CNS - Neurocytology Flashcards
List the three Nervous Systems in the human body.
Nervous systems
- Central nervous system (CNS)
– brain and spinal cord.
- Peripheral nervous system (PNS)
– cranial nerves, spinal nerves and ganglia.
- Enteric nervous system (ENS)
Describe the general division of PNS.
Peripheral Nervous System
- Somatic nervous system (SNS):
- The part that is controlled by the free will. - Autonomic nervous system (ANS):
- Not controlled by free will, e.g., heart, glands, bowel.
Usually devided in:
- Sympathic
- Parasymphatic
List the main cells that are included in the Nervous System?
The nervous system consists of several different types of cells:
- Neurons = nerve cells (100 billions)
- Glial cells = supportive function (1000 billions)
- Astrocytes
- Oligodendrocytes
- Schwann cells
- Mikroglia
Explain a fundamental difference between grey and white brain matter.
Brain
- Grey matter
- bodies of nerve cells. - White matter
- nerve fibers.
What is a nerve cell called?
Neuron = nerve cell
A large number of neurons together form a nerve. I.e
N. Ischiadicus (Sciatic nerve)
Explain MR Tractography.
MR Tractography
In neuroscience, tractography is a 3D modeling technique used to visually represent neural tracts using data collected by Difusion Weighted images (DWI). It uses special techniques of magnetic resonance imaging (MRI), and computer-based image analysis. The results are presented in two- and three-dimensional images.
What role does Myelin play in the Nervous Systems?
Myelin
- Insulation – speed up signal transmission
- Oligodendrocytes - CNS
- Schwann cells - PNS
Describe Astrocytes.
Astrocytes
- Most common cell type in CNS
- Blood Brain Barrier
- Provision of nutrients
- Nervous repair
- Astrocytoma grade I-IV
- Astrocytomas are tumors that arise from astrocytes—star-shaped cells that make up the “glue-like” or supportive tissue of the brain.
Explain Oligodendrocytes.
Oligodendrocytes
- Support and insulation
- Myelin of the CNS
- Brain and spinal cord
- Oligodendroglioma
- Oligodendrogliomas (tumors) come from oligodendrocytes, one of the types of cells that make up the supportive, or glial, tissue of the brain. They can be low-grade (grade II) or high-grade (grade III, or anaplastic).
Explain Schwann cells
Schwann cells
- Myelin of PNS
- Acoustic schwannoma
- A vestibular schwannoma (also known as acoustic neuroma, acoustic neurinoma, or acoustic neurilemoma) is a benign, usually slow-growing tumor that develops from the balance and hearing nerves supplying the inner ear. The tumor comes from an overproduction of Schwann cells—the cells that normally wrap around nerve fibers like onion skin to help support and insulate nerves.
Explain Microglia cells.
Microglia
Microglia are a type of glial cell located throughout the brain and spinal cord. Microglia account for 10–15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defense in the central nervous system (CNS).
BBB
Explain Membrane Potential.
Membrane potential
- Current = movement of charged particles
- The direction of current is that of positive charged ions (e.g Na+, K+, Ca2+) moving
- Voltage = difference in electric potential
Explain Resting membrane potential
Resting membrane potential
Over the nerve cell membrane there is an electric potential (same as a battery)
- On the inside of the cell membrane: surplus of negative charges
- On the outside of the cell membrane: surplus of positive charges
This gives a -70 mV difference in potential between the out- och inside of the cell in resting state
How is resting membrane potential achieved?
The concentration of ions within and outside of the nerve cell is different:
Concentration gradients:
- Extracellular the sodium (Na+) concentration is high and the potassium (K+) concentration low
- Intracellular the Na+ concentration is low and the K+ concentration high
Explain Action Potential.
Action potential
“The electric communication between nerve cells”
A small membrane potential exists in the resting neuron (70 mV) due to uneven distribution of ions. Sodium (Na+) at the outside and potassium (K+) at the inside.
