9 & 10. Response to Stimuli and Coordination Flashcards Preview

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Flashcards in 9 & 10. Response to Stimuli and Coordination Deck (67)
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Suggest why, during a period of intensive exercise, the metabolic rate of a nerve cell increases

-More nerve impulses means more Na needs to be removed from the axon
-Active transport of Na requires ATP


(Two neurones- one secretes acetyl choline (A), the other secretes GABA (B) - a substance that increases a membranes permeability to chloride ions- both form synapses with a neurone C) Suggest now impulses in neurone B would reduce the chances of an action potential in neurone C

-More negative inside/ hyper polarisation
-Requires more stimulation from acetylcholine/ Na/ more impulses


Explain the importance of a nocturnal earthworm moving towards (taxis) from darkness to low light intensities

Allows the worm to come to the surface at night


If the worm is touched, it responds by contracting all its segments rapidly. How can this movement be related to the fact that the nerve cord of a worm contains a number of axons which have a very large diameter?

The larger the diameter of the axon, the faster the rate of conduction of a nervous impulse


Worms were cultured at three different temperatures with food. They were then put on a plate with a temperature gradient on it. The worms moved towards the temperature at which they had been cultured.

Suggest an explanation for the worms' behaviour on the plate in the absence of food.

-Hungry so seeking food/ in absence of food respond to temperature
-Move toward temperature they were used to/ cultured in
-Associate this temperature with food
-(Then) stay in this temperature


Worms were cultured at three different temperatures with food. They were then put on a plate with a temperature gradient on it. The worms moved towards the temperature at which they had been cultured.

The biologist exposed the plates to dim, even light. Give two reasons why this was important.

-(Dim) Worms live in dark soil/ affected by bright light/ dim light is like normal environment
-(Even) Worms might move towards/ away from bright light/ to avoid creating a light gradient/ prevent worms showing phototaxis
-(Dim light) Ensures that heat from the light not a variable/heat from lamp could kill/ dry out worms


When treating patients with dementia, doctors recorded the amount of myelin in the brain for three types of dementia. They used a statistical test to compare the results for AD and LD. They obtained a value for P of 0.047. What does this show about the difference between the means of LD and AD? Use the words probability and chance in your answer.

-Probability of obtaining this difference by chance
-Is less than 5%
-Difference is significant

Allow converse for over 95%


*Graph shows myelin levels
Without dementia - 52 units
With VaD - 25 units
With AD- 35 units
With LD- 41 units... None of the SE values overlap*

A student concluded that there was a relationship between the amount of myelin in a person's brain and whether or not they had dementia. Do these data support the conclusion?

-All dementia groups lower than control group
-Error bars do not overlap so the differences are significant
-Dementia may be due to other factors/ not only due to lack of myelin
-(Because) Big/ significant differences in myelin in different dementias
-Only small sample sizes/ only one study/ more data required


What is a stimulus and how are they detected?

How does the ability to respond to a stimuli increase the chances of survival for an organism?

A stimulus is a detectable change in the internal or external environment of an organism that produces a response.

They are detected through receptors.

Detecting the stimuli and responding increases the chance of the organism surviving to pass on their alleles and successfully reproduce if the stimulus is a predator, so they can get away from the predator, or extreme temperature so they will not overheat/ get hypothermia etc...


How do receptors work as a transducer?

They convert the energy of a stimulus into an electrical impulse that can then be processed by the organism and a response can occur.


Give examples of effectors.

And Systems


Compare the hormonal system and the nervous system in terms of
-Method of travel
-Type of transmission
-Origin of each
-Duration of effect caused by hormone/ impulse
-Where the effects of each are seen/ target organs

-Hormones travel through the bloodstream in the plasma whereas nerve impulses travel through the nervous system (neurones and synapses
-Nerves travel as electrical impulses whereas the hormonal system operates through hormones (proteins/ peptides and steroids)
-Hormones are secreted from glands whereas nerve impulses originate at the receptors where a stimulus is converted into an electrical impulse
-The nervous system produces short lived effects whereas the effects caused by the hormonal system are more long lived
-Nervous system a localised effect whereas the hormonal system has effects on any organ that contains the right receptor for the hormone- a more wide-spread response because it travels through the bloodstream.


Describe the sequence that occurs from detecting a stimulus to an action occurring (nervous system).

Stimulus --> receptor --> coordinator --> effector --> response


What is a taxis? What is a positive taxis vs a negative taxis?

A response in which the direction is determined by the direction of the stimulus (directional response).

Motile organism moves its whole body either away from an unfavourable stimulus (negative taxis) or towards a favourable one (positive taxis).


What are the two types of taxis?
*Hint: not positive and negative*

Give examples.

-Chemotaxis- bacteria move towards a region where glucose is more highly concentrated- increase their chances of survival as they get more food
-Phototaxis- Eg single celled algae move towards the light as they are photosynthetic and a greater light intensity increases their chances of food manufacture and therefore survival


What is a kinesis?
What is the purpose of a kinesis?

