Chapter 3: Biology & Behaviour

Question 1

What are two ways behaviour can be explained?

Answer 1

materialism
mentalism

Question 2

What is materialism?

Answer 2

behaviour can be explained by the working of the brain and the rest of the nervous system (no need to refer to the mind)

Question 3

What is mentalism?

Answer 3

of the mind; explanation of behaviour as a function of the mind

Question 4

Cells of the nervous system

Answer 4

neurons & glial cells

Question 5

What are neurons

Answer 5

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

Question 6

What are the three types of neurons

Answer 6

motor neuron
interneuron
sensory neuron

Question 7

What are glial cells

Answer 7

outnumber neurons by 10 to 1
make up 50% of the brain volume
support, nourish neurons and remove their waste

Question 8

What is the pathway from stimulus to response

Answer 8

stimulus
receptor
sensory neuron
efferent neuron
target cell effector
response

Question 9

What is an axon

Answer 9

part of the neuron
- long thin fiber that transmits signals away from the cell body to other neurons, muscles, or glands

Question 10

What is a myelin sheath

Answer 10

wraps around many but not all axons
- derived from glialcells
- speeds up signal transmission along the axon

Question 11

What will the degeneration of myelin sheath lead to?

Answer 11

ineffective signal transmission
multiple sclerosis
- loss of muscle control
- weakness & paralysis
- vision difficulties

Question 12

What is a terminal button

Answer 12

the end of an axon filled with neurotransmitters (chemical messengers)

Question 13

What is a synapse

Answer 13

connection between two neurons, or a neuron and an effector

Question 14

Neuron at Rest

Answer 14

• 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

Question 15

What is an action potential

Answer 15

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

Question 16

Know what the different parts of an action potential refer to

Answer 16

1. resting potential
2. depolarisation
3. repolarisation
4. resting potential

Question 17

What is depolarization

Answer 17

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

Question 18

When does a depolarization have no affect? (failed initiations)

Answer 18

between -70 to -55 mV threshold

• negativity of the membrane must be reduced to less than -55 mV for an action potential to occur

Question 19

What is repolarization

Answer 19

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

Question 20

What is hyperpolarization?

Answer 20

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

Question 21

What is absolute refractory period

Answer 21

• 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

Question 22

What is relative refractor y period

Answer 22

• the period during which the neuron can fire but its threshold for hiring is elevated
• more intense stimulation is required to initiate action potential

Question 23

What is the all or none law

Answer 23

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

Question 24

what conveys the strength of a stimulus

Answer 24

rate of firing

Question 25

How do neurons communicate with each other

Answer 25

through neurotramsitters in the synapse - between the end foot of an axon and the dendritic spine of another neuron

Question 26

What are the 7 steps of communication between neurons

Answer 26

1. action potentials arrive at axon terminal 2. voltage-gated Ca2+ channels open 3. Ca2+ enters the cell 4. Ca2+ signals to vesicles 5. vesicles move to the membrane 6. docked vesicles release neurotransmitter by exocytosis 7. 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

Question 27

What happens after the neurotransmitter is bound to the receptor on the postsynaptic cell - what are excitatory and inhibitory transmitters?

Answer 27

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

Question 28

What are two types of synaptic transmissions

Answer 28

convergent synaptic transmission & divergent synaptic transmissions (review diagram)

Question 29

What are postsynaptic potentials

Answer 29

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

Question 30

What are two types of messages can be sent from cell to cell

Answer 30

- excitatory PSP (overall positive) - inhibitory PSP (over negative)

Question 31

Where is the postsynaptic potential on the action potential voltage time graph

Answer 31

see graph

Question 32

Exitatory PSP (EPSP)

Answer 32

positive voltage shift increases likelihood that the postsynaptic neuron will fire action potentials

Question 33

Inhibitory PSP (IPSP)

Answer 33

negative voltage shift - decreases likelihood that the postsynaptic neuron will fire action potentials

Question 34

What is the dopamine hypothesis of schizophrenia

Answer 34

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

Question 35

What is an agonist

Answer 35

drug that mimics or enhnces the effect of a neurotransmitter

Question 36

What is an antagonist

Answer 36

drug that blocks or reduces the effect of a neurotransmitter

Question 37

What is the plasticity of synapses

Answer 37

capability of change in response to environment or learning - repetitive exposure to the same stimulus can bring about long-lasting change in synapses

Question 38

In what three ways can synapses be altered in response to an organism's experience

Answer 38

- change in the release of neurotransmitter - grow new synaptic connections - modify their structures

Question 39

Two types of learning that can result in changes in neurotransmitter release

Answer 39

habituation sensitization

Question 40

What is habituation learning

Answer 40

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

Question 41

What is sensitization learning

Answer 41

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

Question 42

Experiment with the sea hare

Answer 42

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

Question 43

Basic brain structures

Answer 43

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

Question 44

Basic subcortical structures

Answer 44

basal ganglia - movement, reward thalamus - sensory gateway hippocampus - memory hypothalamus - regulates body function amygdala - emotion cerebral cortex

Question 45

What is brain plasticity and what are the three lines of evidence for it

Answer 45

the brains ability to change structure & function 1. brain structure may change with experience 2. damage to incoming sensory pathway or the destruction of brain tissue can lead to neural reorganization 3. adult brain can generate new neurons

Question 46

What is the result of damage to the right parietal lobe

Answer 46

hemineglect or hemi-inattention - disruption or decreased ability to look at something in the left field of vision - attention related disorder

Question 47

What is corpus callosum

Answer 47

the nerve fibers that enable communication between two hemispheres