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YEAR 1 > Physiology - Spine/Neurones/Pain > Flashcards

Physiology - Spine/Neurones/Pain Flashcards

1
Q

What increases velocity of conduction within neurones?

A

Larger axon diameter
Myelination of axon
Increased temperature

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2
Q

What are the glial cells in the CNS?

A
  • Ependymal cells - facilitate CSF
  • Oligodendrocytes - form myelin sheath around axons
  • Microglial cells - immune cells
  • Astrocytes - form BBB
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3
Q

What are the glial cells in the PNS?

A
  • Schwann cells - form myelin sheath around axons

- Satellite cells - surround cell bodies on sensory neurones

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4
Q

What cells form the myelin sheath around axons in the CNS and PNS?

A

CNS - oligodendrocytes

PNS - schwann cells

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5
Q

What is the process of an action potential?

A

Membrane at resting potential -70mV

Stimulus triggers ligand gated channels to open - sodium ENTERS cell

Membranes reaches -55mV threshold potential and sodium channels open

Sodium rushes IN, causing membrane depolarisation +30/40mV

Potassium channels open and Sodium channels close

Potassium rushes OUT of cell and causes membrane depolarisation

Potassium channels slow to close, membrane hyperpolarisation -90mV

Refractory period - membrane cannot be stimulated, rest period

Potassium channels close, resting membrane potential of -70mV restored

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6
Q

How are chemicals released into the synaptic cleft?

A

Action potential reaches axon terminal

Calcium voltage gated channels open due to presence of AP/Na+

Calcium rushes into cell and vesicles filled with NT move towards membrane

Exocytosis of vesicle which releases neurotransmitter into synaptic cleft

NT attach to and activate chemical gated channels on dendrite of post synaptic dendrite

Sodium rushes in through channels to depolorise the membrane and make an Action Potential

NT recycled back into pre synaptic cleft into vesicles to stop AP and calcium channels close.

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7
Q

What is the anatomical pathway which pain is transmitted along?

A

Inflammatory mediators released locally as a result of injury/inflammation. Produce pain either by direct stimulation or sensitising free nerve endings.

Pain is mediated via the myelinated A-delta (sharp, immediate pain) and non-myelinated C fibres (slower-onset, duller, more diffuse and prolonged pain).

A fibres enter/terminate the dorsal root; synapse with second-order neurones; decussate/send fibres to the contralateral side; travel in spinothalamic tract.

C fibres enter and terminate at the dorsal root; synapse with axons that pass through the anterior commissure to the contralateral side and up the spino-reticulo-thalamic tract.

Then both via thalamic pathways to and from the cortex to register pain and mediate emotional components.

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8
Q

How do inflammatory mediators sensitise nociceptors?

A

Inflammatory mediators bind to free nerve endings and with the presence of calcium causes sensitisation by lowering the threshold of the nociceptor

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9
Q

What is the Pain Gate Control Theory?

A

Activity of mechanoreceptors (Ab fibres) stimulate inhibitory neurones in lamina II to block interneurones to lamina V - thus inhibiting the excitation of the spinothalamic tract - reducing nociceptive activity.

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10
Q

How are descending tracts involved in endogenous pain relieving mechanisms?

A
  1. Na/5-HT released from descending tracts inhibit release of Substance P, inhibiting excitation of transmission neurone
  2. Na/5-HT stimulates interneuron to release opioid peptide - enkephalin, which closes calcium channel to block substance P release - inhibiting excitation of transmission neurone
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11
Q

What is the process of homeostasis in controlling your temperature when its increased?

A

Rise in temperature

Change detected by thermoreceptors in skin and hypothalamus

Send signals to nuclei within hypothalamus, to control centre to reduce temp

Effector cells act - sweat glands, vasodilation, shunt blood to skin

Temperature reduces to norm

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12
Q

What is the pathophysiology of fever?

