Human Physiology - Unit 2 - Muscle

Skeletal muscle

appearance: striated + cylindrical

action: voluntary

location: attached to bone

nucli: 100-1000 per cell

cardiac muscle

appearance: straited and branched

action: involuntary

location: heart

connected at an intercolated disc to each other

smaller

smooth muscle

appearance: not striated

action: involuntary

location: walls of hollow organs (esophagus, digestive tract)

regulates blood pressure and blood flow

found in sphincters (bladder)

help move things along long passages

body movements, stabilize body positions, generate heat

skeletal muscle functions

electrical excitability

(a property of skeletal muscle) ability to respond to stimuli by producing action potentials

contractility

(a property of skeletal muscle) ability to contract forcefully when adequetly stimulated

extensibility

(a property of skeletal muscle) The ability to stretch without being damaged

somatic nervous system

The division of the peripheral nervous system that communicates with skeletal muscles

uses Ach to send signals to N Ach R

axon exits the spinal cord at the ventral root

whole muscle

a bundle of muscle fibers

muscle fascicle

a bundle of muscle fibers

muscle fiber

a muscle cell

cytoplasmic space is mostly filled with myofibrils

myofibrils

contractile element made of sacromeres

sacromere

contractile subunit with overlapping protein filiments

myosin

primary protein of thick filiments

ATP driven

actin

primary protein of thin filiments

provides the track that myosin moves along

tropomyosin

regulator of muscle contraction

blocks myosin during relaxaton, moves out of the way during contraction

7

_ actin : 1 Tm

troponin

regulator of muscle contraction

3 subunits on thin filament

locks Tm in place

calcium-binding molecule

Titin

3 per sacromere

act like a spring, pulls back after stretching

acts as a ruler to make sure the thick filament doesn’t get too long

Nebulin

a molecular ruler

one micron long

Alpha-actinin

major protein component of the z-line

 myomesin and m-protein

major components of m-line

sarcolemma

muscle plasma membrane in skeletal muscle

*In skeletal and caridac muscle, it has openings to connect to the T-tubes

transverse tubles

passages through the muscle cytoplasm that encircle the myofibrils

sarcoplasmic reticulum

a specialized ER found encircling myofibrils in muscle

contain a high concentration of calcium

calcium

What is used as a second messenger in muscles

pre-synaptic terminal

neuronal axon terminal

post-synaptic target

post-synaptic side

End plate potential

local depolarization die to Ach binding to N-Ach R

Creates action potential if  it exceeds threshold for voltage gated Na+ channels

Motor end plate

specialized region of the skeletal muscle membrane

*enriched in N-Ach R, so it can depolarize end plate

DHP

when moved, Ca+ can flow into the cytoplasm to find the troponin molecules

*Ca+ concentration is high outside, so it is a rapid rush

pump protein

when muscle is at rest, the _____ _______ uses ATP to pump Ca back into the SR

myosin

when contracting, _____ needs ot attach to thin filaments and pull them in both halves of the sarcomere

leads to muscle shortening

releases myosin from actin, and provides energy for the calcium pump and force production

what are the 3 roles of ATP in skeletal muscle

isometric contraction

muscle contracts, but does not shorten

isotonic contraction

muscle contracts and shortens

Creatine Kinase

one step reaction

all muscles have it

reserved energy source

Creatine Kinase

(type of energy metabolism) takes phosphate off atp and transfers it to an amino acid, like creatine

creatine is only used in this mechanism

takes the phosphate off the amino acid to turn adp into atp

When using ATP, what does creatine kinade do to create more

4x

how much more creatine is stored in muscles than ATP

Glycolysis

slow multistep reaction

anarobic

powers relatively short periods of muscle activity

blood from eating and breakdown of muscle glycogen

what are the 2 sources of glucose for glycolysis

2 ATP and 2 Pyruvate

what does the one glucose break down into in glycolysis?

oxidative phosphorylation

where does the 2 pyruvate go from glycolysis if oxygen is available

oxidative phosphorylation

multistep reaction

requires oxygen and mitochondria

converts 1 glucose to 36 ATP

converts fatty acids and amino acids to ATP

Byproducts: CO2 and H2O

Slow oxidative

red muscle

slow myosin aerobic metabolism

type 1

mostly oxidative phosphorylation

many mitochondria and capilaries

resistant to fatigue

less tension

small diameter cells = ???

