PBL 6 Flashcards
What is the function of the frontal lobe?
movement
decision making
problem solving
planning
What are the three main divisions of the frontal lobes?
- prefrontal cortex
- premotor cortex
- primary motor cortex
What is the function of the prefrontal cortex?
personality expression, planning of complex cognitive behaviours
What is the function of the premotor cortex?
voluntary muscle movement
What is the function of the primary motor cortex?
voluntary muscle movement
motor homunculus
What is the function of the parietal lobe?
processing tactile sensory information such as pressure, touch and pain
Which portion of the brain is involved in processing the body’s senses?
somatosensory cortex
What is the function of the somatosensory cortex?
allows co-ordination of movements in response to the objects in our environment (situational/spatial awareness)
What is the function of the occipital lobe?
main centre for visual processing
Which lobes are involved in visual perception
occipital lobes in addition to posterior portions of the parietal and temporal lobes
What main structure is found within the occipital lobe?
The primary visual cortex
What is the function of the primary visual cortex?
receives visual input from the retina via the optic nerve
these visual signals are interpreted in the occipital lobes
Describe the function of the temporal lobe
organising sensory input, auditory perception, language, and speech production
What structures are found within the temporal lobe?
- limbic system
- olfactory cortex
- amygdala
- hippocampus
what is wernicke’s area?
sensory language understanding, lexical processing (words and sentances)
What symptoms will occur if the wernicke’s area is damaged?
- receptive aphasia and extremely poor comprehension
What is Broca’s area?
motor aspect of speech, damage to this area will result in expressive aphasia, non-fluent and slow speech
What is the primary auditory cortex?
area where processing of auditory (sound) information occurs
What is the basal ganglia
a collection of nuclei that are strongly connected to the cerebrum, brainstem and cerebral cortex
What is the basal ganglia involved in?
influencing motor activity and motor control
What are the three parts of the basal ganglia?
- corpus striatum
- subthalamic nuclei
- substantia nigra
What is the corpus striatum?
structure made up of caudate nucleus, putamen and globus pallidus
What is the subthalamic nuclei?
produces the excitatory neurotransmitter glutamate
what is the substantia nigra?
produces the neurotransmitter dopamine, which is involved in the nigro-striatial pathway
What is the medulla oblongata’s function?
deals with autonomic/involuntary functions
carries out life-sustaining functions:
- breathing
- HR
- BP
- swallowing
What is the function of the pons?
connects the cerebral cortex with the medulla oblongata
serves as a communications and coordinations centre between the two hemispheres of the brain
helps in transferring of messages between various parts of the brain and the spinal cord
What is the function of the thalamus?
- relay station
receives auditory, visual sensory and somatosensory signals and relays them to the cortex
Describe the thalamus
dual lobed mass of gret matter burried under the cerebral cortex
location of the cell bodies of the 3rd order neurones in ascending pathways
Describe the hypothalamus
control centre for many autonomic functions of the PNS
- hunger
- thirst
- body temp maintenance
- homeostasis
- influences the pituitary gland
Describe the cerebellum
controls motor movement coordination, balance, equilibrium and muscle tone
relays information between body muscles and areas of the cerebral cortex that are involved in motor control
Describe the amygdala
almond shaped group of neurons located deep within the medial temporal lobes
What is the role of the amygdala?
primary role in processing and memory of emotional reactions
part of the limbic system that supports emotion, behaviour and long-term memory
What is the role of the hippocampus?
forming, organising and storing memories
limbic system structure involved in forming new memories and connecting emotions and senses (smell and sound) to memories
memory ‘indexer’ - sends memories for long-term storage and retrieves them when necessary
Name the two dural reflexions in the cranial cavity
- tentorium cerebelli
- falx cerebri
Where is the tentorium cerebelli found?
between occipital lobes and cerebellum
Where is the falx cerebri found?
between the cerebral hemispheres in the longitudinal cerebral fissure
What is a primary brain injury?
the result of initial trauma on neural tissue
described as:
- focal
- polar
- diffuse
What are focal injuries?
- injuries localised to the site of impact on the skull
- damage is variable
What symptoms would arise from damage to the motor cortex?
contralateral weakness of the face and arm
What are the symptoms of space occupying lesions?
- raised ICP
- brain shifting
- herniation
What can cause a space ooccupying lesion?
- haematoma
- significant oedema
What are the three main types of haematomas that can occur?
- epidural haematoma
- subdural haematoma
- intracerebral haematoma
Describe an epidural haematoma
collections of blood in the epidural space between the cranium and teh dura mater
How do epidural haematomas occur?
