Exam 2 Part three Flashcards
Type of muscle fiber that fatigues easily
Fast fiber
Muscle fiber plasma membrane
Sarcolemma
Muscle whose function opposes agonist
Antagonist
Connective tissue covering a fascicle (skeletal muscle fascicle)
Perimysium
Functional contractile unit of a skeletal muscle fiber
Sarcomere
Protein in thick filaments
Myosin
Sarcomere region with thin filaments only
I band
Muscle that surrounds an opening
Circular muscle
The resting tension within a muscle
Muscle tone
The more mobile attachment of a muscle
Insertion
The unit of muscle structure that is composed of bundles of myofibrils, enclosed within a sarcolemma, & surrounded by a connective tissue covering called endomysium is a?
Muscle fiber
During the contraction of a muscle fiber, myofibrils…
Shorten
In a convergent muscle, the fibers are?
Widespread over a broad area & joined at a common attachment site
The plasma membrane of a skeletal muscle fiber is called the
Sarcolemma
In a skeletal muscle fiber a triad is composed of?
One transverse tubule & two terminal cisternae
During development, the ____ of a somite gives rise to the skeletal muscle
Myotome
What is a synapitc knob?
Expanded tip of an axon at the neuromuscular junction
The bundle of dense regular connective tissue that attaches a skeletal muscle to bone is called a(n)
Tendon
The muscle that assists the agonist is called the?
Synergist
Compare the roles of the three concentric layers of connective tissue wrappings in the organization of skeletal muscle
The 3 layers provide protection, sites for distribution of blood vessels & nerves, & a means of attachment to the skeleton
The endomysium electrically insulates each…
Muscle fiber. It has reticular fibers to help bind together neighboring muscle fibers & support capillaries
The perimysium contains extensive
Arrays of blood vessels & nerves that branch to supply each individual fascicle
The epimysium surrounds
The whole skeletal muscle
Describe the structure of tendons & their purpose in the body
Tendon structure: Thick, cordlike structure
Tendons purpose: Attaches the muscle to bone, skin or another muscle
Describe the structure of aponeuroses & their purpose in the body
Aponeuroses structure: Thin, flattened sheet
Purpose: Replaces a tendon in muscles that are flat and sheetlike & have a wide area of attachment
Ca++ bonds to troponin causing shift in
Tropomyosin
What is the structural & functional unit of the nervous system?
Neuron
Which two muscle tissues have striations?
Cardiac & skeletal
Skeletal muscle is derived from what tertiary development structure?
Myotome (somite is secondary structure)
What is rigor mortise?
Myosin heads don’t let go of actin active site because of lack of ATP after death
How are muscle fibers & neurons similar?
- Both membranes can conduct action potentials
- Both show all-or-none response
- Both must reach a threshold level to trigger an action potential
- One neuron & all the muscle cells it contacts
- allows for fine & gross muscle control
Motor unit
Less cells per motor unit=
Fine control
Most fibers are
Fast or white
Slow fibers can sustain
Contraction; have myoglobin & extensive blood supply (aerobic); red in color=red fibers
Moderate endurance, red in color, aerobic, numbers depend upon exercise, fast fibers become intermediate fibers when used heavily
Intermediate fibers
Atrophy is
Loss of muscle mass, lack of use, loss of proteins, may result in cell loss, never regain those cells
Hypertrophy is
Exercise, increase in mass, not increase in fiber (cells), more myofibrils, more mitochondria, more blood supply, more glycogen
What is a motor unit?
One neuron & all the muscle fibers it stimulates
Why might atrophy be permanent?
Loss of cells, connective tissue buildup
- Fibers bundled at tracts
- Cell bodies in nucleus
- Myelin by oligodendrocytes
Central nervous system
Cell body off the side; sensory neurosn
Unipolar
A single dendrite & a single axon arising from opposite poles of the cell body
Bipolar
A nerve impulse is also called a
Action potential
Resting potential is
-70mv (millivolts)
Speed is affected by size of?
Fiber
Speed is affected by insulation of
Axons
Describe the difference between a nerve and a neuron
- Neuron refers to a single cell that has the ability to become “excited” & pass a nerve impulse along to a muscle, gland or another neuron
- Nerve refers to a structure made up of the fibers of many neurons. These fibers are bundled up in connective tissue. The fibers may be carrying impulses only toward the CNS, in which case it will be a sensory nerve.
