Internal and External Stimuli Flashcards
What is the order for stimuli response?
Stimuli Receptor CNS Effector Response
What is the CNS made up of?
Brain
Spinal cord
What re the two effectors?
Muscle= nervous Gland = hormonal
What is a stimulus?
Detectable change in the eternal or external environment
What is a receptor?
Any structure able to respond to a change
What is a coordinator?
The “switchboard” connecting information from the receptor to appropriate effector
What is an effector?
Causes a response (muscle or gland)
What is a response?
The output/change in behaviour
What are the three type of responses?
Tactic (taxis)
Kinetic (kinesis)
Trophic (tropism)
How do organisms react to an stimulus in their environment differently?
Whole organism or only part of it moves in response
Movement could be directional (+/-) or non-directional
Describe a kinetic response
Whole organism
Alteration in rate of movement
In response to change in intensity of stimulus
Non-directional
What is an example of a kinetic response?
When in dry conditions woodlice move rapidly and change direction
In drier areas = slow
Describe a taxis response
Whole organism
Directed by stimuli
Positive taxis = towards (+)
Negative taxis = away (-)
What is an example of a taxis response?
Some species of bacteria move away from waste products they produce
(Negative taxis)
Describe a trophic movement
Movement of part of the organism
Directed by stimulus
Growth response
What is an example of a trophic response?
Plant roots grow away from light and towards gravity
What are the three type of tropisms?
Hydrotropism
Geotropism
Phototropism
Where are auxins produced?
Apical meristem
What do auxins do?
Cause cells to grow
What is IAA?
Example of auxin
What do auxins do in response to tropism?
They move to shaded side = causes uneven growth = cell elongation towards sun
Where is IAA made?
By cells located throughout plant (not organs)
What is IAA produced in?
Small quantities
What does IAA affect inside of the plant?
Tissues close by + tissues the are released from
What does IAA affect overall?
Growth
What is the CNS?
Central nervous system
What is the PNS?
Peripheral nervous system
What is the peripheral nervous system
Pairs of nerves from the CNS travelling to limbs + organs (sensory neurone)
What are the two main divisions of the PNS?
Somatic - conscious = involves brain
Autonomic - subconscious = reflex actions
What is a reflex?
Involuntary response to a stimuli
What are the importance of reflexes?
Fast Automatic Protective Innate (not learnt) Doesn't involve the brain
Why is it important that reflexes are fast, etc?
Brain can focus on other complex behaviours
Escape predators, gain food or mates
Describe the process of a reflex arc
Sensory neurone takes electrical message from receptor to immediate neurone
Intermediate neurone relays message to motor from sensory
Motor receives from intermediate and sends to effector (muscle)
Muscle will contract so that hands pulls away from stimuli
What do receptors do?
Receive info + pass to CNS
Are receptors specific?
YES
What is sensory perception?
Making sense of information
What must happen to sensory information?
Must be converted into info the body understands
What converts sensory information?
Transducers
Why is the Pacinian Corpuscle important?
It is specific
Involved in sensory reception
Involves in sensory perception
What does the Pacinian Corpuscle respond to?
Mechanical pressure
Where is the Pacinian Corpuscle found?
Deep skin
eg. Fingers, toes, external genitalia + ligaments/tendons
What does the Pacinian Corpuscle act as?
Transducer
What is structure of the Pacinian Corpuscle?
Layers of connective tissue Viscous gel Blood capillaries (transports O2 + glucose for respiration = release energy) Neurone endings Sensory neurone (send message to CNS)
What happen when pressure is applied to the Pacinian Corpuscle?
Lamellae deforms
Applies pressure to neurone endings
Na channels stretch (stretch mediated Na channels) so Na+ can pass through
Increases permeability of membrane
Na+ move from high to low conc
Via facilitated diffusion
Influx of Na+ changes potential
Once at rest channels change back to normal size
Generator potential results in nervous response
What are the two light receptors in the eye?
Rod cells
Cone cells
What do both receptors in the eye act as?
Transducers
What do both receptors in the eye do?
Convert light energy into electrical energy of a nerve impulse
How do the receptors in the eye work?
Contain a specific pigment
Pigment broken down by specific wavelength of light
High/low light intensity
IF broken down message will be sent
Where are rod cells most numerous?
Side of the eye
Where are cone cells must numerous?
Fovea
What pigment is present in rod cells?
Rhodopsin
What pigment is present in cone cells?
3 different idopsin = green, red + blue light
What colour image does rod cells produce?
Black and white
What colour image does cone cells produce?
Coloured
What light intensity is rod cells’ pigment broken down in?
Low
What light intensity is cone cells’ pigment broken down in?
High
What is the visual acuity of rod cells?
Low
What is the visual acuity of cone cells?
High
How many neural connections do rod cells have?
Multiple
How many neural connections do cone cells have?
One = own bipolar cell
Pigment inside rod cells should be broken down but what else?
