Slide 1 : Our Nervous system
Organization of the Nervous System : Organization of the Nervous System BBIPL
Nervous System : Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Sensory Neurons Motor Neurons Somatic Nervous System
voluntary movements via skeletal muscles Autonomic Nervous System
organs, smooth muscles Sympathetic
- “Fight-or-Flight” responses Parasympathetic
- maintenance Nervous System The Nervous System BBIPL
Organization of the Nervous System : Motor (efferent) division
Somatic nervous system = voluntary
Autonomic nervous system = involuntary Organization of the Nervous System Figure 7.2 BBIPL
Central Nervous System : Central Nervous System CNS protection
Bone: skull and vertebrae
Meninges: dura mater, arachnoid, and pia mater
Cerebrospinal fluid: carries nutrients and waste for CNS Blood-brain barrier:
Spinal cord: relays information through nerve tracts in white matter BBIPL
Slide 6 : CENTRAL NEURAL SYSTEM
The central neural system can be compared to the central processing unit (CPU) of a computer.
It regulates all sensory and motor impulses.
It comprises the brain and the spinal cord. BBIPL
BRAIN : BRAIN Brain containing billions of neurons and weighing 1.5 kg is protected by the cranium or brain box of the skull.
It is covered by three protective membranes called meninges,
outer layer of dura mater,
middle layer, arachnoid and
the inner pia mater. BBIPL
Slide 8 : Skin Galea Aponeurotica Connective Tissue Bone Dura Mater Arachnoid mater
Slide 9 : BBIPL
Duramater : Duramater The outermost dura mater is made up of white fibrous connective tissue rich in collagen.
It has poor blood supply.
Below this meninx (singular of meninges) is a subdural space filled with cerebrospinal fluid (CSF). BBIPL
Dura Mater : Dura Mater Tough and leathery.
Most superficial.
2 layers:
Periosteal ? attached to the skull
Meningeal ? true external covering, extends downward and surrounds spinal cord BBIPL
Slide 12 : In several locations, the inner dura mater extends in to the cranial cavity, forming a sheet that dips inward and then returns.
These dural folds provide additional support for the brain.
Dural sinuses may be found between the 2 layers of a dural fold. BBIPL
Arachnoid and Pia Mater : Arachnoid and Pia Mater Arachnoid
Loose spider-web of connective tissue.
Beneath it is the subarachnoid space – filled with blood vessels and CSF
Maintains intracerebral pressure
Pia
Deepest and most delicate
Covers the brain tissue
Follows its every ridge and groove
It is dark black due to pigments of melanin BBIPL
CSF : CSF The cerebrospinal fluid is a colourless, alkaline transparent fluid.
It functions as a shock absorber, drainage of metabolites, nutrition and oxygen supply to the brain.
Fills the space between the arachnoid and pia mater, as well as the internal cavities of the brain (ventricles) and spinal cord (neurocoel). BBIPL
Choroid plexus : Choroid plexus A choroid plexus consists of a combination of specialized epednymal cells and permeable capillaries called telechoroidea for the production of CSF.
2 extensive folds originate in the roof of the 3rd ventricle (located btwn the lateral walls of the diencephalon) and extend through the interventricular foramina and cover the floors of the lateral ventricles.
A region of choroid plexus is also found in the 4th ventricle between the cerebellum and pons. BBIPL
Cerebrospinal Fluid : Functions:
Shock absorption
Support
Nourishment Cerebrospinal Fluid BBIPL
CSF : CSF Ependymal cells selectively secrete capillary filtrate into the ventricles.
They also remove waste products from the CSF and adjust its composition over time. CSF differs markedly from blood in its [soluble protein] and cellular content.
About 500mL of CSF is produced per day.
The total volume of CSF at any given moment is 150mL
CSF circulates from the choroid plexus thru the ventricles and the central canal of the spinal cord.
As it circulates, there is unrestricted diffusion between it and the ISF of the CNS. BBIPL
Neurocoel : BBIPL Neurocoel
Slide 19 : CSF reaches the subarachnoid space through 2 lateral apertures and a single median aperture in the roof of the 4th ventricle. CSF then flows through the subarachnoid space surrounding the brain, spinal cord, and cauda equina
Along the axis of the superior sagittal sinus, fingerlike extensions of the arachnoid membrane, called arachnoid villi, penetrate the dura. In adults, clusters of villi form arachnoid granulations. CSF is absorbed into the general circulation at the arachnoid granulations
Arachnoid membrane : Arachnoid membrane The arachnoid membrane is highly vascular and folded into arachnoid villi (or Pacchionion bodies).
