Chapter 12: Nervous Tissue Flashcards
What role does nervous tissue play in homeostasis?
Nervous tissue helps maintain homeostasis by generating nerve impulses (action potentials) that regulate body organs.
How does the nervous system differ from the endocrine system in maintaining homeostasis?
The nervous system acts quickly through nerve impulses, while the endocrine system uses hormones to maintain homeostasis.
What is the study of the nervous system’s functions and disorders called?
Neurology.
What are the two main parts of the nervous system?
The Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
What is the primary function of the CNS?
The CNS processes sensory information and is the center for thoughts, emotions, memories, and signals controlling muscle movement and gland secretion.
What does the PNS consist of?
The PNS consists of all nervous tissue outside the CNS, including cranial and spinal nerves.
What are sensory receptors?
Sensory receptors are structures that monitor changes in the internal or external environment and send sensory information to the CNS.
What are the two divisions of the PNS?
The sensory (afferent) division and the motor (efferent) division.
What is the function of the sensory (afferent) division of the PNS?
It sends sensory information from the body’s receptors to the CNS.
What is the role of the motor (efferent) division of the PNS?
It sends signals from the CNS to effectors like muscles and glands.
What does the somatic nervous system (SNS) control?
The SNS controls voluntary actions of skeletal muscles.
What is the autonomic nervous system (ANS) responsible for?
The ANS controls involuntary actions of smooth muscles, cardiac muscles, and glands.
What are the three subdivisions of the ANS?
The sympathetic nervous system, parasympathetic nervous system, and enteric nervous system.
How do the sympathetic and parasympathetic nervous systems differ in function?
The sympathetic nervous system is responsible for “fight-or-flight” responses, while the parasympathetic nervous system controls “rest-and-digest” activities.
What are the three main functions of the nervous system?
Sensory function, integrative function, and motor function.
What does the sensory function of the nervous system involve?
Sensory receptors detect stimuli (e.g., changes in blood pressure or external sensations) and send this information to the CNS.
What occurs during the integrative function of the nervous system?
The nervous system processes and analyzes sensory information to decide how to respond.
What is the motor function of the nervous system?
The motor function involves sending signals to muscles or glands to trigger actions like muscle contractions or gland secretions.
Provide an example of the three main functions of the nervous system.
When a phone rings:
- Sensory: Ears detect the sound.
- Integrative: The brain processes the information and decides to answer.
- Motor: The brain sends signals to muscles to pick up the phone and press the answer button.
What are the two types of cells in nervous tissue?
Neurons and neuroglia.
What is the role of neurons?
Neurons connect all regions of the body to the brain and spinal cord, enabling functions like sensing, thinking, remembering, controlling muscles, and regulating glands.
What is the role of neuroglia?
Neuroglia support, nourish, protect neurons, and maintain the fluid around them. They can divide throughout life.
How do the structure of neurons and neuroglia differ in the CNS and PNS?
The structure varies to reflect their different roles in the central and peripheral nervous systems.
What is electrical excitability in neurons?
Neurons have the ability to respond to stimuli and generate action potentials, which are electrical signals that travel along their membranes.
What is an action potential?
An action potential is an electrical signal that travels along the neuron’s membrane, caused by the movement of ions like sodium and potassium.
How fast can a nerve impulse travel?
Nerve impulses can travel at speeds ranging from 0.5 to 130 meters per second (1 to 290 mph).
What are the three main parts of a neuron?
The cell body (soma), dendrites, and axon.
What is the function of the cell body in a neuron?
The cell body contains the nucleus, cytoplasm, and organelles, and it supports neuron growth and repairs damaged axons in the PNS.
What are dendrites?
Dendrites are short, branched extensions that receive signals from other neurons.
What is the function of the axon?
The axon transmits nerve impulses away from the neuron to other cells.
What is the role of neurofibrils and microtubules in neurons?
Neurofibrils provide shape and support, while microtubules help move materials between the cell body and axon.
What is lipofuscin and how does it affect neurons?
Lipofuscin is a pigment that accumulates in neurons as they age but does not harm them.
What is a ganglion?
A ganglion is a collection of neuron cell bodies outside the CNS.
What is the difference between dendrites and axons?
Dendrites receive signals, while axons transmit nerve impulses.
What is a synapse?
A synapse is the communication site between two neurons or between a neuron and an effector cell.
What are synaptic end bulbs and varicosities?
They are structures at the ends of axons that contain synaptic vesicles, which store neurotransmitters.
What are neurotransmitters?
Neurotransmitters are chemicals released from synaptic vesicles that affect the activity of other cells.
What is slow axonal transport?
Slow axonal transport moves materials from the cell body to the axon terminals at a rate of 1–5 mm per day.
What is fast axonal transport?
Fast axonal transport moves materials from the cell body to the axon terminals at 200–400 mm per day, and it can occur in both directions.
What are the two types of axonal transport?
Slow axonal transport (moves materials in one direction) and fast axonal transport (moves materials in both directions).
What is the structural diversity of neurons?
Neurons vary in size and shape, including the size of the cell body, dendritic branching, and axon length.
What are multipolar neurons?
Multipolar neurons have many dendrites and one axon. They are common in the brain and spinal cord.
What are bipolar neurons?
Bipolar neurons have one dendrite and one axon. They are found in areas like the retina, inner ear, and olfactory region of the brain.
What are unipolar (pseudounipolar) neurons?
Unipolar neurons have a single process that splits into dendrites and an axon. They are primarily sensory neurons.
What are Purkinje cells?
Purkinje cells are large neurons in the cerebellum with elaborate dendritic branching.
What are pyramidal cells?
