Survival And Response Flashcards
How do organisms increase chance of survival
Responding to changes in their response external and internal environment eg. Avoiding too hot places
What is a stimulus
A change in the internal/external environment
What are receptors
Detect stimuli
Give 2 examples of receptors
Cells
Proteins on plasma membrane
What are effectors
Cells that respond to the stimulus
How do receptors communicate with effectors
Nervous system
Hormonal system
What is a sensory neurone
Transmit electrical impulses from receptors to the cns
What is a motor neurone
Transmit electrical impulses from cns to effectors
What is a relay neurone
Transmit electrical impulses from sensory neurone to motor neurone
What chemicals take info from one neurone to another
Neurotransmitters
What is the cns
Brain
Spinal chord
What is the peripheral nervous system
Neurones that connect cns to the rest of the body
What is the somatic nervous system
Control conscious activity
What is the autonomic nervous system
Controls unconscious activities
What is the sympathetic nervous system
Fight or flight
Makes body ready for action
What is the parasympathetic nervous system
Calms body
Rest and digest system
What is a reflex
Body responds to stimulus without a conscious decision
Why do reflex’s help survival
Don’t have to spend time devising on response
So very rapid
Draw a simple reflex arc
Receptor Sensory neurone Relay neurone (in grey matter of spinal chord) Motor neurone Effector
When can a reflex be overridden
When there is a relay neurone involved
Why the nervous system localised
Neurotransmitters are secreted directly onto target cells
Why is the nervous system short lived
Neurotransmitters are quickly removed once they’ve done their job
What is the nervous system Rapid
Electrical impulses are very fast
How do plants increase chance of survival with reference to light
Grow towards light
Maximum photosynthesis
How do plants increase chance of survival with reference to gravity
Shoots grow down in the right direction
Define tropism
Plants response to a directional stimulus
What is a positive tropism
Plant grows toward stimulus
What is a negative stimulus
Plant grows away from the stimulus
What is phototropism
Growth of plant in response to light
+ = towards light
- = away from light
What is gravitropism
Growth of plant in response to gravity
+ = grow Down
- = grown up
What are growth factors
Hormone like chemicals that speed up or slow down growth
Where are growth factors produced
Produced in growing regions of plant (shoots and roots)
What does auxin do in shoots
Promotes growth by cell elongation
Cell walls can stretch more
At roots what is the effect or roots
Inhibit growth
What type of response does IAA respond to
Tropism
How does IAA move in the plant
Diffusion and AT
Phloem
What does an uneven distribution of IAA mean
Uneven growth
What does IAA do in response to phototropism
IAA moves to the more shaded parts
Shoots = IAA increase on shaded side. Cells elongate. Shoot bends towards the light
Roots = IAA increases in shaded side. Growth inhibited. Root bends downwards
What does IAA do in response to gravitropism
IAA moves to the underside
Shoots = IAA increases on lower side. Cells elongate. Shoot grows up
Roots = IAA increases on lower side. Growth inhibited. Root grows down
What is a taxes
Animal response
Towards or away directional stimulus
Example of taxes
Light
What is a kinesis
Animal response
Non directional stimulus
Example of kinesis
Humidity
How does a photo taxes help woodlice
Move away from light source
Keeps them concealed under stones in day away from predators and in damper conditions to reduce water loss
How does woodlice benefit from a humidity kinesis
High humidity = move slow and change direction less
Low humidity = move faster and change direction more to find a new area
It reduces water loss and keeps them concealed from predators
Why are receptors specific
Detect one stimulus
What is a resting potential
Difference in charge between outside of cell and inside. Generated by Na/K pumps. Causes a pd.
