9.2

Increases amount of neurotransmitter synthesised Increases release of neurotransmitter from vesicles at presynaptic membrane Binds to post synaptic receptors and activates them or increases the effect of the normal neurotransmitter Prevents the degradation of neurotransmitter by enzymes or prevents reuptake into presynaptic knob

Blocks the synthesis of neurotransmitter Causes neurotransmitter to leak from vesicles and be destroyed by enzymes Prevents the release of neurotransmitter from vesicles Blocks the receptors and prevents neurotransmitter binding

Mimics effect of acetylcholine and binds to specific acetylcholine receptors in the post synaptic membranes known as nicotine receptors

Triggers action potential in post synaptic neurone then receptor remains unresponsive to more stimulation for some time. Triggers release of dopamine - associated with pleasurable sensations

Causes raised heart rate and blood pressure Dopamine release - pleasurable effect High addictive Stimulating at low effects, can be lethal at high effects

Used as local anaesthetic - used by dentists for invasive surgery’s Block voltage-gated sodium channels

Prevents the production of an action potential in sensory nerves and so preventing you from feeling pain Also used to prevent some heart arrhythmias where it works in the same way - blocks sodium channels, raising depolarisation threshold

No feeling of pain in injected area

Toxic substance and often fatal in snake bites Binds reversibly to acetylcholine receptors in post synaptic membranes and neurotransmitter junctions

Prevents transmission or impulses across synapses, including the neuromuscular junctions between motor neurones and muscles

Muscles are not stimulated to contract and gradually the person affected becomes paralysed When toxin reaches the muscles involved in breathing it causes death In low concentrations however it can relax muscles of trachea and bronchi in severe asthma attacks and so saves lives

Converts an environmental stimulus eg light, heat into nerve impulse Achieved by the opening of Na+ channels in the receptor This alters polarity of a receptor and may trigger an action potential which will travel along the nerve to CNS

Converts light into a pattern of nerve impulses Transduction takes place in the retina by a layer of photosensitive cells in the back of the eye Rods and cones are attached to nerves

Membrane shelves lined with rhodopsin Outer segment Inner segment - many mitochondria Outer limiting membrane Nucleus Synaptic body

Only provide black and white images High in number Multiple rod cells are connected to one bipolar cell Retinal convergence allows a generator potential to be reached with low levels of stimulus (low light intensity) A generator potential is created by the breakdown of the pigment rhodopsin Rhodopsin is broken down in low light conditions As multiple rod cells share the same bipolar cell and sensory neurone only one impulse is generated

Integrations of cell membranes that from a stack of membrane disks where photopigments exist as transmembrane proteins Outer segment Inner segment - mitochondria Nucleus Synaptic terminal that forms a synapse with a neuron

3 types of cone cell Each has different form of iodopsin as they respond to different wavelengths of light Cone cells are frequently individually connected to a single bipolar cell No summation is possible so are larger stimulus is required to reach generator potential Iodopsin requires a high level of energy from a high light intensity to be broken down As cone cells are separate they are able to distinguish between points close together providing good visual activity

Have one axon and a dendrite extending from the soma (cell body)

In the bipolar cell with they’re connected to Because there are multiple rods connected to one bipolar neuron much more likely for threshold velue to be reached

Part of retina which light is focused upon Received greatest intensity of light Therefore, cone cells (but not rod cells) are found here More rod cells are found at the edges of the fovea (lower light intensity)

Formed from opsin and retinal Retinal exists as 2 different isomers: cis-retinal and trans-retinal In the dark all retinal is in the cis form When a photon of light hits the rhodopsin, converts it from cis to trans form This changes the shape of the retinal and puts strain in the bonding between opsin and retinal, breaking up the molecule Known as ‘bleaching’

Rod cells are usually quite permeable to sodium ions When rhodopsin is bleached, causes the Na ion channels to close, making it less permeable to sodium However, sodium pump continues to work and so sodium ions are removed from the cell This makes the inside of the rod cell more negative than normal This hyperpolarisation is known as the ‘generator potential’

Nervous control - using baroreceptors and chemoreceptors Hormonal control