1 / 42
420 likes | 429 Vues
Central Nervous system, Brain and its parts, Peripheral and Autonomous Nervous system, Reflex action, Glands and their hypo-secretion and hyper-secretion
E N D
Brain • It is one of the largest organs in the body, and coordinates most body activities. • It is the center for all thought, memory, judgment, and emotion. • Each part of the brain is responsible for controlling different body functions, such as temperature, regulation and breathing.
Cerebrum • It is the largest section of the brain. • It is located in the upper portion of the brain and is the area that processes thoughts, judgment, memory, problem solving, and language. • The outer layer of the cerebrum is the cerebral cortex, which is composed of folds of gray matter. • The cerebrum is subdivided into the left and right halves called cerebral hemispheres. Each hemisphere has 4 lobes.
Lobes of Cerebrum • Frontal lobe: Most anterior portion of the cerebrum, controls motor function, personality, and Speech • Parietal lobe: The most superior portion of the cerebrum, receives and interprets nerve impulses from sensory receptors and interprets language. • Occipital lobe: The most posterior portion of the cerebrum, controls vision. • Temporal lobe: The left and right lateral portion of the cerebrum, controls hearing and smell
Cerebellum • Second largest portion of the brain • Located beneath the posterior part of the cerebrum • Aids in coordinating voluntary body movements and maintaining balance and equilibrium/posture • Refines the muscular movement that is initiated in the cerebrum
Brain Stem • Midbrain—acts as a pathway for impulses to be conducted between the brain and the spinal cord. • Pons — means bridge—connects the cerebellum to the rest of the brain. • Medulla oblongata—most inferior positioned portion of the brain; it connects the brain to the spinal cord.
Spinal Cord • Runs through the vertebral canal • Center for reflex action • Passes impulses to the brain • Extends from foramen magnum to 2nd lumbar vertebra • Regions • Cervical • Thoracic • Lumbar • Sacral • Coccygeal • Gives rise to 31 pairs of spinal nerves - all are mixed nerves
Peripheral Nervous System • The second nervous system, known as the peripheral nervous system, contains all the nerves in the body that lie outside of the spinal cord and brain. • These two systems communicate with each other to make sure our body parts, such as our fingers, can send signals to the central nervous system for processing in our brains • The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. • Some of those nerve pairs are exclusively sensory cells, such as cells that detect information like smell and vision. • Others are exclusively motor cells, like the eyeballs. • Also, there are nerve pairs that have both sensory and motor cells, such as those involved in taste and some aspects of swallowing. • Sensory cells carry messages to the central nervous system. • Motor cells carry the signal from the central nervous system to the internal organs, muscles, and glands in the periphery or the outer edges of the body.
Cranial nerves • Cranial nerve, in vertebrates, any of the paired nerves of the peripheral nervous system that connect the muscles and sense organs of the head and thoracic region directly to the brain i.e. to and from the brain. • In higher vertebrates, there are 12 pairs of cranial nerves: • Olfactory , Optic, Oculomotor , Trochlear, Trigeminal, Abducent (or abducens), Facial, Vestibulocochlear, Glossopharyngeal , Vagus, Accessory, and Hypoglossal. • Cranial nerves are made up of motor neurons, sensory neurons, or both. • They have their origin in the brain.
Spinal nerves • Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. • In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. • Each pair connects the spinal cord with a specific region of the body. • Near the spinal cord each spinal nerve branches into two roots. • One, composed of sensory fibers, enters the spinal cord via the dorsal root; its cell bodies lie in a spinal ganglion that is outside the spinal cord. • The other, composed of motor fibers, leaves the spinal cord via the ventral root; its cell bodies lie in specific areas of the spinal cord itself.
Autonomic Nervous System • The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system. • The somatic nervous system is under voluntary control, and transmits signals from the brain to end organs such as muscle. • The Autonomic nervous system is a 'self-regulating' system which influences the function of organs outside voluntary control, such as the heart rate, or the functions of the digestive system. • Autonomic nerve cells are divided into three separate divisions: • The parasympathetic division is involved with slowing body functions i.e. re-establishes normal condition after violent act is over. • Sympathetic division increases body functions i.e. prepare body for violent action against abnormal conditions. • They normally oppose each other i.e. antagonistic. • The enteric division is involved with all the functions in the gastrointestinal areas, such as the pancreas and the gallbladder.
