Topic 4 - Coordination And Control In Animals Flashcards
What are the two mammalian nervous systems
Central nervous system
Peripheral nervous system
What nerves are involved in the PNS
Cranial nerves attached to the brain, and spinal nerves that are attached to the spinal cord
What is a neurone
The functional unit of the nervous system
What is the structure of a neurone
A cell body (centron) which contains the nucleus and other organelles and has a number of cytoplasmic extensions
Dendrons which transmit impulses to the cell body
Axons which transmit impulses away from the cell body and terminate in synaptic bulbs
Why are axons and dendrons myelinated
To insulate the axon, preventing ion movement between the axon and the tissue fluid around it
What are axons and dendrons myelinated in
Many layers of Schwann cells
What are nodes of Ranvier
Small spaces between Schwann cells giving rise to gaps in the myelin sheath
Why do neurone have a particularly large potential difference
A large excess of positively charged Sodium ions on the outside
What is the resting potential of the neurone
When the potential difference occurs when the neurone is at ‘rest’
Can the potential difference of a neurone be reversed
Yes
What makes a potential difference across the neurone membrane make the inside more negative
When a neurone is stimulated, the cell-surface membrane allows sodium ions to diffuse in
What is the threshold value
If a critical potential difference is reached
When does depolarisation of a neurone occur
When a threshold value is reached, then ions surge in and quickly depolarise the neurone
What is the action potential
The reversal of the potential difference
What is the all-or-nothing phenomenon
As an action potential does not vary in size, it either occurs or it doesnr
What is the refractory period
The period following the action potential when the membrane depolarises and recovers it resting potential
What are the 5 steps of changes in the potential difference, action potential and resting potential
- Axon membrane is at resting potential
- Depolarisation to threshold value needed for further depolarisation to occur
- Further depolarisation leads to action potential
- Magnitude of action potential
- Repolarisation of axon membrane during the refractory period when the membrane cannot be depolarised
How do local circuits occur
As positive ions are attracted by neighbouring negative regions and flows in both directions
How do the two sides of the membrane differ in impulse propagation
On one side, the membrane is still recovering its resting potential, it is in its refractory period during which it cannot be stimulated
On the other excitable side, the local circuit triggers depolarisation and the formation of an action potential
What is saltatory conduction
When an action potential jumps from one node of Ranvier to the next, which greatly increases the speed at which it is propagated along the axon
Where is the neurotransmitter chemical located
At the synaptic vesicles at the synaptic bulbs
What is the synaptic cleft
The gap between the synaptic bulbs
What is the difference between the pre-synaptic membrane and post-synaptic membrane
The membrane of the neurone just before the cleft is called the pre-synaptic membrane and the one on the other side is the post-synaptic membrane
What is the first step of synaptic transmission
When an impulse arrives at the synaptic bulb, the membrane becomes permeable to calcium ions which diffuse into the bulb
What step of synaptic transmission occurs after ‘When an impulse arrives at the synaptic bulb, the membrane becomes permeable to calcium ions which diffuse into the bulb’ and before ‘Vesicles fuse with the presynaptic membrane and releases the neurotransmitter molecules by Exocytosis into the synaptic cleft’
Calcium ions stimulate movement of synaptic vesicles towards the pre-synaptic membrane
What step of synaptic transmission occurs before ‘Neurotransmitter molecules diffuse across the synaptic cleft to the post-synaptic membrane’ and after ‘Calcium ions stimulate movement of synaptic vesicles towards the pre-synaptic membrane’
Vesicles fuse with the presynaptic membrane and releases the neurotransmitter molecules by Exocytosis into the synaptic cleft
What step of synaptic transmission occurs before ‘On the post-synaptic membrane, neurotransmitter molecules attach to specific receptors’ and after ‘Vesicles fuse with the presynaptic membrane and relates the neurotransmitter molecules by Exocytosis into the synaptic cleft‘
Neurotransmitter molecules diffuse across the synaptic cleft to the spot-synaptic membrane
What step of synaptic transmission occurs before ‘This causes ion channels to open so that the potential difference in the post-synaptic membrane is altered. The magnitude of this change is dependent on the amount of transmitter released and so the number of receptors filled’ and after ‘Neurotransmitter molecules diffuse across the synaptic cleft to the spot-synaptic membrane’
On the post-synaptic membrane, neurotransmitter molecules attach to specific receptors
What step of synaptic transmission occurs before ‘When a molecule of ACh attaches to its receptor site, a sodium ion channel opens and the post-synaptic membrane becomes depolarised’ and after ‘On the post-synaptic membrane, neurotransmitter molecules attach to specific receptors’
