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Questions and Answers
What is the function of the myelin sheath in nerve cells?
What is the function of the myelin sheath in nerve cells?
Which structure is primarily responsible for making up the myelin sheath in the peripheral nervous system (PNS)?
Which structure is primarily responsible for making up the myelin sheath in the peripheral nervous system (PNS)?
What is the purpose of the nodes of Ranvier in a neuron?
What is the purpose of the nodes of Ranvier in a neuron?
How do sensory neurons differ from motor neurons?
How do sensory neurons differ from motor neurons?
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In a resting potential state, what is the typical charge inside a neuron?
In a resting potential state, what is the typical charge inside a neuron?
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What is the primary function of motor neurons?
What is the primary function of motor neurons?
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Which component of a neuron is primarily responsible for the conduction of nerve impulses?
Which component of a neuron is primarily responsible for the conduction of nerve impulses?
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What role does the myelin sheath play in neuronal function?
What role does the myelin sheath play in neuronal function?
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At what point during signal transmission does the resting potential of a neuron occur?
At what point during signal transmission does the resting potential of a neuron occur?
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What is the role of interneurons within the nervous system?
What is the role of interneurons within the nervous system?
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What role do motor neurons play in the nervous system?
What role do motor neurons play in the nervous system?
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Which component of a neuron is primarily responsible for receiving signals?
Which component of a neuron is primarily responsible for receiving signals?
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What structure in a neuron carries impulses away from the cell body?
What structure in a neuron carries impulses away from the cell body?
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What type of neuron carries impulses from sensory receptors to the central nervous system (CNS)?
What type of neuron carries impulses from sensory receptors to the central nervous system (CNS)?
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Which of the following best describes the function of interneurons?
Which of the following best describes the function of interneurons?
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Which statement about resting potential in neurons is accurate?
Which statement about resting potential in neurons is accurate?
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What is the main purpose of the myelin sheath surrounding some axons?
What is the main purpose of the myelin sheath surrounding some axons?
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Which part of the neuron is primarily involved in integration and decision-making processes?
Which part of the neuron is primarily involved in integration and decision-making processes?
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Study Notes
Nervous System Overview
- The nervous system allows communication between cells through sensory input, integration of data, and motor output.
- Two cell types are neurons and neuroglia.
Nervous Divisions
- Two divisions:
- Central nervous system (CNS): Composed of the brain and spinal cord.
- Peripheral nervous system (PNS): Includes nerves and ganglia (collections of cell bodies).
Types of Neurons
- Three types:
- Sensory neurons: Carry impulses from sensory receptors to the CNS.
- Interneurons: Receive information within the CNS and send it to motor neurons.
- Motor neurons: Carry impulses from the CNS to effectors (glands or muscle fibers).
Neuron Structure
- Cell body: Contains the nucleus and most organelles.
- Dendrites: Short extensions that carry impulses to the cell body.
- Axon (nerve fiber): A long extension that carries impulses away from the cell body.
Myelin Sheath
- A lipid covering on long axons that increases the speed of nerve impulse conduction, provides insulation, and aids regeneration (in the PNS).
- Schwann cells: Neuroglia that form the myelin sheath in the PNS.
- Nodes of Ranvier: Gaps between myelination on the axons.
- Saltatory conduction: Conduction of the nerve impulse from node to node.
The Nerve Impulse: Resting Potential (RP)
- Resting potential: The state when the axon is not conducting a nerve impulse.
- More positive ions are outside the membrane than inside.
- Negative charge of -70 mV inside the axon.
- More sodium (Na+) ions outside the axon than inside.
- More potassium (K+) ions inside the axon than outside.
The Nerve Impulse: Action Potential
- Action potential: A rapid change in the axon membrane that enables a nerve impulse to occur.
- Sodium gates open, allowing sodium (Na+) ions to enter.
- Depolarization: The interior of the axon loses its negative charge (-55 mV, then +35 mV).
- Potassium gates open, allowing potassium (K+) ions to leave.
- Repolarization: The interior of the axon regains its negative charge (-70 mV).
- Wave of depolarization/repolarization travels down the axon.