What is a generator potential
Stimulus detected Cell membrane gets excited More permeable More ions move in and out of cell Changes pd
What happens to the generator potential with a bigger stimuli
Excites membrane more More permeable More ions can move in Bigger change in pd Larger generator potential
What is an action potential
The generator potential reaches the threshold potential
What is the strength action potential measured by and why
Father frequency
Because all action potentials are the same strength
What type of receptor is a pacinian corpuscle
Mechanoreceptors (detect pressure)
Where are pacinian corpuscles
Skin
What is the stricte of a pacinian corpuscle
Contain sensory nerve ending wrapped in lamellae
What causes a response at pacinian corpuscles
Lamellae are deformed
Press onto sensory nerve ending
Sensory nerve ending cell membrane stretches
Deforms stretch mediated sodium ion channels
Channels open and Na can diffuse into the cell
Forms generator potential
If it reaches threshold = action potential
What type of receptor is in the eye
Photo receptor
How does light enter the eye
Pupil
What controls how much light enters the eye
Muscles in the iris
How are light rays focused in the eye
By lens onto the retina which contains photoreceptors
What is the fovea
Area in retina that contains lots of photoreceptors
How are nerve impulses carries from the eye to the brain
The optic nerve
What is the blind spot in the eye
Where the optic nerve leaves they eye
Contains no photoreceptors
How do photoreceptors work in the eye
Light enters eye
Light absorbed by light sensitive optical pigments
Pigments are bleached
Causes chemical change
Membrane permeability increases to Na ions
Generator potential created
Reaches threshold potential
Impulse sent along bipolar neurone to optic nerve
Where are cone cells
Fovea
Where are rod cells
On the peripheral of the retina
Why are rod and cone cells different
Contain different optical pigments that are sensitive to different wavelengths of light
Rod = black and white
Cone = colour
How do u see different colours
The optical pigments (red, blue, green) in cone cells are stimulated in different amounts
Why are rod cells more sensitive than cone cells
Work well in dim light
Many rods join to one neurone (summation and retinal convergence)
Many weak generator potentials combine to reach the threshold potential and trigger an action potential
Why are cone cells less sensitive
1 cone cells connects to 1 neurone
Takes more light to reach the threshold potentiel
Why do rod cells have low visual acuity
Many rods join to the same neurone (summation)
Light from 2 points close together can’t be told apart
Why do cone cells have high visual acuity
Cone cells are close together 1 cone cell joins to 1 neurone Get an action potential from each cone cell Can distinguish between the 2 points (No summations)
Why is the heart muscle described as myogenic
Can contract and relax without receiving signals from nerves
What is the function of the SAN
Sets the rhythm of the heart by sending regular waves electrical impulses to the atrial walls
Where is the SAN
The right atrium
How does the heart contract
The SAN sends waves of regular electrical impulses to the atrial walls
Causes the right and left atria to constract at the same time
A band of non conduction collagen tissue prevents electrical impulses being sent directly to the ventricles
The electrical activity is sent to the AVN
AVN sends electrical activity to the bundle of his
There is a delay between AVN receiving the impulses and sending them to the bundle of his to make sure the atria have emptied before the ventricles contract
The bundle of his splits into purkyne tissue carrying electrical activity on the muscular walls of the ventricles so they contract at the same time
Why is there a delay between the AVN receiving electrical activity and sending it to the bundle of his
To make sure the atria has fully emptied before the ventricles contract
What part of the brain controls the SAN
Medulla oblongata
Why do animals need to change their heart rate to reasons to stimuli
Prevent fainting from low blood p
Make sure body has enough oxygen
What are pressure receptors called in the heart
Baroreceptors
Where are the baroreceptors
Aorta
Carotid artery
Where are chemo receptors for the hr
Aorta
Carotid artery’s
Medulla
What do hr chemoreceptors measure
PH of blood (indicates CO2 and O2 conc)
What happens at high blood p
Baroreceptors detect high blood p Impulses sent to medulla on parasympathetic neurones Secretes acetylcholine Binds to SAN Heart rate slows and blood p decreases
What happens to the heart at low blood p
Baroreceptors detect low p Impulses sent to medulla on sympathetic neurones Secrete noradrenaline Binds to SAN receptors Hr increases and blood p increases
What happens to the heart at high pH (low CO2)
Chemoreceptors detect Impulses sent to medulla on parasympathetic Neurones Secrete acetylcholine Binds to SAN receptors Herat rate decreases and ph decreases
What happens the the hr at low pH (high CO2)
Chemoreceptors detect Impulses sent to medulla along sympathetic neurones Secrete noradrenaline Binds to SAN receptors Hr increases and PH increase
