Nervous 2 Flashcards
What are the meninges
The membranes that surround the brain and spinal cord
What are the three layers of the meninges
- Dura mater - tough outer for protection & support, attaching to cranium & periosteum & sacrum
- Arachnoid mater - collagen & elastic fibres, subdural space filled with interstitial fluid
- Pia mater - very thin layer containing blood vessels
What are the bridging veins of the skull
Layers of the dura mater of the meninges that creates venous sinuses aka repetitive ‘bridging’ appearance
Allows blood to drain out of the brain into the jugular veins
Where is cerebrospinal fluid found
Between the pia mater & arachnoid mater is the sub-arachnoid space is filled with the fluid
Ventricles of the brain & central canal of the spinal cord
What is a subdural haematoma
Venous bleed (from venous sinuses damage) - Slowly developing as low pressure system
More likely in alzheimers as shrinkage creates tension
What is a subarachnoid haemorrhage
Arterial bleed - rapid onset
“thunderclap headache”
Usually berry anuerysm associated
What is CSF
Made from filtered blood & mostly water with ions & glucose (colourless as blood cells are too large to filter through)
Ependymal cells produce at a rate of 500ml/day - brain can only contain about 150ml
Functions of CSF
- supports & protects acting as a shock absorber
- maintains uniform pressure around the brain
- moistens
- circulates nutrients (oxygen, glucose, ions) & wastes
- optimal chemical environment for nerve signalling ie ions
What are the choroid plexi
A cluster of ependymal cells & network of capillaries found in the walls of ventricles
Produce csf & introduce via capillaries nutrients needed
What 2 arteries deliver blood to the brain
Vertebral & carotid
Brain uses 20% of bodys oxygen & glucose at rest - neurons die within minutes of being deprived of oxygen
What is the blood brain barrier
Protects the brain from toxins, harmful substances & bacteria that enter the bloodstream by Astrocytes maintaining tightness of the capillaries & junctions between cells
What substances can travel through the BBB
- lipid soluble substances cross easily eg alcohol, anaesthetics
- water soluble, usually just water which hydrates csf
- glucose crosses by active transport
- gases diffuse easily eg O2 CO2
- ions diffuse slowly across
What cant travel through the BBB
Larger molecules
Blood cells, proteins, certain drugs
What are the 4 main regions of the brain
- Brainstem - divided into medulla oblongatta, pons & midbrain
- Diancephalon - thalamus, hypothalamus & epithalamus
- Cerebrum - sensory, motor outputs
- Cerebellum ‘little brain’
What is the foramen magnum
Hole that enters cranium, separates spinal cord (a continuation of) into the brainstem
Functions of the medulla oblongata
~ Contains respiratory & cardiac centres (regulating heartbeat & breathing)
~ Controls reflexes such as vomiting, sneezing & hicupping
~ contains four cranial nerves (9-12)
~ contains motor tracts (corticospinal)
What is the name of the motor tract found in the brainstem
Corticospinal tract - leading down out of brain
Functions of the pons
Helps control breathing
Four pairs of cranial nerves (5-8)
Relays motor tracts
Functions of the midbrain of the brainstem
- contains the substantia nigra (contains neuromelanin which causes pigmentation) dopamine releaisng neuronz that help control subconscious muscle activities
- eye reflexes & tracking
- 2 cranial nerves (3&4) ^
- auditory tracts
- movement of head & neck
- transfers motor tracts
Functions of thalamus
Core of the brain making up 80% of the diencephalon
‘Major relay centre’ to the cerebrum
Integrate sensory & motor info
Functions of the epithalamus
Contains pineal gland which secretes melatonin
Connects limbic system to other parts of the hrain
Functions of the hypothalamus
Hormone regulation & homeostasis
Receives sensory info (ie viscera & smell)
Controls the ANS
Controls body temp
Regulates emotional & behavioural patterns (limbic) , eating & drinking & regulation of circadian rhythms