A stimulus, e.g., at the synaps, affects the resting membrane potential, depolarize the membrane to a threshold level. Sodium ions will start to rush into the cell through voltage-gated channels because nature wants to “even out” the concentration gradients – depolarization.
This leads to the opening of potassium channels, potassium ions flow out.
Refractory period – ions are actively pumped back.
Describe the velocity of Action Potential.
The velocity of the action potential
Faster in thick than in thin fibers
- Thick myelinated fibres 10-130 m/s (e.g touch, sharp pain)
- Thin myelinated fibers 0.5-2 m/s (e.g. Dull pain)
- Because pain is transmitted in both fast and slow fibers a painful stimuli can be felt as two ”phases” ;
One early (transmitted in fast fibers) and one late
(transmitted in slow fibers)
This is called ”first och second pain”
Give examples when the action potential may be disrupted.
Examples when the action potential is disrupted:
- In multipel Sclerosis (MS) the myelin is damaged =>impairment of transmission
- Local anesthetic (e.g. Xylocain): blockage of Voltage-gated Na+-channels. Pain impulses are not transmitted.
How can compression affect the transmission of the NS?
Compression
Mechanical compression blocks transmission
Exampels:
When the arm ”goes numb”
or
”Saturday night palsy”
(N. radialis)
Give examples of some neurotransmitters.
Neurotransmitter:
- Glutamate
- Dopamine
- Acetylcholine
- GABA
- Serotonine
Give examples of diseases related to synaptic transmission
Diseases and drugs related to synaptic transmission
- Parkinson disease
- Lack of dopamin
- Treatment – increase amount of dopamin
- Schizofrenia
- Excessive amount of dopamin
- Treatment – inhibit dopamin
- Myasthenia Gravis
- Receptors for neurotransmittor Acetylcholine is blocked by antibodies at the neuromuscular junction
Give examples of drugs acting in neuromuscular junction.
Drugs acting in neuromuscular junction
- Curare (arrow poison) blocks ACh-receptors in
muscles causing palsy
- Anesthetic drug Pavulon has the same effect – used
for muscle relaxation in surgey
- Neostigmin stops the degradation of ACH and is used to reverse muscle relaxation efter operation. Can cause cramps - Sarin gas!
- Botulinum toxin (from the bacteria Clostridie Botulinum) – most potent toxin known. Blockage of ” exocytos” av ACh-vesikler – no transmission at the NMJ
- Cocain inhibit the uptake of noradrenalin precursor of adrenaline.
- Depression – lack of serotonin ”tricyclic anti-depressive and ”selective serotonin reuptake inhibitors” (SSRI – e.g. Prozac) inhibit the uptake of serotonin.
Explain Plasticity.
Plasticity
How to develop and adapt to a changing environment and body.
Behavior – result of interaction between genes and environment
Experiences form behavior through lerning and memories
What are the molecular/morfological causes in the CNS for these changes?
Does the memory lie in the synapses?
Research suggest that neurons can learn and remember activity patterns that results in behavior
Aplysia californica
Nobel prize winner year 2000 - Eric Kandel has studied the plasticity in the withdrawal reflex in this snail. Repeated not tissue-damaging stimulation resulted in habituation – a decrease in response after repeated stimulation.
When mechanical stimulation was together with electric Stimulation in tail the withdrawal reflex is ”sensitized”. Sensititation - increase in behavior after repeated stimulation
Explain habituation/sensitiation.
- The number of synapses is up-/downregulated after habituation/sensititation
- The strenght of the synaps - the amount of transmittors released from presynaptic terminal
- Number and type of receptors in the postsynaptic membrane
- The receptors ”probability of activation” and conductivity
Lasting changes found after stimulation protocols are called:
Long Term Potentiation (LTP = When the synapse gets stronger).
Long Term Depression (LTD = When the synapse gets weaker).
These phenomenon are believed to be the neuronal mechanism of memories..!
