Option A Flashcards
Neurobiology (148 cards)
1
Q
Notochord
A
The dorsal rod that supports the body
2
Q
Neural tube
A
A hollow, embryonic tube, developed from neural groove into spinal chord and vertebral column
3
Q
Stages of neurulation
A
- Thickening and elongation: ectoderm develops into neural tube
- Folding: cells in neural plate change shape, fold in and form a neural groove
- Convergence: lateral edges of neural plate join together to form tube-like structure
- Fusion: neural tube fuses together
- Elongation: neural tube elongates as embryo grows
NB/
- proliferation of cells by mitosis allows continued development of neural plate into neural tube
- differentiation in neural tube produces different types of functioning neurons
- many more neurons are produced than actually required- so any nonessential or damaged cells can be destroyed for survival of organism
4
Q
Neurulation
A
Folding process that develops neural plate into the neural tube
5
Q
Formation of a neuroblast
A
Each neural stem cell divides by mitosis and produces another stem cell and a progenitor cell, which will eventually differentiate into a neuroblast
6
Q
Migration of neurons
A
- immature neurons migrate to a final location
- path of migration is determined by which part of brain is the final location
- immature neurons don’t have all the structures associated w/ a fully developed neuron eg. axons and dendrites
- migration happens as plasma membrane extends and cell body is moved to leading, forward edge by contraction of actin filaments
7
Q
Neurogenesis
A
Birth, growth and development of new neurons in the brain
8
Q
Immature neuron that is growing
A
Immature neuron
- Cell body (contains nucleus and cytoplasm)
- cell body develops and grows into an axon
- shorter branches will also grow (dendrites)
9
Q
Axon
A
- A long narrow growth from the cell body
- Used to carry electrical signals from one cell to another
10
Q
Dendrites
A
- Shorter branches
- highly-branched and responsible fro bringing the electrical signals into the neuron
11
Q
Chemical stimuli in the growing axon
A
In form of signalling molecules that are capable of binding to specific receptors
- can be ‘read’ by neuron
- allows neuron to know exactly the direction and scale that it must grow
- growing axon alters its internal structure to allow for this growth + find its correct target location
12
Q
Length of axons
A
- longer axons carry impulses to effectors eg. muscles and glands
- carry out responses determined by CNS
13
Q
Re-growth of damaged axons
A
- it’s possible for axons to regrow when damaged as long as cell body remains intact
- explains return of sensation and control to muscles-even after they have been damaged or lacking control previously
14
Q
Formation of synapses
A
- growing axon reaches its target cell in CNS or PNS
- a synapse develops between neuron and cell
- development of synapse takes place, structures are assembled on either side of synapse and in synaptic cleft
- most neurons develop multiple synapses w/ target cell, due to interaction between competing neurons for target cell
- more impulses that arrive at synapse, stronger that connection will be
- more likely that synapse will be maintained
15
Q
Synaptic pruning
A
- synapses that aren’t properly stimulated are unlikely to survive
- transmission at synapse leaves a chemical marker that strengthens that particular synapse
- without these chemical markers, synapses become weaker until they’re eventually eliminated
- only strongest, most beneficial synapses are used
16
Q
Neural pruning
A
- no. of neurons in brain of a baby is greater than no. in adult brain
- body produces more neurons than needed to ensure only best, most useful ones survive and are used
- neurons that don’t get used destroy themselves by apoptosis
17
Q
Apoptosis
A
Refers to natural death of a cell
18
Q
What is neural pruning?
