Peripheral Nervous System: sensory

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receptors associated with the general senses

specialized endings of pseudodendrites of first order sensory neurons (pseudounipolar neurons) associated with skin and organ and body walls. They are sensitive to specific changes in the internal or external environent. They differ in structure, thresholds and locations.

exteroceptors and enteroceptors

Types of receptors

types of exteroceptors

nociceptors, thermoreceptors, mechanoreceptors would be categorized as this type of receptor.

exteroceptors

These are found in the skin and interact with the external environment

nociceptors

These receptor consist of free nerve endings. They respond to any extreme stimuli and generate impulses interpreted as pain. They are stimulated by tissue damage and low oxygen and extremes. They are particularly sensitive to bradykinin, the most painful substance known.

thermoreceptors

These receptors respond to changes in temperature.

light touch, regular touch, and pressure

types of mechanoreceptors

Meissner's corpuscles

Which receptor detects light touch in hairless portions of the skin and by root hair plexuses where hairs are present

free nerve endings or Merkel's discs

This receptors detects regular touch

Ruffini's and Pacinian corpuscles

These receptor detects pressure

enteroceptors

These receptors supply the body's interior

visceroceptors and proprioceptors

Types of enteroceptors

nociceptors, pressoreceptors, and chemoreceptors

Types of visceroceptors

pressoreceptors

These receptors are found in the walls of certain blood vessels (carotid and aortic sinuses) and detect change in blood pressure.

chemoreceptors

These receptors detect changes in chemical concentrations.

osmoreceptors

In the hypothalamus, these receptors detect body fluid concentrations (hypertonic vs hypotonic)

glucoreceptors

In the hypothalamus these receptors detect blood sugar levels

proprioceptors

These are mechanoreceptors that detect changes in muscle contraction and joint movement (concerned with the position of the body).

golgi tendon organs

detect excessive muscle tension

muscle spindles

detect stretch and movement of muscle tissue

Receptor adaptation

When, after continuous stimulation, receptors fail to respond. In order to avoid adaptation, change in the stimulus must exceed the rate of adaptation. Stimulation may exceed the ability of the receptor to adapt. Receptors vary in their ability to adapt.

nociceptors and proprioceptors

These receptors are slow adapters

thermoreceptors and touch receptors

These receptors are fast adapters

first order sensory neurons

These neurons are psudounipolar neurons in the periphery that have receptors that detect change in the environment.

dorsal root ganglia

It houses cell bodies of 1st order sensory neurons

2nd order sensory neurons

These neurons typically have their cell bodies in the posterior horn of gray matter and have axons that transmit impulses up the spinal cord to the thalamus.

3rd order sensory neurons

These neurons usually have their cell bodies in the thalamus and have axons that extend from the thalamus to the postcentral gyrus of the cortex

referred pain

This is the perception that pain is felt in a part of the body different from the part that is actually generating the pain.

referred pain

It is an inability to project properly. It probably involves an area of the body that is less familiar, convergence of different afferent neurons onto the same seconday neuron, commonly associated with decaying teeth, appendicitis, and heart attack.

root hair plexuses

These receptor detects light touch where hairs are present

Visceroceptors

These receptors are associated with the walls of internal organs

Chemoreceptors

In the medulla oblongata and in the carotid and aortic bodies, receptors detect carbon dioxide, oxygen and hydrgoen ions.

Osmoreceptors and glucoreceptors

Types of chemoreceptors

Proprioceptors

These receptors are associated with skeletal muscle, tendons and joints

Golgi tendon organs

These parts of the body detect excessive muslce tension

Muscle spindles

These parts of the body detect stretch and movement of muscle tissue

1st order sensory neurons

These neurons have psedodendrites (peripheral processes) that extends from the peripher to the brain stem nuclei of cranial nerves and the dorsal root ganglia of spinal nerves.

1st order sensory neurons

These neurons are the first neurons in the pathway that leads ultimately to the somatosensory cortex on the postcentral gyurs of the brain.

1st order sensory neurons

Axons of these neurons extend from the cell body to the posterior horn of gray matter in the spinal cord.

1st order sensory neurons

the axons of these neurons synapse with a second order sensory neuron in the posterior horn.

2nd order sensory neurons

With their axons in the spinocerebellar tract, these neurons transmit impulses (proprioception) to the cerebellum

thalamus

This part of the brain crudely determines the type and location of the sensation.

thalamus

This part of the brain tempers one's emotional reaction to the sensation

cerebral cortex (postcentral gyrus)

this part of the brain specifically determines the source and kind of sensation

cerebral cortex (postcentraly gyrus)

This part of the brain determines the intensity of the sensation

cerebral cortex (postcentral gyrus)

This part of the brain projects the sensation back to its source

exteroceptors

These receptors are housed in a special structure of special sense (eye, ear, tongue, nose)

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