biology topic 7+ 8

Myogenic

heart's ability to contract without external stimulation

test for safe dosage

test drug on healthy individuals and cell cultures

test on individuals with disease

gradual increase dose to determine safe dosage with least extreme side effects

Importance of cardiac output

increase supply of oxygenated blood to muscles

to allow aerobic respiration

provide energy and oxygen to meet demands

how adrenaline affect heart rate

adrenaline is carried in the blood made from adrenal glands on top of kidneys

acts on so sinoatrial node (SAN)

increase frequency of impulse produced by SAN

increase rate of heart contractions

effects of beta blockers

larger doses, greater decrease of heart rate

reduce heart rate reduces cardiac output

reducing supply of blood to muscle

human/animal controls

age, size, sex

body mass, level of fitness

exposure to same environmental conditions

PET

radioactive glucose

detects production of gamma rays

produces 3D image

Habituation

decreasing responsiveness result of repeated stimulation

transmission of impulses

Ca2+ ion enter presynaptic neurone resulting in neurotransmitters visible fuse with presynaptic membrane

neurotransmitter diffuses across synaptic cleft and synapse

neurotransmitter bind to receptors on post-synaptic membrane

Na+ ion diffuse into post-synaptic neurone leaving to polarisation and action potential

reduced/repeated stimulation on synapse

reduce permeability of presynaptic membrane to Ca2+ ions, fewer Ca2+ ions enter

fewer vesicles fuse with presynaptic membrane

less neurotransmitter bind to post-synaptic membrane

action potential may not occur / membrane may not be polarised

visual cortex development via visual stimulation

ocular domination column develop in visual cortex

neurone form synapse with these column cells

action potential along neurone requires to strengthen connection

stimulation in critical period needed to form connections in visual cortex

fMRI

detects blood flow in brain

increase in brain activity lead to increase demand for oxygenated blood flow for aerobic respiration

oxyhemoglobin absorbs fewer radiowaves

fMRI detects areas of less signal absorbed

risk of CT

radiation

can cause mutation in DNA muscle fibres via x-ray