EXAM 2: The Autonomic Nervous System
Automatic nervous system
(ANS) consists of motor neurons that: -Innervate smooth muscles, cardiac muscle, and glands •Shunts blood to areas that need it and adjusts heart rate, blood pressure, digestive processes, etc. -Operate via subconscious control
What does the center of hypothalamus controls?
-Heart activity, blood pressure, the temperature of the body, water balance, and endocrine activity -Emotional responses (rage, fear, pleasure) activated through limbic system signal hypothalamus to activate the fight-or-flight system
The sensory (afferent) division of the PNS has two subdivisions
-somatic and autonomic sensory division
What are the THREE main anatomical Differences between sympathetic and parasympathetic divisions?
1.Sites or origin 2.Relative lengths of fibers 3.Location of ganglia
Control of the Autonomic Nervous System
ANS is under control of CNS centers in: -Brain stem and spinal cord, hypothalamus, and cerebral cortex -Hypothalamus is the main control center for ANS activity •Cerebral input may modify ANS but usually does so subconsciously -Works through limbic system structures on hypothalamic centers
The sensory division of the PNS contains nerves carrying sensory information into the CNS, these sensory nerves are called...
Afferents (carrying towards)
Map of referred pain
Convergence leads to Referred Pain
The motor division contains nerves carrying information out of the CNS to target organs, these motor nerves are called...
Efferents (carrying away)
Single innervation
Only SNS innervates smooth muscle of blood vessels and sweat glands
3.Location of ganglia
Parasympathetic ganglia are located in or near their visceral effector organ Sympathetic ganglia lie close to the spinal cord
2.Relative lengths of fibers
Parasympathetic has long preganglionic and short postganglionic fibers Sympathetic has short preganglionic and long postganglionic
Spinal cord functions
Reflexes for urination, defecation, erection, and ejaculation
Brain stem functions
Regulates pupil size, heart, blood pressure, airflow, salivation, etc
Visceral pain
Results from stimulation of visceral organ receptors - Felt as vague aching, gnawing, burning - Activated by tissue stretching, ischemia, chemicals, muscle spasms -Ex: chronic chest pain or pelvic pain
Differences between Somatic and Autonomic Nervous Systems
Somatic Nervous System -One neuron from CNS to the periphery -The effect is always stimulatory -VOLUNTARY MOVEMENT Autonomic Nervous System -Two-neuron chain -The effect is either stimulatory or inhibitory, depending on the type of receptors -INVOLUNTARY MOVEMENT
The autonomic nervous system is divided into two parts, what are they?
Sympathetic nervous system Parasympathetic nervous system
Hypothalamus function
The "boss": Overall integration of ANS
Dual innervation
all visceral organs are served by both divisions, but these divisions cause opposite effects -Dynamic antagonism between two divisions maintains homeostasis
What type of movement is the autonomic nervous system? - voluntary or involuntary
involuntary
The motor (efferent) division of the PNS is also subdivided into somatic and visceral divisions. The visceral motor division, more commonly called the autonomic nervous system, controls the...
involuntary actions of cardiac muscle, smooth muscle, and glands.
Are the sympathetic and parasympathetic nervous systems motor or sensory?
motor
Referred pain
pain from one body region perceived as coming from a different region •Visceral and somatic pain fibers travel along the same nerves, so the brain assumes stimulus comes from the common (somatic) region -Example: left arm pain during heart attack
The somatic sensory division conducts signals from receptors located in the...
skeletal muscles and skin
Sympathetic nervous system
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations. Example: Exercise, excitement, emergency, embarrassment are activated. FIGHT or FLIGHT
Parasympathetic nervous system
the division of the autonomic nervous system that calms the body, conserving its energy. Example: person relaxing and reading after a meal REST and DIGEST
The autonomic sensory division (also known as visceral) conducts signals predominantly from organs contained in the...
thoracic and abdominopelvic cavities - Ex:heart, lungs, intestines, bladder, etc.
The nerves that compromise the Peripheral Nervous System can be divided into two divisions based on whether the information is...
traveling or leaving the CNS.
What type of movement is the somatic nervous system? - voluntary or involuntary
voluntary -(skeletal muscles)
The motor (efferent) division of the PNS is also subdivided into somatic and visceral divisions. The somatic division controls the..
voluntary actions of the skeletal muscles in the body
Overlap of Somatic and Autonomic Function
•Higher brain centers regulate and coordinate both systems •Most spinal and many cranial nerves contain both somatic and autonomic fibers •Adaptations usually involve both skeletal muscles and visceral organs -Example: Active muscles require more oxygen and glucose, so ANS nerves speed up heart rate and open airways
Viscerosensory Receptors
•Nociceptors with free nerve endings •Respond to stimuli that damage tissue: - mechanical stimuli - ischemia (reduced blood flow) - chemicals Ex: myocardial ischemia, appendicitis, gastrointestinal cramping or bloating
1.Sites or origin
•Parasympathetic fibers are craniosacral; originate in the brain and sacral spinal cord •Sympathetic fibers are thoracolumbar; originate in thoracic and lumbar regions of spinal cord
Ascending Pathway for Sensory Afferents
•Spinothalamic (anterolateral) pathway to thalamus •Visceral pain is poorly localized because receptor density is low, receptive fields are large and input converges in pathway
Differences between Parasympathetic and Sympathetic Nervous Systems
•Two arms of ANS: -Parasympathetic division: promotes maintenance functions, conserves energy -Sympathetic division: mobilizes body during activity
