Week 2 -neural plate Development of the Central Nervous System (CNS) Week 3 -neural groove Week 4 -neural tube (ice cream cone view) 1. Prosencephalon - 2. Mesencephalon - 3. Rhombencephalon - Week 5 -brain sections 1. Telencephalon- - -hollow space = 2. Diencephalon -interbrain ( ) -diencephalons, thalamus, hypothalamus, epithalamus -hollow space = 3. Mesencephalon- -brain stem: midbrain -hollow space = 4. Metencephalon-after brain -brain stem: -hollow space = 5. Myencephalon-spinal brain -brain stem: medulla oblongata -hollow space = 6. Spinal cord -spinal cord -spinal cord -hollow space =
After week 5, brain begins to curve and bend because it's growing faster than skull Week 6 Week 13 Cerebrum ( ) Diencephalon ( ) Brain stem midbrain ( ) pons ( ) medulla oblongata ( ) Spinal cord ( ) Cerebellum ( ) Birth 1. Cerebrum Frontal lobe Parietal lobe Occipital lobe Temporal lobe 2. Diencephalon 3. Brain stem Midbrain Pons Medulla Oblongata 4. Cerebellum 5. Spinal Cord
FUNCTIONS OF MAJOR BRAIN AREAS 1. Cerebral Hemispheres A. Sensory input B. Voluntary motor output C. Intellect, reasoning, problem-solving 2. Diencephelon A. Relays information to cerebrum B. Controls ANS C. Emotions 3. Brain Stem (midbrain, pons, medulla oblongata) A. Relays information to cerebrum B. Reflex centers 4. Cerebellum A. Relays info about voluntary muscles to primary motor cortex B. Coordinates skeletal muscles (balance, posture)
BRAIN FEATURES I. Cerebrum features A. left and right hemispheres midsagittal cut B. gyrus and convolution part of the folds that stick up C. fissures and sulci depressions, deep or shallow respectively D. parietal lobe - top E. temporal lobe - side F. frontal lobe - front G. occipital lobe - back H. longitudinal fissure divides hemispheres I. transverse fissure divides cerebrum from cerebellum J. lateral sulcus divides parietal lobe from temporal lobe K. central sulcus divides parietal lobe from frontal lobe L. parieto-occipital sulcus divides parietal lobe from occipital lobe M. precentral gyrus convolution anterior to central sulcus N. postcentral gyrus convolution posterior to central sulcus O. corpus callosum largest commissure (connection) between the hemispheres. Allows them to communicate. P. primary motor area controls voluntary muscle movements - located in the precentral gyrus Q. primary sensory area receives information from voluntary muscles. Located in the postcentral gyrus R. fornix small commissure (connection) between diencephalons halves. involuntary information. S. premotor area memory for repetitive motor skills T. speech or Broca s area lateral frontal lobe U. visual area occipital lobe V. auditory area temporal lobe W. taste area - parietal lobe X. olfactory area frontal lobe
II. Diencephalon Features A. thalamus gateway to the cerebrum, relays information B. hypothalamus main visceral control center in the body - ANS, emotions, body temp, food intake, water balance, digestion 1. pituitary gland a main endocrine gland in body 2. infundibulum- stalk of the pituitary gland 3. mammillary body- relay for olfactory information C. epithalamus found above the thalamus 1. pineal body- makes melatonin which helps regulate sleep/wake cycles III. Cerebellum features A. cerebellar hemispheres coordinates body movements B. arbor vitae the pattern of white matter resembling a tree IV. Brain Stem Features A. Midbrain features 1. corpora quadrigemina large nuclei or group of cell bodies a. superior colliculi visual reflex centers (blinking) b. inferior colliculi auditory reflex centers(startle reflex) B. Pons features 1. pons means bridge and it is the bridge between the motor cortex and the cerebellum C. Medulla oblongata features 1. medullary reflex centers a. cardiovascular - cardiac and vasomotor b. respiratory rate and depth of breathing c. other reflexes sneeze, hiccup, vomit, swallow, cough
PROTECTIVE STRUCTURES OF THE CENTRAL NERVOUS SYSTEM I. Bone 8 cranial bones II. Membranes = - functions to protect CNS and blood vessels. Also contains CSF In order from outside in A. tough mother thick outside membrane B. small space between dura and arachnoid C. spider mother thin middle weblike membrane D. places were CFS enters blood E. larger space between arachnoid and pia filled with CSF F. soft mother thin inner membrane that adheres to the brain and spinal cord PAD III. Cerebrospinal fluid (CSF) - functions to cushion, protect, and nourish the brain A. Makes CSF B. membrane that separates lateral ventricles C. one in each hemisphere D. connects lateral to 3 rd ventricle E. around thalamus F. connects 3 rd to 4 th ventricles G. bordered by cerebellum H. holes by cerebellum that connect venticle CSF to CSF in the subarachniod space I. - holes by cerebellum that connect venticle CSF to CSF in the subarachniod space J. hollow middle of spinal cord
IV. Blood Brain Barrier 1. Function 2. Why? Fluctuations in concentrations of hormones, amino acids, and ions in the blood would affect the neurons in the brain and cause them to fire uncontrollably. Particularly after exercise or eating. 3. Looks like 3 layers A. Capillary wall - epithelium with tight junctions B. Thick basal lamina C. Astrocytes hold capillary to neuron 4. Characteristics A. Selective rather than absolute barrier B. Nutrients ( ) move by facilitated diffusion from blood to CSF C. Ineffective against metabolic wastes, proteins, fats, gases, most chemicals (exceptions - ) 5. Exceptions A. Choroid plexus, 3 rd ventricle, and 4 th ventricle no barrier B. Vomiting center monitors poisons C. Hypothalamus regulates water balance D. Newborns haven t developed yet, can t fight toxins like adults
