Nervous System Flashcards
Define the term stimulus
A change in the external environment
Define the term receptor
Detects the stimulus
Define the term effector
A muscle or gland that carries out a response to the stimulus
Give the components (in order) of a coordinated response to a stimulus
Stimulus –> Receptor –> Coordinator (CNS) –> Effector –> Response
How do electrical impulses move from receptor to the CNS?
Sensory neurone
How do electrical impulses move through the CNS?
Relay neurones
How do electrical impulses move from CNS to effector?
Motor neurones
How do messages get transmitted from one neurone to another?
Across a synapse (chemically via a neurotransmitter)
State the two components of the CNS
Brain and spinal cord
State three ways in which nervous responses are different to hormonal responses
Faster, shorter-lived, more specific target, electrical (not chemical), travel via neurones (not bloodstream)
Where are receptors found?
In sense organs, e.g. skin, eyes etc.
What is the purpose of reflexes? Give an example
Rapid, quick, unconscious responses to danger; prevent damage. Examples include knee-jerk, withdrawal from a hot object, blinking
What is the name of the hard white outer layer of the eye that holds its shape?
Sclera
What is the jelly like substance contained within the eye that holds the eye’s shape
Vitreous humour
What structure coats the cornea as a protective layer?
Conjunctiva
What structure refracts light in the eye?
Cornea
What structure focuses light onto the retina?
Lens
What structure contains rods and cones (photosensitive cells) that allow image formation?
Retina
What structure sends impulses to the brain from the eye?
Optic nerve
What structure allows light into the eye?
Pupil
What pair of muscles in the iris control the diameter of the pupil?
Radial and circular muscles
What pair of muscles control the shape of the lens allowing the eye to focus on near/distant objects?
Ciliary muscle and suspensory ligaments
Describe the response of the pupil to dim light?
Pupil dilates; radial muscles contract, circular muscles relax
Describe the response of the lens to looking at a distant object
Lens becomes thinner/less convex; suspensory ligaments tighten, ciliary muscle relaxes
Describe the response of the lens to looking at a near object
Lens becomes fatter/more convex; suspensory ligaments slacken, ciliary muscles contract
