Central Nervous System Flashcards
What are the divisions of the whole brain?
Forebrain, midbrain, hindbrain
What are the divisions of the forebrain?
Cerebrum and diencephalon
Which is the largest area of the brain?
Cerebrum
What are the two cerebral hemispheres separated by?
Longitudinal fissure
What are the two cerebral hemispheres connected by?
Corpus callousum
What function is the cerebrum involved in?
Conscious thought processes and intellectual function,
memory storage, processing and retrieval
conscious and subconscious regulation of skeletal muscle contraction
Where is the diencephalon found?
Very deep in the brain
What does the diencephalon consist of?
Dorsal thalamus and the ventral hypothalamus
What is the function of the dorsal thalamus?
Relay and processing centre
What is the ventral hypothalamus involved in?
Hormone production and emotional control
What are the regions of the hindbrain?
Pons, medulla oblongata and cerebellum
What is the function of the cerebellum?
Coordinated complex somatic motor patterns, maintains balance and refines learned movement patterns
What is the cortex made of?
Grey matter
What are the raised bits of the cortex called?
Gyri
What are the fissures in the Cortex called?
Sulci
What is the function of the gyri and sulci?
Increase brain surface area and subdivide it into lobes
What lobes does the central sulcus separate?
Frontal and parietal
What lobes does the lateral sulcus separate?
Frontal, parietal and temporal
What lobes does the parietooccipital sulcus separate?
Parietal and occipital
What is directly anterior to the central sulcus?
Prefrontal gyrus - primary motor area
What does the primary motor area control?
Voluntary movement
What is directly posterior to the central sulcus?
Primary sensory area - located on the post-central gyrus
What does the primary sensory area do?
Receives and interprets sensations
What is directly inferior to the lateral sulcus?
Primary auditory area- on the superior temporal gyrus
What is the primary auditory area involved in?
Reception and interpretation of sound
What is the posterior section of the superior temporal gyrus called?
Wernickes area
What is wernicke’s area involved in?
Comprehension of speech
What is directly superior to the lateral sulcus?
Broca’s area (motor speech area)
What does Broca’s area do?
Movements involved in speech
Where is the primary visual area located?
Posterior pole of the occipital lobe
What does the brainstem contain?
Medulla oblongata, pons and midbrain
Which part of the brainstem is continuous with the spinal cord?
Medulla oblongata
What connects the cerebellum and cerebrum?
Pons
What acts as a conduit between the forebrain and cerebellum?
Midbrain
What is the arterial supply of the brain?
Two internal carotid arteries, two vertebral arteries and the circle of Willis
What is the path of the internal carotid arteries?
Leave neck passing into cranial area through the carotid canal
Passes upwards and forwards into the cavernous venous sinus
Passes lateral to the optic chiasm
What is the path of the vertebral arteries?
Ascend through the foramen in the transverse process of the upper six cervical vertebrae
Enters cranial cavity through the foramen magnum and join together to form the basilar artery
Where do the internal carotid arteries and vertebral arteries anastomose and what do they form?
Inferior surface of the brain to form the circle of Willis
What does the circle of Willis encircle?
Optic chiasm
What does the circle of Willis provide?
Collateral blood flow between anterior and posterior brain that provides alternate blood flow to the hemispheres
Why is the circle of willis important?
Prevents brain ischaemia
What does ‘autoregulation of cerebral blood flow’ mean?
The ability of the brain to maintain relatively constant blood flow
Why is the brains blood flow auto regulated?
Need for constant blood flow and water homeostasis
What do reductions in cerebral blood flow stimulate?
Release of vasoactive substances from the brain that cause arterial dilation
What do cerebral smooth muscle in arterioles constrict in response to?
Elevated pressure
What are the two main causes of a stroke?
Ischaemia and haemorrhage
What causes brain ischaemia?
Blood supply blocked due to a blood clot
What causes a brain haemorrhage?
Weakened blood vessel supplying the brain bursting
What happens if there’s a stroke in the anterior cerebral bit of the brain?
Affects the primary motor cortex for lower limb and perineum of the contralateral side
What does a blockage in the middle cerebral bit of brain lead to?