A
Modifies cells by removing neurons that are no longer useful
- ensures that only useful connections are retained
19
Q
Plasticity
A
Ability of nervous system to change in structure and function as it develops w/ experience
20
Q
Spina bifida
A
Caused by incomplete closure of the embryonic neural tube
- caused when embryonic neural tube doesn’t fully close
- leads to vertebrae remaining unfused and open
- if gap is large enough, it’s possible for spinal cord to protrude
- effect is felt in lower back region
- pain and symptoms can range from v. mild to extremely severe and debilitating
21
Q
Four main types of spina bifida
A
- Occulta
- Closed neural tube defects
- Meningocele
- Myelomeningocele
22
Q
Occulta spina bifida
A
Most common type
- where a layer of skin hides opening in vertebrae
- rarely causes any symptoms
23
Q
Closed neural tube defects spina bifida
A
- spinal cord is affected by abnormal fat, bone or meninges
- symptoms range from none to complete paralysis
24
Q
Meningocele spina bifida
A
- occurs when spinal fluid and meninges protrude from vertebrae opening
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Myelomeningocele
- most severe
- spinal cord is exposed through vertebrae opening
- causes paralysis of body below that point in the spine
26
Stroke
Occurs when blood supply to brain is disrupted
- high metabolism and energy demands of brain mean that it needs a constant supply of oxygen and glucose to respire aerobically
- smallest of interruptions to blood supply will damage some neurons (neurons don't have glycogen reserves)
NB/ areas of brain damaged by a stroke can't grow new axons- because of scar tissue that blocks this from happening
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Causes of stroke
- may occur due to a blood clot in arterial network around brain
- results in loss of oxygen and glucose the brain needs
- as soon as cellular respiration ceases, neurons begin to be damaged beyond repair and die
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Effects of stroke
- vary from: unnoticed, full recovery, some form of disability to fatal
- destroyed neural connections can't always be rebuilt and repaired
- but, brain can take on new functions to compensate and support damaged areas
- it can reorganise itself after trauma eg. stroke
- so basic bodily functions can be carried out- sometimes by a different side of brain than before trauma
- may have to relearn key skills eg. speech, writing, walking, cooking and spatial awareness
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Neurulation in Xebnopus
- early stages of development are similar for all vertebrates
- hence, animal models can be used to observe them closely
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Advantages of observing neurulation in Xenopus
- rapid development of embryo- less than 48 hours in Xenopus
- zygotes are easily obtained due to external fertilisation
- ethically viable than using human embryos
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Embryonic tissues involved in neurulation in Xenopus
1. Endoderm: forms lining of the gut eg. digestive organs, lungs
2. Mesoderm: central layer that forms skeletal system and circulatory system eg. muscle, kidney, bone
3. Ectoderm: external layer that forms brain and nervous system via neural tube
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Function of medulla oblongata
- contains control centres for heart and lungs
| - controls breathing, swallowing and heart rate
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Function of cerebellum
- regulates muscular activity eg. posture, movement and balance
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Function of hypothalamus
- hormones are synthesised here
| - controls body temp., thirst, hunger and sleep
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Function of pituitary gland
- releases hormones made in the hypothalamus to regulate bodily functions
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Function of cerebral hemispheres
- centre for high-complexity functions eg. language, memory, numerical calculations, decision-making and emotions
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Two parts of ANS
ANS = autonomic nervous system
1. Sympathetic nervous system
2. Parasympathetic nervous system
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Function of ANS
- controls involuntary processes eg. blood flow, swallowing, heart rate and digestion
- these processes are controlled by centres in medulla oblongata
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Information on the brain is obtained from
- animal experiments
- autopsies
- lesion studies
- functional magnetic resonance imaging (fMRI)- identified different roles played by parts of brain
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How does a fMRI work?
