Block 5 - Musculoskeletal and Nervous System 1 Flashcards
What are the 3 phases of the stance phase?
How much of the gait cycle does it make up?
heel-strike (heel hits ground)
Mid-stance (full foot on ground)
Propulsion (only toe is remaining)
60%
What are the 3 stages of the swing phase?
How much of the gait cycle does it make up?
Toe off, limb swing, heel strike
40%
What is the difference between stride and step?
Stride: Length between one foot and the same foot hitting the ground
Step: Length between one foot and the opposite foot hitting the ground
What is the ratio of tendon to muscle and what does this help with?
Tendons are long compared to muscles
Help with running
What do muscles attach?
Stable bones to moveable bones
Define TORQUE
The rotional force when skeletal muscles contract bones around a joint
What are the 4 types of muscles?
Agonists and Antagonists: Opposing movement
Synergist: 2 different positions but both muscles are agonists
Concentric: Muscle shortens and pulls the bone via the tendon
Eccentric: Muscle length increases (e.g. kicking)
What is the muscle lever arm?
What does the distance of it determine?
What is increased if the distance is longer?
What is increased if the distance is shorter?
Perpendicular distance from the line of muscle action to the joint
The distance determines the muscle’s ability to transfer force
Longer = increased power
Shorter = increased speed
What does balance involve?
Coordinating muscle systems
What is the role of the cerebellum?
To adjust movement based on sensory and proprioceptive input
What is the size of the downward force a product of?
Mass and gravity
Where is the centre of mass in a human?
Pelvis
Mid-anterior to the second sarcal vertebrae
What are the main muscles that work during the stance phase?
Heel strike: Dorsiflexion in the ankle, hip extensors lower the foot and intrinsic muscles preserve the arch to transfer weight
Mid-stance and Propulsion : Hip abductors stabilise the pelvis, knee extensors stabilise the knee and intrinsic foot muscles increase stability
What are the main muscles that work during the swing phase?
Toe off: Eccentric contraction of the hip, big toe flexes increasing stability
Initial swing: Ankle dorsiflexors clear the foot and move the leg
Terminal swing: Hip extensors and knee flexors decelerate the leg, ankle dorsiflexors position the foot and knee extensors straighten the leg
How do heels and flip-flops affect the gait cycle?
Heels: Shortened Achilles tendon and calf muscles
Flip-Flops: Shorter steps and stride length
What happens to your muscles as you get older?
Decreased muscle bulk and flexibility
What happens during Antalgic Gait?
Example
Decreased use of the affected limb causes a decreased stance and swing phase and an increased step length
e.g. stone in your shoe
What happens during Ataxic Gait?
What is another name for it?
Example
Decreased cerebellar activity causes uncoordinated movement with a wide base and double tap of the heel
Cerebellar gait
Multiple Sclerosis
What happens during Parkinsonian Gait?
Short, accelerating steps on tiptoes
Trunk and legs flexed stiffly at the hips and knees
What happens during Myopathic Gait?
What is another name for it?
Example
Weak pelvic muscles cause decreased stability and the pelvis tilts to the non-weight bearing leg
Waddling gait
Muscular diseases
What happens during Neuropathic Gait?
What is another name for it?
Example
Weak dorsiflexors lead to increased stepping to avoid toe dragging
High-Stepping Gait
Peripheral nerve disease
What happens during Trendelenberg Gait?
Dislocation/hip paralysis stops the hip abductors from working.
The pelvis drops as the good limb enters swing phase so the lumbar spine flexes towards the paralysed side to bring the centre of gravity onto the damaged limb
What happens during ‘Footballer’s Favourite’?
Deceleration on an extended knee tears the ANTERIOR CRUCIATE ligament
What happens during Coxa VERA?
What type of gait does it cause?
Decreased angle of the femoral neck leads to shortening of the abductors and lower limb
‘Duck waddle gait’
What happens during Coxa VALGA?
Example
Increased angle of the femoral neck by abductor weakness and decrease in normal weight bearing
Cerebral Palsy
What happens during pes planus?
The arch in the foot collapses leading to increased weight bearing
Two ways in which the pelvis adapted for bipedalism?
