Chapter 5 Nervous System Exercise Phys.
axon hillock
the part of a neuron where the summation for incoming information is processed, if threshold is reached an impulse is transmitted down the axon
multiple motor unit summation
the relationship between increased stimulus strength and an increased number of contracting motor units
Peripheral Nervous System (PNS)
the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body (muscles, glands, organs) made up of neurons and ganglia. -subdivided into the autonomic nervous (parasympathetic and sympathetic) system and somatic nervous system
nervous impulse (action potential)
the stimulus in the form of electrical energy that travels down an axon due to the movement of electrically charged ions moving in and out of the axon causing muscle fibers to contract
excitory neurotransmitters
type of neurotransmitters that make membrane potential less negative by increasing membrane permeability to Na+ (causing excitation of the post synaptic membrane)
True
True or false, Greater excitability and nerve conduction velocity in high-threshold motor units of power trained athletes increases force produce and the rate air which the peak force is generated (reaches peak force quicker)
true
True or false, a physiological advantage of the size principle order of recruitment is that It ensures that low threshold or easily recruited motor units composed of type 1 fibers for aerobic metabolism are fatigue resistant. Higher threshold motor units are only recruited when there is a need of higher force but fatigue quickly due to relying an anaerobic metabolism.
Nodes of Ranvier
allow the action potential to jump from node to node due to the presence fo Na+ and K+ channels on the membrane. (question mark in picture) This is apart of saltatory conduction
Maximum force production of a muscle could be increased through several neural adaptations. Increased synchronization of motor units increases the number of motor units active at a point in time, thus increasing maximal force. After training, increases in the excitability of high-threshold motor units make it easier to recruit these motor units. Training also improves conduction velocity of motor axons, which improves the rate coding of motor units. These factors would increase the rate of force development of motor units and of muscle. During an activity involving several muscles, training brings about the ability to rotate recruitment of the involved muscles. This allows muscles that are not being maximally recruited to recover while other muscles generate the force needed to perform the activity. Rotating muscle recruitment during an activity maintains force production for longer periods of time because muscles recover when they are not maximally recruited and so are available to generate force while a different muscle is not maximally recruited and recovers. Thus, rotating muscle recruitment allows a high amount of force production and minimizes the effects of fatigue during the activity.
Discuss neural adaptations that could increase physical performance.
Neuroglia cells
All in the CNS: astrocytes, oligodendrocytes, microglia, ependymal cells. Provide support and nourishment too neurons, form myelin sheaths
dendrites, cell body (soma), axons
What 3 components makes up the most known cell type in the nervous system: the Neuron?
sympathetic nervous system
-fight or flight -the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations
saltatory conduction
-increase velocity of neural conduction -and conserves energy
autonomic nervous system
-part of nervous system that controls physiological functions that are unconscious -Ex: heart rate, breathing, digestion, etc. -broken down into the sympathetic nervous system and parasympathetic nervous system -could be small amount of conscious control
myelin sheath
A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node of Ranvier to the next.
Ligands
A molecule that binds specifically to a receptor site of another molecule.
axon
A threadlike extension of a neuron that carries nerve impulses away from the cell body to another neuron or target tissue (such as muscle)
Na+/K+ pump
Active transporter that moves three Na+ out of a cell and two K+ into the cell against their respective concentration gradients. Restores the separation of charge across the neurons membrane.
No, not all muscle fibers are recruited when a light weight is lifted. According to the size principle, when a light weight is lifted, the force demands are not high enough to recruit the larger motor units.
Are all the muscle fibers recruited when a light weight is lifted? Explain why or why not.
Dendrites
Branchlike parts of a neuron that are specialized to receive information and then send It to the cell body (soma)
Interneurons
Central nervous system neurons that internally communicate and intervene between the sensory inputs (neurons) and motor outputs (neurons) -account for 99% of all neurons and only in CNS
The resting membrane potential is caused by the separation of charged ions across the membrane. Na+ ions predominately are found outside the cell membrane, whereas K+ ions predominately are found inside the cell membrane. Although both of these ions have a positive charge, there are more Na+ ions than K+ ions, resulting in a net negative charge (−65 to 70 mv) on the interior of the membrane. During depolarization, Na+ channels in the membrane open and Na+ ions pass through the membrane to the interior of the cell because of their electrochemical gradient. This results in a net positive charge (+30 mv) on the interior of the membrane relative to the exterior. For repolarization to occur, the Na+ channels close and K+ channels open, allowing K+ ions to leave the interior of the cell because of their electrochemical gradient. This begins to return the membrane to its resting membrane potential. However, the K+ channels remain open slightly longer than necessary to achieve resting membrane potential, and the membrane becomes slightly hyperpolarized. After this brief period of hyperpolarization, the membrane returns to resting membrane potential. An action potential consists of both depolarization and repolarization of the membrane.
