U1T3 - Keywords (2) Flashcards Preview

CCEA A2 Biology Unit 1 > U1T3 - Keywords (2) > Flashcards

Flashcards in U1T3 - Keywords (2) Deck (107):
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Nervous System

Consists of CNS + many peripheral nerves.

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CNS

Brain + spinal cord. Integrates incoming info from peripheral nerves + coordinates effective response.

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Centrons

Contains nucleus, mitochondria + other organelles + Nissi's granules.

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Dendrons

Fine threads of cytoplasmic threads which deliver impulses towards cell body in neurone.

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Axons

Fine cytoplasmic threads which carry impulses away from cell body in neurone. Terminate in synaptic bulbs.

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Sensory neurones

Have dendrons + axons with similar long length so cell body quite central. Carry impulses from receptors to CNS.

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Motor neurones

Long axons with dendrites. Carry impulses from CNS to effectors.

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Dendrites

Short dendrons

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Relay neurones

Shorter overall, shorter dendrons + axons. Connect neurones within CNS.

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Myelinated Neurone

Neurone wrapped in Schwann cells, created electrically insulating myelin sheath rich in lipid myelin. Between each SC, nodes of Ranvier exposed. Speed of impulse transmission greatly increased as local current only exists as nodes of Ranvier.

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Nodes of Ranvier

Small patch of neurone membrane exposed in myelinated neurone.

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Potential Difference

Difference in charge between 2 regions (e.g. inside + outside cell).

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Polarised Cells

Cells with potential difference across membrane.

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Neurones

Have excess of positively charged ions surrounding them, resulting in potential diff of -70mV. More + charged cells outside cell + cell contains many proteins which are - charged. Have cell body + extended nerve fibre.

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Resting Potential

PD across CSM. (Neurones polarsed as electrochemical gradient across CSM) When neruones have excess of + charged ions around them, resulting in pot diff of -70mV. More + charged cells outside cell + cell contains many proteins which are - charged. Maintained as CSM mostly impermeable to flow of sodium ions when not conducting impulse.

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Threshold Potential

-55mV in mammals. Is met when enough transmembrane proteins + positively charged ions open.

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Action Potential

When PD across membrane reaches peak of around +40mV after stimulus applied and threshold potential reached and neurone becomes depolarised.

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Sub Threshold Stimulus

A stimulus which doesn't cause threshold potential to be reached and action potential isn't fired. Display all or nothing principle in this case.

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All or Nothing Principle

Action potential always peaks at same value regardless of stimulus intensity. More intense stimuli result in more frequency firing of action potentials.

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Repolarisation

After depolarisation, neurone actively re-establishes it's resting potential using this. Positively charged ions both diffuse and are actively pumped out of neurone into surrounding fluid.

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Refractory Period

Period of time taken for repolarisation. Neurone can't be stimulated during this time. Limits speed at which action potential fires + so allows coordinator (CNS) to detect each action potential as discrete event. Also ensures impulses travel in 1 direction.

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Impulse

Propogation of action potentials along axon by flow of current in a series of localised currents.

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Voltage Gated Ion Channels.

Transmembrane proteins. Able to sense localised changes in charge + respond by changing shape so positively charged ions flow into cell, resulting in depolarisation, making action potential more likely.

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Saltatory Conduction

Due to fast transmission speed of myelinated neurone, localised currents jump from one node to the next, myelin sheath prevents depolarisation in myelinated zones, hence why it must jump to nodes of Ranvier so fast.

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Synapse

Junction between axon of 1 neurone + dendrite of adjacent as they aren't in physical contact. Electrical signals can jump across this gap. Includes synaptic bulb, synaptic cleft + post-synaptic neurone. Filter out low level background stimuli to prevent overload + overstimulation.

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Tropism

Growth response

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Acetylcholine

Primary neurotransmitter in CNS. Acts to make depolarisation more likely, found in excitatory synapses as its actions results in EPSP. Broken down into choline + ethanoic acid by ecetylcholinesterase.

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EPSPs

Excitatory Post Synaptic Potential.

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GABA

Neurotransmitter. Associated with IPSPs. Released at inhibitory synapses. Hyperpolarises neurone membrane resulting in lower PD across membrane which reduces likelihood of action potential so more + ions must move in to reach threshold potential. Reduces anxiety.

