Ch. 14 Flashcards
Sensation
Process initiated by stimuli acting on sensory receptors
Perception
he conscious awareness of sensations
Senses
The means by which the brain receives info about environment and the body
What are the 2 groups senses are divided into?
General and special
General senses
Have receptors distrubuted over a large part of the body
What are the 2 groups general senses are divided into?
Somatic and Visceral
Somatic senses
Provides info about what?
What is the receptor type?
- *Provide sensory info about the body and environment**
1. Touch
2. Pressure
3. Temp
4. Pain
5. Proprioception
Receptor type -
Mechanoreceptors, Thermoreceptors, Noreceptors
Nerve ending -
Meissner corpusle, Hair follicle, Merkel disc, Pacinan corpuscle, free nerve ending, Ruffini end organ
Proprioception
The sense of your bodies position and movement
Visceral senses
Provides info about what?
What is the receptor type?
What are the nerve endings?
Info about various internal organs and consists primarly of
- Pain
- pressure
Special senses
are localized to specific organs that have specialized receptors
Smell, tasts, sight, hearing, and balance
What are the 3 criteria used to classify sensory recpetors?
- Type of stimulus they detect
- Location in the body
- Receptor structure
What are the 5 types of sensory receptors based on type of stimulus they detect?
- Mechanoreceptors
- Chemoreceptors
- Thermoreceptors
- Photoreceptors
- Nociceptors
What are Mechanoreceptors ?
Respond to mechanical force such as compression, bending or stretching of cells.
Physical simulus
** the senses of touch, pressure (BP), proprioception, hearing and balance all depend on a variety of mechanoreceptors
Chemoreceptors
Respond to chemicals
*Smell and taste depend on chemoreceptors
Thermoreceptors
Respond to changes in temp at site of receptor
There are more cold then there are hot receptors
Photoreceptors
Respond to light striking the receptor cells and are necessary for vision
Nociceptors
Aka Pain receptors
Respond to extreme mechanical., chemical and thermal stimuli
What are the 3 types of sensory receptors based on their location?
Cutaneous receptors
Viscerorecepors
Proprioceptors
Cutaneous receptors
Are associated with skin. Provide info about external environment
Viscerorecpetors
Associated with the viscera or organs, provide info about internal environment
Proprioceptors
associated with joints, tendons and other connective tissue
Provide info about body position, movement, and extent of stretch or force of muscular contractions
What are the 8 type of sensory recpetors based on structure?
Free nerve ending
Merkel Disc
Hair follicle
Pacinian corpuscle
Meissner corpuscle
Ruffini end organ
Muscle spindle
Golgi tendon organ
Free nerve endings
Definition
Location
Responsible for / Involved in
Relatively unspecialized neuronal branches simular to dendrites
Distrubuted through out most parts of body and are especially abundent in epithelial and connecive tissues
*Responsible for a number of sensations, pain, temp, itch and movement
Can be either tonic or phasic
Cold receptor
Increases it rate of action potential production as the skin is cooled
Warm receptors
Increases the rate of AP production as skin temp increases
Merkel discs
Defination
Location
Responsible for
AKA Tactile disks
Consists of axonal branches that end as flattened expansions each associated with an epithelial cell.
Distrubted throughout the basal layers of epidermis just superficial to basement membrane
*involved in sensations of light touch and superficial pressure/ can detect skin displacement of less than 1 mm
Hair follicle receptors
Definition
Location
Responsible for / Involved in
Respond to very light bending of the hair
*are involved in light touch
Not very localized but very sensitive
Pacinian corpuscles
Aka Lamellated corpuscles
Definition
Location
Responsible for / Involved in
Complx receptors that resemble an onion
a single dendrite extends to the center of each pacinian corpuscle.
located within subcutaneous tissue.
Responsible for deep cutaneous pressure and vibration
Meissner corpuscles
Definition
Location
Responsible for / Involved in
AKA tactile corpuscles
Evaluating texture
Distributed through out the dermal papillae
Involved in 2 point discrimination
numerous and close together in tounge and fingertips
2 point discrimination
ability to detect simulaneous simulation of 2 meissner corpuscles in 2 disinct receptor fields bu touching 2 points on skin
Numerous on tounge and fingertips
Ruffini end organs
Definition
Location
Responsible for / Involved in
Located in dermis of skin, primarily in fingers
Respond to pressure on skin directly superficial to receptor and to stretch of adjacent skin.
