Neuroanatomy Practical II PDF BDS 2, 06/12/2020

06/12/2020 NEUROANATOMY PRACTICAL II Brainstem & Cranial Nerves BDS 2 Part B: The Brainstem (Allow 60 mins) 1 1 06/12/2020 Brainstem: Overview https://www.youtube.com/watch?v=Mkj78h8w4a8 2 2 06/12/2020 (iii) The Brainstem 1. The diencephalon is made up in part of the thalamus and hypothalamus. Ident...

06/12/2020 NEUROANATOMY PRACTICAL II Brainstem & Cranial Nerves BDS 2 Part B: The Brainstem (Allow 60 mins) 1 1 06/12/2020 Brainstem: Overview https://www.youtube.com/watch?v=Mkj78h8w4a8 2 2 06/12/2020 (iii) The Brainstem 1. The diencephalon is made up in part of the thalamus and hypothalamus. Identify these and what is the name of the shallow depression that separates them? 3 2. Find the pineal gland. What is its major function? 3. The pituitary gland is not present. Why do you think this might be and where would it normally be found? 4. Identify the tectum, superior and inferior colliculi. 5. The tegmentum can be thought of as the “core” of the brainstem (see insert). Identify it on the large figure and what part of the brain is it continuous with above the midbrain? Sagittal View 3 3 06/12/2020 (ii) 3 The Brainstem Figs 3a and b represent isolated brainstems with the cerebellum removed b a 1. On both a and b, identify the medullary pyramids, olive, pons and cerebral peduncles (crura cerebri). V D 2. Which major motor tract descends (and decussates) in the medullary pyramids? 3. On b, identify the tectum, middle cerebellar peduncle and approximate position of the substantia nigra 4. Which cranial nerve is indicated by the arrow in b? Ventral View Lateral View 4 4 06/12/2020 (i) The Brainstem Sections 1 We will now look at some transverse sections of the brainstem. They are Weigert-Pal stained sections and so myelinated tracts will appear dark while cell bodies appear pale or unstained. Fig 4 Midbrain Ventral is always shown near the base of the slide and the section level is shown in the title of the slide and is also indicated on an insert to the figure. Levels are also shown in Figure 1 here. Pons Fig 3 Medulla The brainstem changes considerably in appearance along its rostro-caudal axis and depicted here are just examples through the major brainstem regions. Many important levels are not shown so do not regard this exercise as a thorough representation of brainstem organisation. Fig 2 Ventral View Lateral View 5 5 06/12/2020 (ii) The Medulla 1. Why do you think this is described as a "closed" medulla? Clue: think of the relationship of the medulla to the IVth ventricle Closed medulla (level of the pyramidal decussation) 2 2. Find and label the gracile and cuneate nuclei. What parts of the body do they represent and where are the cell bodies of the axons that terminate within them? 3. Identify the nucleus of the accessory nerve (C.XI). 4. Locate the spinal sensory nucleus of the trigeminal nerve (C.V). What type of sensory information does it deal with? 5. Compare the essential differences between the spinal sensory nucleus of C.V and the gracile and cuneate nuclei. Think of parts of the body served and types of sensation. 6. Why is the anterior fissure distorted to the left? 6 6 06/12/2020 (ii) The Pons 3 Pons (level of the facial colliculus) 1. What is the name of the space indicated by “A” and the large area of axon tracts on either side (labelled “B” on the right)? 2. Where are the basilar and tegmental parts of the pons? 3. The axons indicated by the white arrows are the same nerve. What is it and how do you account for it being seen at multiple locations? 4. Find the approximate locations of the nuclei of the facial nerve (C.VII) and abducens nerve (C.VI). 5. What are the blocks of white matter shown by the asterisks? Think of similar, ventral positions in the medulla. 7 7 06/12/2020 (ii) The Midbrain 1. Identify the tectum, cerebral aqueduct and crura cerebri (cerebral peduncles) Midbrain (superior colliculi) 4 2. Identify the substantia nigra. Why does it appear pale here? 3. The substantia nigra has two parts: the pars compacta and pars reticularis. The pars compacta of the substantia nigra is involved in motor control and loss of neurons here commonly results in Parkinson’s disease. What is the main neurotransmitter of these neurons? 