PBL Topic 3 Case 2 Flashcards
What do mechanoreceptors detect?
- Mechanical compression or stretching of tissue adjacent to the receptor
What do thermoreceptors detect?
- Changes in temperature, some cold, others warmth
What do nociceptors detect?
- Damage occurring in tissue e.g. physical or chemical damage
What do electromagnetic receptors detect?
- Light on the retina of the eye
What do chemoreceptors detect?
- Taste in the mouth
- Smell in the nose
- Oxygen level in the blood
- Osmolality of blood
- [CO2]
What is a modality of sensation?
- Any principal type of sensation a person experiecnes
What is the labelled line principle?
- Specific nerve fibres transmit only one modality of sensation
- Since they terminate at a specific site in the CNS
What is a receptor potential?
- Change in membrane electrical potential whenever the receptor is stimulated
How does a stimulus cause an action potential?
- Stimulus excites a receptor
- Change in membrane permeability allowing diffusion of ions through the membrane
- Receptor potential rises above a threshold to generate an action potential
What is meant by receptor adaptation?
- The rate at which a receptor responds to a stimulus until the rate of action potential ceases
What is a tonic receptor? Give an example of a tonic receptor
- Slowly adapting
- Transmits continuous impulses to the brain as long as the stimulus is present
- Muscle spindle or Golgi tendon
What is a rate receptor? Give an example of a rate receptor
- Rapidly adapting
- Transmits signals only when the stimulus changes strength
- Pacinian corpuscle
How does a type A fibre compare to a type C fibre?
- Type A are larger and myelinated, transmission is faster
- Type C are smaller and unmyelinated, transmission is slower
Give two examples A-alpha fibre
- Annulospiral ending of muscle spindles
- Golgi tendon organs
Give an example of an A-beta fibre
- Cutaneous tactile receptor
Give an example of an A-gamma fibre
- Flower spray ending of muscle spindles
Give an example of an A-delta fibre
- Nociceptor carrying temperature, crude touch and pricking sensation
Give an example of a C fibre
- Pain and crude touch sensation
What is spatial summation?
- Signal strength increases by using progressively greater number of fibres
What is temporal summation?
- Signal strength increases by increasing number of impulses from each fibre
Outline the structure of a free nerve ending
- Nerve loses its Schwann cell sheath as it reaches dermis or epidermis
Identify two modalities that free nerve endings detect
- Temperature
- Pain
Identify a modality that Merkel cells detect? How do Merkel cells adapt?
- Pressure
- Slowly
Identify three encapsulated nerve endings
- Meissner’s corpuscles
- Ruffini endings
- Pacinian corpuscles