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IPSPs

Inhibitory Post Synaptic Potentials. Central in reducing anxiety through reducing num of impulses which reach brain + reducing possibility of reflex actions being prevented.

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Ciliary Muscles

Ring of muscle surrounding lens. Contains muscular ring of ciliary muscle around eye. Suspensory ligaments extend from ciliary body + hold lens in place. Adjusts lens shape to focus light rays.

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Lens

Flexible fluid filled sac. Transparent biconcave structure with refractive properties which refracts light + focuses light rays on retina.

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Refracted

Bent.

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Retina

Inner layer of eyeball containing light sensitive receptor cells (rods + cones), bipolar cells + ganglion cells.

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Visual Transduction

The process of converting light energy into an energy potential occurring.

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Bleaching

When light strikes rhodopsin, causing it to break down into retinal + opsin.

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Retinal Convergence

Many rods can synapse onto 1 bipolar sense resulting in high rod sensitivity so summation can occur.

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Summation

Small amount of neurotransmitter released from few rod cells can be added together to open enough ion channels in bipolar cell to form action potential. Explains why rods provide decreased visual acuity as image formed is due to patch of cells being stimulated rather than single cell. Provides complexity + flexibility of synapses.

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Light Adapted Eye

When rhodopsin almost entirely broken down as cones used for vision in bright light.

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Dark Adapted Eye

After 30 mins in dark room so rhodopsin has reformed to allow rods to be sensitive.

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Binocular Vision

Use of 2 eyes to form image, allows better distance perception + stereoscopic vision so brain can form 3D image. Distance between eyes + placement of head on animal determine visual field. Prey animals have eyes on side of head to have wide vision for predators.

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Sarcolemma

Outer membrane of muscle fibre. Here, synapses of motor neurones make contact in motor end plates. Also forms T-tubules.

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T-tubules

Deep infoldings at intervals along length of muscle fibre by sarcolemma.

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Sarcoplasmic Reticulum

Network of membranes within muscle fibre which act as storage site for calcium ions.

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Sarcoplasm

Cytoplasm of muscle fibre.

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Myofibrils

Functional units of muscle. Contraction occurs by shorting these. Made of sarcomeres in repeating pattern along length of myofibril.

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Myosin

Thicker fibrous protein with protruding heads at intervals along length. Forms denser striations.

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Actin

Finer fibrous protein with binding sites for myosin heads along length. Form lighter regions between them.

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Sarcomere

Unit of repeating pattern of actin, myosin + structures they attach to.

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Nerves

Bundles of neurones grouped together, protected within outer protective layer. Can contain sensory neurones only, motor neurones only or mix of both.

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Nervous Control

Involves receptors + effectors with interlinking coordinator.

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Receptors

Found in eyes + ears etc. Each sensitive to particular stimulus.

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Stimulus

Something we hear, see or smell.

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Effectors

Parts of body which produce response (muscles)

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Nissi's Granules

Large groups of ribosomes.

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Threshold Stimulus

Level of stimulus necessary before action potential produced.

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Zone of Depolarisation

Part of neurone where polarity reversed.

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Pre-synaptic neurone

Neurone which releases transmitter. Specialised. End thickened into synaptic bulb + synpatic vesicles.

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Post-synaptic neurone

Neurone which receives diffusing neurotransmitter. Specialised. Membrane contains receptors complementary to type of neurotransmitter involved in the synapse.

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Synaptic Bulb

Contain large numbers of mitochondria necessary to create neurotransmitter.

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Synaptic Vesicles

Where neurotransmitter stored.

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Synapse Fatigue

When too many impulses pass along same neurone in short period of time, exhausting neurotransmitter supply more quickly than can be built up.

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Integration

Coordination of processes. Aided by summation.

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Excitatry Synapses

When neurotransmitter chemicals released with function of causing EPSP + subsequent action potential/

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Inhibitory Synapses

Make more difficult for synaptic transmission to occur using preventative neurotransmitter which lead to influx of - ions in PoS membrane so inside of membrane more negative, creating IPSP. This hyperpolarisation makes difficult to create EPSP.

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Noradrenaline

Results in EPSPs. Typically used in involuntary nervous control.

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Nicotine

Stimulates release of acetylcholine + other neurotransmitters making action potentials more likely. Allows Na ions to flood cell.

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Curare

Blocks receptors at neuromuscular junctions preventing synaptic transmission causing loss of muscle function.

