Lesson 11-12: Sensory and Motor Nerve Endings, Endocrine System PDF

LESSON 11 SENSORY AND MOTOR NERVE ENDINGS Efreim Louie Sombillo-Ilano,RN, MSN, MD, FIAMS, MHA  I. SOMATOSENSORY SYSTEM General Senses: 1. Light touch or tactile discrimination 2. Pressure 3. Touch 4. Pain 5. Temperature 6. awareness of limb position and...

LESSON 11 SENSORY AND MOTOR NERVE ENDINGS Efreim Louie Sombillo-Ilano,RN, MSN, MD, FIAMS, MHA  I. SOMATOSENSORY SYSTEM General Senses: 1. Light touch or tactile discrimination 2. Pressure 3. Touch 4. Pain 5. Temperature 6. awareness of limb position and motion  SOMATOSENSORY RECEPTORS: 1. Receptors: Function: a. Meissner corpuscles touch b. Hair follicle receptors touch c. Merkel’s tactile disc touch d. Ruffini’s corpuscle heat e. Krause end bulb cold f. Free nerve endings pain g. Pacinian corpuscle pressure g. Muscle spindle proprioception h. Tendon organ tendon proprioception  GENERAL SENSE PATHWAYS A series of three neurons transmit the touch system impulses from the receptors in the periphery to the cerebral cortex, where these sensations are perceived. 1. First order neuron: also called sensory neuron or N1 2. Second order neuron or association neuron: N2 3. Third order neuron: N3  ASCENDING FIBER TRACTS 1. Anterolateral system A. Lateral spinothalamic tract – for pain and temperature except head region B. Anterior spinothalamic tract – for crude touch/ light touch /light pressure except head region 2. Pathways to the Cerebellum For Unconscious Proprioception A. Anterior Spinocerebellar tract B. Posterior Spinocerebellar tract both A and B carry information to the cerebellum from the lower limbs C. Cuneocerebellar tract Carries information to the cerebellum from the upper limbs  3. Dorsal Column/ Lemniscal system : For conscious proprioception : Deep pressure and discriminative touch : Vibratory sense : Position sense : Stereognosia (ability to recognize familiar objects by touch with the eyes closed)  CLINICAL SIGNS OF INJURY TO THE LEMNISCAL PATHWAY: 1. Inability to recognize limb position. 2. Astereognosia: inability to identify an object by touch with eyes closed. 3. Loss of vibration sense. 4. Loss of two point discrimination. 5. Positive Rhomberg’s sign: abnormal increase in the degree of body sway with eyes closed  II. MOTOR SYSTEM 1. Pyramidal System 2. Extrapyramidal System A. Pyramidal system: mainly concerned with the production of skilled voluntary movements a. Corticospinal tract: Anterior / Lateral b. Corticobulbar tract  CLINICAL CORRELATION A. Upper motor neuron lesion occurs when there is damage to the pyramidal tract along its path Manifestations: Spastic paralysis Hyperreflexia Positive Babinski sign Atrophy from disuse only Negative fasciculations  B. Lower motor neuron lesion involves the anterior horn cells of the spinal cord and the motor nuclei of cranial nerves. Manifestations: Flaccid paralysis Hyporeflexia Negative Babinski sign Marked atrophy Positive fasciculations and fibrillations  C. Extrapyramidal System: Network of interconnections of various parts of cerebral cortex and several subcortical centers ( including thalamus, basal ganglia, and cerebellum), with major pathways to spinal motor neurons arising from reticular formation. Functions include: 1. Regulation of actions of pyramidal system for smooth coordinated movements. 2. Production of automatic movements (smiling, gesticulating). 3. Production of unconscious adjustment in postures and muscle tone.  LESSON 12 ENDOCRINE SYSTEM  Made up of widely distributed organs whose secretion (hormone) reaches target tissues or organs through its specific receptors via the bloodstream. Hence the system is called the duct-less system.  I. PITUITARY GLAND (HYPOPHYSIS CEREBRI) Lies in the sella turcica of the sphenoid bone and attaches to the hypothalamus by a stalk, the infundibulum. It is a pea shaped structure measuring 1-1.5 cm in diameter and is composed of two lobes: a. Anterior lobe (adenohypophysis) b. Posterior lobe (neurohypophysis  A. Anterior lobe (Adenohypophysis) - Makes up 75% of the total weight of the gland. - Hormones: 1. Human growth hormone (hGH) or somatotropin Stimulates several tissues to secrete insulin like growth factors, hormones that stimulate general body growth and regulate aspects of metabolism. 