Nervous coordination Flashcards
How does a membrane remain at a resting potential?
The sodium potassium ion pump uses energy from ATP to actively transport 3 Na+ out for every 2K+ in.
Name the features of an axon membrane
Voltage gated ion channels
Potassium, sodiu ion pump
What happens to generate an action potential?
A stimulus arrives causing Na+ channels to open. Na+ diffuses in to the axon down the electrochemical gradient.
The membrane is now depolarised.
As sodium ion channels close potassium channels open, decreasing potential difference.
What happens when a stimulus is big enough?
Na+ channels open, as Na+ diffuses in more voltage sensitive ion channels open. This is an action potential as the positive feedback causes more depolarisation.
What happens when a stimulus is not big enough?
Only a few Na+ channels open. Not enough Na+ diffuses in to the axon to exceed the threshold. Called a failed stimulus.
What happens during repolarisation?
Sodium ion channels open and sodium ions diffuse in . At 30mV voltage gated sodium ion channels close and potassium ion channels open. Potassium ions diffuse out causing the potential difference alters.
Name factors effecting nervous conduction
Temperature
Myelin sheath
Axon diameter (bigger = less resistance)
Discuss nerve impulse propagation
At the leading edge of the action potential, Na+ diffuse in. Na+ are attracted to the less negative area of the axon in front of the leading edge. This causes Na+ channels further along to open, a localised circuit is established.
Describe synaptic transmission
A wave of depolarisation reaches the pre synaptic knob. Ca+ channels open and Ca+ diffuses in. Vesicles containing acetylcholine fuse to the pre synaptic membrane. Acetylcholine diffuses into the synaptic cleft and it binds to receptors on the post synaptic membrane. The receptors act as Na+ channels, Na+ diffuses through. When the threshold is exceeded an action potential is generated down the post synaptic nuerone.
How is acetylcholine reuptook after synaptic transmission?
An enzyme called acetylcholinesterase hydrolyses acetyl and choline. Using energy from ATP an acetyl and choline pump reuptakes the acetyl and choline.
Some may be reuptook from the vesicle.
What is spatial summation?
Adding together of action potentials from several neurones to exceed a threshold.
What is temporal summation?
Adding together of action potentials over a period of time from one neurone.
What does the neurotransmitter GABA do?
It binds to other receptors
Causes chloride ions to diffuse in
This causes hyper polarisation
An inhibitory response
Name some ways drugs can affect synaptic transmission
Same shape as the neurotransmitter and increase amount of receptors activated (agonists).
Block the receptor so they can’t be activated and fewer receptors are (activated antagonists)
Inhibit the enzymes breaking down the neurotransmitter
Stimulate the release of neurotransmitter
Inhibit the release of a neurotransmitter
What are the there types of muscle?
Skeletal (striated muscle)
Cardiac
Smooth
What are the characteristics of slow twitch muscle?
Type of striated muscle Endurance Aerobic High quantities of mitochondria High quantities of myoglobin High affinity for oxygen at low partial pressures Darker in colour
What are the characteristics of fast twitch muscle?
Type of striated muscle Explosive movements Short bursts Anaerobic Light colour
Name the properties of a muscle cell
Elongated
The membrane is called the sarcolemma
The sarcoplasm is a specialised cytoplasm for contraction
Sarcoplasm contains units called myofibrils
(repeating units of actin and myosin)
Internal membranes called sarcoplasmic reticulum run through sarcoplasm
Where are the following on a myofibril... I band A band Z line M line H zone
I band= bands containing actin filaments
A band= myosin filaments (some overlapped by actin)
Z line= end of each sarcomere
M line= middle of myosin
H zone= only containing myosin
Outline how muscular contraction occurs
An action potential arrives at the motor neurone
Acetyl choline is released
An action potential is generated through the t tubules
Causes the sarcoplasmic reticulum to release calcium ions
Trypomyosin moves of of binding sites
Myosin heads form bridges with actin
They rotate through a 45 degree angle
Actin and myosin filaments slide and the Z line shortens
ATP binds to myosin heads causing them to detach and recock
They attach further down the filament later
What happens to calcium ions after an action potential?
Calcium ions move from binding sites via active transport back to the sarcoplasmic reticulum
Tropomyosin molecules move back and block the actin-myosin binding sites again
Sarcomere lengthens
