brainstem Flashcards
what are the parts of the brainstem
- mid brain
- pons
- medulla
what does the brainstem originate from
- the midbrain and parts of the hindbrain
- it is originally the neural tube which then develops into the hindbrain
what are the functions of the brainstem
- conduction pathway for the sensory, motor and autonomic information
- cranial nerve functions: accommodation, corneal, vestibulocochlear
- autonomic circuits
- reflex circuitry: breathing, vasomotor, swallowing, coughing, salivation, vomiting
- balance
- sensory filter
- chemoreceptors
- movement
- pain modulation
how does the motor pathway work
- the corticospinal track help you make the body move (any damage here leads to paralysis)
- the corticobulbar is cranial nerves 3,4,5,6,7,9,10,11,12 - movement can occur due to these nerves
how does the sensory pathway work
- it detects sensations through the peripheries and travels the through the pain pathway up the spinal column and to the brain
what does the spinothalamic pathway detect
- pain
- crude touch
- temperature
what does the dorsal column detect
- fine touch
- vibration
- proprioception
how does the ventilation feedback regulation work
- decrease in pO2, increase pCO2 and decrease pH in plasma
- activation of peripheral chemoreceptors
- increase frequency of AP in afferent neurones
- medullary respiratory centre - causes an activation of VRG + DRG
- increase AP firing frequency along somatic nerves to skeletal muscles of ventilation
- primary and secondary respiratory muscles
- causes an increase in depth of breathing which increase the ventilation rate
how does the baroreflex control the heart and vessels?
- when there is an increase in blood pressure this then cause an increase of them firing
- an increase in baroreceptor firing causes an increase of nucleus tractus solitarius firing (NTS)
- increase in NTS causes vasodilation, causing a decrease in HR, then decreasing the force of contraction
what does an increase of NTS firing cause
- decrease cardio-acceleratory area
- decrease vasomotor area
- increase cardioinhibitory area
how do vital reflexes control breathing
- through rhythmic control and chemoreceptor reflexes
- an increase in CO2, pH and O2 triggers the brain to breath more
how does CO2 control breathing
- high CO2 is a potent driver of respiration so any increase control the chemoreceptor reflex
- this also occurs with a low pH
- if sats are below 60 the brainstem triggers an increase in resp rate
what structures are involved in the control of breathing
- ventral respiratory group neurones
- dorsal respiratory group
- apneustic centre
- pneumotaxic centre
how is the ventral respiration group involved in breathing
- located in the medulla
- where the pacemaker cells are for breathing
how is the dorsal respiratory group involved in breathing
- stimulates inspiration
- this is done through electrode stimulation makes you want to inspire
how is the apneustic centre involved in breathing
- it increases the speed of the respiration cycle through the driving of inhalation
hoe is the pneumotaxic centre involved in breathing
- this inhibits the apneustic centre
what is the reflex circuit for swallowing and the gag reflex
- throat sensation sends a signal from CN9
- this signal is sent into the brainstem
- it then travels through the descending pathway via CN 10 to the stomach
how does the reflex circuit control coughing
- sensors in the lungs detect touch, irritation and inflammation
- this then sends a signal to the brainstem
- the brainstem then triggers the expiratory muscle to cough
- this is done through the phrenic nerve
how does the reflex circuit cause salivation
- taste from the CNs
- this then triggers the nucleus tractus solitarius
- this stimulate the the salivatory nuclei
- then triggering the salivary gland
what are the sensors that control balance
- eyes (40% of balance)
- vestibular
- proprioceptors
- skin (touch)
how does the vestibular system control balance
it detects the forces at work around us
how do proprioceptors control balance
it tells you what forces are going through you
how does skin control balance
it tells you where your weight is and what is underneath you
what are the effectors that control your balance
the skeletal muscles
how do skeletal muscles control your balance
they help you maintain balance through movement
where is the central processing of balance
- in the cerebellum as this is where sensory information gets processed
- also occurs in the vestibular nuclei (the medulla and pons)
what is the function of the reticular formation
- it acts as a gate keeper for infomration
- this changes someone’s conscious levels
- it does this by acting as a filter of what to do (eg sleep)
how does consciousness work (summary)
- it requires a sensory input
- most of this input passes through the brain stem
- the cells are synaptically connected to the ascending tract (the ascending reticular formation)
what is affected when there is damage to your reticular formation
- awareness
- attention
- alertness
- sleep
- levels of consciousness
what are the motor roles of the brainstem
- conduit
- motor pathways
- balance circuitry
- substantia nigra (motor modulation in the mid brain)
what are the own motor pathways of the brainstem
- balance motor pathway
- head and eye movement
- arm flexion
what does decorticate mean
- when no information from the cortex to the body
- leads to tensing in
- if you lose information from the cortex then the red nucleus takes over
- red nucleus is what causes tensing inwards
what does decerebrate mean
when there is damage between the red nucleus and the inferior olivary nucleus causing extending outwards motion
