The Nervous System
Functions of the Nervous System 1. Sensory input – gathering information To monitor changes occurring inside and outside the body (changes = stimuli) 2. Integration – to process and interpret sensory input and decide if action is needed. 3. Motor output A response to integrated stimuli The response activates muscles or glands
Neuron Anatomy Cell body Nucleus Large nucleolus
Neuron Anatomy Extensions outside the cell body Dendrites – conduct impulses toward the cell body Axons – conduct impulses away from the cell body (only 1!) Figure 7.4a
Nerve Fiber Coverings Schwann cells – produce myelin sheaths in jelly-roll like fashion Nodes of Ranvier – gaps in myelin sheath along the axon Figure 7.5
Application In Multiple Scleroses the myelin sheath is destroyed. The myelin sheath hardens to a tissue called the scleroses. This is considered an autoimmune disease. Why does MS appear to affect the muscles?
The Nervous System Major division - Central vs. Peripheral Central Nervous System Peripheral Nervous System Major division - Central vs. Peripheral Central or CNS- brain and spinal cord Peripheral- nerves connecting CNS to muscles and organs
Peripheral Nervous System 3 kinds of neurons connect CNS to the body sensory motor interneurons Motor - CNS to muscles and organs Sensory - sensory receptors to CNS Interneurons: Connections Within CNS Spinal Cord Brain Nerves key words: peripheral nervous system
Peripheral Nervous System k e l t a ( o m i c ) y p h P r s A u n N v key words: peripheral nervous system; skeletal nervous system; somatic nervous system; autonomic nervous system; sympathetic nervous system; parasympathetic nervous system
Somatic System Nerves to/from spinal cord control muscle movements somatosensory inputs Muscle Motor Neuron Interneuron Skin receptors Sensory Brain
Autonomic System Two divisions: Control involuntary functions sympathetic Parasympatheitic Control involuntary functions heartbeat blood pressure respiration perspiration digestion Can be influenced by thought and emotion
Sympathetic “ Fight or flight” response CENTRAL NERVOUS SYSTEM Brain Spinal cord SYMPATHETIC Dilates pupil Stimulates salivation Relaxes bronchi Accelerates heartbeat Inhibits activity Stimulates glucose Secretion of adrenaline, nonadrenaline Relaxes bladder Stimulates ejaculation in male Sympathetic ganglia Salivary glands Lungs Heart Stomach Pancreas Liver Adrenal gland Kidney “ Fight or flight” response Release adrenaline and noradrenaline Increases heart rate and blood pressure Increases blood flow to skeletal muscles Inhibits digestive functions keywords: sympathetic nervous system; fighlt or flight response
Parasympathetic “ Rest and digest ” system CENTRAL NERVOUS SYSTEM Brain PARASYMPATHETIC Spinal cord Stimulates salivation Constricts bronchi Slows heartbeat Stimulates activity Contracts bladder Stimulates erection of sex organs Stimulates gallbladder Gallbladder Contracts pupil “ Rest and digest ” system Calms body to conserve and maintain energy Lowers heartbeat, breathing rate, blood pressure key words: parasympathetic nervous system; rest and digest system
Summary of autonomic differences Autonomic nervous system controls physiological arousal Sympathetic division (arousing) Parasympathetic division (calming) Pupils dilate EYES Pupils contract Decreases SALVATION Increases Perspires SKIN Dries Increases RESPERATION Decreases Accelerates HEART Slows Inhibits DIGESTION Activates Secrete stress hormones ADRENAL GLANDS Decrease secretion of stress hormones key words: sympathetic nervous system; parasympathetic nervous system