kinesiology part 2

central nervous system location

brain and spinal cord

peripheral nervous system

neurons outside the CNS, sensory division and motor division

general nervous system functions

receiving input and transmitting signals to an integrating center (sensory)

control of the internal environment by sending signals to effector organs (automatic)

voluntary control of movement (somatic)

assimilation of experiences (CNS)

cell body

main cellular structures with nucleus and organelles

dendrites

conduct nerve impulses toward the cell body

axon

conducts impulses away from the cell body, may be covered by adipose-like Schwann cells

synapse

gap between the axon of one neuron (pre-synaptic neuron) and dendrite of another (post-synaptic neuron)

all or none law

if a nerve is stimulated and reaches its threshold it will cause a nerve impulse/action potential, the strength of the impulse is the same no matter what the magnitude of the stimulation

reaching threshold: neurotransmitters

neurons communicate across small gaps, or synapses, using chemical neurotransmitters

general types or responses or neurotransmitters

excitatory or stimulatory: help post-synaptic cell to reach its threshold

inhibitory: hinders post-synaptic cell reaching its threshold

reaching a neuron's threshold is determined by the summation of all output

proprioceptors

provide CNS with information about body position and movement

vestibular receptors

a type of proprioceptor, found in the nonauditory portion of the inner ear, provides CNS with head/body position info

kinesthetic receptors (mechanoreceptors)

a type of proprioceptor, muscle spindles, Golgi tendon organs, free nerve endings. provide the CNS with information on movement

chemoreceptor

provide CNS with information regarding the metabolic rate and muscular activity

baroreceptors

provide CNS with information regarding pressure, such as blood pressure

muscle spindles: a mechanoreceptor

special muscle fibers and sensory neurons located in a connective sheath within the muscle. detects changes in muscle length, rate of length change, and accounts for stretch (myotonic) reflex

nervous system reflexes

rapid, unconscious means of reacting to stimuli

stretch or myotonic reflex

two neuron reflex, one sensory (afferent) and one motor (efferent) neuron, protective reflex

Golgi tendon organ (GTO): a mechanoreceptor

sensory neurons located in the muscle tendon (extension of muscle's connective tissues), monitors tension developed in the whole muscle, excessive force generation results in some muscle fibers

somatic motor function: motor neurons of PNS

carry neural messages from spinal cord to skeletal muscles

somatic motor function: motor unit

a single motor neuron and all the muscle fibers it innervates

somatic motor function: innervation ratio

number of muscle fibers per motor neuron: 1:10s in the eyeball where fine control is required, 1:1000s in the larger muscles that control gross movements

motor cortex

part of the cerebral cortex, most concerned with voluntary movement, forwards message down spinal column to muscles

cerebellum

coordinates sensory information on complex movements, balance, and body position, considered to modify muscular activity

autonomic nervous system

assists in maintaining the internal environment, organs and tissues not under voluntary control, collaborates with the endocrine system

autonomic NS controls several types of tissues

smooth muscle, cardiac muscle, and glands

how many neurons to get to the tissues?

two, a pre and a post-synaptic neuron

autonomic nervous system: sympathetic division

usually excites an effector organ, thoracic and lumbar regions of the spinal cord, pre-synaptic neurons release acetylcholine, post-synaptic neurons release norepinephrine

autonomic nervous system: parasympathetic division

usually inhibits an effector organ, cranial and sacral spinal cord, pre- and post-synaptic neurons releases acetylcholine

skeletal muscle tissues

striated muscle, voluntary control, can be controlled by autonomic nervous system

cardiac muscle tissues

striated muscle, involuntary

smooth muscle tissues

non-striated muscle, involuntary (GI tract, arteries, veins)

structure of skeletal muscle

long, cylindrical cell/fibers, cross-striations of alternating light and dark bands, up to several hundred nuclei in each cell/fiber, structural independence from each neighboring fiber (fibers contract without the fiber next to it contracting)

nervous system control of skeletal muscles

somatic motor neurons from the CNS, The Neuromuscular Junction

the neuromuscular junction

site where Moto neuron meets the muscle fiber, separated by gap called the neuromuscular cleft

acetylcholine is released from the motor neuron, stimulates the muscle fiber by causing an action potential that moves across that fiber

neural stimulation: muscle twitch

contraction as the result of a single stimulus

neural stimulation: summation

repeated, frequent impulses that lead to an increase in tension

neural stimulation: tetanus

a high frequency of stimulation that leads to a sustained contraction

structures of skeletal muscle: myo- or sarc-

muscle

myocyte

muscle cell, muscle fiber

sarcolemma

muscle cell membrane

sarcoplasm

muscle cell cytoplasm

connective tissues

very strong supporting tissues.