These act as phagocytes. BBIPL
Pia mater : Pia mater The pia mater is the innermost thin meninx.
It is rich in blood supply and black in colour due to presence of melanin pigments.
It is firmly attached to grey mater of the brain.
Lower vertebrates upto birds have pia-arachnoid membrane also called leptomenings
Inflammation of the meninges caused by virus, bacteria or fungi is called meningitis and can be fatal. BBIPL
Slide 22 : BBIPL
PARTS OF BRAIN : PARTS OF BRAIN The brain can be divided into three major parts
1. Forebrain (prosencephalon)
2. Midbrain (mesencephalon) and
3. Hindbrain (rhombencephalon) BBIPL
BRAIN PARTS : BRAIN PARTS BBIPL
Slide 25 : BBIPL
Brain: Processes and Acts on Information : Brain: Processes and Acts on Information Forebrain: receives and integrates information concerning emotions and conscious thought
Hypothalamus: helps regulate homeostasis
Thalamus: receiving, processing, and transfer center
Limbic system: neuronal pathways involved in emotions and memory
Cerebrum/cerebral cortex: higher functions as intelligence and logic BBIPL
Brain: Major Divisions : Brain: Major Divisions Hindbrain: coordinates basic, automatic, vital functions
Medulla oblongata: controls automatic functions of internal organs
Cerebellum: coordinates basic movements in relation to gravity
Pons: aids flow of information BBIPL
Hindbrain, Midbrain : Hindbrain, Midbrain Midbrain: coordinates muscles related to vision and hearing BBIPL
FOREBRAIN : FOREBRAIN The forebrain can be further divided into telencephalon (rhinencephalon and cerebrum) and diencephalon (thalamus and hypothalamus). BBIPL
Rhinencephalon : Rhinencephalon Rhinencephalon or olfactory lobe forms the
centre of olfaction.
The size of this lobe represents the olfaction ability of the organism.
In frog It is poorly developed
Whereas in Sharks and carnivore mammals it is best developed.
Its inner cavity is known as rhinocoel in lower vertebrates as frog where it is well formed.
The first pair of cranial nerves are asssociated with this part. BBIPL
Cerebrum or cerebral hemisphere : Cerebrum or cerebral hemisphere It is the biggest part in brain occupying about 1/3 to 2/3 of total brain.
Out of 10 billion neurons in the human brain over 9 billions are in the cerebral cortex alone.
There are fissures/Sulci in cerebrum :
i. Longituidinal fissure
Appears first in amphibians and divides cerebrum into two
cerebral hemispheres.
Mammalian brain
Has additional sulci in each of cerebral hemisphere dividing each hemispheres into lobes
1. Frontal lobe
2. Parietal lobe
3. Temporal lobe
4. Occipital or Hippocampal lobe BBIPL
Exceptional sulci of mammalian brain : Exceptional sulci of mammalian brain The additional sulci in mammalian brain are:
i. Central sulcus = Fissure of Rolando
It separates the frontal lobe from parietal lobe.
ii. Lateral sulcus = Fissure of Sylvius
This separates the frontal and parietal lobe from temporal.
iii. Parieto-occipital sulcus
This separates parietal and temporal lobe from occipital. BBIPL
Basal Ganglia : Basal Ganglia Deep within the cerebral hemispheres are group of nerve cells known as basal ganglia or nuclei.
These nuclei act as relay stations, a place of synapses which occur between ascending and descending nerve fibres.
These basal ganglia are separated from thalamus by internal capsule.
This region has control on the voluntary muscular movements of the body.
It helps in coordination and control of fine movements such as necessary for lifting a pen. BBIPL
Slide 34 : Corpus Callosum Parietal Lobe Choroid Plexus Occipital Lobe Cerebellum Spinal Cord Medulla Oblongata Pons Temporal Lobe Pituitary Gland Hypothalamus Frontal Lobe Third Ventricle Lateral Ventricle Mid Brain Thalamus Fourth Ventricle Mid Brain Cerebellum Choroid Plexus Optic Chiasma Inter mediate Mass of the Thalamus Pineal Gland Central Sulcus Gyrus Cerebrum Sulci BBIPL