B6 -Brain and Mind
Stimulus is a change in the environment of an organism.
Simple reflexes produce rapid involuntary responses to stimuli
Simplest animals rely on reflexes actions for the majority of their behaviour.
Simple reflexes in humans include newborn reflexes (e.g. stepping,grasping and sucking),pupil reflexes,knee jerk and dropping a hot object.
Nervous coordination,including simple reflexes,requires :
- receptors to detect stimuli.
- processing centres to receive information and coordinate responses.
- effectors to produce the response.
Receptors and Effectors can form part of complex organs:
- Light receptors cells in the retina of the eye
- hormone secreting cells in a gland
- muscle cells in a muscle
The Nervous System uses electrical impluses for fast ,short lived responses including simple reflexes,
Hormones are chemicals that are produced in glands,travel in blood and bring about slower,longer lasting responses.eg. insulin and oestrogen.
The development of nervous and hormonal communication systems depended on the evolution of multicelluar organisms.
The Nervous system is made up of neurons linking receptor cells (in skin,ears and skin..) to effectors.
Neurons transmit electrical impluses when stimulated.
An axon is the long extension of the cytoplasm in a neuron and is surrounded by cell membrane.
Some axons are surrounded by a fatty shealth whwich insulates the neuron and increases the speed of transmission of a nerve impluse.
The central nervous system is made up of the brain and spinal cord.
The CNS(brain and spinal cord) is connected to the body via peripherial nervous system(PNS) which includes the motor and sensory and relay neuron.
CNS coordinates an animal's responses via: