Nervous System (Pt. 1) Flashcards
Q: What makes up nervous tissue?
A: Neurons and neuroglia.
Q: What is a nerve?
A: Bundles of axons, connective tissue, and blood vessels located outside CNS & PNS.
Q: What percentage of total body weight is the nervous system?
A: About 3% (2 kg or 4.5 lb).
Q: What are the two main parts of the nervous system?
A: Central nervous system (CNS) and peripheral nervous system (PNS).
Q: What are the two components of the CNS?
A: Brain and spinal cord.
Q: What are the two divisions of the PNS?
A: Sensory (Afferent) Division and Motor (Efferent) Division.
Q: What are the two branches of the Autonomic Nervous System?
A: Sympathetic Division (“fight-or-flight”) and Parasympathetic Division (“rest-and-digest”).
Q: What is the function of sensory receptors?
A: To monitor changes in the external and internal environment.
Q: What are enteric plexuses?
A: Networks of neurons in the digestive tract that regulate smooth muscle and gland functions.
Q: What is the key feature of neurons?
A: The ability to quickly transmit signals over both short and long distances, enabling rapid response to stimuli.
Q: What are the main characteristics of neurons?
A: They are specialized for sensing, thinking, memory, control; cannot divide; are electrically excitable; and respond to stimuli.
Q: What is a nerve impulse?
A: An electrical signal that travels along neuron membranes, caused by sodium and potassium ion movement.
Q: What is unique about nerve impulse strength?
A: They move at constant strength.
Q: What makes neurons some of the longest cells in the human body?
A: They can stretch from the spinal cord to toes or from foot to brain.
Q: Can neurons reproduce?
A: No, neurons cannot divide or reproduce.
Q: What are the two main cell types in the nervous system?
A: Neurons and Neuroglia.
Q: What are the main components found in the cell body (soma)?
A: contains nucleus and typical cell components
Q: What is a ganglion?
A: A cluster of multiple cell bodies located outside the CNS.
Q: What indicates aging in neurons?
A: The presence of lipofuscin pigment.
Q: What are dendrites and their function?
A: They are the receiving portion of the neuron, with branched, tree-like structures containing receptor sites for neurotransmitters.
Q: What is unique about dendritic structures?
A: They have numerous receptor sites (dendritic spines).
Q: What is the axon’s main function?
A: To propagate nerve impulses toward other neurons, muscle fibers, or gland cells.
Q: Where do nerve impulses begin in a neuron?
A: At the axon hillock’s initial segment (trigger zone).
Q: What important structure is NOT found in axons?
A: Rough endoplasmic reticulum (no protein synthesis occurs in axons).
Q: What are axon collaterals?
A: Side branches that extend from the main axon.
Q: How does an axon end?
A: It terminates in axon terminals or telodendrion for communication.
Contains synaptic vesicles that contain neurotransmitters (relays the action potential):
axon terminal
Site of communication between 2 neurons or a neuron and effector cell (muscle, gland)
Synapse
Q: What are the two forms of axon terminal endings?
A: Synaptic end bulbs (bulb-shaped swellings) and varicosities (string of swollen bumps).
Q: What are synaptic vesicles?
A: Tiny membrane-enclosed sacs that store neurotransmitters.
Q: What are the two possible effects of neurotransmitters?
A: Excitatory or inhibitory effects on target cells.
Q: What is fast anterograde transport?
A: Movement of materials from cell body to axon terminals at 200-400 mm per day.
Q: What is retrograde transport?
A: The return of materials back to the cell body for recycling.
Q: What is a synapse?
A: A small gap where two neurons meet or where a neuron connects to a muscle or gland cell.
Q: What are the three types of synapses?
A: Neuron-to-neuron, neuron-to-muscle, and neuron-to-gland.
Q: How does signal transmission work at a synapse?
A: Presynaptic neuron releases neurotransmitters that travel across the synaptic cleft to the next cell.
Q: What types of cells can neurons form synapses with?
A: Other neurons, muscle fibers, and gland cells.
Q: Why are synapses important?
A: They enable rapid information transmission and flexible communication between cells for complex body functions.
Q: What are the two main divisions of the nervous system?
