Chapter 15 - Nervous Coordination Flashcards
What are the characteristics of nervous communication as opposed to the hormonal system
Fast
Short lived
Localised
Where is the central nervous system
Brain and spinal cord
What is meant by the peripheral nervous system
All neurones other than central nervous system
What is meant by the semantic nervous system
Conscious control
What is meant by autonomic nervous system
Unconscious body activity
What is meant by parasympathetic nervous system
Slows things down
What is meant by sympathetic nervous system
Speeds things up
Write the order that an impulse passes through
Stimulus Receptor Sensory neurone Relay neurone (CNS) Motor neurone Effector Response
Draw and label the system an impulse passes through
In folder
What are the characteristics of a receptor
- It is specific to one type of stimulus
- It is a cell or protein on the surface of a cell
- It transforms a stimulus into an electrical nerve impulse
- Connected to dendrites
What is a sensory neurone made up of
A single long sense on
A single short axon
What are the characteristics of a relay neurone
It’s within the CNS
Has many short dendrites and axons
Where is a synapse found
Between sensory neurone and relay neurone, and relay neurone and motor neurone
What are the characteristics of a motor neurone
Many short dendrites
Single long axon
Ends with a neuromuscular junction
What is an effector
A muscle or gland that expresses the response
What allows a resting potential to be maintained
The sodium-potassium pump
What does the sodium potassium pump do at resting potential
Active transport of 3 sodium ions out of neurone and 2 potassium ions in, using ATP
Describe the voltage gated sodium ions channels at resting potential
It’s closed so that the membrane is not permeable to sodium ions
Describe the potassium ions channel at resting potential
Open so some potassium ions diffuse out, down the electrochemical gradient
In summary, what happens at resting potential
- Sodium-potassium pump allows resting potential to be maintained
- Active transport of sodium ions out and potassium ions in
- Some potassium ions diffuse out via potassium ions channels
What happens during generator potential
- A weak stimulus causes some sodium ion channels to open and some sodium ions diffuse in
- This does not reach threshold and so sodium-potassium pump restores resting potential
What happens when generator potential reaches threshold
- Many voltage gated sodium ion channels open
- Sodium ions diffuse into axon
- Positive feedback occurs
What happens during depolarisation
- Sodium ion channels open
- Sodium ions diffuse in
What happens during repolarisation
- Potassium ion channels open
- Potassium ions diffuse out
- Voltage gated sodium ion channels close
When does hyperpolarisation occur
- When membrane potential is more negative than resting potential
What happens during hyperpolarisation
Sodium ion channels slow to close
What is meant by the all or nothing law
- If a generator potential reaches threshold
- Triggers an action potential
- All action potentials are same size
- A strong stimulus generates more frequent action potential
What is meant by the refractory period
- Made up of the phases after depolarisation (repolarisation and hyperpolarisation)
- Another action potential can’t be started
- Makes action potentials discrete (they don’t overlap) and uni-directional (one-way)
What causes the refractory period and therefore means that the action potential is uni-directional
- Sodium ions diffuse along the membrane
- Ahead of an action Potential the neurone is in resting potential
- Sodium ions trigger threshold
- Action potential moves along as a wave on depolarisation
- Means that repolarisation and hyperpolarisation must occur to return back to resting potential
What is myelin sheath
- Made of Schwann cells
- Is am electrical insulator
- So prevents movement of ions in or out of the neurone and therefore prevents depolarisation
What are nodes of ranvier
- Gaps between myelin sheath (diagram in folder if needed)
- Have lots of sodium and potassium ion channels
- Depolarisation can only happen at nodes
How does saltatory conduction occur
- Due to areas of myelination
- An action potential jumps between nodes of ranvier
- Speeding up the transmission of nerve impulses
- Cytoplasm conducts enough charge to depolarise the next node
How can temperature increase the speed of an action potential
- Higher temperature up to 40C
- Molecules diffuse faster due to more kinetic energy
- Therefore faster depolarisation and movement of action potential
How does the diameters of axons impact the speed of an action potential
- Greater diameter the faster the speed of action potential
- Due to more surface area for ion movement
What is a synapse
A junction between neurones where there is a chemical transition by neurotransmitters
What are the 2 types of neurontransmitter
Acetylcholine (ach)
Noradrenaline (nor)
What are the 4 adaptations that increase the speed of an action potential
Myelination
Saltatory conduction
Temperature
Diameter of axons
What are synapses called when the neurones release acetylcholine (ach)
Cholinergic synapses
What are synapses called when the neurones release noradrenaline (nor)
Adrenergenic synapses
What is a synaptic cleft