The pelvis is more wide than high which brings the sarcoiliac joint closer to the hip joint to decrease weight from the vertebrae
The iliac bone is curved to make the hip muscles abuctors
How is the ‘locking mechanism’ of the knee established?
When the quadricep muscles contract, the femur rotates which compacts the joint
The anterior cruciate and collateral ligaments are elongated and tensed
What does the bi-condyle angle of the femur do?
What else increases support of the leg?
Ensure that the weight is shifted inferior to the trunk and the centre of mass is moved to the midline
The femur head is also a lot larger
What stops the trunk from rotating backwards at the hip joint?
How is weight and centre of mass balanced over the lower limbs
Tension in the inferomordial ligament
The cervical and lumbar curves of the vertebrae cancel out
What adaptation for bipedalism do the feet have?
What three things does this do?
A 2 part longitudinal arch (medial and lateral)
Distribute and transfer weight, act as a shock absorber
What three signals does the skeleton receive for development?
Genetic, functional and loading (environmental) signals
What forms the skull, spinal cord and body
Three separate things!
Skull: Neural crest
Spinal cord: Neural folds
Body: Mesoderm
What parts of the body are formed in cartilage and what parts are formed in neural membrane?
Cartilage: Body, cranial base and nasal septum
Neural membrane: Spinal cord
What does the vertebrae develop from?
Somites
Where do the limb buds grow from?
Apical external ridge
What genes code for the bones?
HOX Genes
What kind of growth does cartilage carry out?
Interstitial growth
Where is bone produced first?
Central shaft and ends
What is found in the epiphyseal growth plate?
Ossification sensors
What is hyaline cartilage made from?
Chondrocyte cells
Intercellular matrix made from fibres and a ground substance containing electrolytes and proteins
What is cartilage laid down by?
Chondroblasts
How does cartilage grow?
Cartilage cells expand which give rise to new flat cells underneath which then also expand
How can you tell there is NOT a fracture?
An unbroken light line around the bone
What are the four parts of the bone?
Ephiphysis –> Physis –> Metaphysis –> Diaphysis
What is another word for spongy bone?
Cancellous
What is the dense outer cortex made from?
What system does it make?
A series of layers (lamellae) which surround blood vessels
A tubular system called an Osteon/Haversian system
What surrounds the lamellae?
Collagen fibres, cells, minerals
Osteocytes are found between the lamellae in holes called lacunae
What is special about the ground structure of bone?
It is mineralised
What 2 things does trabecula resist?
Compression and bending
What makes up the central part of bone?
Marrow
3 causes of osteoporosis?
Under-loaded bone
Under-maintained bone
Too much bone is removed
What are the stages of repairing a fracture?
What two words describe the process of repairing a fracture?
Haematoma: Clotting after the break
Proliferation: Mineralising cartilage formed
Callus: Woven bone produced
Cosolidation: New bone made by osteoblasts
Remodelling
A continuous healing process
What are the 3 main types of joints?
Fibrous joints (Synarthroses) e.g. long bone and sutures Cartinaginous joints (Ampiarthrosis) e.g. ribs, sternum, epiphyseal plate Synovial joints (Diarthroses) e.g. knee
What is a synovial joint made from?
2 long bones with hyaline cartilage in a joint capsule lined with synovial membrane (connective tissue) which secretes fluid for lubrication
The surface is made from flattened cells which become more rounded as you reach the bone
What causes osteoarthritis?
Tearing of the surface layer of cartilage means forces are distributed differently and there is more bone on bone interaction
Define ‘the nervous system’
What is it made from?
The system of cells, tissues and organs that regulate responses to internal and external stimuli
Made from interconnected neurones
Which division of the autonomic nervous system creates memories?
Sensory
What is found between the cell body and axon?
Axon hillock
What are the 4 types of neurones?
Unipolar: Cell body one end and terminal branches the other
Multipolar: Same as unipolar but with many dendrites off the cell body
Bipolar: Cell body in the middle; terminal branches one end and receptor at the other
Pseudounipolar: Cell body off a branch in the middle; terminal branches one end and receptor at the other
What is grey and white matter?
Where is it found in the brain, spinal cord and brainstem?
Grey: Contains cell bodies
White: Contains axons
BRAIN: Grey outside, white inside
SPINAL CORD: Grey inside, white outside
BRAINSTEM: No distinction
What are ganglia?