Together the CNS & PNS perform 3 general functions
1) Collecting information
2) Processing & evaluating information
3) Responding to information
Responsible for input
Sensory nervous system
What are the functional divisions of the nervous system?
Sensory and motor nervous system
The sensory and motor nervous system breaks down further to
Sensory nervous system: Somatic sensory & Visceral sensory
Motor nervous system: Somatic motor & Autonomic motor
1) Contains receptors
2) Transmits information from receptors to the CNS
Sensory nervous system
1) Transmits information from CNS to the rest of the body
2) Sends motor information to effectors
Motor nervous system
The somatic sensory of the functional nervous system does what?
Receives sensory information from skin, fascia, joints, skeletal muscles, & special senses
The visceral sensory of the functional nervous system does what?
Receives sensory information from viscera
The somatic motor of the functional nervous system does what?
“Voluntary” nervous system: innervates skeletal muscle
The autonomic motor of the functional nervous system does what?
“Involuntary” nervous system: innervates cardiac muscle, smooth muscle, & glands
Define ganglion
gangli = a swelling) A group of neuron cell bodies.
What are the special senses?
Taste, vision, hearing, balance, & smell
Responsible for output?
Motor nervous system
The autonomic nervous system has two further subdivisions
Parasympathetic and sympathetic
What are the two distinct cell types that form the nervous tissue?
Neurons: Excitable cells that are able to generate, transmit, & receive nerve impulses
Glial cells: Nonexcitable cells that support & protect the neurons
This is sometimes called a nerve fiber
Axon
Axon terminals are
Also called telodendria which are an array of fine terminal extensions. The extreme tips of these have slightly expanded regions called synaptic knobs
The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells
Axon terminals
Myelin sheath
(myel = marrow) The fatty insulating substance around many axons.
Afferent neuron are
Also sensory neurons, that transmit nerve impulses FROM sensory receptors TO the CNS
Efferent neurons are
Also called Motor neurons, that transmit nerve impulses FROM the CNS TO muscles or glands
Describe the relationship and order of the sensory neurons, interneurons, & motor neurons
1) Sensory neurons carry afferent (input) signals to the central nervous system
2) Interneurons process info. in the CNS
3) Motor neurons transmit efferent (output) impulses from the CNS to effectors
How do neuroglia differ from neurons?
1) They are smaller and capable of mitosis
2) Glial cells do not transmit nerve impulses
3) Glial cells assist neurons with their functions
CSF is
Cerebrospinal fluid, a clear liquid that bathes the CNS & fills its internal cavities. Produced by the choroid plexus which is the ependymal cells & nearby blood capillaries that form a network.
The smallest percentage of CNS glial cells
Microglial
A collection of neuron cell bodies located outside the CNS
Ganglion
What is the main activity of axons?
Nerve impulse conduction
Action potential is
Also known as nerve impulse, a rapid movement of an electrical charge along a neuron’s plasma membrane.
Why is nerve impulse also known as action potential?
Because a nerve impulse is caused by an actual voltage (potential) change that moves along the plasma membrane of the axon
The nerve impulse’s ability to travel along an axon is affected by
A process called myelination
Define myelination
The process by which part of an axon is wrapped with a myelin sheath.
Neurilemma is
Sometimes used to describe the delicate, thin outer membrane of the neurolemmocyte when it myelinates
What are the two different myelinating glia cells
In the CNS, a myelin sheath forms from oligodendrocytes and in the PNS it forms from neurolemmocytes
What gives the axon a distinct, glossy white appearance?
The high lipid content of the myelin sheath
In the CNS, an oligodendrocyte can myelinate a portion of
Many axons
In the PNS, a neurolemmocyte can myelinate a portion of
A single axon only
Neurofibril nodes are
The small spaces that interrupt the myelin sheath between adjacent oligodendrocytes or neurolemmocytes. Also called nodes of Ranvier.
What happens at the neurofibril nodes?
At these nodes and only at these nodes can a change in voltage occur across the plasma membrane & result in the movement of a nerve impulse
Saltatory conduction is
The process in a myelinated axon, the nerve impulse jumps from neurofibril node to neurofibril node
Large diameter, myelinated axons conduct nerve impulses rapidly to the skeletal muscles in the limbs using
Saltatory conduction
Nerves are a component of the?
