Lippincotts 2 - CNS

Question 1

what does the CNS consist of?

Answer 1

Brain and spinal cord

Question 2

how much does the brain weigh at birth?
describe the growth in the first 3 years (weight)
how much does the adult brain weigh?

Answer 2

at birth the brain weighs 400g
during the first 3 years the weight of the bhrain triples
adult brain weighs 1400g, 2% body weight

Question 3

from what does the adult nervous system originate during development?
when does development of the nervous system begin?

Answer 3

simple ectodermal tube. beginning the end of week 3 of gestation.

Question 4

describe the development of the neural tube…

Answer 4

• ectodermal plate thickens to form neural plate
  
  • neural plate fold around the midline groove
  • broad rostral end, fold appear (pivot points)
  • fusion begins on day 22
  • cranial neuropore closes day 24
  • caudal neuropore closes day 26

Question 5

what are neural crest cells?

what do they differentiate into?

Answer 5

neural crest cell appear as the fusion of the neural tube occurs. cells from the crest dissociate and migrate away from the neural tube.
they differentiate into a variety of cell types, inc:
- adrenal medulla
- odentoblasts
- schwann cells
- sensory neurons in spinal ganglia
- pigment cells (melinocytes)
- endocardium cushion cells and spiral septum
- branchial pouches (bone/cartilage)
- arachnoid pia

Question 6

developemtn of the brain: primary vesicles to secondary vesicles of neural tube…

Answer 6

the brain starts to develop in the 4th week of gestation.
primary vesicles: (rostal to caudal)
   1. prosencephalon (forebrain)
   2. mesencephalon (midbrain)
   3. rhombencephalon (hindbrain)

secondary vesicles:
1. prosencephalon &raquo_space;> telencephalon
diencephalon

2. mesencephalon &raquo_space;> mesencephalon
3. rhombencephalon&raquo_space;> metencephalon
   myelencephalon

Question 7

what does the prosencephalon subdivide to form?

Answer 7

the prosencephalon is the forebrain. this primary vesicles divides into the telencephalon (cerebral hemispheres) and the diencephalon (thalamus, hypothalamus and subthalamus)

Question 8

what is the mesencephalon?

Answer 8

the mesencephalon is a vesicle in the brain. it does not subdivide and forms the midbrain.

Question 9

what does the rhombencephalon form?

Answer 9

the rhombencephalon is the forebrain. the rhombencephalon is a primary vesicle that subdivides into the rostral metencephalon (pons and cerebellum) and the caudal myelencephalon (medulla)

Question 10

what are the lobes of the cerebral hemisphere?

Answer 10

the telencephalon grows to form a complex 3d structure. expands to form:

• frontal lobes, anterior
• parietal lobes, lateral and superior
• occipital lobes, posterior and inferior
• temporal lobes

expansion results in the cerebral hemisphers covering the diencephalon, midbraina and pons. (cerebellum is posterior, not covered)

Question 11

what is grey matter?

Answer 11

grey matter is the accumulation of neuronal cell bodies
- in the brain, grey matter is found in the cortical layer and deep structures of the brain, also in brainstem (cranial nerve nuclei)

• in CNS collection of neuronal cell bodies are called nuclei
• in PNS collection of neruonal cell bodies are called gangia
• in the spinal cord grey matter is found centrally surrounded by white matter

Question 12

what is white matter?

what are tracts?

Answer 12

white matter is the sum of all fibre tracts.
axons are mostly myelinated and therefore appear more white than grey matter.

a tract is a bundle of axons travelling from one area to another.
a tract in the PNS is called a nerve

Question 13

what is the telencephalon?

Answer 13

the telecephalon is composed of a huge cerebrum, which is divided into cerebral hemispheres. they are covered by grey matter. deep to the grey matter are structures which include:

- basal ganglia
- limbic system structures (hippocampus and amygdala)

Question 14

what is the diencephalon?

Answer 14

the diencephalon is formed from the prosensephalon and forms the caudal end of the forebrain. it consists of the thalamus, hypothalamus and subthalamus

Question 15

what are the four lobes of the cerebral hemispheres?

Answer 15

• frontal
• parietal
• occipital
• temporal

plus the limbic lobe…

Question 16

what is the frontal lobe?

- anatomical position

Answer 16

the frontal lobe is the largest lobe of the brain. it is located anteriorly and separated from the parietal lobe by the cental sulcus (groove) and the temporal lobe by the lateral sylvian fissure.

Question 17

what is the frontal lobe?

- contents and functions

Answer 17

in the frontal lobe, anterior to the central sulcus is the precentral gyrus that contains the primary motor areas.

• lateral and medial areas regulate voluntary motor activity (also initiate)
• also broca motor speech area

remainder of frontal lobe consists of prefrontal association areas

• motivation, emotion, personality, initiative, judgement, social inhibitions and ability to concentrate
• congulate gyrus on medial surface is important in modulating emotional aspects of behaviour.

Question 18

what is the parietal lobe?

- anatomical position

Answer 18

the parietal lobe is separated from the frontal lobe by the central sulcus, and from the temporal lobe by the lateral sylvian fissure, and from the occipital lobe by the parietooccipital fissure

Question 19

what is the parietal lobe?

