Nervous system and Endocrine system
By Jake Robertson, Rhiana Richardson and Jacob Shelton
Brain and Spinal Cord
Cerebellum - The cerebellum controls posture, co-ordination and balance. Also in the cerebellum, there is is folia, bulndled nerve cells. The brain stem is located directly below the cerebellum.
Brain Stem - The lowest part of the brain is located in the brain stem, the meddula oblangata/ Directly above the meddule oblangata are the pons. The pons is the band of nerves that connect the cerebrum, the cerebellum, and the meddula oblangata.
Sensory Neurons and Motor Neurons
Sensory Neurons - The function of the five senses: touch, smell, taste, sound and sight. It sends the 'instructions' to the central nervous system, the brain and spinal cord. It sends the 'message' to the brain, which sends the 'instructions' back to the body part needing it.
Motor Neurons - These transmit umpulses from the central nervous system to the muscles and glands that then carry out the response.
Receptors and Their Uses
Somatosensory Receptors - These receptors detect noxious or painful stimuli.
Meissner Corpuscles - These receptors detect touch to the skin.
Muscle Spindles - These types of receptors respond to the stretch or pulling of the muscles.
Tendon Organs - These respond to tension of muscles or excessive lengthening of the muscle.
Pacinian Corpuscles – These receptors sense vibrations in the body.
Glands of the Endocrine System and their Hormones
Thyroid - The thyroid gland is an important organ that regulates body metabolism. It is located in the front of the neck just below the voice box. The thyroid gland secretes two main thyroid hormones - thyroxine and triiodothyronine. The secretion of both of these by the thyroid is controlled by a feedback mechanism involving the Pituitary gland, a small organ at the base of the brain, and the hypothalamus, a structure in the brain.
Parathyroid - The parathyroid consists of four tiny glands, located in the neck, that control the body's calcium levels. Each gland is about the size of a grain of rice. The parathyroids produce a hormone called parathyroid hormone, which raises the blood calcium level.
Thymus - The thymus gland is a gland that forms part of the immune system, which is situated in the upper part of the chest, behind the breastbone, and is made up of two lobes that join in front of the trachea. Each lobe is made of lymphoid tissue, consisting of tightly packed white blood cells and fat. The thymus enlarges from about the 12th week of gestation until puberty, when it begins to shrink. Its' function is to transform lymphocytes (white blood cells developed in the bone marrow) into T-cells (cells developed in the thymus). These cells are then transported to various lymph glands, where they play an important part in fighting infections and disease. Swelling of lymph glands and fever are a signal that immune cells are moltiplying to fight off invaders of the body: bacteria, fungi, viruses and/or parasites.
Ovaries - The ovaries are a part of the female reproductive system in vertebrates. They are the homologous pairs of the testes in the male reproductive system. Ovaries are a pair of ovum producing glands that are oval in shape and are the size of an almond. The ovary size is about 3 cm x 1.5cm x 1.5 cm. The ovaries are present right above the fallopian tubes in the lateral wall of the pelvis. The region where the ovaries are present is called the ovarian fossa. Ovaries are not attached to the fallopian tubes but they are attached to the outer layer of uterus with the help of ovarian ligaments. Ovaries function by releasing eggs every month; each ovary takes turns to release the egg. However, in case one of the ovaries cease to function or is damaged, the other will continue to produce eggs.
Tesicles - The testes contain germ cells that differentiate into mature spermatozoa, supporting cells called sertoli cells, and testosterone-producing cells called the leydig cells. The germ cells migrate to the fetal testes from the ombryonic yolk sac. The sertoli cells are analogous to the granulosa cells in the ovary, and the leydig (interstitial) cells are analogous to the stromal cells of the ovary. Enables the man to reproduce.