- measures flow of blood to particular parts of brain while carrying out a task
- useful in identifying potential causes and relationships
- an increase in blood flow to a part of the brain while carrying out a task/ experiencing an emotion means that part of the brain controls what's being seen or experienced
- allows us to know that RIGHT brain controls muscles on LEFT-hand side
- LEFT brain controls muscles on RIGHT-hand side
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Correlation
means there is a similarity between two variables
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Causation
there is a cause-and-effect relationship between them
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Cerebral cortex
- outer layer of cerebral hemispheres
- it's the outer surface of cerebrum that's deeply wrinkled
- contains many different neurons that help to process some of the more complex tasks of the brain
- this extensive folding allows humans to evolve
- cerebral cortex is able to increase in total area, close to capacity of human skull
- developed cerebrum provides us w/ higher-order functions eg. memory, speech and emotions
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Four lobes of the brain
1. Frontal lobe
2. Parietal lobe
3. Temporal lobe
4. Occipital lobe
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Frontal lobe
Regulates higher intellectual functions
| - controls social behaviours
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Parietal lobe
Responsible for movement, spatial awareness and sense of touch
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Temporal lobe
Involved in speech, memory and hearing
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Occipital lobe
Visual centre is responsible for input from eyes
| - helps to judge distance and perspective
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Cerebral hemispheres function
- carry out more complex tasks eg. memory, speech and learning
- complex networks of neurons work together to piece together information from receptors and memories
- information forms basis of our reasoning and decision-making abilities
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Function controlled by left cerebral hemisphere
- receives sensory input from right side of body
| - receives sensory inputs from right side of field of vision in both eyes
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Function controlled by right cerebral hemisphere
- receives sensory input from left side of body
| - receives sensory inputs from left side of field of vision in both eyes
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Primary motor cortex
- Posterior part of frontal lobe
- controls voluntary muscle activity
- controls all of the muscle responses
- in the left cerebral hemisphere, controls muscles in right side of the body
- in the right cerebral hemisphere, controls muscles in left side of the body
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Visual cortex
- where neural signals from retinas of the eyes are processed
- allows us to recognise patterns and how fast an object might be moving
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Broca's area
- controls production of speech
| - enables us to communicate what we're thinking
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Nuclues accumbens
- each cerebral hemisphere contains a nucleus accumbens
- stimulated by things that give us pleasure or laughter
- dopamine is released in this area to cause these feelings (can also be released by cocaine and nicotine)
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Pupil reflex
- part of ANS
- response of iris, and hence, pupil size, is involuntary
- protects retina from damage or poor visual perception
- allows pupil reflex to be used when evaluating possible brain damage of a patient
57
Brain death
1. Bright light is shone into the eye
2. Parasympathetic system stimulates muscles in the iris
3. Pupil constricts to reduce amount of light that can get into eye
4. If pupils don't constrict immediately, it's a sign that medulla oblongata may be damaged
5. If a patient fails other tests, it may be considered as brain death- full recovery is unlikely
Other tests:
- observing blinking response
- a lack of gag reflex when a tube is placed in trachea
- lack of movement in eyes when head is moved
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Sensitivity
Capacity of living organisms to respond to changes in their internal or external environment
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Stimuli
Changes in internal or external environment
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Receptors
Detect changes in stimuli
- found at nerve endings of sensory neurons, or specialised receptor cells
- conduct an electrical impulse along sensory neurons to brain
- elicits a response via muscle or glands
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Four forms of energy that receptors respond to
- chemical
- mechanical
- light
- thermal
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Specialised receptors that humans have
1. Thermoreceptors: respond to heat energy
2. Photoreceptors: respond to light energy
3. Chemoreceptors: respond to chemical substances
4. Mechanoreceptors: respond to forces and movement
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Olfactory receptors
- located in upper part of nose
- capable of detecting chemicals in air, and smells from food in mouth that pass through nasal cavities to reach olfactory receptors
- different receptors found in nose allow animals to distinguish between large no. of chemicals in air
- receptors contain proteins in their membrane that bind w/ specific chemicals to induce electrical impulse sent to your brain
64
How is an image formed in the eye?
1. Light enters eye
2. Light is focused by cornea and lens onto retina
3. Retina contains photoreceptors that detect the light (two types- rods and cones)
4. Rods and cones work together to detect image being focused on the retina
- converts this to a signal that is sent to brain
5. Brain will use this information to perceive shape, size, movement, colour and direction of visible light
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Rods, cones and the fovea
Rods:
- distributed evenly throughout most of the retina
- absent from the fovea
Cones:
- found across the retina
- tend to be concentrated around the fovea
Fovea: part of retina used to look directly at an object
66
Light and the retina
1. Light passes through a layer of ganglion cells
2. Then, past bipolar neurons that process the signals
3. Then, reaches the rods and cones
As light passes through each part of the eye, it sends information to the brain via the optic nerve
67
Function and role of rods
Rod cells:
- perform well in low- intensity light
- in bright light, pigment in them is bleached for a few secs, as a rhodopsin molecule in rods is altered
- rhodopsin must be reconstructed, takes a few secs.
