muscle anatomy 1

what is the cell shape, nuclei, control and location to skeletal muscle?

long cylindrical, striated

many nuclei

voluntary

attached to many bones

what is the cell shape, nuclei, control and location to smooth muscle?

long but tapered

1 nuclei, not straited

involuntary control, connected to organs

what is the cell shape, nuclei, control and location to cardiac muscle?

long, BRANCHED

striated

1 nuclei, involuntary found in heart!

what is the neuromuscular junction?

axons of motor neurons extend from spinal cord towards muscle!

divides into axon terminals that form NEUROMUSCULAR JUNCTIONS with muscle fibers across muscle. (1 per fiber)

action potential/electrical impulse travels down this axon into synaptic terminal, opeing voltage gated Calcium Channels

calcium enters neuron terminal.

what is the anatomy of the neuromuscular junction?

calcium channels open, enters neuron terminal. triggers:

Synaptic vesicle contains acetylcholine (inside the axon terminal)

via exocytosis, releases Ach into synaptic cleft, connecting to the ACh receptor of motor end plate.

channel opens, Na+ floods in!

how does a muscle action potential generate?

1. action potential will arrive at synaptic terminal

2. calcium channels open

3. enters synaptic terminal

4. acetylcholine released into synaptic cleft via exocytosis

5. binds to receptors, Na+ rushes into cell

6. action potential spreads across surface of sarcolemma

   1. ACh broken down by AChE

7. returns to intial state, cycle beings again if another action potentia larrives at neuromuscular junction

8. Na+ channels outside of endplate open, causing more Na+ to rush in, K Out, etc eetc

What is excitation contraction coupling?

From the neuromuscular junction and after an action potential is generated in the sarcolemma, it travels along an down into the T Tubules

DHP receptors activated, opeing Ca release channels.

Ca2+ ions released from Sarcoplasmic reticulum

binds to troponin, removing the blocking action of tropmyosin

troponin shape changes, revealing binding sites for myosin on the thin filaments

binding occurs, cross bridges form, contraction begins.

what does the thin myofilament consist of? how does it contribute to contraction?

2 strands of actin sub units (twisted into helix)

two regulatory proteins

• troponin

• tropomyosin

calcium binds to troponin, reveals binding sites for myosin, binding to the actin and forming a cross bridge.

what is the anatomy of a muscle fiber/cell

surounded by sarcolemma (muscle membrane)

• sarcoplasmic reticulum

• terminal cisternae

• T tubule

• triad

What is the cross bridge formation?

when mysoin (energized via holding ADP and P) attaches to newly exposed site on actin(via excitation contraction coupling).

myosin head pivots due to release of ADP P, pulling actin foilament towards center of sarcomere.

How does the myosin deattach from actin?

new molecule of ATP attches to myosin head, detaching the two

ATP is hydrolyzed into ADP P, “re cocking” myosin head into high energy position.

ready to pul again via ratchet mechanism if ATP is available

and if Ca is stil bound to troponin

how does the muscle relax?

Acetylcholine is broken down or diffuses away from neuromuscular junction

as a result no action potentials travel down

Ca2+ is returned to SR via protein pumps

Troponin stops binding to Ca2+, tropomyosin comes back and blocks binding site for myosin

what are 3 different sources for ATP for muscle contraction?

creatine phosphate - combines with ADP to create creatine and ATP

Anaerobic metabolism of glucose via glycolysis

aerobix metabolism of glucose and fatty acids.

what types of ATP are used in short duration exercise vs prolonged duration exercise?

6 seconds - ATP stored in muscles

10 seconds - ATP formed from creatine phosphate (phosphorylation)

30-40 - glycogen stored in muscles broken down to glucose, oxidized to pyruvate to generate ATP (anaerobically)

hours - full odixation of fats and carbs to CO2 and H2O

what is hypotonia and hypertonia

hypotonia - flaccid

hypertonia - spasticity

what influences muscle size

lack of use

aging

disease - dystrophy

Training

Hormones Anabolic - steroids

what is the microscopic anatomy of cardiac muscle

cells interlock at the cell membranes intercalated disks

• connect gap junctions and desmosomes

gap junctions

• ion channels between cells

• allow cells to be coupled electrically

  • functional syncytium

desmosomes

• molecular velcore

• binds cells together

what is autorhythmicity? how does heart contract

craeted by pacemaker

• clsuter of non contractile cardiac cells

• unstable membrane potentials that depolarize sponatenously and rhythmically

  • triggers action potentials that spread throughout heart

uses ATP from aerobic metabolism only

What is smooth muscle fiber anatomy?

intermediate filaments- transmit pull from contractile filaments to whole cell

caveolae - infoldings of sarcolemma(many Ca2+ channels)

Gap Junctions - ion channels between cells

Dense bodies - attachment point for thin and intermdiate filamentes(similar to Z disks in skeletal muscle)

Where are neurotransmitters released from in smooth muscle fibers?

from swellings (varicosities) on the axons of autonomic neurons through diffusion

• not localized to a neuromuscular junction!!

what is the excitation contraction coupling process like in smooth muscle?

calcium ions enter cytosol via Ca2+ channels or scant SR from ECF!

binds to and activates calmodulin

calmodulin activates myosin kinase

myosin kinase catalyzes transfer of phosphate to myosin

activated myosin forms cross bridges with actin of thin filaments, contraction!

how does smooth muscle relax

enzymes remove phosphate from mysoin, (doesnt activate)

no action potenials, Ca2+ channels wone open

• moved out of the cell into SR by protein pumps

calmodulin wont activate, netiher will kinase, nor myosin

what is the affect of neurotransmitters o nsmooth muscle contraction? what about hormones?

acetylcholine - PNS stimulates contraction, bronchioles pupils constriction

norepinephrine - SNS - does both

• dilation of bronchioles/pupils, but constriction of blood vessels depending on the area

gastrin, stimulates gastric motility when food in stomach

cholecystokinin relaxes hepatopancreatic sphincter when food is in intestine

oxytocin

• stimulate contraction of uterus, ducts of mammary glands during breast feedings