Reflexes Flashcards
Reflexes
The nervous system allows the body to react or respond to changes or stimuli both inside or outside the body. May be involuntary or voluntary.
A reflex is
i) Inborn/innate (existing from birth)
ii) Rapid - As a small number of neurons involved
iii) Unlearned
iv) Stereotyped - Same every time
v) Involuntary - No conscious thought involved
Why are they needed
They are protective and designed to prevent any further damage to the body or when or immediate action is required.
Spinal reflexes
In many cases a reflex occurs without the information from neurons passing through the brain.
Instead the information is only passed through the spinal cord and known as a spinal reflex arc.
The reflex arc
The nerve pathway taken by a reflex.
Components of spinal reflex
- Receptor
- Sensory neuron
- Connector neuron and synapse
- Motor neuron
- Effector
- Receptor
- They receive the stimulus
- Either the ending of a sensory neuron or a specialised cell which detects the change in the environment
- Sensory neuron
- Release stimulus to the CNS
- Carries neurons impulses from the receptor to the spinal cord
- Passes through the dorsal root of the spinal cord
- Cell bodies of these neurons are located in the dorsal root ganglion
- Connector neurons
- Which acts as an integration centre
- Once inside the grey matter of the spinal cord, the sensory neuron, transmits through the synapse either to a connector neuron or directly to a motor neuron.
- Motor neuron
- Relays action to the effector
- Receives neurons impulse either directly from the sensory neuron or from a connector neuron. The impulse then leaves the spinal cord through the central root.
- Effector
- The muscle carrying out the response
- Receives the impulse from the motor neuron and carries out the response. An effector is either a muscle or cell
What is the spinal reflex
Important homeostatic mechanism which enables the body to respond quickly to a change in the environment.
Innate reflexes
Determined genetically (babies)
Acquired/Learned/Conditioned
Learned through constant repetition. Must be reinforced or will be weaken or lost. (School bell)
Receptors
A receptor is a structure that can detect a change in the internal or external environment.
Types of receptors
- Thermoreceptors
- Osmoreceptors
- Chemoreceptors
- Touch receptors
- Pain receptors/nociceptors
Thermoreceptors
Respond to changes in temperature. Peripheral thermoreceptors are in the hypothalamus, to detect changes in the body’s core temperature.
Osmoreceptors
Located in the hypothalamus, and are sensitive to many small changes in osmotic pressure to regulate water balance.
Chemoreceptors
Stimulated by particular chemicals (hydrogen ions). Can be found in mouth and nose, and are sensitive to pH especially due to O2 and CO2 concentrations.
Touch receptors/Mechareceptors/Pressure receptors
Located close to skin and are sensitive to very light touch. High in concentration in lips, eyelids, external genitals.
Deep in the skin respond to pressure and vibration.
Pain receptors/Nociceptors
Stimulated by damaged tissues due to low blood flow or excessive stimulation. Pain is uncomfortable, but required to warn us of damaged tissues to then take evasive actions/seek medical help.
