Bio 14 Flashcards
What is a nerve impulse?-
An electrical signal that passes along nerve cells (neurones)
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 a voluntary action?
An action completed with conscious thought and under our own will
What is an involuntary action?
An action completed without conscious thought
Describe the reflex arc
“Stimulus detected by a receptor
Impulse passed along sensory neurone to relay neurones in the CNS
Impulse passed along motor neurone to effector
Effector brings about the response”
What is a reflex action?
A rapid & automatic response to a stimulus by an effector (muscle or gland)
What is a synapse?
A junction between two neurones
How is an impulse transmitted between two neurones?
1/ electrical impulse reaches end of neurone
2/ triggers release of neurotranmitter by vesicle
3/ neurotransmitter diffuses across synaptic gap
4/ it then binds to receptor on second neurone & stimulates electrical impulse
What is the purpose of synapses?
To ensure that impulses travel in one direction only
What are sense organs?
Group of receptor cells that respond to specific stimulus (light/sound/temp/touch/chemicals)
What is the cornea and what is its function?
The transparent layer in front of the eye that protects the eye from damage + refracts light
What is the iris and what is its function?
.The coloured ring around the pupil that controls how much light enters pupil
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 sends 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 bright light
The pupil decreases in diameter to let less light in
Explain the response of the eye to bright light
The circular muscle contracts and the radial muscle relaxes, making the pupil smaller
State the response of the eye to a lack of light
The pupil increases in diameter to let more light in, radial muscles contract, circular muscles relax
Explain how the eye focuses on distant objects
“The ciliary muscles loosen and the suspensory ligaments pull tight
The lens becomes thinner/flatter
Light is refracted less”
Explain how the eye focuses on near objects
“The ciliary muscles contract and the suspensory ligaments loosen
The lens becomes thicker
Light is refracted more”
“Describe the distribution of rods and
cones in the human eye “
Mostly more rods than cones in the eye however in the fovea there are more cones than rods
What is the fovea?
An area on the retina with lots of photosensitive cells so it has the highest visual acuity
What is the function of rods?
They function in low light intensities
What is the function of cones?
There are 3 different types of cone cells that all help to detect colour
What is a hormone?
A chemical secreted by a gland into the blood that changes the activity of one or more specific target organs
Where are the adrenal glands located?
Behind the kidneys
What hormone do the adrenal glands secrete?
Adrenaline
Where is the pancreas located?
Behind the stomach
What hormones does the pancreas secrete?
Insulin / glucagon
What hormone do the testes secrete?
Testosterone
What hormone do the ovaries secrete?
Oestrogen
When is adrenaline secreted?
During ‘fight or flight’ situations
Give 3 effects of adrenaline
“Widens pupils
Increases heart rate
Increases breathing rate”
Give 3 examples when adrenaline secretion increases
“During scary situations
During stressful situations
During exciting situations”
How does adrenaline cause an increase in respiration concentration?
1) adrenaline causes heart to beat w/ more force = ⬆️ heart rate
2) blood delivers ⬆️ oxygen & glucose to respiring cells
3) ⬆️ aerobic respiration
4) adrenaline causes liver to break glycogen
5) this ⬆️ blood glucose = ⬆️ respiration
Give 2 differences between the nervous system and the hormonal system
“Nervous Hormonal
Very fast message Slower message
Short lasting Long lasting”
Define homeostasis
Maintaining a constant internal environment within set limits despite external change
What mechanism is used to achieve homeostasis?
A negative feedback mechanism
What does insulin do in the body?
Insulin decreases blood glucose concentration
Bc: stimulates liver + muscle cells to take in glucose & convert excess into glycogen (storage)
What does glucagon do in the body?
Glucagon increases blood glucose concentration by increasing the conversion of glycogen to glucose in the liver
How type 1 diabetes treated?
“Insulin injections
Diet monitoring
“
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”
Give 3 processes that work to keep the body warm
“Vasoconstriction
Shivering
Erection of hairs on the skin”
Describe the process of vasodilation
“The body detects a rise in temperature
Arterioles near skin dilate
More blood flows through capillaries in surface layers of skin
More heat lost from skin
Temp lowered
What is phototropism?
Phototropism is the growth of a plant towards or away a light source.
What is gravitropism?
“Gravitropism is the growth of a plant towards or away of gravity.
The roots are positively gravitropic (they grow down in the same direction as the pull of gravity).
“
What is auxin and what does it do in shoots?
It is a hormone that causes cell elongation in shoots
Are shoots positively or negatively phototropic?
Postively phototropic
Are shoots positively or negatively geotropic?
Negatively geotropic
Describe how auxin controls shoot growth towards the sun
Auxin is:
produced in tips of shoots
unevenly ditributed
prefers shaded side of leaf
Auxin causes cell elongation therefore growing towards the sun
Explain how auxin controls shoot growth away from gravity
Gravity produces more auxin on the bottom side of the shoot causing it to enlogate away from gravity
Why do plants need auxin
To absorb more light
Light is needed for photosynthesis
