Lesson 3.04: Sympathetic and Parasympathetic Nervous Systems

Pathway for Nerve Impulses

1) Stimuli 2) Sensory Neurons 3) Interneurons 4) Preganglionic Motor Neurons 5) Ganglia 6) Postganglionic Motor Neurons 7) Effector Organ

Hydrolysis

a chemical process that splits a molecule by adding water

Effector

an organ (a gland or muscle) that becomes active in response to nerve impulses.

Parasympathetic Nervous System

calms body after a crisis and reestablishes homeostasis

Ganglia

collections of nerve cell bodies in Peripheral Nervous System

Sympathetic and Parasympathetic Nerve Impulses

nerve impulse enter via different pathways when coming from either sympathetic or parasympathetic nervous system (doesn't change message); neurotransmitter used by each system that explains different reactions of organs

Motor Neurons

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.

Postganglionic Motor Neurons

the visceral motor neurons outside of the CNS

Preganglionic Motor Neurons

visceral motor neurons located in spinal cord

Sympathetic Nervous System

•"fight or flight" •autonomic nervous system split into sympathetic and parasympathetic divisions (difference due to function) •sympathetic nervous system: prepares body for emergency or to react to a stressful situation (increase heart rate, constrict arteries to increase blood pressure, or dilate pupils to increase sensory input)

Sympathetic and Parasympathetic

•*Eye* -Sympathetic: dilation -Parasympathetic: constrict pupil •*Sweat Gland* -Sympathetic: stimulates secretion -Parasympathetic: no effect •*Heart* -Sympathetic: increase heart rate -Parasympathetic: decreases heart rate •*Blood Vessels* -Sympathetic: constriction to increase b.p. -Parasympathetic: dilates to decrease b.p. (b.p. = blood pressure) •*Lungs* -Sympathetic: increases respiration -Parasympathetic: decreases stimulation •*Gastrointestinal Tract* -Sympathetic: movement (slow digestion) -Parasympathetic: stimulates movement •*Fat Cells* -Sympathetic: stimulates hydrolysis of fat cells -Parasympathetic: no effect

Neurotransmitter

•chemical that transfers the nerve impulse from the axon to the end of one neuron to the dendrites of another neuron •in sympathetic nervous system, postganglionic motor neurons release nonepinephrine (effect depends on the tissue--excite or inhibit organ function) •in parasympathetic nervous system, postganglionic motor neurons release acetylcholine (excites organ function because it's attempting to bring organs back to homeostasis; exception is the cardiac muscle--slows heart rate instead)

Nerve Pathways (Summary)

•consists of one group of sensory neurons and two groups of motor neurons with set of ganglia in between •first set of motor neurons sit in the CNS (preganglionic motor neurons); these extend into the ganglia of the peripheral nervous system •second set of motor neurons (postganglionic motor neurons); extend from ganglia to body organs

Nerve Pathways

•in Sympathetic Nervous System, ganglia located in groups along certain cranial nerves (most distinct cranial ganglion is the Vagus nerve--transfers impulses to the heart, lungs, digestive tract, liver, and bladder: only specific certain tissues and organs--doesn't affect whole body at once)

Autonomic Nervous System v. Sensory Somatic Nervous System

•peripheral nervous system divided into sensory somatic nervous system and autonomic nervous system •sensory somatic nervous system controls voluntary actions of skeletal muscle •autonomic nervous system controls involuntary actions of cardiac muscles, smooth muscles, and glands *Sensory Somatic:* -one neuron from CNS to effector -excites nerve impulse of muscle *Automatic:* -two neurons from CNS to effector -excites or inhibits nerve impulse to muscle