15. NERVOUS, COORDINATION & MUSCLE Flashcards
Name the two systems involved in coordination in animals.
Nervous system and Endocrine system.
Compare how each coordination system communicates
Nervous system - communicates by electrical impulses.
Endocrine system - communicates by hormones.
Compare transmission in both coordination systems
Nervous system - through neurones.
Endocrine system - through the bloodstream
Compare speed of transmission in both coordination systems
Nervous system - fast.
Endocrine system - slow
Compare which parts of the body each coordination system travels to
Nervous system - impulses only travel to specific parts of the body.
Endocrine system - travel to all parts of the body.
Compare the speed of responses in both coordination systems
Nervous system - Fast responses.
Endocrine system - Slow responses.
Compare how long-lasting the responses are in both coordination systems
Nervous system - short-lived responses
Endocrine system - long-lasting responses
Compare whether the responses are widespread or localised in each coordination system
Nervous system - localised responses.
Endocrine system - widespread responses
In which coordination system are the effects usually temporary and reversible?
Nervous system
In which coordination system are the effects usually permanent and irreversible?
Endocrine system
Name the structures the make up a mammalian neurone
A cell body, dendrons, an axon, a myelin sheath (made of schwann cells), and nodes of Ranvier.
What does the cell body contain?
Organelles including a nucleus and lots of of RER and Golgi Apparatus
Why does the cell body contain a large amount of RER?
For the production of neurotransmitters (proteins).
Why does the cell body contain a large amount of Golgi Apparatus?
To pack and transport neurotransmitter
Describe the function of dendrites
Transmit electrical impulses towards the cell body.
Describe the function of the axon
Transmit electrical impulses away from the cell body.
State what Schwann cells are.
They wrap themselves around the neurone many times to form the myelin sheath
State the function of the myelin sheath.
Provides electrical insulation to increase the speed of electrical impulse transmission
What are nodes of Ranvier?
Gaps between Schwann cells (where there are no myelin sheath)
Name 3 types of neurones.
Sensory, Motor and Intermediate (Relay) neurones.
State the function of a sensory neurone.
Transmit electrical impulses from a receptor to an intermediate neurone.
State the function of a motor neurone.
Transmit electrical impulses from an intermediate neurone to an effector.
State the function of the intermediate neurone.
Transmit impulses from sensory to motor neurones.
Name the two main effectors.
Muscles and glands.
Which neurone only exists in the CNS?
Intermediate (relay) neurone.
Why do intermediate neurones have many dendrites?
To coordinate electrical impulses from mulitple different sensory receptors.
Why does this neurone have many axon terminals?
To coordinate many different effectors.
What is potential difference?
The difference of electrical potential between two points.
Name the two ions involved creating potential difference over a neuronal membrane
Na+ and K+
Name the channel proteins involved in controlling Na+ and K+ ions movement.
Sodium-potassium pump, Voltage-gated K+ channel, Voltage-gated Na+ channel, Non voltage-gated K+ channels.
What is resting potential in mV?
-70mV
What do we mean when we day the resting potential ‘negative’?
The inside of the neurone is more negative than the outside.
Describe the function of the sodium-potassium pump
It actively transports 3 Na+ out of the axon, and actively transports 2 K+ into the axon
Which ion is the neuronal membrane more permeable to at rest?
K+
Describe how depolarisation occurs
Voltage-gated Na+ channels open and Na+ diffuse into the neurone.
Define threshold potential
The level of depolarisation required to initiate an action potential.
What is the threshold potential in mV?
-55mV
What happens if depolarisation does not reach threshold value?
No action potential is initiated so depolarisation remains local
If a depolarisation does reach threshold potential, what does it stimulate?
More Na+ channels to open
Define action potential.
The propogation of an electrical impulse down a neurone
What is the maximum depolarisation during an action potential in mV?
+40mV
Describe how repolarisation occurs
Voltage-gated Na+ channels close and voltage-gated K+ channels open. K+ diffuse out of the neurone.
Define hyperpolarisation
When the potential difference over the neurone membrane becomes more negative than resting potential (-70mV)
How is resting potential re-established?
The voltage-gated K+ channels close.
Define the All or Nothing Principle
The strength of an electrical impulse in a neurone is independent of the strength of a stimulus
Why are action potentials referred to as all or nothing?
Depolarisation needs to reach a threshold value before an action potential is propogated. The action potential always reaches +40mV.
How is the strength of a stimulus communicated?
By the frequency of the action potentials.
What happens to frequency of electrical impulses if the stimuli gets stronger?
The stronger the stimuli the higher the frequency of electrical impulses.
What is the refractory period?
This is the period of time after an action potential where no new action potential can be generated.
When will a section of a neurone go into the refractory period?
After repolarisation
How is the refractory period created?
Na+ voltage-gated channels are closed and inactive
A greater stimulation is required to generate an action potential in the refractory period. Why?