Threshold value must be exceeded
Ensures generator potential reached
What are disadvantages of rod cells?
Only generates one impulse regardless of multiple
Cannot distinguish between different sources of light
Low visual acuity
What are the two nodes that control the heart?
Sinoatrial (SAN)
Atrioventricular (AV)
What do the two nodes together do?
Iniate the cardiac cycle
Describe what happens in the cardiac cycle
Electrical impulse spreads across atria from SAN = atria contracts
Atrioventricular septum (non-conductive tissue) stops impulse from travelling to the ventricles
Electrical activity travels to AVN
After a pause the AVN sends an impulse down the bundle of His
The bundle of His conducts the impulse through AV septum to bottom of ventricle
Punkinje fibres (smaller fibres) continue throughout ventricle wall
Ventricle contracts from base up
What node is considered the natural pacemaker and why?
SAN because it iniated contraction of atria
What is importance of the Punkinje fibres>?
Smaller branching network which sends nerve impulses to cells in the ventricles of heart
Where is the electrical impulse sent once it reaches the AV node?
Bundle of His
Where does the ventricle contract from and why is this important?
Apex (base) = more muscle in the ventricle walls to increase the pressure + push blood further
Why is there a short delay before the electrical wave leaves the AVN?
Makes sure the atria has emptied before the ventricles contract
What is the autonomic system?
All internal systems in the body needed to be controlled + regulated
What is the peripheral nervous system?
Pairs of nerves from the CNS travelling to limbs + organs
Is autonomic voluntary or involuntary?
Involuntary
Is somatic voluntary or involuntary?
Voluntary
What is the sympathetic N.S primary process?
To stimulate body’s fight mode
When does the sympathetic N.S stimulate effectors?
During strenuous activities
Powerful emotions
When does the sympathetic N.S increase in activity?
Times of stress, illness or injury
Why is the sympathetic N.S constantly active at basic levels?
To maintain homeostasis
Because the sympathetic N.S stimulates what does it do?
Speeds up activities
What does sympathetic N.S do for the body?
Heighten awareness’
Prepare for action
Help cope with stressful situations
Because the parasympathetic inhibits effectors what does it do?
Slows activity
When does the parasympathetic N.S control activities?
Under normal resting conditions
What does the parasympathetic N.S deal with?
Conserving energy + replenishing the body’s resting reserves
When is the parasympathetic N.S active?
State of relaxation
= Sleep/recovery from illness or injury
What is the parasympathetic N.S primary process?
To enable the body to “Rest and Digest”
What is the medulla?
A cone-shaped neurone mass
What is the medulla responsible for?
Involuntary functions
What does the medulla control?
Breathing
Heart rate
Blood pressure
What centres does the medulla contain?
Cardiac
Respiratory
Vomiting
What are the two type of receptors when controlling heart rate?
Chemoreceptors
Pressure receptors
What does chemoreceptors detect?
pH changes in the blood
Where are the chemoreceptors found?
Carotid arteries
What does pressure receptors detect?
Pressure changes in the blood
Where are pressure receptors found?
Carotid arteries
Aorta
The centre, in the brain, that increases HR is linked to what?
SAN by sympathetic N.S
The centre, in the brain, that decreases HR is linked to what?
SAN by parasympathetic N.S
What happens when blood pressure is high?
Pressure receptors
Nervous impulse sent to centre of medulla (decreases HR)
Centre sends impulse via parasympathetic N.S to SAN
Decreases HR
What happens when blood pressure is low?
Pressure receptors
Nervous impulse sent to centre of medulla (increases HR)
Centre receives impulse via sympathetic N.S to SAN
Increases HR
How do chemoreceptors work?
Increased metabolic activity More CO2 = pH decreases Chemoreceptors increase impulses to centre of medulla that increase HR Via sympathetic NS to SAN HR increases = blood flow increases More CO2 removed pH rises to normal
What is a feedback loop?
The automatic control system resulting in a return to normal conditions
`What is the feedback loop of chemoreceptors?
Change in blood pH = stimuli (Chemo)receptors in carotid arteries Coordinate centre co-ordinates a response (medulla) Effector brings about response (heart) Response returns HR back to normal
What effect does IAA have on growth of roots?
Inhibits growth
Why does vision using the fovea has a high visual acuity
Lots of cones cells present
Each cone cell has its own neurone
How does a high conc of IAA at the bottom of the root cause it to bend?
High conc at bottom so cell only grow at the top, causing it to bend downwards
What is the term used to describe the sharing of one neurone by multiple rod cells?
Retinol convergence
By which process do plant hormones move from growing regions of a plant to other tissues?
Diffusion
How is action potential generated in the Pacinian Corpuscle?
Applies pressure which deforms tissues
This widens stretch mediated Na channels
Causes influx of Na+ into membrane
Changes the potential
What is the role of the bundle of His
To conduct electrical message from the AV node to the apex of the heart down the non-conductive septum
What is the role of the medulla oblongta
Involuntary responses
