Topic 6A: Stimuli and Response Flashcards
What are the two major systems in the nervous system?
- Central Nervous System (CNS)
- Peripheral Nervous System (PSN)
What is in the CNS?
- Brain
- Spinal Cord
What is in the PSN?
-neurones that connect to the CNS to the rest of the body.
The PNS consists of..
- sensory neurone
- motor neurone
Motor neurone has….
soamatic and autonomic nervous system
What is the soamatic nervous system?
conscious eg running g body muscle
What is the autonomic nervous system?
subconscious
uses glands, smooth muscle, cardiac muscle eg digestion
What are the two types neurones in a autonomic nervous system?
sympathetic-gets the body ready for action
parasympathetic-calms the body down
What is the importance of the reflex arc?
- Protects you from harm
- Saves times so brain can perform more complex responses
- Fast/Rapid
What is a stimulus?
A detectable change in the internal/external environment
What is a receptor?
Detect stimuli
Animals and plants respond to stimuli…
to increase their chances of survival
Receptors can be…
proteins or cells
What is sensory Reception?
Function of receptors
What is the sensory Presception?
Making sense of the information in the receptors
What is the Pacinian Corpuscle?
A type of receptor that is found in skin cells which detect mechanical pressure
What happens when pressure is applied to the pacinian corpuscle (PC)?
- PC receptor is stimulated
- llemelae gets deformed
- the stretched mediated sodium ion channels get deformed
- membrane becomes more permeable to sodium
- causes channel to open
- sodium ion channels diffuse into cell
- Creates a generator potential
Where is the stretch mediated sodium ion channels located?
in the sensory nerve ending
What is a transducer?
Something that turns stimulus energy into electrical impulses.
Why is rod cells and cones cells types of transducers?
Because it converts light energy into electrical impulses so it can travel around the body
What is iris in the eye?
They are muscles that control the amount of light entered
What does the lense do in the eye?
It focuses the light rays on the retina
What does retina contain?
Light receptors
What happens when light hits the photoreceptors?
- light is absorbed by the light sensitive optical pigments
- causes chemical change in the permeability of Na ions and operator potential
- nerve impulses sent along the bipolar neurone
What is a bipolar neurone?
Neurone that connects the optical nerve and photoreceptors
Name the two types of receptors
Rod and cone cells
Features of Rod Cells
- Found in the retina
- black + white
- one type of cell
- Low light intensity (dim light-very sensitive)
- Low visual acuity
Features of Cone Cells
- Found in the fovea
- Colour
- 3 types of cells:red,blue,green
- High light intensity (bright light)
- High visual acuity
Why does the rod cells have low visual acuity?
Because:
- several rod cells connect to one neurone
- retinal convergence
- sensory preception is hard
Why does the cone cells have a high visual acuity?
Because:
- one cone cell is connected to one neurone
- each individual cone cell so receives more information to the brain
- no retinal convergence
What does the ‘cardiac muscle is myogenic’ mean
it can contract and relax without receiving signals from nerves.This pattern of contraction controls the regular heartbeat.
What does SAN stand for?
sinoatrial node
What does AVN stand for?
atrioventricular node
Where is the SAN located?
walls of the right atrium
Outline how the cardiac muscle regulate a regular heartbeat?
- SAN sets the rhythm of the heartbeat/pacemaker
- by initiating regular waves if electrical activity to atrial walls
- causes right and left atria to contract at the same time
- electrical impulses move to the AVN
- the electrical impulses dont go straight to the ventricles due to non conducting collagen tissue in the ventricles
- After delay AVN sends electrical impulses to the bundle of His
- then to Purkyne tissues
- allows right and left ventricles to contract simultaneously from bottom up
What is bundle of His?
-group of muscle fibres that are responsible for electrical activity between the ventricles and bottom of the heart (apex)
What is Purkyne tissue?
Finer muscle fibres
What receptors that affect the heart rate?
Baroreceptors (pressure receptors)
Chemoreceptors (chemical receptors)
Where are baroreceptors found?
- aorta
- carotid arteries
Where are chemoreceptors found?
- aorta
- carotid arteries
- medulla
If blood pressure is HIGH…
- barorecptors detect the high blood pressure
- impulses sent to medulla
- then to parasympathetic neurone
- parasympathetic neurone secretes acetylcholine
- binds to receptors on the SAN
- heart rate slows
- reduces blood pressure back to normal
If blood pressure is LOW…
- barorecptors detect the low blood pressure
- impulses sent to medulla
- then to sympathetic neurone
- pympathetic neurone secretes noradrenaline
- binds to receptors on the SAN
- heart rate speeds up
- increases blood pressure back to normal
If Oxygen is high, pH levels high, low CO2
- chemorecptors detect the chemical changes in blood
- impulses sent to medulla
- then to parasympathetic neurone
- parasympathetic neurone secretes acetylcholine
- binds to receptors on the SAN
- heart rate decreases
- returns O2, CO2 and pH levels back to normal
If Oxygen is low, pH levels low, high CO2
- chemorecptors detect the changes in the blood
- impulses sent to medulla
- then to sympathetic neurone
- pympathetic neurone secretes noradrenaline
- binds to receptors on the SAN
- heart rate increases
- returns O2, CO2 and pH levels back to normal l
The SAN generates electrical impulses causes….
cardiac muscles to contract
The rate at which the SAN fires is unconsciously controlled by what part of the brain?
The medulla oblongata
Name three stimuli plants respond to?
light
gravity
water
What is tropism?
the response of a plant to a directional stimulus
What is directional stimulus?
a stimulus coming from a particular direction
Movement of a whole organism towards light (e.g. algae) is called…
Phototaxis (positive)
Define taxis.
A directional response in which a whole organism moves towards or away from a stimulus.
Define kinesis.
Random movement of a whole organism in response to a non-directional stimuli e.g. temp or humidity. This may be an increase/decrease in speed or turning frequency.
Name the main plant growth factor…
Indoleacetic Acid (IAA)
Describe the process of positive phototropism in a flowering plant shoot.
- Cells in the shoot tip produce IAA.
- IAA is usually evenly transported down the shoot,
- Light causes the movement of IAA to the shaded side of the shoot.
- There is more IAA on the shaded side vs light side.
- IAA causes shaded side shoot cells to elongate!!
- Unequal growth causes the shoot to bend towards light.
Describe the process of negative phototropism in a flowering plant root.
- Cells in the root tip produce IAA.
- IAA is usually evenly transported down the root,
- Light causes the movement of IAA to the shaded side of the root.
- There is more IAA on the shaded side vs light side.
- IAA inhibits cell elongation in roots!!
- Unequal growth causes the root to bend away from light (into the ground).
Tactic response is….
directional eg light
Kinetic response is…..
non directional ef humidity