- accounts for temporary blindness experienced when moving from v. bright light to a v. dim light
- can absorb a wide range of wavelengths (400nm-600nm)
- can't distinguish between different colours- only provide B&W vision
68
Three types of cone cells
Three types absorb different ranges of visible light to distinguish colours
- red, green and blue cones are stimulated by colour they absorb strongly
- three types of cone cell in retina provide normal trichromatic vision
- relative stimulation is calculated by the brain to tell us what colour we can see
69
Red-green colour blindness
- commonly found in humans due to homozygous recessive alleles being inherited
- occurs due to a defect in gene for pigments in either green or red cone cells
- colour-blindness has a higher prevalence among males
- because, most common genes for this are usually found on X chromosome
70
How is an image produced in the retina?
Bipolar neurons synapse w/ multiple rods but individual cones in the retina
- images sent by rods tend to be of a lower resolution compared to images based on cone cells
- hence, images are due to cone cells synapsing w/ individual ganglion cells, allows for a high degree of resolution
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Convergence
- synapsing of multiple rod cells w/ ganglion cells causes convergence
- convergence gives poor resolution as images are 'blurred' by overlapping boundaries
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Ganglion cells
- contain a cell body and dendrites that form synapses w/ bipolar cells
- no. of impulses from bipolar cells increases in response to increased stimulation of ganglion cells
- axons of ganglion cells pass across front of retina to form a central bundle, form a blind spot
- axons of ganglion cells pass electrical impulses, via optic nerve and optic chiasma
73
Visual cortex
- humans use both eyes to best determine size and distance of objects
- stimuli from each of the eyes are sent to opposite side of visual cortex
- what is seen in left field of vision is processed in right side of visual cortex and vice versa
- crossing over of axons between left and right sides occurs in optic chiasma
74
Function of pinna
- part of outer ear
| - funnels sound waves to inside of the ear
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Middle ear
- an air-filled chamber that begins at eardrum and ends at oval and round windows
- bones in middle ear are smallest bones in human body
- used to transfer vibrations from eardrum to oval window
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Eardrum
- a thin but strong piece of tissue that is taut
| - vibrates in response to sound waves that hit it
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Oval window
Another thin sheet of tissue that connects to inner ear
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Bones of middle ear
1. Malleus
2. Incus
3. Stapes
- these bones (ossicles) work together to amplify sound by up to 20x
- but if ear is exposed to v. loud noises, ossicles are attached to muscles that are able to 'dampen' vibrations and protect the ear
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Cochlea
Responsible for converting sound vibrations into signals that can be ultimately transmitted to brain
- a spiral, coiled, fluid-filled tube
- separated into 3 different membranes that are responsible for detecting different types of frequency
80
Sensory cells in cochlea
- sensory cells are attached to basilar membrane and a network of sensory hairs stretch from one membrane to another
- sensory hairs are selectively activated to distinguish between different sounds and pitches that we hear
- sensory hairs of cochlea are able to detect sounds of a specific wavelength
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Oval and round window
- fluid in cochlea can't be compressed
- vibrations cause movements of fluid to be transmitted to round window
- oval window and round window work in tandem to transmit vibrations through the liquid
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Ampulla and cupula
- 3 fluid-filled semicircular canals are connected above cochlea
- each has a swelling at the end (ampulla)
- ampulla detects head movement due to inertia of liquid inside moving at a different rate
- this information is detected by hair cells in cupula ( in the ampullae) and a signal is sent to the brain
- movement of head can be detected in any direction due to perpendicular nature of the 3 semicircular canals
83
How does the brain detect different wavelengths of sound?