The membrane is hyperpolarised, so is more negative than at rest. Therefore a greater depolarisation is required to reach threshold potential.
Recall the three functions of the refractory period
Produces discrete impulses, ensures action potentials are unidirectional, and limits the number of action potentials
Recall the three factors that affect the speed of impulse transmission
Myelination, axon diameter and temperature
How does myelination affect the speed of nervous transmission?
It increases it
How does temperature affect the speed of a nerve impulse?
As temperature increases, the rate of impulse conduction increases
How does axon diameter affect the speed of a nerve impulse?
As axon diameter increases, the rate of impulse conduction increases
State the name given to conduction down a myelinated axon
Saltatory conduction.
Describe how saltatory conduction occurs
Depolarisation only occurs at nodes because the impulses jump from node to node
Why is conduction in non-myelinated neurones slower than in myelinated neurone
There is no saltatory conduction, therefore depolarisation occurs over the length of the membrane
How is the speed of an action potential transmitted in a myelinated axon compared to an unmyelinated axon?
It is faster in a myelinated axon compared to an unmyelinated axon.
How does diameter of the the axon affect the speed of the nerve impulse?
The greater the diameter of the axon, the faster the speed of conductance.
Why does increasing axon diameter increase speed of conductance?
Because there is less leakage of ions from a large axon.
How does temperature affect the speed of a nerve impulse?
The higher the temperature the faster the speed of the nerve impulse.
Why does increasing temperature increase the speed of nerve impulses?
Increasing temperature increases the speed of ion diffusion
What is a synapse?
The junction between two neurones.
What are the chemicals transmitted between synapses called?
Neurotransmitters
What is the neurone that releases the neurotransmitter called?
Pre-synaptic neurone
What is the swollen portion at the end of a neurone called?
The synaptic knob
What are neurotransmitters stored in?
Synaptic vesicles
What type of Na+ channel exists in the membrane of the post-synpatic knob?
Ligand-gated Na+ channels
What causes calcium ions to diffuse into the pre-synaptic knob?
Depolarisation of the membrane / an action potential
What does the influx of calcium ions into the pre-synaptic knob cause?
Exocytosis of the neurotransmitter into the synpatic cleft
How does the neurotransmitter travel across the synaptic cleft?
Diffusion
What happens to the neurotransmitter molecules once they reach the post-synaptic membrane?
They bind to the ligand-gated channels in the post synaptic membrane
Name the two types of neutrotransmitter
Excitatory and inhibitory
Name an excitatory neurotransmitter.
Acetylcholine
Describe how the release of an excitatory neurotransmitter would stimulate a post-synpatic neurone
They stimulate more Na+ channels to open, causing Na+ to diffuse into the neurone, depolarising the post-synaptic membrane
Do excitatory neurotransmitters change the membrane potential towards or away from threshold potential?
Towards threshold potential
Name an inhibitory neurotransmitter
GABA
Do inhibitory neurotransmitters change the membrane potential towards or away from threshold potential?
They stimulate more Cl- channels to open, causing Cl- to diffuse into the neurone, hyperpolarising the post-synaptic membrane
Do inhibitory neurotransmitters change the membrane potential towards or away from threshold potential?
Away from threshold potential
Define summation
The additive effect of multiple impulses at a synpase
What are the two types of summation?
Spatial and temporal
What is spatial summation?
Action potentials from different presynaptic neurones release enough neurotransmitter to exceed threshold potential.
What is temporal summation?
Multiple action potentials from a single presynaptic neurone releases enough neurotransmitter to exceed threshold potential
Explain how an excitatory and an inhibitory neurone both synapsing with one post-synpatic neurone would have an antagonistic effect
The balance of impulses from both neurones will determine whether the potential difference rises above threshold potential or not
Describe the three actions drugs can have in a synapse
They can bind to receptors on the post-synpatic membrane, inhibit the enzyme that breaks down neurotransmitters, and block the transport of neurotransmitters out of the synpase
Describe which drug action would reduce the effect of a neurotransmitter
Binding to receptors on the post-synaptic membrane
Describe which drug actions would increase the effect of a neurotransmitter
Inhibit the enzyme that breaks down neurotransmitters, and block the transport of neurotransmitters out of the synpase
How are drugs able to bind to neurotransmitter receptors on post-synaptic membranes?
The drugs have a similar shape to the neurotransmitter, and are therefore complementary to the receptor
Describe the action of drugs that bind to post-synaptic receptors
When the drug binds to the post-synpatic receptors, it prevents the neurotransmitter binding
How are drugs able to bind to enzymes that break down neurotransmitters?
They are a similar shape to neurotransmiiter, and are therefore complementary to the enzyme’s active site
Describe the action of drugs that bind to post-synaptic receptors
When the drug binds to the enzyme, it prevents to enzyme breaking down the neurotransmitter. More of the neurotransmitter can bind to the post-synpatic receptors
Describe the action of drugs that bind to post-synaptic receptors
They bind to the drug transporters, so more drug remains in the synpase to bind to the post-synpatic receptors
Muscles content after card 96
What are muscles comprised of?
