Biology Test 5 - Neural Signalling

What two systems coordinate bodily functions?

The nervous system and the endocrine system.

What are the two parts of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS).

What are neurons?

Nerve cells that transmit signals.

What are the three parts of a neuron?

Cell body (soma), dendrites, and axon.

What is the function of the cell body or soma?

Contains the nucleus and organelles but lacks centrioles.

What are dendrites?

Short, branched fibres that increase surface area to receive signals.

What is the axon hillock?

The site where action potentials are generated.

What is the axon?

A long fibre that carries impulses away from the cell body.

What cells form the myelin sheath in the PNS?

Schwann cells.

What is the myelin sheath made of?

75% lipids and 25% proteins.

What cells form myelin in the CNS?

Oligodendrocytes.

What are nodes of Ranvier?

Gaps between Schwann cells on a myelinated axon.

What are axon terminals or synaptic knobs?

Knob-like endings of axons that transmit signals.

What are the three types of neurons?

Sensory neurons, interneurons (relay neurons), and motor neurons.

What is resting potential?

The potential difference across the neuron membrane at rest, about -70 mV.

What ions are more concentrated outside a resting neuron?

Sodium ions (Na+).

What ions are more concentrated inside a resting neuron?

Potassium ions (K+).

What causes the resting potential?

Separation of charges and selective permeability of the membrane.

What is a nerve impulse?

A temporary reversal of membrane potential that travels through a neuron.

How fast can impulses travel in myelinated neurons?

Up to 120 m/s.

How fast can impulses travel in unmyelinated neurons?

1-3 m/s.

What is the function of the sodium-potassium pump?

Transports 3 Na+ out and 2 K+ in using ATP.

What enzyme powers the Na+/K+ pump?

ATPase.

What is depolarisation?

Inflow of Na+ that reverses membrane polarity.

What happens during repolarisation?

Outflow of K+ returns the membrane potential to -70 mV.

What is propagation in neurons?

The wave-like transmission of nerve impulse along the axon.

What is saltatory conduction?

Jumping of impulses between nodes of Ranvier in myelinated neurons.

How does myelination affect speed?

Increases conduction velocity.

How does axon diameter affect speed?

Larger diameters conduct impulses faster due to less ion resistance.

How does temperature affect nerve conduction?

Cooler temperatures slow down transmission.

What makes squid axons fast despite being unmyelinated?

Large axon diameter (over 500 μm).

What did Santiago Ramón y Cajal and Camillo Golgi contribute to neuroscience?

Developed staining methods to study nervous system structure.

What did Thomas Südhof discover?

Mechanisms of calcium-dependent neurotransmitter release.

What did May-Britt and Edvard Moser discover?

Grid and place cells in the brain for spatial navigation.

What is the fastest recorded human nerve impulse speed?

288 km/h.

What activity helps students understand action potentials?

Creating a timeline showing stages like resting potential, depolarisation, repolarisation, and hyperpolarisation.

What drives cognitive processes and learning in the body?

Tightly coordinated signaling between neurons via synapses drives cognitive processes and learning.

What direction does a signal travel in a neuron?

Signals travel in one direction (unidirectional flow) in a neuron.

What is a synapse?

A specialised junction between neurons or between a neuron and an effector cell that allows transmission of signals.

What are the components of a synapse?

Synaptic knob (axon terminal of presynaptic neuron), synaptic cleft, and dendrite of the postsynaptic neuron.

What is the size of the synaptic cleft?

12-20 nanometres.

What is found inside the synaptic knob?

Vesicles containing neurotransmitters.

What happens in the synaptic cleft?

Neurotransmitters are released from the presynaptic neuron and diffuse across the cleft to bind to receptors on the postsynaptic neuron.

What types of synapses exist?

Neuron-to-neuron, neuron-to-muscle, neuron-to-gland.

What is a neuronal synapse?

A synapse between two neurons involving neurotransmitter release and receptor binding.

Where are neuronal synapses found?

In the brain, spinal cord, and peripheral nerves.

What is a neuromuscular junction?

A specialised synapse between a motor neuron and a muscle fibre.

What neurotransmitter is involved in neuromuscular junctions?

Acetylcholine (ACh).

What happens when acetylcholine binds to receptors on a muscle fibre?

It causes depolarisation and the release of calcium ions, triggering muscle contraction.

What is the sarcolemma?

The plasma membrane of a muscle fibre.

What is the sarcoplasmic reticulum?

An organelle in muscle cells that releases calcium ions for muscle contraction.

What is a neuroglandular junction?

A synapse between a neuron and a gland cell.

What is an example of a neuroglandular junction?

The connection between hypothalamic neurons and the pituitary gland.

What are neurotransmitters?

Chemicals that allow neurons to communicate by transmitting signals across synapses.

What are the two types of neurotransmitters?