- Movement caused by pressure waves in inner ear stimulates hair cells in cochlea to release a neurotransmitter
- neurotransmitter crosses a synapse to stimulate a sensory neuron
- an electrical impulse is then sent to the brain along auditory nerve
- brain is able to detect the different wavelengths of sound waves by relative movements of basilar membrane
84
Cure for deafness
- is often overcome by hearing aids to amplify sounds
- this isn't suitable for all deaf patients as it can distort some parts of their hearing
- patients w/ defective hair cells in cochlea will be unable to hear certain frequencies and wavelengths
- simple amplification by hearing aids of all wavelengths won't be beneficial to them
- Cochlear implants are used to enhance speech recognition in these patients
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Structure of a cochlear implant
- consist of an external microphone linked to a speech processor
- processor filters speech frequencies and sends them to internal parts
- internal parts are surgically implanted behind ear; a receiver, a stimulator, and electrodes
- electrodes (implanted in cochlea) receive electrical impulses from stimulator- are sent to brain via auditory nerve
- allows hair cells that aren't functioning to be bypassed
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Innate behaviour
Behaviour that's inherited from parents
- develops independently of the environment
- isn't affected by external influences
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Palmar grasp reflex
- an object is placed into palm of a baby's hand
- baby will instinctively grip object
- reflex occurs from birth- innate - the baby is born with the ability to do it
- behaviour is inherited from parents
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Two types of behaviour
1. Taxis
| 2. Kinesis
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Taxis
a change in movement in response to a stimulus
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Kinesis
a change in rate of activity in response to a stimulus
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Choice chambers
- woodlice prefer dark, damp conditions
- ideal testing subjects for taxis and kinesis
- movement away from light (taxis) and speed of movement from dry to damp conditions (kinesis) can be observed quickly and easily
- woodlice behave this way due to increased chances of survival
- woodlice have gills for respiration that dry out when in dry conditions.
92
Reflex
a rapid response to a stimulus that occurs without having to think about doing it
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Production of a reflex
- an involuntary response controlled by autonomic nervous system
- message is sent by receptors to the brain
- brain then sends a message to an effector (a muscle or a gland) to execute desired response
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Reflex arc
journey of impulse from receptor to effector
- sensory neurons, relay neurons, and motor neurons have synapses that connect them
- allows impulse to be passed on
- Each neuron has a cell body and a nerve fibre for carrying impulses
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Structure of sensory neurons
- cell body is at centre of neuron
- Dendrites carry impulse to cell body, axon carries impulse away from cell body
- function is to carry impulses from receptor to central nervous system (CNS)
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Structure of relay neurons
- cell body makes up most of the neuron
- many short nerve fibres
- function is to enable communication between CNS and sensory/motor neurons
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Structure of moto neurons
- cell body is at the end of the neuron
- many dendrites carry impulses to cell body, axon carries impulse away from cell body
- function is to carry impulse from CNS to an effector (muscle or gland)
98
Pain withdrawal reflex
1. Pain receptors in the skin detect pain
2. This converts signal into an electrical impulse that's propagated along sensory neuron
3. Sensory neurons send impulse to spinal cord of CNS
4. Relay neurons continue impulse and send it along motor neuron
5. Motor neuron sends impulse to muscles near pain stimulus
6. Muscle fibres contract, causing that part of body to withdraw from pain stimulus
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Reflex conditioning
formation of new associations and occurs as new neural pathways are forged in the brain
100
Pavlov's experiments
- Pavlov noticed his dogs salivated when food was brought to them and when they associated certain noises w/ food arriving eg. his footsteps
- set up an experiment where he using conditioned stimuli, eg. bell ringing or flashing of a light, when food was delivered to dogs
- when these stimuli were played without food, dogs still salivated
- they'd been conditioned to salivate in anticipation of food arriving