Describe what causes resting membrane potential in an axon or neuron, and then discuss how the movement of ions causes an action potential.
The action potential refers to both depolarization and repolarization. Depolarization occurs first in the action potential because of the movement of Na+ into the neuron. The depolarization is followed by repolarization, which is achieved by the movement of K+ out of the neuron.
Explain the different stages of the action potential, that is, depolarization and repolarization, and the movement of ions that occurs in each.
They increase the velocity at which the impulse is passed through the CNS
How are myelin sheaths important in sports?
-increased body temperature -changes in acid-base balance -hypo-hydration -changes in blood pressure -altered blood glucose
How does exercise effect homeostasis?
Repolarization
K+ channels open, allowing positively charge K+ to leave the interior of the axon that, in conjunction with closing of Na+ channels, results in the membrane potential becoming negative again during a process termed ______________________
excitory and inhibitory
List the two broad categories of neurotransmitters.
type I; lower
Motor units made up of _______________ fibers are typically recruited first due to the ______________ recruitment thresholds of their neurons.
motor cortex
Movement force and velocity are ultimately determined by the __________ ________, which uses sensory feedback to complete the desired movement
Positive feedback loops intensify or promote a process. During exercise, for example, increased acidity produced by active muscle will cause an increase in blood flow to the affected tissue. As the activity level of muscle increases, resulting in even higher acidity, a greater increase in blood flow will occur.
Provide and explain an example of a positive feedback loop during exercise.
saltatory conduction
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
True
T/F All muscle fibers of a single motor unit are of the same type (i.e. I, IIA, or IIX).
True
T/F An increase in maximal neural drive to a muscle increases force.
.False
T/F During an action potential, repolarization occurs prior to depolarization
True
T/F Slow motor units are made up of type I muscle fibers.
True
T/F The fight-or-flight response is brought about by the stimulation of the sympathetic branch of the autonomic nervous system.
sympathetic; parasympathetic
The ______________ nerves stimulate the heart rate to speed up while the ______________ nerves stimulate it to slow down.
tetanus
The complete summation of nerve impulse twitches is called _____________, which results in the maximal force a motor unit can develop.
Hyperpolarization
The movement of the membrane potential of a cell away from rest potential in a more negative direction
resting membrane potential
The neuron having a negative charge on the inside of the cell and a positive charge on the outside by the arrangements of positive and negative ions and its membrane being impermeable during resting conditions. - charge is about -70mV
Depolarization
The process during the action potential when sodium (NA+) is rushing into the cell via Voltage gated sodium channels causing the interior to become less negative. Up to +30mV. After a brief delay, voltage gated K+ channels open to let out K+ out of the cell to repolarize It (make It more negative again).
rate coding
The rapidity at which action potentials are fired down the motor axon helps control the force produced by a motor unit. This process is called _____________.
true
True or false, at the neuromuscular junction, It has shown that endurance training has given an increase in the number of both acetylcholine presynaptic vesicles and postsynaptic receptors by about 30% resulting in delayed fatigue and improved endurance performance.
False, It causes an increase in the size of the NMJ which improves performance.
True or false, endurance training and resistance training have shown to shrink the size of the neuromuscular junction by about 15%.
true
True or false, exercise can help increase more efficient recruitment pattern of motor units and possibly improve activation at sub-maximal efforts.
True
True or false, most of the time, receptors of ion channels TYPICALLY only allow a single ion type to cross (ex: Na+, K+, or Ca 2+)
True
True or false, muscles where fine control of force is needed, there are fewer muscle fibers per motor unit.
False, muscles where less control of force is needed has more muscle fibers per motor unit.
True or false, muscles where less control of force is needed has fewer muscle fibers per motor unit.
True
True or false, smaller motor units are composed of fewer muscle fibers and generally have smaller axon innervating them that fast motor units.