The gap between 2 neurones
What is the presynaptic neurone
The neurone that carries the impulse to the synapse
Explain the process of how an impulse crosses a synapse
- Action potential arrives at pre-synaptic knob
- Voltage gated ion channels open to allow calcium ions to diffuse in
- Vesicles full of neurotransmitter fuse with the pre-synaptic membrane
- Neurotransmitter diffuses across the synaptic cleft
- Neurotransmitter binds with receptors on post-synaptic membrane
- some sodium ion channels on the post-synaptic membrane open and sodium ions diffuse in off threshold is reached
- Voltage gated sodium ion channels open
- Action potential is triggered in post synaptic membrane
- Enzymes specific to neurotransmitter breaks it down and stops the response
- Products are re-absorbed into the post-synaptic knob and recycled
What makes synapses uni-directional
- Only receptors on post-synaptic membrane
- Neurotransmitter always released from pre-synaptic knob so diffuses from high to low concentration across synaptic cleft
What is meant by synaptic divergence
When one pre-synaptic neurone joins many post-synaptic neurones to spread the action potential to more than one part of the body
What is meant by synaptic convergence
When many pre-synaptic neurones join a single neurone in order to amplify the signal
What is spatial semmation
When neurotransmitter from multiple neurones combine to trigger an action potential in a post synaptic neurone (synaptic convergence)
Needed because a weak stimulus may only create a few action potentials
What is temporal semmation
When a stronger stimulus causes more frequent action potentials, releasing more neurotransmitter that add up to trigger an action potential in the post-synaptic membrane
Needed because a single action potential won’t always cause an action potential
What is a neuromuscular junction
A synapse between a motor neurone and a muscle fibre
What are some difference of neuromuscular junctions to normal synapses
- More receptors on post-synaptic membrane
- So an action potential is always generated in the post-synaptic membrane
Why do muscles act in antagonistic pairs
- Muscles can only pull
- Having pairs allows them to move a limb in both directions
What do ligaments and tendons do
Attach bones to bones
Tendons attach bones to muscles (tender)
What are some characteristics of skeletal/voluntary muscle
- Lots of mitochondria
- Long cylindrical cells called muscle fibres
- Muscle fibres are multinucleate (have many nuclei)
- Muscle fibres can rain long organelles called myofibrils
- Myofibrils constrain myofilaments called actin and myosin
What is a unit of muscle called
A sarcomere
What are z lines
The edges of a sarcomere
What is an M-line
The centre of a sarcomere
How is myosin respresented
Thick
Dark on an electron-micrograph
How is actin represented
Thin
Light colour in electron micrograph
What is the A-band
All of myosin including overlapping actin
What is the H-zone
Unoverlapped myosin
What is the I-band
Actin only with no overlapping myosin
Describe the sliding filament theory of a relaxed muscle
- Actin-myosin bonding site is blocked by tropomyosin
- Tropomyosin is a protein that’s only role is this
- Preventing an actinomyosin bridge being formed
Describe the sliding filament theory of muscle contraction
- Calcium ions released by an action potential cause tropomyosin to move out the bonding site
- Allows actinomyosin bridge to form
- Calcium ions also activate ATPase so ATP can be broken down
- ATP can be used to change shape/angle of myosin heads to enable a power stroke (this continues aslong as binding site is open from calcium)
- ATP also used to detach myosin head from binding site, cause a recovery stroke (return myosin head to starting position) and re-absorb calcium ions into sarcoplasmic reticulum by active transport
What happens to a sarcomere, I-band, H-zone and A-band during contraction
First 3 shorten
A-band stays the same
It H-zone disappears there is full contraction
What is the order of the fastest to slowest way for muscles to create ATP
1) Phosphocreatine
2) Anaerobic respiration
3) Aerobic respiration
Describe how phosphocreatine causes muscle contraction and explain the characteristics of this
- Phosphate group from PCr is added to ADP for ATP
- Short and simple reaction (fastest way to make ATP)
- PCr stores are used up quickly as it is used for high intensity exercises for a short duration
- It is anaerobic
- It is alactic (doesn’t produce lactic acid)
Describe how anaerobic respiration creates ATP and the characteristics of this
- 2 ATP made by glycolysis
- Pyruvate and lactate causes muscle fatigue
- Short duration
- High intensity
Describe how aerobic respiration creates ATP and characteristics of this
- Oxidative phosphorylation creates lots of ATP
- It is slow and there are many reactions
- There are no harmful waste products
List characteristics of slow and fast twitch muscle fibres
Slow
- Contract slowly
- Relax slowly
- Low force of contraction
- Resistant to fatigue
- Respire aerobically (no waste products)
- Have lots of mitochondria, blood vessels and myoglobin (red)
- Little anaerobic respiration so low intensity and long duration
Fast
- All opposite
What is the postsynaptic neurone
The neurone that carries the impulse away from the synapse
