Nervous system 3 Flashcards
The Brain
Develops from bulges of a neural tube and has to fold within the available space as it grows faster that the surrounding membranous skull
Protective coverings of the brain
The brain is protected by the skull and cranial meninges:
- Dura mater(top), sup
- Arachnoid mater(middle)
- Pia mater(bottom)
The spinal meninges are organized similarly
Dura Mater
- the strongest one
Has 2 layers - the periosteal layer is only found in the brain
- the meningeal layer extends into the spinal cord
The 2 layers fuse together except at the dural venous sinuses which collects venous blood from the brain and empties it into jugular veins of the neck
Subdural space has serous fluid
Arachnoid mater
- Subarachnoid space has cerebrospinal fluid(CSF) and major blood vessels that supply the brain
- Archnoid granulations drain CSF back k to the venous blood and protrude into the superior sagittal venous sinus in dura mater
Pia mater
- attaches tightly to the brain
- contains small blood cells that perfuse the brain
The blood brain barrier(BBB)
Separates capillary blood from the brain to maintain a stable internal environment
BBB:
Which 3 structures form the BBB?
- Tight junctions between the endothelium
- Thick basement membrane
- Astrocyte feet’s and perioytes
True or False
All brain tissues are guarded by the blood brain barrier
False:
It is absent around the vomiting centre of the brain stem, so that it can monitor the blood for poisonous substances.
And around the hypothalamus, so that it can monitor the chemical composition of the blood and adjust water balance
Cerebral Spinal Fluid(CSF)
- produced by a specialized capillary network called the choroid plexus
- ependymal cells surround choroid plexus capillaries to filter blood and produce CSF
Key functions:
Supports the brain as it floats in the skull
Protects the brain
Exchanges nutrients and wastes
Maintains electrolyte balance
Ventricles
CSF is transported in a ventricular system which are cavities in the brain
The are 4:
- 2 within the cerebral hemispheres called right/left v
- 1 b/w the cerebellum and the medulla pons(brain stem) called fourth v
1 within the hypothalamus and thalamus called third v
The CSF circulates through all of the following locations, except:
A. Subarachnoid space
B. Central canal of the spinal cord
C. Cerebral aqueduct
D.Subdural space
E. Choroid plexus
D
Brain matter
White matter: mostly myelinated axons
Gray matter: cell bodies and dendrites, some non-myelinated axons and neuroglia
How are white and great matter organized in the brain, brain stem and spinal cord?
Spinal cord: inner gray matter surrounded by outer white matter.
Brain stem: inner gray matter and muclei scattered within outer white matter.
Brain (cerebrum and cerebellum):
reversed inner white matter
surrounded by outer gray matter.
• some gray matter nuclei are found within white matter
Regions of the brain
The adult brain has:
1. Cerebral hemipheres(cerebrium)
2. Diencephalon
3. Cerebellum
4. Brain stem
Cerebrium
- largest part of the brain
- divided into left and right cerebral hemispheres connected by a band of white matter called the corpus callosum
The primary somatosensory cortex and primary motor cortex each contains a homunculus which represents sensory input and motor output from different body parts
Cerebrum:
Each has
A cerebral cortex(superficial grey matter)
Internal white matter
Basal nuclei(deep grey matter dots)
Cerebrum:
Cerebral Cortex
- is the state of conscious mind
It contains foldings:
Gyrus-ridges
Sulcus- shallow groove
Fissure- deeper groove
What does longitudinal fissure seperate?
The left and right central hemispheres
What does the transverse cerebral fissure seperate?
The cerebellum and cerebrum
Each lobe of the brain is associated with specific functional areas:
- Sensory areas: process conscious awareness of sensation.
- Motor areas: control voluntary movement.
- Association areas: integrate information from diverse areas.
True or False
A primary sensory cortex breaks down sensory input into components, while an association cortex makes sense of these sensory inputs
True
Cerebral Cortex:
The functional areas of each lobe
Frontal: Taste areas that overlaps with the temporal lobes, motor areas that are voluntary and motor speech
Parietal: general sensory for cutaneous sensations
Temporal: Auditory and olfactory areas
Occipital: visual areas
The primary somatosensory cortex and primary motor cortex each
contains a homunculus.
each contain a homunculus which represents the sensory input and motor output from different body parts
True or False
Cerebral dominance describes the hemisphere that is dominant for handedness
False:
Cerebral dominance describes the hemisphere that is dominant for language. About 90% of humans have left-sided dominance.
Lateralization
Both hemipheres aren’t identical
• The left hemisphere controls language, math, and logic.
• The right hemisphere controls visual-spatial skills, intuition, emotion, and artistic and musical skills.
They communicate through the white matter fibre tracts.
Cerebral White Matter
Classified depending on the direction they go
Association fibres: connect diff parts of the same hemisphere(horizontally)
Commissural fibres: connect 2 hemipheres(left and right)
Projection fibres: connect higher brain to lower or spinal cord(up and down)
Basal Nuclei
are embedded deep in the brain (subcortical).
The major structures include:
• the striatum
• globus pallidus
Basal Nuclei:
Functions
- regulates muscle tone
- regulates intensity of slow or repetitive movements
- filters out incorrect or inappropriate movements
- inhibits antagonistic or unnecessary movements
Parkinson’s and Huntington’s are associated with this
Cerebral Blood Flow
the heart, carotid and vertebral arteries connect at the base of the brain to form the cerebral arterial circle(circle of Willis)
- the benefit of the circular design of this is is that it provides a redundant blood supply and constant perfusion of the brain
Cerebral blood flow
Veins drain into the dural venous sinuses
- found in dura mater
- csf is also returned to the dural venous sinuses through arachnoid granulations