What do you call ganglia found in the brain?
Bundles of axons which contain cell bodies
Basogalglia
What is grey and white matter made up from in the CNS?
Grey: Cortex and nuclei
White: Tracts
What does dorsal and ventral mean in the brain?
Ventral: Inferior
Dorsal: Superior
What are the 5 layers of a nerve?
Nerve –> Epineurium –> Perineurium –> Fascicle –> Endoneurium
What is Aphasia?
Can’t grasp sensory information
What is Hemianopia?
Loss of vision in one eye
State the progression of nerves from the spinal cord
Dorsal and ventral rootlets –> spinal nerve (in intervertebral foramen) –> dorsal and ventral rami –> plexuses
What property can the nerves in plexuses have distal to the spinal cord?
Sensory and motor functions
What do the dorsal rami supply?
A small area on the back either side of the vertebral column
What is a dermatome and myotome supplied by?
A single spinal SEGMENT
What is heiplegia?
Half body paralysis
What is neglect?
Forget one half of the body
What is the somite?
Specialised areas of mesoderm found either side of the neural tube (musculoskeletal structures)
What is the notocord?
A tube of tissue found beneath the neural tube which is a precursor to the vertebral column
Where do neural crest cells come from? Where do they migrate? What do they form? What do they form in the cranium? What do they form in the trunk?
Cells from the neural folds which migrate to the endoderm forming the 4th germ layer
CRANIUM: Bone, cartilage, connective tissue and ganglia
Migrate to the pharyngeal arches (each contain bone muscle, blood supply and cranial nerve)
TRUNK: Endocrine connective tissue, glia, pigment cells and sensory nerves
What does the neural tube split into near the brain?
Forebrain: Splits into Diencephalon (thalamus and ganglia) and Telencephalon (cerebral hemispheres)
Midbrain: Brainstem
Hindbrain: Brainstem
Where is the thalamus found?
Inside the basal ganglia
What are the three parts of the caudate nucleus?
Where is it found?
Head, body and tail
Runs in a semi-circle around the outside of the basal ganglia along the edge of the lateral ventricle
What is the fornix and hippocampus involved in?
What shape is it and where does it run?
Memory
C-shaped semi-circle which runs in the margin of the lateral ventricle
What is the embryonic precursor for the:
Posterior horn
Anterior horn
White matter
Posterior horn: Alar plates
Anterior horn: Basal plates
White matter: Roof and floor plate
Are anterior or posterior horns motor or sensory?
Where do the nerves grow from for each of these regions?
Anterior: MOTOR –> nerves grow out from cell bodies in the spinal cord
Posterior: SENSORY –> nerves grow into the spinal cord from neural crest cells
Which cranial nerves are:
Extensions of the brain
Pure motor nerves
Mixed nerves - what do these supply
Extensions of the brain: Olfactory and Optic
Pure motor nerves: Oculomotor, Trochlear, Abducens and Hypoglossal
Mixed nerves - Pharangeal arches (1: Trigeminal, 2:Facial, 3: Glossopharyngeal, 4: Vagus)
What percentage of the bone is organic and what percentage is inorganic?
What are the main components of the organic and inorganic part?
Organic: 40% –> Type 1 collagen and non-collagenous proteins
Inorganic: 60% –> Minerals
Where does bone remodelling occur?
In resorption pits between the matrix and marrow in trabeculae bone
What is the role of an osteoblast?
Lay down bone and form the matrix (type 1 collagen)
Vesicles enter the matrix for mineralisation
What is the role of an osteocyte?
Maintain bone by burying into it and extending cytoplasmic extensions that detect chemical changes
What is the role of an osteoclast?
What is its structure?
Binds to the matrix by adhesion molecules
Destroys bone by HCl (inorganic) and phagocytosis (organic)
MULTI-nucleated macrophage
What is the cycle of bone remodelling?
Quiescence: No activity Resorption: Osteoclast activity Reversal: Stem cells --> osteoblasts Formation: New bone Mineralisation: Mineralised bone
How much Calcium is in the body?
What percentage is found in the skeleton?
How is it transported in the blood?
1000g
99% in skeleton and 1% elsewhere
Ionised, Protein bound (albumin) or Complexed (to citrate or phosphate)
How much Phosphorus is in the body?
