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Questions and Answers
What are the two principal types of cells in nervous tissue?
What are the two principal types of cells in nervous tissue?
Supporting cells (Neuroglia) and neurons
Which type of supporting cell forms the myelin sheaths around nerve fibers in the PNS?
Which type of supporting cell forms the myelin sheaths around nerve fibers in the PNS?
What condition results from the loss of myelin in the central nervous system?
What condition results from the loss of myelin in the central nervous system?
Multiple sclerosis
Match the following types of neuroglia with their functions:
Match the following types of neuroglia with their functions:
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Cerebrospinal fluid (CSF) is similar in composition to plasma.
Cerebrospinal fluid (CSF) is similar in composition to plasma.
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What three structures surround and protect the CNS?
What three structures surround and protect the CNS?
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What is the primary function of the blood-brain barrier?
What is the primary function of the blood-brain barrier?
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Identify the three main parts of the brain.
Identify the three main parts of the brain.
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What is the role of astrocytes in relation to the blood-brain barrier?
What is the role of astrocytes in relation to the blood-brain barrier?
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Which type of cell in the CNS is responsible for forming the myelin sheath?
Which type of cell in the CNS is responsible for forming the myelin sheath?
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What is the main function of astrocytes?
What is the main function of astrocytes?
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What is the role of microglia in the nervous system?
What is the role of microglia in the nervous system?
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The blood-brain barrier allows all types of molecules to freely pass through.
The blood-brain barrier allows all types of molecules to freely pass through.
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The three meningeal membranes are the dura mater, the arachnoid mater, and the ______.
The three meningeal membranes are the dura mater, the arachnoid mater, and the ______.
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What is cerebrospinal fluid (CSF) and its function?
What is cerebrospinal fluid (CSF) and its function?
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Which part of the brain is the largest and most superior?
Which part of the brain is the largest and most superior?
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What are Schwann cells responsible for?
What are Schwann cells responsible for?
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Name one neurodegenerative disease related to glial cells.
Name one neurodegenerative disease related to glial cells.
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Study Notes
Nervous System
- The nervous system is composed of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
- The CNS is made up of the brain and spinal cord
- The brain is responsible for higher brain function
- The spinal cord transmits signals between the brain and the rest of the body
- Nervous tissue consists of two cell types:
- Neurons: Nerve cells that transmit signals.
- Neuroglia: Supporting cells
Neuroglia (Supporting Cells)
- Neuroglia support, insulate, and protect neurons
- Astrocytes: Star-shaped cells that form a barrier between capillaries and neurons, preventing harmful substances in the blood from reaching the neurons
- Microglia: Spider-like phagocytes that remove cell debris and bacteria
- Oligodendrocytes: Produce myelin sheaths (fatty coverings) in the CNS, which insulate nerve fibers and increases the speed of signal transmission.
- Schwann cells: Produce myelin sheaths in the PNS
- Satellite cells: Surround neuron cell bodies in the PNS, providing protection and cushioning
- Ependymal cells: Line cavities in the brain and spinal cord, helping to circulate cerebrospinal fluid
Myelin Sheath
- A whitish, fatty material that acts as an insulator around nerve fibers
- Increases the speed of nerve impulse transmission
- Loss of myelin can cause a variety of neurological disorders
Physical Support of the CNS
- The CNS is protected by:
- Cranium: Bony skull that surrounds the brain
- Vertebral column: Bony structure that surrounds the spinal cord
-
Meninges: Three connective tissue membranes that separate the CNS from surrounding bone:
- Dura mater: Outermost layer
- Arachnoid mater: Middle layer
- Pia mater: Innermost layer
- The space between the pia mater and arachnoid mater, called the subarachnoid space, contains cerebrospinal fluid (CSF).
- Cerebrospinal fluid (CSF): Clear, watery fluid that surrounds the CNS and fills its cavities (ventricles). It provides protection to the nervous tissue.
Blood Supply to the CNS
- Despite being only 2% of body weight, the CNS receives 15% of the blood pumped by the heart
- High metabolic activity requires a large supply of glucose and oxygen
Blood-Brain Barrier
- A physical barrier that exists between the blood and the CSF
- Restricts the passage of hydrophilic molecules into the CNS
- Allows hydrophobic molecules, such as ethanol, to cross readily
- Formed by tight junctions between capillary endothelial cells and influenced by astrocytes
The Forebrain
- The largest and most superior part of the brain
- Divided into two hemispheres: left and right
- Contains two main structures:
- Cerebrum: Largest part of the brain
- Diencephalon: Includes thalamus and hypothalamus.
