The Brain (Theme A) Flashcards
Although the relative size of the components of vertebrate brains can vary in size, they all have a common plan - what is this?
Forebrain - Midbrain - Hindbrain (including the cerebellum)
The human forebrain is relatively _______, compared to other vertebrates
Large
What are the 4 components of the brainstem?
- Medulla
- Pons
- Midbrain
- Cerebellum (*which is sometimes considered as separate)
Which 2 components make up the forebrain?
- Telencephalon
- Diencephalon
Why does the human brain have 2 anatomical axis?
Due to the flexure in the brain between the axis (cephalic flexure)
*other vertebrates don’t have such a pronounced flexure
Where are the 2 anatomical axes of the brain?
Axis A - Forebrain
Rostral (forehead side) —> Caudal
Superior / Dorsal (top of head) —> Inferior / Ventral
Axis B - Brainstem, cerebellum, spinal cord
Rostral (top of spine) —> Caudal
Dorsal (back side) —> Ventral (stomach side)
What is the flexure between the 2 anatomical axes of the brain called?
Cephalic flexure
What are the 4 planes of section (of the brain)?
Horizontal - cut horizontally across the head
Sagittal - goes down the midline of the head
Oblique - rarely used
Coronal (transverse) - cut down the head, like ear to ear
*Different to transverse section of the SC, as the axis changes
What does the grey matter contain?
Cell bodies
What does the white matter contain?
Axons
Why is white matter white coloured?
Myelin sheaths of axons - myelin is a pale colour
What are the 3 Brain Meninges? (From outer to inner)
Dura Mater
Arachnoid Mater
Pia Mater
What does the arachnoid mater contain?
CSF
Which of the Meninges is adherent to the surface of the brain?
Pia Mater
Which of the Meninges lines the skull cavity?
Dura Mater
What folds does the Dura Mater form?
- Falx Cerebri
- Tentorium Cerebelli
Where is the falx cerebri?
Fold in the middle of the brain
Where is the tentorium cerebelli?
Between the telencephalon & cerebellum
What are 3 descriptive properties of the Dura Mater?
Tough, smooth, fibrous
How many ventricles are there in the ventricular system?
4
What do the ventricles in the ventricular system contain?
Cerebrospinal fluid (CSF)
How many lateral ventricles are there?
2
What are the (large) lateral ventricles associated with?
Telencephalon
What is the 3rd ventricle associated with?
Diencephalon
What is the 4th ventricle associated with?
Brainstem
The interventricular foramen connects which ventricles?
The lateral ventricles with the 3rd ventricle
The cerebral aqueduct connects which ventricles?
3rd & 4th
Where does the cerebellum attach? (Dorsally or ventrally?)
Dorsally (in axis B)
Which ventricle is associated with the brainstem?
4th
What type of nerves emerge from the brainstem?
Cranial nerves
How many pairs of cranial nerves are there?
12
The cerebellum is attached dorsally to the pons via which structures?
Peduncles
What labels / notation is used to refer to cranial nerves?
Roman numerals (I-XII)
CN1-12
Which part of the brain are the cranial nerves most associated with?
Brainstem
What are the 3 types of cranial nerves?
- Sensory only
- Motor only
- Mixed sensory & motor (contain both types of fibres)
What is the origin of CN1 & CN2
The forebrain
What is the origin of all cranial nerves other than CN1 & CN2?
So CN3-12
The brainstem
Which is the only cranial nerve that is dorsal?
Trochlear
Which cranial nerves are purely motor?
CN3 - oculomotor - ability to move & blink eyes
CN4 - trochlear - ability to move eyes up & down or back & forth
CN6 - abducens - ability to move eyes
Which cranial nerves are purely sensory?
OOV
CN1 - olfactory - sense of smell
CN2 - optic - ability to see
CN8 - vestibulocochlear (auditory) - sense of hearing & balance
Which cranial nerves are mixed sensory & motor?
CN5 - trigeminal - sensations in face & cheeks, taste & jaw movements
CN7 - facial - facial expressions & sense of taste
CN9 - glossopharyngeal - ability to taste & swallow
CN10 - vagus - digestion & heart rate
CN11 - accessory (spinal accessory) - shoulder & neck muscle movement
CN12 - hypoglossal - ability to move tongue
What are all of the names of the cranial nerves in order ?
(OOOTTAFVGVAH)
CN1 - Olfactory
CN2 - Optic
CN3 - Oculomotor
CN4 - Trochlear
CN5 - Trigeminal
CN6 - Abducens
CN7 - Facial
CN8 - Vestibulocochlear (auditory)
CN9 - Glossopharyngeal
CN10 - Vagus
CN11 - Accessory (spinal accessory)
CN12 - Hypoglossal
The interventricular foramen and the cerebral aqueduct connect_______
The ventricles of the ventricular system
What part of the brainstem do the Trochlear (CN4) and Trigeminal (CN5) cranial nerves originate from?
Pons
What part of the brainstem do the Abducens (CN6), Facial (CN7) & Vestibulocochlear (CN8) cranial nerves originate from?
The medulla / pons boundary
What part of the brainstem do CN9-12 originate from?
The medulla
Which ventricles does the central aqueduct in the midbrain connect?
The 3rd & 4th
What are the roles of the superior and inferior colliculi (part of the Tectum) in the midbrain?
Superior - involved in visual processing & coordination of eye movements
Inferior - involved in auditory processing
What is the major division of the forebrain?
The Diencephalon
What are the 2 divisions of the forebrain?
- Diencephalon
- Telencephalon
What are the components of the diencephalon? (5)
- Thalamus
- Epithalamus (above the thalamus)
- Hypothalamus (below the thalamus)
- Pineal gland
- Pituitary gland
Which structure is the pineal gland (aka. Epiphysis) associated with?