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Experience
The patterns of behaviour in animals acquired as a result of observing their parents and environment around them
- varies from one individual to another
- experiences of each person/ animal results in different patterns of behaviour for different individuals
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Imprinting
used to describe learning that occurs in the earliest stages of animal life
- allows immediate bonds to be formed w/ parents
- parents are then able to pass on essential skills of survival
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Operant conditioning
- also known as trial and error learning
- learning takes place by persistent testing of consequences of a particular behaviour
- +ve or -ve impact informs animal, or human, and reinforces or inhibits behaviour
104
Training of a dog
| - 4 quadrants of operant conditioning
1. Positive reinforcement:
- dog's behaviour causes a good thing to happen
- behaviour increases
2. Negative reinforcement:
- dog's behaviour causes a bad thing to stop
- behaviour increases
3. Positive punishment:
- dog's behaviour causes a bad thing to happen
- behaviour decreases
4. Negative punishment
- dog's behaviour causes a good thing to stop
- behaviour decreases
105
Memory
The encoding, storage and assessing of information
106
Encoding
Converts information ready for storage
107
Accessing
Active recall of information when making decisions and during thought processes
108
Role of inheritance and learning in development of birdsong
- behaviour of birdsong = partly innate and partly learned
- innateness of some notes allows for birds to recognise other birds from within same species
- birds reared in isolation produce songs and calls similar to that of their species- shows that some of these behaviours must be innate
- but, some calls are learned from parents eg. particular mating calls or when defending their territory
- quality of birdsong is used to attract mates by demonstrating healthy sound of their voice, making them more desirable
- birds can often have regional dialects
- observed by studies of birds of same species but in different locations - - evidence that birdsong in these cases must be learned behaviour, than innate
109
Neurotransmitters
chemical substances that are able to transmit signals from one cell to another
110
When are neurotransmitters released?
- neurotransmitter is released when depolarisation of presynaptic neuron reaches synapse
- neurotransmitter depolarises postsynaptic neuron as it binds to receptors in the membrane
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Excitatory neurotransmitters
- excite postsynaptic neuron for longer periods of time
- allow for action potentials triggered by depolarisation
- produces a stimulatory response
112
Inhibitory neurotransmitters
- inhibit formation of action potentials in postsynaptic neuron- by opening ion channels for chloride and potassium ions
- makes it more difficult for neuron to reach threshold potential of around -50mV
- nerve impulses will be inhibited
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Summation
- sometimes hundreds of presynaptic neurons form a synapse w/ same postsynaptic neuron
- requires more than one excitatory neurotransmitter to trigger an action potential
- this accumulative effect of multiple releases= summation
- summation combines effects of excitatory and inhibitory neurotransmitters
114
Formation of an action potential
Depends on summation of neurotransmitters
- and whether threshold potential is reached
- just a single excitatory potential wouldn't be enough to reach threshold level of action potential
- combined efforts of many postsynaptic potentials add up to reach required threshold
115
Slow-acting neurotransmitters
control efficiency of fast-acting neurotransmitters
- take hundreds of milliseconds- several minutes, to effect postsynaptic neuron
- important role in memory and learning
- trigger release of secondary messengers in postsynaptic neuron
- these secondary messengers promote synaptic transmission by increasing no. of receptors in postsynaptic membrane
- they're also able to increase rate of ion movements after a neurotransmitter binds
- secondary messengers persist for several days- allows them to maximise impact on synaptic plasticity
- hence, memory and learning are enhanced and developed by changing neurons caused by slow-acting neurotransmitters.
- eg. dopamine, serotonin
116
Fast-acting neurotransmitters
bind w/ receptors of postsynaptic membrane less than a millisecond after arrival of an action potential at presynaptic membrane
- secondary messengers released in postsynaptic neurons begin sequence of complicated processes
- they regulate fast-acting synaptic transmission
- allows action of fast-acting neurotransmitters to be controlled for long periods of time
