L14: Introduction to neuroanatomy Flashcards
What are the different divisions of the nervous system?
CNS: brain, brainstem, spinal cord, cerebellum
PNS: includes cranial nerves
What is the forebrain?
Cerebrum and the diencephalon (deep structures)
(mostly cerebrum)
-sits on top of the brainstem
What does the diencephalon consist of?
Hypothalamus, 2x thalamus
Thalamus: act as relay stations for all the senses coming from the body
What are the 3 key parts of the brainstem?
Top to bottom:
Midbrain
Pons (bulges)
Medulla
What is the cerebellum?
Structure found behind the brainstem, and has connections to the brain stem
What is the cerebrum?
Split into 2 hemispheres
Cortex: grey matter, around outside, due to high density of cell bodies
White matter: myelinated axons
Grey matter can be found in the middle of the brain e.g. the thalami
Why do we have gyri and sulci?
Increase the SA, and therefore the number of neurones we can pack inside the brain
What are fissures?
Deeper than sulci
Longitudinal fissure splits the hemispheres
Lateral fissure
What separates the hemispheres into lobes?
Certain gyri, sulci and fissures
What are the 4 key lobes?
Frontal (L/R)- central sulcus denotes the most posterior portion of the frontal lobe
Parietal (L/R)- past central sulcus, parieto-occipital sulcus can be seen medially and separates the parietal lobe from the occipital lobe
Occipital (L/R)- past the parietal lobe, the sulcus to denote this is hard to see on the brain
Temporal (L/R)- laterally, denoted by lateral fissure against the frontal and parietal, but the distinguisment b/w temporal and occipital is hard to see
What is the corpus callosum?
Collection of white matter (packed full of neuronal axons)
-allows communication between the two hemispheres
What is attached to the hypothalamus?
Pituitary gland, which is attached via the pituitary stalk
What is the septum pellucidum?
Thin membrane splitting the cavity below the corpus callosum which is filled with cerebrospinal fluid
What does rostral and caudal mean (orientation terminology of brain)?
Rostral: towards nostril (same as anterior)
Caudal: towards tail (same as posterior)
The orientation terminology of the spinal cord is not equivalent to the terminology of the brain, as the brain is on an angle.
What are the nerves associated with different regions of the brainstem?
Cranial nerves (you have pairs of cranial nerves, so you have each one of the pair emerging from either side of the brainstem)
What is the major function of the brainstem?
Midbrain: coordinating eye movement and reflexes of pupils in response to light
Pons: feeding (trigeminal nerve-muscles of mastication), controlling sleep
Medulla: cardiovascular and respiratory systems
Why is even just a small lesion in the brainstem significant?
There is a lot of nervous tissue packed into a small area
What are the key functions of the frontal lobe?
- voluntary motor control (gyrus just in front of central sulcus: pre-central gyrus)
- speech production
- social behaviour
- impulse control
- higher cognition
What is known as the primary motor complex?
Pre-central gyrus
What are the key functions of the temporal lobe?
-language
-emotion
-long term memory
Special senses:
-sense of smell
-hearing
-taste
What are the key functions of the parietal lobe?
- spatial awareness
- processing sensory info (not special senses): somatosensory perception: post-central gyrus
What are the key functions of the occipital lobe?
Visual perception
What is the function of the cerebellum?
Co-ordination and motor learning
-sits just beneath the tentorium cerebelli
What is the uncus?
Most medial part of the temporal lobe, receives olfactory info
-uncus can be pushed past the tentorium through the tentorium notch when there is a rise in pressure in the skull= UNCAL HERNIATION
What nerve is the uncus very close to?
3rd cranial nerve coming off the midbrain: oculomotor nerve
-uncal herniation can push against this nerve
How is the primary motor cortex described as homunculus?
Homunculus means little man
If you cut coronally into the complex specific parts of the cortex are responsible for specific part of the bosy
Laterally to medially: pharynx, tongue, face, hands, arms, trunk, legs, feet, genitals
(head and neck will be found laterally)
-somatosensory complex is similar to this however some parts are more heavily represented (lips, tongue, fingertips)
Why is the topography of the brain important?
You can localise what part of the body a lesion to the brain will affect
How does the motor cortex link to the peripheral nervous system?
The primary motor cortex in one half of the brain is responsible for the motor control in the contralateral side of the body.
-motor neurone runs down same side as the side it arose, at the level of the medulla the neurone crosses to the opposite side, where it runs down that side of the spinal cord and synapse with a spinal nerve
(this is the same with the sensory cortex)
Are all cranial nerves mixed like spinal nerves are?
No, only some cranial nerves are mixed, the rest are motor
What is the relationship between the motor cortex and the cranial nerves?
-the motor nerve runs down the ipsilateral side, until it reaches a point where it wants to communicate with cranial nerves on that side
-it needs to cross as it is also contralteral, however it crosses adjacent to the cell body onto which it will synapse
However
-there is also some control from the ipsilateral cortex
Dual cortical innervation to cranial nerves
What does it mean when you say that spinal nerves have uni-cortical control?
The spinal nerves receive input from just one primary motor cortex (uni-cortical, e.g. right and left)
Which cortex has dominant control over the cranial nerve?
Contralateral cortex, ipsilateral control only comes into play when something happens to the dominant pathway
What is the definition of decussate?
Cross over
Do all cranial nerves have cortical input from the ipsilateral cortex?
No, not all do
