What are the two main components of the human nervous system?
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What are the two main components of the human nervous system?
The two main components of the human nervous system are the central nervous system (CNS) and the peripheral nervous system (PNS).
What is the function of the central nervous system (CNS)?
The function of the central nervous system (CNS) is to act as a central coordinating centre for impulses that come in from, and are sent out to, any part of the body.
What is a neurone?
A neurone is a nerve cell that transmits electrical impulses throughout the nervous system.
True or False?
The myelin sheath insulates the axon and prevents the loss of nerve impulses.
True.
The myelin sheath insulates the axon and prevents the loss of nerve impulses.
What is the function of dendrites in a neurone?
The function of dendrites in a neurone is to connect to other neurones and receive impulses from them, forming a network for communication.
What are the three main types of neurones?
The three main types of neurones are sensory neurones, relay neurones, and motor neurones.
What is the role of sensory neurones?
The role of sensory neurones is to carry impulses from receptors to the CNS (brain or spinal cord).
How do relay neurones differ from sensory neurones in structure?
Relay neurones have short, highly branched axons and dendrites, while sensory neurones have a cell body that branches off in the middle, with a long dendron and a long axon.
What is the function of motor neurones?
The function of motor neurones is to carry impulses from the CNS to effectors (muscles or glands).
True or False?
A nerve is a bundle of neurones.
True.
A nerve is a bundle of neurones.
What is an impulse in a neurone, and how does it differ from an electrical current?
An impulse in a neurone is a momentary reversal in the electrical potential difference across the neurone cell surface membrane, not an electrical current flowing along the neurone as if it were a wire.
What is the resting potential, and what is its typical value in a resting neurone?
The resting potential is the electrical potential difference across the membrane of a resting neurone, typically around -70 millivolts (mV).
What contributes to the negative charge inside a resting neurone?
The negative charge inside a resting neurone is due to the active transport of sodium and potassium ions, a difference in the diffusion rates of these ions, and negatively charged proteins inside the axon.
What role does the sodium-potassium pump play in maintaining the resting potential?
The sodium-potassium pump actively transports 3 sodium ions (Na⁺) out of the axon and 2 potassium ions (K⁺) into the axon, creating a concentration gradient that contributes to the resting potential.
How does the permeability of the neurone membrane to sodium and potassium ions differ, and what is the effect?
The neurone membrane is much less permeable to sodium ions than potassium ions, allowing potassium ions to diffuse out faster than sodium ions can diffuse back in, leading to a negative charge inside the neurone.
What is the result of the unequal rates of ion diffusion across the neurone membrane?
The unequal diffusion rates of sodium and potassium ions result in a resting membrane potential of about -70 mV, with the inside of the neurone being more negative compared to the outside.
What does it mean for a neurone membrane to be polarised?
A neurone membrane is polarised when it has reached its resting potential, with a negative charge inside and a positive charge outside.
How is a nerve impulse initiated in a neurone?
A nerve impulse is initiated by depolarisation of the neurone membrane, which involves a reversal of the electrical potential difference, generating an action potential.
What is an action potential, and what changes occur in the membrane potential during it?
An action potential is a rapid change in the electrical potential difference across the axon membrane, reversing the membrane potential from around -70 mV to around +40 mV.
What ions are involved in generating an action potential, and how do they move across the membrane?
Sodium ions (Na⁺) and potassium ions (K⁺) are involved in generating an action potential, with sodium ions rapidly entering the axon and potassium ions exiting, causing the depolarisation of the membrane.
What two structural features of neurones affect the speed of nerve impulse transmission?
The speed of nerve impulse transmission is affected by the myelination of the neurone and the diameter of the axon.
How does myelination influence the speed of nerve impulses?
Myelinated neurones conduct impulses much faster due to the insulation provided by the myelin sheath, which allows for saltatory conduction, where impulses jump between nodes of Ranvier.
Why do wider axons conduct impulses faster than narrower ones?
Wider axons conduct impulses faster because they offer less resistance to the action potential, allowing the electrical impulse to travel more quickly.
How does the speed of transmission in a giant unmyelinated axon of a squid compare to a myelinated mammalian axon?
Despite being significantly wider, the unmyelinated axon of a squid conducts impulses more slowly than a narrower, myelinated mammalian axon due to the absence of saltatory conduction.
What is the role of Schwann cells in myelinated neurones?
Schwann cells form the myelin sheath around the axon by wrapping themselves around it, providing electrical insulation and facilitating faster impulse conduction.
What is saltatory conduction, and where does it occur?
Saltatory conduction is the process by which nerve impulses jump from one node of Ranvier to the next along a myelinated axon, greatly increasing the speed of transmission.
How can the relationship between axon diameter, myelination, and speed of transmission be analysed?
The relationship can be analysed by collecting data on these variables, plotting them on a scatter graph, and calculating the correlation coefficient to determine the strength of the correlation.
What does a correlation coefficient (r) indicate?
The correlation coefficient (r) indicates the strength and direction of a linear relationship between two variables. Values close to 1 or -1 indicate a strong correlation, while a value of 0 indicates no correlation.
What is the difference between correlation and causation?
Correlation is an association or relationship between two variables, while causation indicates that one variable directly influences or causes changes in another.
How do you calculate the coefficient of determination (R²), and what does it signify?
The coefficient of determination (R²) is calculated by squaring the Pearson correlation coefficient (r). It represents the proportion of the variance in the dependent variable that is predictable from the independent variable, with values closer to 1 indicating a stronger correlation.
What is the significance of an R² value closer to 1 (or 100%)?
An R² value closer to 1 indicates a strong correlation, meaning the dependent variable can be accurately predicted from the independent variable.
What is a synapse?
A synapse is the junction between two neurones, separated by a small gap called the synaptic cleft, where they communicate via chemical signals.
What is the synaptic cleft?
The synaptic cleft is the small gap between the presynaptic and postsynaptic neurones at a synapse, across which neurotransmitters diffuse to transmit nerve impulses.
How does synaptic transmission begin when an impulse arrives at the presynaptic neurone?
When an impulse arrives at the presynaptic neurone, the membrane becomes depolarised, causing calcium ions to enter the neurone, which triggers the release of neurotransmitters into the synaptic cleft.
What role do calcium ions play in synaptic transmission?
Calcium ions trigger the movement and fusion of neurotransmitter-containing vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft.
What is acetylcholine (ACh), and what role does it play in synaptic transmission?
Acetylcholine (ACh) is a common neurotransmitter that, when released into the synaptic cleft, binds to receptors on the postsynaptic membrane, causing sodium ion channels to open and potentially generating an action potential.
What happens to acetylcholine after it has been released into the synaptic cleft?
After release, acetylcholine binds to receptors on the postsynaptic membrane and is then broken down by the enzyme acetylcholinesterase to prevent continuous stimulation of the postsynaptic neurone.
Why can impulses only travel in one direction across a synapse?
Impulses can only travel in one direction because neurotransmitters are released from the presynaptic neurone and receptors are only located on the postsynaptic membrane, ensuring unidirectional transmission.
What ensures that the postsynaptic neurone is not permanently depolarised?
The enzyme acetylcholinesterase breaks down acetylcholine, preventing the sodium ion channels from remaining open and stopping permanent depolarisation of the postsynaptic membrane.
What happens to the products of acetylcholine breakdown?
The breakdown products, acetate and choline, are reabsorbed by the presynaptic neurone, where they are used to reform acetylcholine for future use.
What are cholinergic synapses?
Cholinergic synapses are synapses that use acetylcholine (ACh) as their neurotransmitter to transmit nerve impulses across the synaptic cleft.