Pyramidal cells are neurons in the cerebral cortex with pyramid-shaped cell bodies.
What are sensory neurons (afferent neurons)?
Sensory neurons transmit information from sensory receptors to the CNS and are typically unipolar.
What are interneurons (association neurons)?
Interneurons process sensory information and generate motor responses, primarily in the CNS. They are usually multipolar.
What are motor neurons (efferent neurons)?
Motor neurons transmit action potentials from the CNS to effectors (muscles or glands) in the PNS. They are typically multipolar.
What are gliomas?
Gliomas are brain tumors that arise from glial cells, are highly malignant, and grow rapidly.
What are the types of neuroglia in the CNS?
Astrocytes, oligodendrocytes, microglia, and ependymal cells.
What is the function of astrocytes?
Astrocytes provide structural support, maintain the blood-brain barrier, and regulate the chemical environment of the brain.
What are the two types of astrocytes?
Protoplasmic astrocytes (found in gray matter) and fibrous astrocytes (found in white matter).
What are oligodendrocytes?
Oligodendrocytes produce myelin sheaths around CNS axons.
What are microglia?
Microglia act as immune cells in the CNS, responding to injury and disease.
What are ependymal cells?
Ependymal cells line the ventricles of the brain and help produce cerebrospinal fluid (CSF).
What are Schwann cells?
Schwann cells myelinate PNS axons.
What are satellite cells?
Satellite cells provide support and nutrients to neurons in the PNS.
What is myelination?
Myelination is the process where axons are surrounded by a multilayered lipid and protein covering, the myelin sheath, which electrically insulates the axon and speeds up nerve impulse conduction.
What cells produce myelin in the PNS?
Schwann cells produce myelin in the PNS.
What cells produce myelin in the CNS?
Oligodendrocytes produce myelin in the CNS.
How do Schwann cells form myelin?
Schwann cells start forming myelin sheaths during fetal development by wrapping around a single axon, creating multiple layers of membrane, and forming the neurolemma in the PNS.
What is the neurolemma?
The neurolemma is the outer layer of a Schwann cell’s cytoplasm and nucleus, found only in the PNS.
What happens if an axon is injured in the PNS?
If an axon is injured, the neurolemma helps regenerate the axon by forming a tube that guides and stimulates regrowth.
What are Nodes of Ranvier?
Nodes of Ranvier are gaps in the myelin sheath at intervals along the axon, allowing for faster nerve impulse conduction.
How do oligodendrocytes myelinate axons in the CNS?
Oligodendrocytes extend flat processes that wrap around multiple CNS axons to form a myelin sheath, but do not create a neurolemma.
Why is there limited regrowth in the CNS?
Limited regrowth occurs in the CNS due to the absence of a neurolemma and the inhibitory effect of oligodendrocytes.
How does myelination affect the speed of nerve impulses?
Myelination significantly increases the speed of nerve impulse conduction, which improves coordination as myelination develops from infancy to maturity.
What is the difference between gray and white matter?
Gray matter contains neuronal cell bodies, dendrites, and unmyelinated axons, while white matter is made up of myelinated axons.
What are ganglia?
Ganglia are groups of neuronal cell bodies located in the PNS, often associated with cranial and spinal nerves.
What is a nucleus in the context of the nervous system?
A nucleus is a cluster of neuronal cell bodies located in the CNS.
What is the difference between nerves and tracts?
Nerves are bundles of axons in the PNS, while tracts are bundles of axons in the CNS.
What is the role of gray matter?
Gray matter is involved in processing and integrating information and contains cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia.
What is the role of white matter?
White matter is responsible for transmitting nerve impulses between different parts of the nervous system, consisting of myelinated axons.
How does the distribution of gray and white matter differ in the brain and spinal cord?
In the spinal cord, white matter surrounds an inner core of gray matter. In the brain, gray matter covers the cerebrum and cerebellum, while white matter lies beneath.
What are graded potentials?
Graded potentials are small electrical changes used for short-distance communication in neurons.
What are action potentials?
Action potentials are large electrical signals used for long-distance communication within the body, also known as nerve impulses.
What are the two key features of excitable cells that generate electrical signals?
Resting membrane potential and ion channels are key features that allow excitable cells to generate electrical signals.
What are ion channels?
Ion channels are proteins in the plasma membrane that allow specific ions to flow across the membrane, generating electrical currents.
What is the difference between concentration and electrical gradients in ion movement?
Ions move from areas of higher to lower concentration (concentration gradient) and from positively charged areas to negatively charged areas (electrical gradient).
What are leak channels?
Gated channels that randomly open and close.
Where are leak channels located in neurons?
Found in nearly all cells, and in the dendrites, cell bodies, and axons of all types of neurons.
What are ligand-gated channels?
Gated channels that open in response to the binding of a ligand (e.g., Acetylcholine).
Where are ligand-gated channels located in neurons?
Found in the dendrites of some sensory neurons like pain receptors, and in the dendrites and cell bodies of interneurons and motor neurons.
What are mechanically gated channels?
Gated channels that open in response to a mechanical stimulus, such as touch, pressure, vibration, or tissue stretching.
Where are mechanically gated channels located in neurons?
Found in the dendrites of some sensory neurons like touch receptors, pressure receptors, and some pain receptors.
What are voltage-gated channels?
Gated channels that open in response to a voltage stimulus (change in membrane potential).
Where are voltage-gated channels located in neurons?
Located in the axons of all types of neurons.
What causes the resting membrane potential in neurons?
The resting membrane potential arises from a slight accumulation of negative ions in the cytosol and positive ions in the extracellular fluid (ECF), creating potential energy.