The Epithalamus
Which structure is the pituitary gland (aka. Hypophysis) associated with?
The hypothalamus
Which cranial nerve originates from the hypothalamus?
CN2 - optic nerve
What hormone is produced by the pineal gland? And what is its role?
Melatonin
Associated with sleep & circadian rhythm
What are the 2 divisions of the pituitary gland? And how do they release hormones into the blood?
- Posterior pituitary gland = neurohypophysis (direct release of hormones into the blood)
- Anterior pituitary gland = andenohypophysis (release of hormones via the pituitary portal vessel & hypothalamic neurosecretory neurone)
What system is regulated by the hypothalamus?
The autonomic system (hormonal)
How many lobes does the cerebral cortex have?
4 lobes for each cortex - 8 in total
What are the 4 lobes of (each) cerebral cortex called?
- Frontal lobe (front)
- Parietal lobe (middle -> back)
- Occipital lobe (back)
- Temporal lobe (side)
What are the names for the ‘ridges’ and ‘valleys’ of the cerebral cortex?
Ridges = gyri (gyrus)
Valleys = sulci (sulcus) / fissure
What is the location of the longitudinal cerebral fissure ?
Runs down the midline of the brain, separate the 2 cortices
What is the location of the central sulcus?
Runs horizontally across the middle of the head
Separates the frontal & parietal lobes
What is the location of the lateral sulcus / fissure?
Deep fissure between the temporal lobe and the rest of the brain (on the side of the head)
The cerebral cortex is a layered structure. How many layers does it have?
6
The cerebral cortex contains what type of neurones? What is a key feature of these neurones?
Pyramidal neurones which have spiny dendrites
Brodmann categorised regions of the cerebral cortex by what? What are these regions now associated with?
Histological differences in cellular structure
These regions are now associated with functional specialisations
What is the Circle of Willis?
A circular anastomosis of arteries which supplies almost all of the brain’s blood
What is the advantage of the Circle of Willis?
It acts as a protective mechanism - ensures that there if there is disruption to one of the vessels (e.g., a blockage), then other vessels can work to make this up
Maintains pressure
Which are the arteries which are the main suppliers of the Circle of Willis?
- Vertebral arteries (comes up from the vertebrae in the SC)
- Carotid arteries (come up through the skull, pass through the carotid canal and emerge next to the optic chiasma)
What is the path of the Circle of Willis?
Basiliar artery -> posterior cerebral artery -> posterior communicating artery -> internal carotid artery -> anterior cerebral artery -> anterior communicating artery -> down the other anterior cerebral artery -> back across the internal carotid artery -> down posterior communicating artery -> down posterior cerebral artery
How many layers does the hippocampus have?
3
(That is why it is sometimes referred to as the ‘archicortex’)
UCL’s John O’Keefe discovered place cells that appear to underlie which process?
Spatial navigation
- experiments showed that people in positions that demanded high levels of spatial navigation (e.g., taxi drivers) - had larger hippocampus
What are the 2 different types of neuronal arrangement?
- Layers
- Nuclei
Give 3 examples of structures in the brain that have a layered neuronal arrangement ? (3)
Cerebral cortex
Cerebellum
Hippocampus
What is an example of a structure in the brain with a nuclei neuronal arrangement?
Hypothalamus
Cajal & Golgi found a way to ____
Stain a single cell
Before, it was difficult to see - i.e., when staining the cortex with Nissl stain (which marks nucleic acids), it would stain all of the cells
Using the Golgi system - you are able to see a single cell & it’s entire morphology
What are the folds in the cerebellum called?
Folia
The cerebellum has a cerebellar cortex (grey matter) which has 3 layers. What are these layers?
Outer to inner:
- Molecular
- Piriform / Purkinje cell layer (contains cell bodies of Purkinje cells)
- Granular (contains granular cells)
What are the 3 different brain flexures called?
Cephalic flexure (between 2 axes in the human brain)
Pontine flexure
Cervical flexure
What is the smallest division of the human brain?
The midbrain
What are the components of the midbrain?
- Tectum
- Tegmentum
What is the Tectum (of the midbrain) responsible for?
Auditory / vision reflexes
What are the 2 components of the Tectum and what do they control?
- Superior colliculus (top part) - controls visual reflexes
- Inferior colliculus (bottom part) - controls auditory reflexes
What is the functional specialisation of Wernicke’s area?
What Brodmann area is it?
Speech understanding (close to hearing area)
Brodmann area 22
What is the functional specialisation of Broca’s area?
What Brodmann area is it?
Speech generation (close to frontal lobe)
Brodmann area 44
What connects Wernicke & Broca’s areas?
The arcuate fasciculus
The cerebral cortex’s blood supply is from 3 main arteries. What are they?
- Anterior cerebral artery - mainly supplying medial surface of frontal & parietal lobes (because its coming up through the middle)
- Posterior cerebral artery - mainly supplying medial surface of occipital lobe & medial part of the temporal lobe
- Middle cerebral artery - main supplier of lateral part of the brain
Hippocampus dysfunction is thought to underlie what condition?
Amnesia
What is the name of the ‘horn’ of the hippocampus?
Amnon’s horn / cornu Amnois (CA)
(Regional identities CA1-CA4)
What are the inputs and outputs of the cerebellar cortex?
Inputs via
- climbing fibres onto Purkinje cells
- parallel fibres from bifurcated granule cell axons
Output
- from Purkinje cell axons
What is decussation?
The crossing over of nerve fibres from one side of the body to the other - occurs in either the brain or spinal cord