This causes ion channels to open so that the potential difference in the post-synaptic membrane is altered. The magnitude of this change is dependent on the amount of transmitter released and so the number of receptors filled
What step of synaptic transmission occurs before ‘Transmitter molecules on the receptors are inactivated. This breakdown of the neurotransmitter is important as it allows the resting potential to be re-established’ and after ‘This causes ion channels to open so that the potential difference in the post-synaptic membrane is altered. The magnitude of this change is dependent on the amount of transmitter released and so the number of receptors filled’
When a molecule of ACh attaches to its receptor site, a sodium ion channel opens and the post-synaptic membrane becomes depolarised
What step of synaptic transmission occurs before ‘The breakdown products diffuse across the cleft and are reabsorbed into the synaptic bulb where they are resynthesised into the neurotransmitter using energy in the form of ATP’ and after ‘When a molecule of ACh attaches to its receptor site, a sodium ion channel opens and the post-synaptic membrane becomes depolarised’
Transmitter molecules on the receptors are inactivated. This breakdown of the neurotransmitter is important as it allows the resting potential to be re-established
What is the last step of synaptic transmission
The breakdown products diffuse across the cleft and are reabsorbed into the synaptic bulb where they are resynthesised into the neurotransmitter using energy in the form of ATP
What is a neuromuscular junction
When a motor neurone synapse with a skeletal muscle fibre
What is the main transmitter molecule in synapses
Acetylcholine
What is noradrenaline
The neurotransmitter in the synaptic bulbs of the sympathetic nervous system
What is an EPSP
Excitatory post-synaptic potential, when Sodium ion channels open, which results in depolarisation of the post-synaptic membrane
What do EPSPs do to the membrane
They make it less negatively charged ad more likely to reach the threshold level to trigger an action potential, propagating an impulse in the post-synaptic cell
What is GABA
Gamma-aminobutyric acid, a neurotransmitter found in the brain
What do GABA do
When it attaches to its receptor sites, chloride ion channels open, causing the post-synaptic membrane to be hyperpolarised
What is an IPSP
Inhibitory post-synaptic potential
What do IPSPs do to the membrane
They make it more negatively charged and less likely to reach the threshold level to trigger an action potential
What are some advantages of synapses slowing transmission
It ensures that transmission occurs in only one direction
It protects effectors from over-stimulation
It allows certain actions to be controlled through a combination of stimulation and inhibition
It integrates the activity of different neurone synapsing with a single post-synaptic neurone
What are the 3 main type of muscle
Skeletal
Cardiac
Smooth
What is the appearance of skeletal muscle
Muscle fibres are multinucleate, with distinct striations
Where is skeletal muscle found and what is its function
It is attached by tendons to bones, and controls the movement of parts of the body and locomotion
What is the cardiac muscle
Cells are striated and branched, forming a link network, intercalated discs between cells
Where is the cardiac muscle found, and what does it do
Found in the wall of the heart, and pumps the heart to maintain blood circulation
What is smooth muscle
Spindle-shaped cells with a single nucleus and no striations
Where is the smooth muscle found, and what is its function
Present in the iris and ciliary body of the eye and walls of tubular organs, is responsible for movement of materials within the body
What is the structure of the skeletal muscle
Skeletal muscle consist of bundle of muscle fibres. A muscle fibre is multinucleate, which lies just beneath the sarcolemma, out of the way of the packed myofibrils, each of which is surround in sarcoplasmic reticulum and joined transversely by T-tubules, and between which are numerous mitochondria.
Why is skeletal muscle described as striated
Due to the different colours of the protein present, actin and myosin
What is the Z Line
The sarcomere
What is the A band
A thick filament of only myosin
What is the I band
A thin filament of only actin
What is the H-zone
The centre of the A-band
What is the sliding filament theory
The theory that describes how shortening of myofibrils causes muscle contract
What is the first step of the sliding filament theory
An action potential arrives via a motor neurone at the synapse with the cell-surface membrane of the muscle fibre
What is the steps of the sliding filament theory
- An action potential arrives due to a motor neurone at the synapse with the cell-surface membrane of the muscle fibre
- Action potentials are propagated through the T-tubule and along the sarcoplasmic reticulum causing Calcium ions to be released into the cytoplasm
- Calcium ions cause ancillary proteins to de displaced and uncover the binding sites
- Heads of the myosin molecules next to the uncovered binding sites now attach to the actin filaments
- The myosin heads rotate back, pulling the thin actin filaments over the thick myosin filaments
- ATP binds with the myosin heads and the energy released causes the myosin heads to detach from the actin filaments
The detached myosin heads regain original position and attach to another exposed bind site on the actin filament
