Section 6 - Coordination and Response Flashcards
stimulus meaning
a change in internal or external environment
receptors
they detect stimuli. receptors in the sense organs (eyes ears nose tongue and skin) are groups of cells that detect external stimuli
effectors
cells that bring about a response to stimuli. they include muscle cells and cells found in glands. effectors respond in different ways - muscle cells contract whereas glands secrete hormones.
how do receptors communicate
they communicate with effectors via the nervous system or/and the hormonal system
whats the CNS
- the nervous system is made up of all the neuroes (nerve cells) in your body. There are three main types - motor, relay and sensory
- the central nervous system consists of spinal cord and brain only its job is to coordinate responses. coordinated responses need a stimulus a receptor and an effector
CNS how it works
- when receptors in a sense organ detect a stimulus they send electrical impulses along sensory neurons to the CNS
- the CNS sends electrical impulses to an effector along a motor neuron. the effector then responds accordingly
- because neurones transmit information using high speed electrical impulses the nervous system is able to bring about very rapid responses
synapses
- the connection between two neurons is called a synapse.
- the nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
- these chemicals set of a new electrical signal to the next neurone
Reflexes
They are automatic responses to certain stimuli. They reduce the chances of being injured.
What is a reflex arc?
The route taken by information in a reflex through central nervous system.
The reflex arc (process)
- Stimulus is detected by receptors an impulse is set along a sesory euron to cns.
- In the cns, the sesory neuron passes o the message to a relay neuron.
- Relay neuros relay impulse to motor euros.
- Impulse travels alog motor neurons to the effector.
- Muscle the contracts ad moves away from stimulus.
- Because it goes through the spinal cord and the uconscious part of the brain, you don’t think ad it is a quicker response.
Block Diagram
Stimulus / Receptor / Sesory neuron / CNS / Motor euro / Effector / Response
Parts of the eye
- Conjunctiva
- Sclera
- Cornea
- Iris
- Lens
- Optic nerve
Conjunctiva
Lubricates and protects the surface of the eye
Sclera
Tough outer layer protecting the eye
Cornea
Refracts (bends) light into the eye. It is transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from outer surface.
Iris
Controls the diameter of the pupil ( hole in middle ) and therefore how much light eters the eye.
Lens
Focus light into the retina ( the light sesitive part covered in receptors called rods ad cones )
Rods are more sensitive in dim light but can’t sese colours
Cones are sensitive to colours but aren’t so good in dim light. They are foud in the retina but there are loads at the FOVEA
Optic Nerve
Carries impulses from receptors to brain
Iris Reflex
Adjusting for bright light.
1) very bright light triggers a reflex that makes pupil smaller allowing less light in.
2) Opposite process happens in dim light. Brain orders radial muscles to contract which a
makes pupil bigger.
To look at a distant object
Ciliary muscles relax which allows suspensory ligaments to pull tight. This makes the lens go thin (less curved) so it refracts light by a smaller amount
To look at a near object
The ciliary muscles contract which slackens the suspensory ligaments. The lens becomes fatter ( more curved ). This increases the amount by which it refracts light.
Short sighted people
They are unable to focus on distant objects. This occurs when the cornea or lens bend light too much or the eyeball is too long.
The images of distant objects are brought into focus in front of the retina.
Long sighted people
They are unable to focus on near objects. This occurs when the cornea or lens don’t bend light enough or when the eyeball is too long.
Images of near object are brought into focus behind the retina.
Hormones
Chemical release directly into blood. They’re carried by plasma to other parts of body but only affect particular cells ( target cells )
Hormones control things in organs and cells that need constant adjustment.
They are produced in glands, travel slowly and tend to have long lasting effects.
