Neuroscience and behaviour Flashcards
Define neuron
cells in the nervous system that communicate with others to perform information processing tasks
What are the 3 components of a neuron?
- cell body
- axon
- dendrites
What is the cell body in a neuron?
-largest component of the neuron that coordinates the information-processing tasks and keeps the cell alive
- contains a nucleus that houses chromosomes which contain DNA
- enclosed by porous cell membrane
What functions happen inside of the cell body?
- protein synthesis
- energy production
- metabolism
What are dendrites in a neuron?
- receive information from other neurons and relay it to the cell body
- extension of the cell membrane
- look like branches
What are axons in a neuron?
- carries information to other neurons, muscles or glands
- covered by a myelin sheath: insulating layer of fatty material
- there is a gap between the axon of one neuron and dendrites/cell body of another
What is the myelin sheath composed of?
- glial cells : support cells found in the nervous system
Define synapse
junction/region between the axon of one neuron and dendrites or cell body of another
What are the 3 types of neurons specialized by function?
- sensory neurons
- motor neurons
- interneurons
What are sensory neurons?
- receive info from external world and convey it to the brain via the spinal cord
- specialized endings on dendrites that receive signals for light, sound, touch, taste…
What are motor neurons?
- carry signals from spinal cord to muscles to provide movement
- often have long axons to reach extremities
What are interneurons?
- connect sensory neurons, motor neurons and other interneurons
- most common type of neuron
What are the 3 neurons specialized by location?
- Purkinje cells
- Pyramid cells
- Bipolar cells
What are Purkinje cells?
- type of interneuron that carries info from cerebellum to the rest of the brain and spinal cord
- dense elaborate dendrites that resemble bushes
What are pyramid cells?
- found in cerebral cortex
- have a triangular cell body and a single long dendrite among many smaller ones
What are bipolar cells?
- type of sensory neuron found in retinas of the eye
- have a single axon and dendrites
Define ion
- atoms that carry a small positive or negative electrical charge
- flow of ions across neurons cell membrane creates conduction of electric current within neuron
Explain the resting potential of a neuron
- normally some ions are more abundant inside the neuron : K+
- other ions are more abundant outside of neuron in the fluid-filled space between neurons : A-
- net result: inside of neuron has a slight negative electric charge relative to the outside -70mv
What allows the difference in concentration of ions inside and outside of the neuron cell membrane?
- cell membrane is porous
- special channels in cell membrane restrict the movement of ions in and out of the cell
Define action potential
- an electric signal that is conducted along the length of a neurons axon to a synapse
- occurs only when electric charge reaches a threshold:
- electric stimulation below will fail to produce action potential
electric stimulation at/above will always produce action potential
How does the action potential move across a neuron in a domino effect?
-during resting potential membrane channels for sodium ions are closed
- when electrical charge reaches threshold sodium channels in that area open up and Na+ ions rush in
- Na+ ions spread inside cell increasing electric charge in neighboring areas too
- when electric charge reaches threshold channels in adjacent cell membrane open and let in more Na+ ions spreading charge even further
What increases conduction of action potential?
- myelin sheath around axon prevents electric current from leaking out of axon
- clumps around axon with break points > nodes of Ranvier
- current jumps quickly from node to node
Define refractory period
- time following an action potential during which a new action potential can’t be initiated
- Na+ channels in each region of axon are temporarily inactivated after action potential passes over them
- during refractory period the chemical balance of a neuron is restored w/ ion pumps
Define ion pumps
work to redistribute ions until concentrations are rebalanced and resting potential is restored
Define terminal buttons
- knoblike structures that branch out from an axon
- each filled with tiny vesicles that contain neurotransmitters
Define neurotransmitter
chemicals that transmit information information across a synapse to a receiving neuron’s dendrites which contain receptors
Define receptors
part of the cell membrane that receives neurotransmitters and either initiate/prevent a new electric signal
Outline synaptic transmission
- sending and receiving of chemical neurotransmitters
- action potential in presynaptic neuron travels down the length of the axon to terminal buttons
> stimulates the release of NT from vesicles into synapses
> NT float across synapse and bind to receptor sites on nearby dendrite of post synaptic neuron
What are the 3 ways Neurotransmitters leave the synapse?
- reuptake
- enzyme deactivation
- diffusion
Define Reuptake
when NTs are absorbed by terminal buttons of presynaptic neuron’s axon/neighboring glial cells
Define enzyme deactivation
specific enzymes break down specific NTs
Define diffusion
when NTs drift out of synapse and can no longer reach receptors
Define auto-receptors
detect how much of a NT has been released and may stop the release of more
What is ACETYLCHOLINE?
- a NT involved in number of functions including voluntary motor control
found in neurons of brain and synapses where axons connect muscles and organs - activates muscle movement
- helps regulate attention, learning, sleeping, dreaming and memory
What is DOPAMINE?
- NT that regulates motor behaviour, motivation and emotional arousal
- role in basic motivated behaviours
- plays a role in drug addiction
What is GLUTAMATE?
- major excitatory NT in the brain
- enhances transmission of info btw. neurons
What is GABA?
- primary inhibitory NT in the brain
- prevents firing of neurons
Which 2 NT influence mood and arousal?
- NOREPINEPHRINE: involved instates of vigilance/heightened awareness of dangers in environment
- SEROTONIN: involved in regulation of sleep & wakefulness, eating and aggressive behaviour
- low levels of each associated w/ mood disorders
Define ENDORPHINS
- chemicals that act within the pain pathways & emotion centers of the brain
- similar properties as morphine but less intense
How do drugs affect the nervous system?
- work by increasing, interfering with or mimicking the manufacture or function of NTs
What are agonists?
- drugs that increase the actions of a NT
- drug activates the NT by binding to a receptor
What are antagonists?
- drugs that diminish the function of a NT
- prevent NT from acting or less its effect
Give an example of an agonist
- L-dopa: drug made from Dopamine that treats Parkinsons
- Parkinsonns caused by loss of neurons that make dopamine by modifying L-dopa produced naturally in the body
- L-dop acts as an agonist for dopamine > increasing natural production of dopamine
Give 3 examples of drugs that affect the nervous system
- Opioids: agonists for endorphins, creates powerful feelings of calm and euphoria
- Prozac: blocks reuptake of serotonin/more serotonin remains in synapse longer
- Propanol: obstruct receptor sites in heart for norepinephrine, which increases one’s heartbeat
What drug counteracts the effects of Opioids?
- Nalaxon: technically an opioid but acts as an antagonist
- binds with opioid receptors blocking agonists like heroin & preventing their effects on neurons