U1T3 - Keywords (2) Flashcards
Animals
Nervous System
Consists of CNS + many peripheral nerves.
CNS
Brain + spinal cord. Integrates incoming info from peripheral nerves + coordinates effective response.
Centrons
Contains nucleus, mitochondria + other organelles + Nissi’s granules.
Dendrons
Fine threads of cytoplasmic threads which deliver impulses towards cell body in neurone.
Axons
Fine cytoplasmic threads which carry impulses away from cell body in neurone. Terminate in synaptic bulbs.
Sensory neurones
Have dendrons + axons with similar long length so cell body quite central. Carry impulses from receptors to CNS.
Motor neurones
Long axons with dendrites. Carry impulses from CNS to effectors.
Dendrites
Short dendrons
Relay neurones
Shorter overall, shorter dendrons + axons. Connect neurones within CNS.
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.
Nodes of Ranvier
Small patch of neurone membrane exposed in myelinated neurone.
Potential Difference
Difference in charge between 2 regions (e.g. inside + outside cell).
Polarised Cells
Cells with potential difference across membrane.
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.
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.
Threshold Potential
-55mV in mammals. Is met when enough transmembrane proteins + positively charged ions open.
Action Potential
When PD across membrane reaches peak of around +40mV after stimulus applied and threshold potential reached and neurone becomes depolarised.
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.
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.
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.
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.
Impulse
Propogation of action potentials along axon by flow of current in a series of localised currents.
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.
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.
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.
Tropism
Growth response
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.
EPSPs
Excitatory Post Synaptic Potential.
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.
IPSPs
Inhibitory Post Synaptic Potentials. Central in reducing anxiety through reducing num of impulses which reach brain + reducing possibility of reflex actions being prevented.
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.
Lens
Flexible fluid filled sac. Transparent biconcave structure with refractive properties which refracts light + focuses light rays on retina.
Refracted
Bent.
Retina
Inner layer of eyeball containing light sensitive receptor cells (rods + cones), bipolar cells + ganglion cells.
Visual Transduction
The process of converting light energy into an energy potential occurring.
Bleaching
When light strikes rhodopsin, causing it to break down into retinal + opsin.
Retinal Convergence
Many rods can synapse onto 1 bipolar sense resulting in high rod sensitivity so summation can occur.
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.
Light Adapted Eye
When rhodopsin almost entirely broken down as cones used for vision in bright light.
Dark Adapted Eye
After 30 mins in dark room so rhodopsin has reformed to allow rods to be sensitive.
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.
Sarcolemma
Outer membrane of muscle fibre. Here, synapses of motor neurones make contact in motor end plates. Also forms T-tubules.
T-tubules
Deep infoldings at intervals along length of muscle fibre by sarcolemma.
Sarcoplasmic Reticulum
Network of membranes within muscle fibre which act as storage site for calcium ions.
Sarcoplasm
Cytoplasm of muscle fibre.
Myofibrils
Functional units of muscle. Contraction occurs by shorting these. Made of sarcomeres in repeating pattern along length of myofibril.
Myosin
Thicker fibrous protein with protruding heads at intervals along length. Forms denser striations.
Actin
Finer fibrous protein with binding sites for myosin heads along length. Form lighter regions between them.
Sarcomere
Unit of repeating pattern of actin, myosin + structures they attach to.
Nerves
Bundles of neurones grouped together, protected within outer protective layer. Can contain sensory neurones only, motor neurones only or mix of both.
Nervous Control
Involves receptors + effectors with interlinking coordinator.
Receptors
Found in eyes + ears etc. Each sensitive to particular stimulus.
Stimulus
Something we hear, see or smell.
Effectors
Parts of body which produce response (muscles)
Nissi’s Granules
Large groups of ribosomes.
Threshold Stimulus
Level of stimulus necessary before action potential produced.
Zone of Depolarisation
Part of neurone where polarity reversed.
Pre-synaptic neurone
Neurone which releases transmitter. Specialised. End thickened into synaptic bulb + synpatic vesicles.
Post-synaptic neurone
Neurone which receives diffusing neurotransmitter. Specialised. Membrane contains receptors complementary to type of neurotransmitter involved in the synapse.
Synaptic Bulb
Contain large numbers of mitochondria necessary to create neurotransmitter.
Synaptic Vesicles
Where neurotransmitter stored.
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.
Integration
Coordination of processes. Aided by summation.
Excitatry Synapses
When neurotransmitter chemicals released with function of causing EPSP + subsequent action potential/
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.
Noradrenaline
Results in EPSPs. Typically used in involuntary nervous control.
Nicotine
Stimulates release of acetylcholine + other neurotransmitters making action potentials more likely. Allows Na ions to flood cell.
Curare
Blocks receptors at neuromuscular junctions preventing synaptic transmission causing loss of muscle function.
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.
Conjunctiva
Thin transparent membrane covering cornea which protects it from damage.
Sclera
Tough opaque connective tissue covering eye, replaced by transparent cornea at front. Protects against damage + site of attachment of eye muscles.
Cornea
Front transparent part of sclera where most refraction of light occurs.
Aqueous Humour
Transparent watery fluid between cornea + lens which maintains shape of front part of eye.
Iris
Muscular layer with circular + radial muscles, contains light absorbing pigment. Adjusts pupil size to control amount of light entering eye.
Pupil
Gap within iris where light reaches lens + enters centre of eye.
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.
Vitreous Humour
Transparent, jelly like material between lens + back of eye which maintains shape of rear part of eye + supports lens.
Fovea
Region in centre of retina which is rich in cones + doesn’t contain rods. Gives clearest daylight colour vision in eye.
Choroid
Layer of pigmented cells between retina + sclera which contain blood vessels supplying retina + prevent reflection of light back through eye.
Optic Nerve
Bundle of sensory nerve fibres that leave retina + transmit impulses from retina to brain.
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.
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.
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.
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.
Trichromatic theory of colour vision
Blue, green + red.
Generator Potential
Degree of depolarisation stimulated receptor can produce. Action potential only produced if it reaches threshold level.
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.
Sensitivity
Ability to operate in low light intensities.
Skeletal Muscle
Muscle under conscious/voluntary control. Alternating pattern of myosin + actin forms striated pattern.
M-Line
Thin disc linking myosin filaments which it runs perp to.
Z-Line
Thin disc linking actin filaments. Connective tissue.
A-Band
Ansiotropic Band. Part of sarcomere containing myosin. Includes areas where actin penetrates between myosin filaments. Darker.
I-Band
Isotropic Band. Part of sarcomere containing just actin. Lighter
H-Zone
Zone in centre of A-Band where only myosin present.
Sliding Filament Mechanism
The mechanism of muscle contraction. How myosin + actin filaments slide past each other, reducing overall length of sarcomere.
Myelin Sheath
Insulating covering that surrounds axon with layers of myelin.
Depolarisation
Loss of diff in charge between inside + outside of plasma membrane.
Propogation
Transmission of motiom in certan direction/through medium.
Iodopsin
Photosensitive violet pigment in retinal cones, formed from vitamin A.
Stereoscopic Vision
Single perception of slightly diff image from each eye, resulting in depth perception.
Rods
Specialised photoreceptor in retina that provides side vision + night vision.
Cones
Photoreceptors in retina. Responsible for colour vision.
Muscle Fibre
Muscle cell, especially cylindrical, multinucleate cells that make up skeletal muscles.
Muscle
Bundle of fibrous tissue that can contract, producing movement.
Tropomyosin
Protein involved in muscle contraction.
BCC
Bright, circular, contracted.
Alcohol
Hyperpolarises neurone, makes action potentials less likely.