What percentage is found in the skeleton?
How is it transported in the blood?
How are the levels regulated?
600g
85% in skeleton and 15% elsewhere
Ionised, Protein bound or Complexed (Na, Ca, Mg)
Regulated by PTH
How is Vitamin D synthesised?
How can it be absorbed straight into the body?
In the skin from 7-dehydrocholesterol by UV light
Injestion
How is Vitamin D activated?
Hydroxylation (adding OH) by the enzyme 25-hydroxylase
Liver: D3 + OH –> 25(OH)D3
Kidney: 25(OH)D3 + OH –> 1,25(OH)D3
What increases and decreases the levels of activate D3?
What does the active form of D3 do?
Increases: PTH
Decreases: Ca and P
Active: Increase Ca and P absorption from the intestine and increases osteoclast activity
What is the negative feedback mechanism used to prevent Vitamin D toxicity?
In the kidney:
25(OH)D3 + OH –> 24,25(OH)D3
When and where is the Parathyroid Hormone secreted?
What is its role?
How does it do this? (5)
Secreted by the parathyroid gland when Ca levels decrease. It’s role is to increase them by:
Increasing osteoclasts, decreasing osteoblasts, decreasing excretion, increasing absorption and increasing Vitamin D
What is PTHrP?
What is it produced for?
Parathyroid Hormone Related Protein
Local bone development
When and where is Calcitonin produced?
What is its role?
How does it do this?
Secreted by Parafollicular cells in the thyroid when Ca levels increase. Its role is to decrease them by:
Decreasing osteclasts, increasing osteoblasts and decreasing Vitamin D
What are the two sex hormones involved in bone remodelling?
What do they both do and how?
Oestrogen and Androgen
Decrease osteoclasts and increase osteoblasts to maintain bone mass and density
What are 5 causes of hypercalcaemia?
Primary hyperparathyroidism, Hyperthyroidism, Increased Vitamin D, Malignancy, Immobilisation
What is the cause of Primary Hyperparathyroidism?
What are 5 symptoms?
Increased secretion of PTH by a tumour
Osteitis Fibrosa (Increased bone loss leads to replacement of bone with fibrous tissue) Deformity (in extremities), erosion, fracture, pain,
What are 3 causes of hypocalcaemia?
Renal failure, decrease in Vitamin D and an immature thyroid
What is another word for rickets?
What actually is it?
What are 6 causes?
What are 3 symptoms?
Osteomalacia
Increase in non-mineralised bone
CAUSES: Anticonvulsants, Decreased sunlight, Hydroxylase deficiency, Malabsorption, Renal disease, Vitamin D deficiency/resistance,
SYMPTOMS: Pain, weakness, bowing in long bones
5 drugs used to treat Osteoporosis
Calcium supplements Hormone replacement Bisphosphates Calcitonin Oestrogen Receptor Modulators
Where does the spinal column run from?
How long is it?
From the foramen magnum to L1/L2
42-45cm
What are the 5 sections of the spinal cord?
Cervical, Thoracic, Lumbar, Sarcal and Coccygeal
What order do the meningeal coverings go in?
(CNS) Pia, Arachnoid, Dura (OUTSIDE)
What is the difference between the space in the skull vs the space in the spinal cord?
What are the 2 spaces called?
Skull: A potential space called the Extradural space
Spinal cord: An actual space called the Subarachnoid space
Define spinal segment
Bit of spinal cord bounded by the rootlets of a single spinal nerve
What part of the spinal cord is sensory and what part is motor?
VENTRAL: Motor
DORSAL: Sensory
What is the dorsal root ganglion made from?
Cell bodies
What vertebral level does the spinal cord end at?
What is it called?
L1/L2
Condus Medullaris
What is the cistern?
What is the clinical significance of it?
A subarachnoid space with no spinal cord but spinal fluid
Lumbar Puncture
What is funiculi?
White matter divided into columns (tracts)
Define commissure
Fibres which cross the midline
Where do 1st order neurons run from and to?
What type of neuron are they?
Where are the cell bodies found?
Receptor –> dorsal route of spinal nerves
Pseudounipolar
Cell bodies i dorsal root ganglion
Where do 2nd order neurons run from and to?
What do they do?
