Chapter 3: Neuroscience Flashcards
What were the methods used to study human neuroscience decades ago? (4)
Examining autopsy issue
Testing the behaviour of patients with damage to certain parts of the brain
Recording electrical brain activity through multiple electrodes attached to the surface of the scalp
Animal studies
What is the leading idea of testing the behaviour of patients with damage to certain parts of the brain?
the inference is that brain function is localized,so loss of a particular function suggests what function that particular area of the brain is in charge of
event related potentials (ERP) can be analyzed to determine:
WHEN the event takes place
recording electrical brain activity is not ideal for identifying….
WHERE activity takes place because skull dilutes electrical signals
lesioning
targeting specific brain areas for destruction and observing the effects on behaviour
transcranial magnetic stimulation (TMS)
delivers an electromagnetic pulse to a targeted brain area, disrupting localized brain activity in a conscious person
What is the main drawback of the methods in neuroscience used several decades ago?
It tells us little about activity in specific regions of healthy, living, human brains
neuroimaging
techniques that allow for studying brain activity and structure by obtaining visual images in awake human
computerized axial tomography (CAT or CT)
produces clear, detailed, 2D X-ray images which can be computerized and combined to produce a 3D brain.
It is better at detecting problems and is faster to administer
Magnetic resonance imaging (MRI)
uses strong magnetic fields to produce images, computer creates a 3D image, produces clearer scans than CT and has no radiation effects.
It is better at detecting soft tissue injuries in tendons and ligaments, spinal cord and brain. It cannot be used if metal is present
diffusion tensor imaging (DTI)
measures the orientation and integrity of white matter to assess damage in the brain, produces a colour map
useful for concussion
structural images do not enable researchers to:
identify brain regions that become active under specific conditions
functional neuroimaging tells us about:
activity in particular brain areas during specific behaviours
what are some methods to detect activities?
PET and fMRI
positron emission tomography (PET)
harmless radioactive substance injected into a person’s blood, radiation detectors than scan the brain.
Active brain areas=more blood flow and higher amounts of radioactivity
functional magnetic resonance imaging (fMRI)
detects changes in blood flow (indicates changes in activity of neurons)
detects amount of oxygenated hemoglobin after a person is exposed to magnetic pulses
DOES NOT REQUIRE RADIATION, ABLE TO QUICKLY DETECT CHANGES IN BRAIN ACTIVITY
Neuron
A nerve cell
Networks
Neurons that work together in a group
Cell body
Received information from dendrites, and if enough stimulation is received the message is passed on to the axon
Contains the nucleus which contains genetic information and functions related to life occur
Dendrites
Receive information from other neurons and sensory receptors
Axon
Carries the neuron’s message to the terminal buttons
Myelin sheath
Is a type of glial cell that covers segments of the axon to insulate and speed the neural impulses
Terminal buttons/axon terminal
Forms junctions withe other cells and release chemicals called neurotransmitters
Neurons can have many dendrites but have only one
Axon
What is another word for the branches of axons?
Collaterals
What are 2 things all neurons have in common?
- Covered by a specialized membrane that surrounds the entire neuron
- Capable of communicating with other cells by means of chemical and electrical signals
Glia
The cells that, in addition to neurons, make up the nervous system
What are some of the different kinds of glial cells (5)?
Astroglial, oligodendria, Schwann cells, epidymal cells, microglia
Functions of astroglial:
Blood-brain barrier, regulated flow of blood in areas of brain based on activity, absorb/clean up chemicals released by neighbouring neurons, provides growth-promoting molecules to neurons, forms a glial scar at sites of brain injury
Oligodendria (CNS) and Schwann cells (PNS) function:
Provides myelin: protective fatty sheath that insulates neurons from nearby neuronal activity and speeds up transmission of signals
Ependymal cells
Specialized glia cells that line the walls of the ventricles (fluid filled space in the brain), creates and secretes cerebrospinal fluid
Microglia
Important brain defence against infection/illness, cleans up debris of degenerating or dead neurons and glia
resting potential
the electrical charge of a neuron when it is at rest (-70mV, negative on the inside relative to the outside)
concentration gradient
the difference in concentration of sodium ions inside and outside of the neuron
what ions contribute to the resting potential?
