Flashcards in Exam 2 Part two Deck (107):
Prime movers are
Also called agonist. A muscle that contracts to produce a particular movement, such as extending the forearm. The triceps brachii of the posterior arm is an agonist that causes forearm extension
A muscle whose actions oppose those of the agonist. The contraction of the agonist stretches the antagonist, & vise versa
A muscle that assists the agonist in performing its action. The contraction of a synergist usually either contributes to tension exerted close to the insertion of the muscle or stabilized the point of origin
How are the biceps brachia & triceps brachia act as agonist & antagonist?
When the triceps brachia acts as an agonist to extend the forearm, the biceps brachia on the anterior side of the humerus acts as an antagonist to stabilized the movement & produce the opposing action, which is flexion of the forearm
When are synergists most useful?
At the start of a movement when the agonist is stretched & cannot exert more power
What are some examples of synergist muscles?
The biceps brachii & brachialis muscles of the arm. Both muscles work synergistically "together" to flex the elbow joint
Synergists may also assist an agonist by?
Preventing movement at a joint & thereby stabilizing the origin of the agonist
How many levers are found in the human body?
Three classes of levers; first-class, second-class, and third-class
Has a fulcrum in the middle, between the effort & the resistance
An example of first-class levers are?
A pair of scissors. The effort is applied to the handle of the scissors while the resistance is at the cutting end of the scissors. The fulcrum (pivot for movement) is along the middle of the scissors, between the handle & the cutting ends
What is an example of a first-class lever in the body?
The atlanto-occipital joint of the neck, where the muscles on the posterior side of the neck pull inferiorly on the nuchal lines of the skull & oppose the tendency of the head to tip anteriorly
The resistance in a second-class lever is between the
Fulcrum & the applied effort
A common example of second class lever is
Lifting the handles of a wheelbarrow, allowing it to pivot on its wheel at the opposite end & lift a load in the middle.
An example of second-class lever in the body is?
They are rare, but occurs when the foot is depressed so that a person can stand on tiptoe. The contraction of the calf muscles causes a pull superiorly by the calcaneal tendon attached to the heel (calcaneus)
Third class levers are
An effort is applied between the resistance & the fulcrum, as when picking up a small object with a pair of forceps. These are the most common levers in the body
An example of third class levers found in the body is?
Found at the elbow, where the fulcrum is the joint between the humerus & ulna. The effort is applied by the biceps brachii muscle, & the resistance is provided by any weight in the hand, or by the weight of the forearm itself
How does the mandible act as a third class lever?
When you bite w/ your incisors on a piece of food. The temporomandibular joint is the fulcrum, & the temporal is muscle exerts the effort, while the resistance is the item of food being bitten
What are the 3 types of pennate muscles?
Unipennate muscle, bipennate, & multipennate
Unipennate muscle is
All of the muscle fibers are on the same side of the tendon. The extensor digitorum, a long muscle that extends the fingers, is a unipennate
Bipennate muscle is
The most common type, has muscle fibers on both sides of the tendon. The palmar & dorsal interosseous muscles that attach to the metacarpals are composed of bipennate muscle that helps adduct and abduct the digits
Has branches of the tendon w/in the muscle. The triangular deltoid that covers the shoulder joint is a multipennate muscle
Has widespread muscle fibers that converge on a common attachment site. This attachment site may be a single tendon, a tendinous sheet, or a slender band of collagen fibers (raphe). These muscle fibers are often triangular in shape, resembling a broad fans/a tendon at the tip
How is convergent muscle versatile?
The direction of its pull can be modified merely by activating a single group of muscle fibers at one time
An example of a convergent muscle is?
The pectoralis major of the chest
Red fibers are
Also called slow fibers. They are called red fibers because they contain the pigmented myoglobin which is a globular O2 binding, reddish-appearing protein that is structurally related to hemoglobin
White fibers are
Also called fast fibers. They are white because they are pale in color due to their lack of myoglobin
Intermediate fibers are
Exhibit properties that are somewhere between those of slow fibers & fast fibers. These fibers contract faster than the slow & slower than the fast fibers. They resemble fast fiber, however, they have a greater resistance to fatigue
An elongated, rigid object that rotates around a fixed point called a fulcrum. They have the ability to change the speed & distance of movement produced by a force, the direction of an applied force, & the force strength
Both slow & intermediate fibers require O2 to produce ATP, so the metabolic reactions w/in these fibers are termed aerobic
Central nervous system (CNS)
Composed of the brain & spinal cord. Command center of the nervous system that integrates & processes nervous information
Where are the brain & spinal cord housed?