Spinal cord –> Thalamus
They decussate
Where do 3rd order neurons run from and to?
Thalamus –> Cerebral cortex
What is the internal capsule?
A white matter tract near the thalamus that fibres pass through
What is the medial lemniscus?
A bundle of tracts which cross the midline
What is the fasciculus graclis and fasciculus cuneatus?
Where do they synapse?
Fasciculus Graclis: Medial fibre which supply’s the lower body
Fasciculus Cuneatus: Medial fibre which supply’s the upper body
SYNAPSE: Cuneate/Gracilus nucleus
What type of neurone is in the DCMLP?
What is this pathway involved in?
1st order
2 point discrimination, pressure, vibration and proprioception
Where does the neurone decussate in the spinothalamic tract?
What type of neurone is it?
What does it form at the brainstem?
Dorsolateral fassiculus (of Lissauer) 2nd order Brainstem = forms the spinal lemniscus
What is the anterior spinothalamic path involved in?
What is the lateral spinothalamic path involved in?
Anterior: Crude and localised touch
Lateral: Pain and temperature
What are secondary collateral neurones?
Neurones which project information to other parts of the brain
What are the 2 conscious perception tracts?
DCLM
Spinothalamic
What are the 4 unconscious perception tracts?
Spino-cerebellar
Spino-olivary
Spino-tectal
Spino-reticular
Where does the spinocerelellar tract run from and to?
What type of information does it pick up?
Spinal cord –> Cerebellum (ipsilaterally)
Internal information
Where does the spino-olivary tract run to?
What is it involved in?
Runs to the accessory olivary nuclei and cerebellum
Co-ordination and balance
Where does the spino-tectal tract run to?
What is it involved in?
Runs to the superior colliculi in the tectum
Reflex turning of the head to cuneatus stimuli
Where does the spino-reticular tract run to?
What is it involved in?
Runs to the reticular activating system
Arousing conciousness through cuneatus stimulation
What is somatotropic arrangement?
The organisation of axons in tracts
Medial = lower
Lateral = higher
What happens in Brown Sequard Syndrome?
Ipsilateral and contralateal symptoms
Lesion in one half of the spinal cord
Ipsilateral: Paralysis and loss of proprioception
Contralateral: Loss of pain and temperature
Define action potential
How long does it take to reach the end of the neurone?
A rapid change in electrical potential across the plasma membrane of the cell
A few milliseconds
Three things which can generate action potentials?
Neurones, muscles and hormones
Where do signals arrive at an axon?
Dendrites
What type of response is there at the axon hillock?
An all or nothing response
The threshold must be reached
Define membrane potential
The difference in electrical potential between the interior and exterior of a cell caused by a separation of electrical charge
How is a resting potential established?
By an electrochemical gradient
When do ligand gated ion channels open?
In response to a drug
How does the sodium potassium pump work?
3 Na OUT
2 K IN
When is equilibrium reached in a neurone?
When there is an electrochemical balance between electrical and chemical forces
What is the equilibrium potential?
What does it depend on?
What is it predicted by?
Equilibrium Potential: The voltage when an ion’s net flow across a membrane is zero
Depends on: Charge and concentration gradient
Predicted by: NERNST EQUATION
What is the equilirbium potential of potassium and sodium as worked out by the Nernst equation?
Potassium: -80mV
Sodium: +60mV
What is a positive equilibrium potential caused by?
Increased potassium on the outside
What is the threshold during an action potential?
-55mV
What is the relative refractory peroid?
An action potential can still be made but only if there is a very large stimulus
Define subthreshold
Magnitude of a graded response (below 55mV)
Define suprathreshold
Frequency of action potentials (more than 55mV)
What is the Goldmann equation?
What value does it give in a neurone?
Resting membrane potential = 61log (permeability of each ion out/permeability of each ion in added together)
= -70mV
What does sodium cause at the axon hillock?
Local depolarisation
What attacks the myelin sheath in MS?
Where?
What are 3 symptoms in the axons?
T cells
Brain, spinal cord and optic nerve
Inflammation, lesions and scarring
Define pain
A unpleasant sensory and emotional experience associated with actual/potential tissue damage.
It is subjective
Define nociception
What can you sometimes feel pain without?