4. What are the nerves indicated by the arrowheads and what is their function? 5. What is the area indicated by the asterisks? 8 8 06/12/2020 NEUROANATOMY PRACTICAL II Brainstem & Cranial Nerves Part A: ANSWERS 9 9 06/12/2020 (iii) The Brainstem 1. The diencephalon is made up in part of the thalamus and hypothalamus. Identify these and what is the name of the shallow depression that separates them? Hypothalamic sulcus 2. Find the pineal gland. What is its major function? Hormone (esp melatonin) production 3. The pituitary gland is not present. Why do you think this might be and where would it normally be found? 3 Thalamus Pineal gland Hypothalamus 4. Identify the tectum, superior and inferior colliculi. 5. The tegmentum can be thought of as the “core” of the brainstem (see insert). Identify it on the large figure and what part of the brain is it continuous with above the midbrain? Sagittal View 10 10 06/12/2020 (iii) The Brainstem 1. The diencephalon is made up in part of the thalamus and hypothalamus. Identify these and what is the name of the shallow depression that separates them? Hypothalamic sulcus 2. Find the pineal gland. What is its major function? Hormone (esp melatonin) production 3. The pituitary gland is not present. Why do you think this might be and where would it normally be found? It (asterisk shows site) is protected by part of the sphenoid bone and has been retained when the brain was removed 4. Identify the tectum, superior and inferior colliculi. 5. The tegmentum can be thought of as the “core” of the brainstem (see insert). Identify it on the large figure and what part of the brain is it continuous with above the midbrain? 3 Thalamus Pineal gland * Hypothalamus Sagittal View 11 11 06/12/2020 (iii) The Brainstem 1 The diencephalon is made up in part of the thalamus and hypothalamus. Identify these and what is the name of the shallow depression that separates them? Hypothalamic sulcus 2. Find the pineal gland. What is its major function? Hormone (esp melatonin) production 3. The pituitary gland is not present. Why do you think this might be and where would it normally be found? It (asterisk shows site) is protected by part of the sphenoid bone and has been retained when the brain was removed 4. Identify the tectum, superior and inferior colliculi. 5. The tegmentum can be thought of as the “core” of the brainstem (see insert). Identify it on the large figure and what part of the brain is it continuous with above the midbrain? 3 Superior colliculus Tectum Inferior colliculus Sagittal View 12 12 06/12/2020 (iii) The Brainstem 1 The diencephalon is made up in part of the thalamus and hypothalamus. Identify these and what is the name of the shallow depression that separates them? Hypothalamic sulcus 2. Find the pineal gland. What is its major function? Hormone (esp melatonin) production 3. The pituitary gland is not present. Why do you think this might be and where would it normally be found? It (asterisk shows site) is protected by part of the sphenoid bone and has been retained when the brain was removed 4. Identify the tectum, superior and inferior colliculi. 5. The tegmentum can be thought of as the “core” of the brainstem (see insert). Identify it on the large figure and what part of the brain is it continuous with above the midbrain? Hypothalamus 3 Sagittal View 13 13 06/12/2020 (ii) 3 The Brainstem Figs 3a and b represent isolated brainstems with the cerebellum removed Cerebral peduncles Substantia nigra b a Tectum 1. On both a and b, identify the medullary pyramids, olive, pons and cerebral peduncles (crura cerebri). DTrochlear C. IV V Pons 2. Which major motor tract descends (and decussates) in the medullary pyramids? Corticospinal tract Olive Medullary pyramids 3. On b, identify the tectum, middle cerebellar peduncle and approximate position of the substantia nigra 4. Which cranial nerve is indicated by the arrow in b? Trochlear nerve (C. IV) Ventral View Middle cerebellar peduncle Lateral View 14 14 06/12/2020 (i) The Brainstem Sections 1 We will now look at some transverse sections of the brainstem. They are Weigert-Pal stained sections and so myelinated tracts will appear dark while