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P.N System
Peripheral Nervous System
| Question | Answer |
|---|---|
| Major structures of Peripheral Nervous System | Sensory receptor, Ganglia, Nerves |
| Sensory Receptor vary in? | The structure, location and type of stimulus |
| Bare dendrites associated with pain, thermal, tickle, itch, and some touch sensations. | Free nerve ending dendrites |
| Dendrites enclosed in connective tissue capsule for pressure, vibration, and some touch sensations | Encapsulated nerve endings |
| Receptor cells synapse with first-order sensory neurons; located in retina of eye (photoreceptors), inner ear (hair cells), and taste buds of tongue (gustatory receptor cells). | Separate cells |
| Receptor: Located at or near body surface; sensitive to stimuli originating outside body; provide information about external environment; convey visual, smell, taste, touch, pressure, vibration, thermal, and pain sensations | Exteroceptors |
| Receptor: Located in blood vessels, visceral organs, and nervous system; provide information about internal environment; impulses usually are not consciously perceived but occasionally may be felt as pain or pressure | Interoceptors |
| Receptor: Located in muscles, tendons, joints, and inner ear; provide information about body position, muscle length and tension, position and motion of joints, and equilibrium (balance). | Proprioceptors |
| Receptor: Detect mechanical stimuli; provide sensations of touch, pressure, vibration, proprioception, and hearing and equilibrium; also monitor stretching of blood vessels and internal organs. | Mechanoreceptors |
| Receptor: Detect changes in temperature. | Thermoreceptors |
| Receptor: Respond to painful stimuli resulting from physical or chemical damage to tissue. Detect light that strikes the retina of the eye | Nociceptors |
| Receptor: Detect chemicals in mouth (taste), nose (smell), and body fluids | Chemoreceptors |
| Sense osmotic pressure of body fluids | Osmoreceptors |
| Clusters of nerve cell bodies from somatic sensory neurons in a dorsal root of a spinal nerve. | Dorsal root ganglia |
| Clusters of nerve cell bodies from autonomic motor neurons in the autonomic nervous system. | Autonomic ganglia |
| Bundles of axons plus associated CT/vessels. Called TRACTS in C.N system | Nerves |
| Types of Nerves | cranial: 12 pairs that have names/roman numeral numbers, spinal:31 pairs that are numbered, peripheral nerves: form from spinal nerves |
| Ventral and dorsal roots attach a spinal nerve to a segment of the spinal cord | Spinal Nerves |
| Spinal Nerves: Shortly after passing through its intervertebral foramen a spinal nerve divides into several branches | Rami (Ramus) |
| Dorsal and ventral rami supply the entire somatic (skin, musculoskeletal) region of the | Body from the neck down |
| Interwoven network of nerves | Nerve plexus |
| Nerves C1-C5, Innervate muscles of neck & diaphragm | Cervical plexus |
| Nerve C5-T1, Innervate PECTORAL girdle & UPPER limbs | Brachial plexus |
| Nerves T12-L4, Innervate PELVIC girdle & LOWER limbs | Lumbar plexus |
| Nerves L4-S4, Innervate lower limbs | Sacral plexus |
| Emerging from the plexuses are the | Peripheral nerves |
| Purpose of the plexuses is to ensure that each limb muscle | Receives innervation from more than 1 spinal nerve. This ensures that damage to 1 spinal cord segment/nerve cannot completely paralyze a limb muscle. |
| Pathways that carry information from somatic sensory receptors to the primary somatosensory area in the cerebral cortex. | Somatic sensory pathways |
| Pathway: impulses from somatic receptors to the brain stem or spinal cord | First-order neurons |
| Pathway: impulses from the brain stem or spinal cord to the thalamus. Decussation occurs here therefore sensory information from one side of the body is conveyed to the other side of the brain. | Second-order neurons |
| Pathway: impulses from the thalamus to the primary somatosensory area of the cortex on the same side. | Third-order neuron |
