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NOTES: CH 49 NERVOUS SYSTEM ORGANIZATION; THE HUMAN BRAIN Recall…the nervous system is divided into 2 divisions: ● CENTRAL NERVOUS SYSTEM (CNS): information processing; integration ● PERIPHERAL NERVOUS SYSTEM (PNS): transmits info. to/from the CNS; plays a large role in regulating an animal’s movement & internal environment Organization of the CENTRAL NERVOUS SYSTEM: ● consists of the BRAIN & SPINAL CORD ● BRAIN: integration; complex behavior ● SPINAL CORD: conveys info. to / from the brain; generates basic patterns of locomotion SPINAL CORD: ● can also act independently of the brain as part of simple nerve circuits: REFLEXES! ● a reflex protects the body by triggering a rapid, involuntary response to a particular stimulus ● EXAMPLE: knee-jerk reflex Organization of the CENTRAL NERVOUS SYSTEM: ● CEREBROSPINAL FLUID: -formed in the brain by filtration of blood -circulates through brain, providing nutrients & hormones; carries away wastes -cushions the brain & spinal cord GRAY & WHITE MATTER: ● GRAY MATTER: -consists mainly of neuron cell bodies, dendrites, unmyelinated axons, & glia (support cells) ● WHITE MATTER: -consists of bundled axons w/myelin sheaths (gives the white appearance) Organization of the PERIPHERAL NERVOUS SYSTEM: ● consists of NERVES that branch out from the CNS and connect it to other parts of the body. ● includes: SPINAL NERVES and CRANIAL NERVES CRANIAL NERVES ● mammals have 12 pairs of cranial nerves ● originate from the cerebrum & brain stem ● innervate parts of the head, neck and trunk CRANIAL NERVES SPINAL NERVES ● mammals have 31 pairs of spinal nerves ● originate from the spinal cord ● innervate the upper & lower limbs, neck, and trunk SPINAL NERVES PERIPHERAL NERVOUS SYSTEM (PNS): ● can be subdivided into the: 1) Motor system: oversees conscious (voluntary) activities (i.e. skeletal muscles); 2) Autonomic nervous system: controls unconscious (involuntary) activities (i.e. heart, stomach, intestines, glands) AUTONOMIC NERVOUS SYSTEM ● branch of the PNS that is involuntary; ● includes 2 subdivisions: 1) SYMPATHETIC DIVISION; 2) PARASYMPATHETIC DIVISION. ● Sympathetic and parasympathetic divisions may act antagonistically (in opposition), alternately activating or inhibiting the actions of some organs, glands, etc. SYMPATHETIC DIVISION: ● prepares the body for energyexpending, stressful, or emergency situations EXAMPLE: during an emergency, the sympathetic division will increase the heart rate and breathing rate, etc. PARASYMPATHETIC DIVISION: ● is most active under ordinary, restful conditions; ● counterbalances the effects of the sympathetic division EXAMPLE: after an emergency, the parasympathetic division decreases the heart rate, breathing rate, etc. Parts of the Brain: ● During embryonic development, 3 brain regions become evident: 1) FOREBRAIN 2) MIDBRAIN 3) HINDBRAIN Brain Regions: ● Forebrain includes: cerebrum, thalamus, hypothalamus ● Midbrain ● Hindbrain includes: pons, medulla oblongata, cerebellum **the midbrain, along with the pons and medulla oblongata form the BRAINSTEM BRAINSTEM: ● anterior end of spinal cord; ● 3 parts that function in: -homeostasis -movement coordination -conduction of info. to higher brain centers: BRAINSTEM: 3 parts of the brainstem: 1) Medulla oblongata 2) Pons 3) Midbrain 1) Medulla oblongata: controls breathing, heart and blood vessel activity / dilation (and therefore blood pressure), respiratory center, swallowing, vomiting, digestion 2) Pons: regulates breathing centers in the medulla; relays impulses between the cerebrum and the medulla, and the cerebrum and cerebellum. 3) Midbrain: ● receives and sends sensory information; ● coordinates visual reflexes (eye movements with other movements) ● coordinates auditory reflexes (move the head to hear a sound more distinctly) CEREBELLUM: ● coordination of movement; ● balance; ● hand-eye coordination THALAMUS: ● relay center that sorts out & transmits sensory information to and from cerebrum; ● incoming information from all the senses is sorted here and sent on to the appropriate higher brain center; ● involved in regulating emotion & arousal (wakefulness) HYPOTHALAMUS: important regulator of HOMEOSTASIS contains body’s thermostat includes centers for regulating hunger & thirst plays role in sexual response and mating behavior HYPOTHALAMUS: fight-or-flight response, pleasure, daily biorhythms (“biological clock”) source of posterior pituitary hormones & releasing hormones for anterior pituitary hormones CEREBRUM: divided into hemispheres (R and L) each hemisphere divided into lobes (frontal, parietal, temporal, occipital) each hemisphere has an outer covering of gray matter = CEREBRAL CORTEX hemispheres are connected by white matter called CORPUS CALLOSUM CEREBRUM – functions! where memories are stored interprets sensory impulses arriving from sense organs centers for motor coordination; send motor impulses to muscles where conscious decisions are made intelligence and personality stem from cerebral activity language, cognition / thought / problem solving There are 2 functional cortical areas: 1) Primary Motor Cortex: sends commands to skeletal muscles, signaling appropriate responses to sensory stimuli 2) Primary Somatosensory Cortex: receives and integrates signals from touch, pain, pressure, and temperature receptors; divided into specific areas so that we can associate specific stimuli with specific parts of the body. Nervous System Disorders: ● Schizophrenia ● Depression ● Bipolar disorder (manic-depressive) ● Drug addiction ● Alzheimer’s Disease ● Parkinson’s Disease Schizophrenia: Drug Addiction: