Nervous System Flashcards
What is a neuron?
Specialised cell with cell bodies containing a nucleus and long extentions or fibers that transmit signals.
Basic parts of the neuron
A cell body and cell extensions called dendrites and axons
What is the cell body
The region of the neuron around the nucleus that is responsible for producing substances that are necessary for the nerve cell to live and carry out its functions
What is an axon?
A single long cell extension that often makes distant connections.
May give out branches which often split off and right angles and usually have a myelin covering.
What are nerves?
Bundles of neurons that give off message signals called nerve impulses
What is a dendrite?
A cell extension that is usually much smaller than an axon, has no myelin covering and is specialised to recieve impulses from sensory cells or from axons of other neurons.
What is the CNS
Central Nervous System - consisting of brain and spinal cord
What is PNS
Peripheral Nervous System - consisting of nerves that run to and from the CNS
Note on - Sensory Neurons
Receive information froma sensory receptor (special structures that detect changes in the environment).
Most have one long axon bringing messages from particular receptors
Cell bodies lie near the CNS
Note on - Interneurons
Located within the CNS - integrate incoming information with out going messages.
Usually have a highly branched system of dendrites able to receieve input from many different neurons at once
Axons may not be myelinated.
Note on - Motor Neurons
Transmit commands away from central nervous system to the muscles and glands.
One long axon, usually branched at the end, bringing messages to a muscle or gland
What are Neuroglial cells and what are CNS glial cells and PNS glial cells
-Companion cells that provide support, protectionand nutritional stability to the neuron.
-CNS glial cells - Microglia, Ependymal cells, Astrocytes, Oligodendrocytes
-PNS glial cells - Satellite cells, Schwann cells
Function of Microglia
- monitor health and perform defence functions for neurons.
-differentiate to become a type of macrophage to phagocytose debris and microorganisms
Function of Ependymal cells
-line the central cavities of the brain and spinal cord and help circulate cerebrospinal fluid.
Function of Astrocytes
-regulate the chemical environment around the neurons and exchanges between neurons and capillaries
Function of Oligodendrocytes
Wrap around neuron fibres, forming myelin sheath
Function of Satellite Cells
Multifunctional especially during disease.
Found surronding neuron cell bodies within ganglia
Function of Schwann Cells
Found wrapped around and insulating axons of sensory and motor neurons forming a myelin sheath.
What are the Nodes of Ranvier?
Uninsulated spots that occur at regular intervals on an axon.
-These nodes and mylein sheath create conditions that speed the nerve impulses as it is conducted along surface of axon
Functions of neurons:
To transmit info:
-From the environment to the spinal cord and brain
-From one cell to another within the CNS
-From brain and spinal cord to other parts of the body
Nerve cells transmit this infor in form of nerve impulses
When at rest, what is the charge of the cytoplasm and why?
Approx -65 millivolts
Means that the insde of the cell is negatively charged (greater conc of K+ inside axon) relative to extracellular fluid along the outside of the membrane (greater conc of Na+ outside an axon)
Which ions play a principle role in the development of electrical potential along the membrane of the neuron?
Sodium (Na+) and Potassium ions (K+)