Receptors Flashcards
Definition of stimulus.
Detectable change in internal / external envrionment that causes a change to the organism.
Definition of a receptor.
Cell that detects a stimulus. Receptors are specific to one type of stimulus.
Definition of co-ordinator.
Formulates a suitable response to a stimulus.
Definition of effector.
Organ that produces a response.
Definition of taxis.
A directional response.
Towards the stimulus is known as positive taxis.
Away from the stimulus is known as negtaive taxis.
Definition of kinesis.
A non-directional response.
Causes organisms to change the speed of their movement.
In favourable conditions, movement is slow with many turns.
In unfavourable conditions, movement is fast with few turns.
Definition of tropism.
The growth of a plant in response to a directional stimulus.
Towards the stimulus is known as positive tropism.
Away from the stimulus is known as negative tropsim.
Describe phototropism (5 points).
- Cell at shoot tip produces IAA.
- IAA diffuses down all regions of shoot.
- Direction of light affects diffusion of IAA. IAA diffuses away from light.
- IAA concentration builds up on shaded side of shoot. IAA causes cell elongation.
- Shaded side of shoot elongated faster than non-shaded side. Shoot tip bends towards light.
Describe gravitropism / geotropism(5 points).
- Cell at root tip produced IAA.
- IAA diffuses down all regions of root.
- Gravity causes movement of IAA from upper to lower side of root cells.
- IAA concentration build up on lower side of root. IAA inhibits cell elongation.
- Lower side of root elongates slower than upper side of root. Root tip bends downwards deeper into soil.
Definition of motor neuron.
A neuron that transmits an action potential from the central nervous system to an effector.
Definition of somatic nervous system.
Carries nerve impulses to body muscles which are under conscious control.
Definition of central nervous system.
Spinal cord and brain.
Definition of sensory neuron.
A neuron that transmits an action potential from a sensory receptor to the central bervous system.
Definition of reflex arc.
Pathway of neurons involved in unvoluntary response to sensory stimulus.
Definition of peripheral nervous system.
Neurons radiating out from the spinal cord to the rest of the body.
Definition of autonomic nervous system.
Carries nerve impulses to glands, smooth or cardiac muscles which are not under conscious control, involuntary. Sympathetic and parasympathetic nervous system form part of this.
Definition of sympathetic nervous system.
Increases heart rate by sending more impulses to excite the SAN (sino-atrial nodes).
Definition of parasympathetic nervous system.
Descrease heart rate by sending more impulses to inhibit the SAN (sino-atrial nodes).