08-09-23 - Neuroanatomy: Synopsis and revision Flashcards
Learning outcomes
- Describe briefly how the brain develops
- List the general functions of the major parts of the brain
- Explain the functional anatomy of the hypothalamus and hypophysis
- Describe the location and, briefly, function of the respiratory centres
- Describe the reticular formation and, briefly, its functions
- Describe neurons and neuroglia and their functions
- Explain the topographic organization of the neurons in the spinal cord and brain stem and the clinical significance of this organization
- Compare the motor signs and symptoms following injury to the peripheral (LMN) and central (UMN) nervous systems
What embryological structure does the CNS develop from?
Describe this structure.
What can occur if the ends of the neural tube don’t close?
How do vesicles form?
What is the name of the 3 primary vesicles of the neural tube?
What does the cavity of the neural tube develop into?
- The CNS develops from the neural tube
- The neural tube has 2 ends open (which eventually close) with a wall and a cavity inside
- If the cranial end of the neural tube doesn’t close, this can result in anencephaly
- If the caudal end of the neural tube doesn’t close, this can result in spina bifida
- There is differential growth rate of the neural tube, which leads to swellings called vesicles
- Name of the 3 primary vesicles of the neural tube:
1) Forebrain
2) Midbrain
3) Hindbrain - The cavity of the neural tube develops into ventricles filled with CSF
Describe what the primary vesicles of the neural tube develop into (in picture)
Parts of the CNS.
What 3 structures makes up the brainstem?
What 2 structures make up the cerebrum?
What 3 structures make up the encephalon (brain)?
What 2 structures make up the CNS?
- Parts of the CNS
- 3 structures that make up the brainstem:
1) Midbrain
2) Pons
3) Medulla - 2 structures make up the cerebrum:
1) Telencephalon (cortex + white matter + basal nuclei)
2) Diencephalon - 3 structures make up the encephalon (brain):
1) Cerebrum
2) Brain stem
3) Cerebellum - 2 structures make up the CNS:
1) Encephalon
2) Spinal cord
What structures are cerebral lobes?
What are they formed and separated by?
What are the 6 cerebral lobes?
Label the lobes and sulci of the brain (in picture)
- Cerebral lobes are parts of the hemispheres (telencephalon)
- They are formed by gyri and separated by sulci, which appeared early in development
- 6 cerebral lobes:
1) Frontal lobe
2) Parietal lobe
3) Occipital lobe
4) Temporal lobe
5) Insula
6) Limbic lobe - Lobes and sulci labelled on the diagram
What was used to understand the functions of different regions of the nervous system?
- Animal experiments and Functional imaging techniques (PET, fMRI) helped us understand the functions of different regions of the nervous system
Where is the frontal lobe located?
What are the 3 functions of the frontal lobe?
Which part of the frontal lobe is responsible for each function?
- The frontal lobe is located anterior to the central sulcus and superior to the lateral sulcus
- 3 functions of the frontal lobe:
1) Voluntary muscle movement
* Primary motor cortex
* Premotor cortex
2) Language production
* Frontal operculum in the dominant hemisphere (Broca’s area)
3) Higher cognitive functions (impulse control, decision-making, problem solving, social interaction, attention)
* Prefrontal cortex (involved in personality)
Where is the parietal lobe located?
What are the 4 functions of the parietal lobe?
Which part of the parietal lobe is responsible for each function?
- The parietal lobe is located posterior to the central sulcus and superior to the lateral sulcus
- 4 functions of the parietal lobe:
1) Integration of somatosensory information
* Primary and secondary somatosensory cortices
* Association cortices
2) Language comprehension
* Wernicke’s area (partially) in the dominant hemisphere
3) Movement
* Primary somatosensory cortex
4) Reading
Where are the temporal lobes located?
What are the 5 functions of the temporal lobes?
Which part of the temporal lobes is responsible for each function?
What is uncal herniation?
How fatal is it?
- The parietal lobes are located inferior to the lateral sulcus
- 5 functions of the temporal lobes:
1) Auditory processing
* Primary and secondary auditory cortices
2) Comprehension of speech
* Wernicke’s area (primarily, immediately posterior to auditory area)
3) Olfaction
* Antero-medial temporal lobe, temporal pole
4) Emotional (esp. fear) processing
* Amygdala
5) Conscious memory and learning
* Medial temporal lobe especially Hippocampus and neighbouring cortical areas
- Uncal (hook) herniation is the displacement of the uncus through the tentorial notch, compressing the ipsilateral crus cerebri
- This is a surgical emergency
Temporal lobe diagram
Lobes and sulci diagram
Where are the occipital lobes located?