- vessels within the dura susceptible to injury with skull fractures
- fracture of the temporal bone can affect the middle meningeal artery
What is the most common source of epidural haematomas?
arterial source - can expand rapidly
Describe a subdural haematoma
Form in the space between the dura and the arachnoid mater
- stretched and sheared apart
- slower rate of formation
Which vessels are usually affected in subdural haematomas?
bridging veins which drain venous blood from the surface of the brain, coursing the arachnoid and subdural spaces before emptying into the venous sinuses
Describe an intracerebra haematoma
- single or multiple
- commonly in the frontal or temporal lobes
- may occur in association with severe motion or a contusion can coalesce into a haematoma
What are polar injuries?
cerebral contusions that occurs when the brain moves within the cranial cavity causing the brain to be crushed by violent contact with the skull or dura mater
Where are polar injuries found?
occur adjacent to the site of impact (coup lesions) and diagonally opposite (contrecoup lesions)
most common site is the underside of the frontal lobes, inferior aspects of the temporal lobes, the occipital poles and the cerebellum
What is a concussion?
a temporary distrubance in brain function as a result of trauma
What are the symptoms of concussion?
- headache
- dizziness
- memory disturbance
- balance problems
- loss of consciousness
- seizure activity
- poor performance
What are diffuse injuries?
occur when movement of the brain within the cranial cavity causes widespread neuronal damage
What causes diffuse axonal injury?
brain is subjected to shifting and rotational forces during injury
- causes stretching and shearing of axonal white matter
What are the signs of diffuse axonal injury?
- frequently comatose at time of injury
- coma is a consequence of damage in the cerebral cortex
What is a secondary injury?
The development of further neurological damage subsequent to the primary injury
often secondary injuries cause more damage than primary injuries
What are resulting symptoms of secondary brain injury?
- ischaemia
- increased ICP
- altered vascular regulation (hypoxia)
- cerebral sweeping
- infection
How does ischaemia affect the brain?
- failure in supply of energy sources
- neurons have small metabolic reserves and are extremely sensitive to energy deprivation
- failure of energy supply results in death of neurones, with sparing of vessels and support cells which are robust
Which event in ischaemic damage leads to cell death?
-excitotoxicity
activation of glutamate receptors which causes uncontrolled entry of calcium ions into neurons = death
What is intrcranial pressure?
The pressure exerted by the contents of the cranium.
ranges from 0-15mmHg
what components make up the volume of the cranium?
- brain tissue
- CSF
- blood
What is the monro-kellie hypothesis
a description of the compensatory responses to a change in volume by any of the 3 components (compliance)
increase in one can be offset by decreases in the other two
How can blood volume be reduced in the cranium?
- vasoconstriction can reduce blood vessel volume
How can CSF volume be reduced in the cranium?
by moving into the spinal cord from the cranium
How can brain tissue volime be reduced in the cranium?
In young children, head circumference will slightly increase
Name the serious complication that can result from elevated ICP?
compression and herniation
- causes rapid neurological dysfunction
What structures can e affected by a midline shift?
- reticular activating system (RAS) which is necessary for maintaining consciousness, and vital cardiorespiratory centres
How is consciousness clinically assessed?
- Glasgow coma scale (GCS)
- Cranial nerve reflexes
GCS alone in not sufficient
What is consciousness?
A state of alertness and attentiveness to one’s environment and situation
A fully conscious person is awake, alert and orientated to time, person, place and current circumstances
What is the acute management of head injury?
1 - cardiopulmonary stabilisation (ABC, airway vital)
2 - Disability (GCS)
3 - Radiology -
4 - surgical intervention - for depressed skull fractures, bleeding vessels, and haematomas
Management of ICP
What is cerebral perfusion pressure?
the net pressure gradient causing cerebral blood flow to the brain (perfusion)
must be maintained in narrow limits as too little can cause ischaemia and too much can raise ICP
Describe CNS regeneration
adult CNS neurons have limited ability to regenerate in contrast to PNS neurones due to lack of factors that facilitate growth in the cns and to the presence of factors which actively inhibit growth
Describe recovery of function in the CNS
Due to neural plasticity despite limited CNS regeneration
adaption of uninjured tissue to undertake some of the functions of previously subserved tissue which has been irreversibly damaged
Describe neural plasticity
the potential for brain to change its structure and function
What does neural plasticity involve?
- rewiring of existing neurons into new functional networks, and the addition of new formed neurones
What is neural plasticity used for?
to train different areas of the brain to assume new functions
How does neural plasticity occur?
Greater exposure to a particular stimulus prompts the brain to dedicate more neurones to that stimulus (and a lack of stimulation allows the brain to reassign neurones to a different function)
What is the outcome of head injuries?
major causes of morbidity and disability
severe psychosocial factors
What are the possible long-term sequelae of head injury?
- cognitive impairment
- hemiparesis
- epilepsy
- chronic subdural haematoma
- hydrocephalus
- chronic traumatic encephalopathy
