Principles of the nervous system Flashcards
How are the terms “dorsal” and “ventral” used in the brain?
In the brain, the terms “dorsal” and “ventral” have reversed meanings compared to the rest of the body. In the brain, “dorsal” signifies a direction that is upward, toward the top of the head, while “ventral” indicates a direction that is downward, toward the base of the skull.
What do the terms “rostral” and “caudal” represent in the context of the brain?
In the brain, “rostral” refers to a direction that is toward the front or the beak-like end of the brain. “Caudal” signifies a direction that is toward the back or tail-like end of the brain.
What are the two main components of the Central Nervous System (CNS)
Brain, ii) Spinal Cord
What are the two main components of the Peripheral Nervous System (PNS)?
i) Cranial Nerves [12 pairs], ii) Spinal Nerves [31 pairs]
How many pairs of spinal nerves are there?
31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Are the Olfactory (CN I) and Optic (CN II) nerves considered part of the CNS or PNS?
They are considered part of the CNS, although they are often grouped with the PNS on a structural level.
What is the role of sensory organs/receptors in the nervous system?
Sensory organs/receptors detect and respond to stimuli, allowing us to perceive the world around us.
What are the two main types of cells in the nervous system?
i) Neurons, ii) Glia cells (also known as glia and neuroglia)
What is the function of neurons?
Neurons are excitable cells that are responsible for transmitting electrical and chemical signals within the nervous system.
What are the three types of glia cells?
i) Oligodendrocytes, ii) Microglia, iii) Astrocytes
Which type of glia cells are responsible for producing myelin in the central nervous system?
Oligodendrocytes
: What is the role of microglia cells?
Microglia are the immune cells of the CNS and are involved in the defense and repair processes.
What is the most numerous type of cell in the CNS?
Glial cells (or neuroglia) outnumber neurons at a ratio of approximately 10:1.
How do neurons communicate with each other?
Neurons communicate with other neurons via chemical transmission, which involves the release and reception of neurotransmitters.
How do individual neurons communicate internally?
Communication within an individual neuron is through electrical impulses.
What is the function of a dendrite in a neuron?
The dendrite detects incoming information and conducts impulses toward the cell body.
: What is the role of the soma (cell body) in a neuron?
The soma contains the organelles necessary for the neuron’s functions.
What is the function of an axon in a neuron?
The axon conducts impulses away from the soma towards the axon terminal.
Which cells are responsible for myelinating neurons in the central nervous system (CNS)?
Oligodendrocytes myelinate neurons in the CNS.
Which cells are responsible for myelinating neurons in the peripheral nervous system (PNS)?
Schwann cells myelinate neurons in the PNS.
What is the role of an axon terminal?
The axon terminal contains neurotransmitters to be released into the synaptic gap.
What happens during neurotransmission at a synapse?
i) An action potential passes through the presynaptic neuron.
ii) This permits the vesicles carrying neurotransmitters to proceed to the synaptic gap.
iii) Neurotransmitters are released from the presynaptic neuron across the synaptic gap or synaptic cleft.
iv) Neurotransmitters are received by receptors at the postsynaptic neuron.
v) Any neurotransmitter not taken by the postsynaptic neuron remains in the synaptic gap until it is recycled by the presynaptic neuron or destroyed.
What is saltatory conduction?
Saltatory conduction is the propagation of an action potential (AP) along a myelinated axon, specifically occurring at the nodes of Ranvier. It is faster than continuous conduction.
Where does saltatory conduction take place?
Saltatory conduction occurs at the nodes of Ranvier along a myelinated axon.
What is continuous conduction?
Continuous conduction is the process of propagating an action potential within each gateway or segment of an axon. It takes a longer period of time compared to saltatory conduction.
How does the speed of saltatory conduction compare to continuous conduction?
Saltatory conduction is faster than continuous conduction.
What is the active site for saltatory conduction?
The nodes of Ranvier are the active sites where saltatory conduction occurs.
How is the action potential generated in a neuron?
The action potential is generated by an influx of sodium ions (Na+) into the neuron, followed by the release of potassium ions (K+) from the neuron.
How are CNS neurons interconnected?
CNS neurons are deeply interconnected, with each neuron having over 10,000 synaptic connections.
Are neurons capable of proliferating?
No, neurons are post-mitotic cells, which means they do not have the capacity to proliferate. However, there is evidence of adult neurogenesis in specific areas of the brain known as neurogenic niches.
What are the two types of junctions between the axon terminal and the target cell?
i) Electrical synapses, ii) Chemical synapses.
What occurs at electrical synapses?
