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ANAT241 > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

Example of physiological muscle hypertrophy

A

Skeletal muscle changes with exercise

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2
Q

Example of pathological muscle hypertrophy

A

Cardiac muscle hypertrophy

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3
Q

Example of hyperplasia and hypertrophy

A

Increased size of the myometrium during pregnancy

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4
Q

Organisation of the nervous system

A
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5
Q

Anatomy of a neuron

A

Neurons all have the same basic strucuture but they vary in size and shape

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6
Q

3 main neuron shapes

A

Multi = One axon multiple dendrites
Bipolar = one axon one dendrite
Unipolar = common stem connecting axon and dentrite to cell body

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7
Q

Cellular features of a neauron

A
  • large nucleus - reflecting metabolic demand
  • many mitochondria
  • lots of ER, particularly in larger neurons - can be found in dendrites but NOT AXONS
  • numerous neurofilamnts together with microtubules make up the cytoskeleton

Synapses are found at dendrites and also cell body

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8
Q

Two types of matter the CNS is macroscopically divided into

A
  • grey matter (neuron cell bodies, dendrites and axons)
  • white matter (axons; many myelinated
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9
Q

What makes up the grey matter

A
  • neuron cell bodies
  • dendrites
  • some axons
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10
Q

What makes up white matter

A
  • axons; many myelinated
  • lots of lipid in it which is why it is white - myelination is lipid
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11
Q

Does grey matter contain myelin?

A

No

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12
Q

What supports the CNS

A

Glial cells

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13
Q

4 glial support cells of the CNS

A
  • oligodendrocytes
  • astrocytes
  • microglia
  • ependymal cells
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14
Q

What are oligodendrocyte

A

CNS equivalent of Schwann cell myelinated axons

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15
Q

What do astrocytes do?

A
  • provide mechanical support (also form part of the blood brain barrier)
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16
Q

What are ependymal cells?

A

Ciliated cuboidal epithelial cells which line the cavities of the brain and spinal cord

  • epithelial cells
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17
Q

What are microglia

A

Specialised immunological cells of the CNS

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18
Q

Structure of peripheral nerves

A
  • a nerve consists of one or more bundles of nerves fibres called fascicles
  • axons inside the fascicles are surrounded by collagenous support tissue called endoneurium
  • the fascicles are enclosed in dense callagenous tissue called perineurium
  • the fascicles are bound together by loose collagenous tissue called epineurium
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19
Q
A

Schwann cells provide support to the PNS

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20
Q

What are PNS axons enveloped by and what does it provide?

A

PNS axons are an eloped by Schwann cells, providing structural and metabolic support

21
Q

What is the factor that results in different degrees of evolopedness

A

Small diameter fibres are non-myelinated
Large diameter fibres are myelinated

22
Q

Non-myelinated nerve features

A

Small diameter axons of the autonomic system and small pain fibres are simple enveloped by the cytoplasm of Schwann Cells
- no myelination

23
Q

Features of myelinated nerves

A
  • the axon is invaginated into the Schwann cell cytoplasm
  • the outer membrane of the Schwann cell fuses to form a mesaxon
  • the mesaxon rotates around the axon - wrapping the axon in concentric layers of membrane = myelin sheath
24
Q

Histology of myelin

A
25
Q

Do Shawna cells cover the entire axon?

A

Each Swann cell only covers a part of an axon

26
Q

What are the gaps where axons are not myelinated called

A

Nodes of ranvier

27
Q

What are nodes of ranvier ?

A

Gaps where axons are not myelinated

28
Q

What are nodes of ranvier important for?

A

Important in signal conduction along axon

29
Q

Are nodes of ranvier also found in the CNS?

A

Yes - gaos in oligodendrocyte myelination

30
Q

What creates the resting membrane potential?

A

The fluid inside the cell has an excess of negative chargers and the fluid outside the cell has an excess of positive chargers.

