Ther Ex 5 Flashcards
the body’s means of perceiving and responding to events in the internal and external environments. Receptors capable of sensing touch, pain, temperature, and chemical stimuli send information to the CNS concerning changes in our environment. The CNS responds by either voluntary movement or a change in the rate of release of specific hormones from the endocrine system, depending on which response is appropriate.
Nervous system
Nervous system is divided into 2 divisions
Central nervous system and peripheral nervous system
PNS is divided into
Afferent (go towards) and efferent (go away)
Nerve cells are divided into
Cell body, axon, and dendrites
Axons are covered by
Schwann cells
At rest, neurons are negatively charged in the interior with respect to the electrical charge outside the cell. This difference in electrical charge is
Resting potential
When the depolarization reaches threshold, an
action potential or nerve impulse is initiated
Neurons communicate with other neurons at junctions called
Synapses
Neurotransmitters can be
Excitatory or inhibitory
increases neuronal permeability to sodium and results
excitatory transmitter i
cause the neuron to become more negative (hyperpolarized). This hyperpolarization of the membrane
Inhibitory neurotransmitters
position receptors located in joint capsules, ligaments, and muscles.
Proprioceptors
The three most abundant joint and ligament receptors are
nerve endings, Golgitype receptors, and Pacinian corpuscles
The muscle spindle functions as a
Length detector
continuously monitor the tension developed during muscular contraction.
Golgi tendon organs
In essence, Golgi tendon organs serve as safety devices that help prevent
Excessive force during muscle contractions
proprioceptors provide important information to the CNS about
body position and speed of limb movement, which is essential for the successful performance of complex sports skills.
are sensitive to chemical changes around muscle fibers.
Muscle chemoreceptors
When stimulated, muscle chemoreceptors send information back to the CNS about the
metabolic rate of muscular activity, and these messages play a role in the regulation of both the cardiovascular and pulmonary response to exercise
The somatic motor portion of the peripheral nervous system is responsible for
carrying neural messages from the spinal cord to skeletal muscle fibers.
A motor neuron and all the muscle fibers that it innervates are known as
Motor unit
The number of muscle fibers innervated by a single motor neuron is called the
Innervation ratio
the progressive recruitment of motor units, beginning with the smallest motor neurons and progressing to larger and larger motor neurons.
The size principle
Recruiting smaller motor neurons that innervate slow (highly oxidative) muscle fibers first helps to
delay muscle fatigue when high force production is not required to perform the exercise.
The vestibular apparatus is responsible for maintaining
general equilibrium and is located in the inner ear. Specifically, these receptors provide information about linear and angular acceleration.
The brain can be subdivided into three parts:
Cerebrum, cerebellum, and brain stem
The motor cortex controls motor activity with the aid of
input from subcortical areas.
Sports with a high risk of traumatic brain injury (i.e., concussions) include
American football, gymnastics, ice hockey, and boxing
Repeated sportsrelated brain injuries are associated with
h a higher risk of neurodegenerative diseases (e.g., dementia
The disease process responsible for traumatic brain injury–induced dementia is called
chronic traumatic encephalopathy (CTE).
Evidence exists that the spinal cord plays an important role in
voluntary movement, with groups of neurons controlling certain aspects of motor activity.
The spinal mechanism by which a voluntary movement is translated into appropriate muscle action is
Spinal tunning
Reflexes provide the body with a rapid, unconscious means of reacting to a
Painful stimuli
Control of voluntary movement is complex and requires the
cooperation of many areas of the brain as well as several subcortical areas
The first step in performing a voluntary movement occurs in
subcortical and cortical motivational areas, which send signals to the association cortex, which forms a “rough draft” of the planned movement.
The movement plan is then sent to both the
Cerebellum and basal nuclei
Cerebellum responsible for making
FAST movements
Basal nuclei responsible for
slow or deliberate movements
the precise program is sent through the thalamus to the motor cortex, which forwards the message down to spinal neurons for “spinal tuning” and finally to skeletal muscle.
Feedback to the CNS from muscle receptors and proprioceptors allows for the
modification of motor programs
Motor unit aging becomes prominent in most individuals after the age
of 60, and accelerates after 75 to 80 years.
Motor unit aging translates to declines in
reflex response times, peak power, and peak force generation.
Lifelong exercise training is a potent preventative measure for limiting agerelated declines in neuromuscular function
The autonomic nervous system is responsible for maintaining the constancy
the body’s internal environment.
the autonomic nervous system can be divided into two divisions
(1) the sympathetic division and (2) the parasympathetic division.
the sympathetic portion
(releasing norepinephrine) tends to excite an organ
The parasympathetic portion (releasing acetylcholine) tends to
Inhibit same organ
The human body contains more than 600 voluntary skeletal muscles, which constitute 40% to 50% of the total body weight. Skeletal muscle performs three major functions:
(1) force production for locomotion and breathing, (2) force production for postural support, and (3) heat production during cold stress.
Individual muscle fibers are composed of hundreds of threadlike protein filaments called
myofibrils
The region of sarcoplasm surrounding an individual nucleus is termed the
Myonuclear domain
Motor neurons extend outward from the spinal cord and innervate
Individual muscle fibers
Muscle fatigue is defined as a
reduction in muscle power output that results from decreased muscle force generation and/or decreased shortening velocity.
