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Questions and Answers
Which of the following comprises the central nervous system (CNS)?
Which of the following comprises the central nervous system (CNS)?
Neuroglia primarily handle communication and send signals in the nervous system.
Neuroglia primarily handle communication and send signals in the nervous system.
False
What are the two main types of cells found in the nervous tissue?
What are the two main types of cells found in the nervous tissue?
Neurons and neuroglia
The _______ nervous system is also known as the involuntary nervous system.
The _______ nervous system is also known as the involuntary nervous system.
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Match the types of neurons with their corresponding characteristics:
Match the types of neurons with their corresponding characteristics:
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What is the primary role of the nervous system?
What is the primary role of the nervous system?
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Astrocytes are the most abundant type of neuroglia in the central nervous system.
Astrocytes are the most abundant type of neuroglia in the central nervous system.
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Name the structures in the nervous system that make up cell bodies in the CNS and PNS.
Name the structures in the nervous system that make up cell bodies in the CNS and PNS.
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Study Notes
Nervous System
- The nervous system is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
- The CNS includes the brain and spinal cord.
- The PNS includes all parts of the nervous system that are outside the CNS.
Nervous System Role
- The nervous system controls and coordinates the body.
- The nervous system constantly monitors and processes information from inside and outside the body.
- The nervous system combines new and stored information to create responses.
- Everything we think, feel, and do reflects the activity of the nervous system.
Divisions of the Nervous System
- Central Nervous System (CNS): Includes the brain and spinal cord.
- Peripheral Nervous System (PNS): Includes all parts of the nervous system outside the CNS.
Parts of the Nervous System
- Nerves
- Sensory receptors
- Clusters of neuron cell bodies (ganglia)
Cell Types in Nervous Tissue
- Neurons: Handle communication and send signals.
- Neuroglia: Support and protect neurons.
Neuroglia (Glial Cells)
- These are also known as "nerve glue".
- In the CNS, types of neuroglia include astrocytes, oligodendrocytes, microglial cells, and ependymal cells.
- In the PNS, types of neuroglia include Schwann cells (neurolemmocytes) and satellite cells.
- Their functions include supporting and protecting neurons, acting as phagocytes to clean up waste and debris, producing myelin, and assisting with exchange between capillaries and neurons.
Structure of Neuroglia
- Neuroglia can resemble neurons but cannot generate or transmit nerve impulses.
Neurons (Nerve Cells)
- Neurons are the basic functional units of the nervous system.
- They are specialized to send messages (nerve impulses) between parts of the body.
- All neurons have a cell body from which slender extensions (axons and dendrites) emerge.
- Cell bodies contain organelles that control the neuron's structure and function.
Inside the Neuron Cell Body
- Neurofibrils: Cytoskeletal elements that support and transport substances within the neuron.
- Chromatophilic substance (Nissl bodies): Clusters of rough endoplasmic reticulum involved in protein production.
Parts of a Neuron
- Dendrites: The receptive parts of the neuron; receive signals.
- Axons: Parts of the neuron that send out electrical signals (impulses).
- An axon can only have one axon, but it can have many dendrites.
- Axons can branch into smaller extensions called axon collaterals.
How a Neuron Becomes Excited
- A neuron is activated when other neurons release neurotransmitters near its dendrites.
- Neurotransmitters trigger an electrical signal in the neuron.
- If the signal is strong enough, it generates a nerve impulse (action potential).
- The action potential travels down the axon to carry the message.
- Action potential begins at the axon hillock.
Axon Terminals and Synapses
- The axon ends in small structures called axon terminals.
- Terminals connect to other neurons or target cells at junctions called synapses.
- Synapses contain vesicles that store neurotransmitters.
Myelin and Myelinated Fibers
- Myelin is a fatty material that covers many long nerve fibers.
- Myelinated fibers conduct nerve impulses more quickly.
Schwann Cells and Myelin Sheath
- In the peripheral nervous system, myelin is made by Schwann cells.
- Schwann cells wrap tightly around the axon in layers to form the myelin sheath, with gaps called Nodes of Ranvier.
Types of Neurons
- Unipolar (Pseudounipolar): One short process that splits into peripheral and central processes. Found in sensory neurons sending signals to the CNS.
- Bipolar: Two processes (one dendrite, one axon). Rare, found in sensory organs (e.g., eyes, ears, nose).
- Multipolar: Many processes (one axon, the rest dendrites). Found in the brain, spinal cord, and neurons carrying signals from the CNS.
Classification of neurons based on function
- Sensory neurons: Carry signals to the CNS.
- Motor neurons: Carry signals away from the CNS.
