Anatomy Exam 3

skeletal muscle

long, multi-nucleated, striated, muscle that is connected to nerves and used in voluntary movement

cardiac muscle

shorter, uni- or bi-nucleated, branched, striated muscle used in involuntary movement and connected by gap junctions

smooth muscle

short, spindle-shaped, uni-nucleated muscle involved in involuntary movement and connected by gap junctions

endomysium

a thin layer of connective tissue that holds muscle cells together

contractility

the ability of fibers to draw together

excitability

response to stimuli

conductivity

the ability to conduct electricity

extensibiliy

the ability to be stretched

elasticity

the ability to regain original state after stretching

myocyte

a muscle cell responsible for muscle contraction

sarcoplasm

cytoplasm of a myocyte

sarcoplasmic reticulum

modified endoplasmic reticulum in myocytes with Ca2+ ion channels between t-tubules and terminal cisternae and Na+ ion channels at the edge of myofibrils and the indention of them that form a neuromuscular junction

sarcolemma

a fine, transparent sheath that envelops skeletal muscle fibers

myofibrils

structures found in all myocytes that are made up of bundles of specialized proteins that allow for contractions

epimysium

covering surrounding muscle that continues as the tendon

fascicle

a bundle of cells and endomysium gathered together by perimysium

t-tubule

a deep inward extension of the sarcolemma that conducts action potential deep inoto mucle fibers, surrounds each myofibril, is continuous with the cell exterior, and is filled with ECF

terminal cisternae

enlarged sections of the SR that flank each side of a t-tubule

thick filaments

myofibrils made up of bundles of myosin

thin filaments

myofibrils made up of actin, tropomyosin, or troponin

elastic filaments

myofibrils made up of titin

I band

sarcomere section made up of only thin filaments

Z disc

the middle of the I band, where structural proteins that anchor thin filaments in place and to one another reside and serve as points of attachment for elastic filaments and attach myofibrils to each other

A band

sarcomere section that contains the zone of overlap between thick and thin filaments and generates tension during contraction

H zone

the middle of the A band where only thick filaments exist

M line

the dark line in the middle of the A band where structural proteins hold thick filaments in place and serve as anchor points for elastic filaments

electrical gradient

the separation of charged particles across the plasma membrane

electrical potential

potential energy due to the sarcolemma creating a gradient

voltage

the difference in electrical potential between 2 points

membrane potential

electrical potential difference on either side of the cell membrane, generated by Na/K pumps

resting phase

the first phase in action potentials where gated channels are closed and Na+/K+ gradients are maintained by pumps and K+ leak channels

depolarization phase

the second phase in action potentials where Na+ channels open in response to a depolarizing stimulus and Na+ enters the cell down its gradient, further depolarizing the membrane

repolarization phase

the third phase in action potenranetials where Na+ channels close, K+ channels open, and K+ exits down its gradient and repolarizes the membrane

neuromuscular junction

where motor neurons stimulate skeletal muscle contractions

acetylcholine

a neurotransmitter that initiates muscle excitation

troponin/tropomyosin

myofibrils that regulate access to actin binding sites

myosin

motor protein that drives contraction

excitation/contraction coupling

acy releases from the axon terminal and binds to receptors on the sarcolemma, generating an action potential that travels down the T-tubule, creating a voltage change that releases Ca2+ from the SR, which binds to troponin, triggering a cross-bridge to form between actin and myosin; acetylcholinesterase removes acy from the synaptic cleft, Ca2+ is transported back to the SR, and tropomyosin binds active sites on actin, causing the cross-bridge to detach

contraction phase

part of the cross-bridge cycle where ATP triggers myosin heads to bind to actin active sites, creating a crossbridge, myosin releases ADP and P and a power stroke pulls actin toward the M line; after, the binding of new ATP breaks the crossbridge, starting the cycle over

creatine phosphate

the immediate source in contraction that yields 1 ATP from 5 CP in 10 sec

anaerobic glucose catabolism

glycolysis that produces 2 ATP in 1 min from 1 glucose

aerobic glucose catabolism

Krebs cycle that yields 38 ATP from 1 glucose

myogram

graph that records muscle tension with time in ms in the x-axis and tension in the y-axis

unfused tetanus

muscle tension where the muscle doesn’t completely relax between stimuli (50x per sec)

fused tetanus

muscle tension where the muscle gets no break between stimuli (100x per sec)

