Environment of the Brain (Neurones & Glia) Flashcards Preview

Semester 4 - Neuroanatomy & Neuropsychiatry > Environment of the Brain (Neurones & Glia) > Flashcards

Flashcards in Environment of the Brain (Neurones & Glia) Deck (37):
1

What is the general function of neurones?

sense changes and communicate with one another

2

What is the general function of glial cells?

support, nourish and insulate neurones

 

remove waste

3

What are the 3 primary types of glial cells?

Astrocytes

Oligodendrocytes

Microglia

4

What is the most abundant type of glial cell in the CNS?

Astrocytes

A image thumb
5

What are 3 roles of the astrocytes?

Provide Nutrition for Neurones
(glucose-lactate shuttle)

 

Remove Neurotransmitters
 

Maintain Ionic Environment
(K+ buffering)

6

Outline the two sources of energy available for neurons to utilise

glucose directly from the blood
(taken up into brain ECF, then transported into neurone for conversion to ATP)

 

glucose is stored in astrocytes as glycogen that can be released when necessary

(astrocyte glucogen > glucose > pyruvate > lactate > shuttled from astrocyte into neurone > converted back to pyruvate > converted to ATP)

A image thumb
7

How do astrocytes help to limit the effects of neurotransmitters?

re-uptake neurotransmitter from synapse

 

astrocytes uptake glutamate from the synapse, convert it to glutamine and deliver it back to the presynaptic terminal to be converted back to glutamate and further released as a neurotransmitter

A image thumb
8

Neuronal depolarisation causes efflux of K+ to restore the RMP, how is this counteracted in the brain-ECF to prevent elevated K+ levels?

astrocytes uptake excess K+ via:

 

K+ Channels

Na+/K+/2Cl- Channels

Na+/K+ ATPase

A image thumb
9

What is the difference between Oligodendrocytes and Schwann cells?

Oligodendrocytes

CNS - can myelinate multiple neurones

 

Schwann Cells

PNS - can only myelinate single neurones

A image thumb
10

What structure is damaged in multiple sclerosis??

myelin sheaths attacked by auto-antibodies

 

commonly affects the CNS (optic nerve)

 

deposition of plaques/scar tissue

11

What is the function of the microglia of the CNS?

brains main defence system

immunocompetent cells - capable of phagocytosing foerign material

A image thumb
12

What is the function of the blood brain barrier and how is it formed?

limits diffusion of substance from blood to brain ECF - allows a specific environment around the brain to be maintained

 

formed by tight junctions between brain capillaries - these are promoted by the astrocyte foot processes

A image thumb
13

How is the environment around the brain maintained, utilising the tight junctions formed by the capillaries?

specific transporters allow movement of substances across the basement membrane of the brain capillary endothelium

A image thumb
14

The CNS is isolated from the immune system to prevent injury?

 

TRUE / FALSE

FALSE

 

the CNS is not isolated, rather specialised, to allow it to limit the pro-inflammatory T cell response as the rigid skull would not tolerate volume expansion

15

What are the 4 main sections of a neurone?

Cell Soma

Dendrites

Axon

Terminals

A image thumb
16

Outline how neurotransmitters are released from the pre-synmaptic vesicles

  1. Action potential travels down pre-synpatic axon to terminal
  2. Depolarisation causes Ca2+ entry through voltage-gated Ca2+ channels
  3. Ca2+ binds to synaptotagmin
  4. Vesicle brought close to membrane
  5. Snare complex make a fusion pore
  6. Transmitter released through pore
  7. Neurotransmitter binds to post-synaptic receptor

A image thumb
17

What are the 3 major groups of neurotransmitters in the CNS?

Amino Acids
(e.g. glutamate, GABA)

 

 

Biogenic Amines
(e.g. acetylcholine, noradrenaline, dopaminem serotonin)

 

Peptides
(substance p, somatostatin, NPY)

18

What are the main excitatory synapses in the CNS?

Glutaminergic Synapses

19

What is the difference between the inotropic and metabotropic receptors, which are subtypes of the glutamate receptors? 

