Physiology - Test 3

Somatic motor

• 1 nueron

• originates in CNS

• always excitatory

neuromuscular junction

• b/w motor nueron and skeletal muscle fiber

• lots of ACh - nicotinic receptor

skeletal muscles

• striated

• multinucleated

• voluntary control

cardiac muscle

• striated

• uninucleated

• involuntary

• 
  

smooth muscle

• internal organs

• influences movement of material into and out of body

Tendons

attach bone to muscle

• made of collagen

origin of muscle

proximal end of limb

insertion of muscle

distal end of limb

fascicle

muscle fibers bound together

sarcolemma

muscle cell membrane

sarcoplasm

muscle cell cytoplasm

Myofibril

bundles of elastic protiens that carry out contraction

myosin

forms thick filaments - enzyme for ATP

actin

forms thin filaments

tropomyosin

protein polymer - binding site for actin

troponin

calcium binding - moves tropomyosin

cross bridges

mysoin heads of thick filaments bind to actin

sarcomere

pattern of thick/thin filaments - 1 repeat

• contractile unit of myofibril

contraction

myosin and actin sliding over each other

sarcoplasmic reticulum

• wraps around each fiber

• concentrates and stores calcium

transverese tubules

• extension of sarcolemma

• dips into sarcoplasm

• brings action potential closer to center of fiber

terminal cistrae

enlarged end region

triad

1 t-tubule + 2 flanking terminal cisternae

muscle tension

force created by contracting muscle

load

force opposing muscle contraction

contraction

creatoon of tension in a msucle

power stroke

• calcium signal initiates

• myosin cross bridges push actin filaments towards center of sarcomere

• 1 power stroke per contraction

steps for power stroke (5)

1. calcium concentration increases in cytosol

2. calcium binds to troponin

3. troponin pulls tropomyosin away from actin binding site (previously covered)

4. myosin binds to actin and performs power stroke

5. actin filament moves

relaxion

calcium concentration decreases - slow process (why summation is common)

Draw Excitation-contraction coupling and relaxation

Draw contraction cycle

Muscle twitch

single contraction-relaxation cycle

3 phases for muscle twitch

• latent period

• period of contraction

• period of relaxation

latent period

events of excitation - contraction coupling (no muscle tension)

• short delay b/w Action Potential and tension - caused by time required for calcium release and binding of troponin

period of contraction

cross bridges form - tension increases

period of relaxation

calcium goes back into SE - tension goes to zero

temporal summation

frequency of stimulation

• more calcium releases before calcium used in first twitch can go back into SE

• produces smooth and continuous contractions

size principal

number and type of motor neurons recruited

• motor units with smallest muscle fibers recruited first (most excitable)

• the largest motor units only recruited for very powerful contractions (least excitable)

phosphocreatine

backup energy source for muscles (creatine + ATP) - muscle cells have lots of creatine kinase

anaerobic glycolysis

glucose metabolized to lactate (2 ATP per glucose)

Unfused tetanus

maximum contraction and remains there

• caused by increase in stimulus frequency

motor unit

1 neuron and its muscle fibers (all same fiber type) - 1 action potential effects all fibers

recruitment

involving other motor units to increase strength of contraction

• asynchronously activated to prevent fatigue

low threshold neurons

control fatigue-resistant, slow-twitch muscle fibers

Heart

Pumps blood

capillaries

microscopic vessels where blood and interstitial fluid exchange materials

blood

cells and plasma

cardiovascular system

transports materials through body

blood vessels

hollow tubes transporting blood throughout the body

substances moved by cardiovascular system (3)

1. nutrients/water/gases that come from external environment

2. materials moving from cell to cell in body

3. wastes that cells eliminate

arteries

carry blood away from heart

• (usually oxygenated)

Veins

bring blood to heart

• (usually deoxygenated)

pulmonary circulation

takes blood to and from lungs

systemic circulation

takes blood to and from body

Atrium

• upper chamber

• receives blood entering heart

ventrical

• lower heart chamber

• pumps blood out of heart

septum

• divides heart into left and right halves

• keeps oxygenated and deoxygenated blood from mixing

right side job

• receives blood from tissues

• sends to lungs for oxygenation

left side job

• receives oxygenated blood from lungs

• pumps blood from heart to tissues

pulmonary arteries

pumps deoxygenated blood from right ventricle to lungs

pulmonary veins

pumps oxygenated blood from lungs to left atrium

aorta

transports oxygenated blood from left ventricle to tissues

superior vena cava

transport deoxygenated blood from veins from upper part of body to right atrium

inferior vena cava

transport deoxygenated blood from veins from lower part of body to right atrium

parallel circuits

blood entering and exiting both ventricles simultaneously

aortic sinus

pericardium

membranous sac around heart

myocardium

cardiac muscle

atrioventricular valves

• 2 sets

• move blood between aorta and ventricles

• closed during contraction

• prevents blood from flowing back into atria

2 types of Atrioventricular valves

• tricuspind (right AV valve)

