The Human Brain Flashcards
Human CNS structure is…
Tubular
During development the structure expands and there is differential growth at rostral(top) and caudal(bottom) ends
What happens days after fertilisation Days: 19 20 22 26
19- flat cells with neural plate
20- neural groove
22- neural crest
26 - tube formed as 2 sides touch and fuse
Neural tube defects
Cause
Defects caused by caudal and rostral failure to close
Caused by lack of folic acid
Rostral end fails - anencephaly
Caudal end fails - spina bifida
Primary brain vesicles
Define vesicles
Name 4 primary divisions
Vesicles - fluid-filled swelling at rostral end of the neural tube
Prosencephalon
Mesencephalon = midbrain
Rhombencephalon = hindbrain (m and m)
Spinal cord
(Early vesicles grow and expand differentially)
Secondary brain vesicles
Flexicons and outpocketings continue Structures:(top to bottom) Telencephalon Optic vesicle Diencephalon Metencephalon- pons and cerebellum Myelencephalon - medulla oblongata Spinal cord
Telencephalon + diencephalon = forebrain
M and m = rhombencephalon split in 2 (pontine flexure is the bend between the 2)
Spinal cord transverse section shows..
Protection?
Type of nerve roots that extend from spinal cord?
Transverse section shows: white and grey matter(process/ neuronal cell bodies) around a central canal
Protection - encased in bony vertebrae
Nerve roots:
Dorsal roots - Carry sensory input
- swelling = dorsal root ganglion
Ventral roots - Carries motor commands out
- no swelling
(Neuronal cell bodies in ganglion)
Spinal cord interneuron are important when?
Where do they connect between?
Important for reflexes– can be ipsilateral or contra lateral = allows reflexes on both sides (coordination)
Between sensory and motor neurons
Spinal cord columns
Facts about pathways?
What is decussation and where does it happen?
Pathways run up and down? Bilateral ascending and descending pathways
Pathways have multiple connections and many cross over
Decussation - cross over like Roman numeral X
Happens in the medulla for motor cortex
Meninges of spinal cord
Define
3 types
Cord is protected by layers of membrane
1) pia mater - closest to spinal cord
2) arachnoid
3) dura mater - furthest form spinal cord (fibrous protective sheath)
- -continuous with those of the brain–
Meninges of the brain
What happens to pia mater, Arachmoid and dura mater?
Dura sinus?
Pia stays Arachnoid stays Dura splits into 2: 1) endosteal layer (periosteal) 2) meningeal layer 'Dura sinus' - large vein like structures
Cerebrospinal fluid flows where?
What are aperture?
Use of CSF?
Sampling CSF?
Disorders of CSF?
Flows in central canal, brain ventricles and subarachnoid space
Aperture - holes that allow fluid formed on inside to get to subarachnoid space
CSF floats and cushions CNS
If you lose CSF = can reduce blood flow
Sampling - lumbar puncture
Needle inserted between 3rd and 4th lumbar vertebrae (no spinal cord here)
Disorders - hydrocephalus
Internal = increase in intra cranial pressure- causes cell death due to reduce in blood flow
External = pressure externally
Blood- brain Barrier?
Separates circulating blood from brain extra cellular fluid
Physiological barrier:
- capillary endothelial cells
- tight junctions connect endothelial cells
- astrocytes
Coronal plane
Transverse plane
Midsaggital
Coronal plane - frontal plane
Transverse plane - horizontal
Midsaggital - saggital and parasagittal (cut corpus callosum)
4 divisions of brain
Brain stem
Cerebellum
Diencephalon
Cerebrum
What 3 parts make up the Brain stem?
Key facts about brain stem?
Medulla oblongata
Pons
Mesencephalon
Fibre tracts and ‘housekeeping’ nuclei
Ascending and descending tracts
Decussation
Reticular formation occurs in brain stem
Medulla oblongata major features?
Fibre tracts
Nuclei - CVS, respiration
Olives - cerebellum
Nerve roots
Large lesions? = death due to no respiratory rhythm
The pons major feature?