Neuron/Neurone/Nerve cell • The structural and functional unit of nervous system • Sensory neurons get information about what's going on inside and outside of the body and bring that information into the CNS so it can be processed. • Motor neurons get information from other neurons and convey commands to your muscles, organs and glands. • Interneuron or connector, which are found only in the CNS, connect one neuron to another. They receive information from other neurons (either sensory neurons or interneuron) and transmit information to other neurons (either motor neurons or interneuron).
Reflex action • For instance, if you picked up a hot coal, the signal from the sensory neurons in your fingertips would travel to interneuron in your spinal cord. Some of these interneuron would signal to the motor neurons controlling your finger muscles (causing you to let go), while others would transmit the signal up the spinal cord to neurons in the brain, where it would be perceived as pain. • This process commonly called reflex action. • A reflex, or reflex action, is an involuntary and nearly instantaneous movement in response to a stimulus. • The pathway along which nerve impulse travel during the reflex action is called reflex arc.
Reflex arc Relay neuron or
Glandular System • A group of cells that helps in secretion of hormones is called gland. • Exocrine and Endocrine glands. • Exocrine secretes enzymes and endocrine secrets hormones. • Hormones: group of chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Characteristics of hormones: • They are transported to the target cells/ tissue/organ via circulation. • Their actions are specific. Some have generalized role. • They are active in very minute quantities. • They usually activate target cells by forming hormone receptor complex. • They are low in molecular weight. • They are destroyed after their actions. • Their excess or deficiency may lead to serious consequences.
Hormones • Hormones are molecules produced by the endocrine system that send messages to various parts of the body. • They help regulate your body's processes, like hunger, blood pressure, and sexual desire. • They regulate three basic processes: division, enlargement and differentiation of cells. • Whilehormones are essential to reproduction, they are fundamental to all the systems of your body. • Hormones are called chemical messengers because they are chemical agents that travel around the body to tell specific cells to perform a specific action. The term hormone describes a variety of chemicals that perform these signaling tasks.
Pituitary gland • This gland hangs from the base of the midbrain. • It is also called master gland. • It has two parts: an anterior lobe and a posterior lobe. • The anterior lobe produces the growth hormone which stimulates the growth of the body. • The posterior lobe produces oxytocin hormone which stimulates contraction of the uterus in a pregnant women. • The deficiency of the growth hormone leads to dwarfism in children. • Over activity of the growth hormone leads to gigantism in the young and acromegaly in the adults (gorilla-like appearance).
Thyroid gland • This gland is bi-lobed, and is situated in front of the neck below the larynx. • This gland secretes a hormone, known as thyroxin, which regulates the rate of metabolism in the body and also effects the general growth of the body. • If this gland is under active (Hypo-secretion) it results in the formation of swelling in the neck, which is called goitre. • Over secretion (Hyper-secretion) of this gland may also cause another type of goitre called Exopthalmic goitre and rapid heartbeat with shortness of breath and increased metabolic rate.
Parathyroid hormone • These are four small glands located on each side of the thyroid gland at the base of the neck. • Produces Parathormone(PTH) hormonewhich regulates calcium and phosphorous metabolism and proper development of bones. • Hyposecretion: Hypocalcaemia (Ca deficiency, tetany- intense spasm of muscles) • Hypersecretion: Kidney stones, gall stones
Adrenal gland • This gland is cap-like structure located on each kidney. • This gland produces adrenalin hormones: • Corticoids: secondary sexual characters • Hyposecretion: Addison’s disease • Hypersecretion: abnormal sexual maturity in early age (Adrenal virilism) • Adrenalin: prepare for emergency conditions • Hyposecretion: Weakness, low blood pressure, unconsciousness • Hypersecretion: High blood sugar, Hypertension • It also regulates salt and water balance in the body.
Pancreas • Pancreas is ductless gland as well as a duct gland i.e. mixed gland • Pancreas contains special cells called the Islets of langerhans. These are of two types: Alpha-cells and Beta-cells. • Alpha cells secrete glucagon, which stimulates the break-down of glycogen into glucose in the liver. • The beta-cells secrete the insulin hormone which controls absorption of glucose by the body cells. • Hypo secretion of insulin leads to diabetes mellitus • Hyper secretion of insulin leads to insulin shock (coma if sugar level falls drastically)
Sex glands/Gonads • Sex glands are the testesin the male and ovary in the female. • The testes produce testosterone hormone which controls the development of the male sex organs and secondary sexual characteristics. • Ovaries produces: • estrogen hormone which controls secondary sexual characters like mammary gland, menstrual cycle, etc • progesteronehormone, which controls the enlargement of uterus walls and enlargement of mammary glands during pregnancy.
