Topic 8- Responding to Environment, The Brain, Behaviour + Disease Flashcards
1
Q
Describe the coordination of response
A
- Stimuli= change in environment detected by specialised receptor cells located in sense organs
- send signals via coordination centres (nervous/hormonal systems) to spinal cord or brain
- sent onto effectors (parts of body which respond)= muscles or glands
2
Q
Describe the Nervous system
A
- central= brain and spinal cord process info
- peripheral= all the nerves in the body
- information is sent in the form of electrical impulses whcih pass along neurones (nerves are bundles of neurones)
3
Q
Describe the general structure and function of neurones
A
- specialised cells that carry impulses around body and connect receptors w/ CNS + effectors w/ CNS
- all contain:
1. axon= long fibre
2. cell body= contains nucleus and cellular structures
3. axon terminal= end of axon w/ many nerve endings to connect + receive impulses from other neurones
4
Q
Describe the structure + function of motor neurones
A
- carry impulses from CNS to effector
- highly branched dendrites carry impulses from CNS to its cell body
- one long axon which carries impulses from cell body to effector cells at axon terminal
5
Q
Describe the structure and function of sensory neurones
A
- sends impulses from receptors to CNS
- one long dendron carries impulses from receptor cells to cell body (in the middle of neurone)
- short axon carries nerve impulses from cell body to the CNS
6
Q
Describe the structure and function of Relay Neurones
A
- found w/in CNS to connect sensory neurone to motor neurone
- this allows for the bypassing of the CNS to motor neurone so it is much quicker (reflex arc)= this protects from damage
- many short dendrites carry nerve impulses from sensory neurones to cell body
- an axon carries nerv impulses from cell body to motor neurone
7
Q
Describe the eye’s response to bright light
A
- bright light is a parsympathetic stimulus (body is in composed state)
- photoreceptors in eye detect bright light and send impulse along sensory neurones to CNS
- CNS processes info and sends impulse along motor neurone to effectors
- circular muscles are stimulated and contract while radial muscles relax, causing pupil to constrict
8
Q
Describe the eye’s response to dim light
A
- dim light is sympathetic stimuli (body prepares for fight or flight)
- light receptors in eyes detect lack of light and sends impulse along sensory neurone to CNS
- CNS processes the information and sends impulse via motor neurones to effectors
- radial muscles in iris are stimulated and the contract while circular muscles contract
- response is the dilation of the pupils so mor light
9
Q
What is resting potential?
A
- in a neurones resting state (when not stimulated), the outside of the membrane is more positive than the inside
- p.d is around -70mV
- it i smaintained by sodium-potassium pumps and differences in membrane permeability
10
Q
Describe the maintanance of resting potential
A
- Sodium-potassium pumps are present in cell surface membrane of neurones
- they use active transport to move 3 Na+ ions out of the neurone and 2K+ ions in (needs ATP)
- creates Na+ electrochemical gradient as more positive Na+ outside than inside - though Sodium-potassium pumps move K+ in, the membrane is permeable to them so they can also diffuse back out through K+ ion channels
- Na+ cannot diffuse back in= results in more positive ions outside than inside
11
Q
Describe how an action potential occurs
A
- Stimulus excites a neurone and causes Na+ channels to open and Na+ diffuse into the neurone due to increased permeability
- This increases the potential difference inside the neurone and if threshold is reached (-55mV), then depolarisation occurs
- Depolarisation causes all voltage gated Na+ channels to open so more Na+ diffuse in, and the p.d is +30mV
- When +30mV reached, K+ channels open and Na+ channels close. K+ diffuse out so that p.d goes down to resting potential
- Hyperpolarisation occurs due to an overshoot of K+ leaving the neurone (K+ channels start to close) and p.d <-70mV
- Resting potential reached when ions reset as Na-K pump returns the p.d to normal
12
Q
Describe the Transmission along a neurone
A
- First action potential causes some Na+ to diffuse along axon and depolarises next section (wave of depolarisation along neurone)
- Any Na+ that diffuse backwards don’t depolarise it again because it has hyperpolarised and is in refractory period (can’t fire action potential)
13
Q
What is the refractory period and why is it good?
