Chapter 3: Biology & Behaviour Flashcards
What are two ways behaviour can be explained?
materialism
mentalism
What is materialism?
behaviour can be explained by the working of the brain and the rest of the nervous system (no need to refer to the mind)
What is mentalism?
of the mind; explanation of behaviour as a function of the mind
Cells of the nervous system
neurons & glial cells
What are neurons
basic structural and functional units of the nervous system
function: receive, integrate, and transmit information
- all have a cell body
- tree like dendrites specialized to receive information
- an axon
What are the three types of neurons
motor neuron
interneuron
sensory neuron
What are glial cells
outnumber neurons by 10 to 1
make up 50% of the brain volume
support, nourish neurons and remove their waste
What is the pathway from stimulus to response
stimulus
receptor
sensory neuron
efferent neuron
target cell effector
response
What is an axon
part of the neuron
- long thin fiber that transmits signals away from the cell body to other neurons, muscles, or glands
What is a myelin sheath
wraps around many but not all axons
- derived from glialcells
- speeds up signal transmission along the axon
What will the degeneration of myelin sheath lead to?
ineffective signal transmission
multiple sclerosis
- loss of muscle control
- weakness & paralysis
- vision difficulties
What is a terminal button
the end of an axon filled with neurotransmitters (chemical messengers)
What is a synapse
connection between two neurons, or a neuron and an effector
Neuron at Rest
- cell membrane of axon is semi-permeable
- Na+ & K+ are pumped back and forth across the membrane at different rates
- difference in flow rates leads to higher concentration of negatively charged ions inside the cell
- resting potential of an axon = -70 millivolts
What is an action potential
the sudden change in voltage when neuron is stimulated and a brief jump occurs in the neuron’s voltage (a spike is observed on the voltmeter)
- action potential travels along axon like a spark
Know what the different parts of an action potential refer to
- resting potential
- depolarisation
- repolarisation
- resting potential
What is depolarization
in myelinated neurons, action potentials occur in nodes of Ranvier only
- when neuron is stimulated, voltage-gated Na+ channels in its cell membrane open and allow Na+ to rush in
- negativity of the membrane potential is reduced
- membrane is hence depolarized
When does a depolarization have no affect? (failed initiations)
between -70 to -55 mV threshold
- negativity of the membrane must be reduced to less than -55 mV for an action potential to occur
What is repolarization
when transmembrane potential reaches +35 mV, voltage-gate Na+ channels close, K+ channels open and allow K+ to rush out the membrane
- negativity of the membrane potential increases (becomes more negative)
- membrane is hence repolarized
What is hyperpolarization?
membrane potential overshoots to nearly -90 mV and K+ channels close
- then, Na+ and K+ pump quickly brings the membrane back to its normal resting potential of -70 mV
What is absolute refractory period
- after the firing of an action potential, some time is needed before the neuron can fire another action potential
- this downtime lasts 1-2 milliseconds
What is relative refractor y period
- the period during which the neuron can fire but its threshold for hiring is elevated
- more intense stimulation is required to initiate action potential
What is the all or none law
the neuron either fires or does not
-there is no such thing as smaller action potentials due to weaker stimuli
- stonger stimulus will cause a neuron to fire more frequently
- thicker axons transmit neural impulses more rapidly
what conveys the strength of a stimulus
rate of firing
How do neurons communicate with each other
through neurotramsitters in the synapse
- between the end foot of an axon and the dendritic spine of another neuron
What are the 7 steps of communication between neurons
- action potentials arrive at axon terminal
- voltage-gated Ca2+ channels open
- Ca2+ enters the cell
- Ca2+ signals to vesicles
- vesicles move to the membrane
- docked vesicles release neurotransmitter by exocytosis
- neurotransmitters diffuses across the synaptic cleft and binds to the receptors on the postsynaptic cell
Notes: some neurtransmitters are taken back into the axon terminal through the neurotransmitter re-take pump, whereas others are eactivated
What happens after the neurotransmitter is bound to the receptor on the postsynaptic cell
- what are excitatory and inhibitory transmitters?
