Chapter 2- Nerve Cells and Nerve Impulses Flashcards
What did Cajal discover?
the gap between the neurons, previously it was thought that they were all connected
What is the Plasma Membrane?
surface of the cell
What is the nucleus?
where the chromosomes are
What are the Mitochondria?
structure that performs metabolic activities ( provides energy)
What are Ribosomes?
Sites at which the cell synthesizes new protein molecules
What is the Endoplasmic Reticulum?
Network of thin tubes that transports newly synthesized proteins
What is a soma?
Cell body- contains the nucleus, ribosomes, and mitochondria
What are Dendrites?
branching fibers of the neurons, greater the surface area of the dendrite, the more information it can receive “ dendritic spines”
What is an axon?
Thin fiber, neurons information sender
What is the Myelin Sheath?
insulating material coating the axon
What are the Nodes of Ranvier?
interruptions in the myelin sheath
What is the presynaptic terminal
where the axons releases chemicals that cross through the junctions between one neuron and the next
What are motor neurons?
soma in the spinal cord sends and receives excitation through its dendrites and conducts impulses along its axon to a muscle
What is a sensory neuron?
specialized at one end to be highly sensitive to a particular type of stimulation
What is an afferent axon?
brings information into a structure
What is an efferent axon?
carries information away from a structure
What is an Interneuron/ Intrinsic neuron?
when a cell’s dendrites and axon are entirely contained within a single structure
What are Glia?
The other major components of the nervous system
What are Astrocytes?
( glia) star shaped cells that wrap around the presynaptic terminal of a group of functionally related axons. Helping synchronize the activity of the axons, enabling messages to be sent in waves
What are Microglia?
very small cells that remove waste material
What are Oligodendrocytes?
in the brain, specialized type of glia that build the myelin sheath with Schwann cells that are in the periphery of the body
What are Radial Glia?
guide the migrations of neurons and their axons and dendrites during embryonic development
What is Active-Transport?
Protein- mediated process that expends energy to pump chemicals from the blood into the brain
To be able to use Glucose, what vitamin does the body need>
B1- thiamine
What is Korsakoff’s Syndrome?
Caused by prolonged thiamine deficiency, marked by sever memory impairments
What is an electrical gradient?
polarization- the difference in electrical charge between the inside and the outside of the cell. The inside is negatively charged
What is the resting potential?
difference in voltage in a resting neuron
What is the Sodium-Potassium Pump?
A protein complex that repeatedly transports three sodium ions out of the cells, while drawing two potassium ions in.
More sodium outside, more potassium inside
Both the electrical and concentrations gradients encourage sodium to move into the cells, but when the membrane is at rest, the sodium channels are closed
What are actions potentials?
Messages sent by axons, when an axon is at rest… there is a negative potential inside the axon
What is Hyperpolarization?
makes it more negative and less likely to produce an action potential
What is Depolarization?
makes it more likely to produce an action potential ( reduces charge closer to zero)
What is the Threshold of Excitation?
beyond it produces a massive depolarization of the membrane, causes the sodium channels to open and allows sodium ions to flow into the cell
What are voltage-gated channels?
Regulate sodium and potassium - permeability depends on the voltage difference across the membrane
What is the resting potential?
sodium channels are closed and potassium channels are almost closed
What do local anesthetic drugs do?
Novacain and Xylocaine. Attach to the sodium channels of the membrane, preventing sodium ions from entering, which stops actions potentials. The axons can’t transmit the message of “ pain” to your brain
What is the all or none law?
amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiates it, provided the stimulus reaches the threshold
What is the absolute refractory period?
Membrane cannot produce an action potential, regardless of stimulation
What is the relative refractory period?
a stronger than usual stimulus is needed to initiate an action potential
has two mechanisms Sodium channels are closed and potassium is flowing out of the cell at a faster than usual rate
In a motor neuron, where foes an action potential begin?
The axon hillock, a swelling where the axon exits the soma
What is propagation of the action potential?
transmission of an action potential down an axon, just as strong at the end as it was at the beginning
Because the areas that the message “ just passed” are still in their refractory period…
an action potential cannot reinvade the area it just passed
What is Saltatory Conduction?
flow of action potential from one node of Ranvier to another
What is Multiple Sclerosis?
immune system attacks myelin sheaths. If an axon loses its myelin, it still lacks sodium channels in the areas previously covered with myelin. Most Action potentials die out between one node and the next
What are local neurons?
neurons without an axon, do not follow the all or none law, the signal decreases as it travels because it is not being “ reborn” so it gradually decays
What are graded potentials?
membrane potentials that vary in magnitude without following the all or none law
when local neurons are stimulated, it depolarizes or hyperpolarizes in proportion to intensity of stimulus
