IB biology HL: B3.3 - muscles and motility

motility

ability to move as a living organism

bones - purpose

• protect vital organs

• provide framework for rest of body

• blood cell synthesis in marrow

• storage of minerals ( calcium )

• act as levers

cartilage - purpose

• reduces friction between bones 

• absorbs pressure

ligament 

connective tissue that attaches two bones together

types of joints

• hinge joint : only one direction 

• ball and socket joint: allows movement in 3 planes

they act as a lever

synovial fluid

lubricating fluid

method used by some bacteria to locomote

rotation of flagella, which propels bacteria forward

types of muscles

• skeletal muscles: voluntary contration

• cardiac muscles/smooth muscles: involuntary contraction

why the need for locomotion

escaping danger, foraging for food , searching for mates, migration, dispersal.

motile organisms

capable of independent movement; cheetah, tuna,, bacteria with flagellum

sessile organisms

unable to move independently; are anchored to a substrate; plants, corals, barnacles when adults, algae…

sarcomeres

repeating units made of two proteins - actin and myosin

boundaries are defined by Z disk, in the center is the M line

actin

thin filaments making sarcomeres

I bands are regions of sarcomere where only actin filaments are present

myosin

a protein/filament, the thicker one, making up sarcomeres. 

A band is where myosin is present, and which has overlap with actin

H band area inside A band without any actin

motor unit

what causes muscle contraction

junction between he motor neuron and the skeletal muscle fibers

neuromuscular junction 

myofibrils

a series of sarcomeres

sarcoplasmic reticulum

specilised endoplasmic reticulum; they store calcium ions which they release when contracting the muscle fibers

what does a muscle contraction do

• filaments in themselves do not change size

• actin slides next to myosin; myosin stays still

• this shortens the sarcomeres

• muscle fiber gets shorter

• dark band stays the same, light band decreases

skeletal muscles big yap

voluntary control- contract or relax from signals of nervous systems

bundles of muscle fibers 

made of many myofibrils, made of sarcomeres, alternating actin ( anchored at Z line ) and myosin ( anchored at center of sarcomere on M line )

cross bridges of myosin filaments bind to binding sites on actin, allowing them to drag it towards each other

when muscles are relaxed, tropomyosin in binded on actin binding sites, preventing the bridges between the long and short fibers from being created 

when muscles contract, calcium ions are released from sarcoplasmic reticulum, which bind to the troponin, changing it’s shape, moving troponin away, and allowing the cross bridges to be created and making the actin move towards the M line 

troponin and tropomyosin

tropomyosin is a long fiber. it’s over the myosin binding site in actin, not allowing the myosin head to bind actin.

When calcium ions are present, they will bind to troponin, a protein attached to tropomyosin, which makes the troponin undergo a physiological change, which moves the tropomyosin away, and leaves the binding sites free.

muscles contracting

tropomyosin is a long fiber. it’s over the myosin binding site. when calcium ions come, they will bind to troponin, a protein attached to tropomyosin, which moves the tropomyosin away, and leaves the binding sites free.

• active site exposure between myosin head

• cross bridge formed, requires atp, between actin and myosin 

• myosin head pivots up, moving actin

• cross bridge gets detached ( needs atp ) 

• continues if ATP is available and calcium level is high

titin

it is a polypeptide, which acts like a spring. found in sarcomeres, prevents overstretching of relaxed muscle

antagonistic muscle pairs

when one relaxed, the other contracts.

antagonistic muscle pairs examples

• biceps, triceps

• internal and external intercoastal muscles

• quadriceps and hamstring

joints

each joint acts as a pivot point => act as levers

elbow joint

• hinge joint

• angular movement in only one dorection

• flexion + extension

radio ulnar joint 

• pivot joint 

• movement in all rotational directions 

hip joint

• connects pelvis and femur

• ball and socket

• angular movement in many direction

• flexion, extension, abduction, adduction, rotation circumduction

articular cartilage

covers the end of the bones in a synovial joint, acting as a cushion to absorb shock, and has a smooth surface to facilitate movement of bones

synovial joint

joints in which bones are separated by fluid filled capsules, called synovial fluid, which acts as a lubricant between joints

factors which affect range of motion of joints

• age

• estrogen

• muscles ( can get in the way )

range of motion of the joint: what does it refer to ?

type and amount of movement possible in a specific joint

how to measure range of motion of a joint

• a goniometer: measures the angle at which a bone can move relative to it’s resting position

• computer analysis can also be used, works more quicklya and in multiple planes of movement from a video

exoskeleteons 

• skeletal system

• external armour for soft inside

• periodically sheds as animal grows

external intercoastal muscles

• perpendicular to internal intercostal muscles, antagonistic pair

• closest to surface of body

• the actual muscles are diagonal down

• when contract, ribcage goes up and out

internal intercoastal muscles

• perpendicular and deeper compared to external intercoastal muscles, antagonistic pair

• the actual muscles are diagonal up, to middle of ribcage

• when they relax, ribcage goes down and in

• when forced exhalation happens, they contract

innermost intercoastal muscles

deepier, behind internal intercostal muscles, and supports forced expiration during heavy breathing

adaptations for swimming in marine mammals

• streamlined bodies that minimise drag

• adaptations in forelimbs to form flippers, which can be used for steering and to generate lift

• tails forming fat and wide fluke: can be used for steering and propulsion of water by moving up and down

• changes in airways to allows for long periods without dives; waves and dolphins, blowholes; allow to breathe without stopping/ lifting head

• myoglobin present in higher quantity in muscle tissues, allowing them to hold onto oxygen for longer periods of time

• larger lungs and blood volume relative to body size, allowing more oxygen to be taken in each breath and to be stored

• large size= smaller surface area to volume ratio, less heat loss to conserve energy

• no connections between lung and trachea