Biology Notes 3

Biology notes 3­27­07 • The Reflex Arc o Reflex­ Rapid, predictable, and involuntary responses to stimuli o Reflex arc­ direct route from a sensory neuron, to an inter­neuron,  to an effector • Types of Reflexes and Regulation o Autonomic reflexes o Smooth muscle regulation o Heart and blood pressure regulation o Regulaion of glands o Digestive system regulation • Somatic Reflexes o Activation of skeletal muscles • Regions of the Brain o Cerebral hemispheres (cerebellum)  Diencephalon  brain stem  Cerebellum o Paired (left and right) superior parts of the brain  include more than half of the brain mass o Cerebral Hemispheres (cerebrum) o The surface is made of ridges and grooves • Lobes of the Cerebrum • -Fissures (deep grooves) divide the cerebrum into lobes • -Surface lobes of the cerebrum o frontal lobe • parietal lobe • Occipital lobe • Temporal lobe • Specialized areas of the cerebrum Broca’a area- involved in our ability to speak Layers of the Cerebrum • • •

Gray matter o Outer layer Composed mostly of neuron cell bodies White matter

o -Fiber tracts inside the gray matter o -Example: corpus callosum connects hemispheres • Basal nuclei- internal islands of gray matter Diencephalon • Sits on top of the brain stem • Enclosed by the cerebral hemispheres • Made of three parts o Thalamus o Hypothalamus o Epithalamus Thalamus • The relay station for sensory impulses Hypothalamus • Under the thalamus • Important autonomic nervous system center o Helps regulate body temperature o Controls water balance o Regulates metabolism Brain Stem  Attaches to the spinal cord  Parts of the brain stem o Midbrain o Pons o Medulla oblongata Midbrain o Mostly composed of tracts of nerve fibers o Has two bulging fiber tracts- cerebral peduncles o Has four rounded protrusions – Corpora quadrigemina o Reflex centers for vision and hearing Pons The bulging center part of the brain stem Mostly composed of fiber tracts Includes nuclei involved in the control of breathing Medulla Oblongata The lowest part of the brain stem Merges into the spinal cord Contains important control centers Heart rate control Blood pressure regulation Breathing Swallowing Vomiting