Functions of the cerebellum
Proprioception
Maintains posture & balance
Coordinates Skilled movements
Correction of errors during movement eg learning bike/instrument
Also thought role in cognition & language
Alters motor behaviour by altering circuits eg muscles
1/2 brains total neuron content - 50 billion
What can impact/damage cerebellum
Alcohol
Coeliac disease
Thiamine (vitamin B1) deficiency
What is ataxia
Imbalance - lack of muscle coordination
Stumbling, unsteadiness, slurred speech, intention tremor (hand tremor)
Common signs of cerebellar disease
Functions of the cerebrum
Sensory perception
Motor control of skeletal muscles
Contains grey matter & white matter
Two hemispheres - left & right
What connects the left & right hemispheres of the cerebrum
The corpus callosum
What is the corticospinal tract
Motor neuron axons join and the tracts cross over ‘decussates’ in the medulla oblongatta
Hemispheres control opposite sides of the body
Frontal lobe fx
Motor skills
Motor cortex
Temporal lobe fx
Hearing
Parietal lobe fx
Sensory cortex
Occipital lobe fx
Vision
Optical nerve has to travel all way to back of brain hence used for observing brain function, if something is damaged
What is the limbic system
Formed of interconnected structures including parts of the cerebrum, diancephalon & midbrain + hypothalamus, hippocampus & amygdala
Becomes active when dealing with emotional responses to our environments
How much cardiac output does the brain receive
20% of body’s cardiac output (around 750ml a minute)
The brain has a very limited ability to store oxygen or glucose, therefore a constant supply is necessary
Thus cardiovasc health important for brain health
What is the circle of willis
Where the two arterial systems (2 carotid from front & 2 vertebral from back) that supply the brain meet
A common location for aneurysms to develop “berry” = subarachnoid haemorrhage
First sensory cranial nerves
1 olfactory - unmyelinated
2 optic
cranial nerves involved in eyes
2 optic - sensory (densely myelinated)
3 oculomotor - 4 out of 6 eye muscles
4 trochlear, rotates eyes
6 abducens, abducts eyeball
Trigeminal nerve fx
Facial sensations- mastication
3 branches
Opthalmic = over eyes
Maxillary = across cheeks & nose
Mandibular = around jaw
Vestibulocochlear cranial nerve fx
Hearing & balance in ears
Glossopharyngeal nerve fx
Taste, swallowing, tongue sensation
Vagus nerve fx
“Wandering nerve” extensive length, largest nerve
ALL Sensory INFO in chest & abdomen (heart, GI, lungs)
In the Parasympathetic ns
Lowers blood pressure, heart rate
Increase digestive motility
Accessory nerve fx
Sternocleidomastoid & trapezius movement
Hypoglossal nerve fx
Tongue movement & speech (underneath)
Damage to any optic nerves can cause
Strabismus (one eye crossed)
Ptosis (drooping of upper eyelid)
Diplopia (double vision)
Injury to vagus nerve can cause
Tachycardia, dysphagia
Vaso-vagal (fainting) - syncope = hyperstimulated nerve drops blood pressure
What area does the spinal cord begin
Foramen magnum
What is the cauda equina
Consists of spinal nerves that continue beyond the conus where the cord terminates (at L2)
Which spinal tracts involve motor impulses
Descending tracts, sent out via anterior VENTRAL horn
Involves voluntary & involuntary movement
Coordination, posture, balance
What spinal tracts involve sensory info
Transmit impulses from skin, tendons, muscles & joints
Touch, vibration, proprioception
Received via posterior DORSAL horn
What are the two sensory ascending spinal tracts
Both ascending
- Dorsal columns = light touch, vibration, proprioception
- Spinothalamic tract = pain & temperature
What is the corricospinal tract
One motor tract of brain, descending
Involved with voluntary movements
What is a reflex arc
A fast, automatic, unplanned sequence of actiond that occurs in response to a stimulus
What are vertebral foramina
Holes in the vertebra where spinal nerves exit the vertebral column
What is hydrocephalus
Excess csf causing brain swelling - raised intracranial pressure
What is meningitis