ligaments connect bone to bone to provide skeletal support, tendons connect muscle to bone to transfer the force production from muscle cells to bone

myofilaments

structural proteins in muscle fibers that cause shortening

actin

(thin filament) double helix, has a binding site for calcium

myosin

(thick filament) has arm-like cross-bridges that form strong bonds with actin when calcium binds to actin

sarcomere

functional subunit within a myocyte, z-line to z-line: membrane that separates sarcomeres and is attached to the actin filaments

force regulation in muscle

nature of the motor units neural stimulation, increased frequency of stimulation will sum to reach the threshold of more and faster fibers

more motor units

greater force

faster/larger motor units

greater force

fiber types and performance

Nonathletes

-Have approximately 50% slow and 50% fast fibers

Power athletes

-Sprinters

-Higher percentage of fast fibers

Endurance athletes

-Distance runners

-Higher percentage of slow fibers

Fiber type is not the only variable that determines success in an athletic event

endurance training

greatest adaptation in SO fibers, can result in shift in characteristics of FOG and FG fibers toward more oxidative capacity

resistance training

greatest adaptation in FG and FOG fibers, can result in shift in characteristics of SO and FOG fibers

heart

pumps blood and creates pressure in the vascular system

arteries and arterioles

vessels that carry blood away from the heart

capillaries

vessels that allow for the exchange of nutrients/gasses with tissues

venules and veins

vessels that carry block back toward the heart

blood

plasma, hematocrit

hematocrit

primarily red blood cells, white blood cells, platelets. hematocrit explains why blood is actually thicker than water

main functions of the cardiovascular system

transport O2 and nutrients to tissues, removal of CO2 and removal of metabolic by-products, regulation of body temperature

systemic circuit

left side of the heart, pumps oxygen-rich blood to the whole body via arteries, returns oxygen-poor blood to the right side of the heart via veins

pulmonary circuit

right side of the heart, pumps oxygen-poor blood to the lungs via pulmonary arteries, returns oxygen-rich blood to the left side of the heart via pulmonary veins

cardiac output (Q)

total amount of blood ejected from the heart per min (L/min), product of heart rate and stroke volume

Q = HR x SV

arterial blood pressure

systolic/diastolic

systolic pressure

top number, pressure generated in aorta/arteries due to the heart's ventricular contraction (systole)

diastolic pressure

button number, pressure in the aorta/arteries during the heart's ventricular relaxation (diastole)

central command theory

initial signal to "drive" cardiovascular system comes from higher brain centers, located in medulla oblongata

decrease in heart rate

parasympathetic nervous system, vagus nerve releases acetylcholine, slows HR by inhibiting SA and AV nodes

increase in HR

sympathetic nervous system, increases HR by stimulating SA and AV nodes, uses norepinephrine at beta receptors in heart

factors affecting heart rate at rest

age, biological sex, posture, ingestion of food, emotion, body temperature

end-diastolic volume (EDV)

Volume of blood in the ventricles at the end of diastole , like filling a water balloon with more and more water

regulation of venous return

venoconstriction: reducing the volume of the veins

skeletal muscle pump: rhythmic skeletal muscle contractions force blood in the extremities toward the heart

respiratory pump: increased rate and depth of breathing promotes blood flow toward the heart

total peripheral resistance (aortic blood pressure)

pressure that the heart must pump against to eject blood into the systemic circuit

strength of ventricular contraction

"contractility"; increased contractility results in higher stroke volume; circulating epinephrine and norepinephrine cause a direct sympathetic stimulation of the heart

factors affecting stroke volume at rest

posture/gravity, size of heart, non-pathologic cardiac hypertrophy, pathologic cardiac hypertrophy

non-pathologic cardiac hypertrophy

an exercise-induced increase in the thickness of the heart walls, with an increase in the chamber size

pathologic cardiac hypertrophy

a disease-induced increase in the thickness of the heart walls, with a decrease in the chamber size

Q versus VO2 at max

cardiac output (Q) during maximal exercise can increase 4-8 times

oxygen consumption (VO2) can increase 10 to 20 times at max