Chapter 7 - Nervous System I (Neurons) Flashcards
Afferent (Sensory )Neurons Definition
Neurons carrying messages TO the CNS
*Located in Dorsal Root Ganglion
Efferent (Motor) Neurons Definition
Neurons carrying messages FROM the CNS
*Located in grey matter of spinal cord
(leaves CNS and goes to skeletal muscle)
Dendrites Definition
Projection from cell body that carry messages TO cell body
Axons Definition
Large projection that carry messages AWAY from cell body
Interneuron Definition
Located between sensory and motor neurons , within the CNS
- Integrate and interpret sensory signals
Myelin Definition
Myelin Sheath Definition
Myelinated Neurons Definition
Neurons with axons covering neuroglial cells that contain protein myelin
*Carry messages faster than non-myelinated neurons
Schwann Cells Definition
Form myelin sheaths
*Found in PNS
Oligodendrocytes Definition
Form myelin sheaths
*Found in CNS
Nodes of Ranvier Definition
Spaces on axon between glial cells
Ions Definition
Ion Channels Definition
Action Potential Definition
Sodium ions and Potassium ions crossing cell membrane through Ion channels
- Ion channel designed to only allow certain ions to pass through
Repolarization Definition
Caused by potassium ions leaving axon
*When potassium ions open up and allow K+ OUT of the axon, making the inside negative
(action potential travels down the axon)
Depolarization Definition
Caused by Sodium ions entering the axon
- When sodium ions open and sodium rushes in, making the INSIDE positively charged
Membrane Potential Definition
Difference in charge between inside and outside of neuron
Resting Potential Definition
A neuron not conduction a message
*When a neuron is resting, there is MORE Sodium OUTSIDE cell and MORE Potassium INSIDE cell
*Inside of the cell has a negative charge compared to the outside cell
Sodium Potassium Pump Definition
To maintain a resting membrane , neurons pump Sodium OUT of the cell and Potassium INTO the cellf
(this is active transport = requires ATP)
Restores original conditions of pumping sodium OUT of the cell and potassium back IN
Synapse Definition
Junction between two neurons or between neuron and muscle
Synaptic Cleft Definition
The gap between presynaptic neuron and post-synaptic neuron
Synaptic Vesicles Definition
Small vesicles that are clustered at presynaptic terminals
*Store neurotransmitters and release them by calcium triggered exocytosis
Neurotransmitters Definition
A chemical messenger that the body can’t function without
Acetylcholine Definition
Acts in both PNS and CNS as a neurotransmitter
*Causes voluntary muscles to contract
Central Nervous System (CNS) Definition
Brain and Spinal Cord
Peripheral Nervous System (PNS) Definition
Nervous tissue outside brain and spinal cord
*Sense organs
Neurons Definition
Cells responsible for transmitting messages
Neuroglial Cells Definition
Cells that support the neurons
Microglia Definition
Immune system cells, engluf bacteria and cellular debris
Cell Body Definition
Contains the nucleus, main body of cell
Functions of Myelin Sheaths
- The main benefit of myelin sheaths is that myelinated neurons are able to carry messages faster than non-myelinated neurons
- Myelin sheaths from Schwann cells also help regenerate injured PNS neuron axons
Multiple Sclerosis (MS) Definition
Destruction of Myelin Sheath that surrounds axons in CNS
*Results in : Paralysis , loss of sensation , loss of vision
Refractory Period Definition
Sodium channels inactive for awhile after action potential passess
Transmission across the synaptic cleft
- The action potential gets to the end of the presynaptic axon
- The action potential triggers Ca2+ to enter the presynaptic axon terminal
- The Ca2+ triggers synaptic vesicles located at the axon terminal to merge with the neural membrane Transmission across the synaptic cleft
- The synaptic vesicles release the
neurotransmitters into the synaptic cleft - These neurotransmitters travel across the synaptic cleft to the postsynaptic neuron (or the muscle)
- Neurotransmitter binds to receptors on the postsynaptic neuron (or muscle)
- These receptors are ligand-gated sodium ion channels that allow Na+ to enter the postsynaptic neuron (or muscle) and trigger an action potential in the postsynaptic neuron (or muscle contraction)
- Once the neurotransmitters are released they need to be destroyed or contained quickly or they will continue to stimulate the nerve
Myasthenia Gravis Definition
Autoimmune disease that attacks the acetylcholine receptors, resulting in reduced muscle strength
