14. Nervous System II Flashcards
What does the CNS consist of?
Brain
Spinal cord
What is the spinal cord protected by?
Vertebral column
Meninges
What are meninges?
Layers of connective tissue
What is the brain protected by?
Cranium
Cranial meninges
Cerebrospinal fluid (CSF)
Blood brain barrier (BBB)
What are the three layers of meninges that cover the brain and spinal cord?
Dura mater
Arachnoid mater
Pia mater
What is the dura mater?
Tough outer layer
What is the dura mater in the brain made up of?
Two layers
What do the two layers of dura mater in the brain do?
Create venous sinuses
What do venous sinuses do?
Allow blood to drain out of the brain into the jugular veins
What is the arachnoid mater made up of?
Collagen and elastic fibres
What is the subdural space between the dura mater and arachnoid mater filled with?
Interstitial fluid
What is the pia mater?
Thin transparent layer
What is the pia mater made up of?
Blood vessels that supply the spinal cord
What is the subarachnoid space between the arachnoid mater and pia mater filled with?
Cerebrospinal fluid (CSF)
What is a subdural haematoma?
Venous bleed in space below the dura mater
Slowly develops
What is a subarachnoid haemorrhage?
Arterial bleed in the space below the arachnoid mater
Rapid development
What is cerebrospinal fluid (CSF)?
Clear liquid that protects the brain and spinal cord from mechanical and immunological injury
What does CSF consist of?
Filtered blood
Water with ions and glucose
Why is CSF colourless?
Blood cells are too large to filter through
Where can you find CSF?
Subarachnoid space
Ventricles in brain
Central canal of spinal cord
What is CSF produced from?
Ependymal cells
How much CSF is produced a day?
500ml
How much CSF can be found in the brain?
150ml
What happens to excess CSF that can’t fill around the brain?
Gradually absorbed back into blood
What are the functions of CSF?
Supports/protects the brain and spinal cord
Shock absorber
Keeps them moist
Circulates nutrients and waste
Maintains uniform pressure around brain
Maintains optimal chemical environment for nerve signalling
Where does blood flow to the brain from?
Vertebral arteries
Carotid arteries
What percentage of the body’s oxygen and glucose does the brain use at rest?
20%
What does the blood brain barrier do?
Protects brain from toxins, harmful substances and bacteria
How does the BBB protect the brain from toxins, harmful substances and bacteria?
Maintaining tightness of capillaries
Maintaining junctions between cells
What maintains the BBB?
Astrocytes
What substances can transport across the BBB?
Lipid soluble substances - alcohol, anaesthetics
Glucose
Gases
Ions
What substances can’t transport across the BBB easily?
Proteins
Some drugs
What are the four areas of the brain?
Brainstem
Diencephalon
Cerebrum
Cerebellum
What are the parts of the brainstem?
Midbrain
Pons
Medulla oblongata
What are the parts of the diencephalon?
Thalamus
Hypothalamus
Epithalamus
Where can you find the brainstem?
Top of the spinal cord
What does the brainstem pass through?
Foramen magnum (large hole)
Which centres are located in the medulla oblongata?
Respiratory
Cardiac
What does the medulla oblongata control?
Vomiting reflex
Coughing reflex
Hiccupping reflex
Which cranial nerves are located in the medulla oblongata?
9-12
Which tract is located in the medulla oblongata?
Corticospinal tract (motor)
What does the pons control?
Breathing
Which cranial nerves are located in the pons?
5-8
Which tract does the pons relay?
Motor
What does the midbrain contain?
Substantia nigra
What is the substantia nigra?
Large, darky-pigmentated area
Contains dopamine releasing hormones
What does the midbrain do?
Controls eye reflexes and tracking
Controls head and neck movements
Which cranial nerves are located in the midbrain?
3-4
Which tract does the midbrain transfer?
Motor
What is the thalamus?
Relay centre of the brain
What percentage of the diencephalon is made up of the thalamus?
80%
What does the thalamus do?
Relays sensory information to the cerebrum
Integrates sensory and motor information
What does the epithalamus do?
Connects limbic system to other parts of the brain
Which gland is located in the epithalamus?
Pineal gland
Which hormone does the pineal gland secrete?
Melatonin
What does the hypothalamus do?