A

Fever producing stimuli

Recognised by macrophages and T lymphocytes - release cytokines IL-1, IL-6, TNFalpha…

- Activation of immune response
- Acute phase response from the liver
- Breach BBB to reach brain

Brain released PGE2

PGE2 acts on hypothalamus to increase set temperature = FEVER
(Shivers come before the fever, as core temp is below the newly higher set temp.)

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13
Q

What is the process in a stretch reflex/knee jerk/simple reflex arc?

A

Patella tap stretches the muscle - increase in rate of action potentials

Type Ia and II sensory fibres pick up the stretch from the muscle spindle and send signal to the spinal cord into the anterior horn

  1. Type Ia synapses with alpha motor neurone to cause muscle contraction of quads to extend the knee
  2. Type II synapses with an inhibitory interneuron to inhibit alpha motor neurone of hamstrings to allow them to relax and lengthen for extension of the knee

Leg kicks out - involuntary - does not need to go up to the brain

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14
Q

What are muscle spindles?

A

Sensory organs in muscles that sense the changes in the length of the muscle and rate of lengthening.

Ia and II sensory fibres attaches to intramural fibres of muscle spindles

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15
Q

What are Golgi tendon organs?

A

Detect tension in the tendon.

Activated by muscle stretch and contraction to activate Ib sensory fibres

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16
Q

What is the process in inverse myotatic reflex?

A

Muscle contracts which generates tension in the tendon - fires off more action potentials

Tension activates Golgi tendon to activate Ib sensory fibres

Ib fibres transmit signal to dorsal horn where synapses with 2 types of interneurones

  1. Inhibitory interneurone to synapse on alpha neurone to relax contracting muscle
  2. Stimulatory interneurone to synapse with alpha neurone of antagonist muscle to stimulate contraction to release tension off the tendons.
17
Q

What is the process of the withdrawal reflex/crossed extensor reflex?

A

Stimulus activates pain receptors

Leg that feels the pain - reflex to inhibit extensor muscles and stimulate flexor muscle

Opposite leg - reflex stimulates extensor muscle and inhibits extensor muscle

Helps maintain posture and balance

18
Q

What is the central pattern generator?

A

Responsible for locomotion

Neural circuits located in the spinal cord of Inhibitory interneurones between flexor and extensor pools to put together reflexes to be able to walk/run etc

Modulated by proprioception input

19
Q

What muscles are responsible for the swing phase in locomotion?

A

Flexor muscles

20
Q

What muscles are responsible for the stance phase in locomotion?

A

Extensor muscles

21
Q

What are the 4 main structures found in the basal ganglia

A

Neostriatum - caudate and putamen
Globus pallidus
Subthalamic nucleus
Substantial nigra - produce dopamine

22
Q

What is the direct pathway of the basal ganglia?

A

Excitatory - Stimulation of the motor cortex

Pathway:
Substantia nigra release dopamine.
Dopamine acts on D1 receptors in corpus striatum.
Corpus striatum release GABA which inhibits globus pallidus.
(GPi normally release GABA to inhibit thalamus)
Thalamus excited to stimulate cerebral cortex for movement

23
Q

What is the indirect pathway of the basal ganglia?

A

Inhibitory - Suppression of the motor cortex

Pathway:
Substantia nigra release dopamine.
Dopamine acts on D2 receptors in corpus striatum.
Corpus striatum release GABA which inhibits globus pallidus.
(GPe normally release GABA to inhibit STN)
STN release glutamate
Glutamate excites GPi to release GABA
GABA inhibits thalamus

24
Q

What is the main role of the cerebellum?

A

Coordinate muscle movement, maintain posture and balance

25
Q

What are the 3 functional divisions of the cerebellum?

A

Spinocerebellum - limb position, touch and pressure, proprioception, locomotion

Cerebrocerebellum - planning and initiating movement, rapid complex movement , motor learning, coordination of muscles

Vestibulocerebellum - balance, posture and eye movement

26
Q

How does the cerebellum connect to the brainstem?

