Chapter 2: CELLS OF THE NERVOUS SYSTEM Flashcards
What are the main difficulties with studying brain cells?
- very small size (0.01-0.05mm)
- consistency
- uniform cream color
What is the widely used technique for the study of cells of the nervous system?
-Nissl staining: used to study the morphology and pathology of the nervous system, cytoarchitecture in the CNS.
Who are the two pioneers in this field?
- Camillo Golgi
- Santiago Ramon y Cajal
What does the neuron doctrine state?
That the nervous system is composed of nerve cells each of which is a structural unit in contact with other units but not in continuity.
What are the two basic divisions of the nervous system ?
- CNS (Central Nervous System): brain and spinal cord, communicates to the rest of the body through nerves.
- PNS (Peripheral Nervous System)
What is the definition of a neuron and and what are it’s four structures?
- Information-processing and information-transmitting element of the nervous system
- 4 structures: cell body (soma). dendrites, axon, terminal buttons
Three types of neurons and functions?
- Sensory, motor, inter.
1. Sensory gather information from the environment
2. Motor is responsible for movement and contraction of muscles.
3. Inter neurons connect motor and sensory.
Different types of structures of neurons
- Multipolar: A multipolar neuron is a type of neuron that possesses a single axon and many dendrites.
- Bipolar: a neuron with only two extensions—an axon and a dendrite—that run from opposite sides of the cell body.
- Unipolar: A unipolar neuron is a neuron in which only one process, called a neurite, extends from the cell body.
How is the soma of a neuron structured?
- Contains the nucleus
- Shape varies in different kinds of neurons
What is the function and structure of dendrites?
- treelike structure attached to the soma
- receives information transmitted across synapse
- Neurons “converse” with one another, and dendrites are recipients of these messages
What are the functions of dendritic spines?
- Increase the number of possible contact points between neurons
- Major substrate for brain plasticity
- In many mental illnesses or intellectual disabilities, dendritic spine pathologies were found.
How does communication proceed in the synapse?
- message sent from the terminal button, situated on the presynaptic cell.
- message received on the membrane of the postsynaptic cell.
What does the axon do?
- Carries information from the cell body to the terminal button
- The basic message it carries is called an action potential. It runs on the surface of the axon.(it is both electrical and chemical)
What system in the action potential allows messages to travel within the axon?
- axoplasmic transport: propels substances along the “tracks” that run inside the length of the axon.
- anterograde transport: from the soma to the terminal buttons
- retrograde transport: from the terminal buttons back to the soma.
What does the myelin sheath do?
surrounds axons and insulates them
What do the terminal buttons do?
- secrete a chemical called neurotransmitters
- forms the synapse with other neurons
Structure and function of the membrane?
- boundary of the neuron
- different kinds of proteins embedded in the membrane, which each serve different functions
Structure and function of cytoskeleton?
- matrix of strands of proteins
- gives the neuron its shape
- Thickest of the 3 kinds of protein strands: microtubules (structural support for the neuron, form the “tracks” for axoplasmic transport
Structure and function of the cytoplasm?
- fills the space surrounding the membrane, including the soma
- contains organelles: one of them is the mitochondria, which produces a chemical called adenosine triphosphate (ATP)
Structure and function of the nucleus?
- contains chromosomes which are long strands of DNA (deoxyribonucleic acid)
- chromosomes: contain recipes for making protein
- inside chromosome, gene: contains recipes for individual protein
Function of proteins?
-serve as enzymes: direct the chemical processes of a cell by controlling chemical reactions
What are the neurons surrounded of?
- a cellular membrane
- made of a self-organizing phospholipid bilayer
What are the different numbers of neurites a neuron can have?
- Anaxonic: no axon
- Unipolar: single neurite
- Bipolar: two neurite
- Multipolar: more than two neurites
What different morphology can neurons have?
- 2 shapes: stellate cells(star-shaped), and pyramidal cells (pyramid-shaped)
- spiny or aspinous.
What are the neuron that command voluntary movement?
-Cholinergic: releases acetycholine at synapses
Function of adrenaline?
Fight or flight
Function of noradrenaline?
concentration
Function of dopamine?
pleasure
Function of serotonin?
Mood
Function of Gaba?
calming
Fucntion of acetylcholine?
Learning
Function of Glutamate?
Memory
Function of endorphins?
Euphoria
Why do neurons need supporting cells?
- very high rate of metabolism but no means of storing nutrients
- cells support and protect neurons: they are important to our existence
What is the overall function of glia?
-surround neurons, hold them in place, control their supply of nutrients.
What do astrocytes do?
- type of glial cell (most numerous)
- Fill spaces between neurons
- Provide physical support to neurons and cleans up debris within the brain
- Regulate chemical content of extracellular space
What is the function of the blood-brain barrier?
- selectively permeable
- It is produced by the cells in walls of brain’s capillaries
- Regulates the composition of extracellular fluid which allows transmission of messages from place to place.
What is the region in the blood-brain barrier where the barrier is weak?
- Area postrema
- Can detect toxic substances entering the blood and induce vomiting.
What are ependymal cells?
- type of glia
- line brain ventricles
- produce CSF (cerebrosipnal fluid cushions the brain and can remove metabolic waste)
- role in directing developmental cell migration
- protect against viral infections
- May have stem/progenitor cell properties following injury
What are microglia and what are their functions?
- smallest of the glial cells
- engulf and break down dead and dying neurons
- serve as part of immune system, protect brain from invading microorganisms
- Respond to pathogens and injury
- But can be modified by systemic infection or inflammation: risk of neurodegenerative disease.
What type of glial cells are responsible for myelinating the neurons?
- Oligodentrocytes in the CNS : one cell can insulate many axon segments
- Schwann cells in the PNS: one cell insulate a single axon segment: the entire cell surrounds the axon
Why is myelination important?
- conduction and propagation of nerve impulses
- segments with no myelin sheath: node of Ranvier.
- Hallmark of multiple sclerosis: disrupted myelin and oligodentrocytes
