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Brain
- The brain is composed to 100 billion neurons
- Neurons communicate with each other or with other organs through synapses formation
- Divide into four major portions:
- Cerebrum-decision making
- Diencephaon-
- Brain stem-
- Cerebellum-
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The cerebrum
- The brain is made of two hemispheres:
- Right and left
- there are five lobes within the cerecral hemisphere:
- frontal
- parietal
- temporal
- occipital
- insula
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Frontal lobe (commands; motor lobe)
- Forms the anterior portion of each cerebral hemisphere
- Location of the primary motor cortex
- Stimulate skeletal muscles
- Reasonable for speech production
- Function in concentration, planning and problem solving
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Parietal lobe
- Located posterior to the frontal lobe
- Central sulcus separates the parietal lobe from the frontal lobe
- Receives sensory information from the skin
- Understanding speech
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Temporal lobe
- Located below the frontal lobe and parietal lobes
- Function in receiving auditory stimuli
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Occipital lobe
- forms the posterior portion of cerebral hemisphere
- Important in visual stimuli
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Diencephalon
- Made of two regions
- Thalamus
- hypothalamus
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Thalamus
- central relay station for sensory impulses
- It receives all sensory information except the sense of smell
- Channels all the inputs into the proper region of the brain
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Hypothalamus
- Regulates heart rate and blood pressure
- Body temperature
- Water and electrolytes balance
- Control of hunger and body weight
- Controls the secretion of the posterior pituitary gland
- Sleep and wakefulness
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Midbrain
- Contains the corticospinal tract responsible for connection between the cortex and spinal cord
- Contains ceners for visual reflex and auditory reflex
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Pons
- Located below the midbrain
- Contains respiratory centers
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Medulla oblongata
- Contains cardiac center
- Heart rate
- Vasomotor center
- Stimulate smooth muscles arround blood vessels
- Affects blood pressure
- Respiratory center
- Regulates respiratory center
- (Sneezing, coughing, swallowing, vomiting center)
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Cerebellum
- Located below the occipital lobe
- Consists of two lateral hemispheres
- Communicates with various parts of the cerebrum
- Provides coordination of skeletal muscle movements
- Integrates balance information
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Ventricles of the brain
- The brain contains interconnected cavities called ventricles
- The cavities contain a fluid called the cerebrospinal fluid
- Lateral ventricle, third ventricle, and fourth ventricle
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How does the cerebrospinal fluid circulate in the bran?
- From the lateral ventricle, CSF ciculates through the interventricle foramen to the third ventricle
- From the third ventricle, the CSF goes to the fourth ventricle via the cerebral aqueduct
- From the fourth ventricle, CSF travels through the central canal to the spinal cord and to the subarachnoid space
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Function of cerebrospinal fluid
- Supports and protect the brain by acting as a shock absorber
- Maintain a stable ionic concentration
- Provide a pathway of waste products to the blood
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Protection of the brain
- The brain controls every function in the body and therefore must be heavily protected from trauma and injury
- there are four levels of protection:
- Skull
- Meninges
- Cerebrospinal fluid
- Blood brain barrier
- Skull
- Four major bones
- Frontal
- Parietal
- Temporal
- Occipital
- Bones are connected together by strong fibrous suture joint
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Meninges
- Have three layers
- Dura matter-
- Tough white fibrous connective tissue
- Contains many blood vessels
- Archnoid
- Thin membrane without blood vessels
- Pia
- Very thin membrane that contains blood vessels to nourish underlying nervous tissue
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Blood brain barrier
- Chemical protection made of tight capillary network that prevents many chem and toxic material from passing to the brain
- However it is not a complete barrier
- It permits oxygen, glucose, anesthetic & alcohol to pass through to the brain
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Spinal cord
- Slender nerve column that passes from the brain at the level of foramen magnum
- Consists of 31 segments where 31 pairs of spinal nerves originate
- Tapers and terminates at l1-l2
- Have two enlargements that give rise to nerves
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Anatomy of the spinal cord
- Protected by vertebral column
- Surrounded by three layers of the meninges
- Roots extend to become spinal nerves
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Cross section of the spinal cord
- Anterior median fissure is a groove that divides the spinal cord into right and left halves
- Central gray matter is surrounded by white matter
- Upper and lower wings of the gray matter are called posterior and anterior
- Lateral horn is located laterally on the gray matter
- White matter is divided into anterior, lateral, and posterior finiculi
- The CSF circulates in the central canal
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Function of the spinal cord
- The amterior horn contain cell bodies of motor neurons
- Posterior and lateral horns contain interneurons
- The white matter contain nerve tracts
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Ascending tracts
- Spinothalamic tract
- Carry information from the spinal cord to the thalamus
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Descending tract
- Corticospinal tract
- Originates in the cortex of the brain and carries electrical signals to skeletal muscles
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