(Wk2) The Nervous System Flashcards
What are the 4 organs involved in the nervous system?
Brain, Spinal Cord, Peripheral Nerves and the Sense Organs
Name the 2 divisions of the nervous system.
CNS- Central Nervous System is composed of the brain and spinal cord.
PNS- Peripheral Nervous System is composed of nerves, sense organs and receptors (eyes, ears, touch, pain..etc)
What are the functions of the CNS?
To process and coordinate sensory data, motor commands and higher functions of the brain (such as intelligence and emotions).
What are the functions of the PNS?
To connect the nervous system with other systems, deliver sensory information to the CNS and carry motor commands to peripheral tissues and effectors.
Describe Neural Tissue.
Is made up of 2 types of cells: Neurones and Neruoglia (glial cells).
And 2 types of matter: Grey and White matter.
What are Neurones?
Cells that send and receive signals.
What are Glial Cells (Neuroglia)?
Cells that support and protect neurons.
What is grey matter?
Cell bodies and unmyelinated neurones
What is white matter?
Axons of myelinated neurones.
Describe the structure of a Neurone.
Has Dendrites, Perikaryon and Nucleus (Cell Body), Axon and Telodendria.
What are the 4 Anatomical Classifications of Neurones?
-Anaxonic Neuron (have more than 2 proccesses; all dendrites)
-Bipolar Neuron (have 2 processes; separated by the cell body)
-Unipolar Neuron (single, elongated process; with cell body located off to the side)
-Multipolar Neuron (have more than 2 processes; single axon and multiple dendrites).
Describe the neuroglia of the CNS.
Neuroglia in the CNS includes: Ependymal Cells, Astrocytes, Oligodendrocytes and Microglia.
Describe Astrocytes
Star-shaped branching glial cells. They maintain the brain blood barrier and preserve the chemical environment by recycling ions and neurotransmitters.
Describe Ependymal Cells
They line ventricles (brain) and central canal (spine); are involved in the production of cerebrospinal fluid.
Describe Oligodendrocytes
Myelinate axons in the CNS and provide an overall structural framework.
Describe Microglia
Remove cell debris, wastes and pathogens via phagocytosis.
Describe the neuroglia of the PNS
Neuroglia in the PNS includes: Schwann Cells and Satellite Cells.
Describe Schwann Cells
Myelinate axons in the PNS.
Describe Satellite Cells
Regulate nutrient and neurotransmitter levels around neurons in ganglia.
What is the function of dendrites in the structure of a motor neuron?
Thin extensions of the cell body that carry impulses received from neighbouring neurones to the cell body.
What does the cell body consist of in the structure of a motor neuron?
Nucleus, Mitochondria and many ribosomes.
What is the function of axon in the structure of a motor neuron?
Long cytoplasmic extension that carries impulses away from the cell body. It is covered in Schwann Cells, that support and surround the neurones.
What is the function of myelin sheath in the structure of a motor neuron?
The layer of Schwann Cells. Acts as an electrical insulator to speed up the rate of transmission.
What is the function of nodes of ranvier in the structure of a motor neuron?
These are the gaps in the myelin sheath. They occur between adjacent schwann cells.
What is the resting membrane potential?
Is the difference in charge across the neuronal membrane when the neurone is at rest.
It is a result of different concentrations inside and outside the cell.
The resting membrane potential of a nerve cell is about -70mV.
By which 3 factors is the resting potential maintained through?
1) The membrane containing many sodium-potassium pumps.
2) Potassium ion channels making the membrane permeable to potassium ions.
3) Anion (-) concentrations are higher inside the neuron.
How is the resting potential created?
By the unequal distribution of ions, such as Potassium and Sodium, across the cell membrane.
What is the electrochemical gradient?
The balance of forces acting upon an ionic species.
Na+: both electrical and chemical gradients attract Na+ into the cell.
K+: the chemical (out) and electrical (in) gradients oppose one another.
What is the equilibrium potential of K+?
-90mV
What is the equilibrium potential of Na+?
+70mV
Describe passive (leak) channels
-Always partially open
-Contribute to the resting membrane potential.
Describe gated (active) channels
-Open/Close in response to specific stimuli
-Exist in 3 possible states; closed but capable of opening, open, closed and incapable of opening.
There are 3 types of gated channels: chemically regulated, voltage regulated and mechanically regulated.
What is a graded potential?
A temporary, localised change in the resting potential, caused by a stimulus.
What is an action potential?
Rapid sequence of changes in the voltage across a membrane.
What is a synapse?
Site of transmission of electric nerve impulses between 2 neurons
What are the main 2 types of synapses?
Electrical and Chemical.
