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Questions and Answers
What is the potential difference across the plasma membrane known as?
Resting Membrane Potential
What are the stages involved in nerve action potential transmission?
What channels are involved in the propagation of action potential?
Voltage-Gated Sodium Channels
The diffusion potential is caused by an ion concentration difference on the two sides of the membrane.
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Match the brain component with its function:
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Which part of the nervous system is primarily responsible for the sensation of the body and special senses?
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Astrocytes are the largest and most numerous type of neuroglia in the central nervous system.
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What is the basic unit of the nervous system?
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______ are responsible for forming and maintaining the myelin sheath around CNS axons.
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Match the following functional classification of neurons with their characteristics:
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What are the three meninges of the brain?
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Which substances can pass through the Blood-Brain Barrier with ease?
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The function of the cerebrospinal fluid includes mechanical protection.
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Match the following sections of Spinal Cord with their corresponding functions:
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Name three cranial nerves responsible for sensory functions.
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Which pair of spinal nerves has most dermatomes?
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Study Notes
Organization of the Nervous System
- The nervous system consists of the Central Nervous System (CNS) and Peripheral Nervous System (PNS)
- The CNS includes the brain and spinal cord, while the PNS includes nerves that connect the CNS to the rest of the body
Histology of Nervous Tissue
- Neurons are the basic units of the nervous system
- Possess electrical excitability and can respond to stimuli and generate action potentials
- Have three main parts: dendrites, cell body, and axon
- Neuroglia are non-neuronal cells that provide support to neurons
- There are six types of neuroglia in the CNS and two in the PNS
Parts of a Neuron
- Dendrites: receiving or input portions of a neuron, short and highly branched
- Cell Body: contains free ribosomes and clusters of rough endoplasmic reticulum, also known as perikaryon or soma
- Axon: propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell
- Axon Hillock: connection of axon to the cell body
- Initial Segment: closest to the axon hillock
- Trigger Zone: site where nerve impulses arise
- Axoplasm: cytoplasm of an axon
- Axolemma: cell membrane of an axon
- Axon Terminals: end of the axon, involved in neurotransmission
Types of Neuroglia
- Astrocytes:
- Largest and most numerous neuroglia
- Functions: physically support neurons, create blood-brain barrier, secrete chemicals, help maintain chemical environment, and play a role in learning and memory
- Two types: Protoplasmic Astrocytes (short multi-branch processes, located in gray matter) and Fibrous Astrocytes (long unbranched processes, located in white matter)
- Oligodendrocytes: form and maintain myelin sheath around CNS axons
- Microglia: function as phagocytes, removing cellular debris and microorganisms
- Ependymal Cells: line ventricles of the brain and central canal of the spinal cord, assist in CSF circulation
- Schwann Cells: produce myelin sheath in the PNS
- Satellite Cells: flat cells that surround neuronal cell bodies in PNS ganglia, provide structural support and regulate exchanges between neurons and interstitial fluid
Functional Classification of Neurons
- Sensory/Afferent: carry nerve impulses towards the CNS
- Motor/Efferent: carry nerve impulses away from the CNS to effectors
- Interneurons: integrate and process information within the CNS### Brain Regions
- Frontal lobe: motor movements, decision making, problem-solving, judgment
- Parietal lobe: sensations, pain, recognizing objects
- Temporal lobe: memory and hearing
- Occipital lobe: vision
- Insula: lobe inside
Neurotransmission
- Synaptic transmission: process by which neurons communicate with each other
- Composed of:
- Presynaptic terminal
- Synaptic cleft
- Postsynaptic membrane
- Neurotransmitters are contained in synaptic vesicles found at the presynaptic terminal
- Steps of synaptic transmission:
- Action potentials arrive at the presynaptic terminal, causing voltage-gated Ca++ channels to open
- Ca++ diffuses into the cell, causing synaptic vesicles to release acetylcholine
Brain Structure
- Cerebral cortex: folds (gyri), deeper divisions (fissures), and narrower divisions (sulci)
- Cerebral white matter: composed of three types of nerve fibers:
- Association fibers: connect one side of the brain
- Commissural fibers: connect one side to the other
- Projection fibers: connect upper part to lower part
Diencephalon
- Thalamus: relay center for all sensory processes going to the cortex, except for sense of smell
- Hypothalamus: regulates satiety, hunger, temperature
- Epithalamus: involved in movement
- Subthalamus: communicates with basal nuclei for some movements
Basal Nuclei
- Functions for motor planning
- Nuclei means cell bodies located in the CNS
Limbic System
- Also known as the emotional brain
- Composed of:
- Parahippocampal gyrus
- Uncinate gyrus
- Cingulate gyrus
- Hippocampus
- Amygdala
- Dentate gyrus
- Septal nuclei
- Mammillary bodies
- Anterior and medial nucleus
- Olfactory bulbs
- Fornix, stria terminal, stria medullaris, medial forebrain bundle, mammillothalamic tract
Brain Stem
- Continuation of the spinal cord
- Composed of:
- Midbrain
- Pons
- Medulla Oblongata
Meninges
- Protective membranes covering the brain
- Composed of:
- Pia mater
- Arachnoid mater
- Dura mater
Blood-Brain Barrier
- A physiologic barrier that determines the permeability of brain capillaries to different substances or ions
- Properties:
- Few water-soluble substances, such as glucose, cross the BBB by active transport
- Creatine, urea, and most ions cross the BBB very slowly
- Proteins and most antibiotic drugs do not pass at all
- Lipid-soluble substances, such as oxygen, carbon dioxide, alcohol, and most anesthetic agents, can access brain tissue
Cerebrospinal Fluid
- Functions:
- Mechanical protection
- Homeostatic function
- Circulation
- Flow of cerebrospinal fluid: produced by the choroid plexus, flows through the ventricles, and is absorbed by the arachnoid villi
Cranial Nerves
- 12 pairs of cranial nerves:
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Spinal Nerves
- 31 pairs of spinal nerves:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- Dermatomes and myotomes: areas of skin and muscle supplied by specific spinal nerves
Autonomic Nervous System
- Divided into:
- Parasympathetic nervous system (energy conservation, relaxation)
- Sympathetic nervous system (energy consumption, fight-or-flight response)
- Functions and responses:
- Parasympathetic: bradycardia, vasodilation, bronchoconstriction, increased gastric motility, increased gland secretion
- Sympathetic: tachycardia, vasoconstriction, bronchodilation, increased BP
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Description
Introduction to the nervous system, covering the organization, histology, and neurophysiology of nervous tissues. Learn about the structure and functions of the nervous system.
