Neural Control and Co-ordination

Flashcards covering key definitions, nerve impulse generation, conduction, membrane potentials, and synaptic transmission from Chapter 10: Neural Control and Co-ordination.

Which two organ systems jointly coordinate and integrate all activities of the body organs?

The neural system and the endocrine system.

What is the primary function of afferent nerve fibres in the neural system?

They transmit nerve impulses from tissues and organs to the central nervous system (CNS).

In which animal phyla are neurons completely absent?

Phylum Protozoa and Phylum Porifera.

Which cell structure is absent in most neurons, making cell division and regeneration difficult?

Centrosome.

What is the primary function of the neural system?

To receive, process, and transmit information throughout the body.

How do neurons mainly differ from other body cells?

Neurons are excitable cells that can generate and conduct impulses.

Which cells form the insulating myelin covering around axons?

Oligodendrocytes and Schwann cells.

Which type of neuron lacks dendrites and consists of a single axon?

Unipolar neuron.

What is the function of a relay neuron (interneuron)?

It connects sensory neurons and motor neurons.

What is the approximate resting membrane potential of a neuron?

$$-70\,\text{mV}$$

Why does the resting membrane potential of a neuron exist primarily?

Due to the resting membrane having a significantly higher permeability to $\text{K}^+$ than to $\text{Na}^+$.

What ion movement causes the membrane potential to become positive during depolarisation?

The influx (diffusion) of $\text{Na}^+$ ions into the neuron from extracellular fluid.

Which ion channels open first during the generation of an action potential?

Voltage-gated $\text{Na}^+$ channels.

What ion movement is responsible for the repolarisation of a neuron membrane?

The efflux (outflow) of $\text{K}^+$ ions out of the neuron.

What is the primary role of the $\text{Na}^+/\text{K}^+$ pump in a neuron?

To maintain the resting potential by active transport of $3\,\text{Na}^+$ out and $2\,\text{K}^+$ into the neuron.

What is meant by a threshold stimulus in nerve impulse conduction?

The minimum stimulus strength required to just initiate an action potential.

What does the "all-or-none" law of nerve impulse transmission state?

Either a full nerve impulse is generated or no impulse is generated at all.

Where does saltatory conduction occur along a neuron?

In myelinated axons.

What membrane feature characterizes the Nodes of Ranvier?

A high density of voltage-gated $\text{Na}^+$ channels and an absence of myelin sheath.

What event is triggered when an action potential arrives at the synaptic knob?

The opening of voltage-gated $\text{Ca}^{2+}$ channels.

By what mechanism are neurotransmitters released from synaptic vesicles?

Exocytosis.

What is the immediate result of neurotransmitter binding to postsynaptic receptors?

A change in the permeability of the postsynaptic membrane.

What causes synaptic delay in chemical synapses?

The time taken for neurotransmitter release, diffusion, and binding to receptors.

How do electrical synapses differ from chemical synapses regarding ion flow?

Electrical synapses allow direct flow of ions between presynaptic and postsynaptic cells without using neurotransmitters.

Which factor does NOT affect the speed of nerve impulse conduction?

Strength of stimulus.

What effect do inhibitory neurotransmitters produce on the postsynaptic membrane?

Hyperpolarisation.

Why is the direction of a nerve impulse across a synapse fixed?

Because neurotransmitters are released only from the presynaptic axon endings and not by dendrites.

What is the correct sequence of events during impulse generation and conduction?

1) Application of an external stimulus, 2) Opening of sodium gates, 3) Influx of $\text{Na}^+$, 4) Depolarisation, 5) Formation of action potential, 6) Repolarisation.

Which neurotransmitter is considered the most abundant?

Acetylcholine.

What is the correct sequence of steps in synaptic conduction?

1) Arrival of action potential in synaptic knob, 2) Release of $\text{Ca}^{2+}$ ions into synaptic knob and adherence to vesicles, 3) Synaptic vesicles release neurotransmitters, 4) Neurotransmitters bind to specific receptors, 5) Regeneration of a new action potential on the postsynaptic membrane, 6) Postsynaptic membrane repolarised by inactivating neurotransmitter.