The neural process of detecting, encoding and processing unpleasant stimuli
Physiological
You can feel pain without tissue damage
What 2 things does pain stop during sleep?
Stops the formation of bed-sores
Stops skeletal strain
What are the two types of somatic pain
Superficial and deep
Characteristics of superficial, deep and visceral pain?
Superficial: Sharp, brief, localised, on the skin
Deep: In between the two
Visceral: Dull, aching, burning, poorly localised, internal
3 examples of chronic pain
4 examples of acute pain
Chronic pain: Inflammation, headache, musculoskeletal
Acute pain: Burns, cuts, muscle/ligament damage
Where are nociceptive sensors found?
In internal and external body tissues
5 examples of nociceptors
Thermal Mechanical: Pressure Chemical: e.g. spicy food Polymodal: Most pain receptors Sleeping: Inflammation
What are the two divisions of afferent fibres?
What types of receptors are in each division?
What are the fibres in each division called?
Rapid conduction: Low threshold mechanoreceptors (Alpha A and Alpha B)
Slow conduction: Thermo and nociceptors (Alpha D and C)
What are the fibres and receptors for 1st and 2nd pain?
1st: Thermal and mechanical (Ad)
2nd: Polymodal (C)
What are transient receptor potentials
Proteins on a neurone that open in repsonse to certain stimuli
What do pain neurones synapse with in the spinal cord
2nd order neurones in the lamina of the dorsal horn
How does congential analgesia occur?
What can they feel?
Mutations in genes which code for nociceptor sodium ion channels
Sensory receptors
What happens in dissociated sensory loss?
Diminished sensory stimuli on one side and diminished pain on the other
How is the spinothalamic pathway involved in pain?
Thalamus –> medulla = Perception
Somatosensory cortex = localisation
Limbic system = emotion
How do small diameter afferents get to the brainstem?
How do they cross the medulla?
What tract do they use to enter the thalamus and cortex?
They descend in the spinal-trigeminal tract and go to the brainstem
They cross in the pars caudalis in the medulla
Enter the thalamus via the trigeminothalamic tract
Enter the cortex via the ventral posteromedial nucleus
How do impulses enter the pons from the face?
Cranial nerves 5,7,9 and 10
What neurones are involved in the gate theory?
How are they activated?
What does this lead to?
Localised inhibitory interneurones in the spinal cord activated by touching Ab and C fibres leads to reduced action potentials
What is the difference between physiological and pathological pain?
Physiological: Painful stimuli activate C fibres causing acute pain and non-painful stimuli activate Ab fibres causing no pain
Pathological: Painful stimuli activate C fibres causing Hyperalgesia and non-painful stimuli activate Ab fibres causing Allodynia
What fibres become more sensitive in hyperalgesia?
How does sensitisation occur?
C fibres
Surrounding areas can be affected too due to inflammation
6 symptoms of fibromalgia
How is it diagnosed and treated?
Fatigue, headache, insomnia, irritable bowel, muscle stiffness, restless legs
Diagnosis: Identifying tender points
Treatment: Analgesics and antidepressants
What happens during neurosurgery to help pain?
Physically break the nociceptive pathway
Where do descending pathways in the brain arise from?
What do these pathways do in regards to pain?
The periaqueductal grey matter (PAG) and raphe nuclei
They decrease transmitter release from nociceptors by interacting with opioid receptors
What is the brainstem made from?
Midbrain, pons and medulla oblongata
What is found behind the brainstem?
Cerebral peduncles and interpenducular fossa
What are peduncles?
What is found between the cerebral peduncles?
Tracts that link to the cerebellum
Pair of superior and inferior colliculi between the peduncles
What are the nuclei of the cranial nerves?
Forebrain: 1 2
Midbrain: 3 4
Pons: 5 6 7 8
Medulla: 9 10 11 12
Where do the cranial nerve nuclei exit?
Ventral surface of the midbrain
4 = dorsal
Where are nuclei for the peripheral nerves?
Forebrain
Where do UMN and LMN tracts originate?
UMN: Cerebral cortex, cerebellum or brainstem
LMN: Brainstem or spinal cord
What do the basal ganglia, thalamus, cerebellum and pons form?
Descending pathways and feedback loops
Where is the basal ganglia nuclei?
What function do they therefore have?
