Nervous system pt 4

Senses

Maintain homeostasis, by providing information about the outside world and the internal environment

General senses

made up of receptors that are widely distributed throughout the body; skin, various organs and joints

Special senses

made up of specialized receptors confined to structures in the head; eyes, ears, nose, and mouth

Sensory receptors

Collect information from the environment, and relay it to the CNS on sensory neurons; Link nervous system to internal and external changes or events; Can be specialized cells or multicellular structure

Transduction

when stimulus is converted into graded receptor potentials

Transmission

when receptor potentials trigger action potentials which are conducted along sensory neurons to CNS

Interpretation occurs….

in the brain or spinal cord of CNS

Chemoreceptors

Respond to changes in chemical concentrations like small, taste, and oxygen concentration

Nociceptors

pain receptors that respond to tissue damage from mechanical, electrical, or thermal energy

Thermoreceptors

respond to moderate changes in temperature

Mechanoreceptors

respond to mechanical forces that distort receptor like touch tension, blood pressure, and stretching

Photoreceptors

respond to light

Stimulation of receptor causes______________, causing graded potential according to stimulus intensity

local change in its membrane potential

If receptor is______, the membrane potential may generate an action potential

part of a neuron

If receptor is _________, the receptor potential must be transferred to a neuron to trigger an action potential

not part of a neuron

Sensation

Occurs when action potentials make the brain aware of a sensory event

Perception

Occurs when brain interprets sensory impulses

Projection

Process in which cerebral cortex interprets sensation as being derived from certain receptors. The brain projects the sensation back to the apparent source, allowing a person to locate the region of stimulation

Sensory Adaptation

the ability to ignore unimportant (or continuous) stimuli. Involves a decreased response to a particular stimulus from the receptors (peripheral adaptation) or along the CNS pathways leading to the cerebral cortex (central adaptation)

Exteroceptive senses

Senses associated with body surface

Interoceptive (visceroceptive) senses

Senses associated with changes in the viscera

Proprioceptive senses

Senses associated with changes in muscles, tendons, and joints, body position

what are the 3 types of mechanoreceptors that respond to touch and pressure

Free nerve endings, Tactile(Mesissner’s corpuscles, and Lamellated(Pacinian) corpuscles

Free nerve endings

simple receptors commonly found epithelial tissues that sense itching and other sensations

Tactile (Meissner’s) corpuscles

Receptors that detect fine touch and texture, used to distinguish between 2 points. They are found abundantly in hairless portions of the skin and lips

Lamellated (Pacinian) corpuscles

Nerve endings encased in large ellipsoidal structure, commonly found in deeper subcutaneous tissues, tendons, and ligaments, used to detect heavy pressure and vibrations

Nociceptor

Pain receptors that consist of free nerve endings that are stimulated by tissue damage, chemicals, mechanical forces, or extremes in temperature, oxygen deficiency

Pain receptors are the only receptors in viscera whose __________

stimulation produces sensations

Referred pain

Visceral pain that feels as if its coming from another part of the body

ex: Heart pain often feels like it is coming from the left shoulder or medial portion of left arm

Referred pain results from

common nerve pathways, in which sensory impulses from the visceral organ and a certain area of the skin synapse with the same neuron in the CNS

Fast pain (A-delta) fibers

Myelinated axons that conduct impulses rapidly. Associated with sharp (acute) pain in localized skin are that usually stops as soon as stimulus stops

Slow pain (C) fibers

Unmyelinated axons that conduct impulses slowly. Associated with dull, aching (chronic) pain that is difficult to localize. Pain often continues after stimulus stops

The sensation of pain begins in the _____

Thalamus

Part of the brain that judges intensity of pain, locates the source of pain, and produces emotional and motor responses to pain

Cerebral cortex

part of the brain that regulates flow of impulses from spinal cord

gray matter in brainstem

Pain-inhibiting substances produced in the body

Enkephalins, serotonin, and endorphins