What are the four neural structures outside the brain and spinal cord (that make up the PNS)?
Sensory receptors, peripheral nerves, ganglia and efferent nerve endings
Collections of nerve cell bodies
Define peripheral nerves
31 pairs of mixed spinal nerves named for the point of issue from the spinal cord
What is the function of the PNS?
The PNS provides links to the outside world. It also carries impulses to and from the CNS. And it serves as the communicator via afferent and efferent nerves
What is the function and subdivisions of afferent nerves?
Brings sensory information toward the CNS and can be subdivided into somatic and visceral nerves.
What is the function and subdivisions of efferent nerves?
Carries motor commands away from the CNS. Can be subdivided into somatic and autonomic nerves.
Fight or flight
Rest and digest
Define somatosensory system
The part of the sensory system serving the body wall and limbs
What are the 3 types of receptors in the somatosensory system?
Exteroceptors, interoceptors and proprioceptors
What happens to a stimulus input as it travels to ward the CNS?
It's processed along the way
Where is the stimuli processed?
In the postcentral gyrus
What regions of the body does the primary somatosensory cortex receive sensory information from?
Skin, skeletal muscle, joints and tendons
What is the somatosensory humunculus?
It's a point-to-point mapping of the body on the brain that represents contralateral sensory input from various body regions. The amount of the brain that's covered by the image in the humunculus is representative of the amount of the brain and location used.
What is a sensory receptor?
The interface between the nervous system and the surrounding environment, both interior and exterior to the body.
What is the connection between the sensory receptor (in the PNS) and the neuron (in the CNS)?
A labeled line
Do sensory receptors pick up every different kind of stimuli?
No, only specific stimuli
What is the reaction that's generated by a stimuli?
A nerve impulse
How are sensory receptors classified?
Stimulus type, location and structure
What do thermoreceptors sense?
Heat and cold
What do Meissner's corpuscles sense?
What do nociceptors sense?
What so Pacinian corpuscles sense?
What are the stimuli that exteroceptors respond to?
Touch, pressure, pain tempurature
Exteroceptors respond to stimuli inside the body
False. They respond to stimuli outside the body
Where do interoceptors provide info about?
Inside the body
What do proprioceptors respond to?
Stretch in skeletal muscles, tendons, joints, ligaments and connective tissue coverings of bones and muscles. They also provide info about position and movement of the body
What are the various classifications of stimulus type?
Mechanoreceptors, thermoreceptors, chemoreceptors and nociceptors
What do mechanoreceptors respond to?
Touch, pressure, vibration and pain
What do thermoreceptors respond to?
Changes in temp
What do chemoreceptors respond to?
Chemicals, (i.e. smell, taste and changes in blood chemistry)
What do nociceptors respond to?
Pain, (i.e. extreme heat or cold, excessive pressure, inflammatory chemicals)
What are the two types of simple receptors for general senses?
Non-encapsulated and encapsulated
What are the varieties of non-encapsulated nerve endings?
Free nerve endings, tactile (Merkle) discs, hair follicle receptors
What are the different types of encapsulated nerve endings?
Meissner's corpuscles, pacinian corpuscle, ruffini corpuscle, muscle spindle and golgi tendon organ
Where are free nerve endings found?
The dermis and the epidermis
What types of tissues contain free nerve endings?
The epithelia and connective tissues
Describe nonencapsulated (free) nerve endings
They are non-myelinated with knoblike distal endings
What do thermoreceptors, nociceptors, chemoreceptors and mechanoreceptors all have in common?
They are all nonencapsulated (free) nerve endings
What do free nerve endings mostly respond to?
Temperature and pain. some to pressure induced tissue movement and itch.
Where are non-encapsulated simple receptors found?
In the stratum basale layer of the epidermis
All encapsulated nerve endings consist of...
One or more fiber terminals of sensory neurons enclosed in a connective tissue capsule
What do non-encapsulated simple receptors respond to?
Light touch and light pressure.
What are the two classifications that fall under non-encapsulated nerve endings?
Mechanoreceptors and exteroceptors