Regulates hormones and homeostasis Controls body temperature Regulates emotional/behavioural patterns Regulates appetite/satiety Regulates circadian rhythm
What type of information does the hypothalamus receive?
Sensory
Which nervous system does the hypothalamus control?
Autonomic nervous system
Where is the cerebellum located?
Inferior and posterior aspect of the cranium
How many neurons can be found in the cerebellum?
50 billion
What are the functions of the cerebellum?
Balance/posture Co-ordinate sequences of movement Correct errors during ongoing movement (learning an instrument, learning to walk) Cognition Thoughts and language processing
What can damage the cerebellum?
Chronic alcohol abuse
Coeliac’s disease
Thiamine (B1) deficiency
What are the symptoms of a cerebellar disease?
Ataxia - lack of muscle co-ordination Stumbling Unsteadiness Slurred speech Intention tremor (tremor when doing a movement e.g. hand shaking when putting key in lock)
What are the areas of the cerebrum called?
Left and right hemispheres
What does the cerebrum contain?
Outer cerebral cortex with multiple foldings
Deeper cerebral region
What is the outer cerebral cortex also known as?
Grey matter
What is the deeper cerebral region also known as?
White matter
What is grey matter made up of?
Cell bodies
Dendrites
Unmyelinated axons
What is white matter made up of?
Myelinated axons
How are the left and right hemispheres of the cerebrum connected?
By the corpus callosum
What does the corpus callosum do?
Co-ordinates movements between sides e.g. walking
What are the functions of the cerebrum?
Sensory perception
Motor control of skeletal muscles
What is the name of the descending motor tract?
Corticospinal tract
What is the corticospinal tract made up of?
Motor neuron axons
Where do the motor tracts cross over (decussate)?
In the medulla oblongata
What impact does the motor tracts decussating have on the body?
Left side of brain co-ordinates right side of body
Right side of brain co-ordinates left side of body
What are the four lobes of the cerebrum called?
- Frontal
- Temporal
- Parietal
- Occipital
What does the frontal lobe of the cerebrum control?
Motor skills
What does the temporal lobe of the cerebrum control?
Hearing
What does the parietal lobe of the cerebrum control?
Sensory cortex
What does the occipital lobe of the cerebrum control?
Vision
What does the outer cerebral cortex contain?
Sensory cortex
Motor cortex
What does the sensory cortex do?
Receives sensory input (e.g. touch, vibration) and maps it out
What does the motor cortex do?
Controls voluntary movements of specific muscles
What is the limbic system?
Area of brain that is active with different emotions
What is the limbic system formed of?
Cerebrum
Diencephalon
Midbrain
What are the key structures within the limbic system?
Hypothalamus
Hippocampus
Amygdala
When does the limbic system become active?
When dealing with emotional responses
What is the key area for emotions?
Amygdala
What does the hippocampus do?
Encode and retrieve memories
What percentage of cardiac output does the brain receive?
20%
How much blood does the brain receive?
750ml every min
What is the Circle of Willis?
Where the carotid and vertebral arterial systems meet
The Circle of Willis is a common location for which pathology?
Berry aneurysm
How many cranial nerves are there?
12
What are the cranial nerves?
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Which cranial nerves are located in the cerebrum?
- Olfactory
2. Optic
Which cranial nerves are located in the midbrain?
- Oculomotor
4. Trochlear
Which cranial nerves are located in the pons?
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
Which cranial nerves are located in the medulla oblongata?