• mitral (Left AV valve)

semilunar valves

• move blood from ventricles to arteries

• prevent back-flow into ventricles

Chordae Tendinea

anchor the AV valve to prevent it from flipping inside out (cause of “broken heart syndrome”

ventricular contraction

• semilunar valves - open

• ventricles - contracted

• chordae tendinae - tense

• AV valves - closed

ventricular relaxation

• semilunar valves - closed

• ventricels - dilated

• chordae teninae - relaxed

• AV valves - open

anastomosis

alternative routes blood can take to the same capillary bed

diastole

when heart is relaxed

systole

when heart is contracting

coronary circulation

blood vessels feeding cardiac muscles encircling heart near base

blood circulation route (6)

• right atrium

• right ventricle

• lungs

• left atrium

• left ventricle

• body tissue

Autorhythmic cells

• send signals for myocardial contractions (do not contract themselves)

• self-generate action potentials

• 1% of cardiac cells

• make up the sinoatrial and atrioventricular nodes

contractile cells

• perform physical contractions of the heart

cardiac myocytes

• contractile cells

• striated fibers organize into sarcomeres

• contractions cause blood to pump through heart

Skelatal muscle differences from Cardiac muscle (9)

Skeletal muscle:

• multinucleated

• fibers as long as whole muscle

• 3 subtypes (skeletal, smooth, cardiac)

• fast glycolytic (aerobic mostly)

• can perform summation

• Action potentials between 1-2 ms

• use neuromuscular junctions

• muscle fibers are at optimal length for contraction

• voluntary - only contract using somatic NS

Cardiac Muscle differences from skeletal muscles (9)

Cardiac Muscle:

• only 1-2 nuclei

• shorter, branched muscle fibers

• 2 sub types (contractile + autorhthmic)

• only aerobic respiration (very mitochondria heavy)

• Action potentials every 200-300ms

• cannot use summation

• use intercalated disks instead of neuromuscular junctions

• fiber length shorter than optimal length

• autonomic NS modifies rate of contractions

intercalated disks

• cell junctions between cardiac myocytes

• contain desmosomes and gap junctions

desmosomes

• physically tie adjacent myocytes together

• allows force to be transferred from cell to cell

gap junctions

• allow electrical connection between myocytes

• allow depolarization - contraction happen almost simultaneously through myocytes

autorhythmic cardiac fibers

make up SA and VA nodes

pacemaker potential

• unstable membrane potential of autorhythmic cells

• potential eventually depolarizes to threshold causing action potential

• due to If cannels

If channel

• causes pacemaker potential

• inflow of Na+

• (na+ flow higher than k+)

• gradually close as cell depolarizes - different Ca+ channels open

actions of autorhythmic cell at threshold

• different Ca++ channels open - steep depolarization

• close at peak of action potential

• K+ have opened and releases K+

• 
  

Actions of autorhthumc cell at peak

• Ca++ channels close

• K+ channels open - leaves cell

• pacemaker potential returns to lowest point

Actions of autorhthmic cells during repolarization

• K+ open and K+ leaves cell

draw and label EC coupling in contractile cardiac muscle

steps of action potential in contractile cardiac cell

0. Na+ channels open

1. Na+ channels close

2. Ca++ channels open & fast K+ channels close

3. Ca++ channels close & slow K+ channels open

4. resting membrane potential

cardiac cell refractory period

• same duration as action potential

• summation not possible

plateau

there is a plateu in the repolarization period of cardiac contractile cells

• caused by 2 things:

  • decreased permeability to K+

  • increased permeability to Ca++

• helps slow action potentials, prevent summation and prevent tetanus

Conducting system of heart steps (5)

1. SA node depolarizes

2. electrical activity rapidly moves to AV node

3. depolarization slowly spreads across atria

4. depolarization rapidly spreads across ventricles to apex

5. depolarization wave spreads upward from apex

bradychardia

heart rate below 60 BPM

tachycardia

heart rate over 100 BPM