Inotropic
have an integral ligand-gated ion channel

 

Metabotropic
linkted to a GPCR

20

What electrochemical effect is caused when glutamate binds to an inotropic glutamate receptor on a neuronal cell?

activation causes depolarisation of the neurone

 

AMPA receptors = Na+/K+

NMDA Receptors = Na+/K+ and Ca2+ 

 

opening channels causes an influx of Na+ and efflux of K+

21

What effects does glutamate have on the excitability of neurones?

Increases Excitation

22

Why does binding of glutamate to AMPA and NMDA receptors cause slightly differing responses?

AMPA Receptor
only ligand gated channels - allowing rapid depolarisation due to Na2+ influx

 

NMDA Receptor

ligand and voltage gated channels - voltage gated portion is opened by AMPA stimulation, which causes the Mg2+ blocking the pore to be removed and allow Na+ and Ca2+ influx - glutamate is also required to open the ligand gated portion 

A image thumb
23

What is the molecular basis for long term potentiation in neurones and what is thought to be the biological benfit of such effects?

activation of NMDA receptors allows Ca2+ influx which can then activate second messengers

 

second messengers cause up-regulation of AMPA receptors and cause an increased conductance of ions > generating larger action potentials

 

believed to be essential for the formation of memories and learning

A image thumb
24

What risk is posed to neurones if excess glutamate is present around synapses?

excess NMDA stimulation

 

excess calcium entry into post synaptic terminals

 

Ca2+ is TOXIC to neurones

25

What is the main inhibitory neurotransmitter in the:

 

Brain

 

Brainstem and Spinal Cord

Brain

GABA

 

Brainstem & Spinal Cord

Glycine

26

Which ion channel opens when GABA and Glycine bind to receptors in neurones, and what is the effect?

ligand gated Cl- channels

 

influx of Cl- into cell

 

hyperpolarisation of cell

A image thumb
27

What does EPSP and IPSP mean?

Excitatory Post-Synaptic Potential

 

Inhibitory Post-Synaptic Potential

28

How do barbituates and benzodiazepines function?

enhance the response of GABAreceptors when GABA binds
(modulate GABAA receptor)

 

barbituates = increase the duration of opening

benzodiazepines = increase freuqncy of opening

A image thumb
29

How can inhibitory neurones be useful in the spinal cord?

released from interneurones which allow relaxation of the opposite muscle group when testing relfexes

A image thumb
30

What are the target receptors for acetylcholine in the CNS and what is their effect?

Q image thumb

nicotinic and muscarinic receptors in cortex and hippocampus

 

mainly excitatory

 

involved in arousal, learning and memory

31

In which area of the brain do cholinergic neurones originate and what pathology is associated with destruction of these neurones? 

Nucleus Basalis
(basal forebrain)

 

Alzheimer's Diseaese

A image thumb
32

In which area of the brain do the largest number of dopaminergic neurones arise?

Substantia Nigra

 

(terminating in the corpus striatum)

A image thumb
33

What function in the brain is provided by the dopaminergic nigrostriatal pathway?

Motor Control

34

What conditions can be caused by a deficit / excess of dopamine in the brain?

Dopamine Deficit

Parkinson's disease - loss of neurones in substantia nigra

 

Dopamine Excess

Schizophrenia - could be secondary to amphetamines as they stimulate dopamine release

35

Why is does the treatment of Parkinson's disease involve the administration of L-DOPA rather than dopamine, as well as the co-administration of Carbidopa?

doapmine cannot cross blood brain barrier

 

L-DOPA can cross blood brain barrier

 

carbidopa prevents peripheral conversaion of L-DOPA to dopamine, which could lead to treatment failure and side effects from peripeharl dopamine receptor stimulation

A image thumb
36

What is the function of a the locus coeruleus in the brainstem?

release of noradrenaline throughout cortex, cerebellum and hypothalamus

 

noradrenaline release increases wakefulness

A image thumb
37

Where are the cell bodies of the serotonin (5-HT) releasing neurones located within the CNS and what is their function?

within upper medulla and pons

(often called raphe nuclei)

 

Functions include modulation of:

  • sleep, wakefulness and mood
  • perception of pain

A image thumb