The Central Nervous System Brain and Spinal Cord
The Central Nervous System Brain and Spinal Cord
Anatomy • The Central Nervous System is divided into two parts the brain and the spinal cord • Brain - (1. 4 -1. 4 kg) about 3 lbs. • 100 billion nerve cells • Spinal Cord is about 45 cm long
• Composed of 3 layers of connective tissue • Dura mater - thick and tough. • Arachnoid - thin, delicate membrane. Cerebrospinal fluid located in space between Arachnoid and Pia mater. • Pia mater - very thin, vascular membrane, adheres to brain and spinal cord. The Meninges
• About 135 m. L of this clear liquid fills the ventricles of the brain and subarachnoid spaces around the brain and spinal cord. • 99% water, also glucose, salts, protein and urea. • Produced by the choroid plexus, a network of capillaries which project from the pia mater into the ventricles. Cerebrospinal fluid
• CSF is produced by the choroid plexus in the ventricles of the brain. • Circulates through subarachnoid spaces of the brain and spinal cord • Cushions the brain and spinal cord. • Absorbed by the arachnoid granulations in blood sinuses in the brain.
• Capillaries near the brain have very tight junctions which restricts the materials that can pass through and be absorbed. • Glucose, amino acids, O 2, Ca+2 and erythromycin pass easily into the brain. • Urea, insulin and penicillin, pass very slowly • Many drugs used in treating tumors of the brain cannot pass through this barrier. Blood Brain Barrier
• Most inferior part of the brainstem. • Consists of white matter (nerve fibers) and gray matter (nerve cell bodies) • Controls heart rate, blood pressure and breathing. • Also controls vomiting, sneezing, coughing and swallowing. Medulla Oblongata
• The Pons (#3) is a bulge on the ventral surface of the brainstem. • Functions as a link connecting various parts of the brain. • Helps to regulate respiration. • Also serves as a center for reflexes of the face. • Helps control chewing and eye movements, facial expression, taste and equilibrium Pons
• Extends from the Pons about 2 cm. • In many vertebrates this is the largest brain region. • In humans most of its functions have been assumed by the cerebrum. • Functions: pupil response to light, turning head to hear sound and righting reflexes
• Also known as the epiphysis. • Functions as an endocrine gland • Secretes melatonin, may influence onset of puberty in humans. Pineal Body
Thalamus • Consists of two oval masses of gray matter covered by a thin layer of white matter • Functions as a major relay center for all sensory information, except smell, to the cerebrum.
• Forms the walls of the third ventricle. • Most important relay station between the cerebral cortex and the lower autonomic centers. • Link between brain and pituitary gland. • Maintains fluid balance, is the thirst center. • Regulates body temperature, hunger and sexual behavior
Cerebellum
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