Peripheral Nervous System PNS Include the following – Sensory receptors and sensation – Transmission lines the Nerves cranial and spinal – Motor endings and motor activity – Reflex activity

Sensory receptors and sensation Specialize to respond to environmental changes or stimuli Simple receptors for pain, touch, pressure, temperature in skin, as well as those found in skeletal muscles and tendons and visceral organs Complex receptors are the sense organs, vision, hearing, equilibrium, smell, and taste Classified by stimulus detected: mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, and nociceptors Classified by location: exteroceptors, interoceptors, proprioceptors

Sensation to Perception Sensation is awareness of internal and external stimuli Perception is conscious interpretation of those stimuli 3 levels of sensory integration: receptor, circuit (ascending pathway), perceptual levels (cerebral cortex) Function to transform generator potential to action potential – Levels of perception: spinal cord reflexes, nonspecific neurons, and then others to the thalamus

Levels of Motor Control Low- spinal cord and reflex arc Middle- motor cortex High - precommand uses cerebellum and basal nuclei

Components of Reflex arc 1.Receptor: site of stimulus action 2.Sensory neuron: transmits impulse to CNS 3.Integration Center: synapse between a signal neuron and motor neuron, or a more complex network of multiple synapses with a chain of interneurons 4.Motor neuron: conducts impulse from integration center to an effector organ 5.Effector: muscle fiber or gland cell that responds by contracting or secreting - somatic reflex actives skeletal muscle - autonomic reflex activates either smooth, cardiac muscle or a gland

Autonomic Nervous System

Function of ANS The system of motor neurons that innervates smooth and cardiac muscle and glands Signals from visceral organs send impulses to the CNS and the autonomic nerves make adjustments as necessary to ensure optimal support for body activities – Sending blood to needy areas – Speed or slow heart rate – Adjust blood pressure and body temperature – Increase or decrease stomach secretions

Neurotransmitters in ANS

Neurotransmitters Two major neurotransmitters: acetylcholine (Ach) and norepinephrine (NE) ACh binds to Cholinergic receptors the effects often are excitation or activation NE binds to Adrenergic receptors the effects vary depending on the target cells Effects are felt from the heart to kidney, lungs to digestive tract, constricts blood vessels of the skin and visceral organs except heart, think “adrenaline rush” ** inhibits insulin secretion by pancreas in order to elevate blood sugar levels, stimulates fat cells to break down fat, and liver to release stored sugars

Parasympathetic vs Sympathetic

Adrenal Medulla Embryologically, sympathetic ganglia and the adrenal medulla arise from the same tissue Sometimes referred to as a “misplaced” sympathetic ganglion, being located atop the kidney not in the CNS The adrenal ganglia releases norepinephrine and epinephrine, stimulating the secretion of adrenaline into the blood from the adrenal gland Produces the excitatory effect

Visceral reflexes Referred pain Visceral sensory neurons share pathways with somatic reflex arcs This becomes an issue when you have a heart attack and the visceral pain travels along the same pathway as somatic pain so the pain is perceived as somatic in origin, radiating to the superior thoracic wall and along the medial aspect of the left arm

Hypertension Results from homeostatic imbalance of the ANS Overactive sympathetic vasoconstictor response promoted by high levels of stress Increases the work load of the heart, causing an enlarged heart which restricts the pumping ability and can lead to heart failure Increases wear and tear on artery walls, this increases risk of a tear causing a stroke, or worse a fatal aorta rupture Treatment involves adrenergic receptor blocking drugs