2J Coordination and Response Flashcards
Homeostasis
Maintaining a constant internal environment despite external change
3 conditions which need to be controlled within the body
- Temperature
- Water levels
- Blood glucose concentration
3 main parts to a coordinated response
- A stimulus (e.g temperature change)
- A receptor (to detect the change)
- An effector (to carry out the response)
What does auxin trigger
Auxin triggers growth of the main stem of the plant (and it inhibits the growth of side shoots)
What is phototropism and which part of a plant is positively phototropic?
Phototropism is the growth of a plant towards a light source. The shoots are positively phototropic (they grow towards the light source)
What is geotropism and which part of a plant is positively geotropic?
Geotropism is the growth of a plant towards the pull of gravity
- The roots are positively geotropic (they grow down in the same direction as the pull of gravity)
How does auxin cause the shoots to grow towards the light source
- Auxin collects on the shaded side
- Auxin promotes cell growth
- The shoot curves towards the light
3 differences between nervous and hormonal communication
- Nervous communication uses nerve cells and impulses whereas hormones are secreted by glands and travel in the blood
- Nervous communication is generally much faster than hormonal communication
- Hormonal communication usually brings about longer lasting responses than nervous communication
What is the difference between the CNS and the Peripheral NS
The CNS is the brain and the spinal cord. The Peripheral NS is every other part of the NS
How is an impulse transmitted between two neurones? (synapse)
- The impulse reaches the end of one neurone
- A neurotransmitter is released and it diffuses across the gap
- A new impulse is triggered in the next neurone
Stimulus
change in the environment
Type of neurone that connects a receptor to the CNS
A sensory neurone
Effector
part of the body that brings about the response to a stimulus like a muscle or a gland
Type of neurone that connects the CNS to an effector
Motor neurone
Describe the reflex arc
Stimulus detected by a receptor
Impulse passed along sensory neurone to CNS (to a relay neurone)
Impulse passed along motor neurone to effector
Effector brings about the response
Describe the sequence of events involved in removing a hand away from a hot flame
- Thermoreceptors in the hand detect the heat of the flame
- An impulse is sent along a sensory neurone
- The impulse passes through relay neurones in the CNS
- The impulse then passes along a motor neurone and triggers the muscles in the arm to move the hand away
Cornea and is its function
The transparent layer in front of the eye
- protects the eye from damage
Iris and its function
The coloured ring around the pupil that controls its diameter
Optic nerve and its function?
The nerve coming out the back of the eye
- sends signals to the brain
Function of the lens
Focuses the light rays onto the retina
Retina and its functions
The black part of the eye
- converts visual stimuli into electrical impulses
What do the ciliary muscle and suspensory ligaments do?
They control the shape of the lens (accomodation)
How does the eye focus on near objects?
- Ciliary muscles contract and suspensory ligaments realx, causing the lens to thicken
- Thicker lens causes the light to refract more
How does the eye focus on far away objects?
- Ciliary muscles relax and suspensory ligaments stretch, which makes the lens thinner
- Thinner lens causes the light to refract less
How does the eye respond to bright light?
The iris contracts, making the pupil smaller and letting in less light
How does the eye respond to a lack of light?
The iris relaxes which makes the pupil larger and lets in more light
Why does the temperature need to be controlled?
To provide a suitable environment for enzymes so that they can work fastest at their optimum temperature
2 processes involving the skin that cool the body down
Sweating - cools the body by evaporation
Vasodilation - allows blood to flow closer to the surface of the skin where it can cool
Describe the process of vasodilation
- The body detects a rise in temperature
- Blood vessels supplying the capillaries at the skin surface dilate (the muscles in the vessels relax)
- More blood flows closer to the skin where it can cool
3 processes that work to keep the body warm
- Vasoconstriction
- Shivering
- Erection of hairs on the skin
Describe the process of vasoconstriction
- The body detects a drop in temperature
- Blood vessels supplying the capillaries at the skin surface constrict (the muscles in the vessels contract)
- Less blood flows closer to the skin surface so less heat is lost to the surroundings
What are hormones
Hormones are chemical messengers that are secreted by glands of the endocrine system into the bloodstream
What does insulin do in the body
Insulin decreases blood glucose concentration
Where is insulin secreted from?
The Beta cells of the pancreas
What does testosterone do?
- Main male sex hormone
- Involved in growth of testes and penis
- Triggers many changes in males during puberty (hair growth, deeper voice, increased muscle mass)
Where is testosterone secreted from?
The testes
When is adrenaline secreted?
During times of anxiety, fear or stress
Where is adrenaline released from?
The adrenal glands
3 effects of adrenaline in the body
- Increases heart and breathing rate
- Increases blood glucose concentration
- Dilates the pupils
What does oestrogen do?
Oestrogen causes the uterus lining to thicken
Where is oestrogen secreted from?
The ovaries
What hormone does oestrogen inhibit?
Oestrogen inhibits follicle stimulating hormone (FSH)
What does progesterone do?
Maintains the womb lining
Where is progesterone secreted from?
The ovaries
What hormone does progesterone inhibit?
Progesterone inhibits follicle stimulating hormone (FSH)