True
True or false, the autonomic N.S is divided into the sympathetic N.S and parasympathetic N.S
true
True or false, the importance of the Na+/K+ pumps is obvious when considering the that half of all standard energy consumption is used to synthesize and maintain these related channels.
true
True or false, the primary role of the parasympathetic system is to help the body rest and digest
true
True or false, there are more Na+ ions outside of the neuron membrane than there are K+ ions inside of the neuron membrane.
False, there are more negative feedback systems (loops)
True or false, there are more positive feedback systems in the body than negative feedback systems
True
True or false, with resistance training comes an increase in maximal neural drive (neural activity in the muscles) which increases muscular strength without hypertrophy.
True
True or false, within the first weeks of training, strength increase mostly comes from neural adaptations to exercise.
-decrease in heart rate and blood pressure -pupil constriction -contracts bronchials -increase blood flow to the skin -peristalsis of gastrointestinal tract -check photo
What are some of the body responses when the parasympathetic N.S is activated?
-increase in heart rate and blood pressure -more blood flow to skeletal muscles -release of glucose by liver/break down of glycogen in the muscles -pupil dialtion -decrease in saliva produced -bronchials relaxed -increase release of norepinephrine and epinephrine from adrenal medulla -others in photo
What are some of the body responses when the sympathetic N.S is activated?
-increase velocity of neural conduction -and conserves energy
What are the advantages of saltatory conduction?
Brian and spinal cord
What are the two components of the CNS
Improvements in muscular strength without significant muscular hypertrophy are caused by improvements in motor synchronization or activation, rate coding of motor units, and less activation of antagonistic muscles. Together these are sometimes referred to as "neural adaptations."
What contributes to training-induced changes in muscle strength with no significant hypertrophy of the muscle?
-Time delay caused by recruiting smaller motor unite may be detrimental to performance of a high force activity -in such cases, high-threshold, fast motor units are recruited first to allow faster movement velocity Ex: like a power clean
What is an exception to the size principle of recruitment?
During low-intensity exercise, few motor units are required to produce the needed force for movement in the exercise. This means that other motor units needed to produce force in high-intensity exercise are essentially resting and recovering. Such low-intensity exercise is many times used as a recovery workout to allow for repair and remodeling of the higher-threshold fast motor units that were used the day or two before. However, because that force but must be maintained for long periods of time, slow motor units that have high aerobic capacity are recruited first and primarily. Only when high levels of force are required are fast motor units recruited, but they fatigue quickly because of poor aerobic capacity. So, primarily recruiting the slow motor units during low-intensity activity helps prevent fatigue.
What is the advantage of the size principle of motor unit recruitment during an activity like jogging slowly?
Type 1, Type IIa, Type IIx -becasue It goes type 1 is the smallest axons and somas to type IIX being the biggest axons and somas. It is easier to recruit the smaller fibers due to having a lower recruitment threshold.
What is the oder in the type of muscle fibers recruited first and why is It done in the order in most cases?
opens channels allowing ion flux or movement across the neurons membrane resulting in electrical charge.
What is the primary function of a receptor?
fast-fatigable motor units
What kind of motor unit is being described? -large motor axons -quickly send electrical impulses to muscle fiber (fast twitch) -type IIX -Highest amount of force between three, but last short period of time
fast-fatigue resistant motor units
What kind of motor unit is being described? -larger axons and propagate electoral stimulations two to the muscle fibers more rapidly -muscle fibers innervated are Type IIA:capable of developing considerable force, larger than type 1, moderately fatiguable
Slow (S) motor units
What kind of motor unit is being described? -type one fibers that develop little force and are small in size -resistant to fatigue (high aerobic capacity)
-Skull and cerebral spinal fluid for the brain -Vertebrae and cerebral spinal fluid for the spinal cord
What protects the Brian and spinal cord?
all; none
When a threshold level of activation is reached in a motor unit, ______________ of the muscle fibers in the motor unit will be activated; if the threshold level is not achieved, ________________ of the muscle fibers in the motor unit will be activated.
