Coordination and Response Flashcards
Homeostasis & Examples
The maintenance of a constant internal environment
E.g: Body water content, Body temperature
Co-ordinated response requires:
Stimulus, Receptor, (Coordination center), Effector
Roots
Positively Geotropic, Negatively Phototropic
Stems/Shoot
Negatively Geotropic, Positively Phototropic
Phototropic so
Geotropic so
P: Leaves have a greater surface area facing light, so more absorbed for photosynthesis
G: Roots can grow downwards for water and minerals in the darkness, Shoot grows upwards away from soil
Auxin in phototropic response of stems:
Auxin mostly made in tips of shoots and diffuses down the shoot
Auxin stimulates cells in a region to elongate
If light shines evenly, the auxin is distributed evenly and the cells grow at the same rate
If light shines (more) from one side, auxin concentrates on the shaded side, making those cells grow faster than the brighter side
This causes the shoot to bend and grow towards the light
Endocrine System
Hormones secreted from glands into blood stream
They travel in blood to target cells/organs
Bind to correct receptors on target cells, bringing about a response/triggering a chemical reaction
Used to control slower responses
Nervous System
Information sent through neurones as electrical responses
Impulses travel along neurones at very high speeds up to 100m/s
This allows rapid responses to stimuli
Nervous system coordinates receptors, decision making centres in CNS and effectors
Used to control rapid responses
Nervous vs Endocrine
N: involves Brain, spinal cord, neurones, E: Glands
N: Electrical impulse, E: Chemical hormone
N: Transmitted by neurones, E: Bloodstream
N: Muscle or gland effectors, E: target cells in specific tissues
N: Fast transmission, E: slower
N: Short & localised effect, E: Long and widespread
Nerve:
Bundle of neurones
CNS
Central Nervous System - brain and spinal cord
acts as central coordinating center
PNS
Peripheral Nervous System - all of the nerves in the body
Reflex Arc:
Receptor -> Sensory Neurone(PNS) -> Relay neurone(CNS) then synapses with -> Motor neurone -> Impulse to Effector -> Response - (fraction of a second)
Sensory Neurone Structure
Long, cell body middle of axon
Myelin sheath
Connected to receptor cell and CNS neurones
Relay Neurone Structure
Short, small cell body at one end with many dendrites
No Myelin sheath
Connects sensory and motor neurons
Motor Neurone Structure
Long, large cell body with long dendrites
Myelin sheath
Connected to CNS neurones and effectors
Dendrites function
Extend out of cell body and end of axon
Alows neurones to connect to many other neurones and recieve impulses
Synapse
Gap between dendrites of 2 neurones
Role of Neurotransmitters
Electrical impulses cannot travel directly from one neurone to the next
Electrical signal briefly converted to chemical signal, transferred across the synapse by Neurotransmitter molecules
Once the Neurotransmitters cross the synapse, the signal is converted back into an electrical impulse, which passes along the neurone
How is an impulse passed across a synapse
Electrical impulse travels along the presynaptic neurone
Vesicles at the end of the presynaptic neurone release neurotransmitters
Neurotransmitters diffuse across the synapse and bind with receptors on the postsynaptic membrane, stimulating electrical impulse in it to the next neurone.
Cornea Function
Transparent lens that refracts light as it enters the eye
Iris Function
Controls how much light enters the pupil
Lens Function
Transparent disc that changes shape to focus light onto the retina
Retina Function
Contains Light Receptor Cells - Rods (Detect light intensity) and Cones (Detect color)