Cerebrum
- C-shaped structure containing both gray and white matter
-
Gray matter: Contains neuron cell bodies
- Cerebral Cortex: Outermost layer of the brain
- Subcortical nuclei: Deep, interconnected nuclei
- White matter: Beneath the gray matter, containing axons (nerve fibers)
Cerebral Cortex
- The outermost layer of the cerebrum, composed of a thin layer of gray matter
- Highly convoluted, with grooves called sulci and ridges called gyri
- Responsible for higher brain functions:
- Sensory perception, thinking, memory, voluntary movement
Nervous Tissue
- Consists of two main cell types: neurons and neuroglia (supporting cells).
- Neuroglia are collectively known as "nerve glue" and play crucial roles in supporting, insulating, and protecting neurons.
Types of Neuroglia
-
Astrocytes: Star-shaped cells that make up about half of neural tissue.
- They form a barrier between capillaries and neurons, protecting neurons from harmful substances in the blood.
- Microglia: Spider-like phagocytic cells that remove debris, including dead brain cells and bacteria.
- Oligodendrocytes: Produce myelin sheaths, fatty insulating coverings around nerve fibers in the central nervous system (CNS).
- Schwann cells: Form myelin sheaths around nerve fibers in the peripheral nervous system (PNS).
- Satellite cells: Protective, cushioning cells.
- Ependymal cells: Line the central cavities of the brain and spinal cord, their cilia help circulate cerebrospinal fluid.
Myelin Sheath
- A whitish, waxy substance that protects and insulates nerve fibers.
- It increases the transmission rate of nerve impulses.
Neuroglia and Disease
- Glial cells may contribute to neurodegenerative diseases like multiple sclerosis, Alzheimer's disease, and Parkinson's disease.
- Multiple sclerosis: Loss of myelin in the CNS, an autoimmune disorder where the immune system attacks oligodendrocytes.
- Alzheimer's disease: Caused by the loss of cholinergic neurons.
- Parkinson's disease: Caused by the loss of dopaminergic neurons.
- During neuron degeneration, astrocytes and microglia become overly active, releasing inflammatory chemicals that worsen neuron degeneration.
Physical Support of the CNS
- Cranium (Bony skull): Surrounds the brain.
- Vertebral column: Surrounds the spinal cord.
-
Meninges: Three connective tissue membranes that separate the soft tissue of the CNS from the surrounding bone.
- Dura mater: The outermost layer.
- Arachnoid mater: The middle layer.
- Pia mater: The innermost layer.
- Subarachnoid space: Located between the pia mater and arachnoid mater, filled with cerebrospinal fluid (CSF).
- Cerebrospinal fluid (CSF): Clear, watery fluid that surrounds the CNS and fills its cavities (ventricles), providing protection and cushioning for nervous tissue.
Blood Supply to the CNS
- The CNS accounts for only about 2% of body weight but receives roughly 15% of the blood pumped by the heart.
- This high blood supply is needed because CNS tissue has a high metabolic rate and requires significant glucose and oxygen to function.
Blood Brain Barrier
- A physical barrier between the blood and CSF.
- Most hydrophobic molecules can diffuse across capillary endothelial cells (simple diffusion, e.g., ethanol).
- The movement of hydrophilic molecules across capillary walls is restricted by the blood-brain barrier due to tight junctions between capillary cells.
- Astrocytes are critical for forming the blood-brain barrier.
Brain Structure
- The brain is composed of three main parts:
- Forebrain: The largest and most superior part, divided into left and right hemispheres.
- Brainstem: Connects the forebrain to the spinal cord.
- Cerebellum: Located at the back of the brain, involved in motor coordination and balance.
The Forebrain: Two Main Parts
-
Cerebrum: The largest part of the brain, responsible for higher-level cognitive functions.
- Gray matter: Contains cell bodies and is found in the cerebral cortex and subcortical nuclei.
- White matter: Contains axons and is located beneath the gray matter.
-
Diencephalon: Located near the base of the forebrain.
- Thalamus: Relays sensory information to the cerebral cortex.
- Hypothalamus: Controls vital functions like body temperature, hunger, and thirst.
Cerebrum: Cerebral Cortex
- The outermost layer of the cerebrum, a thin, highly convoluted layer of gray matter.
- The convolutions consist of grooves called sulci and ridges called gyri, which increase the surface area of the cortex.
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Description
This quiz explores the components of the nervous system, including the Central and Peripheral Nervous Systems. You will learn about the roles of neurons, neuroglia, and the specific types of neuroglia that support and protect nerve cells. Test your understanding of how these elements work together to facilitate communication within the body.
