or lanes labelled “C” for ____ ____have horizontal red stripes or bands of antibodies except for specimen 4 (seeing numbering on the bottom).
Columns labelled “S,” for serum or blood, lack bands. Only bands are present in spinal fluid and not blood
count towards oligoclonal bands to diagnose MS. Of note, oligoclonal bands can be present in other neurological conditions.

A

cerebrospinal fluid

39
Q

What is the cure for MS?

A

There is no cure for multiple sclerosis. Treatment typically focuses on speeding recovery from attacks, slowing the progression of the disease and managing MS symptoms. Some people have such mild symptoms that no treatment is necessary.

40
Q

What are some treatments for MS attacks? (2)

A
  • Corticosteroids, such as oral prednisone and intravenous
    methylprednisolone, are prescribed to reduce nerve inflammation. Side effects may include insomnia, increased blood pressure, increased blood glucose levels, mood swings and fluid retention.
  • Plasma exchange (plasmapheresis). The liquid portion of part of your blood (plasma) is removed and separated from your blood cells. The blood cells are then mixed with a protein solution (albumin) and put back into your body. Plasma exchange may be used if your symptoms are new, severe and haven’t responded to steroids
41
Q

What is a nerve?

A

Nerve = group of neurons bunched together OR group of axons

42
Q

Spinal cord nerve fibres are each wrapped in a protective sheath known as the ______.

bundled together into groups known as _____ each surrounded by a protective sheath of connective tissue known as the _____.

several fascicles may be bundled together
with a blood supply and fatty tissue within
another sheath, the _____.

A

endoneurium
fascicles
perineurium
epineurium

43
Q

Nerve Impulse Mechanism: (8)

A

(1) The sensory neuron has endings in the skin that sense a stimulus such as water temperature. The strength of the signal that starts here is dependent on the strength of the stimulus.

(2) The graded potential from the sensory endings, if strong enough, will initiate an action potential at the initial segment of the axon (which is immediately adjacent to the sensory endings in the skin).

(3) The axon of the peripheral sensory neuron enters the spinal cord and contacts another neuron in the grey matter. The contact is a synapse where another graded potential is caused by the release of a chemical signal from the axon terminals.

(4) An action potential is initiated at the initial segment of this neuron and travels up the sensory pathway to a region of the brain called the thalamus. Another synapse passes the information along to the next neuron.

(5) The sensory pathway ends when the signal reaches the cerebral cortex.

(6) After integration with neurons in other parts of the cerebral cortex, a motor command is sent from the precentral gyrus of the frontal cortex.

(7) The upper motor neuron sends an action potential down to the spinal cord. The target of the upper motor neuron is the dendrites of the lower motor neuron in the grey matter of the spinal cord.

(8) The axon of the lower motor neuron emerges from the spinal cord in a nerve and connects to a muscle through a neuromuscular junction to cause contraction of the target muscle

44
Q

3 stages of information processing → occur quickly at 150 m/sec or 540 km/h

A
  1. Sensory input → gathering of information
  2. Integration → processing of information
  3. Motor output → response to information transmitted to muscle or gland
45
Q

What type of neurons make up the nervous system?

A
46
Q

Afferent neurons:

A

convey information from tissues and organs into CNS and are also called sensory neurons.

47
Q

Interneurons:

A

connect neurons within specific regions of the CNS.

48
Q

Efferent neurons:

A

transmit signals from CNS to the effector cells and are also
called motor neurons.

49
Q

Afferent and efferent also refer generally to ____ that, respectively, bring information to or send information from the brain

A

neurons

50
Q

What type of glial cells make up the nervous system? (4)

A
51
Q

What are microglia? (3)

A
  • Microglia are specialized macrophages capable of
    phagocytosis that protects neurons of the central
    nervous system.
  • These cells are found in all regions of the brain
    and spinal cord → CNS
  • They are mobile within the brain and multiply when the brain is damaged. In a healthy brain, microglia direct the immune response to brain damage and play an important role in the inflammation that accompanies the damage.
52
Q
  • Many diseases and disorders are associated with deficient microglia, such as: (3)
A

Alzheimer’s disease
Parkinson’s disease
ALS

53
Q

Microglia are :
* _______ cells
* Remove cellular ____
* Not ___ in origin

A

Phagocytic
debris
in

54
Q

What are astrocytes? (3)

A
  • The most abundant type of macroglia cell in the CNS, astrocytes (also called astroglia) have numerous projections that link neurons to their blood supply while forming the blood-brain barrier.
  • They regulate the external chemical environment of neurons by removing excess potassium ions, and recycling neurotransmitters released during synaptic transmission.
  • Astrocytes may regulate vasoconstriction and vasodilation by producing substances such as arachidonic acid, whose metabolites are vasoactive.
55
Q

What is the structure of astrocytes? (3)

A
  • Structural support → provide neurons with glucose
  • Regulate the composition of extracellular fluid in CNS
  • Regulate extracellular ion concentrations
56
Q

What are oligodendrocytes? (3)

A
  • Oligodendrocytes are cells that coat axons in the CNS with their cell membrane, forming a specialized membrane differentiation called myelin, producing the myelin sheath.
    The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently.
  • Form myelin sheaths around neurons in CNS
  • Allow for rapid conduction of action potentials in small diameter axon in PNS – Schwann cells
57
Q

What are ependymal cells?

A

Ependymal cells, also named ependymocytes → line the spinal cord and the ventricular system of the brain.
These cells are involved in the creation and secretion of cerebrospinal fluid (CSF) and beat their cilia to help circulate the CSF and make up the blood-CSF barrier.

58
Q

Ependymal cells
* They are also thought to act as ____ stem cells
* Line _____ of brain; produce cerebrospinal fluid (CSF)
* Have _____ for circulation of CSF

A

neural
ventricles
cilia

MBBCh 1- APES1001A (38 decks)

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