Lecture 21 - structure and layout of major brain areas, basic sensory and motor pathways

Question 1

Central sulcus

Answer 1

Separates frontal and parietal lobes

Question 2

Parieto-occipital sulcus

Answer 2

Separates parietal and occipital lobes

Question 3

Lateral sulcus

Answer 3

Seperates temporal lobe from frontal and parietal lobes

Question 4

Transverse fissure

Answer 4

Separates cerebrum from cerebellum

Question 5

Brain lobes

Answer 5

There are 4 lobes on each side of the brain (frontal, occipital, parietal and temporal)

Lobes of the brain are named after the bones above them

Lobes are located in the cerebrum and are divided by sulci and gyri

Question 6

Frontal lobe

Answer 6

Frontal lobe has the motor cortex (also personality, behaviour, mood and language)

Question 7

Parietal lobe

Answer 7

Parietal lobe has the somatosensory cortex (also association cortex - faces, shapes, words etc)

Question 8

Occipital lobe

Answer 8

Occipital lobe (vision)

Question 9

Temporal lobe

Answer 9

Temporal lobe (hearing, memory)

Question 10

Cerebral cortex

Answer 10

Outermost layer of the brain made up primarily of grey matter

Question 11

Corpus callosum

Answer 11

White matter therefore it is made up of axons and is therefore is a tract (commissural tract)

Function - communication and connection between the two cerebral hemispheres (as it is a commissural tract)

Question 12

Brainstem

Answer 12

Midbrain
pons - Large bit that sticks out anteriorly
medulla oblongata - continuous with the spinal cord
Brainstem connects the cerebrum to the spinal cord

Question 13

Diencephalon

Answer 13

The diencephalon can be found just above the brainstem between the cerebral hemispheres; it forms the walls of the third ventricle. Contains the thalamus and hypothalamus

Question 14

Thalamus

Answer 14

The thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both.

Question 15

Hypothalamus

Answer 15

The hypothalamus is a small region of the brain. It’s located at the base of the brain, near the pituitary gland.

Question 16

Cerebellum

Answer 16

The cerebellum is located inferior to (underneath) the occipital lobe of the cerebrum.

The cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements.

Question 17

White matter of the brain

Answer 17

There are three main kinds of white matter tracts: projection, commissural, and association. The largest white matter structure of the brain is the corpus collosum, a form of commissural tract that connects the right and left hemispheres.

Question 18

Grey matter of the brain

Answer 18

cerebral cortex

Question 19

Grey and white matter in the brain versus the spinal cord

Answer 19

In the spinal cord, the grey matter is the inner section and the white matter is the outer section …it is the opposite in the brain, for the most part the great matter is on the outside and the white matter is on the inside (there are some exceptions though)

Question 20

Deep nuclei in the brain

Answer 20

Deep in the brain are these places with collections of cell bodies
Collections of cell bodies, that are not in the cerebral cortex are called nuclei

Question 21

Commissural tracts

Answer 21

Type of white matter
Axons cross from side to side - both directions (from one side of the brain to the other)
Example is the corpus callosum (allows the left and right side of the brain to be coordinated as they are able to communicate with each other)

Question 22

Projection tracts

Answer 22

Type of white matter
Axons extend between cortex and other CNS areas outside cerebrum
Example - corticospinal tract

Question 23

Association tracts

Answer 23

Type of white matter
Axons on the same side within the cerebral cortex.
Communication between brain areas - short or long distance (information may be needed to be transferred to another part of the brain)

Question 24

Primary motor cortex

Answer 24

Pre central gyrus (the gyrus that comes before the central sulcus)
In the frontal lobe (precentral gyrus)
Involved in voluntary movement - execution
Somatotopically organised - neurons are mapped depending on where they go an innervate in the body (homoculus)
Larger area = highly innervated body part

Question 25

Primary somatosensory cortex

Answer 25

In the parietal lobe (postcentral gyrus)
Involved in processing somatic sensations of different parts of the body
Somatotopically organised - neurons are mapped depending on where they go an innervate in the body (homoculus)
Larger area = high sensory innervated body part

Question 26

Primary motor cortex organisation

Answer 26

The precentral gyrus functions as the primary motor cortex

Specific regions of the primary motor cortex control specific regions of the body

Question 27

Corticospinal pathway

Answer 27

Main motor output system for voluntary movements in our bodies
Pathway for voluntary movement

1st (upper) motor neuron
Cell body in primary motor cortex (brain)
Axon crosses at medulla and extends down spinal cord (axon extends from motor cortex to spinal cord on opposite side)
Synapses with second neuron (makes synapse on lower motor neuron) in ventral horn of spinal cord

2nd (lower) motor neuron
Cell body in ventral horn (grey matter) of spinal cord
Axon extends from the spinal cord (ventral root) out to the body (nerve)
Axon synapses with skeletal muscle

Question 28

Primary motor cortex damage

Answer 28

Damage to the motor cortex, muscle weakness and paralysis in region of body corresponding to the location of damage

Question 29

Primary somatosensory cortex organisation

Answer 29

The post central gyrus functions as the primary somatosensory cortex
Specific regions of the somatosensory cortex receive sensory information from specific regions of the body (these neurons are receiving info (compared to motor cortex as those cells are sending info down))

Question 30

The dorsal/posterior column pathway

Answer 30

Pathway for proprioception and discrimination - three neurons between sensory receptor in the body and somatosensory neuron in the post central gyrus

1st neuron
Sensory information comes from skin into cell body in dorsal root ganglion (unipolar neuron)
Peripheral fibre (input zone) from sensory receptor in skin
Central fibre (output zone) ascends toward brain in dorsal columns (spinal cord white matter)
Axon ascends spinal cord
Synapses with neuron 2 in the medulla oblongata

2nd neuron
Cell body in medulla oblongata
Axon crosses to the opposite side and ascends
Make synapse on neuron 3 in the thalamus

3rd neuron
Cell body in thalamus
Axon ascends to somatosensory cortex, synapses onto a SSC neuron, sensation is perceived

Question 31

Primary somatosensory cortex damage

Answer 31

Cell in somatosensory cortex that receives information from dorsal column pathway dies
Ascenting information has no place to go therefore there is no perception of touch in that area of body (there is no cell to transfer information to)

Question 32

Myelin is…

Answer 32

Fat so often comes up white on microscope images

Question 33

White versus grey matter

Answer 33

White matter is myelinated axons whereas grey matter is everything else (cell bodies, unmyelinated axons, axon terminals)

Question 34

`What are the anterior and posterior horns made up of?

Answer 34

Grey matter - which is cell bodies, unmyelinated axons, dendrites and axon terminals

Question 35

You might see other nuclei within the grey matter, what are these cell types likely to be?

Answer 35

Glial cells (support cells)

Question 36

What is white matter composed of?

Answer 36

Myelinated axons called a tract