What are the 2 functions of the occipital lobes?
Which part of the occipital lobes is responsible for each function?
- Occipital lobes are located posteriorly to the parietooccipital sulcus
- 2 functions of the occipital lobes:
1) Visual perception and processing
* Primary and secondary visual cortices
2) Memory
Where are the insula and limbic lobe located?
What are the 3 functions of the insula?
What are 2 functions of the limbic lobe?
What are the 5Fs of the limbic lobe?
- The insula is located deep within the lateral sulcus of the brain
- 3 functions of the insula:
1) Olfaction
2) Taste
3) Discriminative touch - The limbic lobe is lateral to the thalamus, underneath the cerebral cortex, and above the brainstem
- 2 functions of the limbic lobe:
1) Behavioural and emotional responses
2) Learning and memory - A quick way to remember the functions of the limbic system is to think about five “F’s”:
1) Feeding (satiety & hunger)
2) Forgetting (memory)
3) Fighting (emotional response)
4) Family (sexual reproduction and maternal instincts)
5) Fornicating (sexual arousal)
What are the 5 parts of the diencephalon?
- 5 parts of the diencephalon:
1) Thalamus
* Biggest part
* On the lateral walls of the third ventricle
2) Hypothalamus
3) Metathalamus
* Medial and lateral geniculate bodies
* specific thalamic nuclei that relay the auditory and optic pathways, respectively
2) Epithalamus
* Pineal body
* Your pineal gland, also called the pineal body or epiphysis cerebri, is a tiny gland in your brain that’s located beneath the back part of the corpus callosum.
It’s a part of your endocrine system and secretes the hormone melatonin.
3) Subthalamus
What are 2 functions of the thalamus?
What are 6 functions of the hypothalamus?
- The thalamus is a major relay station for:
1) Sensory impulses ascending to sensory cortex except smell (smell goes to cortex first, then thalamus)
2) Inputs from subcortical motor nuclei and cerebellum travelling to the cerebral motor cortex
- 6 functions of the hypothalamus:
1) Autonomic control
2) Endocrine control (w/pituitary gland)
3) Regulation of thirst – Fluid-electrolyte balance
4) Eating - energy balance
5) Sexual behaviour, reproduction
6) Body temperature
What are the 2 parts of the metathalamus?
What are they each responsible for?
What structures do they have connections with?
- 2 parts of the metathalamus:
1) Medial geniculate body
* Involved in hearing
* Have connection with inferior colliculus and lateral lemniscus
2) Lateral geniculate body
* Involved in vision
* Most of the neurons in the optic tract synapse here
* Have connection with Superior colliculus
What does the hypophysial (pituitary) gland develop from?
What are the 2 parts of the pituitary gland?
What is their function?
- The hypophysial (pituitary) gland develops in part from diencephalon (posteior lobe, Neurohypophysis) and roof of the mouth (Anterior lobe, adenohypophysis)
- 2 parts of the pituitary gland:
1) Neurohypophysis
* Median eminence, pituitary stalk and posterior lobe of pituitary
* Secretes 2 hormones produced in hypothalamus
2) Adenohypophysis
* Produces and secretes hormones into hypophysial portal system
What are the 3 parts of the brainstem?
- 3 parts of the brainstem:
1) Midbrain
2) Pons
3) Medulla oblongata
What are the 3 parts of the midbrain?
What are their functions?
- 3 parts of the midbrain:
1) Superior & inferior colliculi (visual & auditory reflex centres)
2) Red nucleus (nucleus ruber) (subcortical motor centre)
3) Substantia nigra (involved in reward-seeking, motor learning and others)
What is the purpose of the conduction area in the pons?
What do the nuclei in the pons contribute to?
- The conduction area of the pons acts as connections between forebrain and cerebellum
- Nuclei in the pons contribute to regulation of respiration (apneustic area) as well as hearing and balance
What are the 3 different structures of the medulla oblongata?
What is their function?
- 3 different structures of the medulla oblongata:
1) Pyramidal decussation
* Crossing of corticospinal axons
2) Vital centres
* Regulate respiratory rhythm, heart rate, blood pressure
3) Non-vital centres
* Regulate cough, sneeze, swallowing, and vomiting (area postrema)
What is another name for the area postrema of the medulla oblongata?
Where is the area postrema located?
What structure does the area postrema lack?
What does this trigger?
What structures does it have connections with?
How does the area postrema induce vomiting?
