Unit 2.5 - Response and Regulation Flashcards
Define a sense organ
An organ comprised of a group of receptor cells which responds to a particular stimulus.
What stimuli do the sense organs respond to?
Eyes - light Ears - sound Skin - Touch/Temperature/Pressure Nose - Chemicals (smell) Mouth - Chemicals (taste)
What is the nervous system made up of?
The brain, spinal chord and all the body’s nerves
What are the central nervous system and peripheral nervous system?
CNS - Brain and Spinal Chord
PNS - Nerves that carry information to or from CNS
What are the properties of a reflex action?
Fast, automatic/involuntary, some are protective
In the reflex action of a hand being damaged by a cactus, what are the different components of the reflex arc?
Stimulus - Spines on cactus
Receptor - Receptor cells in skin
Sensory neurone - Neurone carrying impulse from receptor cells in skin to co-ordinator
Co-ordinator - Spinal chord
Relay neurone - Inside spinal chord, relays impulse from sensory neurone to motor neurone
Motor neurone - neuron carrying impulse from co-ordinator to effector
Effector - Muscles in arm
Response - pulling away from the cactus
What is a synapse and where does it appear in a reflex arc?
It is a small gap between the neurones over which the electrical impulse must pass when it goes from one neurone to another.
Define the sclera
Protective, tough white outer coat of eye
Define the cornea
The clear part of the sclera, which allows light to enter and refracts light entering.
Define the pupil
The hole in the center of the iris which allows light to enter.
Define the iris
Muscles which alter the size of the pupil to control the amount of light entering the eye.
Define the lens
The lens changes shape to focus light onto the retina.
Define the choroid
A pigmented layer which absorbs light to prevent reflection, also contains blood vessels.
Define the retina
A light sensitive layer where the image is formed and sent to optic nerve.
Define the optic nerve
The nerve which carries impulses from the eye to the brain.
Define the blind spot
The point where the optic nerve leaves the eye, so there are no light sensitive cells here.
Why must animals keep their internal conditions constant and which conditions must be kept constant?
Metabolism (all the chemical reactions in cells, including respiration) only operates within a narrow range of temperature and pH, and requires appropriate nutrients and water - keeping internal conditions constant is called homeostasis.
What are hormones?
Chemical messengers released by glands and carried by the blood which control many body functions.
Why is homeostasis of blood glucose levels important?
Glucose is required for respiration, so it is important that blood glucose levels are kept at a constant level.
What happens when blood glucose levels increase and when might this happen?
After eating a meal containing sugar or starch - pancreas releases the hormone insulin (a protein) into the blood, which causes the liver to convert glucose to insoluble glycogen, and the storing it, decreasing the blood glucose level.
What happens when blood glucose levels decrease and when might this happen?
After exercising, or a while after eating - pancreas releases glucagon, which breaks down glycogen stored in the liver into glucose, raising the blood glucose level.
