Chapter 3.3 Receptors and Reflexes ✓ Flashcards
What is a receptor?
A receptor is a structure that is able to detect a change in the body’s internal or external environment.
Define sense organ
It is receptors grouped into a discrete organ e.g. eye
Define stimulus
Stimulus refers to any change, internal or external, that causes a response
Define thermoreceptors
Thermoreceptors are able to respond to heat and cold
Define Osmoreceptors
A receptor sensitive to osmotic pressure of body fluids
Define chemoreceptors
A receptor sensitive to particular chemicals
Define touch receptors
A receptor sensitive to touch
Define pain receptors
A receptor that is stimulated by damage to tissues
Define reflex
A reflex is a rapid, automatic response to a change in the external or internal environment; tries to restore homeostasis
What are the four important properties of relfexes?
-A stimulus is required to trigger a reflex; the reflex is not spontaneous
-A reflex is involuntary; it occurs without any conscious thought
-A reflex is rapid; only a small number of neurons are involved
-A reflex is stereotyped; it occurs in the same way each time it happens
What part of the body coordinates reflexes
spinal cord
Define spinal reflex
A reflex carried out by the spinal cord without involvement of the brain
Define reflex arc
The pathway travelled by nerve impulses from receptor to effector in a reflex
Define spinal reflex arc
The pathway travelled by a nerve impulse from receptor to effector in a spinal reflex
What are the basic components of a reflex arc?
-Receptor: Reacts to a change in the internal or external environment by initiating a nerve impulse in the sensory neuron
-Sensory neuron: Carries impulses from the receptor to the spinal cord or brain
-Synapse (at least one): The nerve impulse may be passed directly to a motor neuron, or there may be one or more interneurons that direct the impulse to the correct motor neuron
-Motor neuron: Carries the nerve impulse to an effector
-Effector: Receives the nerve impulse and carries out the appropriate response. Effectors are muscle cells or secretory cells.
Define innate reflexes
A response to a stimulus that is acquired genetically and is therefore present at birth
Define acquired reflexes
A response to a stimulus that has been learnt through practice
What are some examples of innate reflexes?
-Sucking
-Chewing
-Following movements with eyes
What are some examples of acquired reflexes?
-Muscular adjustment required to maintain balance while riding a bike
-Jamming on the brakes of a car to avoid a dangerous situation
-Catching a ball
List the different types of receptors and state the relevant stimulus for each
-Thermoreceptors: Respond to heat and cold
-Osmoreceptors: Sensitive to osmotic pressure of body fluids
-Chemoreceptors: Sensitive to particular chemicals
-Touch receptors: Sensitive to touch
-Pain receptors: Stimulated by damage to tissues
Draw a labelled diagram to represent a spinal reflex arc
Diagram and answer on page 64
Compare and contrast pain and touch receptors
Touch receptors
-Located in the skin
-Specialised structures that detect touch, pressure and vibrations
-Receptors near the surface respond to light touch
-Deeper receptors respond to stronger pressure and vibrations
-More concentrated in highly sensitive areas like the fingertips and lips
-Adaptation varies by type - some adapt quickly, other slowly (shirt touching skin)
Pain receptors
-Located in the skin and other body tissues
-Free nerve endings that detect harmful or potentially damaging stimuli
-Stimulated by physical injury, extreme temperatures or certain chemicals
-Do not adapt-continue sending signals as long as the stimulus persists (cut or burn)
-Serve a protective function by triggering reflexes and altering the body to danger
Explain how a gag reflex protects the body
-The gag reflex is triggered when the back of the throat is stimulated.
-It causes throat muscles to contract, helping to expel foreign objects and prevent them from entering the airway, protecting the lungs from choking or infection
Describe the steps involved in the reflex initiated by touching a hot object
-Heat stimulates pain receptors in the skin
-A sensory neuron sends the signals to the spinal cord
-Interneurons in the spinal cord process the signal
-A motor neuron carries the response to the muscles
-The muscles contract to withdraw the hand from the hot object
