Nervous Coordination Flashcards
What are the differences between the nervous and endocrine system
Nervous system is very specific, short lasting and fast compared to slow, wide spread and long lasting
Nervous system uses electrical impulses produced via neurones
Endocrine uses hormones in blood plasma produced by Glands
Nervous system is temporary and reversabke
Endocrine can be permanent and Irreversible
How are neurones adapted to function
Highly specialised
Carry nerve impulses rapidly
What are the main features of a neuron
Cell body Axon Schwann cells Nodes of ranvier Dendrons Dendrites Synaptic knobs
Describe the cell body
Main part of cell
Contains all organelles of normal cell
Large RER
Describe Dendrons and Dendrites
Dendrons are extensions of cell body
Dendrites are sub divisions of Dendrons
Carry impulses towards body
Describe the Axon
Long extension from cell body carrying impulses away from cell body
Describe Schwann cells
Cells that wrap around the axon
Myelin in cell membrane create myelin sheath
Electrical insulation and phagocytosis to remove cell debry
Describe Nodes of ranvier
Gaps along axon where there is no myelin sheath
Describe the structure of a motor neurone
Long axon
Many Dendrites
Describe the structure of a sensory neuron
One dendron and axon with cell body in the middle
Describe the structure of an intermediate neurone
Many short Dendrons and one short axon
Many Dendrites
How is resting potential established in a neurone
The sodium potassium pump actively transports 3 na+ out and 2K+ in.
All Na+ voltage gated channels are closed and some K+ voltage gated channels are open.
Some K+ Diffuse out (hyperpolarisation) and then back in
Until equilibrium so membrane is polarised
How is an action potential propagated
Stimulus exceeds threshold producing AP
Some Na+ voltage gated channels open causing Na+ to diffuse in down electrochemical gradient increasing potential inside axon
This causes more Na+ channels to open further down, positive feedback.
More Na+ enter so more positive
How is the membrane repolarised
Na+ voltage gated channels close preventing Na+ entering. Pump removes them
K+ voltage gated channels open allowing K+ to diffuse out down electrochemical gradient.
Positive feedback causes more K+ channels to open so more K+ leave (hyperpolarisation)
K+ Diffuse back in
K+ close so equilibrium is reached so membrane is polarised
Describe the all or nothing principle
If generator potential exceeds threshold then AP generated
Is threshold not exceeded nothing happens
How to magnitudes of stimuli differ
Frequency of AP (size is the same)
Different neurones have different thresholds
What factors affect the speed of an ap
Temp
Myelination
Diameter of axon
Describe how Myelination affects the speed of an ap
Myelination acts as an electrical insulator as ions can’t diffuse across lipids
Saltatory conduction occurs so less membrane surface is need to be de polarised = faster as less diffusion occurs
Describe how temp affects the speed of an ap
Higher temp means ions have more kinetic energy so more faster = faster diffusion = faster conduction of AP
Increased rate of Respiration = Increased ATP production = more pumping of ions so repolarised quicker
Describe how axon diameter affects the speed of an ap
Larger diameter = smaller sa:vol
Less leakage of ions = ap and resting potential easier to maintain
Describe and explain the subcellular structure of a Synaptic knob
Many mitochondria and SER to produce neurotransmitter
What is the name for a synapse that uses acetylcholine
Cholinergic synapse
Describe the transmission of an ap using acetyl choline
Ap reaches synatipc knob causing ca2+ channels to open
Ca2+ diffuses in via facilitated diffusion
Causes vesicles containing acetylcholine diffuse towards and fuse with presynaptic membrane (exocytosis)
Acetylcholine diffuses across Synaptic cleft and binds to receptors on sodium channels on postsynatic membrane causing them to open
Na+ Diffuse into post Synaptic neurone causing de polarisation
How is the synapse reset for a new ap
Ca2+ actively Transported out of Synaptic knob
Acetylcholinesterase releases and Hydrolyses acetylcholine into acetyl and choline
Diffuse across Synaptic cleft and into synatipc knob
Reformed at SER
Why is summation necessary
Prevents overstimulation of nervous system
Effects of stimulus is magnified
Synapses act as barriers
What are the two types of summation
Temporal and spatial
Describe temporal summation
One neurone releases many bursts of neurotransmitter in a short amount of Time
Describe spatial summation
More than one neurone releases low concentration of neurotransmitter which together lead to a high conc of neurotransmitter
What are the types of Synapses
Excitatory and inhibitory
Describe what an inhibitory synapse is
A synapse that makes an ap less likely on the postsynatic membrane
Describe what an excitatory synapse is
A synapse that makes an ap more likely
How do inhibitory Synapses work
Produced neurotransmitters that either open K+ channels or Cl- channels
Cause K+ to diffuse out and Cl- in
Inside becomes less positive making it harder for membrane to be de polarised
Counteracts Na+ diffusing in