Loss of sensation and motor function everywhere but the lower limbs and perineum
What does a blockage in the posterior cerebral bit of the brain lead to?
Visual field defects and memory loss
What are the bits of cranial meninges?
Dura, arachnoid and pia mater
What are the two layers of the dura mater called?
Endosteal (or periosteal) and meningeal
Where is the periosteal layer of the dura mater?
Covers the skull
What is the periosteum made of?
A dense layer of vascular connective tissue enveloping the bones except at the surfaces of joints
What does the meningeal layer cover?
Brain
Where/ what is the cranial dura mater continuous with?
Through the foramen magnum with the dura mater of the spinal cord
What do the septa of the cranial dura mater do?
Divide the cranial cavity into freely communicating spaces
What are the functions of the cranial dura mater septa?
Contain the brain subdivisions and restrict rotary brain displacement
What are the reflections of the dura mater?
Falx cerebri Falx cerebelli Tentorium cerebelli Tentorial notch Diaphragma sellae
Where does the Falx cerebri lie?
Midline between the two cerebral hemispheres
Where is the falx cerebelli?
Projects forward between the cerebellar hemispheres
Where is the tentorium cerebelli?
Over posterior cranial fossa,
upper surface of cerebellum
Supports the occipital lobes of cerebral hemispheres
What does the diaphragm sellae allow?
Passage of the infundibulum
Where are the venous sinuses found?
Between the periosteal and meningeal layers of dura mater
What do the venous sinuses join together to form?
Internal jugular vein
Where do the venous sinuses receive tributaries from?
Brain, skull bones, orbit and internal ear
What are the three intracranial haemorrhages?
Extradural, subdural and subarachnoid
What are intracranial haemorrhages the result of?
Trauma or cerebral vascular lesions
Where are extradural intracranial haemorrhages?
Between the periosteal and meningeal dura mater
What is a subdural intracranial haemorrhage?
Buildup of blood between the dura mater and subarachnoid mater
What are subdural haemorrhages caused by?
A tearing of veins as they enter the superior saggital sinus
What are subarachnoid haemorrhages caused by?
Leakage or rupture of the circle of Willis
What happens if you have a subarachnoid haemorrhage?
Severe headache -> loss of consciousness
How do you diagnose a subarachnoid haemorrhage?
Withdrawing heavily bloodstained CSF through a lumbar puncture
What is the central canal?
CSF filled central passageway that extends along the spinal cord and brain
What are the functions of CSF?
Brain cushion,
buoyancy,
suitable environment for correct brain function
transport for nutrients and waste
What is CSF?
Clear colourless fluid
What forms the CSF?
Chorioid plexus
Where does CSF circulate through?
Ventricular system
How does CSF enter the bloodstream?
Passing through the arachnoid into the venous sinuses
What is hydrocephalus?
Accumulation of CSF
What causes hydrocephalus?
Either overproduction of CSF or blockage of the ventricular system
What happens in a neonatal skull with hydrocephalus?
Increased pressure forces unfused cranial bones apart, leading to cranial abnormalities as well as neurological complications
What happens in a fused adult skull with hydrocephalus?
Leads to a dangerous rise in intracranial pressure
What can you treat hydrocephalus with?
A shunt that drains CSF from the ventricular system into a body cavity where it can be reabsorbed
Which cranial nerves arise from the cerebrum?
Olfactory (I) and optic (II)
Which cranial nerves arise from the pons?
Abducens (VI), facial (VII) and vestibulocochlear (VIII)
Which cranial nerves arise from the medulla oblongata?
Glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII)
Which cranial nerves arise from the midbrain?
Trochlear (IV)
Which cranial nerves arise from the junction between the midbrain and pons?
oculomotor (III)
Where do the olfactory bulb and tract lie within?
The anterior cranial cortex
What contains olfactory receptors?
Epithelial within the nasal cavity
Which of the cranial nerves is surrounded by cranial meninges?
Optic nerve
Which cranial nerves exit the skull through the jugular foramen?
Vagus, glossopharyngeal and accessory
Which is the longest cranial nerve in the body?
Vagus
What does the vagus nerve innervate?
Skin of external acoustic Meatus, internal surfaces of laryngopharynx and larynx