The brain is protected & enclosed w/in the skull, while the spinal cord is housed & protected w/in the vertebral canal
Peripheral nervous system (PNS)
Includes the cranial nerves (nerves that extend from the brain), spinal nerves (nerves that extend from the spinal cord), & ganglia, which are clusters of neuron cell bodies located outside the CNS. Projects information to and receives information from CNS mediates some reflexes
Large cells w/a bulbous body & slender cytoplasmic extensions or processes. The processes ensheath portions of many different axons, each repeatedly wrapping around part of an axon. This protective covering around the axon is called myelin sheath
Also called schwann cells. They are associated w/PNS axons. Responsible for myelinating PNS axons.
Sensory (afferent) nervous system is responsible for
Receiving sensory info. from receptors & transmitting to CNS. Responsible for input. Contains both PNS & CNS components; nerves of the PNS transmit the sensory info, & certain parts of the brain & spinal cord interpret info. Has two components; Somatic sensory & visceral sensory
Motor (efferent) nervous system is responsible for
Transmitting motor impulses from CNS to muscles or glands. Also for output. Contains both CNS & PNS components; parts of the brain & spinal cord initiate nerve impulses, which travel through motor nerves that in turn transmit impulses to effector organs. Subdivided into somatic motor & autonomic motor components
The components are the general somatic senses-touch, pain, pressure, vibration, temp. & proprioception, & the special senses (taste, vision, hearing, balance, & smell). These functions are considered voluntary because we have some control over them & we tend to be conscious of them
Visceral sensory components transmit...
Nerve impulses from blood vessels & visceral to the CNS. The visceral senses include temp. & stretch (muscles of the organ wall). These functions are involuntary because we don't have control over them & are not conscious of them
Component conducts nerve impulses from the CNS to the skeletal muscles, causing them to contract. Called the voluntary nervous system division because the contractions of the skeletal muscles are under conscious control
This component is called the autonomic nervous system (ANS), because it innervates internal organs & regulates smooth muscle, cardiac muscle, & glands w/out our control. Also known as the visceral motor system or the involuntary nervous system. Has two further subdivisions: parasympathetic & sympathetic
The cell body of a neuron is
Also called a soma, serves as the neurons control center & responsible for receiving, integrating, & sending nerve impulses. It is enclosed by a plasma membrane & contains cytoplasm surrounding a nucleus
Dendrites tend to be
Shorter, smaller processes that branch off the cell body. Some neurons have only one dendrite, while others have many. They conduct nerve impulses toward the cell body; they receive input & then transfer it to the cell body for processing. The more dendrites a neuron has, the more nerve impulses that neuron can receive from other cells
Axon is typically
The longer nerve cell process emanating from the cell body. Sometimes called a nerve fiber. Neurons have either one axon or no axon at all
Synaptic knob is
Also called end bulbs or terminal boutons. Slightly expanded regions at the tips of telodendira
A neuron process that conducts impulses away from the cell body "output"
Unipolar neurons have
A single, short neuron process that emerges from the cell body & branches like a T. Also called pseudo unipolar because they start out as bipolar neurons during development, but their two processes fuse into a single process
Most sensory neurons of the PNS are?
Bipolar neurons are
Neurons that have two neuron processes that extend from the cell body-one axon & one dendrite. Relatively uncommon in humans, primarily limited to some of the special senses
An example of bipolar neurons are?
Located in the olfactory epithelium of the nose & in the retina of the eye
An example of unipolar neurons are?
Most sensory neurons of the PNS
Multipolar neurons are...
The most common type of neuron. Multiple processes, many dendrites & a single axon that extend from the cell body
Example of multipolar neurons are?
Motor neurons that innervate muscle & glands
Sensory neurons are
Or afferent neurons, transmit nerve impulses from sensory receptors to the CNS. They are specialized to detect changes in their environment called stimuli.
Most sensory neurons are
Unipolar, although a few are bipolar
The cell bodies of unipolar sensory neurons are located
Outside the CNS & housed w/in structures called posterior (dorsal) root ganglia
Aggregates of neurofilaments that extend as a complex network into dendrites & axons, their tensile strength provides support for theses processes
Conducts impulses FROM body to CNS
Conducts nerve impulses FROM CNS to muscles or glands
Found only in CNS; facilitates communication between motor & sensory neurons
Structural classification of neurons
Unipolar, Bipolar, Multipolar
Functional classification of neurons
Sensory, motor, interneuron
Most common type of neuron
Function example of multipolar neuron
Interneuron, motor neurons
Function example of bipolar neuron
Some special sense neurons (e.g in olfactory epithelium of nose, retina of eye)
Functional example of unipolar neuron
Most sensory neurons (detect stimuli in the form of touch, pressure, temp., or chemicals
Structural example of sensory neurons
Most sensory neurons are unipolar; a few (e.g some in olfactory epithelium & retina) are bipolar
Structural example of motor neurons
Structural example of interneurons
What is the mnemonic "SAME DAVE"
Sensory-Afferent, Motor-Efferent, Dorsal-Afferent, Ventral-Efferent
The action potential is generated at the
Axon hillock and conducted along the axon to the axon terminals
What are the 3 types of neurons based upon their anatomy?