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Opiods

Blocks CA channels in pre synaptic neurone so less transmitter substance released + action potentials less likely. Can provide pain relief by reducing impulses from pain receptors.

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Conjunctiva

Thin transparent membrane covering cornea which protects it from damage.

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Sclera

Tough opaque connective tissue covering eye, replaced by transparent cornea at front. Protects against damage + site of attachment of eye muscles.

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Cornea

Front transparent part of sclera where most refraction of light occurs.

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Aqueous Humour

Transparent watery fluid between cornea + lens which maintains shape of front part of eye.

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Iris

Muscular layer with circular + radial muscles, contains light absorbing pigment. Adjusts pupil size to control amount of light entering eye.

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Pupil

Gap within iris where light reaches lens + enters centre of eye.

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Suspensory Ligaments

Ligaments that connect ciliary body to lens. Transfer tension in eyeball wall to make lens thinner, important for distance vision. Tough + flexible but don't stretch, allowing the lens to thin when they're pulled.

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Vitreous Humour

Transparent, jelly like material between lens + back of eye which maintains shape of rear part of eye + supports lens.

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Fovea

Region in centre of retina which is rich in cones + doesn't contain rods. Gives clearest daylight colour vision in eye.

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Choroid

Layer of pigmented cells between retina + sclera which contain blood vessels supplying retina + prevent reflection of light back through eye.

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Optic Nerve

Bundle of sensory nerve fibres that leave retina + transmit impulses from retina to brain.

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Blind Spot

Part of retina where sensory neurones that unite to form optic nerve leaving eye. Contain no light sensitive cells so not sensitive to light.

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Accommodation

Adjustment of lens thickness to ensure light rays are focused on retina, irrespective of angle of light rays reaching eye. Example of reflex action.

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Photoreceptors

Photosensitive cells. Light energy brings about change in level of polarisation of membranes. e.g. Rods + cones which as act as transducers converting light stimulus to nerve impulse in associated neurones.

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Rhodopsin

Light sensitive pigment which is packed into array of membranes in outer part of rod cell. Formed from protein opsin, combined with light absorbing compound retinal from vitamin A. When stimulated by light, breaks into components, changing membrane potential of cell + creating generator potential. . If threshold potential reached, becomes depolarised + action potential created.

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Trichromatic theory of colour vision

Blue, green + red.

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Generator Potential

Degree of depolarisation stimulated receptor can produce. Action potential only produced if it reaches threshold level.

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High Visual Acuity

Each cone cell can synapse individually with its own bipolar neurone so can provide own discrete image in vision which allows them to provide highly precise colour vision of high red allowing distance perception.

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Sensitivity

Ability to operate in low light intensities.

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Skeletal Muscle

Muscle under conscious/voluntary control. Alternating pattern of myosin + actin forms striated pattern.

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M-Line

Thin disc linking myosin filaments which it runs perp to.

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Z-Line

Thin disc linking actin filaments. Connective tissue.

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A-Band

Ansiotropic Band. Part of sarcomere containing myosin. Includes areas where actin penetrates between myosin filaments. Darker.

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I-Band

Isotropic Band. Part of sarcomere containing just actin. Lighter

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H-Zone

Zone in centre of A-Band where only myosin present.

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Sliding Filament Mechanism

The mechanism of muscle contraction. How myosin + actin filaments slide past each other, reducing overall length of sarcomere.

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Myelin Sheath

Insulating covering that surrounds axon with layers of myelin.

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Depolarisation

Loss of diff in charge between inside + outside of plasma membrane.

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Propogation

Transmission of motiom in certan direction/through medium.

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Iodopsin

Photosensitive violet pigment in retinal cones, formed from vitamin A.

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Stereoscopic Vision

Single perception of slightly diff image from each eye, resulting in depth perception.

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Rods

Specialised photoreceptor in retina that provides side vision + night vision.

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Cones

Photoreceptors in retina. Responsible for colour vision.

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Muscle Fibre

Muscle cell, especially cylindrical, multinucleate cells that make up skeletal muscles.

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Muscle

Bundle of fibrous tissue that can contract, producing movement.

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Tropomyosin

Protein involved in muscle contraction.

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BCC

Bright, circular, contracted.

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Alcohol

Hyperpolarises neurone, makes action potentials less likely.