Neuronal Communication Flashcards
why are communication systems needed in multicellular organisims
for animals and plants to respond to changes in internal and external environments
coordinate activities of different organs
cell signalling/communication
what is cell signalling
when a cell releases a chemical which has an effect on its target cells
trasnferring signals between neurones at synapses
neurotransmitter
electircal
transferring signals across large distances
hormones chemical
what is the purpose of a neurone
to transmit electrical impulses around the body so that organisms can respond to changes in its external and internal environment
what are the three types of neurones
sensory
relay
motor
structure sensory and function
one long dendron and a short axon
transport to relay motor or brain
relay neurone s and f
many dendrites
transmit impulses between neurones
motor s and f
transmit impulses from relay and sensory to effectors such as muscles or glands
many dendrites
structure of a neurone
cell body surrounded by vytoplasm
dendrons which divide into dendrites which is responsible for transmitting electrical impulses to the cell body
axons which transmit electrons away
what happens in myelinated neurones
electrical impulses jump from node to node as it travels along the neurone
what covers the axon and what is it made up of
myelinated sheath
schwaan cell
what does the mylein sheath act as
an electrical insulator
it allows myelinated nuerones to conduct electrical impulses faster than non myelinated nuerones
features of a sensory receptor
detect range of different stimulus and convert stimulus into a nerve impulse.
what is a nerve impulse known as
a generator potential
features of a sensory receptor
specific to a single type of a stimulus
act as a transducer - convert stimulus into a nerve impulse
what are the 4 types of sensory receptors
chemoreceptor - detect chemicals
thermoreceptor - detect heat
mechanoreceptor - detect pressure
photoreceptor - detect light
how do sensory receptors act as a transducer
they detect stimuli and receptors convert the stimulus into a nerve impulse known as a generator potential
what is a pacinian corpuscle
sensory receptors which detect mechanical pressure
what do they act as
mechanoreceptors
features of a pacinian corpuscle
single sensory neurones surrounded by layer of tissues which is separated by gel forming an onion like structure.
it has layers of connective tissues separated by gel
stretch mediated sodium ion channels which open when pressue is applied - allows influx of sodium ion
explain how Pacinian corpuscle converts mechanical pressure into a nerve impulse
- pressure is applied, corpuscle changes shape causing membrane to stretch
- membrane stretches, sodium ion channels widen allowing sodium ions to diffuse into the neurone.
- influx of sodium ions causes the membrane to be depolarised resulting in a generator potential
- generator potential creates an action potential which passes along sensory neurones
what is resting potential
polarised
-70mv
why does resting potential occur
it occurs due to the movement of sodium and potassium ions across the axon membrane.
what is action potential
w
potential difference becomes depolarisedhen a stimulus is detected by a sensory receptor, the stimulus reverses the charge.
action potential process
- neurone has resting potential
- stimulus triggers sodium voltaged gates ion channels to open, membrane more permeable to NA so it diffuses in down the electrochemical gradient making it less negative
- charge change causes the na channels to open so more na can diffuse in
- voltage gated sodium ion channels close and potassium ion channels open and the membrane is more permeable to potassium
- potassium diffuse out the axon down the electrochemical gradient making axon more negative
- potassium diffuse put and axon is more negative hyperpolarisation occurs
propogation
salatory conduction
all or nothing principle
what is a synapse and what are impulses transmitted as
junction between two neurones
neurotransmitters
what is the synaptic cleft
it seperates axon of one neurone from the dendrite of the next neurone
presynaptic neurone
neurone along which impulse has arrived
postsynaptic neurone
neurone which receives the neurotransmitter
synaptic knob
it is the swollen aend of presynapric neurone which contains many mitochondria
synaptic vesicle
vesicle containing neurotransmitters which fuse with presynaptic membrane and release contents into synaptic cleft
neurotransmitter receptor
receptor which neurotransmitter binds to in postsynaptic membrane
types of neurone transmitter
- inhibitory - results in hyperpolarisation of the postsynaptic membrane preventing action potential
- excitatory - results in depolarisation of postsynaptic neurone
synaptic transmission