The Synapse
- A synapse is a small gap between a sending neuron (presynaptic membrane) and a receiving neuron (postsynaptic membrane).
- Transmission across the synapse is accomplished by neurotransmitters (e.g., acetylcholine (ACh), dopamine, or serotonin).
- Neurotransmitters are stored in synaptic vesicles in the axon terminals.
Synaptic Transmission
- Nerve impulse reaches the axon terminal.
- Calcium ions enter the axon terminal and stimulate synaptic vesicles to fuse with the presynaptic membrane.
- Neurotransmitters are released and diffuse across the synapse.
- Neurotransmitters bind to the postsynaptic membrane, either inhibiting or exciting the neuron.
Synaptic Integration
- Integration is the summation of inhibitory and excitatory signals received by a postsynaptic neuron.
- Neurons receive multiple signals.
Central Nervous System (CNS)
- Includes the brain and spinal cord.
- Protected by: bones (skull and vertebral column), meninges (three protective membranes), cerebrospinal fluid (CSF) which cushions and protects.
- CNS is composed of:
- Gray matter: Contains cell bodies and nonmyelinated fibers.
- White matter: Contains myelinated axons.
CNS: Spinal Cord
- Extends from the brain's base along the vertebral canal.
- Functions in communication between the brain and most of the body.
- Center for reflex arcs.
- Gray matter is butterfly-shaped, white matter surrounds it.
CNS: Brain
- Four major parts:
- Cerebrum
- Diencephalon
- Cerebellum
- Brain stem
CNS: Cerebrum
- Cerebral hemispheres: Major structures of the cerebrum.
- Cerebral cortex: The thin, outer layer of gray matter.
- Primary motor area: Voluntary control of skeletal muscles.
- Primary somatosensory area: Processes sensory information from skeletal muscles and skin.
- Association areas: Integration occurs here.
- Processing centers: Perform higher-level analytical functions (e.g., Wernicke's and Broca's areas involved in speech).
CNS: Diencephalon
- Includes the hypothalamus and thalamus.
- Hypothalamus: Maintains homeostasis (e.g., hunger, sleep, thirst, body temperature, and water balance) and controls the pituitary gland.
- Thalamus: Receives all sensory input except smell; involved in memory and emotions.
- Pineal gland: Secretes melatonin and controls daily rhythms.
CNS: Cerebellum
- Receives and integrates sensory input from eyes, ears, joints, and muscles; provides information about the current position of the body.
- Functions: Maintains posture, coordinates voluntary movement, allows learning of new motor skills.
CNS: Brain Stem
- Includes the midbrain, pons, and medulla oblongata.
- Midbrain: Relay station between the cerebrum and spinal cord or cerebellum, has reflex centers.
- Pons: A bridge between the cerebellum and the CNS; regulates breathing rate; reflex center for head movements.
- Medulla oblongata: Contains reflex centers for regulating breathing, heartbeat, and blood pressure.
- Reticular formation: A major component of the reticular activating system (RAS) that regulates alertness.
Limbic System
- Connects primitive emotions (fear, pleasure) with higher functions (reasoning).
- Can cause strong emotional reactions, but conscious thought often overrides.
- Amygdala: Imparts emotional overtones.
- Hippocampus: Important for learning and memory.
Peripheral Nervous System (PNS)
- Includes cranial nerves (12 pairs), spinal nerves (31 pairs), and ganglia outside the CNS.
- Spinal nerves: Conduct impulses to and from the spinal cord.
- Cranial nerves: Conduct impulses to and from the brain.
- Two divisions:
- Somatic division: Serves the skin, skeletal muscles, and tendons.
- Reflexes: Automatic responses.
- Autonomic division: Regulates involuntary muscles (e.g., cardiac and smooth muscles) and glands.
- Two divisions:
- Sympathetic division: Coordinates the "fight or flight" response.
- Parasympathetic division: Counters the sympathetic system to bring the body back to a relaxed state.
- Two divisions:
- Somatic division: Serves the skin, skeletal muscles, and tendons.
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Description
Test your knowledge on the structure and function of the nervous system, including the distinctions between the central and peripheral nervous systems. Learn about neuron types, their functions, and the myelin sheath's role in impulse transmission.
