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Questions and Answers
What is the primary function of satellite cells in the peripheral nervous system?
What is the primary function of satellite cells in the peripheral nervous system?
What is the primary direction of impulse conduction for axons?
What is the primary direction of impulse conduction for axons?
What terminus structure contains vesicles filled with neurotransmitters?
What terminus structure contains vesicles filled with neurotransmitters?
Which of the following best describes a synapse?
Which of the following best describes a synapse?
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How does Multiple Sclerosis primarily affect the nervous system?
How does Multiple Sclerosis primarily affect the nervous system?
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What is the primary function of sensory input in the nervous system?
What is the primary function of sensory input in the nervous system?
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Which division of the nervous system carries impulses away from the central nervous system?
Which division of the nervous system carries impulses away from the central nervous system?
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Which type of neuroglia is responsible for forming a barrier between capillaries and neurons in the central nervous system?
Which type of neuroglia is responsible for forming a barrier between capillaries and neurons in the central nervous system?
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What is one key difference between neuroglia and neurons?
What is one key difference between neuroglia and neurons?
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Which subdivision of the motor division is responsible for involuntary actions?
Which subdivision of the motor division is responsible for involuntary actions?
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Where are most neuron cell bodies located?
Where are most neuron cell bodies located?
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What type of neurons carry impulses from sensory receptors?
What type of neurons carry impulses from sensory receptors?
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Which type of neuron has many extensions from the cell body?
Which type of neuron has many extensions from the cell body?
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What is the primary function of the hypothalamus?
What is the primary function of the hypothalamus?
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Which part of the brain acts as a relay station for sensory impulses?
Which part of the brain acts as a relay station for sensory impulses?
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What type of reflex involves activation of skeletal muscles?
What type of reflex involves activation of skeletal muscles?
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What protects the central nervous system?
What protects the central nervous system?
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What is the role of cerebrospinal fluid?
What is the role of cerebrospinal fluid?
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Which part of the brain is involved in emotional regulation?
Which part of the brain is involved in emotional regulation?
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What defines a mixed nerve?
What defines a mixed nerve?
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What is found in the central canal of the spinal cord?
What is found in the central canal of the spinal cord?
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What is the primary role of basal nuclei?
What is the primary role of basal nuclei?
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Which layer of the meninges is the innermost layer that clings to the brain?
Which layer of the meninges is the innermost layer that clings to the brain?
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The cerebral hemispheres include which of the following?
The cerebral hemispheres include which of the following?
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Study Notes
Nervous System Overview
- The nervous system has three main functions:
- Sensory input – gathering information about changes inside and outside the body (stimuli)
- Integration – processing and interpreting sensory input and deciding if action is needed
- Motor output – a response to integrated stimuli activating muscles or glands
Structural Classification
- Central nervous system (CNS):
- Brain
- Spinal cord
- Peripheral nervous system (PNS):
- Nerves outside the brain and spinal cord
Functional Classification of the PNS
- Sensory (afferent) division – carries information to the CNS
- Motor (efferent) division – carries impulses away from the CNS
- Somatic nervous system – voluntary control of skeletal muscles
- Autonomic nervous system – involuntary control of smooth muscle, cardiac muscle, and glands
Nervous Tissue: Support Cells (Neuroglia or Glia)
- Astrocytes: Star-shaped, abundant cells forming a barrier between capillaries and neurons, controlling the brain's chemical environment (CNS).
- Microglia (CNS): Spider-like phagocytes that dispose of debris.
- Ependymal cells (CNS): Line cavities of the brain and spinal cord, circulate cerebrospinal fluid.
- Oligodendrocytes (CNS): Produce myelin sheaths around nerve fibers in the CNS.
- Satellite cells (PNS): Protect neuron cell bodies in the PNS
- Schwann cells (PNS): Form myelin sheaths in the PNS
Neuroglia vs. Neurons
- Neuroglia divide; neurons do not.
- Most brain tumors are gliomas, involving neuroglia not neurons.
- Cell division is crucial in cancer.
Nervous Tissue: Neurons
- Neurons = nerve cells; specialized cells transmitting messages.
- Major regions of neurons:
- Cell body – nucleus and metabolic center
- Processes – fibers extending from the cell body (dendrites and axons)
- Dendrites – conduct impulses toward the cell body
- Axons – conduct impulses away from the cell body (only one per neuron)
Axons and Nerve Impulses
- Axons end in axonal terminals containing vesicles with neurotransmitters.
- Axonal terminals are separated by a synaptic cleft from the next neuron.
- Synapse – junction between nerves
Nerve Fiber Coverings
- Schwann cells – produce myelin sheaths around axons in the PNS in jelly-roll fashion.
- Nodes of Ranvier – gaps in the myelin sheath along the axon
Clinical Application: Multiple Sclerosis
- In multiple sclerosis, the myelin sheath is destroyed, hardening into scleroses.
- It is an autoimmune disease.
Neuron Cell Body Location
- Most neuron cell bodies are in the CNS (gray matter – cell bodies and unmyelinated fibers).
- Nuclei – clusters of cell bodies within the white matter of the CNS.
- Ganglia – collections of cell bodies outside the CNS.
Functional Classification of Neurons
- Sensory (afferent) neurons – carry impulses from sensory receptors (cutaneous and proprioceptors).
- Motor (efferent) neurons – carry impulses from the CNS to effectors.
