Sensory Receptors_BTED Flashcards Preview

Jasandra_Med 2.1 (3) > Sensory Receptors_BTED > Flashcards

Flashcards in Sensory Receptors_BTED Deck (71):

Define a sensory receptor

Structures that recognise a stimulus in the internal (e.g. stomach) or external (e.g. skin) environment of an individual.
These nerve endings or specialised cells which then converts stimuli from the external or internal environment into afferent nerve impulses.


What happens to the nerve impulses once it reaches the sensory receptor?

Impulse passes (through PNS) into the CNS where is it initiates appropriate voluntary or involuntary responses


What can initiate an action potential in the sensory axon?

Depolarisation induced in the terminal of a sensory receptor, which if sufficiently large can initiate AP in the sensory axon (may be a separate cell or same cell)


What is the action potential in the sensory axon produced by?

Produced by sensory transduction (transformation of stimulus into electric current) -> membrane depolarisation -> an AP


Using taste bud as an example, show how taste is covered into an electrical signal to the brain

When stimulated, the taste bud triggers the release of neurotransmitter within the synapse, which will stimulate order neuron to generate an AP which may propagate along the axon into the CNS


Where are sensory receptor in the tongue found?

Taste bud


Where are sensory receptor in the carotid artery found?

Carotid body glomus cells


Where are sensory receptor in the tongue found?

Taste bud


All the information received by the sensory receptor gets flowed to where?

Peripheral nerve


Where are sensory receptor of the urinary bladder found?

The smooth muscle and urothelium


What does the sensory receptors do?

1) Provide information about the location, intensity, and duration of a peripheral stimulus
2) Receptors are designed to change (transduce) one kind of energy to another [i.e. touch to electrochemical nerve impulse]


What does the sensory receptors do?

1) Provide information about the location, intensity, and duration of a peripheral stimulus
2) Receptors are designed to change (transduce) one kind of energy to another [i.e. touch to electrochemical nerve impulse]


What are the characteristics of sensory receptors?

1) Information carried in a sensory system may or may not lead to awareness of the stimulus (conscious awareness)
- if not consciously aware, it means that the info. may not have reached the epithelium
2) Transduction process from sensory receptors involve the opening or closing of ion channels in the receptor
3) Ions then flow across the membrane, causing a receptor action potential


When does Amplitude of a receptor (generator) potential increase?

As stimulus strength and frequency of stimulation increase


What is adaptation?

A change over time in the responsiveness of the sensory system to a constant stimulus (receptors adapted to stimulus)


What are sensory receptors innervated by?

Different sensory receptors are innervated by different types of nerve fibres


What are muscles innervated by?

Type I and II fibres


What are skin receptors innervated by?

Innervated by alpha-beta, alpha-delta and C fibres


Normally where do the impulse form the stimulus of touch and pain sensation from either the trigeminal nerve (sensation in the face) and the typical spinal nerve, end up?

Postecentral gyrus of cerebral cortex


What is a cortical homunculus?

physical representation of the human body, located within the brain. A cortical homunculus is a neurological "map" of the anatomical divisions of the body.


What is identified in the homunculus?

Hand and lips are very sensitive therefore they need a lot of nerve tissue to process the information. Therefore there is a disproportionate large section allocated to it in the body


Name the classification of sensory receptors

1) Anatomical location
2) Function
3) Adaptive Properties
4) Structure


What are the divisions under Anatomical location?

1) Exteroceptors
2) Proprioceptors
3) Interoceptors (visceroreceptors)


What do exteroceptors respond to?

Respond to stimulus outside the body (touch, pressure, pain, etc.)


What do proprioceptors respond to?

Respond to information on position, orientation, movement and tension
(e.g. vestibular apparatus in ear, tendon organs, neuromuscular spindles in skeletal muscle)


What do interoceptors respond to?

Respond to stimulus from viscera
(e.g. chemoreceptors in blood vessels, receptors in bladder wall (distension)


Name the different divisions under Function.

1) Electroreceptors - electric field (Ampulla of Lorenzini) - sharks have this
2) Baroreceptors - pressure
3) Chemoreceptors - chemical stimuli
4) Hydroreceptors - humidity
5) Mechanoreceptors - mechanical stress
6) Nociceptors - pain perception
7) Osmoreceptors - osmolarity of fluids (hypothalamus)
8) Photoreceptors - light - eyes
9) Proprioceptors - change of position
10) Thermoreceptors - temperature change


Name the different division under Adaptive properties

1) Slowly adaptive (tonic)
2) Rapidly adaptive (phasic)


What is slowly adaptive (tonic)?