parasympathetic nervous system
Which division of the autonomic N.S plays a significant role in recovery from exercise by returning the body to homeostasis? -essential for optimal health and fitness especially with aging
e. a, b, and c
Which of the following IS true of fast-fatigable motor units? a. They have large motor axons b. They feature type IIX muscle fibers c. Of the three types of motor units they develop the most force d. They feature type I muscle fibers e. a, b, and c f. d and b
d. It occurs only in unmyelinated nerves
Which of the following is not true of saltatory conduction? a. It allows the action potential to "jump" from one node of Ranvier to the next. b. It increases the velocity of nerve transmission c. It conserves energy d. It occurs only in unmyelinated nerves e. It uses the movement of different ions
e. All of the above
Which of the following is true concerning a neuron? A. Dendrites carry impulses toward the cell body B. Axons carry impulses away from the cell body C. The axon hillock is between the axon and the cell body D. One neuron controls all the muscle fibers in a motor unit E. All of the above
C. The number of muscle fibers in a motor unit depends on the amount of fine control required for its function
Which of the following is true of a motor unit? A. Smaller and larger motor units are able to produce the same amount of maximal force. B. On average, for all of the muscles in the body, about 100 neurons control a muscle fiber C. The number of muscle fibers in a motor unit depends on the amount of fine control required for its function D. Motor unit that stretch the lens of the eye contain 1,000 muscle fibers E. A. motor unit onsite of a beta motor neuron and its associated skeletal muscle fibers
e. a and b
Which of the following is, or are, exceptions to the size principle of recruitment? a. Recruit high-threshold type II motor units first b. Not recruiting low-threshold motor units first c. recruiting slow prior to fast motor units d. None of the above e. a and b
myelin sheath
White covering high in lipid (fat) content that surrounds the axons, provides insulation, and maintains electrical signal strength of the action potential as It travels down the axon
positive feedback loop
a feedback loop in which change in a system is promoted or intensified (increased blood flow to working muscles that are building up acid)
alpha motor neurons
a neuron that controls skeletal muscle activity; It is composed of relatively short dendrites that receive the information, cell body, and long axons that carry impulses from the cell body to the neuromuscular junction., which interfaces with the muscle fiber
Acetylcholine (ACh)
a neurotransmitter released at motor synapses and neuromuscular junctions, active in the transmission of nerve impulses
chemical synapse
a type of synapse at which a chemical (a neurotransmitter) is released from the presynaptic axon of a neuron into the synaptic cleft, where it binds to receptors on the postsynaptic neuron or specialized region of a muscle cell or secretory cell
Homeostasis
ability of an organism to maintain internal equilibrium by adjusting its physiological processes to keep function within physiological limits at rest or during exercise
motor unit
an alpha motor neuron and all the muscle fibers it innervates
sensory neurons (afferent neurons)
carry messages from sensory receptors in the body's periphery to the central nervous system (long dendrites and short axons)
Tetanus
complete summation of twitches and maximal force a motor unit can develop
Motor cortex (frontal lobe)
conscious, controlled movements that characterize exercise and sports activities are initiated in the________________________
motor neurons (efferent neurons)
have their cell body in the spinal cord so they have a long axon that innervates muscle fibers and short dendrites to receive impulses from other neurons.
asynchronous recruitment
helps avoid fatigue during sustained muscle contractions, refers to different motor units taking turns maintaining muscle tension, and makes an entire muscle seem to contract smoothly.
cell body (soma)
is the processing center for signal information received. That signal is then sent to the axon
size principle of recruitment
motor units fire in order from small to large (size of neuron found at that motor unit) and are derecruited in opposite order
inhibitory neurotransmitters
neurotransmitters that make membrane more permeable to K+ or Cl-, making It more negative inhibiting the formation of an AP.
sensory-somatic nervous system
part of the peripheral nervous system that consists of 12 pairs of cranial nerves, 31 pairs of spinal nerves, and associated ganglia; controls voluntary actions of the body, like walking & talking.
Synapse
point of connection and communication between two excitable cells
electrical synapses (gap junctions)
rare, found in the heart, smooth muscle, and GI tract: communicate by allowing ions or electrically charged particles to directly pass between them through specialized areas of the membrane of cells called gap junctions.
negative feedback loop
reduce the intensity of an ongoing process in an attempt to return to the initial status (sweating until temperature brought back to normal)
rate coding
the ability of neurons to vary the rate at which action potentials are generated
action potential
the change in electrical potential associated changes in Na+ and K+ across the membrane (depolarization and replarization) causing the passage of an impulse along the membrane of a muscle cell or nerve cell.
parasympathetic nervous system
the division of the autonomic nervous system that calms the body, conserving its energy, or keeping the body at a resting homeostatic state or function
reciprocal innervation
when one muscle is signaled to contract, its antagonist is signaled to relax to prevent countering muscle forces
all or none law
when threshold is reached, all muscle fibers in motor unit are activated, if not reached, none of the muscle fibers are activated
