brainstem

Question 1

what are the parts of the brainstem

Answer 1

• mid brain
• pons
• medulla

Question 2

what does the brainstem originate from

Answer 2

• the midbrain and parts of the hindbrain
• it is originally the neural tube which then develops into the hindbrain

Question 3

what are the functions of the brainstem

Answer 3

• 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

Question 4

how does the motor pathway work

Answer 4

• 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

Question 5

how does the sensory pathway work

Answer 5

• it detects sensations through the peripheries and travels the through the pain pathway up the spinal column and to the brain

Question 6

what does the spinothalamic pathway detect

Answer 6

• pain
• crude touch
• temperature

Question 7

what does the dorsal column detect

Answer 7

• fine touch
• vibration
• proprioception

Question 8

how does the ventilation feedback regulation work

Answer 8

1. decrease in pO2, increase pCO2 and decrease pH in plasma
2. activation of peripheral chemoreceptors
3. increase frequency of AP in afferent neurones
4. medullary respiratory centre - causes an activation of VRG + DRG
5. increase AP firing frequency along somatic nerves to skeletal muscles of ventilation
6. primary and secondary respiratory muscles
7. causes an increase in depth of breathing which increase the ventilation rate

Question 9

how does the baroreflex control the heart and vessels?

Answer 9

• 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

Question 10

what does an increase of NTS firing cause

Answer 10

• decrease cardio-acceleratory area
• decrease vasomotor area
• increase cardioinhibitory area

Question 11

how do vital reflexes control breathing

Answer 11

• through rhythmic control and chemoreceptor reflexes
• an increase in CO2, pH and O2 triggers the brain to breath more

Question 12

how does CO2 control breathing

Answer 12

• 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

Question 13

what structures are involved in the control of breathing

Answer 13

• ventral respiratory group neurones
• dorsal respiratory group
• apneustic centre
• pneumotaxic centre

Question 14

how is the ventral respiration group involved in breathing

Answer 14

• located in the medulla
• where the pacemaker cells are for breathing

Question 15

how is the dorsal respiratory group involved in breathing

Answer 15

• stimulates inspiration
• this is done through electrode stimulation makes you want to inspire

Question 16

how is the apneustic centre involved in breathing

Answer 16

• it increases the speed of the respiration cycle through the driving of inhalation

Question 17

hoe is the pneumotaxic centre involved in breathing

Answer 17

• this inhibits the apneustic centre

Question 18

what is the reflex circuit for swallowing and the gag reflex

Answer 18

• 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

Question 19

how does the reflex circuit control coughing

Answer 19

• 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

Question 20

how does the reflex circuit cause salivation

Answer 20

• taste from the CNs
• this then triggers the nucleus tractus solitarius
• this stimulate the the salivatory nuclei
• then triggering the salivary gland

Question 21

what are the sensors that control balance

Answer 21

• eyes (40% of balance)
• vestibular
• proprioceptors
• skin (touch)

Question 22

how does the vestibular system control balance

Answer 22

it detects the forces at work around us

Question 23

how do proprioceptors control balance

Answer 23

it tells you what forces are going through you

Question 24

how does skin control balance

Answer 24

it tells you where your weight is and what is underneath you

Question 25

what are the effectors that control your balance

Answer 25

the skeletal muscles

Question 26

how do skeletal muscles control your balance

Answer 26

they help you maintain balance through movement

Question 27

where is the central processing of balance

Answer 27

- in the cerebellum as this is where sensory information gets processed - also occurs in the vestibular nuclei (the medulla and pons)

Question 28

what is the function of the reticular formation

Answer 28

- 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)

Question 29

how does consciousness work (summary)

Answer 29

- 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)

Question 30

what is affected when there is damage to your reticular formation

Answer 30

- awareness - attention - alertness - sleep - levels of consciousness

Question 31

what are the motor roles of the brainstem

Answer 31

- conduit - motor pathways - balance circuitry - substantia nigra (motor modulation in the mid brain)

Question 32

what are the own motor pathways of the brainstem

Answer 32

- balance motor pathway - head and eye movement - arm flexion

Question 33

what does decorticate mean

Answer 33

- 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

Question 34

what does decerebrate mean

Answer 34

when there is damage between the red nucleus and the inferior olivary nucleus causing extending outwards motion