Mammalian Locomotion Flashcards
(47 cards)
1
Q
What are the factors for locomotion?
A
- bipedal/quadrupedal
- environment & terrain
- size
- body plan
- speed
- gravity
2
Q
What is the general function of cylindrical/long bones?
A
adapted to act as levers
3
Q
Describe short bones
A
- typically seen in carpus and tarsus
- no dimension that greatly excees any other
- helps with complex movements such as rotation and may reduce concussion
4
Q
Describe flat bones
A
- many in skull or pelvis
- offer protection to soft parts
- provide attachment sites for large muscle masses
5
Q
Describe irregular bones
A
- examples include vertebrae
- similar structure to short bones but less uniform
- lie on mid-line and are unpaired
- often specialized function
6
Q
What are the 3 primary regions of skeleton?
A
- axial skeleton: vertebral column, ribs, sternum & skull
- appendicular skeleton: bones of limbs
- Splanchnic/visceral skeleton: bones developed in substance of soft organs
7
Q
What is an example of teh splanchnic skeleton?
A
penis bone in cats
8
Q
What are the functions of the axial - appendicular skeletons?
A
- postural control
- proprioceptive reflex arcs
- pelvic orientation
9
Q
Describe how the axial-appendicular skeleton provides postural control
A
- shift in centre of gravity where top heavy biped needs greater postural control
- quadruped has 4 vertical appendages to suspend body in a balanced way
10
Q
How does the axial-appendicular skeleton form proprioceptive reflex arcs?
A
- myotatic reflex
- activation of stretch receptors in muscle spindle stimulates contract of muscle
- inhibits contraction of antagonist flexor muslce of limb
- similar reflex arcs to stimulate extensors and inhibit flexor muscles of the limb in response to gravity forcing flexion of limb joints
11
Q
How does the axial-appendicular skeleton assist pelvic orientation?
A
- functions of associated muscles
- gluteus medius extends hip
- hamstring rotates pelvis away from femur - extends hip joint and pushes pelvis forward during locomotion
12
Q
What are the advantages and disadvantages of quadrupedal structure?
A
- advantage: naturally resolves balance issue
- disadvantage: issue of attaching limbs to a horizontally orientated body and how they should move in order to make body work
13
Q
Describe quadrupal evolution of vertical limbs underneath the animal
A
- shifted from horizontal to vertical attachment
- causes limbs to rotate instead of protract and retract backwards and forwards
- significant reduction of bony aspect of sternum with coracoid and interclavicle bones lost - only clavicle left
14
Q
Describe the evolution of the clavicle bone
A
- present in mammals with prehensile forelimbs
- absent in sea mammals and those adapted for running
- absence improves running effiecny as scapula not restrained
15
Q
Describe pectoral and pelvic girdles
A
- no longer bony attachment of forelimb to main part of body due to lost clavicle
- attachment of forelimb is muscular by thoracis sling or pectoral girdle
16
Q
Describe the scapular spine
A
- divides supraspinous and infraspinous fossae
- bony protrusion that runs down length of scapula
17
Q
Describe the glenoid fossa
A
- point of insertion of humerus via humeral head
- at bottom of scapular
18
Q
What are the primary functional components of the scapula?
A
- blade width from teres process to cranial border - moment arms of flexors and extensors in shoulders
- orientation of scapular axis - extent of scapular contribution to limb flexion and extension
- size and shape of acromion and coracoid processes - size and moment arms of shoulder muscles
19
Q
How does the blade width from teres process to cranial border in the scapula affect moment arms of shoulder muscles?
A
the wider the blade, the increase in moment arm and the shift from speed to power lever
20
Q
What does the type of lever relate to the point of fulcrum in relation to?
A
forces coming from effort and from resistance or weight
21
Q
Describe the lever and moment arm in relation to the human head
A
- contraction of neck muscles act on joint of head atlas to base of head
- acts againstt downward force of weight of head
- fulcrum in middle position and reasonable mechanical advantage
22
Q
Describe levers and moment arms in relation to raising the human heel from the ground
A
- action of calf muscle is at other end of fulfrum with resistance at mid point
- system of high mechanical advantage where force applied is less than force of resistance
- power lever and slow acting
23
Q
Describe levers and moment arms in relation to the human bicep
A
- point of action of muscle very close to fulcrum with resistance (weight of hand) at other end of the lever
- mechanical disadvantage - force applied greater than resistant force
- fast acting
24
Q
Describe power vs speed levers
A
- if load close to fulcrum and effor far from fulcrum - small effort over large distance can move large load over small distance (power lever, mechanical advantage
- if load far from fulcum and applied near fulcrum - force exerted must be greater than load (mechanical disadvantage, speed lever)
25
Which 2 types of mammals have developed scapular adaptations?