Important in continous touch or pressure
Muscle spindles
3-10 specialized muscle fibers that are located in skeletal muscles; provide info about length of muscle
Golgi tendon organs
Proprioceptive receptors associated with fibers of a tendon near the junction between the muscle and tendon
activated by an increase in tendon tension
Receptor potentional
Once the sensory receptor has been stimulated it produces a graded potential called receptor potential.
Primary receptors
Sensory receptor is the sensory neuron
Secondary receptors
Specialized cell that releases neurotransmitters to the senosry neuron to activate an action potential
*Receptor cells of taste, hearing and balance belong to this category
Adaptation
decreased sensitivy to continued stimulus.
Example clothes touching skin
Tonic receptors
Generate action potentials as long as stimulus is applied to they adapt very slowly
*Merkel disc and ruffini end organs
Phasic receptors
adapt rapidlly so they are more sensitive to changes in stimuli
Pacinian and meisseners
Some ascending pathways in CNS names start with ________ & end with_________
Others pathways indicate_________?
Origin
termination
Ex. Spinocerebellar
Location in spinal cord
What is the 3 neuron pathway?
Primary (Sensory recptor) - From PNS->Posterior horn->Synapse with interneuron
Secondary (Interneuron) - Decussate to other side, enter spinothalamic tract, ascend to thalamus
Tretiary - Thalamus to somaticsensory cortex
The 2 major pathways involved in conscious perception of external stimuli are
- Spinothalamic tract of anterolaeral system
- Dorsal-column/medial -lemniscal system
Anterolateral system
1 of 2 major systems that convey cutaneous sensory info to the brain
Includes 3 tracts: Spinothalamic, spinoreticular, spinomesencaphalic
Spinothalamic tract
Allows conscious perception of pain and temp as well as light touch, pressure, tickle, and itch
- Receptors go into dorsal root ganglion
- Connect with secondary neruon, desuccate and ascend to thalamus
- Connect to tretiary neuron and go to somaticsensory area of cerebral cortex
Spinoretuclar tract & Spinomesencephalic tract
Carry pain and touch sensations to other parts of brain, where info is not consciously perceived
**Some spinoretuclar tracts do not cross over bu ascend on the ipsilateral side of spinal cord
Primary neurons of spinothalamic tract..
1st neurons in pathway
Connect sensory recptor with spinal cord
Primary neuron cell bodies are located in dorsal root ganglia
Relay sensory input from the periphery to the dorsal horn of spinal cord where they synpase with interneurons
Secondary neurons in spinothalamic tract…
relay info to brain
within spinal cord, axons from 2nd neuron cross or decussate to the opposite side of spinal cord (occurs in anerior portion of gray and white commissures) Axons then enter spinothalamic tract and ascend to thalamus. They then synapse with tertiary neurons
Tertiary neurons in spinothalamic tract…
in the thalamus relay info to neurons in somatosensory cortex
Spinotectal tract
A portion of the spinomesencephalic tract that ends in superior colliculi and transmits action potentials involved in relfexes that turn head and eyes toward cutaneous stimulation
Dorsal column/Medial lemniscal system
Consists of 2 pathways that carry the sensation of 2 point discrimination, proprioception, pressure and vibration to cerebellum and cerebrum
- Primary neurons enter dorsal root ganglion from different locations. 1 for lower limbs/trunk and 1 for upper limb/trunk
- Ascend to the gracile and cutaneate nuclei synapse with secondary neuron, then decussate and ascend to thalamus
- Synapse with third order neuron then ascend to primary somatosensory cortex
*Primary neurons are located in dorsal root ganglia, are the largest cell bodies in dorsal root ganglia
Lemniscus means ribbon for thin like ribbon appearance of the pathway
Dorsal column/Medial lemniscal system are divided into what 2 tracts?
based on source of stimulus
Fasciculis gracilis and necleus gracilis
Fasciculus gracilis
Conveys sensations from lower part of the body, below the mid thoracic level
Middle tract
Terminates at Nucleus gracilis by synapsing with secondary neurons in medulla oblongata
Fasciculus cuneatus
conveys sensations from upper part of body, above the mid thorax
outer tract
terminates at nucleus cunteatus by synpasing with 2ndary neurons located in medulla oblongata