Topic 7 and 8 for Snab Biology Unit 5

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Action potentials -An action potential initiates an electrical Pupil reflex Detecting stimuli- photoreceptors
Types of neurone
-From resting potential (-70 mV) current Motor- Bright light sympathetic Cones- colour vision; rods- monochrome
depolarisation occurs when a -Depolarisation spreads to the adjacent CNS to effector reflex circular muscles Rods in dark:
stimulus causes influx of Na ions region Sensory- contract, radial muscles +
- Na enters and leaves cell
-At +40 mV (action potential), This is called a wave of depolarisation and Sensory cells to CNS relax -It is depolarised
+ +
Na channels close and K is faster in myelinated neurones, as Relay- Dim light -Neurotransmitter released and inhibits
channels open impulse `jumps'. Within the CNS parasympathetic reflex bipolar cell
-K ions leave- repolarisation Schwann cell node of Ranvier radial muscles contract, -No action potential so no information
-When too many K ions leave, Synapses circular muscles relax to optic nerve
the membrane is hyperpolarised, -An action potential at the presynaptic Rods in light:
then resting potential is restored. 2+
neurone causes Ca ions to enter Neurones are myelinated for insulation and to speed Critical window
-Rhodopsin is broken down into retinal
-Vesicles containing neurotransmitters up nerve impulses-which travel by saltatory conduction Exposure to stimulus is
and opsin
Excitatory- causes an action release their contents into synaptic cleft needed to develop fully- + +
-Na channels closed, but Na continues
potential in the next neurone by exocytosis demonstrated by Hubel and
to leave cell
Inhibitory- prevents an action -Neurotransmitters bind to receptors on Wiesel's experiments
potential- possibly by increasing postsynaptic neurone membrane -No neurotransmitter released
threshold for an action potential Nature vs. Nurture debate
-This triggers an action potential (if -Action potential in bipolar cell so visual
Topic 8 -Newborn babies
excitatory) information travels via optic nerve
Brain imaging -The neurotransmitter is either broken Grey Matter -Brain damage cases
CT scans: -Twin studies
down in synaptic cleft or reuptaken
-X-rays, frozen moment picture, -Cross cultural studies Phytochromes
detect brain disease, not very -In normal sunlight, more red light than far
The Brain Parietal lobe-
detailed Genetic Modification red- more PFR
MRI: Frontal lobe- Microorganisms -In dark, PFR converts into PR
-Magnetic field + radio waves, thinking -Inserting gene for required trait The Eye -PFR needed to form leaves and chlorophyll
detect soft tissue, can obtain 3D (e.g. insulin production) into a -Phytochromes allow plants to detect day
image, more detailed plasmid of a bacterium length; controlling germination and flowering
-Used to detect tumours, -Extracting insulin
strokes, brain injuries Occipital Plants
-Plants use growth substances such as IAA
fMRI: Temporal lobe- lobe- sight -Artificial selection
-Plant shoots are positively phototropic,
-Lots of pictures observing brain hearing -Transgenic plants- infect with
Cerebellum- so more IAA on shaded side, to promote
function over time, modified bacterium, remove
coordinates movement cell elongation, and then plant grows
deoxyhaemoglobin absorbs and tumour, plants grown from tumour
towards light
emits signal, whilst will contain desired trait
Hypothalamus- thermoregulation Animals
oxyhaemoglobin does not Issues with genetic modification
Medulla oblongata- cardiovascular -Transgenic animals produce certain
-Active brain regions light up -Antibiotic resistance, harmful products, virus
and ventilation centre proteins in milk
-Only used for normal brain transmission from animals to humans
function -Ill health caused by eating/using GMOs
Parkinson's disease Depression
-Caused by lack of dopamine -Caused by lack of serotonin Human Genome Project Nervous control Hormonal control
Investigating habituation (ignoring -Symptoms: tremors, stiff muscles,
-Symptoms- sadness, -Can find genes for drug targets Travel as nerve impulses Travel in blood
unimportant stimuli) in sea slug poor balance and slow movement
anxiety, hopelessness -Provide tailored dosage and drugs Fast acting Slower acting
-Gill withdraws when siphon is -Treatments: L-dopa which can
cross blood-brain barrier and helps -Treatments- SSRIs which -More insight into genetic/ environmental Short-term changes Long-term changes
stimulated then comes back out
remaining cells produce dopamine, inhibit serotonin reuptake risk factors Action potential in specific Blood travels to all cells but
-Repeat at regular intervals
dopamine agonists which mimic -Ethical considerations if there is a DNA cells hormones affect target cells
-Siphon returns more quickly or
effects of dopamine Ecstasy is harmful due to its database: breaches of confidentiality etc
stops withdrawing Local response Widespread effect
effects on serotonin levels

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Effects of exercise Muscles bring about movement at joints and work in Sliding Filament Theory
Disabilities and injuries in sport
antagonistic pairs -Impulse at neuromuscular junction
-Prosthetic limbs 2+
Too much exercise Too little exercise Extensors contract to extend; flexors contract to flex -Ca released; attaches to troponin
-Knee joint replacements
-Then tropomyosin moves, exposing
Wear and tear of joints Obesity -Repairing ligaments by keyhole
Ligaments- bone to bone; Tendons-muscle to bone myosin binding site on actin filament
Compromised immunity CHD surgery
-Myosin head binds…read more



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Lucy Sargent

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