Bridges side of cerebellum
Connects to cerebellum via peduncles
Respiratory centres
Fibre tracts
The cerebellum
structure?
Roles?
Cerebellular ataxia?
Folia
Layers - molecular layer, purkinje cell layer, granule layer, white matter
Deep nuclei
White matter = arbar vitae
roles– muscle tone, coordination, motor error correcting, learning
Cerebellular ataxia– loss of cerebellar neurons = jerky imprecise movements
Mesencephalon or midbrain
Cerebral peduncles
Tectum- superior and inferior colliculi
- visual(superior) and auditory(inferior) reflexes
Substantia nigra - the black substance
(Associated with Parkinson’s due to role in the regulation of movement)
Nucleus ruber - red nucleus
Diencephalon
Part of what part of brain?
What does it link?
Contains?
Part of forebrain
Links midbrain and cerebrum
Contains: thalamus, hypothalamus and pineal
Thalamus– processing and relay centre- all special senses, except smell -synasthesia– motor role, arousal, higher functions
Hypothalamus– eating, drinking, sexual behaviour, stress
Pineal – endocrine organ, melatonin and serotonin
The cerebrum
How many hemispheres?
What are the bumps and grooves called? (And what are they for)
Identify the 6 lobes
2 hemispheres
Gyri and fissure(to increase SA)
Frontal, parietal, occipital, temporal (on surface)
Central(insula), limbic
Cerebral cortex
What is the outer cortex surrounding?
Name the 3 structures within the cerebral cortex
White matter and deep nuclei
2 lateral ventricles
Wall = much thicker for an adult
Lots of structures and groupings of neurons e.g.striatum
1.Caudate nucleus, 2.putamen, 3.global pallidus
1+2= aka corpus striatum
2+3 = aka lentiform nucleus
Cortical structures
How thick?
Layers of what?
How many layers of cells below white matter? Name them
V thin- 3-mm of cells
Layers of neocortex(not all areas of cortex in same in structure)
Generally 6 layer of cells below white matter:
- Molecular layer
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal pyramidal layer
- Fusiform layer
How was mapping done?
Brodmann’s area
Phineas gage
Brocas aphasia
Wernickes aphasia
Modern mapping
Mapping by lesion(pathologist approach) and direct stimulation (anatomical approach)
B area- cytoarchitecture (allowed people to predict what could happen if damage occurred in certain areas)
Phineas gage - damaged frontal lobe= personality change
Brocas - inability to produce speech sound, left frontal lobe damage, expressive aphasia, impaired speech
Wernickes- posterior temporal lobe damage, language comprehension ruined, receptive aphasia= fluent but inappropriate wording
PET scanners, MRI, regional blood flow
Reading =visual cortex lights up(wernickes and Broca’s area)
Association cortex - most cortical area (receives input from many source+ modalities)
– so brain can compile and understand info
Lateralisation
Left hemisphere?
Right hemisphere?
Why differences in function?
Left - speech, calculation, analysis
Right- spatial, conceptual, artistic
Due to?
Differential gene expression, gender diff, nature vs. Nurture
Basal ganglia
What is it?
Where?
Function
4 structures in it?
Type of nuclei
Deep within hemispheres
Movement regulation so problem = huntingtons or Parkinson’s
1) striatum –caudate and putamen
2) globus pallidus
3) subthalamic nucleus
4) substantia nigra(mesencephalon) – linked due to function not anatomically
Limbic system
Function?
4 structures?
Memory and emotions
1) limbic lobe (6th lobe)
2) hippocampus and amygdala
3) thalamus and hypothalamus
4) reticular formation
Hippocampus associates in limbic system due to roles in:
Memory, emotions and motivation
Cerebral fibre tracts
What are they?
3 types of fibres?
Pathways and projections
Association fibres - link areas within a hemisphere
Commissural fibres - connect between hemispheres (fewer in males)
Projection fibres - link to non-cortical areas (leave the cerebral hemispheres)
