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
Define the nervous system
interacting network of neurons that conveys electro-chemical info throughout body
What are the 2 major divisions of the nervous system?
- Central nervous system: composed of brain and spinal cord
- Peripheral nervous system: connects nervous system to body’s organs and muscles
What does the central nervous system do?
- receives sensory info from external world
- processes and coordinates it
- sends it over to skeletal and muscular system for action
Name the 2 subdivisions of the peripheral nervous system
- somatic nervous system
- autonomic nervous system
What is the somatic nervous system?
- set of nerves that conveys info btw skeletal muscles and central nervous system
What is the autonomic nervous system?
- set of nerves that carries involuntary automatic commands that control blood vessels, body organs and glands
- regulates bodily system on its own outside of conscience
What are the 2 major subdivisions of the autonomic nervous system?
- sympathetic nervous system: set of nerves that prepare the body for action in challenging/threatening situations
- parasympathetic nervous system: helps the body return to a normal resting state
What are the 2 elements of the central nervous system?
brain and spinal cord
Define spinal reflexes
- simple pathways in nervous system that rapidly generate muscle contractions
- illustrate operation of reflex arc: neural pathway that controls reflex actions
What is the hindbrain?
- area of the brain that coordinates info coming in and out of the spinal cord
- controls most basic functions; respiration, alertness, motor skills
What are the 4 components of the hindbrain?
- medulla
- reticular formation
- cerebellum
- pons
What is the medulla?
extension of spinal cord into skull that coordinates heart rate, circulation & respiration
What is reticular formation?
- small cluster of neurons that regulate sleep, levels of arousal & wakefulness
- begins inside medulla then extends upward
- maintains balance btw. alertness & unconsciousness
What is the cerebellum?
- large structure that controls fine motor skills
- orchestrates proper sequence of movements
- fine tunes behavior for graceful execution
What is the pons?
- structure that relays info from cerebellum to rest of the brain
- bridge btw cerebellum & other structures in the brain
What are the 2 main structures of the Midbrain?
- tectum: orients an organism in the environment/receives stimulus input from eyes, ears, skin/ moves organism in coordinated ways towards stimulus
- tegmentum: involved in movement & arousal
What is the Forebrain?
- the highest level of the brain
- controls complex cognitive, emotional, sensory & motor functions
What are the 2 main sections of the forebrain?
- cerebral cortex: outermost layer of the brain/ visible to the naked eye
- subcortical structures: areas of the forebrain housed under cerebral cortex near center of the brain
What are the subcortical structures?
- protected structures deep inside the brain
- Thalamus
- Limbic system> hypothalamus, hippocampus, amygdala
- Basal ganglia
- Pituary gland
What is the Thalamus?
- relays & filters information from the senses & transmits the info to cerebral cortex
- receives input from all major senses
- thalamus actively filters sensory info, giving more weight to some/less to others
- closes pathways of incoming sensations during sleep
What is the hypothalamus?
- regulates body temp, hunger, thirst & sexual behavior
- helps regulate food intake
- part of the Limbic system
What is the Limbic system?
- group of forebrain structures involved in motivation, emotion, learning & memory
- where subcortical structures meet cerebral cortex
What are the 2 structure of the Limbic system?
- Hypocampus
- Amygdala
What does the hypocampus do?
critical for creating new memories & integrating them into a network of knowledge to be stored indefinitely in other parts of cerebral cortex
What does the Amygdala do?
- located a tip of each horn of hypocampus & plays a central role in many emotional processes (memories)
- handles emotional significance attached to events
- encodes events as fearful
What is the Basal ganglia?
- set of subcortical structures that directs intentional movements & plays a role in reward processing
- receives input from cerebral cortex > sends outputs to motor centers in brainstem
What does the stratum do in the basal ganglia?
- important role in control of posture & movement
- midbrain supplies stratum with dopamine > pleasure, motivation
What is the endocrine system?
- network of glands that produce & secrete hormones into the bloodstream which influence a wide variety of basic functions
- distinct from nervous system but works with it to regulate thoughts, emotions & behaviours
What are the endocrine system’s main glands?
- thyroid: regulates bodily functions
- adrenals: regulates stress response
- pancreas: controls digestion
- pineal: secretes melatonin, affecting sleep-wake cycle
which gland of the endocrine system orchestrates the overall functioning?
- Pituary gland: master gland of body’s hormone producing system which releases hormones that direct functions of many other glands
- hypothalamus sends signals to pituary gland> send hormonal signals to other glands
What are the 2 sexual reproductive glands?
- ovaries (f): produce estrogen
- testes (m): produce testosterone
What is the cerebral cortex?
- highest level of the brain; responsible for the most complex aspects of perception, emotion, movement and thought
What are the smooth surfaces and ridges/indentations of the cortex called?
smooth: Gyri
ridges: Sulci
allow cortex to fit more brain power in a smaller surface area
How the functions of the cortex be understood?
At 3 levels:
- separation of the cortex into 2 hemisphere
- function of each hemisphere
- role of specific cortical areas
Define contralateral control
- each hemisphere control the functions of the opposite side of the body
- right hemisphere perceives stimuli from & controls movem. on left side of the body
- left hemisphere perceives stimuli from & controls movem. on right side of your body
What connects the 2 cerebral hemispheres of the cerebral cortex?
- commissures: bundles of axons that allow communication between parallel areas of the cortex in each half
What is the largest commissure?
corpus collossum: connects large areas of cerebral cortex on each side of brain & supports communication of information across hemispheres
Name the 4 lobes the hemispheres of the cerebral cortex are divided into
-occipital
-parietal
- temporal
- frontal
(from back to front)
what is the occipital lobe?