Adrenaline
Source - Adrenal glands (on top of kidneys)
Role - Readies body for a flight or fight response
Effects - Increases heart rate, blood flow to muscles and blood and sugar level
Insulin
Source - Pancreas
Role - Helps control blood sugar level
Effects - Stimulates the liver to turn glucose into glycogen for storage
Testosterone
Source - Testes
Role - Main male sex hormone
Effects - Promotes male secondary sexual characteristics
Progesterone
Source - Ovaries
Role - Supports pregnancy
Effects - Maintains uterus lining
Oestrogen
Source - Ovaries
Role - Main female sex hormone
Effects - Controls menstrual cycle and promotes female secondary sexual characteristics.
Hormones vs Nerves
Hormones
- Slower message
- Act for long time
- Act in a more general way
Nerves
- Very fast message
- Act for short time
- Act on very precise area
Homeostasis
The maintenance of a constant internal environment,
Water
Water is taken into the body as food and drink and is lost through skin in sweat, via lungs in breath, via kidneys as urine and via faeces.
Homeostasis:
- when is hot or when your exercising you sweat a lot, you will produce less urine but it will be more concentrated. you will also lose more water through your breath when you exercise because you breathe faster
- on a cold day or when your not exercising you don’t sweat as much
youll produce more urine which will be pale (as its more diluted)
body temp homeostasis
all enzymes work best at optimum temp (ab 37º)
- brain acts as a thermostat, its sensitive to blood temp in brain and receives messages from temp receptors in skin that provide info ab skin temp
based from signals from these receptors your CNS can activate necessary effectors to make sure temp stays just right
homeostasis when your too hot
- lots of sweat is produced - when it evaporates it transfers energy from your skin to the environment, cooling you down
- blood vessels close to surface of skin widen (vasodilation) allowing more blood near the surface so it can transfer more energy into surroundings, which cools you down
- hairs lie flat
homeostasis when your too cold
- very little sweat produced
- blood vessels near surface of skin constrict ( vascoconstruction), so less blood flows to the surface, and less energy is transferred to surroundings
- shivering increases rate of respiration, which transfers more energy to warm body, exercise does the same
- hairs stand on end to trap an insulating layer of air, which helps keep you warm
smaller organisms homeostasis
they can cool quicker
- they have a bigger surface area to volume ratio, so they gai or loose heat faster because tehre is more area for heat to transfer across. This is good in hot climates as they loose body heat more easily but dangerous in cold climates
animals in cold conditions have compact (rounded shape) to keep surface area to a minimum reducing heat loss
plants and stimuli
-plants also icrease their chances of survival by respoding to chages in environment such as:
- they sense direction of light and grow towards it so they maximise light absorption for photosynthesis
- they can sense gravity so roots and shoots grow in right direction
- climbing plants have sense of touch si they mind new thinfs to climb to reach sunlight
can respond to prescence of predetors:
- produce substances toxic to predetors to avoid being eaten
can respond to abiotic stress (non-lining natural threats) such as:
- carrots produce antifreeze proteins at low temperatures the proteins bind to ice crystals and lower the temperature that water water freezes stoping ice crystals from forming
auxins
plant growth hormones
- control growth in tips of shoots and roots, they move through plant in solution (dissolved in water).
- its produced in tips and diffuses backwards to stimulate cell elongation process that occurs in cells just behind the tips
- promotes growth of shoot but inhibits growth of roots
- they are involved in growth responses of plants to light (phototropism) and gravity (geotropism)º
auxin and shoot directions
shoots are positively phototropic
- when tip is exposed to light it accumulates more auxin on the side thats in the shade than the side in the light so cell elongates faster on the shaded side so yhe shoot bends towards the light
shoots are negatively geographic:
- when shoot is growing sideways gravity prodces an unequal distribution of auxin, with more on lower side causing lower side to grow faster bending shoot upwards
auxin and root direction
roots are positevely geotrophic
- a root sideways will have more auxi o lower side but in roots auxin inhibits growth so top will elongate faster and root will bend downwards
roots are negatively phototropic
- if root starts being exposed to some light, more auxin accumulates on shaded side so root bends downwards back into ground
