Chapter 3 Neural Bases of Behaviour Flashcards
Define neurons
Basic building blocks of the nervous system - The cells that link together the bodies circuitry
What are the three main parts of the neuron?
- cell body
- dendrites
- axon
What is another term for the cell body of the neuron?
soma
Describe the cell body of the neuron
Contains the structure is necessary for the neuron to stay alive and the nucleus contains the genetic information that the neuron needs to function and develop - It also combines and processes incoming information.
Describe the dendrites of the neuron
Branch like fibres that emerge from the cell body that are specialized receiving units That provide input from neighbouring neurons and send the electrical impulse on to the cell body
Describe the axon of the neuron
Conducts electrical impulses away from the cell body to other neurons or muscles or glands
What branches out of the axon?
Axon terminal’s which may connect with other dendrites from other neurons
Describe the structural elements of a neuron
how are neurons supported in their functions?
glial cells
Describe glial cells
- surround neurons and hold them in place
- Manufacture or transport proteins
- Form the myelin sheath around some axons
- Absorb toxins and waste materials that might damage neurons
- Guide neurons to specialized positions during prenatal brain development
- Protects the brain from toxins
What keeps foreign substances from gaining access to the brain?
blood brain barrier - Glial cells and the small gaps in the blood vessels found in the brain
What two important things do neurons do?
- generate electricity
- release chemicals that allow them to communicate with other neurons and with muscles and glands
What are the three basic steps of nerve activation?
- at rest, neuron has a resting electron potiential due to distribution of positively and negatively charged chemicals otuside and inside of cell respectively
- When stimulated a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential, producing an action potential or nerve impulse
- the original distribution of ions is restored and the nueron is again at ret and capable of being activated again
describe ion channels
proteins embedded in the semipermeable neuron membrane that allow the passage of select substances
What creates a nerver impulse?
exhange of ions
Describe ions
electrically charged atoms
What ions are present in the fluid outside the neurons?
Na+ & Cl-
What ions are present inside the neurons?
A- (anions) & K+
Describe the neurons resting potential
An uneven distribution of ions inside and outside of cell that makes the inside more negative due to high concentration of negatively charged proteins interiorly and high concentration of positively charged Na+ exteriorly.
What state is the neuron in at resting potential?
State of polarization
When the neuron is not being stimulated what is the difference in the electrical charge?
-70mV between the interior and the surface of the cell
What maintains the negative interior of the neuron?
sodium-potassium pump - pumps out 3 Na+ for every 2 K+ that comes in
How does the electrical charge change during an action potential?
sodium is pumped into the axon and the charge changes from -70mV to +40mV
How does the action potential move down the length of the neuron?
Once neuron is stimulated, Na+ channels will open up in certain area changing the electrical charge and immediately after they close the K+ channel will open to pump K+ out restoring the resting charge and then adjacent Na+ pumps will open and this cycle will repeat down the length of the axon.
Show in a graph how the changes in potential would look
Describe action potential
sudden reversal in cells membrane voltage momentarily moves from -70mV ot +40mV inside the cell based off of the movement of Na+ and K+ movement across the cell membrane
Describe depolarization
shift from negative to positive voltage
Describe the reflex action
when Na+ channels close after depolarization and postively charged K+ flow out restoring the negative resting potential
What are the four stages of an action potential?
- polarization
- depolarization
- reflex action
- absolute refractory period
describe the absolute refractory period
Recovery period as the original distribution of ions is reastiblished so cannot generate an action potenital during this period and due to this potential can only travel in one direction down axon
describe the all or none law
for a specific type of neuron, action potentials occur at a uniform and maximum intensity or they do not occur at all
Describe the action potential threshold
before the action potenital will be triggered, the charge inside the neuron must change from -70Mv to about -50Mv
Describe graded potentials
changes in the negative resting potential that do not reach -50Mv but over but over several neurons could add up to maybe cause an action potential
Describe the myelin sheath
A fatty insulation layer that coats the outside of many axons and is derived from glial cells durin development
Describe the nodes of Ranvier
interruptions in the myelin sheath at regular intervals where the sheath is nonexistant or thinner
How does the electrical impulse move along a mylenated axon?
skips from node to node - so faster and fewer action potential required than for unmylenated neurons
What is a disease resulting from damaged myelin sheath?