A
- when ion channels are recovering from depolarisation and can’t be opened
- acts as atime delay between one action potential and the next
makes sure the action potential travels in only one direction
14
Q
How do local anaesthetics work?
A
- bind to Na+ channels to prevent depolaristion as less Na+ can diffuse in to reach threshold for action potential
- no action potentials/ info. sent to brain so no pain
15
Q
Describe myelination and Saltatory Conduction
A
- myelin sheath made of Schwann cells and acts as an electrical insulator
- depolarisation can only occurat nodes of Ranvier (bare membrane)where Na+ can get through
- neurone’s cytoplasm conducts enough charge to depolarise next node + the impulse jumps
16
Q
Why are non-myelinated neurones slower?
A
- impulses travel as a wave so they have lover conduction velocity
17
Q
Describe Synaptic transmission
A
- action potential arrives at presynaptic neurone and causes voltage gated Ca2+ channels to open and Ca2+ diffuse in
- Ca2+ causes vescicles containing neurotransmitters to fuse with presynaptic membrane and release NT into syntaptic cleft (exocytosis)
- NT bind to receptors on postsynaptic membrane which causes Na+ channels to open and Na+ diffuses in
- Threshold is reached and depolarisation occurs (action potential)
- NT are broken down by enzymes or reuptaken= prevents response from continuing
18
Q
Define synaptic divergence
A
- when one neurone connnects to many neurones to spread/disperse information to different parts of body
19
Q
Define synaptic convergence
A
- when many neurones connect to one neurone to amplify information
20
Q
Define spatial summation
A
- when the effect of neurotransmitter released from many neurones is added together
21
Q
Define temporal summation
A
- when repeated stimulation of a presynaptic neurone causes all the neurotransmitter released to add together in effect
22
Q
Why does summation occur?
A
- a stimulus may be too weak to excite posynaptic neurone to threshold level as only a small amount of neurotransmitter is released
- summation helps stimulate an action potential
23
Q
Define habituation and why does it occur?
A
- reduced response to an unimportant stimulus due to repeated exposure over time
- responding to stimuli increases an animals chances of survival
- if the stimuli is not threatening, there is no need to waste energy to respond
24
Q
Describe how habituation works
A
- Nerve impulses are transmitted across synapses by neurotransmitters released due to Ca2+
- repeated exposure reduces the Ca2+ released into presynaptic knob so less neurotransmitter released from vesicles
- less NT bind with receptors on postsynaptic neurone and less Na+ channels open (threshold not reached)
- nerve impulse doesn’t reach effector
25
Q
Describe the habituation practical
A
- gently brush damp cotton bud onto skin of snail near tentacles and snail will withdraw head
- use stopwatch to time how long it takes for snail to fully extend tentacles
- repeat at regular intervals + record time
habituation will cause the time to decrease
26
Q
Describe Parkinson’s disease
A
- brain disorder affecting coordination and movement
- causes desturction of neurones that produce dopamine NT (involved in muscle control)
1. less dopamine binds to receptors on post = less Na+ channels open= less Na+ enter
2. fewer action potentials generated due to decreased depolarisation
symptoms: tremors/ slow movement
27
Q
Describe depression
A
- scientists believe there is a link between low levels of serotonin and depression (but correlation doesnt =causation)
- serotonin=NT that trransmits nerve impulses across synapses in parts of brain controlling mood
- antidepressents increase levels of serotonin like SSRIs selective serotonin reuptake inhibitors
28
Q
Describe why patients w/ Parkinson’s take L-dopa
A
- dopamine can’t be given as it can’t enter brain directly
- L-dopa has similar structure to dopamine and absorbed into brain
- converted into dopa-decarboxylase then levels of dopamine increase
more impulses transmitted across synapses in part of brain controlling movement (more control)
29
Q
Describe the effect of MDMA on serotonin levels
A
- increases levels of serotonin by:
1. inhibiting reuptake of serotonin back into presynaptic neurone by binding to reuptake proteins (blocks them)
2. also triggers release of serotonin
increase depolatisation in parts of brain controlling mood
:( post synaptic membrane become less responsive to serotonin/ loss of receptors on postsynaptic membrane
also depletes normal levels of serotonin
30
Q
What is personalised medicine?
