week 2 Flashcards
are the fundamental units of the brain and nervous system, the cells responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between.
Neurons
-Neurons that carry sensory impulse from sensory organs to the central nervous system are known as ______
-They are located in the dorsal root ganglion of the spinal cord.
-It is unipolar
-Comprises of a short axon
-An adult has an average of 10 million sensory -nerves in the body
Found in eyes, skin, ears, tongue and nose
SENSORY NEURONS
-A neuron that carries motor impulses from the central nervous system to specific effectors is known as ______.
-They are located in the ventral root ganglion of the spinal nerve
-It is multipolar
-Comprises of a long axon
-Half million of motor neurons are found in the body
-Found in muscles and glands
MOTOR NEURONS
-are the finger-like cells present on the end of a neuron. They are short, branching fibres extending from the cell body of the nerve cell. This fibre increases the surface area available for receiving incoming information. Dendrites are the receiving or input portions of a neuron.
-The greater the surface area of a _____, the more information it can receive
-The shape of _______ varies enormously from one neuron to another and can even vary from one time to another for a given neuron
Dendrites
(also called the soma) is the spherical part of a neuron that houses the nucleus. It also contains all the other organelles essential for cell survival and plays a key role in supplying energy, proteins, and other materials to the axon
-Contains the nucleus, ribosomes, mitochondria, and other structures found in most cells.
Much of the metabolic work of the neuron occurs here.
______ of neurons range in diameter from 0.005 mm to 0.1 mm in mammals and up to a full millimeter in certain invertebrates.
Like the dendrites, the cell body is covered with synapses on its surface in many neurons
Cell Body or the SOMA
- It is also called nerve fibre, portion of a nerve cell (neuron) that carries nerve impulses away from the cell body.
- A neuron typically has one axon that connects it with other neurons or with muscle or gland cells.
- Some ____ may be quite long, reaching, for example, from the spinal cord down to a toe
Axon
_____ is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances.
This ______ allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down.
Myelin Sheath
These are periodic gaps in the insulating sheath (myelin) on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses.
These interruptions in the myelin covering were first discovered in 1878 by French histologist and pathologist Louis-Antoine Ranvier, who described the nodes as constrictions.
Nodes of Ranvier
They are the nerve fibers responsible for bringing sensory information from the outside world into the brain.
Afferent neurons
They are the nerve fibers responsible for carrying signals from the brain to the peripheral nervous system in order to initiate an action. In other words, they are the neurons that tell your body to perform an action, such as removing your hand from a hot pan
Efferent neurons
-The term glia, derived from a Greek word meaning “glue,” reflects early investigators’ idea that glia were like glue that held the neurons together
-_____ are smaller but also more numerous than neurons. Overall, they occupy about the same volume
-the other major components of the nervous system, do not transmit information over long distances as neurons do, although they do exchange chemicals with adjacent neurons.
Glia Cells/ Neuroglia
Types of Glia
Astrocytes
Microglia
Oligodendrocytes
Schwann Cells
Radial glia
-Star-shaped ______ wrap around the presynaptic terminals of a group of functionally related axons, they take up chemicals released by axons and then releasing them back to axons, an _______ helps synchronize the activity of the axons, enabling them to send messages in waves.
-remove waste material created when neurons die and control the amount of blood flow to each brain area
-during periods of heightened activity in some brain area, _____ dilate the blood vessels to bring more nutrients into that area
- they release chemicals that modify the activity of neighboring neurons
-They are an important contributor to information processing.
Astrocytes
very small cells, also remove waste material as well as viruses, fungi, and other microorganisms.
They function like part of the immune system
Microglia
guide the migration of neurons and their axons and dendrites during embryonic evelopment
Radial Glia