Many muscle fibres
What are muscle fibres comprised of?
Many myofibrils
What are myofibrils comprised of?
Many sarcomeres attached end to end
What is the cytoplasm in muscle fibres called?
Sarcoplasm
What is the membrane in muscle fibres called?
Sarcolemma
What is the reticulum in muscle fibres called?
Sarcoplasmic reticulum
Name the organelle that connects the sarcolemma and the sarcoplasmic reticulum
T-tubules
Name the two proteins sarcomeres are made from
Actin and myosin
Describe the structure of actin.
Thinner and consists of two strands twisted around one another.
Describe the structure of myosin.
Many myosin tails wind together to form a myosin filament. Each myosin filament has a head.
Why are muscles striated?
They are dark bands where the actin and myosin overlap, and light bands where they don’t
Once sarcomere is measured in between which two lines?
Between two adjacent Z lines.
What is the light band called?
I band.
Which protein is in the light band?
Actin
What is the line in the centre of the I band called?
Z line
What is the dark band called?
The A band
Which proteins are in the A band?
Actin and myosin. It’s where they overlap.
What is the centre of that band called?
The H zone.
Which protein is found in the H zone?
Myosin.
What happens to the I-Band when a muscle contracts?
It becomes narrower.
What happens to the Z-lines when a muscle contracts?
They move closer together and the sarcomere shortens.
What happens to the H-zone when a muscle contracts?
It becomes narrower / disappears
What happens to the width of the A-Band?
Remains the same width.
When a muscle contracts, will the actin and myosin overlap more or less?
More
What is the sliding filament mechanism?
During contraction, the actin filaments are pulled past the myosin filaments, reducing the length of each sarcomere
Name the three proteins the thin (actin) filament is made from
Actin, troponin and tropomyosin
Which protein has many myosin binding sites along it?
Actin
Which protein is troponin bound to?
Tropomyosin
At rest, which protein is blocking the myosin binding sites on the actin?
Tropomyosin
What do you call a synpase between a motor neurone and a muscle fibre?
A neuromuscular junction
Which neurotransmitter is always used in neuromuscular junctions?
Acetylcholine
In a neuromuscular junction, where are the ligand-gated Na+ channels that the acetylcholine binds to?
In the sarcolemma
What the does the binding of acetylcholine to the ligand-gated Na+ channels in the sarcolemma cause?
Depolarisation of the sarcolemma, the t-tubules and the sarcoplasmic reticulum
What does the depolarisation of the sarcoplasmic reticulum cause?
Ca2+ to diffuse from the sarcoplasmic reticulum into the myofibril (through the sarcoplasm)
Once the Ca2+ are in the sarcoplasm of the myofibril, what do they bind to?
The tropnonin
Describe the effect of Ca2+ binding to troponin
It causes the shape of troponin to change causing it to move, exposing the myosin binding sites on the actin
Which part of the myosin filaments bind to the actin?
Myosin heads
After the myosin heads have bound to the actin, one ATP molcule is broken down to release energy. What is this energy used for?
For the myosin heads to bend, pulling the actin past the myosin. This is called the power stroke
After the power stroke, a new ATP molecule binds to the myosin head. What does this cause?
The mysoin head to detach and re-set
Name the two types of muscle fibres.
Slow-twitch and Fast-twitch fibres.
Which type of muscle fibre carries out more aerobic respiration?
Slow twitch muscle fibres
Which type of muscle fibre is used for endurance and posture?
Slow twitch muscle fibres
Describe the contractions in slow twitch muscle fibres
Slow and less powerful, but last longer
What two things are slow twitch muscles adapted for?
To increase the rate of aerobic respiration and to prevent the build up of lactic acid
Why are slow twitch muscle fibres surrounded by many capillaries?
To supply lots of oxygen for a high rate of aerobic respiration
Why do slow twitch muscle fibres have more mitochondria?
To produce more ATP
Which type of muscle fibre carries out more anaerobic respiration?
Fast twitch muscle fibres
Describe the contractions in fast twitch muscle fibres
Rapid and powerful, but over a short period of time
How are the myosin filaments adapted for more powerful contractions in fast twitch muscle fibres?
They are thicker and more numerous
Why is there a lots of glycogen in fast twitch muscle fibres?
To supply lots of glucose for anaerobic respiration
Which type of muscle fibre contains more phosphocreatine?
Fast twitch muscle fibres
What is the function of phosphocreatine?
To provide phosphate to make ATP in anaerobic conditions
How is creatine regenerated into phosphocreatine in aerobic conditions?
By hydrolysing ATP into ADP and Pi, and using the phosphate to regenerate creatine into phosphocreatine