SPINAL CORD 1. Begins 2. Ends A. Conus medullaris - B. Filum terminale - C. Cauda equina - 3. Length 17 inches 4. Width ¾ inch (diameter of pinky finger or 5 th digit) except A. Cervical enlargement B. Lumber enlargement 5. Protection ( same as brain) A. Bone B. Membranes C. CSF 6. Clinical Application - Cross-section of spinal cord 1. Fissures A. Anterior median fissure B. Posterior median fissure 2. Gray matter butterfly-shaped A. Location deep to white matter B. Commissure - C. Posterior horn Interneurons (receive info from sensory nerves) D. Lateral horn Autonomic motor neurons ( ) send info out to visceral organ E. Anterior horn Somatic motor neurons ( ) send info out to skeletal muscles 3. White matter A. Location superficial to gray B. Posterior column ascending tracts ( ) C. Lateral column ascending and descending tracts D. Anterior Column ascending and descending tracts 4. PNS branches A. Dorsal root sensory ( ) fibers B. Dorsal root ganglion sensory cell bodies (motor are located in spinal cord) C. Ventral root motor ( ) fibers D. Spinal nerve ventral and dorsal roots meet (mixed nerve)
Peripheral Nervous System Nerves as organs - cordlike organ - consists of peripheral axons wrapped in connective tissue and surrounded by endoneurium (loose connective tissue) A. 2 main types of PNS nerves 1. 2. B. 3 functional types of PNS nerves 1. Sensory nerve ( ) nerves that carry impulses to CNS 2. Motor nerves ( ) nerves that carry impulses away from CNS 3. Mixed nerves nerves containing both sensory and motor fibers C. 2 locational types of PNS nerves 1. Visceral autonomic nerves 2. Somatic skeletal muscles We can combine these together S.A. S.E. V.A. V.E.
Sense receptors of touch a. Free dendritic endings found - everywhere especially C.T. - function b. Nociceptors found - everywhere especially C.T. - function c. Pacinian corpuscles found everywhere especially C.T. - function d. Merkel discs found - germinativum layer of epidermis - function e. Root hair plexus found hair follicle - function f. Messners corpuscles found dermal hairless skin, (soles of feet, fingertips, genitalia) - function g. Muscle spindles found skeletal muscles - function h. Golgi tendon organs found tendons - function The Spinal Reflex Arc - reflex defined as a predictable automatic response to changes Reflex arc components 1. Receptor of stimulus 2. Sensory neuron entering via dorsal root with cell body in dorsal root ganglion 3. Synapse (directly with motor neuron or with interneuron) 4. Motor neuron exiting via ventral root with cell body in ventral gray horn 5. Effector ( ) responds
Spinal Nerves 31 pairs of nerves - all are mixed - dorsal and ventral root join to make spinal nerve A. Naming spinal nerves - named from point of entry into/out of spinal cord - top 7 spinal nerves located above same bone name - rest of spinal nerve located below same bone name cervical spinal nerves (one more than number of bones) thoracic spinal nerves lumbar spinal nerves sacral spinal nerves coccygeal spinal nerve Example - 3 rd cervical nerve - 5 th lumbar nerve B. Naming the plexuses After exiting from the intervertebral foramen, branching occurs. The dorsal branch extends to innervate skin and muscles of the back; anterior or ventral branch to muscles and skin of the front of trunk and limbs. With exception of the thoracic region, the anterior branch forms network (plexus) fibers of spinal nerves and are sorted and recombined. FINAL RESULT: although the point of origin of the spinal nerve may differ, fibers for a particular part of the body meet in the same nerve. 1. found deep in neck from C1-4, serves skin and muscles of head and neck, diaphragm connects with some cranial nerves. 2. found within shoulder between neck and armpit from C5- T1 serves upper extremities, parts of neck and shoulders 3. located within muscle that tilts pelvis from L1-L4 serves part of lower extremities, external genitalia 4. found on posterior wall of pelvic cavity from L5-S4 serves buttocks, perineum (between pubic area and anus in both sexes), and rest of lower extremities
Cranial Nerves Number Saying Name S/M/B Function 1 2 3 4 5 6 7 8 9 10 11 12
CHARACTERISTIC AUTONOMIC N.S. SOMATIC N.S ALSO CALLED EFFECTOR OR TARGET ORGAN # NEURONS IN PNS TO EFFECTOR EFFERENT PATHWAYS 1 ST NEURON IN EFFERENT PATHWAY 2 ND NEURON IN EFFERENT PATHWAY CONDUCTION SPEED NEUROTRANSMITTER EXAMPLE
AUTONOMIC NERVOUS SYSTEM CHARACTERISTIC ALSO CALLED Sympathetic (Emergency, stress) Parasympathetic (Non-emergency) FUNCTION ORIGIN OF NERVES LOCATION OF MOTOR GANGLIA NAME OF GANGLIA LENGTH OF AXONS BRANCHING NEURO- TRANSMITTER NERVE FIBER OR AXON NAME
EFFECT ON ORGAN/SYSTEM HEART Sympathetic (Emergency, stress) Parasympathetic (Non-emergency) BLOOD VESSELS RESPIRATORY DIGESTIVE EYE PUPILS SKELETAL MUSCLES URINARY GLANDS ARRECTOR PILI MUSCLE LIVER CELLULAR METABOLISM MENTAL ACTIVITY
SHORT STRESSED SUZY HAS 2 THICK CHAINS Short Stressed Suzy 2 Thick Chains *General increase in activity to skeletal muscles, decrease in activity to digestive system and other systems Passive Polly thinks gangs are very achy and terminal Passive Polly Achy Terminal *General resting nervous system, digestion and other systems are functioning normal, and skeletal muscle activity decreases