- The area postrema of the medulla oblongata is also known as the chemoreceptor trigger zone, emetic (vomiting) centre
- The area postrema is Located on the roof of the 4th ventricle
- It lacks a blood-brain barrier (one of circumventricular organs), meaning emetic toxins in the blood & CSF stimulate neurons in this area.
- Have connections with the hypothalamus and reticular formation
- Induces emesis by coordinating muscular movements for retching & vomiting
What does the reticular formation of the medulla oblongata consist of?
What structures is it connected to? How is it divided?
- The reticular formation of the medulla oblongata is a polysynaptic network in the brainstem, surrounding principal sensory & motor nuclei and tracts
- The reticular formation is connected to virtually all parts of the CNS but connectivity is extremely complex
- It is divided into 3 longitudinal zones/fields
1) Median
2) Paramedian
3) Lateral reticular formation
Where are respiratory centres located?
What structures are responsible for inspiration and expiration?
How does the Dorsal Respiratory Group (DRG) function?
What happens if the DRG is completely supressed?
- Respiratory centres are located in the medulla and pons
- Dorsal Respiratory group (DRG) – INSPIRATION
- Establishes the rhythm of normal quiet inspiratory breathing
- Neurons in DRG stimulate nerves to the diaphragm and external intercostals muscles
- Ventral Respiratory group (VRG) – EXPIRATION
- If DRG is completely suppressed breathing stops (overdose sleeping pills, alcohol, etc.)
What are the 4 different types of neurons?
- 4 different types of neurons:
1) Unipolar (not found in adult humans)
2) Bipolar
3) Pseudounipolar
4) Multipolar
Describe the organization of neurons from the spinal cord to the brain stem?
How do arteries that supply the spinal cord differ medially and laterally?
- The organization of neurons from the spinal cord to the brain stem:
- Central grey matter more vertical
- Grey matter “opens up “dorsally”
- Central grey matter more horizontal
What are the myelinating cells of the CNS and PNS?
What type of condition is Multiple sclerosis (MS)?
What are 4 effects of MS on the CNS?
What symptoms does MS present with?
- The myelinating cells of the CNS are oligodendrocytes (can myelinate multiple axons each)
- The myelinating cells of the PNS are Schwann cells (can myelinate 1 axon each)
- Multiple sclerosis (MS) is a demyelinating condition
- 4 effects of MS on the CNS:
1) Development of plaques (patches) of demyelination in the white matter
2) Axons also undergo degeneration
3) Impulse conduction is compromised (in neighbouring myelinated fibres as well)
4) Plaques are progressively replaced by glial scar tissue
- MS is not anatomically selective, meaning it can affect different areas in each patient and present with variable symptoms
Describe the neuroglia (supporting cells) of the CNS and PNS (in picture).
What are brain tumours mostly derived from?
- Brain tumours are mostly derived from astrocytes
What is Diffusion tensor imaging (DTI) used for?
What are the 3 potential directions of axons in white matter tracts (myelinated)?
What type of fibres are these directions associated with?
Where can they be found in the brain?
- Diffusion tensor imaging (DTI) used to generate 3D model showing many axons connecting specific areas of the CNS
- 3 potential directions of axons in white matter tracts (myelinated):
1) Up / down: Projection fibres (Eg. internal capsule)
2) Front / back: Association fibres (Eg. superior longitudinal fasciculus)
3) Left / right: Commissural fibres (Eg. corpus callosum, posterior commissure)
Projection fibres diagram
Commissural fibres diagram
Motor pathways.
Where are upper and lower motor neuron bodies found?
Where do UMN axons travel?
- Motor pathways (Upper and lower motor neurons instead of presynaptic and postsynaptic neurons)
1) Upper motor neuron (UMN)
* Neuron bodies in the cortex
* Most of the axons cross over in lower medulla
* Descend in the lateral column of spinal cord as lateral corticospinal tract ̶
* Synapse with LMN in the anterior horn
2) Lower motor neuron (LMN)
* Neuron bodies in the anterior horn
What are 3 signs of upper motor neuron lesions?
What are 4 signs of lower motor neuron lesions?
- 3 signs of upper motor neuron lesions:
1) Hypertonia (spasticity)
2) Hyper-reflexia
3) Abnormal reflex (Positive Babinski sign unless younger than 6 months old) - 4 signs of lower motor neuron lesions:
1) Hypotonia/Flaccidity
2) Hypo-reflexia/areflexia
3) Fasciculations
4) Atrophy/wasting of muscles
