lesson 2

• Nervous System


  Includes the brain, spinal cord, and a complex network of nerves
• Nervous System


  • Sends messages back and forth between the brain and the body
  • Highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body
• Central Nervous System (CNS)


  Includes the brain and spinal cord
• Peripheral Nervous System (PNS)


  Includes all nerve fibers and nerve cells not found in the central nervous system
• Neurons


  Nerve cells that send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking
• Axons


  The long, thin structure in which action potentials are generated; the transmitting part of the neuron
• Dendrites


  The receiving part of the neuron
• Types of Neurons


  • Sensory Neurons
  • Motor Neurons
  • Connector Neurons
• Sensory Neurons


  Carry impulses from the receptor to the CNS (brain or spinal cord)
• Motor Neurons


  Carry impulses from the CNS (brain or spinal cord) to the effector
• Connector Neurons


  Neurons that connect to brain regions
• Nerve Impulse


  An electrical signal that travels along a nerve fiber in response to a stimulus and serves to transmit a record of sensation from a receptor or an instruction to act to an effector
• Synapse


  A small gap at the end of a neuron that allows a signal to pass from one neuron to the next
• Reflexes


  An involuntary and nearly instantaneous movement in response to a stimulus
• Neurotransmitters


  Molecules that amplify, transmit, and convert signals in cells, having an essential role in information transmission throughout the nervous system
• Spinal Cord


  • A large rope-like segment of nerve tissue extending down the vertebral column
  • Serves as the connector mechanism for spinal reflexes and the connecting link between the peripheral system and the brain
• Spinal Nerves


  • Interact directly with the spinal cord to modulate motor and sensory information from the body's periphery
  • Enters and leaves the spinal cord through the spaces between the spinal vertebrae at regular intervals
  • There are 31 pairs of spinal nerves
• Dorsal Root


  Carries sensory nerve fibers
• Ventral Root


  Carries motor nerve fibers
• Brain


  A complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates our body
• Medulla Oblongata


  Serves as the connecting link between the spinal cord and the brain proper and it plays an important role in such automatic activities as heartbeat, breathing, and blood circulation
• Pons


  • Lies in the brain stem just above the medulla oblongata
  • Made up of largely of nerve fibers that connect higher
• Cerebellum


  Maintains posture and smooths out and coordinates complex muscular activities
• Midbrain


  • The connecting link between the hindbrain and the forebrain
  • Connects the sensory and motor pathways between the lower and upper portions of the nervous system
  • Portions of midbrain have a special role in visual and auditory activities
• Thalamus


  Large group of nuclei which serves as a relay station for sensory impulses to the appropriate areas of the brain
• Hypothalamus


  • Consisting of a group of small nuclei just below the thalamus
  • Plays an important role in many physiological activities
• Cerebrum


  • Represents the most important development of the brain in man which cannot be found in other organisms
  • The seat of consciousness and of the higher mental processes, such as language and abstract thinking
  • Divided into the right and left cerebral hemispheres (frontal, parietal, temporal, occipital)
• Somatic System


  Includes the sensory system and the motor nerves that activate skeletal (voluntary) muscles
• Autonomic System


  • Also called the vegetative nervous system
  • Concerned with activities of the body that make us alive – the glands, the internal organs, and other organs that function involuntarily
• Endocrine System


  • In charge of creating and releasing hormones to maintain countless bodily functions
  • Consists of different tissues and glands including pituitary gland, thyroid, pancreas, islets of Langerhans, adrenal, and parathyroid
• Pituitary Gland (Hypophysis)


  The master gland of the body
• Adrenal Lobes


  • Secretes several important hormones which have to do with growth, the formation of milk, and the functioning of other endocrine glands
• Posterior Lobes


  • Secretes vasopressin (an antidiuretic hormone) which controls excretion of water through the kidneys
  • Secretes oxytocin which stimulates the breasts to produce milk and stimulates contractions of the uterus during labor
• Thyroid Gland


  • Located at the base of the throat, near the Adam's apple in males
  • Secretes two known hormones: alrasine and idotlyroxine
• Adrenal Gland


  • Located on top of each kidney
  • Composed of two parts: the center or medulla and the outer layer or cortex
• Adrenal Cortex


  • Secretes a number of hormones that control many basic chemical mechanisms within the body, including metabolism of carbohydrates and functioning of reproductive organs
• Islets of Langerhans


  • The pancreas which contains the Islets of Langerhans is located just posterior to the stomach and attached by a duct to the intestinal tract
  • It delivers a pancreatic secretion into the digestive tract, thereby aiding digestion
  • Islets of Langerhans produce the hormones insulin and glucagon
• Gonads


  • Glands that produce hormones that are involved in reproduction and other functions of the body
  • During the period of embryonic development prior to the third month of prenatal development, we are neither female nor male. At the third month, we begin to differentiate; the sex glands develop
• Male Sex Glands (Testes)


  • Secrete a hormone known as testosterone
• Female Sex Glands (Ovaries)


  • Secrete estrogen and progesterone
  • Estrogen is responsible for the appearance of the secondary sex characteristics
  • Progesterone stimulates the thickening of the uterine lining in preparation for pregnancy