A: Central Nervous System (CNS) and Peripheral Nervous System (PNS).
Q: What are the two main divisions of the PNS?
A: Sensory Division (Afferent) and Motor Division (Efferent).
Q: What are the two types of senses in the Sensory Division?
A: Somatic senses (touch, temperature, pain, position) and special senses (vision, hearing, smell, taste, balance).
Q: What are the two branches of the Motor Division?
A: Somatic Nervous System and Autonomic Nervous System.
Q: What are the three parts of the Autonomic Nervous System?
A: Sympathetic (fight/flight), Parasympathetic (rest/digest), and Enteric (digestive control).
Q: How does the Sensory Division function?
A: As an “INPUT” system, bringing information TO the CNS.
Q: How does the Motor Division function?
A: As an “OUTPUT” system, sending commands FROM the CNS.
Q: What does the Somatic Nervous System control?
A: Voluntary movements of skeletal muscles.
Q: What three types of tissue does the Autonomic System affect?
A: Smooth muscle, heart muscle, and glands.
Q: What is the main function of the CNS?
A: To process information received from the body.
Conveys messages INTO the CNS
Sensory Division (i.e. Afferent)
Conveys messages FROM CNS
Motor Division (i.e. Efferent)
Q: What are the three main functions of the nervous system?
A: Sensory, integrative, and motor functions.
Q: What is the sensory function?
A: To detect changes through sensory receptors, both inside and outside the body.
Q: What is the integrative function?
A: To analyze incoming sensory information, store information, and make decisions about appropriate behaviors.
Q: What is the motor function?
A: To respond to stimuli via effectors (muscles and glands).
Q: What components are involved in the motor response?
A: Muscles and glands (effectors).
Q: Using a cell phone as an example, what represents the sensory function?
A: Hearing the phone ring through ear stimulation.
Q: Using a cell phone as an example, what represents the integrative function?
A: The brain processing the ring and deciding to answer the call.
Q: Using a cell phone as an example, what represents the motor function?
A: Muscles moving to grab and answer the phone.
Q: What happens after sensory receptors detect changes?
A: The information travels to the brain and spinal cord through nerves.
Q: What are the three main types of neurons?
A: Sensory (afferent) neurons, interneurons (association neurons), and motor (efferent) neurons.
Q: What is the function of sensory neurons?
A: To convey information to the CNS when stimuli activate sensory receptors.
Q: What is the function of interneurons?
A: To process sensory information and elicit motor responses within the CNS.
Q: What is the function of motor neurons?
A: To convey information from the CNS to muscles and glands.
Q: Where are interneurons located?
A: In the CNS, between sensory and motor neurons.
Q: What type of structure do most sensory neurons have?
A: Unipolar structure.
Q: What type of structure do most motor neurons and interneurons have?
A: Multipolar structure.
Q: How do motor neurons transmit signals?
A: Through cranial or spinal nerves.
Q: What happens when a sensory receptor is activated?
A: It creates a nerve impulse (action potential) that travels through its axon to the CNS.
Q: What is the structure of a sensory neuron?
A: Usually pseudounipolar, with sensory receptor (dendrites), axon, and cell body located along the axon.
Q: Where are sensory neurons located?
A: In the Peripheral Nervous System (PNS).
Q: Where are interneurons located?
A: In the Central Nervous System (CNS).
Q: What is the function of sensory receptor dendrites?
A: To detect stimuli.
Q: What is the primary function of interneurons?
A: To integrate sensory input and formulate responses.
Q: What are effectors?
A: Muscles or glands that react to signals from motor neurons.
Q: What is the correct flow of information in the nervous system?
A:
Sensory neuron → Interneuron → Motor neuron → Effectors.
Q: Where are motor neurons’ signals directed?
A: To effectors (muscles or glands).
Q: What is the role of neurotransmitters in sensory neurons?
A: To transmit signals from sensory neurons to interneurons in the CNS at synapses.
Q: How do interneurons use neurotransmitters?
A: To relay signals to other neurons, including motor neurons, after processing sensory information.
Q: What is the role of neurotransmitters in motor neurons?
A: To stimulate muscle contraction or gland secretion at neuromuscular junctions.
