3.1 - Nerve cells ✓ Flashcards
What is the role of the nervous system?
The role of the nervous system is to receive and process information from sense organs and bring about responses to the information received.
What are neurons?
Neurons are the basic structural and functional units of the nervous system
What are the two main parts of the nervous system?
-Central nervous system (CNS)
-Peripheral nervous system (PNS)
What does the central nervous system consist of?
It consists of the brain and spinal cord.
What do all neurons consist of?
They all consist of a cell body, dendrites and the axon.
What is the cell body and what is its function?
It is a part of the neuron that contains the nucleus and is responsible for controlling the functioning of the cell.
Describe the structure and the function of dendrite
Dendrite are fairly short extensions of the cytoplasm of the cell body. They carry messages , or nerve impulses, into the cell body.
Describe the structure and the function of an axon
-The axon is often a single, long extension of the cytoplasm.
-At the end, the axon divides into many small branches called axon terminals.
-Its function is to carry nerve impulses away from the cell body
Describe the structure a myelin sheath
Myelin sheaths is a layer of fatty material
Define myelinated fibre
A nerve fibre that has a myelin sheath.
Define unmyelinated sheath
A nerve fibre that has no myelin sheath.
Define nerve fibre
A nerve fibre is a projection from a nerve cell with its associated coverings; usually refers to an axon.
What forms myelin sheath?
Schwann cells
What are the gaps in the myelin sheaths called?
nodes of Ranvier
What are the 3 main functions of a myelin sheath?
-Acts as an insulator
-Protects the axon from damage
-It speeds up the movement of nerve impulses along the axon.
What structure surrounds the myelin sheath in a Schwann cell?
The neurolemma
What is the function of the neurolemma?
It helps in the repair of injured fibres.
What cells produce the myelin sheath in the brain and spinal cord?
Oligodendrocytes
What colour do areas with myelinated fibres appear and what are they called?
They appear white and are called white matter
What is the colour and name of areas made up of cell bodies and unmyelinated fibres?
They appear grey and are called grey matter
Why do areas with myelin appear white?
Because the fatty nature of the myelin gives them a white appearance
How are nerve impulses passed from neuron to neuron?
Nerve impulses are passed where the axon terminal of one neuron joins with a dendrite or cell body of another neuron.
Define synapse
Synapse is the junction where the axon terminal of one neuron joins with the dendrite or cell body of another neuron.
Do neurons physically touch at the synapse?
no, there is a small gap between them
How are the massages carried across the gap at the synapse?
Messages are carried by the movement of chemicals called neurotransmitters
What is the synapse called when an axon meets a skeletal muscle cell?
The neuromuscular junction
What are the three functioning types of neurons?
-Sensory neurons
-Motor neurons
-Interneurons
What do sensory neurons do?
They carry messages from receptors in the sense organs, or skin, to the central nervous system.
What are other names for sensory neurons?
Afferent or receptor neurons
What do motor neurons do?
They carry messages from the central neuron system to the effectors (muscle and glands).
What are other names for motor neurons?
Efferent or effector neurons
Where are interneurons located and their function?
They are located in the central nervous system and they link sensory and motor neurons
What are other names for interneurons?
-Association neurons
-Connector neurons
-Relay neurons
How are neurons classified by structure?
They are classified based on the number of extension from the cell body
What are the 4 main structures of the neuron?
-Multipolar
-Unipolar
-Bipolar
-Pseudounipolar
What is the structure of multipolar neurons?
Multipolar neurons have one axon and multiple dendrites.
What is the most common neuron structure?
Multipolar
Where are multipolar neurons found?
They are found in the brain and spinal cord and in motor neurons.
What is the function of multipolar neurons?
They carry messages to skeletal muscles
What is the structure of a bipolar neuron?
They have one axon and dendrite.
Where are bipolar neurons found in the body?
They are found in ears, eyes and nose
What is the function of bipolar neurons?
They take impulses from receptor cells to other neurons
What is the structure of a unipolar neuron?
They just have an axon extention
Where are unipolar neurons found?
Found in insects
What is the structure of a pseudounipolar neuron?
They have a single axon that separates into two extensions, one connecting to dendrites and the other ending in axon terminals
Where are pseudounipolar neurons found?
Typically found in mose sensory neurons
What is the function of pseudounipolar neurons?
They carry messages to the spinal cord
Define nerve fibre
Any long extension of cytoplasm of a nerve cell (although the term usually refers to an axon)
Define nerve
Nerves are bundles of nerve fibres held together by connective tissue.
