Organisation Of The Nervous System 2 Flashcards
The volume of the adult human brain ranges from
750ml to 2100ml
The adult human brain contains almost
97 percent of the body’s neural tissue
The average weight of the adult human brain is
About 1.4kg (3lb)
The brain size varies
Considerably amongst individuals
The brain of males are, on average, about ten percent larger than those of females due to
Differences in average body size
What are the six regions of the brain?
Cerebrum Cerebellum Diencephalon Midbrain Pons Medulla oblongata
The cerebrum is
The largest part of brain
The cerebrum controls
Higher mental functions
The cerebrum is divided into
Left and right cerebral hemispheres
The brain has an extensive area of
Neural cortex, a layer of grey matter covering most of its surface
Neural cortex is also called
Cerebral cortex
This cerebral cortex forms a series of:
- Elevated ridges (gyri), that serves to increase its surface
- The gyri are separated by shallow depressions called sulci
- Or by deep groves called fissures
The cerebellum is the
Second largest part of the brain
The cerebellum coordinates repetitive body movements by
Adjusting ongoing movements by comparing arriving sensations with previously experienced sensations, allowing you to perform the same movements over and over
The cerebellum has
Two hemispheres
Like the cerebrum, the cerebellum has hemispheres that are covered
By a layer of grey matter, the cerebellar cortex
The diencephalon is located
Under cerebrum and cerebellum
The diencephalon links cerebrum to
Brain stem
There are three divisions of the diencephalon:
- Left thalamus
- Right thalamus
- Hypothalamus
Thalamus: each contains relays and processing centres for
Sensory information
The hypothalamus aka the floor of the diencephalon contains centres involved with
Emotions, autonomic function, and hormone production
In the diencephalon there is a
Pituitary gland
The pituitary gland is a
Major endocrine gland and is connected to the hypothalamus via infundibulum (narrow stalk)
The hypothalamus and the pituitary gland are responsible for
The integration of the nervous and endocrine systems
The diencephalon is a
Structural and functional link between the cerebral hemispheres and the components of the brain stem
The brain stem processes information between
Spinal cord and cerebrum or cerebellum
The brain stem includes:
Midbrain
Pons
Medulla oblongata
The midbrain also called the mesencephalon processes
Sight, sound and associated reflexes
The midbrain contains nuclei that
Process visual and auditory information and control reflexes triggered by these stimuli
The midbrain maintains
Consciousness
Pons connects cerebellum to brain stem and contains
Nuclei involved in somatic and visceral motor control
The medulla oblongata connects brain to spinal cord and
Relays sensory information to the thalamus and to centres in other portions of the brain stem
The medulla oblongata regulates autonomic functions
Heart rate
Blood pressure
And digestion
The brain is a
Large, delicate mass of neural tissue
Each of the six major brain regions has specific functions ascending from
The medulla oblongata to the cerebrum, brain functions become more complex
The brain is involved in
Conscious thought and intelligence and these are produced in the neural cortex of the cerebral hemispheres
Physical protection of the brain involves
Bones of the cranium
Cranial meninges
Cerebrospinal fluid
Biochemical isolation is
The blood-brain barrier
The cranial meninges have three layers:
- Dura mater
- Arachnoid mater
- Pia mater
The cranial meninges are continuous with
Spinal meninges
The cranial meninges protect the brain from
Cranial trauma
The dura mater of the cranial meninges has
Inner fibrous layer (meningeal layer)
Outer fibrous layer (periosteal layer) fused to periosteum
Venous sinuses between two layers
The arachnoid mater of the cranial meninges covers
Brain providing smooth surface that does not follow brains underlying folds
The arachnoid mater contacts
Epithelial layer of dura mater and there is a subarachnoid space between arachnoid mater and pia mater
The pia mater of the cranial meninges is attached to
Brain surface by astrocytes
The Duran folds are the
Folded inner layer of dura mater and extend into cranial cavity
The rural folds
Stabilise and support the brain and contain collecting veins (dural sinuses)
The three largest dural folds are
- Falx cerebri
- Tentorium cerebelli
- Falx cerebelli
cerebrospinal fluid (csf) surrounds
All exposed surfaces of CNS
The functions of the CSF include
Cushions delicate neural tissue
Supports brain
Transports nutrients, chemical messengers and waste products
In essence the brain is suspended inside the cranium and
Floated in the CSF. A human brain weighs about 1400g (3.9lb) in air but only about 50g (1.8oz)when supported by CSF
Cerebrovascular disease is
Disorders that interfere with blood circulation to brain e.g stroke or cerebrovascular accident (CVA)
Stroke or CVA occurs when
The blood supply to a portion of the brain is shut off and affected neurons begin to die in a matter of minutes
Blood-Brain Barrier
Isolates CNS neural tissue from general circulation
The BBB is formed by
Network of tight junctions between endothelial cells of CNS capillaries
Only lipid-soluble compounds (02, c02), steriods and small alcohols can
Diffuse into interstitial fluid of brain and spinal cord
What are astrocytes?
Cells that are in close contact with CNS capillaries and control blood-brain barrier
What is one of the ways astrocytes control blood-brain barrier?
Releasing chemicals that control permeability of endothelium so these cells play a key supporting role in the blood-brain barrier
If astrocytes are damaged or stop stimulating the endothelial cells,
The blood-brain barrier disappears
The blood-CSF barrier is
Formed by special ependymal cells
The blood-CSF limits movement
Of compounds transferred
Blood-CSF barrier allows
Chemical composition of blood and CSF to differ
The meninges stabilise the position of the
Brain within the cranial cavity
Cerebrospinal fluid provides
Protection against sudden jolts and shocks
CSF provides
Nutrients and removes wastes
Blood-brain barrier and blood-CSF barrier selectively isolate
Brain from chemicals in blood that might disrupt neural function
Many water-soluble molecules that are abundant in the blood occur in small amounts or not at all in the extra cellular fluid of the brain. Why?
Many water-soluble molecules are rare or absent in the extra cellular fluid (ECF) of brain because the blood-brain barrier regulates the movement of such molecules from the blood to the ECF of the brain