Muscle cramps are
spasmodic and involuntary muscle contractions.
Although the exact cause of muscle cramps remains unsettled, it appears that motor neuron hyperexcitability is likely the general underlying cause of many exerciseinduced muscle cramps suggesting that muscle cramps originate from the
central nervous system.
Successful power athletes (e.g., sprinters) generally possess a large percentage of
Fast muscle fibers and therefore a low percentage of slow, type I fibers.
The amount of force generated during muscular contraction is dependent on the following factors:
(1) types and number of motor units recruited, (2) the initial muscle length, (3) the nature of the motor units’ neural stimulation, and (4) prior contractile activity of the mu
The addition of muscle twitches is termed
Summation
When the frequency of neural stimulation to a motor unit is increased, individual contractions are fused in a sustained contraction called
Tetanus
The peak force generated by muscle decreases as the speed of movement
Increases
release hormones directly into the blood to alter the activity of tissues possessing hormonespecific receptors
Endocrine glands
The free plasma hormone concentration determines the
magnitude of the effect at the tissue level.
The free hormone concentration can be changed by altering the rate of
secretion or inactivation of the hormone, the quantity of transport protein, and the plasma volume.
The hormone—receptor interaction triggers events at the
Cell
Changes in the concentration of the hormone, the number of receptors on or in the cell, and hormone—receptor affinity all influence
magnitude of the effect
Thyroid hormones T3 and T4 are important for maintaining the
metabolic rate and allowing other hormones
The adrenal medulla secretes the
catecholamines epinephrine (E) and norepinephrine (NE)
secreted from the adrenergic neurons of the sympathetic nervous system.
norepinephrine (NE).
The adrenal cortex secretes
s aldosterone (mineralocorticoid), cortisol (glucocorticoid), and estrogens and androgens
regulates Na+ and K+ balance
Aldosterone
increases with strenuous exercise
Aldosterone secretion
is secreted by the β cells of the islets of Langerhans in the pancreas and promotes the storage of glucose
Insulin
The hypothalamus controls the activity of both the
Anterior pituitary and posterior pituitary
GH is released from the anterior pituitary gland and is essential for
Normal growth
GH increases during exercise to
mobilize fatty acids from adipose tissue and to aid in the maintenance of blood glucose
Chronic exercise (training) can decrease
testosterone levels in males and estrogen levels in females. The latter adaptation has potentially negative consequences related to osteoporosis.
The latter mechanism is enhanced during exercise due to the increase
In calcium
act in a permissive manner to support the actions of other hormones during exercise
hormones thyroxine, cortisol, and growth hormone
Growth hormone and cortisol also provide a
“slowacting” effect on carbohydrate and fat metabolism during exercise
Plasma glucose is maintained during exercise by increasing
liver glucose mobilization, using more plasma FFA, increasing gluconeogenesis, and decreasing glucose uptake by tissues. The decrease in plasma insulin and the increase in plasma E, NE, GH, glucagon, and cortisol during exercise control these mechanisms to maintain the glucose concentration
Glucose is taken up 7 to 20 times faster during
exercise than at rest—even with the decrease in plasma insulin. The increases in intracellular Ca++ and other factors are associated with an increase in the number of glucose transporters that increase the membrane transport
Training causes a reduction in circulating levels of
E, NE, glucagon, and insulin responses to exercise.
The plasma FFA concentration decreases during
heavy exercise even though the adipose cell is stimulated by a variety of hormones to increase
triglyceride breakdown to FFA and glycerol
A healthy immune system requires the teamwork of two layers of immune protection:
(1) innate immune system and (2) acquired immune system.
protects against foreign invaders and is composed of three major components: (1) physical barriers such as the skin and the mucous membranes that line our respiratory, digestive, and genitourinary tracts; (2) specialized cells (e.g., phagocytes and natural killer cells) designed to destroy invaders; and (3) a group of proteins called the complement system, which are located throughout the body to protect against invaders.
Innate
adapts to protect against almost any type of invading pathogen. The primary purpose of the acquired immune system is to provide protection against viruses that the innate immune system cannot combat directly. B and Tcells are the major cells involved in the acquired immune system. Bcells produce antibodies, whereas Tcells specialize in recognizing and removing antigens in the body.
Acquired immune system
The relationship between the intensity/amount of exercise and the risk of developing a URTI is described as a
J shaped curve
This Jshaped curve illustrates that moderateintensity aerobic exercise decreases
Risk of infection
heavyintensity/prolonged exercise increases the risk of
infection
Following heavyintensity exercise, lower cell counts and activity of natural killer cells, Tcells, and Bcells appear to be directly related to the increased risk of
infection following heavyintensity/longduration bouts of exercise.
Heavyintensity/longduration exercise has a temporary depressive effect on the
Immune system
exercise in a hot environment does not pose a greater threat to immune function compared to exercise in a
Cool environment
Prolonged highaltitude exposure (i.e., living in the mountains) combined with exercise can
increase the risk of URTI.
It is not wise to exercise if cold symptoms are below the
Neck