oxygen diffusion

what does myoglobin aid in slow oxidative muscle fibers

fast-oxidative

type 2a

has the capacity to do oxidative phosphorylation and glycolysis

large diameter filled with myofibrils to make it stronger

large amounts of myoglobin, but less than type 1

somewhat resistant to fatigue

fast myosin ATPase

fast glycolytic

large diameter

fast myosin ATPase

mostly glycolytic metabolism

large amounts of glycogen

few capillaries and mitochondria

no myoglobin

prone to fatigue

doesn’t require oxygen

what does a large diameter mean in muscle fibers

fast tension development

What does fast myosin ATPase cause in muscle fibers

motor unit

a motor neuron and the muscle fibers it innervates

recruited

the larger amount of tension, the more motor neurons are _______

Fatigue

trying to stimulate a muscle, and it doesn’t respond normally

muscle fatigue

high ECF K+ concentration, buildup of adp, and disruption of calcium regulation causes what

number of active motor units, number of muscle fibers in each motor unit, and fiber types

what are the 3 factors to tension development

lower motor neurons

somatic neurons

communicate with the brain stem

Receive commands from 4 levels

basal nuclei, cerebrum, local circuit neurons, upper motor neurons

What are the 4 levels the lower motor neurons receive commands from

cerebral cortex and brainstem

what makes up the upper motor neurons

Vestibular nuclei

(upper motor neuron; indirect motor pathway) controls posture and balance

Reticular formation

(upper motor neuron; indirect motor pathway) controls posture and muscle tone

medial

(reticular formation tract) excites muscles

lateral

(reticular formation tract) inhibits muscles

Superior Colliculus

(upper motor neuron; indirect motor pathway) assists with movements of the head, trunk, and unexpected shifting eye movements

decussates

decussation

passing from one side of the spinal cord to the other

red nucleus

controls voluntary movements of the upper limbs through the rubrospinal tract

Corticospinal pathways

voluntary control of skeletal muscles of the body (limb+trunk)

allows for the the right side of brain to control the left side of the body, and vice versa

lateral corticospinal tract

crosses the midline of the body at the medulla

responsible for precise movements of the hands and feet

ventral corticospinal tract

crosses the midline of body at spinal cord

responsible for trunk and proximal parts of limbs

basal nuclei

several masses of grey matter in cerebral hemispheres

control initiation of movement

control the suppression of unwanted movements

regulation of muscle tone

regulation of non-motor processes

tonic inhibition of neurons in the thalamus

how does the basal nucleus suppress unwanted movements

regulation of muscle tone

keeps muscles from being completely relaxed

communicates through the reticulospinal tracts

non-motor processes

attention, memory, planning, and emotional behaviors

the cerebellum

monitors the intention of movement and actual movement

compares command signals with sensory information

sends out corrective feedback

smooth muscle

tapered towards ends

one central nuclei

have thick filiments and thin filiments

thick filiments

myosin throughout (no bare zone at center)

thin filaments

composed of actin and tropomyosin, no troponin

bound to membrane-anchored protein assemblies (no z-bodies)

dense bodies

linked by intermediate filaments

desmosomes

cells are attached to each other by _______

arteries

(smooth muscles help with this in what part of the body) regulates blood pressure

arterioles

(smooth muscles helps with in what part of body) regulate distribution of blood flow

airways

(smooth muscles helps with in what part of body) regulate airflow in the bronchi of lings

stomach

(smooth muscles helps with in what part of body) mix contents

intestines

(smooth muscles helps with in what part of body) move contents from stomach to rectum

bladder

(smooth muscles helps with in what part of body) store and expel urine

uterus

(smooth muscles helps with in what part of body) expel baby

saturates troponin resulting in a twitch

In the skeletal muscle, what is the role of calcium in muscle contraction

it determines the amount of tension

In the smooth muscle, what is the role of calcium in muscle contraction

voltage and ligand-gated channels, stretch-activated cation, and intracellular stores

where does Ca+ come from

troponin

(smooth muscle) there is none of this contractile protein

calmodulin

calcium sensor

myosin light chain sensor

activated by Ca-calmodulin

phosphorylates myosin’s regulatory light chain when active

myosin light chain phosphatase 

Dephosphorylates myosin’s regulatory light chain to relax smooth muscle

length tension relationship

the optimum length permits maximum tension generation in smooth muscle contraction

relaxation

A decrease of Ca levels and the dephosphorylation of myosin by MLCP causes what in smooth muscle

single unit smooth muscles

are connected by gap junctions

excitation of one cells results in excitation of all

ex: stomach

Multi-unit smooth muscle

activates individually after the reception of the activating signal

ex: eye

pacemaker cells

unsteady resting membrane potential, due to leaky ion channels

slow waves

type of autorythmic behavior which is the undulating membrane potential

a stimulus will only reach threshold when ______ is near it crest