A
- development of targeted drugs to treat a variety of human diseases in individuals with different genotypes
- uses Human Genome Project to create drugs based on identified proteins
- HGP also highlights common genetic variations as some variations can cause drugs to be less effective
31
Q
What are the moral, social and ethical issues around personalised medicine?
A
- creating these specific drugs is expensive so only the wealthy will be able to afford them]
- insurance companies may wrongfully discriminate if patient is unlikely to get better with treatment due to variation in genotype
- may be mentally damaging when revealing a drug won’t work for you
32
Q
What is the structure and function of the cerebrum?
A
- largest part of brain/ 2 halves called ceribral hemispheres
- thin outer layer called cerebral cortex which has lots of folds (large SA)= increase no. connections for more complex behaviour
- conscious activity (sppech, thinking, memory)
33
Q
Describe the structure and function of the hypothalamus
A
- just beneath middle of brain
- monitors blood as it flows through brain and responds by releasing hormones that control pituitary gland
- maintains body temp./endocrine functions automatically
34
Q
What is the structure and function of the cerebellum?
A
- underneath cerebrum at the back, has a folded cortex
- cordinates movement + balance
35
Q
What is the structure and function of the medulla oblongata?
A
- base of brain, above spinal cord
- automatically controls beathing + heart rate (contains CCC and repiritory centres)
36
Q
Describe CT scanning
A
- beam of X-rays aimed at patient + denser tissues absorb more X-ray (lighter region on scan)
- shows physical structures + visualisation of tissue damage
e.g bleed in brain shows up lighter
:(
- don’t show function but if there is damage it can be worked out
- can be dangerous as X-rays can cause mutations in DNA= cancerous
37
Q
Describe MRI scanning
A
- magnetic resonance imaging which uses magnetic and radio waves
- soft tissue seen clearly using MRI tumours are very visible
- higher resolution than CT scan and lower risk
:(
- don’t show funtion but can link damge with visible symptoms
- can interfere with medical devices
38
Q
Describe fMRI scanning
A
- functional magnetic resonance imaging
- shows changes in brain activity as they happen
- more oxygenated blood flows to active areas to supply neurones with O2 and oxygenated blood responds differently to magnetic field
39
Q
Describe PET scanning
A
- positron emission tomography
- radioactive tracer in body is absorbed by tissues + PET detects radioactivity + maps it (radioactively labelled glucose)
- glucose needed in more active parts of brain so more radioactivity detected in active parts
- both structure and function in real time
40
Q
What is the visual cortex?
A
- an area of the cerebral cortex at back of brain where it receives and processes visual information
41
Q
Describe the development of the visual cortex
A
- soon after birth, neurones of the VC begin to form synapses so visual information can be transferred + processed by VC
- Critical period= both eyes must be visually stimulated for neurones in VC to be organised correctly
- neurones organised into ocular dominace columns
- synapses that pass on impulses during critical period are strengthened and become permanent in VC
if no impulses received, synapses are lost and not reformed (if eyes aren’t stimilated) and can result in blindness
42
Q
Describe Hubel and Wiesel’s animal models to discover the structure of the VC
A
- stitched 1 eye of very young kittens for several months until they unstitched
- found that stitched eye was blind and that ocular dominance collumn of stitched eye were smaller than normal + non-stitched bigger than normal
- neurones in VC switched dominance= oc dom col of open eye had expanded to take over columns that weren’t stimulated
- did the same with dult cats but the stitched eye regained sight and oc dom col sizes stayed the same
- repeated with young and adult monkeys
showed critical period where eyes must be visually stimulated for VC to develop correctly
43
Q
Describe how we can use babies and humans to investigate development of VC
A
- if babies have cataracts they must have it removed asap as the eye will not be visually stimulated during critical period and could lead to blindness
- if adult develops cataracts, not urgent as sight will be regained due to critical period passing already (when removed, sight regained back to normal)
44
Q
What are the reasons FOR animals in research?