In the grey matter - a motor function
What are the 2 descending tracts called?
Dorsolateral
Ventromedial
Ventromedial tracts:
What part of the white matter are the tracts in? Where do they synapse? What movements are they involved in? Ipsilateral or contralateral? What does injury lead to?
Ventral and medial aspects of white matter
Ventral and medial anterior horn cells
Flexors and extensors of the thigh, arm and trunk
Involved in posture and moving multiple joint
Bilateral movements (both sides through one neurone)
Ipsilateral
Injury = loss of posture, a slump but maintains fine motor movements
Dorsolateral tracts:
What part of the white matter are the tracts in? Where do they synapse? What movements are they involved in? Ipsilateral or contralateral? What does injury lead to?
Dorsal and lateral aspects of white matter
Dorsal and lateral anterior horn cells
Flexors and extensors below the elbow and knee
Act on single joints
Contralateral
Injury = normal posture and navigation but loss of fine motor movements
What are examples of ventromedial tracts?
Reticulospinal
Tectospinal
Vestibulospinal
What are examples of dorsolateral tracts?
Ruberospinal
Corticospinal
What are the two limbs of the internal capsule and what are they separated by?
Which limb does the corticospinal tract pass through?
Anterior and posterior
Genu
Posterior
4 symptoms which occur when tracts are lost?
Paralysis, hyper-reflexia, hypertonia and Babinski
Define ‘Brainstem Death’
Irreversible loss of capacity for consciousness and breathing
What cranial nerve does each reflex test test for?
Pupillary light reflex: 2+3 Cotton wool in eye: 5+7 Vesibulo-occular reflex (turning head and eyes): 3,4,6+8 Gag reflex: 5+7 Cough reflex: 10
Which cranial nerves do not have their nuclei in the brainstem?
1 and 2
What are the three movements?
Reflex, rhythmic, voluntary
6 examples of reflexes
Spinal, posture, balance, innate movements, learned movements, goal-directed movements
3 characteristics of the alpha motor neurone
Wide axons, myelinated, long
Where can motor neurones receive information from?
Muscle spindles (1a afferents) Golgi and tendon organs (1b afferents) Cutaneous skin receptors Spinal interneurones Upper motor neurones
What neurone degenerates in motor neurone disease?
Alpha motor neurone
5 symptoms of motor neurone disease
3 things that are unaffected
Muscle weakness, atrophy, twitching, difficulty breathing and swallowing
Cognitive, eyes and sensory
When do extrafusal muscle fibres contract?
What do they contain?
Contract when the alpha motor neurone signals
Contain muscle spindles
Where are intrafusal muscle fibres found?
What do they detect?
Inside muscle spindles parallel to the extrafusal fibres
They detect the amount and rate of muscle length change
What does the 1a afferent neurone provide information about?
Spindle stretch
What is the muscle spindle?
What neurones innervate it?
A fibrous capsule found in muscle fibres
1a sensory and gamma motor neurones
2 roles of the gamma motor neurone
What is it co-activated with?
Regulates the sensitivity of sensory afferents to stretch and intrafusal muscle contraction
Readjusts and maintains the tautness of the muscle spindle length
Always co-activated with alpha
Explain the knee jerk reflex:
Type of reflex
What is activated
Flexors vs extensors
Agonist vs Antagonist
A stretch reflex
Patellar tendon –> stretch quadriceps + activate 1a muscle spindle
If the flexors are excited then the extensors are inhibited causing movement
AGONIST: Contracted by the reflex
ANTAGONIST: Inhibitory interneurone inhibits hamstring movement
Where is the Golgi tendon organ?
What does it run parallel to?
What is it innervated by?
How is it activated?
In the junction between the muscle and the tendon
Runs parallel to the extrafusal fibres
Innervated by the 1b afferent
Increased tension in collagen fibres –> compression of sensory receptors and increase in 1b activity –> decrease in alpha motor neurone activity
How does the flexor withdrawal reflex work?
Step on something sharp
Nociceptive cutaneous receptors –> afferent –> inter –> alpha motor
Hamstring flex to pull leg away
AND Quadriceps flex on the other leg to extend the knee and balance
What are central pattern generators?
What is the purpose of them?