Q: What is a neuromuscular junction?
A: The synapse where motor neurons release neurotransmitters to stimulate muscles or glands.
Q: What is the overall importance of neurotransmitters in the nervous system?
transmission of sensory information, processed signals, and motor commands through synapses.
Q: What is the primary function of sensory neurons?
A: To detect stimuli and generate nerve impulses.
Q: What is the primary function of interneurons?
A: To process incoming sensory information and decide on appropriate responses.
Q: What is the primary function of motor neurons?
A: To send motor impulses to effectors (muscles or glands).
Q: Where do neurotransmitters function in the nervous system?
A: At synapses between neurons and at neuromuscular junctions.
Q: What is a motor unit?
A: One motor neuron and all the muscle fibers it connects to.
Q: What happens when a motor neuron sends a signal?
A: It activates all muscle fibers in its motor unit simultaneously, leading to muscle contraction.
Q: What is neuroglia?
A: Support cells in the nervous system that make up about half of the CNS’s volume.
Q: What are two key differences between neuroglia and neurons?
A: Neuroglia can multiply and divide, and they don’t conduct nerve impulses.
Q: How many types of neuroglia are there and where are they found?
A: Six types total: four in CNS (astrocytes, oligodendrocytes, microglia, ependymal cells) and two in PNS (Schwann cells, satellite cells).
Q: What happens when neurons die?
A: Neuroglia fills in the spaces left by the dead neurons.
Q: What is a glioma?
A: A usually malignant brain tumor formed from glial cells.
Q: What are two key characteristics of neuroglia?
A: They are not electrically excitable and do not transmit action potentials.
Q: How do neuroglia compare in size to neurons?
A: They are smaller than neurons but more numerous.
Q: What are the functions of astrocytes?
A: Provide structural support, maintain the blood-brain barrier, guide neuron growth, regulate chemical balance, and influence synapse formation.
Q: What is the role of oligodendrocytes in the CNS?
A: To form and maintain the myelin sheath around CNS axons, insulating them and speeding up nerve impulse transmission.
Q: What is the myelin sheath and its function?
A: A multi-layered lipid and protein covering that insulates axons and increases the speed of action potentials.
Q: What are ependymal cells responsible for?
A: Producing and monitoring cerebrospinal fluid (CSF), which protects and nourishes the spinal cord and brain.
Q: What is the function of microglia?
A: They act as phagocytes, clearing away cellular debris and microbes in the CNS.
Q: What is the role of Schwann cells in the PNS?
A: To encircle PNS axons and form myelin sheaths, aiding in axon regeneration.
Q: What do satellite cells do in the PNS?
A: Provide structural support and regulate nutrient exchange between neurons and interstitial fluid.
Q: What are the two types of astrocytes, and where are they found?
A: Protoplasmic astrocytes (in gray matter) and fibrous astrocytes (mainly in white matter).
Q: How do ependymal cells contribute to brain protection?
A: They form a barrier between blood and cerebrospinal fluid (CSF) and circulate CSF in the ventricles of the brain.
Q: What is the appearance of microglial cells?
A: Small cells with slender, spinelike projections that resemble macrophages in function and structure.
Q: What does myelinated mean?
A: Axons that are covered by a myelin sheath, which insulates and speeds up nerve signals.
Q: What cells produce myelin in the PNS vs. CNS?
A: Schwann cells in the PNS; oligodendrocytes in the CNS.
Q: How do Schwann cells differ from oligodendrocytes in myelination?
A: Schwann cells wrap around one axon segment, while oligodendrocytes cover parts of several axons.
Q: What are nodes of Ranvier?
A: Gaps between myelin segments that help speed impulse conduction.
Q: Why is regeneration more effective in the PNS?
A: Due to the presence of the neurolemma (peripheral nucleated cytoplasmic layer of Schwann cells).
Q: What is the neurolemma?
A: The peripheral, nucleated cytoplasmic layer of the Schwann cell.
Q: How does myelination change from birth?
A: It increases over time, improving nerve signal speed and coordination.
Q: How do Schwann cells aid in axon repair?
A: By forming a regeneration tube.
Q: Why is repair limited in the CNS?
