15.Nervous Coordination And Muscles Flashcards
(47 cards)
What are the two forms of coordination in animals
Nervous system
Hormonal system
How does hormonal system form coordination
Produces chemicals transported in blood plasma to target cells
Target cells have specific cell surface membrane receptors
Change in conc of hormone stimulates them
Results in slower, less specific form of communication
Response long lasting and wide spread
Comparison of hormonal and nervous system
Communication by : Chemicals / nerve impulses
Transmission by : Bloody system / neurones
Transmission is : Relatively slow / very rapid
Travel to : all body, only target cells respond/ specific parts
Response is : Widespread / localised
Response is : Slow / fast
Response is : Long lasting / short lived
Effect is : Permanent irreversible / temporary reversible
What makes up motor neurone
Cell Body- contains cell organelles, high amount of rough ER
Dendrons - extensions of body subdivide into dendrites
Axon - sing long fibre carries impulse away from cell body
Schwann cells- surround axon, protect it, provide electrical insulation, carry out phagocytosis and nerve regeneration
Myelin sheath - rich lipid, if have it called myelinated neurone
Node of ranvier - constrictions between adjacent Schwann cells no myelin sheath
What are the three types of neurone
Sensory - transmit from receptors to intermediate/motor neurone, one long dendron takes impulse to cell body, then axon take away
Intermediate/relay - transmit impulses between neurones
Motors- transmit from intermediate or relay to effector such as gland or muscle, long axon and many short dendrites
What can a nerve impulse be defined as
Self propagating wave of electrical activity that travels along axon membrane, it’s a temporary reversal of the electrical potential difference across the axon membrane.
What is happening when the axon is at resting potential (what happens to maintain/achieve it)
- Phospholipid bilayer prevents sodium ions and potassium ions diffusing across it
- channel proteins called sodium potassium pump actively transport 3 sodium ions out of axon, and two potassium ions in to axon
- creates a electrochemical gradient as more positive ions outside so outside is positively charged
What are the two types of skeletal muscle
Fast twitch
Slow twitch
What are the characteristics of fast twitch fibres
- strength
- rapid movement
- sprinter
- Anaerobic
- fewer blood vessels
- small amount energy released quickly
- less mitochondria
- Less myoglobin
What are the characteristic of flow twitch fibres
- stamina
- endurance
- marathon runner
- aerobic
- many blood vessels
- large amount energy released slowly
- more mitochondria
- more myoglobin
What is the sliding filament theory
- The process where actin and myosin filaments slide last one another during muscle contraction
- myosin filaments pull the actin filaments
- the Z plates pulled closer together
- I band becomes narrower
- H zone become narrower
- sarcomere shortens
- A band stays same width- myosin length doesn’t change
What’s the structure of myosin
- Two proteins
- Fibrous protein arranged into filament made of several hundred molecules from the “tail”
- globular proteins formed into two bulbous structures at one end form the “head”
- thicker
What’s the structure of actin
- Globular protein
- molecules arranged into 2 long chains that are twisted around one another to form helical strand
- tropomyosin forms long thin threads that are wound round the actin filaments
-thinner
What’s a neuromuscular junction
-Point where motor neurone meets skeletal muscle fibre, there’s many along muscle fibre
What’s the advantage of many neuromuscular junctions
-muscle contraction is simultaneous
-muscle contraction is rapid and powerful
-motor unit is when all muscle fibres supplies by single motor neurone act together as single functional unit
-
What’s the structure of skeletal muscle
- Individual muscles are made up of millions of tiny muscle fibres called myofibrils
- collectively are very powerful
- muscle composed of smaller units bundled into progressively larger units
- separate cells have fused together into muscle fibres, share nuclei and sarcoplasm.
Comparison of neuromuscular and cholinergic synapse
- Excitatory / excitatory or inhibitory
- Neurone to muscle / neurone to neurone
- only motor neurone / motor,sensory, intermediate
- action pot ends here / new action pot produced
- acetylcholine binds to receptors on muscle fibre / acetylcholine binds to receptor on post synaptic neurone
What happens during muscle stimulation (start of muscle contraction)
- Action potential reaches neuromuscular junctions simultaneously
- causes calcium ion protein channels to open and calcium ions diffuse into synaptic knob
- calcium ions cause synaptic vesicles to fuse with presynaptic membrane and release acetylcholine into synaptic cleft
- acetylcholine Diffuses across synaptic cleft, bind with receptors on muscle cell causing it to depolarise
What happens during muscle contraction
- Action pot travels down T tubules into the fibre and branches out throughout sarcoplasm
- tubules in contact with endoplasmic reticulum of muscle which has actively transported Ca2+ from cytoplasm-low conc in cytoplasms
- act pot opens calcium ion voltages gated channels, ca2+ diffuses out and into muscle cytoplasm
- calcium ions bind to troponin, which causes the tropomyosin to unblock the binding sites on the actin filament
- Myosin heads bind to actin filament, to form cross bridge
- ADP dissociates and the myosin head changes angle forming power stroke and pulling the actin filament
- ATP attaches to myosin head, calcium ions activate enzyme ATPase which hydrolysed ATP to ADP causing it to detach and resets back to original shape/angle
- if calcium conc stays high process repeats
- c
What’s the action potential
- when stimulus is sufficient size and detected by receptor, energy causes temporary reversal of charges
- negative charge of inside -65V becomes +40-known as action potential
- part of axon is depolarised
- depolarisation occurs because channels in axon membrane change shape, open voltage gated channels.
What’s the process of a nerve impulse
- resting pot (k+ voltage gated channels open, na+ closed)
- energy of stimulus causes some sodium voltage gated channels in axon membrane to open, na+ diffuse into axon along electro chemical gradient, positively charged, trigger reversal of potential difference -depolarisation
- na+ diffuse into axon, increase potential so more channels open (voltage gated)
- action potential at +40V, sodium channels close
- k+ open electrical gradient that prevents further outward movement is reversed, k+ diffuse rapidly out
- outward diffusion of k+ causes temporary overshoot of electrical gradient, inside is more negative than usual (hyperpolarisation) k+/na+ pump moves k+ in and na+ out, testing potential re-establishes
How does a action potential move along an unmyelinated axon
Propagated
- resting potential
- stimulus causes influx of na+ ions
- reversal of charge on axon membrane, depolarisation
- localised electrical currents established by the influx of sodium ions causes opening of sodium voltages gated channels as sodium diffuses up along axon depolarising next section
- behind the depolarising region, sodium channels shut and potassium channels open, potassium leave axon along electrochemical grad
- outward movement of k+ lowers potential in axon, repolarisation of axon
- resting potential established by k+/na+ pump
The passage of action potential along myelinated axon
- Action potentials only occur at nodes of ranvier
- localised circuits go from node to node, so action potentials jump from node to node
- still has depolarisation and resting potentials and depolarisations
What factors affect, the speed of action potential travelling
- Myelin-electrical insulator prevents action potentials forming so jumps node to node increases conductance
- diameter of axon-greater the diameter the fast the conductance, due to less leakage of pins from larger axon
- temperature-affects rate of diffusion of ions, higher temp faster nerve impulse, energy for active transport come fro respiration, controlled by enzymes, above certain temp denatured
