BIOLOGY SBI 4 U December 11 2012 THE

BIOLOGY SBI 4 U December 11, 2012 THE NERVOUS SYSTEM AND HOMEOSTASIS Chapter THE NERVOUS SYSTEM AND HOMEOSTASIS

STRUCTURE OF THE NERVOUS SYSTEM: 2 components: Central Nervous System (CNS) -composed of the brain and spinal cord Peripheral Nervous System (PNS) -further divided into: the Autonomic NS (non-conscious) the Somatic NS (conscious)

Sympathetic • Fight or flight response • May interfere with higher levels of brain activity, affecting concentration and memory Parasympathetic • Opposite effect (Page 139, fig 5. 3) Autonomic nervous system

SOMATIC NERVOUS SYSTEM is comprised of : • Sensory neurons: sends impulses to the CNS • Motor neurons: transmits commands from the CNS to the muscles

1. NEURON: Structural and functional unit of the nervous system consists of: a) Cell body b) Dendrites c) Axon (More details in next class) REFLEX ARC: is the nerve pathway that leads from stimulus to reflex action. (p 141, fig 5. 5) Interesting fact: PNS is made of interconnected neurons held together by connective tissue CNS contains 90% of all the neurons in the body

The Brain co-ordinates homeostasis within the body. • It processes the information transmitted through the senses (receptors) • BRAIN is the control centre. • Body reacts to deal with the external and internal environment (effectors) The brain: • Contains about 100 billion neurons • Consumes 20% of the body’s oxygen and glucose • Contains 15% of the body’s blood supply • Complexity due to the variety of cells, unique internal hormone and interneurons (between various parts of the brain) THE BRAIN IS VERY COMPLEX! THE BRAIN AND HOMEOSTASIS

Brain research: 1. Study people with brain disease or injury: a) Observe symptoms, conclude it must be due to area of brain damage. 2. EEG (Electroencephalograph) discovered in 1924 • measures electrical activity of the brain • information can be printed out (objective). 3. Direct electrical stimulation • map the functions of the various areas 4. CAT scans: (computerized tomography) series of cross sectional xrays 5. PET scans: (positron emission tomography) observes changes in activity in specific areas Brain research

(page 143, fig. 5. 9) • • • Medulla Oblongata Cerebellum Thalamus Hypothalamus Cerebrum Four Lobes: v Frontal v Parietal v Occipital v Temporal (page 145, fig. 5. 10) STRUCTURES OF THE BRAIN

HW: Page 146, #3, 4, 6 Ms. Poblete’s Website: atpearsonci. weebley. com