6. Basic Neuroscience Flashcards
Briefly describe communication by nervous system and the benefits
Neuron -> nerve impulse -> neurotransmitter -> target cells
Faster signalling
Neuron smallest functional unit in body
Briefly describe endocrine system and benefits?
Endocrine cells -> hormone in bloodstream -> target cells
Small amount of hormone needed for whole body
Describe the prototypical neuron?
Neurons are highly polaried, very different one end to other, made up of axon, soma (cell body) and dendrites
What are the two major cell types in the nervous system?
Neurons and Glia
Describe the axon?
Gap in the myelin = node (of ranvier)
Myelin sheath on axon = white electrical insulator
Describe the glia?
Glial cell not quite as polarised
Outnumber neurons by 10:1
May mediate some signalling in brain
Primary role is to support neurons
Can divide unlike neurons
Also known as neuroglia
Name the CNS glial cells and PNS glial cells?
CNS glial cells: astrocytes (astroglia), oligodendrocytes, ependymal (make csf) and microglia (immune function)
PNS glial cells: Schwann cells
Describe oligodendrocytes/schwann cells and their function?
Make myelin from cholesterol and myelinate axons of neurons
Oligodendrocytes=Many branches/axons=CNS
Schwann cells=Single axon=PNS
What is the support for the nervous system?
There is no internal connective tissue for support, the supporting cells are all Glia.
What is the grey matter?
Grey matter = nerve cell bodies
Outside of the brain e.g. cortex and basal nuclei and inner part of the spinal cord
What is white matter?
White matter = axons and myelin
Inner part of the brain and outer part of the spinal cord
White is from fatty tissue in myelin
What are the types of neuron?
Unipolar (Psuedo)
Bipolar
Multipolar
Which direction do signals travel along a neuron?
Dendrites receive
Cell body integrates
Synapse Transmits
What is the role of axons?
Specialised for transmission of information
What is the role of dendrites?
Specialised for receipt of information
What similarities and differences are there between neurons and other cells?
Similarities:
- cell body with cytosol and organelles including a nuclus
- cell membrane (plasmalemma)
Uniquie(ish):
- can’t reproduce
- can trigger action potentials (excitable cells)
What other cells to nerve cells communicate with?
Nerve cell -> nerve cell
Nerve cell innovates muscle
Nerve cell innovates glands
Movement of charges ions across cell membranes depends on what?
Diffusion and electricity
Which way do charged ions want to move?
From areas of high to low concentrations
What charge to charged ions move towards?
Charged ions move to areas of opposite charge
How can ions be kept outside of inside the cell against their concentration gradients?
Channels and pumps that can be made to stay closed or forced to work
What is voltage/membrane potential?
The difference in charge from different ions outside and inside the cell
Is neuron polarised?
Inside of a neuron is negative compared to outside (polarised) typically -70 or -80 mV
What ions are inside and outside the resting cell?
Sodium Na+ - Positive charge - Outside cell
Protein - Negative charge - Inside cell
PO4 3- - Negative charge - Inside cell
Maintained by sodium-potassium pump
Describe the resting cell membrane?
Polarised
Negative inside (lots of protein)
Positive outside (lots of sodium)
Describe the stimulation phase of an action potential?
Depolarisation
Sodium channels open
Sodium moves in
Reversal of electrical ppotevntial (inside becomes +ve)
Describe the repolarisation phase of an action potential?
Repolarisation
Sodium channels close
Potassium channels open
Potassium moves out
Return of electrical potential inside to -ve
What happens if stimulation is below threshold for action potential?
No action potential
All or nothing
What happens if stimulation is above threshold for action potential?
Fixed size of action potential whether it’s just above threshold or miles above hreshold
What does myelin do?
Myelin does the job of electrical tape - it insulates the axon so the flow of Na+ ionns in the action potential can travel quickly without dissipating out of the cell
What is MS?
Multiple Sclerosis is a disease affecting the myeling. Myelin is attacked by the body’s own immune system and degraded
What does no myelin mean for the action potential?
No myelin means the action potential will move more lowly down the neuron. Many problems in nerve function then happen, depending on the location of myelin attack.
What do you call the neuron before and after the synapse?
Presynaptic neuron
Postsynaptic neuron
Describe a chemical synapse?
Action potential in nerve terminal opens Ca2+ channels
Ca2+ entry causes vesicle fusion and transmitter release
Receptor-channels open, Na+ enters the postsynaptic cell and vesicle recycle
Name some neurotransmitters?
Serotonin
Acetyl choline
Glutamate
Dopamine
GABA
noradrenaline
adrenaline
How are neurons classified?
- ) Sensory (afferent: somatic or visceral) neurons originate from senory receptors to the processor
- ) Motor (efferent: somatic or visceral) neurons conduct signals that originate in the CNS
- ) Interneurons are between sensory and motor neurons
Name 3 problems with neurons that can cause clinical problems?
- Paralysis - damage to the spine means action potentials can’t travel down neurons to/from areas below the damage usually crush or severing of spinal cord
- Stokes and head injuries - regions of cell death in the brain stop signals being generated or interpreted in that area usually cell death due to brain starvation of blood or oxygen
- Alzheimer’s disease - make too much protein, tangles up, means signalling can’t occus
Give examples of neurological exams?
Glasgow coma scale, pupillary light reflexes, tests for normal cranial nerve and midbrain function, muscle tone and strength
Describe glasgow coma scale?
Rapid assessment of level of coma/consciousness especially useful following acute head injuries
Best GCS=15
Comatose GCS < 8
Totally unresponsive = 3
3 categories: eye opening response, best verbal response, best motor response