Small molecules and large peptide molecules.

Where are small molecule neurotransmitters synthesized?

In the axon terminal.

Where are large peptide neurotransmitters synthesized?

By ribosomes in the neuron's cell body.

How are large peptide neurotransmitters transported?

In vesicles from the cell body to the axon terminal.

What is the most common neurotransmitter in the nervous system?

Acetylcholine (ACh).

What are cholinergic neurons?

Neurons that release acetylcholine (ACh).

What are adrenergic neurons?

Neurons that release norepinephrine (noradrenaline).

What are the main neurotransmitters in the body?

Acetylcholine, norepinephrine, GABA, serotonin, glutamate, glycine, and dopamine.

What triggers neurotransmitter release from a presynaptic neuron?

An action potential reaching the axon terminal.

What causes vesicles to release neurotransmitters?

Influx of calcium ions into the presynaptic neuron.

What is exocytosis in neurons?

The process where vesicles fuse with the presynaptic membrane to release neurotransmitters.

How do neurotransmitters reach the postsynaptic cell?

They diffuse across the synaptic cleft and bind to specific receptors.

What happens after neurotransmitters bind to postsynaptic receptors?

A postsynaptic response is initiated, which can be excitatory or inhibitory.

How are neurotransmitters cleared from the synaptic cleft?

By reuptake, enzymatic degradation, or diffusion.

What is an excitatory postsynaptic potential (EPSP)?

A depolarisation of the postsynaptic membrane caused by sodium ion influx.

What causes depolarisation in the postsynaptic neuron?

Opening of sodium channels and Na+ inflow after neurotransmitter binding.

What is hyperpolarisation in a postsynaptic neuron?

When the membrane potential becomes more negative, leading to an inhibitory postsynaptic potential (IPSP).

What causes the transmission of nerve impulses in the body?

Nerve impulses are transmitted by neurons through coordinated actions involving synapses and neurotransmitters.

What ensures one-way flow of signals in the nervous system?

The unidirectional flow of signals is ensured by specialized junctions called synapses.

What is a synapse?

A synapse is a junction between two neurons or a neuron and an effector cell where neurotransmitters transmit signals.

What is the synaptic cleft?

The synaptic cleft is a 12-20 nm gap between the presynaptic and postsynaptic neurons.

What are the types of synapses?

Neuron-to-neuron, neuron-to-muscle (neuromuscular junction), and neuron-to-gland (neuroglandular junction).

What is a neuromuscular junction?

A specialized synapse where a motor neuron communicates with a muscle fiber to initiate contraction.

Which neurotransmitter is commonly used at neuromuscular junctions?

Acetylcholine (ACh).

What is a neuroglandular junction?

A synapse between a neuron and a glandular cell, regulating gland secretions.

What are neurotransmitters?

Chemicals that transmit signals across a synapse from one neuron to another or to an effector cell.

How are small molecule neurotransmitters synthesized?

They are synthesized in the axon terminal and stored in vesicles.

How are large peptide neurotransmitters synthesized?

They are synthesized by ribosomes in the cell body and transported to the axon terminal.

What happens when an action potential reaches the presynaptic terminal?

Voltage-gated calcium channels open, calcium enters, vesicles fuse with the membrane, and neurotransmitters are released.

What happens after neurotransmitters are released into the synaptic cleft?

They bind to receptors on the postsynaptic membrane, initiating a response.

What is an excitatory postsynaptic potential (EPSP)?

It is a depolarisation of the postsynaptic membrane due to Na+ inflow.

What causes an inhibitory postsynaptic potential (IPSP)?

Hyperpolarisation that makes the membrane more negative, preventing action potential generation.

What is depolarisation in a neuron?

The influx of Na+ ions that makes the membrane potential more positive.

What is the threshold potential?

Approximately −50 mV; the point at which voltage-gated Na+ channels open.

What is the peak value of membrane potential during depolarisation?

+40 mV.

What are leak channels?

Non-gated channels that allow passive movement of ions across the membrane.

What causes repolarisation of a neuron?

Efflux of K+ ions when voltage-gated potassium channels open.

What restores the resting membrane potential after an action potential?

The sodium-potassium pump (Na+/K+ pump).

What is the resting membrane potential of a neuron?

Approximately −70 mV.

How does the Na+/K+ pump work?

It pumps 3 Na+ out and 2 K+ into the neuron using ATP.

What is the intracellular concentration of Na+?

15 mM.

What is the extracellular concentration of Na+?

145 mM.

What is the intracellular concentration of K+?

150 mM.

What is the extracellular concentration of K+?

4 mM.

What are the stages of an action potential?

Resting, depolarisation, threshold, rising phase, falling phase, hyperpolarisation, resting, refractory period.

How is an action potential propagated?

As a wave, through local depolarisation spreading to adjacent regions of the axon.