excitatory transmitters cause depolarization
- inside of receiving neuron becomes positive
- increases likelihood of action potential
inhibitory transmitters cause hyperpolarization
- inside of receiving neuron becomes negative
- decreases the likelihood of an action potential
What are two types of synaptic transmissions
convergent synaptic transmission & divergent synaptic transmissions
(review diagram)
What are postsynaptic potentials
when a neurotransmitter and receptor molecule combin, reactions in the cell membrane cause a postsynaptic potential (PSP)
- voltage change at the receptor site on a postsynaptic cell membrane
- they are graded (not all-or-none) bc it is a summation of many signals from pre-synaptic neurons
- size and direction of a PSP will increase or decrease the probability of a neural impulse in the receiving cell
What are two types of messages can be sent from cell to cell
- excitatory PSP (overall positive)
- inhibitory PSP (over negative)
Where is the postsynaptic potential on the action potential voltage time graph
see graph
Exitatory PSP (EPSP)
positive voltage shift
increases likelihood that the postsynaptic neuron will fire action potentials
Inhibitory PSP (IPSP)
negative voltage shift
- decreases likelihood that the postsynaptic neuron will fire action potentials
What is the dopamine hypothesis of schizophrenia
some forms of schizophrenia may be related to excessive dompamine activitiy
- amphetamine and cocaine create schizophrenia-like symptoms by increasing dopamine activity at the dopamine synapses
What is an agonist
drug that mimics or enhnces the effect of a neurotransmitter
What is an antagonist
drug that blocks or reduces the effect of a neurotransmitter
What is the plasticity of synapses
capability of change in response to environment or learning
- repetitive exposure to the same stimulus can bring about long-lasting change in synapses
In what three ways can synapses be altered in response to an organism’s experience
- change in the release of neurotransmitter
- grow new synaptic connections
- modify their structures
Two types of learning that can result in changes in neurotransmitter release
habituation
sensitization
What is habituation learning
simple form of learning in which the strength of a response to a certain stimulus becomes weaker with repeated presentations of that stimulus
- calcium channels become less responsive to voltage changes
- influx of Ca2+ in response to an action potential decreases, resulting in LESS neurotransmitter released at the presynaptic membrane and LESS depolarization of the postsynaptic membrane
What is sensitization learning
enhanced response to a stimulus
- K+ channels become less responsive and slower to open, prolonging an action potential
- this causes more Ca2+ influx and increased transmitter release, resulting in MORE neurotransmitters released at the pre-synaptic membrane and MORE depolarization of the postsynaptic membrane
Experiment with the sea hare
aplysia californica
- when threatened, it defensively withdraws its gill and siphon
- is habituated to the touch of waves (a novel stimulus resembling a wave will lose its novelty over time)
- a novel stimulus resembling an attack on its body will produce a hypersensitive response
Basic brain structures
frontal lobe - thinking, memory, behavior, and movement
temporal lobe - hearing, learning, and feelings
parietal lobe - language and touch
occipital lobe - sight
cerebellum - balance and coordination
brain stem - breathing, heart rate and temperature
Basic subcortical structures
basal ganglia - movement, reward
thalamus - sensory gateway
hippocampus - memory
hypothalamus - regulates body function
amygdala - emotion
cerebral cortex
What is brain plasticity and what are the three lines of evidence for it
the brains ability to change structure & function
- brain structure may change with experience
- damage to incoming sensory pathway or the destruction of brain tissue can lead to neural reorganization
- adult brain can generate new neurons
What is the result of damage to the right parietal lobe
hemineglect or hemi-inattention
- disruption or decreased ability to look at something in the left field of vision
- attention related disorder
What is corpus callosum
the nerve fibers that enable communication between two hemispheres