- processes visual information
- at the back of cerebral cortex
What is the parietal lobe?
- processes info about touch
- contains somatosensory cortex: within each hemisphere it reps the skin areas on the opposite sided of body
- and motor cortex: initiates involuntary movem. & sends messages to basal ganglia, cerebellum & spinal cord
What is the temporal lobe?
- responsible for hearing and language
- contains primary auditory cortex: receives sensory info from ears based on frequencies of sounds
- houses areas that interpret meaning & help us identify familiar objects around us
What is the frontal lobe?
- specialized areas for movement, abstract thinking, planning, memory & judgment
- coordinate thought processes that help us plan our behaviors, retrieve memories & interact socially
What is an association area within a lobe?
- composed of neurons that help provide sense & meaning to info registered in the cortex
- helps produce understanding of what’s being registered in brain
What differentiates neurons in association areas from those in primary areas?
they are usually less specialized & more flexible > can be shaped by learning & experience to do their job more effectively
Name a type of neuron that exemplifies association areas
mirror neuron: active when animals performs an action and also when another animal observes that animal performing the same action.
> found in frontal & parietal lobe
What does brain plasticity mean?
- sensory cortices are not fixed and can adapt to changes in sensory inputs
- exercice: can increase the number of synapses & promote development of new neurons in hipocampus
What is the influence of culture on brain plasticity?
- exerts a notable impact on neurobiological processes
eg. there are cognitive differences btw westerners and easterners
Define gene
- major unit of hereditary transmission
- sections on a strand of DNA that code for the protein molecules that affect traits
- organized into large threads: chromosomes
Define chromosomes
- strands of DNA wound around each other in a double-helix configuration
- DNA in chromosomes produces protein molecules through Messenger RNA
- come in pairs (32 each)
- X and Y chroms. determine sex
What is messenger RNA?
Communicates a copy of the DNA code to cells that produce protein (chromosomes)
What is the degree of relatedness?
- probability of sharing genes
- monozygotic twins: share 100% of genes
- dizygotic twins: share 50% of genes
What are epigenetics?
- study of environmental influences that determine whether or not a gene is expressed/degree to which they are expressed w/o altering basic DNA sequence
- environment can influence gene expression through epigenetic marks
What are epigenetic marks?
- chemical modifications to DNA that can turn a gene on/off
Name 2 common epigenetic marks
- DNA methylation: an enzyme called epigenetic writer adds a methyl group to DNA, which switches off the methylated gene
- Histone modification: involved adding chemical modifications to proteins involved in packaging DNA (histones)/DNA is tightly packed around groups of histone proteins which can switch genes on/off
Define heritability
- measure of variability of behavioral traits among individuals, that can be explained by genetic factors
- Scores btw 0 and 1 > individual differences are caused by varying degrees of genetic and environ. factors
What are the 4 limitations of heritability?
- abstract concept: tells us nothing about specific genes that contribute to a gene
- tells us nothing about an individual
- dependent on environ.: meaningful only in specific environ.
- it’s not fate: tells us nothing about degree to which interventions can change behavioral trait.
Define neurodiversity
idea that there are natural variations in structure and function of the brain that produce variations across individuals in cognitive, social & emotional functions that should be distinguished from disorders/damaged brain
What is an ELECTROENCEPHALOGRAPH?
device used to record electrical activity in the brain
What do neurons in the visual cortex have?
- feature detectors: selectively respond to certain aspects of a visual image
- some visual processing neurons in temporal lobe activate only when detecting faces
What is a Computerized axial tomography scan (CT)?
- scanner rotates around person’s head & takes x-rays from diff. angles
- show diff. densities of brain tissue
- used to locate lesions/ tumors: appear darker because they are less dense than the cortex
What is Magnetic resonance imaging? (MRI)
- use strong magnetic field to line up nuclei of specific molecules in brain tissue
- diff. molecules have unique energy signatures when they snap back in line with the magnetic field
- these can be used to reveal brain structures w/ diff. molecular compositions
What are limitations of MRIs and CT scans?
both can help localize brain damage but tell us nothing about the functions of the brain
What is Diffusion Tensor Imaging (DTI)?
- type of MRI used to visualize white matter pathways > fiber bundles that connect both nearby & distant brain regions to each other
- measures rate &direction of movement of water molecules > indicates where the white matter pathways go
What does functional brain imaging do?
shows researcher the brain in action
What is Position Emission Tomography (PET)?
- radioactive substance injected into a person’s bloodstream
- brain scanned by radiation detectors while person performs tasks
- active areas of brain need more energy and thus bloodflow> higher amount of radiation in that region
What is a Functional Magnetic resonance Imaging (fMRI)?
- detects the difference between oxygenated hemoglobin and deoxygenated hemoglobin when exposed to magnetic pulses
- active neurons demand more energy & bloodflow> oxygenated blood concentrates in active areas
What are 4 advantages of fMRI over PET?
- fMRI does not require any exposure to radioactive substances
- fMRI can localize changes in brain activity over briefer periods than PET
- fMRI allows researchers to design experiments that more clearly resemble ones done in a psychology lab.
- fMRI can be used to explore the relationship btw brain regions using Resting state functional connectivity > absence of stimuli
What is the default network?
group of interconnected regions in frontal, temporal & parietal lobed involved in internally focused cognitive actions
eg” remembering faces, past events,..
