The Nervous System Flashcards
What are the three functions of the nervous system?
- Monitor the body’s internal and external environments.
- Integrate sensory information.
- Direct or coordinate the responses of other organ systems to the sensory input.
What are the major divisions of the nervous system?
- The central nervous system.
- The peripheral nervous system:
The ____ consists of the brain and spinal cord, which occupy the ___ body cavity.
Central nervous system, dorsal.
The integrating and command center of the nervous system - it interprets sensory input and dictates motor responses based on past experience, reflexes and current conditions.
Central nervous system.
The part of the nervous system outside of the CNS, and consists mainly of the nerves that extend from the brain and spinal cord.
Peripheral nervous system.
Carry impulses to and from the spinal cord.
Spinal nerves.
Carry impulses to and from the brain.
Cranial nerves
What are the sub-divisions of the peripheral nervous system?
- The sensory (afferent) division.
- The motor (efferent) division.
Consists of nerve fibers that convey impulses to the central nervous system from sensory receptors located throughout the body.
Sensory (afferent) division.
Sensory fibers conveying impulses from the skin, skeletal muscles, and joints are called ___.
Somatic afferent fibers.
Fibers transmitting impulses from the visceral organs (organs within the ventral body cavity) are called _____.
Visceral afferent fibers.
Transmits impulses from the CNS to effector organs, which are the muscles and glands.
The motor (efferent) division.
The ______ is composed of axons that conduct impulses from the CNS to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.
Somatic nervous system.
Consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. This system is also referred to as the involuntary nervous system.
Autonomic nervous system.
What are the two divisions of the autonomic nervous system?
The sympathetic and the parasympathetic.
Mobilizes body systems during activity.
The sympathetic division of the ANS.
Conserves energy and promotes housekeeping functions during rest.
The parasympathetic division of the ANS.
How many neuroglia are there in the CNS?
Four.
How many neuroglia are there in the PNS?
Two.
What are the different neuroglia found in the central nervous system?
Astrocytes, microglia, ependymal cells, and oligodendrocytes.
Shaped like delicate branching sea anemones, ____ are the most abundant and most versatile glial cells.
Astrocytes.
____ are small ovoid cells with relatively long “thorny” processes.
Microglia.
Their processes touch nearby neurons, monitoring their health, and when they sense that certain neurons are injured or in other trouble, the ____ migrate towards them.
Microglia.
_____ range in shape from squamous to columnar, and many are ciliated.
Ependymal cells.
They line the central cavities of the brain and the spinal cord, where they form a fairly permeable barrier between the cerebrospinal fluid that cushions the brain and spinal cord.
Ependymal cells.
Though they also branch, the ____ have fewer processes than astrocytes.
Oligodendrocytes.
They line up along the thicker neuron fibers in the CNS and wrap their processes around the fibers, producing insulating coverings called myelin sheaths.
Oligodendrocytes.
Their numerous radiating processes cling to neurons and their synaptic endings, and cover nearby capillaries, supporting and bracing the neurons and anchoring them to their nutrient supply lines. They have a role in making exchanges between capillaries and neurons, in guiding the migration of young neurons, in synapse formation, and in helping to determine capillary permeability.
Astrocytes.
What are the two kinds of PNS neuroglia?
Satellite cells and Schwann cells.
___ surround neuron cell bodies located in the peripheral nervous system, but their function is still largely unknown.
Satellite cells.
____ surround and form myelin sheaths around the larger nerve fibers in the peripheral nervous system - they are vital to regeneration of damaged peripheral nerve fibers.
Schwann cells.
A chronic potentially debilitating disease that affects the myelin sheath of the central nervous system. Believed to be an autoimmune disease, the body directs antibodies and white blood cells against proteins in the myelin sheath surrounding nerves in the brain and spinal cord, which causes inflammation and injury to the myelin sheath.
Multiple sclerosis.
What structure/tissue is affected by multiple sclerosis?
Myelin sheath.
The billions of ___, also called nerve cells, are the structural units of the nervous system. They are highly specialized cells that conduct messages in the form of nerve impulses from one part of the body to another.
