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Vertebrate Zoology > Mammalian Locomotion > Flashcards

Mammalian Locomotion Flashcards

1
Q

What are the factors for locomotion?

A
  • bipedal/quadrupedal
  • environment & terrain
  • size
  • body plan
  • speed
  • gravity
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2
Q

What is the general function of cylindrical/long bones?

A

adapted to act as levers

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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
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4
Q

Describe flat bones

A
  • many in skull or pelvis
  • offer protection to soft parts
  • provide attachment sites for large muscle masses
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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
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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
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7
Q

What is an example of teh splanchnic skeleton?

A

penis bone in cats

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8
Q

What are the functions of the axial - appendicular skeletons?

A
  • postural control
  • proprioceptive reflex arcs
  • pelvic orientation
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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
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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
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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
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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
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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
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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
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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
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16
Q

Describe the scapular spine

A
  • divides supraspinous and infraspinous fossae
  • bony protrusion that runs down length of scapula
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17
Q

Describe the glenoid fossa

A
  • point of insertion of humerus via humeral head
  • at bottom of scapular
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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
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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
Q

Which 2 types of mammals have developed scapular adaptations?

A
  • cursorial / running mammals
  • fossorial / digging & natatorial / swimming mammals
26
Q

Describe the scapular adaptations of cursorial mammals

A
  • 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
Q

Describe the scapular adaptations in fossorial and natatorial mammals

A
  • 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
Q

Describe the deltoid muscles

A
  • 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
Q

Describe deltoid tuberosity adaptations in antelopes and otters

A
  • 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
Q

What is key to solving the quadruped issue of transferring propulsive forces from hindlimb through to main part of the body?

A
  • joint between pelvis and spine (pelvic girdle)
  • free-ranging movement
  • efficient transfer of propulsive force
31
Q

What does the rigidity of spine determine?

A

forms of gallop: transverse or rotatory

32
Q

Describe a rotatory gallop

A
  • placement of second hindfoot followed by ipsilateral forefoot
  • sequence of footfalls appears to rotate around body
  • faster than transverse
  • more rigid body
33
Q

Describe transverse gallop

A
  • two hindfeet placed in sequence
  • placement of second hindfoot followed by contralateral forefoot and then by remaining forefoot
34
Q

What are the most important biomechanical determinants of gallop type?

A
  • body mass
  • relative length of limb segments
  • aspect ratio - body height/body length
35
Q

Describe appendicular attachment in relation to stride sequence

A
  • 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
Q

Describe appendicular attachment in relation to stride sequence in quadrupeds

A
  • 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
Q

What happens when an incorrect timing and sequence of action potentials occur along motor neurons?

A
  • will correct sequence of muslce in relation to gait being performed
  • incorrect sequence firing in humans affects functionality and efficiency of gait
38
Q

Describe the forefoot

A
  • carpal bones downwards
  • includes metacarpals and phalanges
  • sometimes referred to as the manus
39
Q

Describe the hindlimb

A
  • from tarsal bones downwards
  • includes metatarsals and phalanges
  • sometimes referred to as the pes
40
Q

What are the different types of digit evolution?

A
  • plantigrade
  • digitigrade
  • unguligrade
41
Q

Describe plantigrade digit evolution

A
  • entire foot on ground
  • greater forward propulsion from muscles that attach to back of the foot than digitigrade and unguligrade mammals
  • humans, bears
42
Q

Describe digitigrade digit evolution

A
  • 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
Q

Describe unguligrade digit evolution

A
  • digit tips on ground, cursorial
  • extension of limb length exaggerated further
  • more limb segments - longer metacarpals
  • quicker, more efficient movement
  • horses, antelopes
44
Q

Describe scansorial adaptations

A
  • climbing mammals
    • mobile limbs
  • capable of pronation or supination
  • clavicle stabilizes shoulder
  • triangular scapula
45
Q

Describe fossorial mammal adaptations

A
  • 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
Q

Describe natatorial mammal specializations

A
  • 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
Q

Describe graviportal mammal specializations

A
  • mammals with extremely large body masses
  • limb bones have large diameters to support mass
  • vertical orientation of ilium of the pelvis

Vertebrate Zoology (25 decks)

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