A

Superior peduncles - cerebellum to midbrain - communicate with motor cortex

Middle peduncles - cerebellum to pons - input from cerebral cortex

Inferior peduncles - cerebellum to medulla - output to upper motor neurones

27
Q

What are the 3 parts of the brainstem?

A

Midbrain - visual system, accommodation, pupillary light reflex, substantially migration

Pons - jaw/jerk, blink, tensor tympani reflex

Medulla oblongata - swallowing and gag reflex, cough and knee reflex, vibration, proprioception

28
Q

Where does reticular formation occur in the brain stem?

A

Pons and Medulla oblongata

29
Q

What descending tracts originate in the brainstem?

A

All except corticospinal tract - originate in motor cortex

30
Q

What are the motor regions of the cerebral cortex?

A

Primary motor cortex - initiates voluntary movement

Supplementary motor cortex - sequences of movement

Premotor cortex - planning of movement

31
Q

What 2 descending tracts does the primary motor cortex send signals down?

A

Corticospinal tract to spinal cord for movement of the body

Corticobulbar tract to brain stem for movement of the head/neck/face

32
Q

What are signs of an upper motor lesion and how does it occur?

A

Damage to brain or spinal cord(white mater)

Causing spasticity…

Minimal or no muscle atrophy
Increased reflexes and spasticity 
Plantar response - dorsiflexion = babinski positive 
Normal coordination
Reduced power
Increased tone
33
Q

What are signs of a lower motor lesion and how does it occur?

A

Injury axons leaving the spinal cord, or spinal cord (grey mater)

Causing flaccidity

Muscle atrophy
Flaccid paralysis - reduced tone and power
Absent tendon reflexes - negative babinski sign
Absent plantar response
Normal coordination

34
Q

What are examples of motor lesion disease?

A

Parkinsons, Huntingtons - Basal ganglia - movement changes

Myopathy, muscular dystrophy - Muscle - muscle weakness, atrophy

Myasthenia gravis - Neuromuscular junction - fatiguable weakness

Multiple sclerosis - Cerebellum - incoordination, decrease in tone

35
Q

What is the descending tract responsible for voluntary movement and what is the pathway?

A

Corticospinal tract - anterior(trunk) and lateral(limbs)

Originates in the cerebral cortex
Descend into the brainstem - cerebral peduncles
Descend into the medulla to form - pyramids of medulla

Anterior tract - remain ipsilateral in the tract until they decussate and terminate in the ventral horn

Lateral tract - decussate to the other side of the CNS in the tract and terminate in the ipsilateral ventral horn

Synapse with lower motor neurones to supply muscles of the body

36
Q

What is the gait cycle?

A

STANCE - single or double contact

  • Heel strike/Initial contact - dorsi flexed - tibialis anterior, gluteus Maximus
  • Foot flat/ Loading response - quads
  • Midstance - gastrocnemius + soleus for knee stability
  • Heel off / Terminal stance - gastrocnemius + soleus

SWING - foot not on the ground

  • Toe off / pre swing - plantar flexed and everted, rectus femurs
  • Midswing - iliopsoas and rectus femoris
  • Terminal swing - quads and hamstrings, tibialis anterior
37
Q

What are the pre-requisites for gait?

A 
Stability in stance
Sufficient foot clearance in swing
Appropriate pre-positioning of foot in swing
Adequate step length
Energy conservation
38
Q

What are different types of abnormal gait?

A 
Short leg
Trendelenberg - OA, perthes, weak glutes
Rigid - OA
Antalgic
Weak - polio, spina bifida, scoliosis 
Spastic - cerebral palsy - scissor
39
Q

What are managements of spastic gait?

A 
Physical therapy 
Muscle relaxants 
Botulinum toxin
Orthotic braces
Surgery

YEAR 1 (17 decks)

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