Neurons.
The ___ consists of a transparent spherical nucleus with a conspicuous nucleus surrounded by cytoplasm. The cells body ranges in diameter from 5 to 140 um. Except for centrioles, it contains the usual organelles.
Neuron cell body.
Bundles of neuron processes in the CNS.
Tracts.
Bundles of neuron processes in the PNS.
Nerves.
___ of motor neurons are short, tampering, diffusely branching extensions. They are the main receptive or input regions. They bristle with thorny appendages having bulbous or spiky ends, which represent close points of contact with other neurons. They convey incoming messages toward the cell body, known as graded potentials.
Dendrites.
Each neuron has a single ___. The initial region arises from a cone shaped area of the cell body, and then narrows to form a slender process that is uniform in diameter for the rest of it’s length. In some neurons, it is very short or absent; in others, it is long and accounts for nearly the entire length of the neuron. Any long ___ is called a nerve fiber.
Axon.
These neurons have three or more processes. They are the most common neuron type in humans, and the major neuron type in the CNS.
Multipolar.
These neurons have two processes - an axon and a dendrite - that extend from opposite sides of the cell body. These rare neurons are found in some of the special sense organs. Examples include some neurons in the retina of the eye and in the olfactory mucosa.
Bipolar neurons.
These neurons have a single short process that emerges from the cell body and divides T-like into proximal and distal branches. The more distal process is often associated with a sensory receptor, known as the peripheral process, whereas that entering the CNS is the central process. These neurons are more accurately called pseudo because they originate as bipolar neurons.
Unipolar.
These neurons transmit impulses from sensory receptors in the skin or internal organs toward or into the central nervous system. Except for certain neurons found in some special sense organs, nearly all of these neurons are unipolar.
Sensory (afferent) neurons.
These neurons carry impulses away from the CNS to the effector organs (muscles and glands) of the body periphery. These neurons are multipolar, and except for some neurons of the autonomic nervous system, their cell bodies are located in the CNS.
Motor (efferent) neurons.
These neurons lie between motor and sensory neurons in neural pathways and shuttle through CNS pathways where integration occurs. Most of these neurons are confined within the CNS, and make up over 99% of the neurons in the body, including most of those in the CNS. Almost all of them are multipolar, but there is considerable diversity in both size and fiber-branching patterns.
Interneurons.
Where are sensory neurons found?
In sensory ganglia outside the CNS.
Where are motor neurons found?
Inside the CNS.
Where are interneurons found?
Confined within the CNS.
Periodic gaps in the insulating myelin sheaths of myelinated axons where the axonal membrane is exposed to the extracellular space.
Nodes of Ranvier.
How do Schwann cells form the myelin sheath and the neurilemma?
- To make the myelin sheath, Schwann cells wrap around an axon in a jelly roll fashion, and one cell forms one segment of myelin sheath.
- Neurilemma is the peripheral bulge of a Schwann cell, containing the nucleus and most of the cytoplasm of the Schwann cell.
Small cells that surround and wrap delicate neurons.
Neuroglia.
Excitable cells that transmit electrical signals.
Neurons.
Regions of brain and spinal cord with dense
collections of myelinated fibers – usually fiber tracts
White matter.
Mostly neuron cell bodies and nonmyelinated fibers
Gray matter.
How do PNS nerve fibers regenerate?
- Separate ends seal themselves off, then swell.
- The axon and its myelin sheath distal to the injury site begin to disintegrate because they cannot recieve nutrients.
- The entire axon distal to the injury is degraded by phagocytes within a week.
- Surviving Schwann cells proliferate in response to the mitosis-stimulating chemicals released by macrophages
- Schwann cells release growth factors to stimulate axonal growth.
- Sprouts form on stumps of damaged nerve fibers, some grow into the endoneurial tubes
- As fibers grow in endoneurial tubes, Schwann cells surround and remyelinate regenerating axons.
- Increased blood supply to area where nerve is reaching.
- Sensory and motor functions return.
Why can’t CNS neurons regenerate their fibers?
No Neurilemma is present to form a regeneration tube to guide growth of a severed axon
What is a synapse?
