Co-ordination and Homeostasis Flashcards
What is the nervous system
A complex network of nerves that carry complex messages to and from the brain / spinal cord and to the rest of the body
What is the CNS
The central nervous system made up of the brain + spinal cord
Give 5 receptors and what they do
Eardrum - Vibrations in air + balance Tongue - Chemicals in food + drink Skin - Pain, pressure Eyes - Detect light Nose - Chemicals in air
What is the neural pathway
Stimuli - Receptor - Sensory neurone - Co-ordianator - Motor neurone - Effector
What is the relay neurone
Transfers the message across the CNS
In a reflex reaction where does the message go
The spinal cord - quicker
Give the reflex arc
Stimulus - Receptor - Sensory neurone - CNS - Relay neurone - Motor neurone - Effector
Neurons do not…..each other, instead there is a tiny gap which are called…..
Touch
Synapses
How do the impulses get across the neurones
The impulse arrives at the presynaptic neurone, the chemical messenger is released into the synapse.
The chemical messenger diffuses across the synapse because the synapse is only 20 nanometer wide, it takes a very short time
On the other side of the synapse, the neurotransmitter binds with a receptor molecule on the membrane of the postsynaptic neutron. When it binds, it stimulates a new impulse in the postsynaptic neurone.
Finally, the chemical messenger is reabsorbed back into the presynaptic neurone ready to be used again.
What are neurotransmitters stored in
Tiny packages called vesicles
The eye is a…..organ
Sense
What does the eye do
Acts as a light receptor and sends electrical messages to the brain in a way that allows us to distinguish different out intensities and colours
What are rods
Found in the Retina
Black and white image
Works in dim light
What are cones
Colour image
Works better in bright light
Gives clearer image
Concentrated in the Fovea
What happens to the eye when focusing on a distant object
Ciliary muscles relax
Suspensory ligaments stretch and tighten
Lens flattens
Rarefaction is reduced
What happens to the eye when focusing on a near object
Ciliary muscles contract
Suspensory ligaments become slack
Shape of sense becomes rounded
What happens to the eye under dim light
Pupil dilates
Radial muscles contract
Circular muscles relax
What happens to the eye in bright light
Pupil gets smaller
Circular muscles contracts
Radial muscles relax
What are hormones
Chemical messages
Where are hormones produced
By endocrine glands, and are secreted directly into the blood and are carried around the body within the plasma
What do hormones do when detected
Alter the action of the cell or organ
What is a gland
An organ that secretes a chemical which then travels elsewhere in the body
What does insulin do
Causes glucose to be stored as glycogen.
Encourages liver cells to take up glucose
What does adrenaline do
Breathing + heart rate increases.
Pupils dilate
blood diverted to muscles
Mental awareness increases
What is homeostasis
The maintains of a constant internal environment
Give 4 things that the body needs to control
Core body temperature
Blood water levels
Ion content
Blood glucose levels
Give two hormones that are involved with homeostasis
ADH - blood water levels
Insulin - blood glucose levels
What is glycogen
A store of glucose
Long branched chains
Stored in liver and muscles
Forms insoluble granules
What is the role of insulin
To promote the formation of glycogen in the liver, from glucose
What is the role of glucagon
Promotes the break down of glycogen to glucose
What happens when the blood sugar levels are high
Release of insulin
Formation of glycogen in liver form glucose
Blood sugar levels decrease
What happens when blood sugar levels are low
Release of glucagon
Stimulates the break down of glycogen
Glucose is released into the blood
What is type 1 diabetes
Inherited
Beta cells in pancreas stop producing insulin
Insulin injections needed before meals
What is type 2 diabetes
Common in those who are obese
Body does bot respond to insulin
Where do skin receptors send their signals to
Hypothalamus
What happens to the skin when we get very cold
Blood vessels in the skin vas constrict, heat is not lost.
Shivering releases heat through respiration
Hairs stand up to trap a layer of hair to insulate
Sweat glands decrease sweat production
What happens to the skin when we get very hot
Blood vessels in skin vasodilator - heat can radiate away (blood vessels bigger so more heat can be lost as closer to the surface of the skin)
Sweat glands increase sweat production, cools body as it evaporates
Hairs lie flat, do not insulate
What is a tropism
A tropism is a direct response, plants grow to wards or away from the stimulus
What is Phototropism
The growth in the response to light
What is Hydrotropism
Growth in response to water
What is Geotropism
The growth in response to gravity
If the direction of growth is towards the stimulus, then it is……
Positive
What happens to the plant when there is lots of light (auxins)
The meristem releases the auxins when detect light.
If the light is directly above, the auxins are evenly released.
If the light is coming in at an angle, they release more auxins on the shaded side of the plant, so that the plant elongates to one side
