Brain Cells Flashcards
1
Q
Neurons
A
- Cells of the nervous system that conducts nerve impulses; consisting of an axon and several dendrites
- Electrically active
- Function: information processing
- ~ 85 billion
2
Q
Glial cells
A
- Cells in the nervous system that support and protect neurons:
- regulating the chemical environment
- enhancing electrical signalling of neurons
- removing debris left by dead neurons
- role in brain signalling
- ~85 billion
3
Q
Neuron structure
A
Soma + dendrites + axon
4
Q
Soma
A
- Metabolic centre of the neuron
- Composed of:
- Cytosol: intracellular fluid inside a cell (salty, potassium rich solution)
- Cytoplasm: everything within the cell membrane, including organelles, but excluding the nucleus
- Organelles: same as found in other eukaryotic animal cells
- nucleus
- mitochondria
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- ~20 μm (10-6 m)
5
Q
Mitochondria
A
- Cellular respiration – generates adenosine triphosphate (ATP)
- ATP = energy currency of the cell
6
Q
Cytoskeleton
A
- “Cell skeleton” = cell shape → correct positioning of organelles and racks for in cell transportation
- Consists of:
- Microtubule - 20 nm - tubulin molecule
- Neurofilament - 10 nm
- Microfilament - 5 nm - actin molecule
7
Q
Neuronal membrane
A
- Barrier to enclose the cytoplasm inside the neuron
- Protein composition varies depending on the location (soma, axon, dendrites).
- CRITICAL for the function of neurons – electrical activity of neurons is dependent on the membrane
8
Q
Axon
A
- A tube-like structure that propagates the integrated signal from the axon hillock to specialized endings called axon terminals
- Only found in neurons
- Each neuron has only one axon
- Highly specialized for information transfer (electrical signals) over distances (“electrical cables”)
- Axons can extend < 1mm to 1 m long.
-
Axon hillock: region where the axon originates.
- Integrates signals from multiple synapses and serves as a junction between the cell body and an axon
- The neurofilaments in the axon hillock become clustered together as fascicles.
9
Q
Axon terminal
A
- Region where the axon contacts with other neurons
- Terminal arbor – short branches at the end of the axon
- Synaptic vesicles – that contain important chemicals for communication (neurotransmitters)
- Numerous mitochondria → high energy demand
- Synapse – point of contact between an axon and other neuron
10
Q
Dendrite
A
- Branched projections of a neuron that conduct the impulses received from other neural cells to the cell body
- Dendritic tree – collection of dendrites from a neuron, a branch is called dendritic branch
- “antennas of the neuron” / “receiving ends” → lots of synapses
-
Dendritic spines increase possible synaptic contact sites between neurons.
- Very effective synapses that can quickly change in appearance
- Important for plasticity and learning (new spines can grow, existing spines can become larger or smaller, or disappear)
- Ribosomes can be found in spines → protein synthesis for quick structural change of spines
11
Q
Pyramidal cell
A
12
Q
Purkineje cell
A
13
Q
Spindle-shaped cell
A
14
Q
Classification of neurons
A
- Based on number of neurites (axons and dendrites):
- Unipolar: only 1 neurite is attached to cell body (soma); no dendrite at soma, only axon!
- Bipolar: 2 neurites (1 dendrite + 1 axon) are attached to soma
- Multipolar: many neurites (many dendrites + 1 axon) are attached to soma
- Taking up only a very small amount of information can lead to greater precision → uni and bipolar neurons are most often sensory neurons
- Multipolar neurons can be found in the central nervous system (brain and spinal cord)
- Based on dendrites: classification is often unique to a particular part of the brain
- e.g. stellate cells have a very tight network of dendrites → perfect for interconnection and information exchange between neighbouring neurons; whereas pyramidal cells are perfect for transferring information over long distances (e.g. from brain to spinal cord)
15
Q
Types of neuroglia
A
- Central nervous system
- Ependymal cells
- Oligodendrocytes
- Astrocytes
- Microglia
- Peripheral nervous system
- Satellite cells
- Schwann cells
16
Q
Astrocytes
A
- In the CNS astrocytes provide nutrients to neurons, give synapses structural support, and block toxic substances from entering the brain;
- ”star-like”
- Most numerous glia in the brain
- In the gaps between neurons
- Influence neurite growth
- Regulation of chemical content in extracellular space (potassium K+)
- Restricting spread of neurotransmitters from synaptic cleft
- Active removal of neurotransmitters from synaptic clef
18
Q
Myelinating glia
A
Oligodendrocytes (CNS) and Schwann cells (PNS): insulation of axons by supplying a myelin sheath around axon → increases conduction speed
