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What 3 structures make up the Brain Stem?
- Medulla Oblongata
What is the role of the Midbrain?
Links forebrain to hindbrain
The Substantia Nigra of the Midbrain has what function?
- Connect basal nuclei
- Regulate movement
- (black due to melanin precursor of dopamine)
The Red Nuclei of the Midbrain has what function?
- Relay descending motor pathways
- (red due to blood and iron)
The Corpora Quadrigemina of the Midbrain is split into two different functional groups -
- Superior Colliculi - Vision reflexes
- Inferior Colliculi - Auditory reflexes
The Midbrain's ventral aspect is characterised by what?
Cerebral peduncles which contain large pyrimidal tracts that relay motor signals from the motor cortex to the spine
What is the function of Periaqueductal Grey Matter of the Midbrain?
- Encircles aqueduct linking 3rd and 4th ventricles
- - Pain supression
- - Links Amygdala
- - Autonomic 'fight or flight' pathways
What is the Reticular Activating System?
- RAS - Neurons projecting through medulla, pons and midbrain
- ALL SENSES SYNAPSE TO RAS
- 99% filtered out
- Keeps brain awake - inhibited by Hypothalamus
What is the Pons?
- Origin of CNV CNVI and CNVII
- Conduction tracts
- Contains Pneumotaxic centre
What is the Medulla?
- Contains ALL ascending sensory nerve tracts and ALL descending motor
- Anterior Surface contains Pyramidal tracts
- Control Centre for a lot of Autonomic reflexes
Where are the Chemoreceptors and what do they respond to?
- Central - Medulla, stimulated by H+
- Peripheral - Arteries of neck, CO2 and O2, impulses travel via Vagus (CNX) and Glossopharyngeal (CNIX)
What is the role of the Cardiovascular Centre of the Medulla?
To adjust the force of heart, vessel diameter, blood flow and pressure (vasomotor centre)
The Cardiovascular Centre recieves input from where?
- Preparation for Exercise - Cerebral Cortex, Limbic System, Hypothalamus
- Anatomical Input - Proprioceptors (joints+muscles), Baroreceptors(blood vessel stretch), Chemoreceptors
The Cardiovascular Centre outputs to where?
- Sympathetic - Cardiac accelerator nerves
- - Vasomotor nerves for smooth muscle vasoconstriction
- Parasympathetic - Vagus (CNX)
Explain the process of the Pons and Medullary Deglutition centre
- 1.Bolus of Food voluntarily passes to Oropharynx
- 2. Involuntary: Pharynx signals Deglutition centre in Medulla and Lower Pons
- 3. Returning Impulses cause soft palate and uvula to close of nasopharynx and epiglottis to close off larynx
- 4. Oesophageal sphincter relaxes, bolus moves into oesophagus
Explain the process of the Medullary Vomiting centre
- 1. Stimuli send impulses to medullary vomiting centre
- 2. Co-ordinated motor impulses sent to contract diaphragm and abdominal muscles and relax cardiac sphincter
- 3. Soft palate closes off nasal passages
Explain the process of the Medullary Sneezing Centre and Couging centres
- Sneeze - Stimuli -> medulla ->CNV-> uvula depresses, abdominal muscles contract
- Cough - Stimuli-> medulla -> CNX -> glottis closes, respiratory musculature contracts. Can be cortically controlled
What are the basic concepts of Motor Control?
- Primary Motor Cortex - Conscious initiation
- Actual Control - Cerebellum and Basal Nuclei
What are the 3 sections of the Cerebellum and their associated roles?
- Anterior and Posterior Lobes - Subconscious Body Movement
- Flocculondular Lobe - Vestibular equilibrium and balance
What is the Stretch Reflex?
- Spinal Reflex
- Ensures muscle length
- eg. No knee buckling
What is the Golgi Tendon Reflex?
- Spinal Reflex
- Opposite to Stretch Reflex - relax and lengthen in response to tension
- Allows smoooth muscle action and prevents tears
What is the Flexor or Withdrawal Reflex?
- Spinal Reflex
- Withdrawal from painful stimuli
- Can be cortically overcome
What is the Crossed Extensor Reflex?
- Spinal Reflex
- Accompanies Flexor
- Maintains balance when bearing weight
What are the two Descending Motor Pathways?
- Pyramidal Tracts - Direct and Voluntary
- Extrapyramidal System - Reflexive and indirect, multineuronal
What are the Reticulospinal Tracts?
- Originate Reticular Formation of Pons and Medulla
- - Locomotion of Limbs
- - Postural control
What is an oversimplification of Motor Control?
1. Motor Cortex "what do I want to do?"
2. Precommand Areas Cerebellum and Basal Nuclei
take over and determine timing and patterns
- 3. Via thalamus, returns information to Motor Cortex
- 4. Motor Cortex initiates or terminates action
What would you like to do?
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