- Information about ongoing stimulation
- Continue to discharge during stimulation (slow to 'lose responsiveness')
- e.g. Ruffini nerve endings
- e.g. pain receptors, muscle spindle
- sensory receptor that adapts slowly to a stimulus and continues to produce action potentials over the duration of the stimulus. In this way it conveys information about the duration of the stimulus


What is rapidly adaptive (phasic)?

- Information about changing stimuli
- Respond only when stimulation starts or ends (rapid loss of responsiveness)
- e..g Pacinian corpuscle receptor
- sensory receptor that adapts rapidly to a stimulus. The response of the cell diminishes very quickly and then stops. It does not provide information on the duration of the stimulus; provides stimuli intensity and rate


What are the different division under Structure?

1) Non-encapsulated
2) Encapsulated


What is non-encapsulated?

- Free nerve endings (terminal branches of neuron)
- Terminal branches are unmyelinated
- Dermis and epidermis
- Nociceptors and thermoreceptors


What is encapsulated?

- Myelinated
- Specialised function
- Consist of remaining type of cutaneous receptors
- Not innervated by free nerve endings


What is free nerve endings used for?

Pain, heat, cold


What receptors are used for touch sensation?

1) Merkel discs
2) Krause end bulbs
3) Root hair plexus
4) Meissner corpuscles


What receptors are used for pressure?

1) Ruffini endings
2) Pacinian corpuscles


What is the widest distribution throughout the body?

Free nerve endings


Where is nerve endings located?

- Located in the epithelium between cells and between the epithelium and other layers in addition to blood vessels
- Found in skin, mucous membranes, joints, and other sites


What do free nerve endings respond to?

Respond directly to a wide variety of stimuli (pain, touch, pressure, tension)


What is under the category of non - encapsulated?

Free nerve endings


What is under the category of encapsulated?

1) Meissner tactile corpuscles
2) Pacinian corpuscles
3) Ruffini endings
4) End bulbs
5) Neuromuscular spindles
6) Tendon organs of Golgi


What is the Meissner Tactile Corpuscles?

Elongated spirals of receptor endings


Where is the Meissner Tactile Corpuscles located?

in Dermis


Where is the Meissner Tactile Corpuscles distribued widely in?

In skin (esp. hairless skin of the finger, pal of the hand, plantar surface of the foot, toes, nipples and lips)


What is a property of the Meissner Tactile Corpuscles?

Rapidly adapting


What is the stimulus of the Meissner Tactile Corpuscles?

1) Moving touch (to report moving objects on the skin);
2) sensitive to shape and textural changes in exploratory touch (neural basis for Braille reading)


What is the most widely distributed encapsulated receptor?

Pacinian Corpuscle (a.k.a Lamellar corpuscle)


Almost one third of the Pacinian Corpuscle is located where?

In the fingers


What does the Pacinian Corpuscle look like?

- Elliptical Capsule
- Concentric lamellae of fibroblasts and collagenous tissue


What does the Pacinian corpuscle do?

1) Invests the unmyelinated distal segment of a large myelinated (alpha-beta) axon
2) Sensitive to vibration and pressure
- only be able to tell when pressure has begun or ended


Histologically what does the Pacinian corpuscle look like?

Appear like a divided onion


What does the Pacinian corpuscle contain?

Encapsulated receptors


What is the Pacinian corpuscle characterised by?

Unusual structure


What are Ruffini endings?

Slowly adapting mechanoreceptors


What do Ruffini endings look like?

Elongated and complex


Where are Ruffini endings located?

1) Dermis of skin (finger tips)
2) joint capsule


What do Ruffini endings respond?

Sensation of pressure


What is the end bulb?

End bulb of Krause


What is the end bulb of Krause associated with?

Have been associated with sensations of temperature


What are muscle spindles?

Specialised striated fibres in a capsule parallel to the surrounding skeletal muscle fibres


Where are muscle spindles found?

Abundant in muscles that control fine movement


What do muscle spindles contain/

both efferent and afferent nerve fibres


What is muscle spindles innervated with?

Sensory and motor neuron


When does muscle activity stops?

Stops with relation of tension in the spindle (when skeletal muscle contracts)


What is the basis of all monosynaptic stretch reflexes (e.g. knee jerk)?

When a muscle is stretched by tapping its tendon, the stimulated receptor endings initiate an impulse in the afferent nerves which stimulates the alpha motor neurons and results in a reflex muscle contraction.


What is the tendon organ of Golgi?

Slowly adapting receptor


Where is the Tendon Organ of Golgi located in?

In tendons, close to junction with skeletal muscle


What are fascicles of tendon ensheathed by?

Connective Tissue


What does the Tendon Organ of Golgi do when the muscle is stretched excessively?

If muscle (along with its tendon) is stretched excessively, Tendon Organ of Golgi will respond immediately to relax the muscle


How is light converted to sensory impulse?

Rods and cones in retina


Where is the primary visual cortex located?

In occipital lobe at back of brain