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PHRM 100 – APPP > APPP 03: Gross Anatomy of the CNS – Spinal Cord and CNS Protection > Flashcards

APPP 03: Gross Anatomy of the CNS – Spinal Cord and CNS Protection Flashcards

1
Q

What are the 2 structures of the central nervous system?

A
  • brain
  • spinal cord
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2
Q

Describe the structure of the spinal cord.

A
  • continuous with the medulla of the brainstem
  • segments – 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
  • grey matter – shape of an H with a dorsal-ventral orientation
  • white matter (myelinated axons) – surrounding area
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3
Q

What does the spinal cord do?

A

large-diameter and small-diameter sensory neuron fibres enter through the dorsal horn and feed into axons of motor neurons involved in rapid, involuntary movements (reflex arc), and signal to cortex

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4
Q

What is the reflex arc?

A
  • incoming sensory signals from the body (afferent sensory nerve fibres) synapse at the posterior/dorsal horn with interneurons found in the intermediate grey
  • interneurons signal to efferent motor nerve fibres in the anterior horn to stimulate muscle movement
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5
Q

Describe the pathway of afferent nerves.

A

propagates information toward the CNS (coming in)

  • activation of pain receptor
  • AP travels through dorsal root ganglion nerve fibre
  • synapse at posterior horn/dorsal horn (PH)
  • action on afferent nerves leading to actions at specific sites in the brain
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6
Q

Describe the pathway of efferent nerves.

A

propagate information away from CNS to a muscle or gland (relay signals going out)

  • efferent nerves from cortex signal to anterior horn
  • motor movements
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7
Q

How does the spinal cord link to the autonomic system?

A

intermediate grey matter contains autonomic neurons with axons that leave through ventral roots

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8
Q

Describe the structure of the skull.

A
  • 22 bones
  • cranial bones enclose and protect the brain – frontal, temporal, occipital, parietal, sphenoid, and ethmoid
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9
Q

What is the spine protected by?

A

vertebrae

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10
Q

What are meninges?

A

form a major part of the mechanical suspension of the CNS – necessary to keep it from self-destructing

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11
Q

What are the 3 layers of meninges?

A
  • dura mater
  • arachnoid
  • pia mater
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12
Q

What is the dura mater?

A

thick connective tissue membrane

  • below skull
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13
Q

What is the arachnoid?

A

thinner collagenous membrane

  • cellular layer
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14
Q

What is the pia mater?

A

thinner collagenous membrane

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15
Q

How do the three layers of meninges connect to each other?

A
  • dura connects the skull to the arachnoid layer
  • arachnoid connects to the pia mater cell layer by delicate strands of connective tissue (arachnoid trabeculae) – suspends the CNS in its bath of cerebrospinal fluid
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16
Q

What stabilizes the CNS during head movement?

A

partial flotation of the CNS in subarachnoid CSF, in combination with mechanical suspension

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17
Q

What is cerebral spinal fluid (CSF)?

A
  • contains nutrients
  • formed by filtration of blood
  • enters the venous circulation through arachnoid villi
  • around 150 ml coats the brain
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18
Q

What are arachnoid villi?

A

outpouchings that poke through holes in the walls of the venous system

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19
Q

What do arachnoid villi do?

A

act like valves

  • when CSF pressure is higher than venous, CSF moves into the venous system
  • in reverse, villi snap shut and venous fluid does not enter subarachnoid space – this imbalance can lead to intracranial pressure
20
Q

What is an epidural hematoma?

A

bleeding occurs between the dura mater and the skull

21
Q

How do epidural hematomas occur?

A

skull fracture causes a blood vessel (that runs through dura mater) to rupture, resulting in epidural bleeding

22
Q

What can epidural hematomas lead to?

A

increased pressure on, and damage to, brain tissues

23
Q

What are signs and symptoms of epidural hematomas?

A
  • severe headache
  • nausea and vomiting
  • slurred speech
24
Q

How does a stroke occur?

A

spontaneous rupture of blood vessel, resulting in subarachnoid bleeding

  • buildup of blood can cause pressure on the brain
25
Q

What are the symptoms of a stroke?

A

similar to an epidural hematoma

  • severe headache
  • nausea and vomiting
  • slurred speech
26
Q

What is the blood brain barrier (BBB)?

A

protective functional separation of the circulating blood from the CNS

27
Q

What is the role of the BBB?

A

limit the penetration of substances

  • keep toxins and pathogens out – including drugs
  • facilitates the select transport of molecules
28
Q

Describe arachnoid mater.

A

impermeable barrier to the CNS

  • cell are joined by tight junctions
29
Q

Describe pia mater meninges.

A

impermeable and joined by tight junctions

30
Q

What are astrocytes?

A

brain glial cell type that lines the surface of the brain

31
Q

What are the 4 layers of the BBB?

A
  • endothelial cell layer
  • pericyte layer
  • protecting basement membrane
  • glial barrier formed by astrocyte endfeet
32
Q

What is the pericyte layer?

A

cell layer that lines around 80% of the capillary layer

33
Q

What is the role of the pericyte layer of the BBB?

A
  • physical role is to stabilize the endothelial layer
  • regulation of BBB permeability
34
Q

What is the role of the glial barrier formed by astrocyte endfeet of the BBB?

A

(astrocytes interact with blood vessels with their endfeet)

  • regulate dilation and constriction of microvessels to control blood flow
35
Q

What do both the pericyte layer and the glial barrier formed by astrocyte endfeet contribute to?

A

contributes to the maintenance and regulation of endothelial cell tight junctions (length, width, and complexity)

36
Q

What is the role of the endothelial cell layer of the BBB?

A

has specific transport systems that permit the supply of nutrients, ions, and bioactive molecules

  • diffusion of CO2 and O2 and lipid-soluble (small nonpolar) molecules (transcellular) or small water soluble (paracellular)
  • active transport – ie. glucose
  • receptor mediated (ie. insulin) and adsorptive transcytosis (albumin)
37
Q

What is the key to proper BBB function?

A

maintenance and regulation of endothelial cell tight junctions

38
Q

What does transport of drugs into the BBB often require?

A

requires the drug to engage specific transport mechanisms

ie. L-DOPA (precursor to dopamine) uses an amino acid transporter

39
Q

How do we reduce uptake of drugs in the brain?

A

create more polar compounds

  • ie. 2nd generation (modified) antihistamines cause less drowsiness
40
Q

What are the 3 types of glia/support cells in the CNS?

A
  • astrocyte – blood flow, K+ house keeper
  • oligodendrocyte – myelinate
  • microglia – phagocyte
41
Q

What do astrocytes do?

A

support or protection

  • role in BBB
  • provide nutrients to nerve cells
  • control the chemical composition of fluids around nerve cells, enabling them to thrive
42
Q

What do oligodendrocytes do?

A

make myelin

43
Q

What is myelin?

A

a fatty substance that insulates nerve axons and speeds the conduction of impulses along nerve fibres

44
Q

What do microglia do?

A

help protect the brain against infection and help remove debris from dead cells

  • ‘macrophages’ of the brain
45
Q

What has microglia activation been implicated in?

A

in the inflammatory alterations observed in severe neurodegenerative disease

  • Alzheimer’s disease (AD)
  • Parkinson’s disease (PD)
  • Huntington disease (HD)
  • multiple sclerosis (MS)
  • amyotrophic lateral sclerosis (ALS)
46
Q

What do these neurodegenerative diseases have in common?

A

share pathological characteristics

  • abnormal protein aggregation
  • failure in protein degradation pathways
  • impaired axonal transport

PHRM 100 – APPP (22 decks)

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