EDU2HBS Human Body Systems 1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Nervous Systems

EDU2HBS Human Body Systems 2 The Nervous System –Is the primary coordinating and controlling system of the body –Uses impulses to fulfill its functions General functions include

EDU2HBS Human Body Systems 3 Divisions of the Nervous System Anatomical divisions Central nervous system (CNS) Body’s neural control center Peripheral nervous system (PNS) Consists of nerves and sensory receptors Receptors Effectors

EDU2HBS Human Body Systems 4 Functional divisions –Sensory division –Motor division Divided into 2 divisions 1. Somatic nervous system Voluntary control of skeletal muscle 2. Autonomic nervous system Involuntary control of cardiac muscle, smooth muscle, and glands

EDU2HBS Human Body Systems 5 Nerve Tissue Neurons –Specialized to transmit neural impulses –Structural and functional units of nervous system –Though they vary in size and shape, neurons have many common features

EDU2HBS Human Body Systems 6 Structure of a neuron Dendrites Cell Body Axon

EDU2HBS Human Body Systems 7 Synapse The junction across which a nerve impulse passes from an axon terminal to the dendrite of another neuron. Threshold stimulus is needed to activate a neuron

EDU2HBS Human Body Systems 8 Steps in synaptic transmission An impulse travels down the axon When the impulse reaches the axon terminal, Ca+ ions are released.

EDU2HBS Human Body Systems 9 Steps in synaptic transmission (cont) The neurotransmitt ers alter the membrane surface to allow sodium into the dendrites This causes an action potential to start if threshold is reached

EDU2HBS Human Body Systems 10 Types of neurons Sensory neurons Motor neurons Carry impulses from CNS to effectors to produce an action

EDU2HBS Human Body Systems 11 Protection for the Central Nervous System Bones –Cranial bones –Vertebrae

EDU2HBS Human Body Systems 12 Meninges: three fibrous membranes Pia Mater Contain blood vessels to nourish brain and spinal cord Arachnoid Mater Filled with cerebrospinal fluid Dura Mater Attached to cranial bones

EDU2HBS Human Body Systems 13 The Brain Four major components: cerebrum, cerebellum, diencephalon, brain stem

EDU2HBS Human Body Systems Cerebrum Largest portion of the brain Left and right cerebral hemispheres Performs higher brain functions

EDU2HBS Human Body Systems 15 Hemisphere specialization –Each hemisphere performs basic functions Receiving sensory output Initiating voluntary motor output –Some functions are only performed by one hemisphere Left hemisphere Right hemisphere

EDU2HBS Human Body Systems 16 Cerebral hemisphere is divided into 4 lobes Frontal lobe Parietal lobe Temporal lobe Occipital lobe

EDU2HBS Human Body Systems Cerebellum Second largest brain region Controls posture, balance, and muscle coordination Damage results in loss of equilibrium, muscle coordination, and muscle tone

EDU2HBS Human Body Systems Diencephalon Lies between the brain stem and midbrain Consists of two major areas Thalamus relay station for sensory impulses Hypothalamus a role in regulation of body temperature and water balance the centre for many drives and emotions (thirst, appetite, sex, pain and pleasure)

EDU2HBS Human Body Systems Brain Stem About the size of a thumb and 3 inches long Provides a pathway for spinal cord Functions

EDU2HBS Human Body Systems 20 Spinal Cord A continuation of the brain stem 17 inches long Functions –Transmit impulses to and from brain Ascending (sensory) tracts Descending (motor) tracts –Reflex center for spinal reflexes

EDU2HBS Human Body Systems 21 Peripheral Nervous System Consists of nerves found outside the CNS Main function

EDU2HBS Human Body Systems 22 Reflexes –Maintain homeostasis and increase chances for survival –Reflex pathways are called reflex arcs

EDU2HBS Human Body Systems 23

EDU2HBS Human Body Systems 24 Autonomic Nervous System Consists of parts of central and peripheral nervous systems Purpose – to maintain homeostasis The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, sexual arousal

EDU2HBS Human Body Systems 25 Disorders of the Nervous System

EDU2HBS Human Body Systems 26 Alzheimer’s disease –Characterized by progressive loss of memory, disorientation, and mood swings –Exhibit loss of neurons in brain –Also have reduced ability to secrete acetylcholine Concussion –Caused by severe jarring of brain due to blow to the head –Can be accompanied by unconsciousness, amnesia, and confusion

EDU2HBS Human Body Systems 27 Dyslexia –Person reverses letters or syllables in words or words within sentences –Due to malfunctioning language center Fainting –Loss of consciousness due to sudden reduction in brain blood supply –Physical or psychological causes

EDU2HBS Human Body Systems 28 Headaches –Various causes Most due to dilation of blood vessels within the meninges Some are caused by tension in head and neck muscles Paralysis –Permanent loss of motor control over body parts –Common cause is injury to CNS