Biology Paper 2

• homeostasis: A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level
• nervous system: A conglomeration of billions of cells specifically designed to provide a communication network within the human body.
• receptors: Special structures that allow living organisms to sense the conditions of their internal or external environment
• stimuli: Changes, occurring within or outside the body, that affect nervous system functioning.
• coordination centres


  receive and process info from receptors
• effectors: muscles or glands that carry out the correct response to stimuli
• nerve: A cordlike bundle of neuronal axons and/or dendrites and associated connective tissue coursing together outside the central nervous system
• central nervous system


  The brain and spinal cord; CNS
• sensory neurones: nerve cells that carry messages from cells in the sense organs to the CNS
• motor neurones: Nerve cells that carry messages from the CNS to effectors
• gland: An organ that produces and releases chemicals either through ducts or into the bloodstream.
• reflex: A simple, automatic response to a sensory stimulus, such as the knee-jerk response. Automatic and rapid; they do not involve the conscious part of the brain.
• reflex arc: nerve pathway in which an impulse crosses only two synapses before producing a response; stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector - response
• neurotransmitters: Chemical messengers that cross the synaptic gaps between neurons.
• relay neurones: Nerve cells that carry signals from sensory neurones to motor neurones
• cerebral cortex: The part of the brain where information processing takes place. Divided into four lobes.
• medulla: The base of the brainstem; controls heartbeat and breathing.
• hypothalamus: A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.
• pituitary gland: The endocrine system's most influential gland. Under the influence of the hypothalamus, it regulates growth and controls other endocrine glands.
• cerebellum: A large structure of the hindbrain that controls fine motor skills.
• accommodation: The process by which the eye's lens changes shape to focus near or far objects on the retina.
• iris: A ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.
• pupil: The adjustable opening in the center of the eye through which light enters.
• cornea: Clear membrane at the front of the globe covering the iris, pupil, and anterior chamber. Responsible for 60% of the eye's focusing power.
• lens: The transparent structure behind the pupil that changes shape to help focus images on the retina.
• retina: The light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
• sclera: Dense fibrous opaque outer coat enclosing the eyeball except the part covered by the cornea; The "white" of the eye
• ciliary muscle: muscle that alters the shape of lens to accommodate vision
• suspensory ligament: A series of fibres that hold the lens of the eye in place
• optic nerve: the nerve that carries neural impulses from the eye to the brain
• circular muscles: Muscles found in the iris that contract in bright light and relax in dim light
• radial muscles: Muscles found in the iris that relax in bright light and contract in dim light
• hyperopia: A condition in which visual images come to a focus behind the retina of the eye and vision is better for distant than for near objects -- called also farsightedness.
• myopia: A condition in which the visual images come to a focus in front of the retina of the eye because of defects in the refractive media of the eye or of abnormal length of the eyeball resulting especially in defective vision of distant objects -- called also nearsightedness.
• convex


  curving outward
• hormone: Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues
• endocrine system: Glands that secrete hormones that regulate processes such as growth, reproduction, and nutrient use (metabolism) by body cells.
• ADH: Antidiuretic hormone; controls water levels in the blood, causes more water to be reabsorbed by the kidneys
• FSH: Follicle stimulating hormone; In females, FSH stimulates the ovaries to develop eggs and secrete oestrogen; in males, FSH stimulates spermatogenesis.
• oogenesis


  The production of mature egg cells.