Coordination Flashcards
Describe how responses can be controlled by nervous or by hormonal communication
Nervous - transmits impulses through nerve cells, the nerve impulses are fast and have an instant effect. The response is short lived and the impulses act on individual cells so have a localised effect.
Hormonal - transmits hormones through the bloodstream, they travel more slowly and take longer to act. The response is long-lasting and have widespread effects on different organs.
What is the central nervous system?
The central nervous system (CNS) is made up of the spinal cord and the unconscious part of the brain. It is linked to sense organs by nerves.
The CNS decides a response for a stimulus, which is done by receptors in sense organs sending messages through nerves to the spinal cord or the brain.
Describe the structure and functioning of a simple reflex arc
Stimuli is Detected by Receptors and will Stimulate Sensory Neurons to Send Electrical Impulses to the Central Nervous System (Brain and Spinal Cord)
Central Nervous System will Pass On Impulses to the Relay Neurons Across the Synapse (Gap) by Chemicals
The Relay Neurons will Pass on Impulses to the Motor Neurons which is Carried to the Effector
The Effector will Carry out the Response Quickly, Allowing Rapid Responses
Describe the structure and function of the eye as a receptor
The eye is a receptor of light:
Conjunctiva: lubricates and protects the surface of the eye.
Cornea: refracts light into the eye. It’s transparent, with no blood vessels to supply it with oxygen, so oxygen diffuses in from the outer surface.
Iris: controls the diameter of the pupil (how much light enters the eye).
Lens: focuses the light onto the retina.
Retina: light-sensitive, covered in light receptors (rods and cones).
Optic nerve: carries impulses from the receptors to the brain.
Describe the function of the eye in focusing near and distant objects, and in responding to changes in light intensity
When the eye is focus on a distant object, the rays of light from the object are almost parallel when they reach the cornea. The corner refracts the rays but the lens does not need to refract them much more to focus the light on the retina so it does not need to be very convex. The ciliary muscles relax and the pressure in the eye is pushed outwards on the lens, flattening it and stretching the suspensory ligaments.
On nearby object: light rays are diverging when they enter the eye. The lens has to be more context in order to refract the rays enough to focus them on the retina. The ciliary muscles now contract; the suspensory ligaments become slack and the elastic lens bulges into a move convex shape.
What are the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen?
Adrenaline: Adrenal glands - prepares the body for “fight or flight” - breathing rate increases, heat beats faster sending more blood to muscles, in liver - stored carbohydrates are changed into glucose and released into blood. Pupils dilate and body hair stands on end.
ADH - pituitary glands - controls the water content of the blood by increasing or decreasing the permeability of the kidneys
Insulin: pancreas - lowers the blood glucose levels in the body
Testosterone: controls the development of male secondary sexual characteristics
Progesterone: regulates the menstural cycle
Oestrogen: controls the development of female secondary sexual characteristics
Describe the geotropic responses of roots and stems
Shoots: grow away from the direction of gravity (negative geotropism)
Roots: grow towards the direction of gravity (positive geotropism)
Describe positive phototropism of stems
When the shoot tip is exposed to light, it accumulates more auxin on the side that’s in the shade.
This makes cells elongate faster on the shaded side, so the shoot bends towards the light.
