Co-ordination and response Flashcards
what is a nerve impulse?
an electrical signal that passes along nerve cells (neurons)
what is the difference between the central nervous system and the peripheral nervous system?
the central nervous system is the brain and the spinal cord
the peripheral nervous system is every other part of the nervous system
what is involuntary action?
an action completes without conscious thought
describe the reflex arc
Sensory receptor recieves stimulus
The signal travels along a sensory neuron
The synapse at the end of the sensory neuron carries a message to the relay neurone
The signal travels along the relay neuron, transmitted to a motor neuron
The signal travels along the motor neurone
An effector recieves the signal and carries out a response.
what is a reflex action?
a rapid response to a stimulus by an effector (muscle or gland)
what is a synapse
A junction between two neurons
ensures that impulses travel in one direction only
what is the cornea and what is its function?
the transparent layer in front of the eye that protects the eye from damage
what are sense organs?
groups of cells that detect changes in the environment
what is the iris and what is its function?
the coloured ring around the pupil that controls its diameter
what is the pupil and what is its function?
the pupil is the hole in the middle of the iris that lets light into the eye
what is the optic nerve and what is its function?
the nerve coming out the back of the eye that send signals to the brain
what is the function of the lens?
the lens focuses the light rays onto the retina
state the response of the eye to a bright light
the pupil decreases in diameter to let less light in
state the response of the eye to a lack of light
the pupil increases in diameter to let more light in
how does the eye focus on near objects?
- the ciliary muscles contract and the suspensory ligaments loosen
- the lens becomes thicker
- light is refracted more
explain how the eye focuses on distant objects
- the ciliary muscles relax and the suspensory ligaments tighten
- the lens becomes thinner
- light is refracted less
The light from distant objects needs to be bent only weakly to focus on the retina. When looking at distant objects, the ciliary muscles relax, pulling in the suspensory ligaments which pull on the lens, stretching it thinner and bending light less strongly. This brings distant objects into
focus on the retina.
where are the adrenal glands located?
behind the kidneys
what is a hormone?
a chemical secreted by a gland into the blood that brings about an affect on one or more target organs
what hormone do the adrenal glands secrete?
adrenaline
where is the pancreas located?
what hormone does it secrete?
behind the stomach
insulin
what hormone do the testes secrete?
testosterone
what hormone do the ovaries secrete?
oestrogen
when is adrenaline secreted
during fight or flight situations
during
- scary situations
- stressful situations
- exciting situations
give 3 effects of adrenaline
- widens pupils
- increases heart rate
- increases breathing rate
what does oestrogen do?
causes the uterus lining to thicken
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
what does insulin do in the body?
Insulin decreases the level of glucose in the blood. It causes the liver cells to change blood glucose into glycogen to be stored.
glycogen (the carbohydrate stored in the liver) and glucose ( the sugar carried around in the blood).
what is homeostasis
maintaining a constant internal environment
give 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
describe the process of vasoconstriction
- the body detects a drop in temperature
- the blood vessels supplying the capillaries at the skin surface constrict (the muscles in the vessels contract
less blood flows closer to the skin so less heat is lost to the surroundings
what is phototropism and which part of the plant is positively phototropic?
its the growth of a plant towards a light source
the shoots are positively phototropic - they grow towards the light source
what is gravitropism and which part of the plant is positively gravitropic?
its the growth of a plant towards the pull of gravity
the roots are positively gravitropic - they grow in the same direction as the pull of gravity
explain how auxin controls shoot growth
auxin is made in the shoot tips of the plant and spreads through the plant
it is unequally distributed in response to light and or gravity
it stimulates cell elongation and the growth of the shoot on the side with most auxin