Electrical synapses allow for direct electrical communication between cells, where ions can flow through gap junctions connecting the cells.
What occurs at chemical synapses?
Chemical synapses involve the release of neurotransmitters from the axon terminal of one neuron into the synaptic cleft, which then bind to receptors on the target cell to transmit the signal.
Can you provide an example of an area in the brain where adult neurogenesis occurs?
Neurogenic niches, such as the hippocampus, are regions in the brain where adult neurogenesis has been observed.
What is a unipolar neuron?
A unipolar neuron is a type of neuron that has a single axon only. It is typically found in primary sensory neurons, such as the cell bodies in dorsal root ganglia.
What is a ganglia?
A ganglia is a cluster of neuronal cell bodies.
What is a bipolar neuron?
A bipolar neuron is a type of neuron that has one axon and one dendrite. It is often found in specialized sensory neurons, such as those in the retina. An example of bipolar neurons in the retina is the bipolar cells that transmit signals from photoreceptors.
What is a multipolar neuron?
A multipolar neuron is a type of neuron that has one axon and multiple dendrites. They are the most common type of neurons in the brain. Motor neurons are also examples of multipolar neurons. There are three distinct types of multipolar neurons: a) Motor neurons found in the spinal cord, b) Pyramidal neurons found in the hippocampus, c) Purkinje neurons found in the cerebellum.
Can you provide an example of a pyramidal neuron?
Pyramidal neurons are found in the hippocampus. They are named for their pyramid-shaped cell body and are involved in processes related to learning and memory.
What is the role of astrocytes?
Astrocytes are glial cells that support and provide a suitable environment for neurons to function in the central nervous system (CNS).
What is the role of oligodendrocytes?
Oligodendrocytes are glial cells found only in the CNS and are responsible for the production and maintenance of the myelin sheath, which helps create white matter (WM). Each oligodendrocyte can myelinate multiple axons.
What is the composition of myelin?
Myelin is mainly composed of Myelin Basic Protein (MBP) and Proteolipid Protein (PLP), which make up approximately 80% of its structure.
What are microglia?
Microglia are a type of glial cell in the CNS. They have a delicate network of ramified cells and can be activated by pathogens. They are distributed throughout the CNS in a regular mosaic pattern and make up about 5% of all cells in the brain.
What are the functions of microglia?
Microglia serve as phagocytic and immune cells in the CNS. They play a role in promoting repair processes and respond to various stimuli by transitioning from a quiescent to an activated state.
What is the role of Schwann cells?
Schwann cells are the neuroglia of the peripheral nervous system (PNS). They myelinate axons through a process of spiral wrapping. They are important for axon regeneration and provide a substrate for axons to grow along.
How many axons does one Schwann cell myelinate?
One Schwann cell myelinates one axon.
What are the layers of myelin formed by Schwann cells called?
The layers of myelin formed by Schwann cells are referred to as dark bands.
What is the Node of Ranvier?
The Node of Ranvier is a gap between myelin sheaths along an axon where the axonal membrane is exposed.
Can axons be myelinated or unmyelinated?
Yes, axons can be either myelinated or unmyelinated. Myelinated axons have a diameter larger than 1 μm, while unmyelinated axons have a diameter smaller than 1 μm.
What is the significance of saltatory conduction?
Saltatory conduction is the process by which action potentials jump from one Node of Ranvier to another along a myelinated axon, allowing for rapid transmission of the signal.
What is the speed of conduction in myelinated axons compared to unmyelinated axons?
Conduction in myelinated axons is very rapid, with speeds up to 120 m/s. In contrast, unmyelinated axons have much slower conduction, typically less than 1.5 m/s.
What is the unit of measurement for micrometre?
The unit of measurement for micrometre is μm, which is equal to one millionth of a meter.
What are the anatomical components of the central nervous system (CNS)?
The central nervous system consists of the brain and the spinal cord.
What are the anatomical components of the peripheral nervous system (PNS)?
The peripheral nervous system includes the communication between the CNS and the periphery, which includes the viscera, muscles, joints, vessels, skin, and glands.
What are the divisions of the brain within the central nervous system?
The brain is divided into three main parts: the forebrain, midbrain, and hindbrain.
What are the specific components of the midbrain?
The midbrain includes structures such as the cerebral hemispheres, thalamus, hypothalamus, and brainstem.
What is the composition of the brain in terms of grey matter (GM) and white matter (WM)?
: The brain consists of both grey matter (GM), which includes neuronal cell bodies and synapses, and white matter (WM), which is composed of myelinated axons.
