Ascending tracts & Sensory receptors Flashcards
What are sensory receptors
Specialized cells providing CNS with information. Respond to stimuli and convert it into AP’s in the process of transduction to carry it to CNS. CNS interprets info
What are sensory mechanisms that collect info form all over the body
Temperature Touch Pressure Vibration Proprioception Pain
What are the special senses that collect info
Vision Hearing Smell Taste Equilibrium
How can you classify somatic receptors
1- Based on mechanism of activation
2- based on purpose they serve
When classifying based on mechanism of action what are the types of somatic receptors
1- Mechanoreceptors : compression/ stretching
2- Thermoreceptors : hot/cold
3- Electromagnetic : light in retina
4- Chemoreceptors : O2, CO2, H+ levels , taste , smell
When classifying based on purpose what are the types of somatic receptors
1- Nociceptors : give rise to pain sensation ) mechanisms, thermo and chemoreceptors )
2- Proprioceptors : mechanoreceptors that give info about joint position and body movement
Can receptors only respond to 1 type of stimulus
No they can respond to multiple , but will show high sensitivity to one type of stimulus
Ex: pressure on eye can cause whit flash that is interpreted as a visual signal
If an area is sensitive it’s receptive field will be …
Small. Receptors will have little overlap to allow fine discrimination between different stimuli
Give an example of an area that would have small receptive fields and one that would have larger ones
Small : fingers
big : back / torso
What is a pacinian corpuscle and how does it work
A receptor consisting of a bare neurone tip surrounded by concentric tissue layers.
Local pressure will cause deformation of tissue , which will be transmitted to unmyelinated fibre tip. this allows depolarizing Na+ entry and electric signal will be sent if stimulus reaches threshold.
When is an AP generated
When receptor potential is above threshold membrane potential
The stimulus length is coded for in
1- Size of receptor potential
2- Sensory nerve frequency of AP ( frequency is proportional to stimulus )
Explain what a phasic response is and give an example of a receptor
Phasic receptors will adapt rapidly and the receptor potential and AP will diminish.
Brief , phasic response , gives transient info
ex: pacinian corpuscle
Explain what a tonic response is and give an example of a receptor
Receptors that respond with prolonged depolarization in presence of stimulus. little deputation. receptor potential and AP is maintained.
Constant sensation
Ex: some proprioceptors
Explain what are mechanoreceptors
Receptors that have stretch sensitive membrane channels and respond to distortion of that membrane.
List groups of mechanoreceptors and explain each
1- Tactile receptors of skin - fine or crude touch receptors - different pathways ascending to brain 2- deep tissue receptors - same as skin but in deeper tissue 3- proprioceptors - ex: muscle spindles , Golgi tendon organs, joint receptors 4- baroreceptors - within CVS : carotid sinus , aortic arch ,right atrium. senses stretch caused by blood pressure 5- inner ear receptors - cochlear ( move hairs ) and vestibular receptors ( move hairs )
What are the types of tactile receptors and explain each ( 6 ) - what they are composed of, where they are found and what do they sense
1- free nerve endings : bare dendrites between skin cells that give rise to tonic discharge when stimulated. small fields. only receptors on cornea of eye
2- root hair plexus : sensory dendrites surrounding hair follicles. rapidly adapting
3- Tactile Merkel’s discs: very sensitive peripheral tonic touch receptor. Closely associated with skin cells. grouped in igoo domes ( bumps on skin ). small field
4- Tactile Meissner’s corpuscles : encapsulated nerve ending in the dermis with dendrite network at the end . fast adapting. senses fine touch and low frequency vibration. In sensitive areas like finger types, eyelids, lips
5- Laminated Pacinian corpuscles: layer of CT with fluid in between surrounding single dendrite. Changes in CT = pressure. Rapid adapting. Senses deep pressure era high frequency vibration. on fingers and viscera ( deep tissue and skin)
6- Ruffini corpuscle : dendrites intertwined with collagen fibres in skin. give distortion sensation and skin pressure
What are muscle spindles
Senses muscle length , triggers muscle stretch reflexes.
when muscle shortens it’s detected by sensory receptors around the intramural fibres of the spindle. signals sent to SC via primary afferent nerve.
How do muscle spindles maintain their sensitivity
Y gam,a fibres are activated which travel to the contractile ends of muscle spindles and contracts it along with the muscle
What are Golgi tendon organs
Located in tendon , in series with muscles. Sense muscle tension. Initiate inhibitory reflex.
Explain joint receptors as proprioceptors
Free nerve endings in joint capsules that detect joint pressure & movement & tension
Explain Baroreceptors as a form of mechanoreceptors
free nerve endings in elastic tissue of distensible organs , blood vessels and respiratory , digestive and urinary tracts.
Monitor pressure changes in organ walls. Rapidly adapting & produce different afferents according to tissue
Explain temperature receptors
Located in : hypothalamus , spine , lover , skeletal muscle, dermis
Free nerve ending phasic receptors , sensitive to hot or cold temperatures. Transduced by TRP channels that open up in specific temperature ranges
Explain chemoreceptors
In carotid and aortic bodies : monitor blood pH , CO2 , O2 & elicit respiratory , CVS and behavioural responses
In medulla oblongata : monitor CSF pH and CO2
Hypothalamic receptors : monitor glucose, amino acids , osmolarity
In GI tract : taste buds, trigger gastric secretions