- eg. glutamate, acetylcholine
117
Psychoactive drugs
affect mind by altering performance of synapses in the brain
- some are excitatory and amplify postsynaptic transmission
- other drugs are inhibitory, they reduce postsynaptic transmission
118
Examples of excitatory drugs
1. Nicotine - found in cigarettes, obtained from Nicotiana tabacum
2. Cocaine - obtained from Erythroxylum coca.
3. Amphetamines - artificially synthesised compounds
119
Examples of inhibitory drugs
1. Benzodiazepines - known as GABA, includes Valium, synthesised artificially
2. Ethanol (alcohol) - obtained by fermentation using yeast.
3. Tetrahydrocannabinol (THC) - obtained from Cannabis sativa
120
Effect of two stimulants on nervous system
1. Pramipexole: - causes similar effect to dopamine
- binds to dopamine receptors in postsynaptic membrane
- Used to treat Parkinson's disease in its early stages
- Can be used as an anti-depressant
2. Cocaine
- acts on dopamine synapses
- Blocks dopamine re-uptake transporters
- causes a buildup of dopamine in synaptic cleft
- Postsynaptic neuron is continuously excited, resulting in a state of euphoria
121
Effects of two sedatives on nervous system
1. Diazepam
- binds to GABA (inhibitory neurotransmitter)
- causing chloride channels to open and hyperpolarisation and inhibition of nerve impulses
- reduces anxiety, panic attacks, and insomnia
2. Tetrahydrocannabinol (THC)
- present in cannabis
- binds to receptors in presynaptic membranes of hippocampus, cerebellum, and cerebral hemispheres
- inhibits release of excitatory neurotransmitters
- Impairs short-term memory, causes intoxication and stimulates appetite
122
MDMA
- recreational drug
| - increases activity of neurotransmitters in the brain
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Serotonin
- a neurotransmitter
- regulates mood, sleep, pain and appetite
- large amounts of serotonin released depletes brain of dopamine
- causes negative behavioural effects that can last for several days
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Dopamine
- helps to regulate emotion and feelings of pleasure
125
Stimulants
- drugs that increase alertness, raise heart rate, increase blood pressure, and make people more energetic and euphoric
- stimulation matches that of sympathetic nervous system
- body believes that it's been naturally stimulated
- eg. caffeine, cocaine, amphetamines
126
Drug addiction
- both physiological and psychological
- brain and the body desire drugs that alter the mind
- compulsion to consume the drugs is difficult to overcome
- side-effects of withdrawing from them can be painful
127
Causes of addiction
1. Genetic disposition
- genes are believed to be more prevalent in people w/ addictions
- suggests that they're more susceptible to addiction
2. Social environment
- peer pressure and social deprivation contribute to whether some people are more likely to try drugs in the first place
- Drugs may be more available and acceptable in some areas or countries.
3. Dopamine secretion
- addictive drugs cause high levels of dopamine secretion for long periods of time, making the user feel euphoric
- feeling motivates user to repeatedly seek more drugs, often increasing dosage each time in search of a bigger 'high'
128
Anaesthetics
drugs that cause a reversible loss of sensation and consciousness
- interfere w/ neural transmission between areas of sensory perception and CNS
129
General anaesthetic
- causes total loss of consciousness
- makes patient unaware of any pain or sensation during surgery
- must be administered by a highly trained anaesthetist
130
Local anaesthetic
- causes a localised loss of sensation for a short period of time
- inhibits sodium channel in membranes of nerve cells
- mechanism prevents conduction of electrical impulse along neuron
- this anaesthetic can be used anywhere on body but is often used for teeth and gums
131
Spinal block
administered to prevent pain but keep the patient breathing and aware of the procedure
- local anaesthetic is injected into space around spinal cord so pain can't be felt below the waist
132
Pain sensation
- skin is cut, burned by heat, or affected by chemical substances
- pain receptors in skin detect this stimulus
- send message to CNS
- pain sensation is sent to sensory area of cerebral cortex
133
Endorphins
- neuropeptides produced in pituitary gland
- natural painkillers
- able to prevent sensation of pain
- bind to specific receptors in pathway that links pain and pain perception
- inhibits transmission of electrical impulse and prevents pain being felt.
134
Ethology
scientific study of the behaviour of animals in their natural habitat
135
Anthropomorphism
attribution of human characteristics to an animal or an object
136
Courtship
- animals have many rituals to attract a mate
- if animal can't do so, it won't produce any offspring and characteristics won't be passed on
- this means only the most desirable features of certain animals are inherited by next generation
137
Attracting a mate
- animals attempt to show themselves off as being attractive, strong and desirable w/ exaggerated traits
- eg. extravagant plumage in birds, mating calls, and courtship dances.
