Stimuli and response and nervous coordination Flashcards
Why do organisms respond to changes in their environment
To increase survival chance
Define Taxis response
A simple response directional response in which a whole organism moves towards or away from a stimulus
Define Kinesis response
Random movement of a whole organism in response to a non directional stimuli eg temperature or humidity. this may be an increase/decrease in speed or turning frequency
How do plants respond to stimuli
Using growth factors
What is IAA
Auxin. It is a plant hormone. It allows plants to be photo and gravotrophic
Where in a plant is IAA produced
The tips of roots and shoots
How does IAA effect cells in shoots and roots
It promotes cell elongation in shoots and restricts it in roots
Outline the pathway of a simple reflex arc
Stimulus - receptors - sensory neurone - CNS- relay neurone - motor neurone - Effectors- response
What three neurones are involved in a simple reflex arc
Sensory neurone, replay neurone, motor neurone
What purpose does a simple reflex arc serve
Protective response to increase survival chance
What do the Pacinian corpuscles detect
Mechanical pressure
What ion channels are present in the Pacinian corpuscles
Stretch mediated sodium ion channels
What is established when a receptor is stimulated
A generator potential
When is an action potential triggered
When a generator potential exceeds a threshold
What is the connective tissue called that is wrapped around the sensory nerve ending in Pacinian corpuscles
Lamellae
What two types of cells detect light in the eyes
Rod cells
cone cells
Which type of cell has high visual acuity
cone cells
Why do the two types of cells have different visual acuity
Several rod cells connect to one bipolar neurone. This means that they are sensitive but have low visual acuity as it isn’t possible to tell which exact rod cell(s) was stimulated
A cone cell is attached to a single bipolar neurone. This means that they have high visual acuity
Which of the two types of cell is most sensitive to light
Rod cells
Which type of cell is responsible for trichromatic vision
cone cells
What is responsible for the blind spot of an eye
The location where the optic nerve leaves the eye is the blind spot
What neurone connects photoreceptors to the optic nerve
bipolar neurone
What is different about myogenic muscle tissue
It can contract and relax without receiving signals from nerves
Cardiac muscle fibres are Myogenic
Outline the roles of the sinoatrial node (SAN)
Sends regular electrical impulses to the atrial walls to control heart rate. Causes right and left atria to contract simultaneously
Often referred to as pacemaker
Outline the roles of the Atrioventricular node (AVN)
Passes the impulse to the bundles of His. Has a slight delay to ensure atria are empty
Outline the roles of the Bundle of His
Through the atrioventricular septum to the base of the ventricles where the bundle branches into smaller fibres of purkyne tissue. The wave of excitation is released from the purkyne tissue causing the ventricles to contract quickly at the same time from the bottom of the heart upwards
Outline the roles of the Purkyne tissue
This tissue is fibres from the bundle of His. It carries waves of electrical activity into the ventricle walls, causing simultaneous contraction from the bottom up
What section of the brain subconsciously controls the rate at which the SAN fires
Medulla
Where are the baroreceptors located and what are they stimulated by
Aorta and carotid arteries - pressure
Where are the chemoreceptors located and what are they stimulated by
Aorta, carotid arteries and medulla. O2 levels, CO2 levels and Ph (which indicates O2 levels)
What effectors are related to slow down heart rate
Acetylcholine, which binds to receptors on the SAN
What effectors are related to speed up heart rate
Noradrenaline, which binds to receptors on the SAN
When low 02, high CO2 or low blood pH is detected, how is heart rate changed to bring back normal levels
Heart rate is increased. This is done by releasing noradrenaline
State the equation linking Cardiac Output (CO), Stroke Volume (V) and Heart Rate (R)
CO=VxR
What is a myelin sheath
An electrical insulator
What ells are myelin sheaths made from
Schwann cells
What is the term for the bare patches of membrane between the cells
Nodes of Ranvier
What are sodium ion changes concentrated at
Nodes of Ranvier
In a myelinated neurone, where does depolarisation occur
Nodes of Ranvier
How does myelination effect the speed of conduction
Increases it all less depolarisation has to occur
Give two other features that would effect speed of conduction
Temperature
Axon Diameter
When a resting potential is established how is the outside of a cell charged in comparison with the inside
It is positively charged
What proteins create and maintain a resting potential
Potassium ion channels, Sodium potassium pumps
Why are there more sodium ions outside the cell than on the inside
They are actively transported out and the cell membrane is not very permeable to them
When a stimulus is detected, what channel proteins open
Na+ channels open
What occurs when the threshold is reached
Lots more Na+ channels open
When repolarisation occurs, how does the membrane permeability to sodium and potassium change
Impermeable to sodium, permeable to potassium
What effect does the refractory period have on nervous impulses