Multiple sclerosis
Describe multiple sclerosis
When a person own immune system attacks the myelin sheath
Describe a synapse
Where neurons communicate with each other through a functional connection but do not physically touch each other through the release of chemicals that carry the message from one neuron to the next in an organized circuit
What is the synaptic cleft?
The tiny gap that exists between the axon terminal of one end and the dendrite of the next neuron
Describe neurotransmitters
Chemicals that are produced and released from neurons that carry messages across the synapse he either excite or inhibit the activity of the next cell
What are the five steps of chemical communication between neurons?
- synthesis
- storage
- release
- binding
- deactivation
Describe the synthesis stage of chemical communication?
process whereby the chemical molecules are formed inside the neuron
Describe the storage stage of chemical communication
Synaptic vesicles within the axon terminal store the molecules produced in the neuron.
Describe the release stage of chemical communication
When an action potential comes down the axon, the chemicals being stored within the synaptic vesicles dock to the surface of the axon terminal and release the contents to the synaptic cleft.
Describe the bind stage of chemical communication
Molecules released from the presynaptic neurons move across the cleft and bind to receptor sites of the post synaptic neuron.
Describe the receptor sites of the post synaptic neuron
large protein molecules embedded in the post synaptic neuron membrane that have a specially shaped surfaces to bind to specific neurotransmitters. Once binded the neurotransmitter has an effect.
What two effects can a neurotransmitter have once it binds to a receptor?
Neurotransmitter will either depolarize or hyperpolarize the post synaptic cell membrane
What happens when a neurotransmitter depolarizes the post synaptic cell membrane?
Excites the membrane causing an influx of Na+ ions making it more likely to reach the threshold to instigate an action potential.
General term for the transmitters that cause depolarization
Excitatory neurotransmitter
What happens when a neurotransmitter hyperpolarizes the post synpatic membrane?
Creates a more negative potential at the membrane so that an action potential is less likely to occur
General term for transmitters that create hyperpolarization
Inhibitory neurotransmitter
Describe the deactivation stage of chemical communication
Once a neurotransmitter has bonded to its receptor site it continues to either excite or inhibit the neuron until its actions are stopped
What two major ways does deactivation occur?
- Some neurotransmitters are broken down to their orginal components by other chemicals in the synaptic cleft
- Otherwise through uptake whereby the released neurotransmitters are reabsorbed into the presynaptic terminal
How are drugs psychological effects determined?
By which specific neurotransmitter receptors the drug targets
What are seven common neurotransmitters?
- glutamite (glutamic acid)
- GABA (gamma-aminobutyric acid)
- Acetylcholine (ACh)
- Norepinephrine
- Serotonin
- Dopamine
- Endorphines
Describe the major function of glutamate
Excitatory neurotransmitter; Found throughout the brain and involved in control of all behaviour especially important in learning and memory
Describe the major functions of GABA
Inhibitory transmitter; Found throughout the brain; involved in control of all behaviours, especially important in anxiety and motor control
Describe the major function of acetylcholine
Excitatory add synopsis and is involved in muscular movement and memory
Describe the major functions of norepinephrine
Excitatory and inhibitory functions at various sites; Involved in neural circuits controlling learning, memory, wakefulness, and eating
Describe the major function of serotonin
Inhibitory it more sites; Involved in mood sleep eating and arousalAnd may be an important transmitter underlying pleasure and pain
Describe the major function of dopamine
Can be inhibitory or excitatory; Involved in voluntary movement emotional arousal motivation experiencing pleasure and learning
Describe the major function of endorphins
Inhibit the transmission of pain impulses
what are disorders associated with malfunctioning GABA?
- Huntingtons disease
- personality changes
what are disorders associated with malfunctioning Acetylcholine?
- Undersupply causes memory loss and Alzheimer’s disease
- Over supply causes muscle contractions and convulsions
what are disorders associated with malfunctioning Norepinephrine?
- Under supply may cause depression
- Oversupply may cause stress and panic disorders
what are disorders associated with malfunctioning serotonin?
depression, eating and sleeping disorders
what are disorders associated with malfunctioning Dopamine?
- Under supplied Parkinson’s disease and depression
- Oversupply schizophrenia
what are disorders associated with malfunctioning endorphins?
- Oversupply and sensitivity to pain
- Under supply pain hypersensitivity and immunity problems
Describe neuromodulators
More general and widespread influence on synaptic transmission And can either increase or decrease the sensitivity of neurons to the specific neurotransmitters. Play a role in functions such as eating sleep and stress.
