Topic 14: Response to the environment Flashcards
What are 4 types of environmental stimuli
- Mechanical
- Thermal
- Chemical
- Electromagnetic
What is Taxis
- A simple response whee an organismm will move its entire body away from or towards a stimulus
What would you call the type of stimulus that induces negative taxis
unfavourable stimulus
What would you call the type of stimulus that induces positive taxis
Favourable stimulus
What is the difference between negative and positive taxis
- negative taxis is when the organism moves away from the stimulus
- positive taxis is when the organism moves towards the stimulus
What is kinesis
- Simple response where an organism changes the speed of movement, and the rate it changes direction
What is tropism
- Simple response where a part of the plant grows towards or away from a stimulus
What do you call plant hormones + name one
- growth factors
- Auxin (indoleacetic acid)
Name three environmental factors that plants will respond to
- light
- water
- gravity
What is a growth factor
A hormone-like substance produced by plants that stimulates a variety of plant processes
Where is IAA found
Shoots and roots
What is the difference in function of IAA between roots and shoots
- In roots - inhibits growth
- In shoots - elongates cells *promoting growth
Explain phototropism in shoots
- IAA diffuses to the darker side of the shoot,
- IAA stimulates cell growth, making the cells elongate,
- which bends the shoot towards the light source (positive phototropism)
- to maximise photosynthesis
Explain phototropism in roots
- IAA diffuses to the dark side of the roots
- IAA will inhibit cell growth on the side of the roots
- Causing the root to bend away from the light source (negative phototropism)
- Allowing the root to anchor the plant further into the soil
Explain gravitropism in the shoots
- IAA moves towards the lower side
- IAA will stimulate cell growth in the lower side, causing cell elongation
- This causes the shoot to bend upwards, against gravity (negative gravitropism)
Explain gravitropism in roots
- IAA in roots moves towards the lower side
- IAA will inhibit cell growth in the lower side
- Causing the root to bend towards gravity (downwards), (positive gravitropism)
What are the two systems for coordination
- Nervous system
- Endocrine system
What is the difference between the nervous system and the endocrine system
- The nervous system uses nerves, and electrical impulses
- The endocrine system uses hormones and chemicals
Compare and contrast the nervous system and endocrine system
**Nervous system **
- communication by nerve impulses
- transmission by neurones
- rapid transmission
- nerve impulses travel to specific parts of the body
- response is localised
- response is rapid
- response is short lived
**Endocrine system **
- Communication is by hormones
- Transmission in the blood system
- Transmission is relatively slow
- Hormones travel to all parts of the body, only target cells respond
- Response is widespread
- Response is slow
What are the two major divisions of the nervous system
- The Central nervous system (CNS)
- The peripheral nervous system (PNS)
What does the CNS consist of
- the brain
- the spinal cord
What does the PNS consist of
- Sensory neurones
- ## Motor neurones
Within the PNS, what are the two types of nervous systems, within the motor nervous system
- Voluntary nervous system (conscious)
- Autonomic nervous system (subconscious)
What are the advantage of the reflex arch
- protect us from harm
- they are fast
- they are involuntary (the brain isnt involved)
What is a reflex
An involunatry response to a sensory sitmulus
Describe the steps of the reflex arch
- Stimulus
- Receptor
- Sensory neurone
- Relay neurone
- Motor Neurone
- Effector
- Response
What are effectors
- muscles / glands that will carry out a response
What are the three types of neurones
- Relay neurone
- Sensory Neurone
- Motor neurone
State the 5 features of a neurone
- Dendrons / dendrites
- Axon
- Cell Body
- Schwann cells
- Myelin Sheath
What are shwann cells and what do they do
- Cells that surrond the axon, protecting it, providing electrical insulation and forming the myelin sheath
Name 6 types of receptors
- Photoreceptors (light)
- Mechanoreceptors (pressure)
- Chemoreceptors (chemicals)
- Thermoreceptors (temperature)
- Electroreceptors (electrical stimuli)
- Magnetoreceptors (magnetism)
What kind of stimulus does the pacinian corpuscle respond to
- pressure
How does the pacinian corpuscle work
- Pressure is applied in the fingertips
- The p.c has mechanoreceptors
- The sensory neurone has stretch-mediated sodium channels, and when they feel pressure, they will bend, allowing Na+ to enter the cell, creating a generator potential, and allowing a response
What are the two types of photoreceptors in the retina
- rods
- cones
Explain why rod cells only process images in black and white
They cannot detect different wavelengths of light. They can detect light of very low intensity
Explain retinal convergence
- Rod cells can detect light of low intensity, however becaue many rod cells connect to one sensory neurone
Explain how rod cells create a generator potential
- Pigment within rod cells, rhodopsin, must be broken down by light energy
- Low intensity light is enough to break it down
- Enough rhodopsin must be broken down for the threshold to be met within the bipolar cells, which link the receptors to the sensory neurone
Explain spatial summation
Where several cells pass on a message to a single recieving cell (many rod cells will connect to a single bipolar cell)
What is a disadvantage of retinal convergence
- Retinal convergence means that the brain cannot distinguish between the separate sources of light that are stimulating the rod cells. Two sources of light close together cannot be seen as separate, therefore rod cells give low visual acuity
What is another word for resolution when talking about the eye
Visual acuity
How many types of cone cells are there and what are there differences
3 types
containing diff iodopsin pigments ; red, green, blue
What cells percieve light and what cells percieve in black and white
Light - rod cells
Black and white - cone cells
When is iodopsin broken down
Only in high light intensities.