Meningeal inflammation causing brain swelling & raised pressure
What is encephalitis
Inflammation of brain tissue causing brain swelling & raised pressure
What is papiloedema
Bulging of the optic disc - seen only with opthalmoscopy - sign of raised intracranial pressure
Key sign of raised intracranial pressure
Vomiting often without nausea prior
Due to medulla being pushed into foramen magnum
Most common causes of meningitis
Viral (90%) eg herpes simplex
Bacterial
Immuno-compromised eg elderly, HIV
Brain tumour
(Typically lasts 4-72hrs)
Photophobia
Strong sensitivity to light
Strong sign of meningitis alongside other symptoms
Petechiae, non-blanching
Small purple/red spots on the skin as a result of tiny haemorrhages
Non-blanching = not disappearing with a finger/glass
Key sign of bacterial meningitis
What is kernigs sign
Pain & resistance to knee extension when laying with hips fully flexed
Sign of meningitis
What is brudzinskis sign
Neck flexion upon lying causes flexion of hip & knee
Sign of meningitis
What are antipyretics
Lowers body temp
Used for meningitis
What is a cerebral contusion
Bruise
Traumatic brain injury causing bruising of the brain with ruptured vessels & oedema
What is a coup
Injury to the site of impact of head
What is a contracoup
Damage to the brain at a site contra-lateral to the site of trauma
The skull acts to stop acceleration of the brain away from the site of impact, causing damage on opposite side
What can an absent knee jerk/ankle jerk indicate
Either normal or
peripheral nerve damage/compression/sciatica
Disc herniation
Hypothyroidism
What is babinskis sign
A cutaneous reflex where sole of the foot is stroked upwards
If toes fan out this is positive & indicates corticospinal tract damage such as MS or Motor Neuron Disease
(Normal reaction in infants up to 2yrs)
What is a cervicogenic headache
Originates from the neck, pain radiates from the back of the head
What is a TMJ headache
Tempera-mandibular joint headache
Stress-related ie cleched jaw
Grinding teeth can indicate parasitic infection
What is a cluster headache
Extremely painful caused by facial pain of trigeminal nerve
Aka suicide headache
Headache red flags
— Uncharacteristic & first onset over 50 yrs
— “Thunderclap” headache
— Non-blanching rash, positive kernig/brudzinski sign = meningitis
— worsening morning headache, uneven pupils, double/tunnel vision, papilloedema, vomiting with no nausea = raised intracranial pressure
What is epilepsy
Sudden, hyper-excitable & uncontrolled neuronal activity in the brain
Symptom of a disease, most commonly triggered by hypoglycaemia/calcaemia
Petit mal epilepsy
Non-convulsive
Lasts 10-30 secs “day dreaming child at school”
Grand mal epilepsy
Convulsive ‘tonic clonic’
Tonic = contraction of all muscles which can cause fall
Clonic = rapid contraction & relaxation of muscles causing convulsions
What is spina bifida
‘Occulta’ / ‘cystica’
Embryological disease, usually b12 deficient
Incomplete closure of the spinal column around the spinal cord, most common at lumbosacral junction
Either ‘occulta’ = overlying skin intact
‘Cystica’ = visible cystic mass
What is the straight leg test indicative of
Sciatic/herniated disc
Pain felt up to 45 degrees of raising someones leg whilst lying down
What is aspartame
An artificial sweetener that is a documented neurotoxic
Can cause weight gain instead of loss
Linked to widespread neurological damage & variety of symptoms/conditions including MS, Parkinsons, balance problems etc
What neurological examinations can assess function
— signs eg tremor, rigidity
— motor testing
— cranial nerve exam
— dorsal columns test: light touch, vibration, proprioception/balance
— spinothalamic tract: pin prick, temperature
— gait analysis (walking) & rombergs (proprioception)
— cutaneous & deep tendon reflexes
What is rombergs test
Assesses proprioception
Stand feet together (indicates good cerebellar function if possible)
Upon closing eyes if patient sways indicates positive sign = damage of dorsal columns in spinal cord (often b12 deficient)