1) Unipolar neurons
2) Bipolar neurons
3) Multipolar neurons
Chromatophilic bodies are
Free and bound ribosomes, that go by two names, chromatophilic substance, because they stain darkly with basic dyes, or Nissl bodies, because they were first described by the german microscopist Franz nissl. These together with dendrites & cell bodies account for the gray color of the gray matter, as seen in the brain & spinal cord areas containing collections of neuron cell bodies
Defined as a cluster of rough endoplasmic reticulum found in the cell bodies of neuron. Chromatophilic refers to a chromophil cell or cell structure or, a substance readily stained with dyes
A Chromatophilic substance is
Motor neurons are
Efferent neurons, transmit nerve impulses from the CNS to muscles or glands. Called motor neurons because most of them extend to muscle cells to contract.
The muscle & gland cells that receive nerve impulses from motor neurons are called?
Effectors, because their stimulation produces a response or effect
The cell bodies of most motor neurons lie?
In the spinal cord, whereas the axons primarily travel in cranial or spinal nerves to muscles & glands
All motor neurons are?
Interneurons (or association neurons) lie
Entirely w/in the CNS & are multipolar structures. They receive nerve impulses from many other neurons & carry out the integrative function of the nervous system-meaning they retrieve, process, & store info. & decide how the body responds to stimuli. They facilitate communication between sensory and motor neurons
Interneurons outnumber all other neurons in
Both their total number & different types
99% of all neurons are
The number of interneurons activated during processing or storing increases dramatically with?
The complexity of the response
Myelin sheath is
The insulating covering around the axon, consisting of concentric layers of myelin
In the CNS, a myelin sheath forms from?
In the PNS, a myelin sheath forms from?
Myelin mainly consists of
The plasma membranes of these glial cells & contains a large proportion of fasts & a lesser amount of proteins
The high lipid content of the myelin sheath gives the axon
A distinct, glossy, white appearance
Neurofibril nodes are
Gaps or small spaces that interrupt the myelin sheath between adjacent oligodendrocytes or neurolemmocytes. Also called nodes of Ranvier. At these nodes, & only there, can a change in voltage occur across the plasma membrane & result in the movement of a nerve impulse
A nerve is
A cablelike bundle of parallel axons. A nerve tends to be a macroscopic structure. It has 3 successive connective tissue wrappings: endoneurium, perineurium, & epineurium
All of the fascicles are bundled together by this superficial connective tissue covering. Thick layer of dense irregular connective tissue encloses the entire nerve, providing both support & protection to the fascicles w/in the layer
Groups of axons that are wrapped into separate bundles, by a cellular dense irregular connective tissue layer called the perineurium
Cellular dense irregular connective tissue layer. It supports blood vessels supplying the capillaries w/in the endoneurium
A delicate layer of areolar connective tissue that separates & electrically isolates each axon. Also w/in this connective tissue layer are capillaries that supply each axon
A starlike shape due to many projections from their surface. Large cell with numerous cell processes; in contact with neurons & capillaries
Most common type of glial cell
Blood-brain barrier (BBB)
Strictly controls substances entering the nervous tissue in the brain from the bloodstream. Protects the delicate brain from toxins, but allows needed nutrients to pass through. Sometimes detrimental; for example, some medications are not allowed to exit the capillaries & enter the nervous tissue in the bran
Appearance of Ependymal cell is
Simple cuboidal epithelial cell lining cavities in brain & spinal cord; cilia on apical surface
Function of ependymal cells
Lines ventricles of brain & central canal of spinal cord. Assists in production & circulation of CSF
Appearance of microglial cell
Small cell with slender branches from cell body; least common type of glial cell
Function of microglial cells
1) Defends against pathogens
2) Removes debris
3) Phagocytizes wastes
Appearance of satellite cells
Flattened cell clustered around neuronal cell bodies in a ganglion
Function of satellite cells
Protects & regulates nutrients for cell bodies in ganglia
Flattened cell wrapped around a portion of an axon in the PNS. Myelinates & insulates PNS axons. Allows for faster nerve impulse conduction through the axon
Myelinates & insulates CNS axons. Allow faster nerve impulse conduction through the axon. Rounded, bulbous cell with slender cytoplasmic extensions; extensions wrapped around CNS axons
Function of astrocyte
1) Helps form the blood-brain barrie
2) Regulates tissue fluid composition
3) Provides structural support & organization to CNS
4) Replaces damaged neurons
5) Assists with neuronal development
A bundle of anatomical fibers, as of muscle or nerve. Also called fascicle.
What are the structural divisions of the nervous system?
The central nervous system (CNS) and the peripheral nervous system (PNS)