Neuron Anatomy Part 1 Flashcards
the physical structural features of a neuron
1) Cell body (soma)
2) Dendrites
3) Axon
4) Presynaptic terminal
Neuron
*Communicating/information processing cells
*‘Primary’
- vital to the life of a cell
-excitation and inhibition
-regulation of sensorimotor and higher functions (cognition and language)
Neurons are Composed of Gray & White Matter
Synapse:
* Point of contact between two neurons
Information-processing cells:
1) Sense changes in the environment and
these sensations, generating behaviors and actions and communicate these changes to other neurons
2) Commands the body’s response to
*essentially electrical responses that send/receive messages
Glial cells
*90% of CNS cells
*Supporting structures/cells of the nervous system
*Association
-protection of nerve cells and tissue repair
*provide insulation, support, structure, protection and nourishment to neighboring neurons
–can be divided into microglia (sanitation) or macroglia^(healing injury/infection)
types of Glial/Neuroglia cells
- Ependymal cells (CNS)
- Astrocytes (CNS)
- Microglia (CNS)
- Oligodendrocytes (CNS)
- Satellite cells (PNS)
- Schwaan Cells (PNS)
Oligodendrocyte (CNS)
Primary Glial Cell
- Small cells
- Provide support to axons of neurons
- Produce fatty substance called myelin
Astrocyte (CNS)
Primary Glial Cell
- Characterized by their star like shape.
- ‘End foot’ connects to capillaries
- Thought to have a role in nutritive function.
Schwann Cell (PNS)
Primary Glial Cell
- Similar to oligodendrocytes in CNS, Schwann cells myelinated neurons in the peripheral nervous system.
what composes gray and white matter of a neuron
- Gray matter = cell body and dendrites
- White matter = axon
cell body (soma)
*process information
* Spherical central part of the neuron
* Also known as the cell body
* Filled with cytoplasm, which contains:
– Cytosol: gel-like substances composed of salt and potassium
– Organelles: sub structures with various functions
* Organelles are protected by the neuronal membrane that prevents substances from the surrounding fluid from entering the cell
* Processing center of the neuron
Dendrites
Carries impulses toward the cell body
- Dendrites receive information
- Some types of neurons have single dendrite others have multiple branches or dendritic tree.
- Dendrites are designed with special receptor sites to receive chemical signals or respond to
sensory inputs. - Receptors: specialized protein
molecules in the dendritic
membrane which receive
neurotransmitters.
Axon
Carries impulses away from the cell body (some covered with myelin)
- Distinct function is action potential
- Axon is made up of white matter
- Neurons contain just 1 axon
- Carries electrical signal away from soma to axon terminal (i.e., sends out information to other cells)
- Can be less than a millimeter to over a meter long
- Variable diameter too: less than 1mm to 25mm in humans
- Diameter is important for the speed of the nerve impulse sent by the axon.
- Thicker = Faster!
Axon Terminals
- Also known as presynaptic terminals
- One component of synapse, or the point of communication between neuron
- Axons separate into a number of small fibers that have terminals
- Each of these axon terminals have a functional connection to another cell
- This is called a synapse
- This is where the axon terminals from one neuron meets the dendrite from another neuron.
Myelin Sheath of Axons
- Axons are covered in a myelin sheath
- Myelin is a multilayered lipid (fat) material that insulates and protects the nerve fiber.
- This insulation prevents the escape of electrical energy during impulse transmission and regulates the speed of nerve impulses.
- The myelin sheath is interrupted by nodes of ranvier (These are important for enhancing the rapid propagation of the electrical impulse (action potential) down the action)
Saltatory Conduction
- Action potential (electrical impulses) jumps from one node of Ranvier to the next, known as saltatory conduction.
- This facilitates rapid conduction inside the axon, up to 120 m/sec.
Myelination
- The production of myelin
*enhance the speed of the conduction of electrical impulses along the neuron, thereby improving the efficiency of neurotransmission and connectivity of the brain - The incomplete or impaired maturation of myelination has implications for the development of sensorimotor functions and speech-language-cognitive skills.
- Damaged myelin in the CNS impairs nerve impulse conduction and is found in demyelinating disorders such as multiple sclerosis.