A: Because oligodendrocytes lack a neurolemma.
most axons in CNS & PNS are ____.
Myelinated
Most axons found in the autonomic nervous system are ___.
unmeylinated
What types of cells form the myelin sheath?
Schwann cells and oligodendrocytes
where are schwann cells found?
PNS
what does each schwann cell myelinate?
a single axon segment.
where are oligodendrocytes found?
found in the central nervous system (CNS).
what can each oligodendrocyte myelinate?
parts of multiple axons.
Q: What are the three stages of myelin sheath formation?
A:
1. Initial stage (Schwann cell begins wrapping)
2. Progressing stage (multiple membrane layers form spiral)
3. Final stage (complete sheath with neurolemma and nodes of Ranvier)
Q: What defines whether an axon is myelinated or unmyelinated?
A: Myelinated axons have a myelin sheath covering; unmyelinated axons do not.
Q: How do Schwann cells and oligodendrocytes differ in myelination?
A: Schwann cells wrap around one axon segment with a neurolemma, while oligodendrocytes cover multiple axons without a neurolemma.
Q: What is the significance of the neurolemma?
A: It helps repair the axon and is present only in PNS (Schwann cells).
Q: Why do infants have slower responses than adults?
A: Due to incomplete myelination, which develops progressively from birth to adulthood.
Q: What happens during the progressing stage of myelination?
A: The Schwann cell wraps multiple layers of its membrane around the axon in a spiral pattern.
Q: What is formed in the final stage of myelination?
A: A complete myelin sheath with the neurolemma as the outer layer and nodes of Ranvier between successive Schwann cells.
Q: What is the primary function of myelin?
A: To increase the speed of nerve impulse transmission.
Q: What are nodes of Ranvier and why are they important?
A: Gaps along the myelinated axon that aid in speeding up nerve impulses.
what is the myeline sheath?
is a lipid and protein covering around axons that increases nerve impulse speed. Axons with this sheath are “myelinated”; those without are “unmyelinated.“
Q: What is Multiple Sclerosis (MS)?
A: An autoimmune disease that progressively destroys myelin sheaths around neurons in the CNS.
Q: How many people are affected by MS?
A: About 350,000 people in the U.S. and 2 million worldwide.
Q: What causes MS?
A: Exact cause is unclear but may involve both genetic and environmental factors, possibly including herpes virus as a trigger.
Q: What are the main symptoms of MS?
A: Muscle weakness, abnormal sensations, and double vision.
Q: What is the most common form of MS?
A: Relapsing-remitting MS.
Q: What happens in relapsing-remitting MS?
A: Attacks of symptoms followed by periods of remission, typically occurring every year or two.
Q: What are scleroses in MS?
A: Hardened scars that form and disrupt nerve signal transmission.
Q: How does MS affect the nervous system?
A: The immune system attacks myelin sheaths, disrupting normal nerve signal transmission.
Q: What is the nature of MS as a disease?
A: It’s an autoimmune disease where the body’s immune system attacks its own myelin.
Q: What are nodes of Ranvier?
A: Gaps between myelin sheaths where the axon is exposed, containing ion channels for sodium and potassium.
Q: What type of ion channels are found in nodes of Ranvier?
A: Voltage-gated sodium (Na+) channels.
Q: What is saltatory conduction?
A: The process where nerve impulses “jump” from one node of Ranvier to the next along a myelinated axon.
Q: How do nodes of Ranvier increase signal transmission speed?
A: By allowing action potentials to jump between nodes rather than traveling along the entire axon length.
Q: What is the main function of myelin sheaths between nodes?
A: To insulate the axon and speed up transmission of nerve impulses.
Q: What ions are exchanged at the nodes of Ranvier?
A: Sodium (Na+) and potassium (K+) ions.
Q: Why is saltatory conduction more efficient than continuous conduction?
A: Because the signal jumps between nodes rather than traveling the entire length of the axon, making transmission faster.
Q: What makes saltatory conduction possible?
A: The combination of myelinated sections and exposed nodes of Ranvier with ion channels.
Q: What are the three major factors affecting nerve impulse speed?
A: 1. Amount of myelination 2. Axon diameter 3. Temperature
Q: How does axon diameter affect nerve impulse speed?