- Interneurons (association neurons) – connect sensory and motor neurons within the CNS.
Structural Classification of Neurons
- Multipolar neurons – many extensions from the cell body
- Bipolar neurons – one axon and one dendrite
- Unipolar neurons – one short process leaving the cell body
How Neurons Function (Physiology)
- Irritability – ability to respond to stimuli
- Conductivity – ability to transmit an impulse.
- Plasma membrane at rest is polarized — fewer positive ions inside the cell than outside.
Continuation of the Nerve Impulse between Neurons
- Impulses cross the synapse to another nerve via neurotransmitters released from the axon terminal.
- The dendrite of the next neuron has receptors stimulated by the neurotransmitters.
The Reflex Arc
- Reflex – rapid, predictable, and involuntary response to a stimulus
- Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector.
Types of Reflexes and Regulation
- Autonomic reflexes – regulation of smooth muscle, heart, blood pressure, glands, and the digestive system.
- Somatic reflexes – activation of skeletal muscles.
Regions of the Brain
- Cerebral hemispheres
- Diencephalon
- Brain stem
- Cerebellum
Cerebral Hemispheres (Cerebrum)
- Paired, superior parts of the brain, comprising more than half of the brain mass.
- Surface has ridges (gyri) and grooves (sulci).
Lobes of the Cerebrum
- Fissures divide the cerebrum into lobes.
- Frontal lobe, parietal lobe, occipital lobe, temporal lobe.
Specialized Areas of the Cerebrum
- Somatic sensory area – receives impulses from sensory receptors
- Primary motor area – sends impulses to skeletal muscles
- Broca's area – involved in speaking
- Gustatory area – (taste)
- Visual area
- Auditory area
- Olfactory area
- Interpretation areas of the cerebrum – speech/language region, language comprehension region, general interpretation area
Layers of the Cerebrum
- Gray matter – outer layer, composed mostly of neuron cell bodies
- White matter – fiber tracts inside the gray matter
- Corpus callosum – connects hemispheres
Basal Nuclei
- Islands of gray matter within the cerebral white matter.
- Regulate voluntary motor activities by modifying information sent to the motor cortex.
- Problems with basal nuclei can cause jerky or spastic movements (Huntington's and Parkinson's diseases).
Diencephalon
- Situated above the brain stem, enclosed by the cerebral hemispheres.
- Composed of the thalamus, hypothalamus, and epithalamus.
Thalamus
- Surrounds the third ventricle; relay station for sensory impulses.
- Transfers impulses to the correct part of the cortex for localization and interpretation.
Hypothalamus
- Under the thalamus.
- Important autonomic nervous center.
- Helps to regulate body temperature and water balance.
- Regulates metabolism and part of the limbic system (emotions).
- Pituitary gland attached to it.
Epithalamus
- Forms the roof of the third ventricle and houses the pineal body (endocrine gland).
- Includes the choroid plexus for cerebrospinal fluid formation.
Brain Stem
- Attaches to the spinal cord.
- Midbrain
- Pons
- Medulla oblongata
Midbrain ("Mesencephalon")
- Mostly composed of nerve tracts.
- Reflects vision and hearing, cerebral aqueduct connects 3rd and 4th ventricles.
Pons
- Bulging center part of the brain stem.
- Composd of fiber tracts.
- Nuclei control breathing.
Medulla Oblongata
- Lowest part of the brain stem.
- Merges into the spinal cord; contains important control centers for heart rate, blood pressure, breathing, swallowing , and vomiting.
Cerebellum
- Has two hemispheres with convoluted surfaces
- Provides involuntary coordination of body movements
Protection of the Central Nervous System
- Scalp and skin
- Skull and vertebral column
- Meninges:
- Dura mater: Double-layered external covering (periosteum attached to the skull, meningeal layer covers the brain)
- Arachnoid layer: Middle layer (web-like)
- Pia mater: Internal layer, clings to the brain surface
Cerebrospinal Fluid
- Similar to blood plasma composition.
- Formed by the choroid plexus.
- Forms a watery cushion to protect the brain.
- Circulated in arachnoid space, ventricles, and central canal of the spinal cord.
Spinal Cord
- Extends from the medulla oblongata to the region of T12.
- Below T12: Cauda equina – collection of spinal nerves.
- Enlargements occur in the cervical and lumbar regions
Spinal Cord Anatomy
- Exterior white matter – conduction tracts.
- Internal gray matter – mostly cell bodies.
- Dorsal (posterior) horns
- Anterior (ventral) horns
- Central canal filled with cerebrospinal fluid.
- Meninges cover the spinal cord.
- Nerves leave at the level of each vertebra.
- Dorsal root
- Ventral root
Peripheral Nervous System
- Nerves and ganglia outside the CNS.
- Nerve = bundle of neuron fibers
- Neuron fibers bundled by connective tissue
Classification of Nerves
- Mixed nerves – both sensory and motor fibers.
- Afferent (sensory) nerves – carry impulses toward the CNS.
- Efferent (motor) nerves – carry impulses away from the CNS.
Spinal Nerves
- A pair at each vertebral level.
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Description
Explore the fundamental aspects of the nervous system, including its main functions: sensory input, integration, and motor output. Delve into the structural and functional classifications of the nervous system, distinguishing between the central and peripheral systems. Learn about the critical roles of neuroglia and the divisions of the peripheral nervous system.