Why can you not see colour in the dark
- Colour is percieved by the cone cells
- Cone cells require the break down of iodopsin, in order to create a generator potential and see light, yet this can only happen within high light intensities
- because there is no spatial summation
- therefore in the dark, where there is low light inensity, you cannot see wavelengths of light, that show us colour
What kind of visual acuity do cone cells give, and what do rod cells give
- cone cells, high visual acuity
- rod cells, low visual acuity
What is the part of the retina where light is focused by the lens
The fovea
Where do u find a high amount of cone cells
Near the fovea
Describe the distribution of rod cells in the retina
The rod cells increase as you move away from the fovea
State the three stages of the cardiac cycle
- diastole
- atrial systole
- ventricular systole
What does myogenic muscle mean
Cardiac muscle is myogenic
- contractions are initiated within the muscle itself, rather than impulses (neurogenic)
What controls the rate of contraction in the heart
Waves of electrical activity in the nervous system
Where is the sinoatrial node located
Top right corner of the right atrium
How does the SAN cause cardiac msucle to contract
- SAN is a tissue that can release a wave of electricity
- which is depolarisation
- when this depolarisation reaches the cardiac muscle, it causes it to contract
Where is the atrioventricular node (AVN) located
near the border of the right and left ventricle, but still within the right atrium
What is the septum
Thick wall in between the left and right ventricle. Within the septum are fibres called the Bundle of His
Describe how the Bundle of His, and purkyne fibres run
The Bundle of his run from the top of the ventricle, connected to the atrioventricular node, all the way through the septum, down into where they branch into the purkyne fibres, which run around the bottom and side walls of the ventricles
Explin what causes atrial and ventricular systole
- The SAN will detect a change
- It will release a wave of depolarisation which will travel across the atria, causing tem to contract in atrial systole.
- There is a non-conductive layer between the atria and ventricles, to prevent them contracting at the same time.
- The AVN will release another wave of depolarisation, which will travel through the Bundle of His, down the septum, and into the purkyne fibres.
- The apex of the ventricles will contract first, then the rest of the walls contract
What region of the brain controls the heart rate
Medulla oblongata
What is the difference between the two centres of the medulla oblongata
- one centre increases heart rate
- one centre decreases heart rate
Describe the centre of the medulla oblongata that increases heart rate
- sympathetic nervous system
- helps us cope with stressful situations
- positive feedback
Describe the centre of the medulla oblongata that decreases the heart rate
- parasympathetic nervous system
- helps control activites under resting conditions
- negative feedback
What is the danger of too high blood pressure
- damage the walls of the arteries
What is the danger of too low blood pressure
not enough oxygenated blood getting around the body to the respiring cells and removing waste
Where do you find chemoreceptors and baroreceptors (pressure receptors)
Aorta and carotid arteries
Whys is a low pH a problem and how is it caused
- caused by buildup of Carbon dioxide and lactic acid during respiration, which forms carbonic acid, reducing the pH
- Excess acid can cause enzymes to denature
Explain the response to an increase in pressure
- (stimulus) increase pressure
- (receptors) detected by pressure receptors in the walls of the aorta and carotid arteries
- (coordinator) electrical impulses sent to the medulla oblongata. Impulses sent by parasympathetic nervous system to the SAN in the heart, to decrease the frequency of electrical impulses
- (effector) cardiac tissue, sinoatrial node tissue sends less waves and less contractions
- (response) reduced heart rate
Explain the response to an decrease in pressure
- (stimulus) decreased pressure
- (receptors) detected by pressure receptors in the walls of the aorta and carotid arteries
- (coordinator) electrical impulses sent to the medulla oblongata. Impulses sent by sympathetic nervous system to the SAN in the heart, to increase the frequency of electrical impulses
- (effector) cardiac tissue, sinoatrial node tissue sends more waves and more contractions
- (response) increases heart rate
Explain the response to an decrease in pH
-(stimulus) decrease pH
- (receptors) detected by chemoreceptors receptors in the walls of the aorta and carotid arteries
- (coordinator) electrical impulses sent to the medulla oblongata. Impulses sent by sympathetic nervous system to the SAN in the heart, to increase the frequency of electrical impulses
- (effector) cardiac tissue, sinoatrial node tissue sends more waves and more contractions
- (response) increased heart rate to pump blood faster and remove CO2
Explain the response to an increase in pH
- (stimulus) increase pH
- (receptors) detected by chemoreceptors receptors in the walls of the aorta and carotid arteries
- (coordinator) electrical impulses sent to the medulla oblongata. Impulses sent by parasympathetic nervous system to the SAN in the heart, to decrease the frequency of electrical impulses
- (effector) cardiac tissue, sinoatrial node tissue sends less waves and less contractions
- (response) decreased heart rate to pump blood slower and allow CO2 to form carbonic acid, and to allow for lactic acid