A: Larger diameter axons propagate action potentials faster due to larger surface areas.
Q: How does myelination affect nerve impulse speed?
A: More myelin increases the speed of action potentials.
Q: How does temperature affect nerve impulse speed?
A: Higher temperatures increase the speed of action potentials; lower temperatures decrease speed.
Q: Why might temperature effects on nerve impulse speed be relevant to warm-up?
A: Because warming up increases temperature, which could increase nerve impulse speed.
Q: Which type of axon conducts nerve impulses faster?
A: Myelinated axons conduct faster than unmyelinated axons.
Q: What happens to nerve impulse speed when an axon is cooled?
A: The speed decreases.
Q: Why do larger diameter axons conduct faster?
A: Because they have larger surface areas for impulse propagation.
Q: What are the two types of electrical signals used by neurons for communication?
A: Graded potentials and action potentials (nerve impulses).
Q: What is the function of graded potentials?
A: To transmit short-distance signals within a neuron.
Q: What is the function of action potentials?
A: To transmit long-distance signals along the axon.
Q: How do graded potentials differ from action potentials?
A: Graded potentials vary in magnitude and can decay over distance, while action potentials are all-or-nothing and propagate without decay.
Q: Where do graded potentials typically occur?
A: At the dendrites or cell body of a neuron.
Q: Where do action potentials occur?
A: Along the axon of a neuron, especially at the axon hillock after summation of graded potentials.
Q: How are graded potentials initiated?
A: By stimuli such as neurotransmitters binding to receptors or sensory input.
Q: What is the minimum threshold that must be reached for an action potential to occur?
A: A critical level of depolarization, known as the threshold potential.
Q: What are the two main features of excitable cell membranes that underlie graded potentials and action potentials?
A: Resting membrane potential and specific ion channels.
Q: What is the resting membrane potential?
A: The electrical difference (voltage) across the membrane when a neuron is not actively transmitting signals, similar to voltage in a battery.
Q: How does current flow in excitable cells?
A: Current flows through the movement of ions, not electrons, across the cell membrane.
Q: What allows graded potentials and action potentials to occur in neurons?
A: The presence of various ion channels that open or close in response to specific stimuli.
Q: Why is the lipid bilayer of the plasma membrane a good insulator?
A: It prevents the free flow of ions, making ion channels the primary pathways for ion movement across the membrane.
Q: What is the role of ion channels in neuron signaling?
A: Ion channels facilitate the movement of ions across the membrane, which is essential for generating and propagating electrical signals in neurons.
Q: How does the flow of ions relate to the concept of a battery?
A: Just as a battery allows current to flow when connected, the resting membrane potential creates an environment for ions to flow, generating electrical currents in excitable cells.
Q: What happens to ion channels in response to specific stimuli?
A: They open or close, allowing ions to enter or exit the neuron, which can alter the membrane potential and initiate graded potentials or action potentials.
Q: What are the key characteristics of an action potential?
A:
- All-or-nothing response
- Same strength every time
- Travels in one direction
- Allows long-distance communication
Q: What is the sequence of ion channel changes during an action potential?
A:
1. Sodium channels open (ions rush in)
2. Depolarization occurs
3. Potassium channels open (ions flow out)
4. Repolarization returns cell to resting state
Q: What happens at neuromuscular junctions?
A: Action potential triggers neurotransmitter release, which crosses synapse to muscle fiber and causes contraction.
Q: How does depolarization occur?
A: Sodium channels open, allowing positive ions to rush in, making the membrane more positive.
Q: What is repolarization?
A: The process of returning to resting state when potassium channels open and positive ions flow out.
Q: How does an action potential move along an axon?
A: It travels like a wave through sequential ion channel changes.
Q: Why is the action potential’s “all-or-nothing” nature important?
A: It ensures consistent signal strength and reliable communication throughout the nervous system.
Q: What makes neural communication effective?
A: It allows for rapid communication throughout body, precise muscle control, and coordinated responses to stimuli.
Q: How do motor axons control muscles?
A: One motor axon can connect to multiple muscle fibers through neuromuscular junctions, allowing coordinated muscle control.