A
- only done when absolutely necessary and strict rules are followed
- cell cultures aren’t a true respresentation of how cells reat when surrounded by body tissues
- humans have greater right to life because we have more complex brains
- animals are similar to humans= leads to lots of medical breakthroughs
45
Q
What are the reasons AGAINST animals in research?
A
- animals are different so drug effects may be different
- can cause pain/distress
- alternatives like human cell cultures/computers
- animals have the right not to be experimented on
46
Q
What are the 2 types of photoreceptors?
A
- Rod Cells= sensitive to light intensity + detect presence + brightness of light
- allows black + white vision in bright + dim light - cone cells= sensitive to different wavelengths of visible light
- detect colour in bright light
47
Q
Describe what happens to light sensitive pigments when light falls on them
A
- bleaching occurs and causes a chemical change in photoreceptors= this generates an impulse
- Rhodopsin–> retinal + opsin
48
Q
Describe the action of rod cells in light
A
- rod cells are stimuilated + light energy breaks apart rhodopsin–> opsin + retinal
- opsin causes Na+ channels to close so they can’t diffuse back in (active transport of Na+ out of membrane still occurs)
- hyperpolarises inside of rod cell and stops releasing inhibitory neurotransmitter = no inhibition of bipolar neurone
- bipolar neurone depolarises and p.d reaches threshold and action potential transmits to brain
49
Q
describe the action of Rod cells in the dark
A
- rod cells aren’t stimulated and Na+ continues to actively transport out of cell and is able to diffuse back in (no opsin)
- insdie of the rod cell is only slightly more negative and the membrane is depolarised
- triggers release of inhibitory neurotransmitter to inhibit bipolar neurone
- bipolar neurone can’t fire action potential and no information to brain
50
Q
What is IAA?
A
- indoloacetic acid which is a type of auxin
- bring about responses like phototropism by alternig transcription of genes (affects growth of plant cels and elongation)
- produced in tips of shoots of plants (distributed by diffusion)
51
Q
Describe phytochrome
A
- type of photoreceptor so plants can detect light (controls seasonal flowering depending on how much daylight etc.)
- PR absorbs red light (660nm)
- PFR absorbs far red light (750nm)
52
Q
What happens to phytochrome in daylight and in the dark?
A
- more red light than far red so PR is converted to PFR more rapidly than the other way (PFR increases)
- PFR stimulates flowering in some plants
- PFR converts back to PR slowly in darkness and when nights are short there is no time for this to happen so PFR builds up = increased flowering
53
Q
What is genetic engineering?
A
- deliberately modify a specific characteristic of an organism by removing required gene from one organism and transferring it
54
Q
Describe GMO Microorganisms
A
- gene isolated w/ restriction enzymes
- copied using PCR + inserted into plasmids which act as vectors (carry genes into organism)
- Plasmid + gene joint by DNA ligase
- Transferred to microorganism + they are grown in large containers
- divide and produce lots of protein to be purified + used in drugs e.g human insulin to treat Type 1 diabetes
55
Q
Describe GMO plants
A
- after geen is in plasmid + transferred to bacteria, bacteria infects plant cell as a vector
- bacteria inserts gene into plant cell DNA + plant grows where ecah cell has the gene
- protein purified from plant tissues/ delivered to tissues by eating
56
Q
What’s a gene gun?
A
- tiny pellets coated with desired DNA fired into plant or animal cells
57
Q
Describe GMO animals
A
- gene for protein injected into nucleus of zygote (fertilised egg)
- implanted into adult animal which grows into animal cnotaining copy of gene in each cell
- protein produced from gene is purified
or gene gun
58
Q
What are the risks and benefits of drugs from GMOs?
A
:)
- crops can be modified to increase yield (decrease famine)
- crops can have pest resistance so less pesticides used (decrease environmental damage + costs)
- vaccines produced don’t need refrigeration
- treat disorders with human proteins so no reactions
:(
- we don’t know the long term impacts of using GMOs
- wrong to use animals for human benefit
- herbicide resistant crops may interbreed with weeds (resistant weeds)