  • this action potential allows information to travel along the axon
31
Q

Non-myelinated vs myelinated

A
  • non-myelinated nerves are slower to conduct an action potential
  • action potential of myelinated nerves jumps quickly between nodes of ranvier

MYELINATION SPEEDS UP CONDUCTION VELOCITY
- can localise channels at the nodes - allows the dollarisation / information to jump

32
Q

What is multiple sclerosis?

A

Autoimmune nervous system disease where immune system attacks the myelin of the CNS

33
Q

What does multiple sclerosis do?

A

Slows down or blocks messages between the brain and the body

Causes:
- visual disturbances
- muscle weakness
- trouble with coordination and balance numbness, prickling- pins and needles
- thinking and memory problems

34
Q

Cause of multiples sclerosis and cure

A

Don’t know the cause
- no cure

35
Q

What is Guillain-Barré syndrome ?

A

Autoimmune nervous system disease where immune system attacks the myelin of the PNS

36
Q

What does Guillain-Barré syndrome cause?

A

Tingling in hands and feet

Progressing weakness of limbs and respiratory muscles

Effects on autonomic nervous system lead to altered heart rate and blood pressure

Cause unknown but usually associated with earlier infection

37
Q

What are synapses

A

Specialised intercellular junctions which link neurons to eachother and to muscles

  • pre-synaptic terminus
  • post-synaptic terminus
  • synaptic cleft with neurotransmitter released
38
Q

Process of synaptic transmisssion at chemical synapses

A
  • propergating axon terminates at the terminal bouton
  • AP from propagating axon elicits release of neurotransmitter from synaptic vesicles into synaptic cleft
  • neurotransmitter diffuses across synaptic cleft and stimulates receptor on the post-synaptic membrane
  • this stimulates a response, usually an action potential, in the effector cell
  • neurotransmitters include: Noradreanaine, glutamate, dopamine, ACh, seratonin
39
Q

Neurotransmitter disorders

A

Neurotransmitters synthesised via biochemical pathways

  • loss of enzyme GTP cyclohydrolase 1 leads to deficiency in several neurotransmitters

GTPCH deficiency:
- early onset (4-5 months)
- intellectual disability
- convulsions
- irritability
- hypersalvation
- difficulty breathing

Treatment with neurotransmitter precursors

Other deficiencies recapitulate effects

40
Q

What is the neuromuscular junction

A

The synapse between motor neurons and muscle fibre

41
Q

How many muscle fibres can one neuron innervate

A

Thousands of

One motor neuron can divide into many branches each ending in a neuromuscular junction - one neuron may innervate thousands of muscle fibres

42
Q

What is a motor unit

A

Motor neural and all connected skeletal muscle fibres

43
Q

Lots of fibres in a motor unit =
Fewer fibres in a motor unit =

A

Power
Endurance

44
Q

Release of ACh at the neruomuscualr junction (motor end plate)

A

AP comes down the axon
ACh is released form synaptic vesicles
Binds to nicotinic ion channels that cause membrane depolarisation
Secondary synaptic cleft caused by folding (more surface area for more channels)
NMJ occupies a recess on the muscle surface: sole plate

45
Q

Muscle fibre action potential

A
46
Q

What is myasthenia gravis

A

Autoimmune disease - body produces antibodies to nicotinic receptor.

Binding of ACh is therefore blocked and muscle activation is inhibited

Most commonly affected muscles: eyes, face, those associated with swollaing

Acetylcholinesterase inhitiors alleviate symptoms

Immune suppressors can also help

47
Q

Botox shit

A
48
Q

Process of injecting Botox to elimitate skin wrinkles

A

Botulinum toxin A regulates ACh release from nerve terminals and thus selectively inhibits the underlying muscles ability to contract

Existing lines and furrows are thus smoothed

Toxin cleaves the protein involved in release of ACh from vesicle

ANAT241 (29 decks)

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