- cursorial / running mammals
- fossorial / digging & natatorial / swimming mammals
26
Describe the scapular adaptations of cursorial mammals
- longer, narrower scapulae positioned vertically compared to ambulatory mammals
- increased rotational ability of scapula which has an overall effect of increasing stride length
- narrow scapula - reduces moment arms of muscles running from scapula to humerus - speed lever
- small acromium process reflects small lateral muscle of shoulder joint - very little rotation or abduction of limb
27
Describe the scapular adaptations in fossorial and natatorial mammals
- triangular scapulae and larger teres process
- increased leverage from teres major muscle - more powerful adduction of forelimb
- absence of large acromium that gives power leverage to deltoid muscles
28
Describe the deltoid muscles
- teres major and deltoid muscles flex shoulder joint and run from scapula to humerus
- deltoid responsible for abducting the shoulder
- muscle moment determined by deltoid tuberosity (point of insertion)
29
Describe deltoid tuberosity adaptations in antelopes and otters
- Antelopes: deltoid tuberosity 1/4 distance down shaft, moment arm for deltoid and teres major is rapid but weak extension/flexion of arm
- Otters: deltoid tuberosity further down shaft, greater power
30
What is key to solving the quadruped issue of transferring propulsive forces from hindlimb through to main part of the body?
- joint between pelvis and spine (pelvic girdle)
- free-ranging movement
- efficient transfer of propulsive force
31
What does the rigidity of spine determine?
forms of gallop: transverse or rotatory
32
Describe a rotatory gallop
- placement of second hindfoot followed by ipsilateral forefoot
- sequence of footfalls appears to rotate around body
- faster than transverse
- more rigid body
33
Describe transverse gallop
- two hindfeet placed in sequence
- placement of second hindfoot followed by contralateral forefoot and then by remaining forefoot
34
What are the most important biomechanical determinants of gallop type?
- body mass
- relative length of limb segments
- aspect ratio - body height/body length
35
Describe appendicular attachment in relation to stride sequence
- largely for maintaining balance
- range of variations of stride sequence or gait - speed and species dependent
- central pattern generator - rhythmic patterened outputs with sensory feedback
- key function is to provide correct timing and sequence of action potentials along motor neurons
36
Describe appendicular attachment in relation to stride sequence **in quadrupeds**
- one or more limbs have to be lifted off the ground for locomotion to occur
- can cause instability - important that centre of gravity maintained within triangle of support or aligns with line of support if 2 limbs are simultaneously off the ground
37
What happens when an incorrect timing and sequence of action potentials occur along motor neurons?
- will correct sequence of muslce in relation to gait being performed
- incorrect sequence firing in humans affects functionality and efficiency of gait
38
Describe the forefoot
- carpal bones downwards
- includes metacarpals and phalanges
- sometimes referred to as the manus
39
Describe the hindlimb
- from tarsal bones downwards
- includes metatarsals and phalanges
- sometimes referred to as the pes
40
What are the different types of digit evolution?
- plantigrade
- digitigrade
- unguligrade
41
Describe plantigrade digit evolution
- entire foot on ground
- greater forward propulsion from muscles that attach to back of the foot than digitigrade and unguligrade mammals
- humans, bears
42
Describe digitigrade digit evolution
- digits on ground, ankle/wrist raised
- propulsion comes from retraction of whole limb
- extra limb segment - longer distal limbs - longer strides to increase speed
- forward thrust more dependent on proximal limb
- dogs, cats
43
Describe unguligrade digit evolution
- digit tips on ground, cursorial
- extension of limb length exaggerated further
- more limb segments - longer metacarpals
- quicker, more efficient movement
- horses, antelopes
44
Describe scansorial adaptations
- climbing mammals
- - mobile limbs
- capable of pronation or supination
- clavicle stabilizes shoulder
- triangular scapula
45
Describe fossorial mammal adaptations
- specialized digging mammals
- strength of forelimbs rather than speed
- long teres (scapula) and olecranon (ulna) processes
- leads to longer moment arms
- shortened and inflexible manus elements
- mole humerus has large tubercles to support short, bulky muscles
46
Describe natatorial mammal specializations
- similar forelimb specializations to fossorial mammals but hindlimbs also specialized
- elongated manus, esp digits
- shortened femur and long crus (knee to ankle)
- long tibias
- paddle-like pes may be webbed
47
Describe graviportal mammal specializations
- mammals with extremely large body masses
- limb bones have large diameters to support mass
- vertical orientation of ilium of the pelvis