PNS
Sensory neurons convey sensory information to the
Central nervous system
Motor neurons convey motor impulses from the
Central nervous system to the muscles & glands
Mixed nerves convey
Both types (CNS & PNS) of information
Synapses are
Specialized junctions where axons terminate as they contact other neurons, muscle cells, or glands
where the nerve impulse is transmitted to the other cell
Synaptic knobs are
Swellings that are formed by the synaptic endings.
What do the synaptic knobs contain?
The synaptic knob is filled with membrane-enclosed vesicles containing a neurotransmitter
Synaptic cleft is
A very narrow space where the plasma membranes of the presynaptic neuron & postsynaptic neuron are separated. Separates the synaptic knob & motor end plate
Presynaptic neuron is
A neuron from the axon terminal of which an electrical impulse is transmitted across a synaptic cleft to the cell body or one or more dendrites of a postsynaptic neuron by the release of a chemical neurotransmitter
Post-synaptic neuron is
A neuron to the cell body or dendrite of which an electrical impulse is transmitted across a synaptic cleft by the release of a chemical neurotransmitter from the axon terminal of a presynaptic neuron
A neurotransmitter is
A signaling molecule. Most common is acetycholine (ACh)
The neurotransmitter is only released from the
Presynaptic cell
After the neurotransmitter is released what happens?
They then bind to receptor proteins found only in the plasma membrane of the postsynaptic cell, and this causes a brief voltage change across the membrane of the postsynaptic cell
Acetylcholine (ACh) is
The most common type of neurotransmitter. They cause a brief voltage change across the membrane of the postsynaptic cell
Synaptic vesicles are
Small secretory vesicles that contain a neurotransmitter, found inside an axon near the presynaptic membrane, and releases its contents into the synaptic cleft after fusing with the membrane
Neuromuscular junction
The point where a motor neuron meets a skeletal muscle fiber
Norepinephrine is
A neurotransmitter, norepinephrine relays brain impulses from one cell to the next and is involved in arousal, attention and mood.
Axon ending is
The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells. Also called end-feet, neuropodia, terminal boutons
Describe a chemical synapse
1) A nerve impulse travels through the axon & reaches its synaptic knob
2) The arrival of the nerve impulse at the synaptic knob causes an increase in calcium ion (Ca2+) movement into the synaptic knob through voltage-regulated calcium ion channels in the membrane
3) Entering calcium ions cause synaptic vesicles to move to & bind to the inside surface of the membrane; neurotransmitter molecules w/in the synaptic vesicles are released into the synaptic cleft by exocytosis
4) Neurotransmitter molecules diffuse across the synaptic cleft to the plasma membrane of the postsynaptic cell
5) Neurotransmitter molecules attach to specific protein receptors in the plasma membrane of the postsynaptic cell, causing ion gates to open
6) An influx of sodium ions (Na+) moves into the post synaptic cell through the open gate, affecting the charge across the membrane
7) Change in the postsynaptic cell voltage causes a nerve impulse to begin in the postsynaptic cell
8) The enzyme acetylcholinesterase (AChE) resides in the synaptic cleft & rapidly breaks down molecules of ACh that are released into the synaptic cleft. Thus AChE is need so that ACh will not continually stimulate the postsynaptic cell
True or false: Acetylcholine is actively transported from the pre-synaptic membrane to the post - synaptic membrane
False
True or false: If the post-synaptic membrane potential reaches threshold level, an action potential will be produced
True
What factors effect the speed of an impulse?
The axon’s diameter & the presence (or absence) of a myelin sheath. The larger the diameter of the axon, the more rapidly the impulse in conducted because of less resistance to current flow as charged ions move into the axon. An axon with a myelin sheath conducts impulses many times faster than an unmyelinated axon because of the difference between saltatory & continuous conduction
Why do we have synapses?
1) They make sure that the flow of impulses is in one direction only. Because the vesicles containing the transmitter are only in the presynaptic membrane and the receptor molecules are only on the postsynaptic membrane
2) They allow integration
3) They allow ‘summation’ to occur
4) They allow the ‘filtering out’ of continual unnecessary or unimportant background stimuli
5) For communication