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Mnemonic for remembering the cranial nerves
On, Olfactory On, Optic On, Oculomotor They - Trochlear Travelled - Trigeminal And - Abducens Found - Facial Voldemort - Vestibulocochlear Guarding - Glossopharyngeal Very - Vagus Ancient - Accessory Horcruxes - Hypoglossal
Cranial nerve 1 - name, function, location
Olfactory
Sense of smell
Cerebrum
Cranial nerve 2 - name, function, location
Optic
Vision
Cerebrum
Cranial nerve 3 - name, function, location
Oculomotor
Eye movements, eyelid opening, pupil dilation
Midbrain
Cranial nerve 4 - name, function, location
Trochlear
Eye movements
Midbrain
Cranial nerve 5 - name, function, location
Trigeminal
Facial sensations, chewing, some taste
Pons
Cranial nerve 6 - name, function, location
Abducens
Eye movement (abducts eye)
Pons
Cranial nerve 7 - name, function, location
Facial
Taste, facial expressions, salivary glands
Pons
Cranial nerve 8 - name, function, location
Vestibulocochlear
Hearing, balance
Pons
Cranial nerve 9 - name, function, location
Glossopharyngeal
Taste, swallowing, tongue sensations
Medulla oblongata
Cranial nerve 10 - name, function, location
Vagus
Sensory/motor functions in chest/abdomen
Medulla oblongata
Cranial nerve 11 - name, function, location
Accessory
Neck and shoulder movement
Medulla oblongata
Cranial nerve 12 - name, function, location
Hypoglossal
Tongue movement and speech
Medulla oblongata
How many eye muscles does the oculomotor nerve (3) move?
4 out of 6
How many eye muscles does the trochlear nerve (4) move?
1 out of 6
How many eye muscles does the abducens nerve (6) move?
1 out of 6
What can damage to the oculomotor, trochlear or abducens nerves cause?
Strabismus (squint)
Ptosis (drooping of upper eyelid)
Diplopia (double vision)
What is strabismus?
One eye crossed
What is ptosis?
Drooping of upper eyelid
What is diplopia?
Double vision
What are the branches of the trigeminal nerve (5)?
Ophthalmic
Maxillary
Mandibular
What is the vagus nerve?
Largest nerve of the autonomic nervous system
What information does the vagus nerve carry?
All sensory information from chest and abdomen
What can damage to the vagus nerve cause?
Tachycardia
Dysphagia
Mnemonic for remembering the cranial nerve functions
Some - Sensory Say - Sensory Money - Motor Matters - Motor But - Both My - Motor Brother - Both Says - Sensory Big - Both Brains - Both Matter - Motor More - Motor
Where does the spinal cord begin?
At the foramen magnum
Where does the spinal cord terminate?
At vertebral level 2 (L2)
Where does the spinal cord meninges tissue continue to?
To level S2 of sacrum
What is vertebral level 2 (L2) also known as?
Conus
What is the cauda equina?
Spinal nerves that continue beyond the conus
What does the spinal cord consist of?
White matter around a core of grey matter
What does the spinal cord white matter consist of?
Bundles of myelinated axons - tracts
Which tracts make up the spinal cord white matter?
Motor tracts
Sensory tracts
Which direction does the motor tract of the spinal cord go and what does it do?
Descending
Control voluntary and involuntary movement
Which direction do the sensory tracts of the spinal cord go and what do they do?
Ascending
Transmit impulses from skin, tendons, muscles and joints
What does the spinal cord grey matter consist of?
Cell bodies
Dendrites
How is the spinal cord grey matter divided up?
Posterior (dorsal) horn
Anterior (ventral) horn
What does the posterior (dorsal) horn do?
Receive sensory impulses
What does the anterior (ventral) horn do?
Sends out motor impulses
How is information processed in the spinal cord?
- Information enters the dorsal horn
- It synapses with interneurons and travels up a sensory tract to the thalamus
- Thalamus processes the information and sends it to the sensory cortex
- Sensory cortex sends motor information down the corticospinal tract where it synapses at the level it’s coming out of
- The information then comes out of the ventral horn
What are the spinal cord tracts called?
Dorsal columns
Spinothalamic tract
Corticospinal tract
Which spinal cord tracts are ascending?
Dorsal columns
Spinothalamic tract
Which spinal cord tract is descending?
Corticospinal tract
What information does the dorsal column receive?
Light touch
Vibration
Proprioception
What information does the spinothalamic tract receive?
Pain
Temperature
What information does the corticospinal tract send out?
Voluntary movements
What is a reflex arc?
A fast, automatic and unplanned sequence of actions that occurs in response to a stimulus
What is the spinal reflex?
Integration of a reflex that happens in the spine
What does a reflex arc consist of?
- Sensory receptor
- Sensory neuron
- Interneuron
- Motor neuron
- Effector organ
What are extensions of the spinal cord called?
Spinal nerves
Where do spinal nerves exit the vertebral column?
Through holes in the vertebra called vertebral foramina