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- 1. ANATOMY & PHYSIOLOGY WEEKLY Volume 1, Issue 2 10.29.12 Dura mater: made of strong white fi- ment. Functions: The spinal cord per- brous tissue, serves as the outer layer of forms two general functions. the meninges and also as the inner peri- Where is it found : cerebrospinal Briefly, it provides conduction osteum of the cranial bones. fluid is found in the subarachnoid routes to and from the brain and space around the brain and spi- serves as the integrator, or reflex Arachnoid membrane, a delicate, coweb nal cord within the cavities and center, for all spinal reflexes (2) like-layer, lies between the dura matter canals of the brain and spinal and the pia matter or innermost layer of cord. Which are called ventricles the meninges Spinal cord: the spinal cord lies Pia matter: innermost layor of the menin- in the spinal cavity, extending ges. The transparent pia matter adheres from the foramen magnum to the to the outer surface of the brain and spi- lower border of the first lumbar nal cord and contains blood vessels vertebra, a distance of about 45 cm in the average body. The Cerebrospinal fluid: In addition to its bony spinal cord does not completely and membranous coverings, nature has fill the spinal cavity. further protected the brain and spinal cord against injury by providing a cushion of fluid both around the organs and within them, it also a reservoir of circulating fluid that, along with blood, the brain monitors for changes in internal environ- © (12) © (12) © (12) © (12) © (12) © (12) Inside this Issue CNS 1,2,3 Page 1 PNS 5,6,7,8 Page 2 CNS 4,5,6 Page 3 CNS 7,8,9 Page 4 PNS 1,2,3,4 Page 5
- 2. Page 2 ANATOMY & PHYSIOLOGY WEEKLY purpose of the sympathetic nervous Inside the peripheral The autonomic nervous system is to prepare the body for nervous system there are system functions inde- physical activity. The purpose of the two subdivisions, the so- pendently and without parasympathic nervous system is to matic nervous system conscious effort. Afferent active vegetative functions such as and the autonomic nerv- nerves are the sensory digestion, defecation, and urination. ous system. The auto- nerves that travel away (1) nomic nervous system from the central nervous includes fibers that con- system and efferent nect the CNS to viscera, nerves are the motor such as the heart, stom- nerves that travel toward ach and glands. Within the central nervous sys- the automatic nervous tem. As a whole the Auto- system it is divided into nomic Nervous System another two parts the sends impulses from the sympathetic nervous sys- central nervous system to tem and the parasym- smooth muscle, cardiac pathic nervous system. muscle, and glands. The Autonomic Nervous System “The autonomic © (12) function functions independe ntly” Efferent nerves Afferent nerves travel travel toward the away from the CNS CNS © (12)
- 3. VOLUME 1, ISSUE 2 Page 3 © (12) The ance. Brainstem functions as our own the cerebrum. Inferior privet is located at the lower part of cerebellar peduncles The Thalamus and the Hypothalmus are also im- the brain directly connected to the composed cheifly if reacts portant to the brainstem. The thalamus is a dumb- spinal cord. The brainstem is like into the cerebellum from bell shaped mass of grey matter that makes up the spinal cord, performs sensory, the medulla and cord. many nuclei. They play two parts in the mecha- motor, and reflex functions. It is the Middle CP are composed nism responsible for sensation. pathway for all fiber tracts passing almost entirely of tracts It impulses from appropriate up and down from peripheral nerves into the cerebellum from receptors, on reaching the thal- and spinal cord to the upper areas the pons, that is, ponto- mus, produce conscious recog- of the brain. The Medulla Oblongata cerebellar tracts. Superior nition of the crude,less crtical is a relay station for the crossing of CP is composed to princi- sensation of pain, temperaure motor tracts between the spinal pally of tracts from den- and touch. The neurons whose cord and the brain. It also contains tate nuclei in the cerebel- dendrites and cell bodies lie in the respiratory, motor and cardiac lum through the red nu- certain nuclei of the thalamus functions, as well as several mech- cleous of the midbrain to relay all kinds of sensory im- anisms of reflex activities such as the thalamus. The func- puses. Plays a part in the coughing, swallowing and vomiting. tions of the cerebellum is mechanism responsible for The midbrain is the nerve pathway that they perform three emotion, in the arousal or alert- of the cerebral hemisphere and general functions that has ing machanism and a part in contains auditory and visual reflex to deal with the control of the mechanism that produce centers. The pons is the area that skeletal muscles. They complex reflex movements. It links different parts of the brain and act with the cerebral cor- is involved in regulation of the seves a relay station from the me- tex to produce skilled homeostatic control. Neuroen- dulla to the higher cortical struc- movements by coordinat- docrine role in conjunction with tures of the brain. ing the activities of groups the pituitary gland as well as by its influence on the os muscles. They help the autonomic nervous system, which helps regu- The Cerebellum is the second larg- control posture. It func- late body temperature, the cardiovascular system, est part of the brain. A transverse tions below the level of and food and water intake. fissure separates the cerebellum consciousness to make from the cerebrum. The Gyri of the movements smooth. They cerebellum are much more slender also control the skeletal and less prominent than those of muscles to maintain bal-
- 4. VOLUME 1, ISSUE 2 Page 4 Somatic Motor Pathways con- Secondary sensory neurons conduct Cerebral Cortex sists of motor neurons that con- from the cord/brainstem up to the thala- duct impulses from the central mus. The cerebrum is the largest and nervous system to somatic effec- uppermost division of the brain, con- tors. Tertiary sensory neurons conduct from sist of two halves, the right and left the thalamus to the post central gyros of cerebral hemispheres. The set of coordinated com- the parietal lobe, the somatosensory mands that control the pro- area. Composed of gray matter grammed muscle activity mediat- ed by extrapyramidal pathways is Each side of the brain registers sensa- often called a motor program. tions from the opposite side of the brain. Functions of Cerebral Cortex Crude touch and pressure sensations are functions of the spin thalamic path- Consciousness, language, emotion Somatic Sensory Pathways way. and memory are also all controlled by the cerebral cortex Primary sensory neurons of the relay conduct from the periphery Mechanisms that control voluntary to the central nervous system. movements are extremely complex and imperfectly under- stood (1) © (12) © (12) © (12)
- 5. Page 4 At each skin surface area supplied by sensory fibers of a given spinal Cranial Nerves- Connect nerve is called a dermatome, a name that means “skin section”. (2) to the undersurface of the brain, mostly on the © 12 brainstem. There are 12 different cranial nerves: (2) Olfactory (sensory) Optic (sensory) Oculomotor (Motor) A Myotome is a skeletal muscle or Trochlear (Motor) group of muscles that receives mo- Trigeminal (Mixed) tor axons from a given spinal nerve. (2) Abducens (Motor) Facial (Mixed) The Ventral rami of most spinal nerves—all but nerves T2 through Vestibulocochlear T12--- subdivide to form complex (Sensory) networks called Plexuses. (2) Glossopharyngeal Each of the 31 pairs of spinal nerves (Mixed) exits the spinal cavity from the inter- Vagus (mixed) vertebral foramina. The names of © 12 the vertebrae are given on the left Hypoglossal (Motor) and the names of the corresponding spinal nerves on the right. (2) © 12 © 12 © 12