Intro Neurophysiology Flashcards
What are the two subdivisions of the mammalian nervous system?
CNS
PNS
What are the division in the CNS
Brain and the spinal cord
What are the important components of the PNS
Receptors, Nerves and the Ganglia
What is the role of the brain in the CNS
Receives, processes sensory information, initiates responses, stores memories, generates thought and emotion
What is the role of the spinal cord in the CNS
Conducts signals to and from the brain, controls reflex activities (highway)
What are the further division of the PNS
Sensory division AFFERENT and Motor division (EFFERENT)
SAME
What do sensory neurons do
AFFERENT: They bring information to the CNS from receptors in peripheral tissues and organs
What do the motor neurons do?
Carries commands from the CNS to PNS
What is the further subsdivisions of the Sensory division
Visceral Sensory Division and Somatic Sensory Division
Visceral Sensory divison
provides information about internal organs (PNS to the CNS)
- visceral receptors and sensory neurons
Somatic sensory division
Provides information about position, touch, pressure, pain and temperature (PNS to the CNS)
- somatic receptors and sensory neurons
Somatic Motor divison
Controls skeletal muscle contraction (voluntary control)
Commands from the CNS to the PNS
Visceral motor divison
Provide autonomic regulation of smooth muscle, cardiac muscle glands, adipose tissue (involuntary control)
Sympathetic - Fight or Flight
Parasympathetic - Rest and Digest
What are the two categories of cells?
Neurons and Neuroglia
What are the major functional unit of the NS
Neurons (nerve cell) - Specialized in information processing
What happens when neurons reach maturity
They can no longer divide
Neurons are composed by
- Dendrites
- Cell body, soma or pericaryon
- Axon
- Axon hillcock or trigger zone
- Presynaptic terminal
- Myelin sheath
- Node of ranvier
Dentrites
Receiving area of the cell membrane
Cell body, soma, Pericaryon
life support center - contains organelles
Axon
information-carrying extension of the cell membrane
Passes messages away from the cell body to other neurons, muscles, glands.
Presynaptic terminal
end of the axon - transmit information
Axon Hillock
Axon origin: originates th AP
Myelin sheath
enhances the speed of information transfer
AP is jumping from node to node
Node of Ranvier
Gaps in the insulating myelin sheath
Terminal branches of axon
Form junctions with other cells
How do neurons communicate
through synapses
Are all axons Myelinated?
Only larger axons are myelinated smaller ones are not because their APs are so tiny
Where is the myelinated sheath?
Wrapped around the axon in a spiral fashion
Where do the myelinated sheath originate from and are part of?
Schwann cells in the PNS
and oligodendrocytes in the CNS
What is the myelin sheath a modification of?
The plasma membrane
What are the periodic interruptions of the myelin sheath
Node of Ranvier and are critical for the function of Myelin
What does myelin sheath facilitate
** is an electrical insulator
conduction - however its function of facilitating conduction has no exact analongy in electrical circuitry
What kind of conduction is in the myelin sheath?
Saltatory - AP jumps from node to node
When is depolarization much more rapid
When the myelin sheath is presented
What is the conduction velocity in myelinated fibers related to?
Proportional to the diameter therefore larger axons have longer internodes and faster conductions
What is the conduction velocity in unmyelinated fibers related to?
proportional to the square root
What are the classifications of the neurons?
Neurons can be classified by structure and and function
What are the structure of the neurons
Multipolar
Bipolar
Pseudo- unipolar
Unipolar
What is the structure multipolar neurons
Most common type of neuron
- 1 axon and many dendrites; the length and arrangement vary considerably
What is the structure of bipolar neurons
Have two process; 1 axon and 1 dendrite
Pseudo-unipolar
Have a single stem process that bifurcates to form 2 processes - one goes to the PNS and one goes to the CNS
What structure and function do sensory or afferent neurons have?
Most of them are pseudo-unipolar
Send information from receptors in sensory organs toward the brain/spinal cord
What structure and function do interneurons or associated neurons have?
They are usually multipolar or bipolar neurons
Found in the brain and spinal cord (CNS) connecting motor and sensory neurons
What structure and function do motor or efferent neurons have?
They are multipolar
Send information from the brain/spinal cord to muscle/glands (effector organs)
What are neuroglia?
Small neurons that do not have axons and dendrites
They fill in the spaces in the NS not occupied by blood vessels or neurons
More numerous than neurons in the nervous tissue
Have the capacity to divide
Do not produce AP
Do not participate in synaptic interactions and electrical signaling
Why are neuroglia cells important?
production of myelin sheaths of axons
modulate growth of of neurons (developing or damaged)
Buffer extracellular concentrations of potassium. and neurotransmitters
formation of contracts between neurons
immune response of the nervous system
What gilia cells are located in the CNS
- Microglial cells
- Astrocytes
- Oligodendrocytes
- Ependymal cells
What gilia cells are located in the PNS
Schwann cells which produce myelin
What are microglia cells
brain defence cells - protect against injury + infection + role in developing the brain (destroy the synapses that are unnecessary)
They are also know to release NO (nitric oxide) antiviral substance
What cells act as macrophages
Microglia cells - phagocytosis to clear debris
What are Astrocytes?
Star-shaped cells with numerous long cell processes - 50% of the cell population
What is Astrocytes role?
Provide structural and metabolic support for neurons, forms the inner and outer glial limiting membrane of the CNS.
Helps elongate axons and dendrites
Participate in the repair process following tissue injury
What cell maintains the neurons environment and how?
Astrocytes
Controls the level of neurotransmitters around the synapse and controls the concentration of important ions
Provides metabolic support
Modulates how neurons communicate
What are Oligodendrocytes
Support to the axon of neurons in the CNS, contains numerous processes that extend to adjacent axons to form myelin
What is the reason the brain has white matter?
Myelin
Where are the ependymal cells?
cover ventricle, central canal + choroid plexus
What do the ependymal cells create?
Involved in creating CSF
What are schwann cells
Provide support to axon in the PNS, they are similar to the oligondendrocytes
How are the Schwann cells arranged?
side by side on along the axons