- these traits are reproduced, so traits have become more exaggerated and evident in birds
- instead of competing w/ each other, some species of birds collaborate together to attract a mate eg. blue manakin
138
Natural selection
- favour specific types of behaviour
- survival of the fittest
- behaviours that give animals best chances of survival and reproduction persist from generation to generation
- frequency of animal behaviour may increase within a population as it adapts to change in environmental surroundings
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Learned behaviour
Learned behaviour that conveys a competitive advantage will be copied and spread throughout population
140
Altruism
when behaviour of an animal benefits another animal but decreases animal's own chances of survival
141
Reciprocal altruism
- a behaviour where an organism acts in a manner that reduces its health and fitness
- while increasing health and fitness of another organism, w/ expectation that other organism will return favour later
142
Blackcaps and natural selection
- have been able to adapt innate behaviour by natural selection
- traditionally migrate between northern Europe and Spain and Portugal in summer so they can claim best breeding territories
- breeding takes place during winter in northern Europe (usually Germany)
- Later, it was noticed that blackcaps were beginning to winter in Great Britain
- previously rare behaviour- was linked to climate change in Britain
Advantage to blackcaps:
- had a much shorter journey
- territorial advantage over other blackcaps
- earlier arrival in Germany meant birds could lay more eggs
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Vampire bats and altruism
- eg. of how natural selection favours altruistic behaviour
- vampire bats feed on blood of mammals
- but if food can't be found then a fellow bat will regurgitate some of their own food- reciprocal altruism
- bats recognise that they may also need food in future
- will be more likely to benefit from reciprocal altruism of others in group
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Shore crabs
- feed on mussels, use their strong claws to crack them open
- they'll only attack mussels of an optimum size to ensure most profitable energy yield from prey.
- eat more of the mussels that provide greatest energy gain
- mussels that provide most energy are those around 15 - 25 mm length
- benefit of this foraging behaviour = allows predator to catch prey that'll provide them w/ more energy
- also helps gather information about availability of other prey sizes
- so, if optimum sizes aren't available they can still eat smaller or larger prey
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Coho salmon
- exhibit behaviour that maximises chances of survival and reproduction
- found along west coast of North America
- breed in rivers before spending majority of their life in the ocean
- coho salmon will return to rivers to breed
Two main breeding strategies between males are:
1. Jacks (small adult male)
- hide before sneaking out to mate w/ an available female
2. Hooknoses (large adult males)
- fight other hooknoses to access females and deposit their sperm over eggs
- success of two males is cyclical
- jacks are more successful, leading to greater competition
- allows hooknoses to be more successful w/ their aggressive breeding strategy
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Oestrus
Male cubs typically leave their pride between 2-3 years
- when they develop into adults, males breed by taking over another pride and killing all the cubs
- female lions usually protect their cubs from the attack but are often unsuccessful
- Once attack is complete, female will mate w/ male lion as she comes into oestrus more quickly.
Synchronisation of oestrus in female lions that belong to same pride
- is triggered by innate release of pheromones
- this increases chances of cub survival and reproduction
- means that all the females are suckling at the same time and can suckle each other's cubs
- When cubs grow up at the same age, male lions can work together to gain new territories and breed
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Learned behaviour
competitive advantage gained by learned behaviour is more likely to be copied by others in the population
- leads to behaviour spreading faster than innate behaviour
- innate behaviour must be passed from one generation to the next by natural selection
NB/learned behaviour can be lost more rapidly than innate behaviour
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Blue tits
- blue tits feeding on cream from milk bottles is an example of how learned behaviour may be developed or lost
- milk bottles were left outside houses
- blue tits pecked tops of the bottles to get to the cream
- behaviour was copied by blue tits and led to the spread of the behaviour across Europe
- but, blue tits don't seem to feed on cream from milk bottles anymore
- due to less milk being delivered and aluminium foil tops being replaced by plastic tops
- learned behaviour has been eliminated as quickly as it was originally developed.