| A dermatome is an area of skin that is mainly supplied by | A single sensory cranial or spinal nerve. |
| Respond to noxious stimuli. ie. intense thermal, mechanical or chemical stimuli Found in every tissue of the body except the brain. | Nociceptors |
| Pain from the skin carried by large myelinated neurons | Fast pain |
| Pain from the skin, deeper tissues and viscera carried by small unmyelinated neurons | Slow pain |
| Detect light that strikes the retina of the eye | Photoreceptors |
| Nerves that extend out of the brain stem/spinal cord are called | Lower Motor Neurons (LMNs) |
| LMN nerves innervate | Skeletal muscles of the face/head through cranial nerves and skeletal muscles of the limbs/trunk through spinal nerves |
| Nerves that synapse with LMNs are called | Upper Motor Neurons (UMNs) |
| Two UMN Pathways | Direct and Indirect motor pathways |
| Direct motor pathways | Deliver signals to LMNs from the primary motor area of the cerebral cortex |
| Why motor directions from one side of the body are relayed to the opposite side | Decussation of the pyramids in the medulla oblongata |
| Indirect motor pathways | Deliver signals to LMNs from motor centers in the brainstem who receive information from the basal nuclei, cerebellum and cerebral cortex |
| If a LMN is cut | Flaccid paralysis results |
| UMN synapse with LMNs to | - Initiate/coordinate voluntary movement - Influence reflex movement by usually inhibiting reflexes |
| If a UMN is cut there is lack of voluntary movement | Spastic paralysis results because the reflex is not being inhibited |
| Autonomic Nervous System (ANS) | Regulates activity of smooth/cardiac muscle and glands |
| Hypothalamus integrates the | ANS- the ‘boss’ |
| Autonomic Nervous System: Sensory information comes from? | Visceroceptors (in organs/not consciously perceived) , Special sense receptors, Somatic sense receptors |
| Autonomic motor pathways has TWO divisions that innervate most organs and are antagonistic to each other. ie. one stimulates and the other depresses the organ activity. | Sympathetic and Parasympathetic |
| Autonomic motor pathway has consist of two motor neurons in series | preganglionic & postganglionic neuron |
| Has its cell body in the central nervous system. The axon extends to an autonomic ganglion. | Preganglionic neuron |
| Has its axon extending from the ganglion to the effector (smooth muscle, cardiac muscle, or gland). | Postganglionic neuron |
| Produce and release, autonomic neurons are considered as either cholinergic or adrenergic | Neurotransmitters |
| Cholinergic neurons release the neurotransmitter | Acetylcholine (all preganglionic neurons and all postganglionic parasympathetic neurons) |
| Adrenergic neurons release | Norepinephrine (noradrenalin): *Drugs that mimic, enhance or inhibit these neurotransmitters are used to treat many medical conditions (called cholinergic or adrenergic drugs |
| The cell bodies of preganglionic neurons are in the thoracic and lumbar spinal cord. Ganglia are close to the spinal cord. | Sympathetic division |
| Cell bodies of the preganglionic neurons are in the brain and sacral spinal cord. Ganglia are close to or in the effectors. | Parasympathetic division |
| The FIGHT or FLIGHT division because its stimulation leads to increased alertness and metabolism to be ready for an emergency | The sympathetic nervous system |
| The REST & DIGEST division as its stimulation slows down most body activity | The parasympathetic nervous system |
| Sympathetic Responses examples | Pupils dilate, Heart rate/force of contraction and blood pressure increase, Airways dilate, Sweating for heat release |
| Parasympathetic Responses examples | Salivation, lacrimation, urination, digestion, defecation Also decreased heart rate, airway diameter and pupil diameter. |
| Fear normally elicits sympathetic responses. Syndrome occurs when someone is ‘backed into a corner’ with no escape. | Paradoxical Fear |
Created by:
aest12