Neural networks in the brain and spinal cord
Allow you to automatically carry out OSCILLATORY (repetitive) movements (e.g. walking) without sensory feedback
What are the 3 layers of the muscle outer layer?
Which layer has the muscle fasicle and which has myosin and actin filaments?
Epimysium
Perimysium (Muscle Fascile)
Endomysium (Myosin and Actin)
What are the 3 bands of muscle?
What do the words isotropic and anisotropic mean?
I band: Actin only (isotropic)
A band: Actin and Myosin (anisotropic)
H band: Myosin only
How are the ends of actin anchored to the z line?
By the enzyme alpha actinin
Where are satellite cells found?
Between the basement membrane and sarcolemma
What two types of chains is myosin made from?
Light and heavy
What 3 things is an actin molecule made from?
Tropomyosin regulatory proteins
Myosin binding site
Troponin complex
When is the maximum tension in a muscle?
When the muscle is at rest
What does the force of contraction depend on?
What is it proportional to?
Depends on the degree of overlap
Proportional to the muscle fibre length
What receptors are found at the NMJ in skeletal muscle?
Nicotinic cholinergic receptors
What is the muscle end plate potential?
How is an action potential always made?
-90mV
Many neurotransmitters
What is the sarcolemma in direct contact with?
The extracellular fluid
What forms a triad in the muscles?
T tubules surrounded by sarcoplasmic reticulum with a terminal cisternae on either side
When does Rigor Mortis end?
When proteolytic lysosomal enzymes released by autolysis digest the decomposing cells
How long does Rigor Mortis last for?
2-3 hours
Can be 24 hours
3 ways that Calcium is taken back into the sarcoplasmic reticulum after muscle contraction
SERCA pump on Sarcoplasmic Reticulum (ATP)
Na-Ca exchanged
Ca pump
How is calcium stored in the sarcoplasmic reticulum?
Calsequestrin and Calreticulin
How is Calcium released from the sarcoplasmic reticulum?
Type-L calcium channels open (Dihydropyradine)
These link to ryadonine receptors releasing calcium from the sarcoplasmic reticulum
What are the 3 phases of muscle twitch?
- Lag phase: Time is taken for cross bridge formation
- Contraction: Increased tension
- Relaxation: Decreased tension
What is a motor unit?
The motor nerve and muscle fibres which it innervates
What are the 4 types of muscle twitch?
Single muscle twitch: Stimulate muscle separately
Temporal summation: Continue to stimulate the muscle before it is relaxed causing an increase in tension every time
Unfused tetanus: Stimulate the muscle at shorter intervals - no overall increase in tension
Fused tetanus: Stimulate at very short intervals - muscle tension increases in a straight line
What is the pre-load determined by?
The initial muscle length
What is isometric contraction?
Example
Stimulate muscle and increase tension but NO muscle shortening
(e.g. pushing a wall)
What is isotonic contraction?
Example
Stimulate muscle and increase tension and the muscle SHORTENS
(e.g. pushing a box)
What are the three muscle fibres?
Slow twitch fibres
Fast twitch fatigue resistant fibres
Fast twitch glycolytic fibres
Slow twitch fibres: High or low oxygen? Do they get fatigued easily? Colour? Myoglobin level? Blood flow? What movements do they allow?
High oxygen Resistant to fatigue Red High myoglobin Increased blood flow Posture
Fast twitch fatigue resistant fibres: High or low oxygen? Myoglobin level? Colour? Do they get fatigued easily?
High oxygen
Resistant to fatigue
Red/pink
Medium myoglobin
Fast twitch glycolytic fibres: Colour? Myoglobin level? Blood flow? Do they get fatigued easily?
White
Decreased myoglobin
Decreased blood flow
Get faigued easily
Defne myopathy
Muscle disease
Define Myostitis
Inflammation in the muscle
What is Muscular Dystrophy?
A inherited and progressive disease
What is Myasthenia?
Increased muscle weakness with exercise
What is Myotonia?
Faliure to relax the muscle?
Which ion channels are affected in channelopathies?
Na, K and Cl
What happens during the disease dystrophonia?
What gender is it more common in and why?
What happens to the muscles?
What is the average life expectancy?
A loose dystrophin complex –> fat deposition in muscles instead of protein deposition
Males (sex linked)
Progressive muscular weakness
Life expectancy = 30
