6.1 Detection and Response Flashcards
What is a stimulus?
A change in the environment
What is a receptor?
A cell or group of cells that detects the stimulus
What is an effector?
The structure that brings about the response to the stimulus change
What are the prefixes indicating the stimulus changes?
Photo - light Hydro - water Geo - gravity Thermo - heat Hygro - humidity Rheo - water currents Chemo - chemical Anemo - air current Baro - pressure
What is the stimulus response process?
Stimulus Receptor Coordinator Effector Response
What are the three types of response?
Taxes
Kineses
Tropisms
If a questions says what type of behaviour is shown - what do you put?
Either taxis, kinesis or tropism
Nothing else
What is taxes?
Movement in a specific direction that are directed by a stimulus such as light or food
Examples of taxes?
Euglena - shows positive phototaxes useful in photosynthesis
Earth worm - responds to water, gravity, light
Some bacteria - move to regions of high glucose concentration = positive chemotaxis
What is kineses? Example?
More random movements that are not directed by a stimulus
Eg Woodlice (prone to desiccation) - move randomly to find dark when in the light
What is tropisms? Example?
A growth movement of part of a plant in response to a directional stimulus
Roots - positive hydrotropism
Shoots - initially negative phototropism (as no light in soil)
When should a response be deemed positive or negative?
Taxes and tropisms are positive and negative
Whereas kineses can’t be positive or negative as it is random
In kineses when does an organism move more frantically?
The more unfavourable the stimulus the more rapidly the organism moves and the more frequently it changes direction
What are auxins?
Plant growth factors
NOT hormones
What is the most common auxin?
IAA
Indole-3-acetic acid
What is significant about the different parts of a plant?
They have different optimum auxin concentrations
What do the concentrations of auxins lead to in the stems and roots?
A high concentration of IAA in the stem stimulates growth (the cells don’t replicate but elongate the ones already there)
A high concentration of IAA in the roots inhibits growth
Why can growth be inhibited by too high a concentration of IAA?
As IAA is an acid it can denature the enzymes
Describe phototropism in flowering plants?
When reacting to sunlight
Cells in the tip of the shoot produce IAA
IAA is distributed evenly down the stem
The light causes the IAA to move to the ‘shaded’ side
A greater concentration of IAA causes cell elongation on the ‘dark’ side
The shades side grows faster so the shoot grows towards the light
How does elongation take place?
It activates a protein pump which lowers the pH
This activates an enzyme to break bonds in the cell wall - loosening the cell wall
So the shoot bends to the light
Describe geotropism in flowering plants?
When reacting to gravity
Cells in the tip of the root produce IAA
This settles at the bottom, no matter the branch
The greater concentration of IAA at the bottom causes cell elongation on the other side and bends down as a result (as high IAA in roots inhibits growth)
What happens if a tip of the shoot is covered or has been cut off?
It will grow normally with no directional response i.e straight up
What happens if a tip of the shoot is exposed with the rest buried in sand?
The shoot behaved as normal showing it was definitely the tip that caused the response to light
What is the nervous system made up of?
The peripheral nervous system
The central nervous system
What is the central nervous system comprised of?
The brain
The spinal cord
What makes up the peripheral nervous system?
Sensory nervous system
Motor nervous system
What is involved in the motor nervous system?
Somatic (mostly voluntary)
Autonomic (mostly involuntary)
What is the autonomic aspect made up of?
Sympathetic - fight or flight
Parasympathetic - rest and digest
Go through the reflex arc?
Stimulus Receptor Sensory neurone Intermediate neurone Motor neurone Effector Response
How are neurones drawn?
All neurones go into the grey matter with the intermediate neurone completely in there
As a ball at the start then a line
There’s a curve as though to fit the ball of the next neurone but not touching to show the synapse
When labelling a neurone what must you do?
Write the name and the label MUST be touching the neurone (not just ‘near’ it)
Why are reflex arcs important?
They protect the body from harmful stimuli
They are fast
They are involuntary
They don’t involve the conscious part of the brain
What are effectors?
A muscle - contacts
Or
A gland - secretes
What is monosynaptic and polysynaptic? Significance?
Mono - only one synapse
Poly - many synapses
Mono synaptic responses are much quicker
What are some factors of sensory receptors?
All are specific to a single type of stimulus
All produce a generator potential (start of a nerve impulse) by acting as a transducer
What are some examples of sensory receptors?
The pacinian corpuscle
The retina of the human eye
How does the pacinian corpuscle transduces the mechanical of a stimulus into a generator potential?
