Lower Limb - Anatomy, Biomechanics, Neural Control of Standing

Question 1

What are the major bone of the trunk connected to the legs?

Answer 1

Ilium (hip Bone)
Pubis

Question 2

What are the major bones in the legs?

Answer 2

femur (thigh)
Patella (knee cap)
Tibia/Fibula (Lower Leg)

Question 3

What are the major bones in the foot?

Answer 3

tarsals (ankle bones - 7)
metatarsals (5)
Phalanges (in toes - 14)

Question 4

What are the bones of the lower limb?

Answer 4

Question 5

Where does the Sacral Plexus arise from?

Answer 5

vertebrae L4-S4

Question 6

Where do the Obturator and Femoral nerves arise from

Answer 6

Vertebrae L2-L4

Question 7

What are the main nerves that are involved in the nervous Innervation of the Leg

Answer 7

Femoral Nerve L1-L4
Sciatic Nerve L5-S3
Common Peroneal Nerve
Tibial Nerve

Question 8

What are the main groups of muscles that move the Thigh?

Answer 8

Gluteal group
Lateral Rotator group
Adductor group
Iliopsoas group

Question 9

What are the Gluteal Muscles and their nerves?

Answer 9

Gluteus Maximus - inferior Gluteal Nerve
Gluteus Medius - Superior Gluteal Nerve
Glutes Minimus - Superior Gluteal Nerve
tensor Fasciate Latae - Superior Gluteal Nerve

Question 10

What are the muscles in the Lateral Rotator Group and their nerves?

Answer 10

Obturator - Branch of Sciatic Plexus
Piriformis - Branch of Sciatic Plexus
Gemelles - branches of Sciatic Plexus
Quadratus Femoris - Branch of Sciatic Plexus

Question 11

What are the muscles and their nerves in the Adductor group?

Answer 11

Adductor Longus - Obturator
Adductor Magnus - Tibial Portion of Sciatic
Adductor Brevis - Obturator
Pectineus - Femoral
Gracilis - Obturator

Question 12

What are the muscles and their nerves of the Iliopsoas group?

Answer 12

Iliacus - femoral
Psoas - femoral

Question 13

What are the flexors of the Knee?

Answer 13

Biceps Femoris - sciatic tibial portion (long head) and Common peroneal of Sciatic ( short head)
Semimbranosus - Sciatic Tibial portion
Semitendinosus - Sciatic Tibial portion
Sartorius - Femoral
Poplitius - tibial nerve

Question 14

What are the extensors of the Knee

Answer 14

Quadriceps
- Rectus Femoris
- Vastus Lateralis
- Vastus Intermedius
- Vastus Medialis

Nerve: Femoral

Question 15

What are the flexors of the ankle?

Answer 15

Tibialis Anterior - Deep Peroneal

Question 16

What are the Extensors of the Ankle

Answer 16

Gastronemius (medial and lateral) - Tibial
Soleus - Tibial
Plantaris - Tibial
Tibialis Posterior - Tibial
Peroneus (Fibularis) brevis - Superficial peroneal
peroneus (Fibularis) longus - Superficial Peroneal

Question 17

What are the flexors of the Toes?

Answer 17

Flexor Digitorum Longus - Tibial
Flexor hallucis Longus - Tibial

Question 18

What are the Extensors at the Toes

Answer 18

Extensor Digitorum Longus - Deep peroneal
Extensor hallucis Longus - Deep peroneal

Question 19

What is needed to maintain an upright position in Humans?

Answer 19

Centre of mass of the body must remain within the confines of the base of support

Question 20

What is the base of support in humans?

Answer 20

The area underneath and between the feet or the feet and cane/crutch

Question 21

What Mechanical principles Affect Stability?

Answer 21

• Ability of the body to maintain stability against disturbing external forces is proportional to the area of the base of support
• Stability is directedly related to horizontal distance of the center of mass from the edge of the base of support
• Stability is inversely related to the height of the Centre of mass above the base of support
• stability is proportional to the weight of the body

Question 22

What is the centre of pressure?

Answer 22

the location of the vertical ground reaction force which is equal and opposite to a weighted average of the locations of all downward acting forces (weight of the body and the inertial effect of body movement)

Question 23

Why does the location of the Center of pressure changes?

Answer 23

Center of pressure location changes according to CofM movement and distribution of muscle forces required to control or produce that movement

Question 24

Why are humans generally less stable than Quadripeds?

Answer 24

2/3rd of the mass of the body is located at 2/3rds of the body height above the ground and this makes up more unstable

Question 25

What does the inverted pendulum model tell us for sway angle of more than 8 degrees?

