Autonomic Nervous System

Components

Function

• Involuntary control of systems in body, cardiac, respiratory, digestive, urinary, metabolism

Reflex arc

• Sensroy integrative motor pathway, called autonoic reflexes or visceral reflexes

• Efferent autonomic regulation is Dependent on sensory receptors

Parasympathetic

• motor/efferent pathways, rest and digest system, dominant controller

Sympathetic

• motor/efferent pathways, fight or flight, emergency system

Mixed Function

• sensory/afferent function: monitors internal and external environment in periphery and sends to CNS

• Motor/efferent function; sensory sends signal which is integrated in CNS and it controls response

Dual Innervation

• Allows for precise control of effector tissue

• Parasympathetic and sympathetic

• On division always stimulates(accelerator) and other inhibits(brake)- antagonistic, eg. pupils

• Some organs are only innervated by sympathetic nervous system

  • Adrenal glands, sweat glands, pilomotor muscles, blood vessels

Motor/Efferent Pathway of ANS: two neuron pathway

• Carries information that will stimulate a tissue to hae an effect

Preganglionic neuron

• Carries impulses from CNS to autonomic ganglion, efferent/motor neuron

Postganglionic neuron

• Carries impulases from autonomic ganglion to effector tissue in periphery, efferent/motor neuron

Anatomy of each system

Receptors and Neurotransmitters of ANS

Acetylcholine

• Cholinergic neurons if they release ACh

• ACh binds to specific receptors on effector cells, cholinergic receptors

  • Muscarinic chollinergic and nicotinic cholinergic

Norepinephrine

• Adrenergic neurons if they release norepinephrine

• NE bind to specific receptors on effector cells, adrenergic receptors

  • Alpha and beta receptors

Sympathetic nervous system: effent/motor

• Preganglionic neurons → ACETYLCHOLINE

• Postganglionic neurons → usually NOREPHINEPHRINE, only one circumstance where ACETYLCHOLINE is release, when sympathetic fibers project to sweat glands

  • Sweat glands produce sweat when ACETYLCHOLINE neurotransmitters stimulating it

Parasympathetic nervous system: efferent/motor

• Preganglionic neurons → ACETYLCHOLINE

• Postganglionic neurons → ACETYLCHOLINE

Cholinergic receptors

Nicotinic

• Located on cell bodies of ALL postganglionic neurons in both divisions

Muscarinic

• Found on ALL effector cells in parasympathetic division, when ACh binds, they promote rest and digest

• Also located on sweat glands in sympathetic division, when ACh binds, they promote sweat secretion

Adrenergic receptors

Alpha

beta

Duration and termination of acetylcholine

• Each vesivle containts 1000-50000 molecules

• 30-300 vesicles

• 1-2 msec, constant release of ACh to cause sustained effect

• Inactivated by acetylcholinersterase breaks down ACh to reuptake it into presynaptic neuron

General and Special Senses (online)

Sensory Receptors

• So that body can respond to stimuli by converting them to nerve impulses

• Different receptors respond to different stimuli, than transmits it to processing centre

• Acquired through depolarization of sensory nerve endings

• Is affected by age, disease, structural defects and more

Receptor Potential

• Stimulus acts on receptor, develops potential, if large enough threshold is reached and action potential is triggered

• Impulse travels along axon to CNS, this is where sensation is felt, and reflex response is started

Principle of Adaptation

• Receptor potential decreases over time in response to continuous stimuli

  • Initially you feel dangling earrings, but throughout the day you don’t feel it anymore because you have adapted ot its sensation

• Leads to decreasing rate of impulse conduction and decrease intensity of sensation

• Rapidly adapting receptors and slowly adapting receptors

Special Sense Receptors

• Receive input for smell, tast, vision, hearing, equilibrium

• In localized areas or complex organse

Gneeral sense organs

• Widely distributed in body, touch, temperature, location, etc

• Skin, mucosa, connective tissue, muscles, tendons, joints, viscera (organs)

Based on structure

Free Nerve Endings

• Simplest, most widely distributed

• Surfaces of body, externoreptors and deep in organds, visceroceptors, nociceptors (pain), thermo and tough receptors (merkel disks, root hair plexuses)

Encapsulated nerve endings

• Touch ad pressure receptors, have capsule on it, a connective tissue capsule that surrounds the ends

• Corpuscles: touch, pressure, vibraiton

• Stretch receptors: muscle spindles allow us to sense muscle length changes, golgi tendon receptors allow us to sense muscle tension and activated to lead to relaxation to prevent injury, both contribute to proprioception

By Location

Exteroceptors

• Body surface, picks up information by external environment

Visceroceptors

• Internally in body organs, recives information about internal environment

Proprioceptors

• Special type of visceroceptors, skeletal muscles, tendons, joint capsules

• Receives information about body movement, position, and orientation in space

• Tonic Proprioceptors: slow adapting, positional information while at rest

• Pasic Proprioceptors: rapidly adapting, positional information while moving

BY type of Stimulus Detected

Mechanoreceptors: activated by mechanical stimuli (stretch, pressure)

Chemoreceptors: activated by change in concentration of chemicals

Thermorecptors: activated by temperature changes

Nociceptors: activated by intense stimulation, results in pain

Photoreceptors: only in eye, activated by light

Osmoreceptors: in hypothalamus, activated by changes in concentration of electrolytes

By Selectivity and Snesitivity

• A range of thermoreceptor sensitivity, both cold and warm go through rapid adaptation, cold has broader response

• Discriminative touch: fine touch, you can pinpoint the area in your foot being touched

• Cutaneous sensation: people with uncontrolled diabetes can lose there ability to sense touch in toes

Referred Pain

• Stimulation of pain receptors in deep structure but can be felt as pain in skin that lies over the affected structure

  • Eg. if gallbladder is hurt there might be pain inbetween shoulder blade

  • A hear attack in men cause pain down arm, comes from different locations but travel along same pathway

• Caused from convergence of sensory nerve impulses from both diseeased organ and skin in area of refereed pain