Putting pressure on the capsule all the consequent layers and gel are squished and forced together
The pressure on the neurone ending causes the stretch mediated Na+ channels to open
This causes an influx of Na+ using facilitated diffusion which changes the charge as there is now a greater positive charge in the neurone ending due to depolarisation
Leading to a generator potential
What happens if there is a weaker stimulus on the pacinian corpuscle?
A weak stimulus isn’t registered due to not enough pressure therefore not enough stretching of the membrane
Therefore no generator potential
What is the function of these in the eye?
Choroid
Fovea
Optic nerve
Retina
Choroid - absorbs light passed through the retina containing melanin and blood vessels
Fovea - high density of cone cells
Optic nerve - contains sensory neurones
Retina - contains photoreceptors
What is the function of these in the eye?
Lens
Sensory ligaments and ciliary muscles
Cornea
Iris
Lens - made up of proteins
Sensory ligaments and ciliary muscles - change the shape of the lens
Cornea - main site of refraction
Iris - controls the amount of light entering (using antagonistic muscle action)
What is involved in making up the retina?
Rod cells
Cone cells
Bipolar neurone
Ganglion cells
Information about cone cells?
High in the fovea
Iodopsin is the pigment that is broken down
3 types of iodopsin blue/green/red sensitive
Each cone cell is connected to a separate bipolar neurone
High visual acuity
Low sensitivity in low light
Why do cone cells have high visual acuity?
Several stimuli hit each cone cell which is connected to a separate bipolar neurone
So many individual impulses can be sent to the brain
Information about rod cells?
High in the side of eye
Rhodopsin is the pigment that is broken down
Many rod cells are connected to a each bipolar neurone
Low visual acuity
High sensitivity in low light
Why do rod cells have a high sensitivity in low light?
Many rod cells are stimulated per bipolar neurone allowing the threshold of neurotransmitter to be reached
Therefore nerve impulses are transmitted to the brain along the optic nerve
Which of the pigments in rod/cone cells are more easily broken down?
Rhodopsin in rod cells
What happens to pigments when they are broken down?
They have lots of mitochondria allowing aerobic respiration to take place forming ATP
The energy from ATP will used to resynthesise the pigment
What causes vision to be in colour?
Different wavelengths of light
Describe the events controlling the cardiac cycle?
Wave of excitation from SA node spreads across both atria so they contract and push blood into the ventricles
Wave reaches AV node - along purkinje fibres of bundle of His
Atria relax
Wave reaches bottom of ventricles + contract from the bottom up - increased pressure causes AV valves to close
Forces blood in pulmonary artery + aorta through SL valves
Ventricles relax, pressure below aorta, SLV shut - then the cycle repeats
What are the sections of the brain we need to know?
Cerebral cortex - consciousnesses, intelligence, memory and language
Cerebellum - coordinates movement and balance
Medulla - controls automatic actions (heart beat and breathing)
How does heart rate increase?
Increased aerobic respiration leads to more CO2 production
Carbonic acid in the blood leads to a decrease in pH detected by chemoreceptors in the aorta and carotid arteries
A sensory neurone sends an impulse to the cardiac acceleratory centre in the medulla of the brain
More impulses are sent down the sympathetic nerve to the SA node
The cardiac muscle will contract more often
Why would heart rate decrease?
Decreased aerobic respiration leads to less CO2 production
Less Carbonic acid in the blood leads to a increase in pH detected by chemoreceptors in the aorta and carotid arteries
A sensory neurone sends an impulse to the cardiac inhibitory centre in the medulla of the brain
Fewer impulses are sent down the parasympathetic nerve to the SA node
The cardiac muscle will contract less often
What is the equation for cardiac output?
Cardiac output = stroke volume x heart rate
What happens when there is an decrease in blood pressure?
The baroreceptors in the aorta and carotid arteries detect the decrease in pressure
A sensory neurone sends an impulse to the cardiac acceleratory centre in the medulla of the brain
The impulse goes down the sympathetic nerve to the SA node
The cardiac muscle will contract more often
Leading to a faster heart beat
What happens when there is an increase in blood pressure?
The baroreceptors in the aorta and carotid arteries detect the change in pressure
A sensory neurone sends an impulse to the cardiac inhibitory centre in the medulla of the brain
The impulse goes down the parasympathetic nerve to the SA node
The cardiac muscle will contract less often
Leading to a slower heart beat
Explain an increase in pressure with more salt in the blood?
More salt = lower water potential
So water moves in via osmosis
Leading to an increase in volume and therefore increase in pressure