• contents
• functions (3)

Answer 19

the parietal lobe contains the postcentral gyrus, posterior to the central sulcus. the postcentral gyrus is the primary somatosenory area of the cortex.

the parietal lobes are important in regulating somatosensory functions

1. inital cortical processing and perception of touch, pain and limb position (lateral and medial aspects of parietal lobe)
2. sensory aspects of language
3. aspects of spacial orientation and perception

Question 20

what is the occipital lobe?

- anatomical position

Answer 20

the occipital lobe is separated from the parietal lobe by the parietooccipital fissure

located posteriorly

Question 21

what is the occipital lobe?

- contents and functions

Answer 21

the occipital lobe is primarily involved in processing visual information
primary visual area is located on either side of the calcarine sulcus in the medial surface.

the calcarine sulcus joins the parietooccipital fissure

the occipital lobe mediates the ability to see and recognise objects.

Question 22

what is the temporal lobe?

- anatomical position

Answer 22

the temporal lobe is separated from the frontal and parietal lobes by the lateral sylvian sulcus and from the occipital lobe by a line drawn extending the parietaloccipital fissure

Question 23

what is the temporal lobe?

- contents and functions

Answer 23

the temporal lobe is important for auditory processing

the superior temporal gyrus is the area of hearing and the interpretatiopn of sound

the lateral surface functions for perception of language

the medial (anterior) aspects are important for learning, memory and emotion.

Question 24

what is the limbic lobe?

Answer 24

the limbic lobe, although not an actual lobe of the cerebral hemisphere but formed from parts of frontal, parietal and temporal lobes. (the cingulate and the parahippocampus gyri)

the limbic lobe is a ring of cortex on the medial side, which overlie and is interconnected with limbic system structures.

Question 25

what gyri make up the limbic lobe?

Answer 25

- cingulate | - parahippocampus

Question 26

what is the ventricular system?

Answer 26

the ventricular system is a fluid-filled space within the brain. it is comprised of the: - lateral vetricles - 3rd ventricle - cerebral aqueduct - 4th ventricle - spinal canal cerebral spinal fluid circulates within the ventricles.

Question 27

what is CSF?

Answer 27

cerebral spinal fluid, circulates around the ventricular system, secreted from ependymal cells of the choroid plexus.

Question 28

describe the circulation of CSF...

Answer 28

``` csf fills the ventricles and subarachnoid space in the brain and spinal cord. continuous production (500ml per day) drives the CSF to circulate. ``` CSF moves from the lateral ventricles to the 3rd to the 4th ventricles. from the 4th ventricle the outflow is through the two lateral foramina of Luschia and through the medial foramen of Magendie (posterior) intot he subarachnoid space, also to the central canal of the spinal cord. in the subarachnoid spacecisterns are evident. CSF moves posteriorly around the spinal cord and then back up anteriorly. circulating until it reaches the arachnoid granulations that protrude into the superior sagital venous sinus. where it is reabsorbed

Question 29

where is CSF produced?

Answer 29

CSF is produced by the choroid plexuses and small amount by ependymal cells.

Question 30

where are the main choroid plexuses found? | what is the structure of choroid plexus?

Answer 30

choroid plexuses are found int he lateral ventricles and 4th ventricles. choroid plexus is a 3 layered structure: 1. fenestrated endothelium of choroid arteries 2. pial layer 3. specialised ependymal cells

Question 31

how is CSF reabsorbed?

Answer 31

CSF is reabsorbed by the superior sagittal venous sinus through arachnois granulations. reabsorption id driven by a pressure gradient. pressure is less in the venous sinus that the arachnoid granulations and so CSF enters the sinus.

Question 32

what is the sturcture of the lateral ventricle?

Answer 32

the lateral ventricle are associated with the telencephalon. a lateral ventricle is found in each cerebral hemisphere. lateral ventricle is C shaped and conforms to the curvature of the brain. 3 horns: - anterior horn: deep in the frontal and parietal lobes - posterior horn: extends into the occipital lobe - inferior horn: in the temoral lobe (hippocampus is found in the floor of the inferior horn of the lateral ventricle)

Question 33

what connects the lateral ventricle to the 3rd ventricle?

Answer 33

the intraventricular foramen of Monroe connects the lateral ventricles with the 3rd ventricle

Question 34

what separates the two anterior horns of the lateral ventricles?

Answer 34

the sepum pelucidum separates the anterior horns of the lateral ventricles on the medial surface

Question 35

what is the 3rd ventricle associated with and what connects it to the 4th ventricle?

Answer 35

the 3rd ventricle is associated with the diencephalon (thalamus and hypothalamus located on either side of the ventricle) the 3rd ventricle is connected to the 4th ventricle by the cerebral aqueduct.

Question 36

what are the spaces between the meninges?

Answer 36

there is only one true meningeal space: subarachnoid space the subarachnoid space is filled with CSF and is between the pia mater and arachnoid mater. other meningeal spaces may develop: - subdural space: arachnoid and dura - epidural space: drua and bone although in the spinal cord a true epidural space exists between dure (only single layer in spinal cord) and peristeum of verebrae. this space is filled with fatty tissue andf the certebral venous plexus.

Question 37

what are the sources of blood to the brain:

Answer 37

brain blood supply is from 2 sources: 1. internal carotid 2. vertebral arteries