- Interneurons: Connect sensory and motor neurons. These are located within the CNS.
Structure of a Nerve
- Axon bundles in the CNS are called tracts.
- Axon bundles in the PNS are called nerves.
- The various coverings of nerves include endoneurium, perineurium, and epineurium.
Cranial Nerves
- There are 12 pairs of cranial nerves that serve functions for the head and neck and some areas of the thorax and abdomen.
CNS and PNS Relationship
- The brain and cranial nerves work closely to manage body functions.
Meninges of the Brain
- The meninges are three protective layers of connective tissue covering and protecting the brain and spinal cord: Dura mater, Arachnoid mater, and Pia mater.
Cerebrospinal Fluid (CSF)
- CSF cushions the brain and spinal cord.
- CSF flows through the ventricles of the brain and bathes the brain and spinal cord.
Spinal Cord Anatomy
- The spinal cord is enclosed within the vertebral canal.
- It's surrounded and protected by the meninges.
- It has a protective filum terminale that attaches to the coccyx.
- Spinal nerves are a part of the peripheral nervous system.
Spinal Cord Damage
- Motor and sensory functions lost in the body served by the damaged region.
Types of Damage:
- Paraplegia (paralysis in legs)
- Quadriplegia (paralysis in arms and legs)
Spinal Nerves
- 31 pairs of spinal nerves: Cervical, Thoracic, Lumbar, Sacral, Coccygeal
- They emerge from the spinal cord and pass through intervertebral foramina.
- Divided into dorsal and ventral branches.
- Ventral rami form nerve plexuses.
Nerve Plexuses
- Networks of nerves.
- Exist in the cervical, brachial, lumbar, and sacral regions.
- The nerve plexuses primarily serve muscles and skin of the limbs.
Cervical Plexus
- Formed by ventral rami (branches) of spinal nerves C1-C5.
- Contains the phrenic nerve, the key nerve related to breathing.
Brachial Plexus
- Formed by ventral rami of spinal nerves C5-T1.
- Helps function for the shoulders, arms, and hands.
Lumbar Plexus
- Formed by ventral rami of spinal nerves L1-L4.
- Supplies the muscles and skin of the lower abdomen, hips, and thighs.
Sacral Plexus
- Formed by ventral rami of spinal nerves L4-S4.
- Supplies the muscles and skin of the buttocks, perineum, and lower limbs.
Autonomic Nervous System (ANS)
- Controls involuntary body functions (e.g., smooth muscles, cardiac muscles, glands).
- It is divided into two main divisions: sympathetic and parasympathetic.
- Sympathetic division: The "fight or flight" division. Prepares the body for stressful situations by increasing heart rate, respiration etc.
- Parasympathetic division: The "rest and digest" division. Promotes self-repair and stress recovery actions (e.g., digestion, lowering the heart rate etc.).
Aging of the Sympathetic Nervous System
- As people age, the sympathetic nervous system is less efficient.
- This reduced efficiency can lead to conditions like Orthostatic Hypotension.
- Orthostatic hypotension is a condition where blood pressure drops too much when a person changes positions rapidly (e.g., standing up suddenly).
Reflexes
- Reflexes are rapid, predictable, involuntary responses to stimuli.
- Inborn reflexes (innate): Natural and automatic.
- Learned reflexes: Acquired through experience.
- Five components of reflex arcs: receptor, sensory neuron, integration center, motor neuron, effector.
Types of Reflexes
- Autonomic reflex: Controlled by autonomic nervous system; involve smooth muscles, cardiac muscles, and glands.
- Somatic reflex: Involve somatic nervous system; stimulate skeletal muscles.
Reflex Testing
- Reflex testing evaluates the functioning of the nervous system by testing for reflexes in various regions.
- Spinal cord injuries can impact reflex responses at various sites above and below the damage.
Cranial Nerve Reflexes
- Corneal reflex (trigeminal nerve): Blinking when cornea is touched.
- Gag reflex (glossopharyngeal and vagus nerves): The reaction to oral mucosa; ensures proper function.
Autonomic reflexes
- Pupillary light reflex: Controls pupil size in response to light.
- Ciliospinal reflex: Response involves pupil, and the reaction is observed.
Reaction Time of Reflexes
- Factors that influence reaction time: receptor sensitivity, nerve conduction speed, number of neurons, synapses, etc.
- Speed of learned reflexes differ from intrinsic reflexes.
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Description
Test your knowledge about the central nervous system (CNS) and its components with this quiz. Questions cover various aspects, including the types of cells, roles of neuroglia, and neuron characteristics. Ideal for students studying biology or human anatomy.