cell bodies appear pale or unstained. Fig 4 Midbrain Ventral is always shown near the base of the slide and the section level is shown in the title of the slide and is also indicated on an insert to the figure. Levels are also shown in Figure 1 here. Pons Fig 3 Medulla The brainstem changes considerably in appearance along its rostro-caudal axis and depicted here are just examples through the major brainstem regions. Many important levels are not shown so do not regard this exercise as a thorough representation of brainstem organisation. Fig 2 Ventral View Lateral View 15 15 06/12/2020 (ii) The Medulla 1. Why do you think this is described as a "closed" medulla? Clue: think of the relationship of the medulla to the IVth ventricle Closed medulla (level of the pyramidal decussation) 2 The section is taken below the level of the IVth ventricle – note the smooth, round dorsal surface 2. Find and label the gracile and cuneate nuclei. What parts of the body do they represent and where are the cell bodies of the axons that terminate within them? Gracile nuclei: lower trunk and legs Cuneate nuclei: upper trunk and arms Gracile nuclei Cuneate nuclei Cell bodies are in the DRG 16 16 06/12/2020 (ii) The Medulla 3. Identify the nucleus of the accessory nerve (C.XI). 4. Locate the spinal sensory nucleus of the trigeminal nerve (C.V). What type of sensory information does it deal with? Pain and temperature 5. Compare the essential differences between the spinal sensory nucleus of C.V and the gracile and cuneate nuclei. Think of parts of the body served and types of sensation. Spinal sensory nucleus: Pain/temperature (Head & neck) Closed medulla (level of the pyramidal decussation) 2 C.V C.XI C.V C.XI Gracile & cuneate nuclei: Fine touch/conscious proprioception/vibration (Body) 17 17 06/12/2020 (ii) The Medulla 3. Identify the nucleus of the accessory nerve (C.XI). Closed medulla (level of the pyramidal decussation) 2 4. Locate the spinal sensory nucleus of the trigeminal nerve (C.V). What type of sensory information does it deal with? Pain and temperature 5. Compare the essential differences between the spinal sensory nucleus of C.V and the gracile and cuneate nuclei. Think of parts of the body served and types of sensation. Spinal sensory nucleus: Pain/temperature (Head & neck) Gracile & cuneate nuclei: Fine touch/conscious proprioception/vibration (Body) C.V C.XI C.V C.XI 6. Why is the anterior fissure distorted to the left? Decussation of the corticospinal tract 18 18 06/12/2020 (ii) The Pons 1. What is the name of the space indicated by “A” and the large area of axon tracts on either side (labelled “B” on the right)? A: IVth ventricle B: Middle cerebellar peduncle 2. Where are the basilar and tegmental parts of the pons? 3. The axons indicated by the white arrows are the same nerve. What is it and how do you account for it being seen at multiple locations? The facial nerve (C.VII) travels dorsally, around the nucleus of the abducens nerve (genu) and then exits ventrolaterally 4. Find the approximate locations of the nuclei of the facial nerve (C.VII) and abducens nerve (C.VI). Pons (level of the facial colliculus) 3 VI VII Tegmental Pons Basilar Pons 5. What are the blocks of white matter shown by the asterisks? Think of similar, ventral positions in the medulla. Axons of the corticospinal tract 19 19 06/12/2020 (ii) The Midbrain 1. Identify the tectum, cerebral aqueduct and crura cerebri (cerebral peduncles) 2. Identify the substantia nigra. Why does it appear pale here? No myelin just cell bodies, albeit pigmented 3. The substantia nigra has two parts: the pars compacta and pars reticularis. The pars compacta of the substantia nigra is involved in motor control and loss of neurons here commonly results in Parkinson’s disease. What is the main neurotransmitter of these neurons? Dopamine 4. What are the nerves indicated by the arrowheads and what is their function? Oculomotor nerve (C.III) Somatomotor to many extraocular muscles; parasympathetic to pupillary and ciliary muscles of the eye 5. What is the area indicated by the asterisks? Periaqueductal grey (PAG) Midbrain (superior colliculi) 4 Tectum Cerebral aqueduct Cerebral peduncles Substantia nigra 20 20