Answer 25

The model predicts that the difference between the CofP and CofM is proportional to the horizontal acceleration of the CofM

Question 26

Formula for the inverted pendulum model

Answer 26

CoP – CoM = -Ix/Wd = -Kx
I = Moment of inertia of the total
body about the ankle in the direction
of interest
x = Horizontal acceleration of the
CoM in the direction of interest
d = Vertical distance from the ankle
joints to the CoM
W = Total body weigh above the
ankle joints

Question 27

What are the afferent Systems involved in balance stability?

Answer 27

visual
vestibular
proprioceptive

Question 28

What pathways make of the medial system?

Answer 28

Reticulo-spinal
vestibulo-spinal

Question 29

What is the purpose of the medial system?

Answer 29

This system is involved in controlling posture

Question 30

What are the two parts of the Reticulospinal Tract?

Answer 30

Medial
- arises in Pons
- responsible for extensor tone (decerebrate Rigidity)
Lateral
- arises in Medulla
- more involved in muscle movement

Question 31

What is Decerebrate Rigidity

Answer 31

Decerebrate rigidity is a condition that occurs when there is damage to the brain, specifically to certain areas that control movement and coordination. This damage leads to increased muscle stiffness and a specific posture where the limbs are extended and rigid. It’s a neurological response indicating a lack of normal inhibitory control over muscle tone.

Question 32

What is Inhibitory Descending Drive

Answer 32

The brain has a system that sends signals (or “drive”) to control and inhibit certain activities in the spinal cord. This control is important for maintaining balanced and coordinated movements.

Question 33

What is Reticular Formation

Answer 33

The reticular formation is a part of the brainstem that plays a crucial role in regulating various bodily functions, including consciousness, arousal, and motor control.

Question 34

What are Descending Noradrenergic and Serotonergic Neuromodulatory Axonal Projections

Answer 34

refers to nerve pathways that carry signals using neurotransmitters like noradrenaline (noradrenergic) and serotonin (serotonergic). These pathways start in the brain (from the nuclei) and travel down (descending) to the spinal cord. They act as modulators, influencing and adjusting the activity of other nerve cells in the spinal cord.

Question 35

What are Excitatory Neuromodulatory Axonal Projections

Answer 35

The signals carried by these pathways are “excitatory,” meaning they increase the activity of the nerve cells they interact with. In the context of motor control, this increased activity can enhance the transmission of signals that lead to muscle contractions and movement.

Question 36

What is the difference between Decerebrate and Decorticate Postures?

Answer 36

Decerebrate posture result from damage to the upper brainstem. The arms are adducted and extended, with the wrist pronated and the fingers flexed. the legs are stiffly extended with plantar flexion of the feet

Decorticate posture results from damage to one of both corticospinal tracts. the arms are adducted and flexed, with the wrist and gingers flexed on the chest. the legs are stiffly extended and internally rotated, with plantar flexion of the fee

Question 37

What are the components of the Vestibulospinal pathway

Answer 37

Vestibular Apparatus (Inner Ear)
is comprised on two Otoliths
(gravity sensing) and three
semi-circular canals (rotational
acceleration sensing)

Question 38

What is the purpose of the parts of the vestibulospinal pathway components

Answer 38

lateral tract - involved in stabilization of body
medial tract - involved in stabilization of head

Question 39

What is the vestibulocercical Reflex

Answer 39

-Involved in stabilization of head on body. Uses Medial Vestibulospinal pathway.
- When the head rotates or tilts in one direction, contract neck muscles to oppose
the motion.
- Also, biomechanical components of the head have a characteristic resonance frequency of 2-3 Hz which oscillation would likely occur and this reflex will help dampen

Question 40

What is the vestibulospinal Reflex?

Answer 40

• Involved in stabilizing body.
  Uses Lateral Vestibulospinal pathway.
• When body rotates or tilts in
  one direction, contract ipsilateral extensor
  muscles to counteract.

Question 41

Types of Strategies for Postural Control

Answer 41

• Sensory strategies of how the three systems (visual, vestibular
  and proprioceptive) interact and are organized for controlling posture.
  Enviromental conditions can have large effects on type of postural
  strategies used.
• Sensorimotor strategies reflect how the sensory and motor
  systems combine to produce a co-ordinated postural response.
• Attentional strategies determine the degree of attention given
  to a postural task while performing other tasks simultaneously.
  Can be modified depending on the degree of anticipation of upcoming
  disturbances, and on previous postural conditions (postural set)

Question 42

How does the lost of a sensory system affect postural Strategy choice?

Answer 42

Vestibular Loss - tend to rely solely on ankle strategy
People with Distal Neuropathies (loss of sensation from proprioceptors) - tend to rely on hip strategy

Different sensory inputs can weight the type of postural strategy chose