Chapter 3: Neuroscience and Behavior 3.1-3.3 Flashcards
Neurons
Cells in the nervous system that communicate with each other to perform information processing tasks
Cell body
Aka the soma is the largest component of the neuron that coordinates the information-processing tasks like protein synthesis, cell production, and metabolism, and keeps the cell alive; enclosed by a porous cell membrane that allows some molecules to flow into and out of the cell
Nucleus
Contained in the cell body and houses chromosomes that contain your DNA
What are the two types of specialized extensions of the cell membrane?
Dendrites and axons
Dendrites
Greek for “tree,” receive information from other neurons and relay it to the cell body
Axon
Carries information to other neurons, muscles, or glands; can be very long
What covers the axon (in many neurons)?
Myelin sheath, an insulating layer of fatty material composed of glial cells (Greek for “glue”)
Glial cells
Support cells found in the nervous system that serve different functions like digesting parts of dead neurons, providing physical and nutritional support for neurons, and forming myelin that insulates the axon and allows it to carry information more efficiently
Demyelinating diseases
E.g. multiple sclerosis, cause the myelin sheath to deteriorate, slowing the communication from one neuron to another which lead to problems like loss of feeling in limbs, partial blindness, difficulties in coordinated movement and cognition
Synapse
Junction or region between the axon of one neuron and the dendrites or cell body of another
What are the three major types of neurons?
Sensory, motor, and interneurons
Sensory neurons
Receive information from the external world and convey this information to the brain via spinal cord; have specialized endings on their dendrites that receive signals for light, sound, touch, taste, and smell
Motor neurons
Carry signals from the spinal cord to the muscles to produce movement, often have long axons that reach to muscles at our extremeties
Interneurons
Connect sensory neurons, motor neurons, or other interneurons; work together in small circuits to perform tasks like identifying the location of a sensory signal and recognizing a familiar face
Purkinje cells
Type of interneuron that carries information from the cerebellum to the rest of the brain and the spinal cord; have dense elaborate dendrites that resemble bushes
Pyramidal cells
Found in the cerebral cortex, have a triangular cell body and a single, long dendrite among many smaller dendrites
Bipolar cells
Type of sensory neuron found in the retinas of the eye, have a single axon and a single dendrite
What are the two stages of electrochemical action in neurons?
Conduction and transmission
Conduction
Movement of an electric signal within neurons, from the dendrites to the cell body, then throughout the axon
Transmission
Movement of a signal from one neuron to another as a result of chemical signalling across the synapse
Resting potential
The difference in electric charge due to varying concentrations of ions between the inside and outside of a neuron’s cell membrane
When is a neuron in resting state?
Inside the neuron’s cell membrane, there is a high concentration of positively charged potassium ions (K+) and larger negatively charged protein ions (A-) compared to outside it. Outside the neuron’s cell membrane, there is a high concentration of positively charged sodium ions (Na+) and negatively charged chloride (Cl-). A- ions are larger and carry a stronger charge than the others so the inside of the cell membrane is negatively charged at -70 millivolts relative to the outside during resting potential.
Action potential
Electric signal that is conducted along the length of a neuron’s axon to a synapse
Explain “the action potential is all or none”
Electric stimulation or shock below the threshold fails to produce an action potential while electric stimulation at or above the threshold always produces the action potential at the same magnitude (value is above zero at +40 millivolts)
How does the total charge inside the axon change from negative to positive?
During resting potential, voltage-gated channels for Na+ ions are closed. When the voltage across the cell body membrane reaches the threshold, sodium-specific channels on the nearby axons open up and Na+ ions rush out into the cell instantaneously, changing the total charge in the axon from negative to positive in less than a millisecond.
What two events restore the negative charge of the resting potential?
(1) Na+ channels are inactivated or in a refractory period for several milliseconds, stopping the flow of Na+ ions (2) Channels specific to K+ ions open, allowing K+ ions inside the cells to exit, then the channels close
Refractory period
The time following an action potential during which a new action potential cannot be initiated; limits the number of times a neuron can fire and keeps the action potential from travelling back to the cell body
Explain the domino effect of action potential across the neuron
When the first voltage channels open, Na+ ions spread and increase the electrical charge down the inside of the axon. When the voltage around adjacent voltage channels reaches the threshold, those open and let in more Na+ ions that spread further. The influx of Na+ ions triggers the nearby channels to open (each reaching +40) and the process repeats down the entire axon.
What is the effect of the myelin sheath on the action potential?
Conduction of the action potential is greatly increased by the presence of a myelin sheath around the axon; prevents electric current from leaking out of it