Functional junction or point of close contact between two neurons or between a neuron and an effector cell.
What is a ganglion?
A collection of nerve cell bodies outside of the CNS.
a complex system of nerves and networks in the brain, involving several areas near the edge of the cortex concerned with instinct and mood. It controls the basic emotions (fear, pleasure, anger) and drives (hunger, sex, dominance, care of offspring).
The limbic system.
What is saltatory conduction?
the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
What 2 factors influence impulse speed?
Myelin sheath and axon size.
How does a nervous impulse cross a chemical synapse?
One neuron releases chemicals in response to an action potential (nerve impulse). The chemicals travel across the synapse and stimulate an action potential in the next neuron.
How does a nervous impulse cross an electrical synapse?
In an electrical synapse, gap junctions, which are formed by the channel proteins connecting the presynaptic and postsynaptic membranes of two neurons, allow the current to pass directly from one neuron to the next.
Distinguish between a graded potential and an action potential?
Depending on the stimulus, graded potentials can be depolarizing or hyperpolarizing. Action potentials always lead to depolarization of membrane and reversal of the membrane potential.
What ions are involved in creating action potentials, and resting potentials?
Sodium and potassium.
Explain how a cell membrane becomes polarized:
An electrical signal is generated when the neuron allows sodium ions to flow into it, which switches the charges on either side of the cell membrane. This switch in charge is called depolarization. In order to send another electrical signal, the neuron must reestablish the negative internal charge and the positive external charge. This process is called repolarization.
What is the resting potential?
The resting membrane potential of a neuron is about -70 mV - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
What is the Reticular Activating System?
The part of the reticular formation in the brainstem that plays a central role in bodily and behavioral alertness; its ascending connections affect the function of the cerebral cortex and its descending connections affect bodily posture and reflex mechanisms.
What are the three layers of the meninges?
- Dura Mater.
- Arachnoid Mater.
- Pia Mater.
What neuronal structures are found in the ganglion?
The Soma.
What is the neural tube/crest and what does it develop?
A dorsal tubular structure in the vertebrate embryo that develops into the brain and spinal cord. A tubular structure that results from the folding of tissue along the back of vertebrate embryos and develops into the brain and spinal cord.
What are the general functions of the cerebrum?
- Conscious thought.
- Memory storage and processing.
- Sensory processing.
- Regulating skeletal muscle contractions.
What are the general functions of the diencephalon?
The structural and functional link between the cerebral hemispheres and the rest of the CNS - the link between the nervous and endocrine systems.
What are the general functions of the midbrain?
- Regulates auditory and visual reflexes.
- Controls alertness.
- Can direct complex motor patterns at the subconscious level.
- Influences the level of activity in the entire nervous system.
What are the general functions of the pons?
- Connects the cerebellum to the brain stem.
- Contains nuclei that function in somatic and visceral motor control.
What are the general functions of the medulla oblongata?
- Relays sensory information to other portions of the brain stem and to the thalmus.
- Regulate autonomic function, such as heart rate and blood pressure.
What are the general functions of the cerebellum?
- Coordinating and modulating motor commands from the cerebral cortex.
- Adjusting the postural muscles of the body.
- Programming and fine tuning movements controlled at the conscious and subconscious levels.
What connects the two hemispheres of the cerebrum?
Corpus callosum.
What are the general functions of the brain stem?
The brain stem has many basic functions, including regulation of heart rate, breathing, sleeping, and eating.
What are the functions of the thalamus?
- Involved in sensory and motor signal relay.
- Regulation of consciousness and sleep.
- All senses, excluding smell.
- Controlling the motor systems of the brain which are responsible for voluntary bodily movement and coordination.
What are the functions of the hypothalamus?
i. Centers controlling emotions, autonomic functions, and hormone production, appetite.
ii. In both the nervous and endocrine systems.
Creates hormones that are sent to the pituitary gland.
What are the functions of the pineal gland?
secretes hormone melatonin, regulates sleep
What is the fifth lobe?
Insula.
What are the four major lobes of the cerebrum?
Frontal, parietal, temporal, occipital.
