Chapter 3 - Biological Foundations of Bahaviour Flashcards
Neurons are the basic building blocks of the nervous system, made up of what three parts? describe them
Cell body/Soma
- contains biochemical structure needed to keep neuron alive
- nucleus carries genetic info that determines how cel will develop and function
Dendrites
- branch like emerging from cell body
- collects messages from other neurons, send them to cell body
Axon
- extends from cell body, conducting electrical impulses to other neurons, muscles or glands
- connects with dendrite branches from other neurons
How many neurons does a human have at birth?
100 billion, loosing 10,000 every day
What are Glial cells
They surround neurons and hold them in place
- made up of fatty tissue
- also manufacture nutrients from myelin sheath, absorb toxins and waste
- guide newly divided neuron to place during brain development
what does the blood-brain barrier do
prevents substances from entering brain
Describe the sate inside and outside of a neuron
- neurons are surrounded by a positively charged liquid environment (Na+)
- inside of the neuron is negative (Cl- and negative protein ions)
- the resting potential across the membrane is -70mV
Describe events leading up to action potential
Action potential (nerve impulse) is a sudden reversal in neuron’s membrane voltage
- depolarization occurs; changes from -70mV to +40
- only occurs if the graded potential reaches action potential threshold, about -55mV (obeys all or none law)
- This change occurs due to ion channels, which open allowing a rushing in of Na+, making the neuron less negative (depolarization)
- Ion channels then close, K+ channels open and the positive ions go back to their respective positions outside the cell
- resting potential is restored
what is the refractory period
time period during which the membrane is not excitable and cannot discharge another
action potential
- occurs immediately after impulse passes
- limits rate at which action potential can be triggered (300 impulses/sec in humans)
What is the Myelin sheath and what is its purpose? Also was are the nodes of ranvier?
- a fatty, whitish insulation layer derived from glial cells that covers axons
- thins out at regular intervals, called the nodes of renvier
- allow for higher conduction speeds along axon and faster transmission time
- prevents loss of signals
what is a polarized neuron
a neuron at resting potential
what is a depolarized neuron
a neuron which sodium channels have opened and Na+ has rushed into the cell making it positive
what is hyperpolarization
a change in a cell’s membrane potential that makes it more negative
When neurons are classified by shape there are three kinds. which are…
Bipolar - an axon and one dendrite extending from the cell body toward opposite poles
Multipolar - multiple dendrites and a single axon.
Unipolar - neurons have one axon (usually the cell body on the side of the axon)
what is an excitatory neuron
Will depolarize postsynaptic membrane (EPSP) making it positive
What is an inhibitory neuron
Hyperpolarizes membrane (IPSP) making it negative
EPSP’s and IPSP’s are additive across space and time
what does this mean
if you were to get two epsp’s you could add them together to get the total effect of both of them
same with ipsps
or if you have an ipsp and epsp that are equal, they will cancel each other out
who discovered synaptic transmission
Otto Loewi
What is a synaptic cleft/ synapse
- neurons don’t touch each other
- tiny space between axon terminals to dendrite of the next neuron
Carrying messages through synapse to excite or inhibit the other neurons evolves what five steps
Synthesis - chemical molecules formed inside neuron
Storage - Molecules stored in synaptic vesicles
Release - Action potential causes vesicle to move to surface of terminal, molecules are releases into fluid-filled space
Binding - molecules cross the space and bind to receptor sites (large protein molecules embedded in the membrane)
Deactivation
whos experiment studied the flexor response and helped discover the synapse?
Sherrington
he suggested that the transmission from neuron to neuron was not electrical but rather chemical
what are neurotransmitters
the chemicals found in synaptic vesicles that travel across synapse during synaptic transmission
The binding of neurotransmitters to receptor sites causes two possible effects which are…
Excitation
- depolarizes next neuron
- makes post-synaptic neuron more likely to fire
- causes sodium to enter postsynaptic neuron
Inhibition
- hyperpolarizes (more negative),
- causes action potential to not occur
- changes the potential from -70mV to -72mV
this makes it more difficult to excite the neuron to the threshold and cause action potential, thus inhibiting neuron
the receptor sites on the postsynaptic membrane will only allow for neurotransmitters what are the right _____ to bind/pass
shape
how are inhibiton and seizures linked
seizures are caused by a lack of inhibition
t or f? some neurons can be both expiatory and inhibitory
True! depends on the type of receptor