Na+, K+, Cl- and negatively charged protein ions (A-)
what is higher in concentration outside of the cell?
Na+ and Cl-
What is higher in concentration on the inside of the cell?
K+ and A-
ions are not distributed equally across membranes because:
the membrane is selectively permeable (ion channels and sodium-potassium pump)
ion channels
pores in the cell membrane that can open and close to allow certain ions into or out of the cell (mostly negative molecules trapped inside)
sodium-potassium pump
protein pumps in the membrane of cells that push out sodium ions and push in potassium ions (3 Na+ out for every 2 K+ in)
action potential
a sudden positive charge of a neuron’s axon, also known as a spike or firing; action potentials are rapidly transmitted down the axon
threshold of excitation
the point at which the relative influence of other neurons succeeds in causing a neuron to initiate an action potential (effects of excitatory input from other neurons outweigh the effects of inhibitory input)
depolarization
the inside of the neuron membrane becomes LESS negative relative to the outside
hyperpolarize
the inside of the neuron membrane becomes MORE negative relative to the outside
excitatory postsynaptic potentials (EPSP’s)
postsynaptic depolarization that increase chances of neuron firing
inhibitory postsynaptic potentials (IPSP’s)
hyper polarize the membrane and decrease chance of cell firing
summation
net effect of excitatory and inhibitory signals
actions potentials are:
“all-or-none” events
stronger stimuli causes:
more neurons to fire more often (higher frequency)
outline the process of an action potential:
sodium ion channels open, sodium enters cell (+50mV), potassium channels open (repolarization to hyperpolarized state), sodium-potassium pump re-establishes resting membrane potential
myelin
a fatty white substance formed from glial cells that insulates the axons of many neurons
action potentials occur at:
nodes of Ranvier
saltatory conduction
the process of action potentials jumping from node to node
absolute refractory period
a very brief period of time after an action potential during which a neuron is completely unable to fire again
relative refractory period
a brief period just after the absolute refractory period during which a neuron can only fire if it receives a stimulus stronger than its usual threshold level
synapse
tiny spaces between the axon terminal of one neuron and the neuron through which chemical communication occurs
neurotransmitters
specialized chemicals that travel across synapses to allow communication between neurons
synaptic vesicles
membrane-bound spheres in the axon terminals of neurons in which neurotransmitters are stored before their release
serotonin
neurotransmitter involved in activity levels and mood regulation
when are neurotransmitters released?
when the action potential reaches the presynaptic axon terminal
where do neurotransmitters bind?
to receptors on the dendrites of the postsynaptic cell
neurotransmitter receptors
proteins in the membranes of neurons that bind to neurotransmitters
postsynaptic potentials
electrical evens in postsynaptic neurons that occur when a neurotransmitter binds to one of its receptors
neurotransmitters can be:
excitatory or inhibitory or both (depending on the type of receptor present)
termination of neurotransmitter action occurs in two ways:
- enzyme degradation or 2. reuptake
outline the process of enzyme degradation
enzyme breaks down neurotransmitters, products are reabsorbed by the cell and used to synthesize more neurotransmitters
outline the process of reuptake
neurotransmitters are drawn back into the presynaptic neuron and recycled for future use.
stem cells
undifferentiated cells that can divide to create new cells that have the potential to become any other cell type, including neurons
neural circuits or networks
collections of neurons that communicate with one another in a sequential fashion
Hebbian synapses
synapses that change as a result of input or experience
as mental processes are repeated, synaptic connections are:
strengthened
neuroplasticity
the brain’s ability to create new neural pathways as a result of experience or following an injury
synaptic plasticity
plasticity at the synapse, ex. changes that occur from repeated release of neurotransmitters