A non directional response where the increase in random movement increases with the intensity of the stimulus.

The purpose is to bring the organism back into more favourable conditions.


What is a tropism and what are the types of tropism(use examples)?

It is a growth movement of a plant in response to a directional stimulus.
-Phototropism- eg plants shoots growing towards light and plants roots growing away from light
-Geotropism- plants shoots grow away from the direction of gravity and plant roots grow towards the direction of gravity
-Hydrotropism- plant roots go towards water so that root systems develop where there is most water


What are the two major divisions of the nervous system? What are they made up from?

-Central nervous system - brain and spinal cord
-Peripheral nervous system - made up of pairs of nerves that originate from either the brain or the spinal cord.


How is the peripheral nervous system divided?

-Sensory neurones- nerve impulses from receptors towards the central nervous system
-Motor neurones- carry impulses away from the central nervous system to the effectors


What are the two subdivisions of the motor nervous system?

-Voluntary nervous system- carries nerve impulses to the body muscles and is under conscious control
-Autonomic nervous system- carries nerve impulses to glands, smooth muscle and cardiac muscle and is not under conscious control.


Describe the structure of the spinal cord.

Column of nervous tissue that runs along the back and lies inside the vertebral column for protection. Emerging at intervals along the spinal cord are pairs of nerves.


Describe the chain of events in a reflex arc for the example of withdrawing our hand from a hot flame.

-Stimulus- heat from the hot object
-Receptor- temperature receptors in our skin create nerve impulses in the sensory neurone
-Intermediate neurone (relay neurone) links the sensory neurone to the motor neurone in the grey matter of the spinal cord.
-Motor neurone- carries nerve impulse from the spinal cord to the effector muscle
-Effector, in this case a muscle is stimulated to contract
-Response- hand pulling away from the hot flame


What are the advantages of reflex actions?

-They do not require the brain as they are involuntary so they leave the brain free for more complex responses- therefore the brain is not overloaded with situations in which the response is always the same.
-Protect the body from harmful stimuli- they are not learned, they are innate responses
-They are FAST - pathways are very short with very few synapses (the slowest part because chemical transmission is slower than electrical transmission)


What are the two subdivisions of the autonomic nervous system? How are they antagonistic?

-Sympathetic nervous system- stimulates effectors and so speeds up an activity (controls activities in eg strenuous exercise or powerful emotions).
-Parasympathetic nervous system- inhibits effectors and so slows down activity (controls activities under normal resting conditions).

They are antagonistic as their effects usually oppose one another.


Describe how the heart is controlled by chemoreceptors

-High conc of CO2 in blood reduces the pH
-Chemoreceptors in the walls of the carotid arteries and aorta detect this and increase the frequency of nervous impulses to the centre in the medulla oblongata that increases heart rate
-This centre increases the freq of impulses via the sympathetic nervous system to the SAN which increases the heart rate
-Increased blood flow causes more carbon dioxide to be removed via the lungs
-CO2 level of blood returns to normal
-Chemoreceptors in the walls of the carotid arteries and aorta reduce the freq of impulses to medulla oblongata
-Medulla oblongata reduces freq on impulses to SAN so heart rate reduced to normal level


Describe how the heart rate is controlled by pressure receptors when the blood pressure is higher than normal or lower than normal.

-Pressure receptors are in the walls of the carotid arteries and aorta

-When blood pressure is too high- transmit a nervous impulse to centre in medulla oblongata that reduces heart rate. This centre sends impulses through the parasympathetic nervous system to the SAN which decreases the heart rate

-When blood pressure is too low- nervous impulses to the centre of the medulla oblongata that increases heart rate. This centre sends impulses via the sympathetic nervous system to the SAN which increases the heart rate.


What are the features of sensory reception as demonstrated by a pacinian corpuscle?

-Specific to a single type of stimulus- in this case, only responding to mechanical pressure

-Produces a generator potential by acting as a transducer- mechanical energy traduced into electrical energy


Describe the structure and function of a pacinian corpuscle.

-Respond to mechanical stimulation eg pressure
-Most abundant in soles of feet, fingers and external genitalia
-Sensory neurone in the centre of many layers separated by gel
-Mechanical pressure opens stretch gated sodium ion channels


What are the two types of light receptor in the eye and describe their structure, location and what they do, what type of light they respond to, what kind of visual acuity does each give.

-Rod cells
>Many rod cells sharing a single sensory neurone
>Allow us to see in black and white
>Allow us to see in low light intensities
>Concentrated at the periphery of the eye
>Low visual acuity

-Cone cells
>Each cone cell attached to its own sensory neurone
>3 types (red, green and blue) allow us to see in colour
>Allows us to see in high light intensities
>Concentrated at the fovea
>Gives high visual acuity


What is it called when many rod cells are attached to a single bipolar cell?

Retinal convergence