2. Thyroid stimulating hormone (TSH) or thyrotropin Controls the secretion and activities of the thyroid gland  3. Adrenocorticotropic hormone (ACTH) or corticotropin Stimulates the adrenal cortex to secrete glucocorticoids. Some corticotrophs also secrete melanocyte-stimulating hormone (MSH) 4. Follicle stimulating hormone, 5. Luteinizing hormone (LH) (FSH) FSH & LH are gonadotrophic hormones which regulate the functions of the gonads (ovaries & testis) 6. Prolactin (PRL) Helps initiates and maintains milk secretion by the mammary gland  B. Posterior lobe (Neurohypophysis) Does not synthesize hormones. Instead stores and releases two hormones. Secretions from this lobe are produced by the cell bodies of the supraoptic nucleus (produces vasopressin or antidiuretic hormone/ADH) and the paraventricular nucleus (produces oxytocin) of the hypothalamus and are moved by axonal transport to the axon terminals in the posterior pituitary.  II. PINEAL GLAND (EPIPHYSIS CEREBRI) Located at the caudal end of the diencephalon of the brain. Consists of cells called pinealocytes. Hormone secreted: Melatonin derived from serotonin, which may promote sleepiness  Hormones stored in neurohypophysis: A. Oxytocin - enhances smooth muscle contraction in the walls of the uterus during delivery, it stimulates milk ejection (“letdown”) from the mammary glands in response to the mechanical stimulation provided by the suckling infant. B. Antidiuretic hormone – conserves body water by decreasing urine volume; decreases water loss through perspiration; raises blood pressure by constricting arterioles.  IV. PARATHYROID GLANDS 2 pairs of yellowish glands closely related to the posterior surface of the thyroid gland Secretes parathormone, which directly elevate blood calcium levels  V. ADRENAL (SUPRARENAL) GLANDS A pair of glands resting on top of each kidney 2 layers: 1. Adrenal Cortex Secretions: A. Mineralocorticoids (aldosterone and deoxycortisones) Regulate fluids and electrolytes help adjust blood pressure and blood volume  III. THYROID GLAND - Located in the lower part of the anterior neck , with a pair of lobes connected in the midline by an isthmus - Contains follicles, which secrete 2 thyroid hormones: thyroxine and triiodothyronine - Actions of thyroid hormones: 1. Increase basal metabolic rate 2. help maintain normal body temperature - Also secretes thyrocalcitonin secreted by the parafollicular cells which helps regulate calcium homeostasis  B. Glucocorticoids (e.g. cortisone) - Regulate metabolism and resistance to stress C. Androgens- Promote libido in females and are converted to estrogen, also stimulate growth of axillary and pubic hairs in boys and girls and contribute to the prepubertal growth spurt  2. Adrenal Medulla Secretes the cathecolamines, epinephrine and norepinephrine. Produces effects that enhance those of the sympathetic division of the autonomic nervous system during stress  VI. PANCREAS - pistol shaped flattened organ , the head part of which is enclosed by the duodenum, the body at the back of stomach and tail related with spleen. - the endocrine portion of the pancreas consists of the cells of the Islets of Langerhans scattered among the exocrine acini  Cell populations found in the pancreatic islets: 1. Alpha cells Produce glucagons, which increase blood glucose levels when it falls below normal. 2. Beta cells Produce insulin, helps lower blood glucose levels when it is too high 3. Delta cells Produce somatostatin which inhibits secretion of insulin and glucagon and slows absorption of nutrients from the gastrointestinal tract 4. F cells Secrete pancreatic polypeptides  GONADS are the organs that produce gametes sperms in males and oocytes in females. The female gonad is the ovary, a pair of oval bodies located in the pelvic cavity. The male gonad, the testes are oval glands that lie in the scrotal sac  VII. TESTES - The interstitial cells of Leydig in the testes secretes these androgens: 1. Testosterone 2. Dehydrotestosterone 3. Androstenedione Its main hormone testosterone regulates production of sperm and stimulates the development and maintenance of masculine secondary sex characteristics such as beard growth and deepening of the voice.  VIII. OVARIES The follicular cells of the ovarian follicle secrete estrogen and the corpus luteum secretes progesterone. These hormones regulate the female reproductive cycle. Regulate oogenesis, maintain pregnancy, prepare the mammary gland for lactation and promote development and maintenance of female secondary sex characteristics.  SELECTED DISEASES AFFECTING THE ENDOCRINE GLANDS: 1. Grave’s Disease autoimmune disorder associated with increased circulating levels of thyroid hormones 2. Diabetes mellitus disorder of metabolism and chronic hyperglycemia  3. Cushing’s Syndrome - refers to the manifestations of excessive corticosteroids, eg. Central obesity, moon face, buffalo hump, osteoporosis, hypertension, hyperglycemia.  4. Addison’s disease -disorder caused by the destruction of the adrenal cortices characterized by chronic deficiency of cortisol, aldosterone and androgens causing skin pigmentation QUESTION S?