Acts as a time delay so impulses don’t overlap. Ensures impulses are discrete. Means there is a limit to how often impulses can fire
As described thy the all-or-nothing principle, how would a bigger stimulus effect the size of an action potential
No change
As described thy the all-or-nothing principle, how would a bigger stimulus effect the frequency at which an action potential fires
Faster frequency
What is contained in the vesicles of the presynaptic knob
Neurotransmitters
What is the gap between the cells at the synapse called
Synaptic cleft
Why are synapses unidirectional
Only the post-synaptic neurone has receptors
When an action potential arrives at a Cholinergic synapse, what three steps happen
Ca2+ ions move into presynaptic knob. Vesicles with Each fuse with membrane of synapse releasing neurotransmitter. This diffuses across the synaptic cleft and activates the receptors. The neurotransmitter is then broken down by AChE
What is summation in relation to synapses
Where the effect of many neurones, or one stimulated multiple times, is added together
State the names of both types of summation
Spatial summation
temporal summation
How is ACh removed from he synaptic junction
AChE breaks it down and the products are reabsorbed by the presynaptic neuyrone
What are stored in clefts at a neuromuscular junction
AChE
suggest 2 advantages of simple reflexes
rapid protect against damage to the body do not have to be learnt help escape predators enable homeostatic control
stimuli are detected by
receptors
a response to a stimuli is controlled by a
coordinator (brain)
a response to a stimuli (eg hormone secretion) is produced by
an effector
Movement of a whole organism towards light is called, and give an example of such an organism
phototaxis (algae)
Positive taxis is
movement towards a stimulus by a whole organism
Negative taxis is
movement away from a stimulus by a whole organism
define tropism
the growth of part of a plant in response to a directional stimulus eg light, gravity or water
when plants grow towards light it is called
positive phototropism
when plant shoots grow away from gravity it is called
negative gravitropism
When plant roots grow away from light it is called
negative phototropism
Why do woodlice increase their rate of turning if they exit favourable conditions
to increase the probability that they will reenter the favourable conditions
why do woodlice decrease their rate of turning and move rapidly after spending a while in unfavourable conditions
to increase the chances that they will pas through the unfavourable conditions and enter more favourable ones
When roots grow towards water it is called
positive hydrotropism
give the location of the osmoreceptors in the body of a mammal
hypothalamus
the pressure receptors in the skin are called
pacinian corpuscles
what is a transducer
a receptor cell which converts one form of energy (eg light) into a form that can be understood by the body (eg an electrical impulse)
What is a stretch mediated sodium channel
a sodium channel protein whose permeability to sodium ions increases they they are deformed
In which part of the eye are light receptor cells found
the retina
rod cells are responsible for _____ vision
black and white
why can rod cell images only be seen in black and white
they can not distinguish between different wavelengths of light
rod cells are sensitive to ____ intensity light
low
cone cells are sensitive to _____ intensity light
high
which pigment, that breaks down in low intensity light, is found inside rod cells
rhodopsin
How many types of cone cell are there
3
each of the 3 types of cone cell contain a specific group of pigments called
iodopsins
does iodopsin break down in the presence of high or low intensity light
high
where does the lens of the eye focus light
fovea
where is the fovea
central point in the retina
outer periphery of the retina contains ____ cells
rod
the fovea contains ____
cone
what are cholinergic synapses
synapses that use acetylcholine
What is a synapse
the junction between a neurone and the next cell
what ensures that impulses cross the synapse in one direction only
Neurotransmitter is released from the presynaptic knob. Receptor for the neurotransmitter is only found on the post synaptic membrane
what happens to the neurotransmitter once they have attached to the receptors on the post synaptic membrane
They are broken down by enzymes and their products are taken back into the neurone
What stimulates the synaptic vesicles to move towards the presynaptic membrane in a cholinergic synapse
Calcium ions diffuse into the synaptic knob causing the synaptic vesicles to move towards the presynaptic membrane
What happens when the acetylcholine bind with the receptors on the post synaptic membrane
Sodium channels open and sodium floods in. If the threshold is reached an action potential is generated
How is acetylcholine removed from the synaptic cleft
Acetylcholinesterase breaks acetylcholine and the products are reabsorbed to make more acetylcholine
What is temporal summation
where there are two or more nerve impulses that arrive in quick succession from the same presynaptic membrane and action potential is more likely to occur
What is spatial summation
When many neurones connect to one neurone. The small amount of neurotransmitter released from each of these neurones can be enough to reach the threshold value
What are the nodes of Ranvier
Bare areas of neurones that are not insulated by myelin
