Chapter 4: Neuroscience Flashcards
What is neuroimaging?
techniques that allow for the stuyding of brain activity by obtaining visual images in awake humans
What are the two most useful neruoimaging methods?
PET scan: enable the detection of the uptake of certain molecules so that brain areas with increased activity can be identified
fMRI scan: allows for the detection of changes in blood flow, a presumed indicator of changes in the acidity of nerouns
What is a neruon?
a nerve cell
What do neurones have?
A cell body; filled with cytoplasm with a nucleus; dendrites; extend like brahcnes from the cell body to collect INPUTS from other nerusons, can have many dendrites; axons; also extend from cell body, function to carry information AWAY from the cell body toward other neurones, with a specialized region at the end called the axon terminal
What are the different types of neurones?
Sensory; in the skin, musles that respond to pressure, temp, or pain; Motor, that stimulate our muscle cells into action, and Interneurons that contact these two types; all neurones are covered by a membrane, all nerouns are capable of communication with other cells by producing and sending electrical signals
What are glia?
Non-neuronal cells
What do they do?
buffer the neurones from the rest of the body, control the nutrient supply to neurones, and destroy and removed diseased and dead neurones
How do nerouns work?
they send messages to one another bia electrochemical actions/ cause an electrical signal to be generated/ sudden electoral change of a neurones axon causes it to a release a neurotransmitter
What are the nerve cells surrounded by
The nerve cells are surrounded by an extracelluar fluid that has ions/ there are also ions inside the neruon which gives it an electrical charge even when it is resting
What is the resting charge called?
Resting potential and it is negative b.c fluid INSIDE the nueron is more negative then the fluid OUTSIDE the ncell
What are ion channels?
neruons membrane is selectively permeable/ ion channels only allow passage of certain ions into and out of the cell/ they open and close depiing on the info received from other nerusons
What are the key ions in determining the resting potential?
positively charged sodium ions NA+, and potassium K+ and negatively charged chloride CL- ion
When the neurone is at rest, which ions are in higher concentration and where are they?
postive sodium ions, and they are in higher concentration outside the cell
What is this unequal distribution of ions on each side of the cell membrane called?
The concentration gradient
How is the resting charge maintained
By the sodium potassium pump
How does the sodium potassium pump work?
it uses energy to hold the reading potential at a negative charge by continuously pumping Na+ out of the axon, enhancing Na+ for K+; pumps push out 3 sodiums and only put in 2 potassium ions
When does the concentration gradient change?
when an electrical charge increases the permeability of the membrane to Na+, which allows Na+ ions to go out of cell
What is the Action Potential?
A sudden postitive change in the electrical charge of a neurones axon, when the AP has been generated the neruon “fires”; the AP occurs when EXCITATROY signals outweigh the number of INHIBITORY sign as and each a certain threshold
What is the definition of a threshold?
the point at which the relative excitiarty influence of other neurons succeeds in causing a neruon to initiate an action potential
What happens during an Action Poential?
Ion channels that allow the passage of Na+ open, this lets Na+ (high concentrationoutside the axon) to rush through the Na+ channels and into the axon; influx of postiv ions shifts electrical charge of axon from positive to negative, when the peak of the action potential reachers a membrane charge of 50 mV, the sodium channels close
What has this caused?
Neighbouring sodium chanels to open and the action potential action potential sweeps down the axon to the neruon
What happens when the sodium channels close in an axon section?
Potassum channels open, and potassium ions exit the cell, restoring the negative charge within that area of the cell
What are the neurones insulted by and what does it do?
Myelin sheath which is made from spepcialed glial cells, that facilitate he movement of an AP down the axon
What are Nodes of Ranvier?
Exposed regions on the axon that are exposed to extracellular fluid
What is saltatory conduction?
It is when the action potential jumps from node to node
What is the refractory period?
After the neurone fires it cannot fire again for a short time
What is the Absoulte refractory period?
Immediately following an AP, the axon is completely unable to fire no matter how stron gthe stimulus to the nueron
What is the Reletive refractory period?
Happens a bit later on, the cel can fire if it is given a stung enough stimulus, threshold for spiking is high
What are neurones separated by?
Synapeses; spaces between the axon terminal of one cell and the dendrite of another cell which neurones communicate
What is needed to facilitate communication across the synapees?
Neruttransmitters