- action potential reaches end of presynaptic neurone
- depolarisation of the presynaptic membrane causes calcium ion channels to open
- calcium ions diffuse into presynaptic knob
- causes the synaptic vesicle containg neurotransmitter to fuse with presynaptic membrane
- neurotransmitter diffuses across the synaptic cleft and binds with the receptor on the postsynaptic membrane
- causes sodium ion channels to open
- sodium ions diffuse into postsynaptic neurone
- triggers an action potential
what is the transmission across a cholinergic synapse
- action potential at the end of the presynaptic neurone causing the calcium ion channels to open and calcium to open
- influx of calcium into the presynaptic neurone causing synaptic cleft to fuse with the presynaptic membrane releasing acetylcholine into the cleft
- acetylcholine fuse with receptor site on sodium ion channels in the postsynaptic neurone membrane causing sodium ion channels to open and allowing sodium ions to diffuse in
- influx of sodium ions generates an action otential in postsynaptic neurone
- acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid which diffuses back across the synpatic cleft into the presynaptic neurone
- atp is released combining ethanoic acid and choline
what is the role of a synapse
to ensure that synapse are unidirectional
allow impulses to be transmitted
what is spatial summation
temporal summation
synaptic divergence
synaptic convergence
what is the nervous system organised as
- cns
2.pns
how is it further organised
- stomatic nervous system
which is the consious control - autonomic nervous system
subconcious control
how is the autonomic nervous system separated into
- parasympathetic - relaxing responses
- sympathetic -
flight or fight
what is the brain protected by
skull
cerebrum
voluntary actions
receives sensory information
cerebellum
unconcious functions
receives info from organs
medulla oblongata
autonomic control
hypothalamus
regulatory centre for temp and water balance
ptuitary gland
anterior - 6 hormones involved in reproduction and growth hormones
posterior - stores and releases hormones
reflex arc
receptor
sensory neurone
relay neurone
motor neurone
what are the 3 types of muscles
skeletal
caridac
involuntary
what is skeletal muscles made up of
- muscle fibres- sarcolemeres
2- myofibrils which are made up of actin and mysoin
what is actin
myosin
thinner
thicker
what is the sliding filament model
During contraction. Myosin filaments will pull the actin filaments towards the centre of the sarcomere. This will result in the light band becoming narrower and the Z line moving closer and Hzone becoming narrower.
structure of myosin
globular hinged heads allowing them to move back and forth
binding sites for atp
myosin filaments
structure of actin
binding sites for myosin heads
which is blocked by trpomyosin when relaxed
how does muscle contraction occur at the neuromuscular junction
Muscle contraction is triggered when an action potential arrives at a neuromuscular junction (where motor neurone and muscle fibres meet)
When an action potential reaches the neuromuscular junction, it stimulates the calcium ion channels to open. This causes the calcium ions to diffuse from synapse to the synaptic knob which causes the synaptic vesicles to fuse with the presynaptic membrane. Acetylcholine is released into the synaptic cleft via exocytosis and diffuse across the synapse where it will bind to the receptors on the postsynaptic membrane causing sodium ion channels to open resulting in depolarization. Acetylcholine is broken by acetylcholinesterase into choline and ethanoic acid preventing overstimulation in the muscle. Choline and ethanoic acid diffuse back into the neurone and recombine with acetylcholine using atp by the mitochondria ( this is transmission across a cholinergic synapse)
how is energy suuplied
hydrolysis of atp into adp and phosphate
what is the sliding filament theory
SLIDING FILAMENT THEORY
1.Tropomyosin prevents myosin head from attaching to the binding site of the actin molecule
2.Calcium ions are released from the endoplasmic reticulum causing tropomyosin molecules to pull away from the binding site on the actin molecule
3.Myosin head now attaches to the binding site on the actin filament
4.This causes the head of the myosin to change angle moving the actin filament along and releasing ADP
5.ATP molecules fix to myosin causing it to detach from the actin filament
6.Hydrolysis of ATP to ADP by myosin provides energy for the myosin head to resume its normal position
7.The head of the myosin reattaches to its binding site further along the actin filament and the cycle repeats.
ways in which atp is generated
Aerobic respiration
Atp is regenerated by ADP during oxidative phosphorylation
Anaerobic respiration
Atp made by glycolysis
Creatine phosphatE
ADP is phosphorylated
