11 CO-ORDINATION + CONTROL Flashcards
Define homeostasis
The maintenance of a constant internal enviroment
What is needed for a coordinated response
Stimulus, receptor, effector
What is in the central nervous system
The brain and spinal cord
How is the CNS linked to sense organs
Neurones
Types of neurone
- Sensory
- Relay
- Motor
How do the 3 types of neurones interlink
- Impulse from receptor pass along sensory neurones until they reach the CNS
- Impulses pass to relay neurones in the CNS
- Impulse passed to effectors along motor neurones
Role of myelin sheath
Insulates axon and speeds up transmission of impulse
Why are reflexes rapid
They do not involve the brain
Describe the process of a reflex arc
- Receptors detect the stimulus
- Send an electrical impulse along the sensory neurone
- Sensory neurone passes impulse to spinal cord to a relay neurone
- By neurotransmitters across the synapse
- Relay neurone passes the impulse through the spinal cord to a motor neurone
- Motor neurone causes effector to move away from stimulus
Describe what happens at the synapse
- Electrical impulse travels along axon
- Triggers neurotransmitters to be released and to diffuse across synapse
- Bind with receptor molecules on second neurone
- Stimulates another electrical impulse
Function of cornea
Focuses objects on the front of the eye
Function of pupil
Circular opening that’s controlled by the iris
Function of iris
Controls how much light enters pupil
Function of ciliary muscles
Contracts = lens gets thicker, relaxes = lens gets thinner
Function of suspensory ligament
Attach to ciliary muscle
Function of lens
Focuses light onto retina
Function of retina
Contains rods and cones
What happens to iris muscles in dim light
- Radial muscles contract
- Circular muscles relax
- Pupil dialtes
What happens to iris muscles in bright light
- Circular muscles contract
- Radial muslces relax
- Pupil constricts
How does the eye focus on a far object
- Ciliary muslces relax
- Suspensory ligaments pulled tight
- Lens pullled thin
- Less refraction of light
How does the eye focus on a near object
- Ciliary muslces contract
- Suspensory ligaments slack
- Lens thick and convex
- More refraction of light
What releases hormones
Glands
Hormonal vs Nervous: speed
Slow (except adrenaline) vs fast
Hormonal vs Nervous: type of message
Chemical vs electrical impulse
Hormonal vs Nervous: method sent
Via blood (dissolved in plasma) vs along neurones
Hormonal vs Nervous: response to message
Only target organs respond but still sent across body vs send directly to muscle
Hormonal vs Nervous: role in body
Controls long term processes vs used when a fast response needed
Insulin gland
Pancreas
Adrenaline gland
Adrenal glands
Testosterone gland
testis
Oestrogen gland
Ovary
Progesterone gland
Ovary
Insulin target organs
Liver and muscles
When the body is too hot, what changes take place
- Hairs stand on end - trap layer of air providing insulation
- Less sweat released - less heat loss by evaporation
- Vasoconstriction - arterioles under skin surface constrict, so less heat loss by radiation
When the body is too cold, what changes take place
- Hairs lie flat - insulating layer of air not formed
- More sweat released - upon evaporation heat energy is taken away from the skin
- Vasodilation - arterioles under skin surface dilate, so more blood flows by skin, so more heat loss by radiation
ADH gland
Pituitary gland
How does ADH affect the permability of the collecting duct
- ADH diffuses out of blood and binds with receptors on collecting duct
- More ADH that binds = more premeable to water
- More water reabsorbed
- Less urine
- More concentrated urine
How does auxin affect phototrophic responses
- Tip of shoot produces auxin
- Diffuses down the shoot causing elongation of cells
- Auxin builds on shaded side
- Shoot bends towards light
How does auxin affect phototrophic responses
- Tip of shoot produces auxin
- Diffuses down the shoot causing elongation of cells
- Auxin builds on shaded side
- Shoot bends towards light
What tropism is growth towards a light
Positive phototropism
What tropism is growth away from a light
Negative phototropism
What tropism is growth down due to gravity
Positive geotropism
What tropism is growth against gravity
Negative geotropism
What tropism is growth against gravity
Negative geotropism