type I muscle fiber

slow twitch muscle fiber with low myosin ATPase activity, extended periods of contraction, a largely oxidative metabolism, and well-developed blood supply, myoglobin, and mitochondria

type I subtype

slow oxidative fibers

type II muscle fiber

powerful fast twitch muscle fiber with high myosin ATPase activity that quickly fatigues, a largely anaerobic metabolism, smaller blood supply, and less myoglobin and mitochondria

type II subtypes

fast oxidative glycolytic, fast oxidative, fast glycolytic

motor units

single motor neurons with multiple axon branching that stimulate 150 fibers on average

concentric contraction

when the force generated by muscle is greater than the load and the muscle shortens

eccentric contraction

when the force generated by muscle is less than the load and the muscle lengthens

isometric

when the length of muscle doesn’t change

skeletal muscle functions

locomotion, breathing, swallowing, sound modulation, voluntary control, shivering

agonists

prime movers that provide the most force for a mucle action

antagonists

on the opposite side of bones and joints from agonists and modulate and control agonist movement

synergists

aid agonists by supplying supplemental force, stabilizing joints

fixators

provide movement efficiency and protection from injury cause by unnecessary movements

lever system

a system consisting of a load, a force, and a fulcrum or pivot point

1st class lever system

a fulcrum is placed between the load and force applied

2nd class lever system

a fulcrum is at one end, with the load in between and force applied at the other end

3rd class lever system

the fulcrum and force are near the same end, with the load at the other end

myoplasticity

change in muscle structure due to changes in function in training

endurance training

exercise with a large increase in frequency of motor unit activation and a medium increase in force production, causing biochemical changes in type I muscles and some type II, increasing oxidative enzymes, mitochondria production, fatigue resistance, and efficiency of fatty acid and non-glucose fuel for ATP production

resistance/strength training

exercise with a medium increase in frequency of motor unit activation and a large increase in force production, causing anatomical changes in the number of myofibrils and the diameter of fibers

nervous system

a physically connected network of cells, tissues, and organs that allow us to communicate with and react to our environment

central nervous system

part of the nervous system in charge of integration and control that includes the brain and spinal cord

100 billion

how many neurons the brain has

100 million

how many neurons the spinal cord has 

peripheral nervous system

part of the nervous system that sends impulses to and from the spinal cord and brain

12

how many pairs of cranial nerves there are

31

how many pairs of spinal nerves there are

nervous system functions

sensory input, integration, motor output

afferent division

receives information

somatic sensory division

afferent division that carries general sensory stimuli from muscles, bones, joints, and skin

visceral sensory division

afferent division carries stimuli from organs

efferent division

sends information

somatic motor division

efferent division that carries stimuli to skeletal muscles

autonomic nervous system

efferent division that carries stimuli to smooth muscle, cardiac muscle, and glands

sympathetic ANS

prepares the body for stress or danger

parasympathetic ANS

calms the body down

neurons

nervous cells that are 1mm-1m in length, amitotic, long-lived, and excitable

axon

a long, whip-like extension in neurons that generates and conducts action potential

axon hillock

the junction connecting the cell body and axon where the neuron decides whether or not to send an impulse

telodendria

terminal branches of axons that can number 10000+

axon terminals

ends of axons that release signals to target cells

nissl bodies

granular structures composed of rough endoplasmic reticulum and ribosomes found in the cell body and dendrites

dendrites

several branch-like projections that receive action potentials and generate local potentials

anterograde

transport away from the cell body

retrograde

transport towards the cell body

kinesin/dynein

ATP-dependent motor proteins used in neural transport

myelin sheath

protein lipoid that is an extension of the glial plasma membrane and acts as insulation, increasing transmission speed

Nodes of Ranvier

the gaps between Schwann cells in the PNS

slow axonal transport

axonal transport that is only anterograde, travels 1-3 mm/day, and moves cytoskeletal proteins and soluble enzymes

fast axonal transport

axonal transport that moves in anterograde and retrograde, travels 290-400 mm/day, and moves vesicles containing substances and membrane bound organelles

multipolar

neurons with 3+ processes

bipolar

neurons with 2 processes, usually found in the retina

unipolar

neurons with 1 process that is an axon with a distal peripheral process that acts as a sensory receptor and a central process that enters the CNS

spinal motor neuron

multipolar neuron that consists of a cell body with multiple dendrites and an axon

pyramidal cell

multipolar neuron that consists of a cell body with 3 main dendrites and an axon