Response To Stimuli Flashcards
What is kinesis
A change in activity
What is taxes
A automatic response to stimuli - orientated movement towards or away from an environment
What is tropism
Only part of the organism moves towards or away from stimulus
Describe the reflex arc
Stimulus Receptor Sensory neurone Relay neurone Motor neurone Effector Response
Why are reflex arcs important
Makes survival more likely as quick and involuntary so don’t require timely decision making
Also have from birth so don’t need to learn
What is the role of the voluntary nervous system
Carries nerve implies to body muscles and it is conscious of control. Involves skeletal muscle
What is the role of the autonomic nervous system
Subconsciously carries nerve impulses to glands, smooth muscle and cardiac muscle
What does the sympathetic nervous system do
Stimulates effectors so speeds up activity
What does the parasympathetic nervous system do
Inhibits effectors so slows down activity
Why are they sympathetic and parasympathetic nervous systems described as antagonistic
They normally oppose each other
What area in the brain controls changes in heart rate
Medulla oblongata
Where are chemoreceptors found
In walls of carotid arteries
Where are pressure receptors found
In walls of carotid arteries and aorta
Describe what happens to the heart of blood pressure is higher than normal
Baro (Pressure) receptors Transmit nervous impulse To medulla oblongata Impulse sent via parasympathetic branch To sinoatrial node Causes decrease in heart rate
Describe what happens to the heart if blood pressure is lower than normal
Baro (pressure) receptors Transmit nervous impulse To medulla oblongata Impulse sent via sympathetic branch To sinoatrial node Causes increase in heart rate
Describe what happens to heart rate if PH is lowered from high co2 concentration in blood
Chemoreceptors detect PH is lower
Increase frequency of nervous impulses to medulla oblongata which increases heart rate
Blood flow increased so more co2 removed by lungs
PH rises to normal
Frequency impulses reduced
Heart rate reduced to normal
Give an example of a sensory receptor
Pacinian corpuscle
Senses pressure
What is a generator potential
The first impulse
All impulses after this are called action potential
What would happen if someone applied pressure to a pressure sensory receptor
The receptor’s shape will squash
Mechanical energy converted to electrical energy
As nerve impulse (generator potential)
Describe how a pacinian corpuscle produces a generated potential when stimulated
Increase pressure changes stretch-mediated sodium channel
Sodium ions flood in
Depolarisation leading to generator potential
What is the word to describe the neurone in nerve impulse at rest
Polarised
What is the ratio of the sodium-potassium pump
3 sodium out
2 potassium in
What happens to the channels when it’s at rest
Sodium channels closed so they’re stuck outside
Potassium channels open so they can move outside
Describe what happens during depolarisation
Sodium channels open Sodium rushes in Charge across membrane reversed Action potential generated Sodium channels close Potassium channels open Potassium moves out Briefly hyperpolarised
Why does hyperpolarisation occurs
Prevents it being excited again as more sodium is required to reach the threshold to create another action potential
Why does the next cell get stimulated after action potential
Positive feedback
Presence of sodium in previous one encourages it
What factors affect the speed of action potential and how
Myelin sheath
(Allows jump from node to node)
Big diameter of axon is faster
(Less leakage of ions so easier to maintain)
Higher temperature is faster
(Pump controlled by enzymes)
How is a myelinated axon faster than one not myelinated
Less ATP used
As
Myelin sheath allows action potential to jump from node to node
Myelin acts as electrical insulator
What is the difference between kinesis and taxes
Taxes is moving in a direction. Kinesis is moving but no direction
What is the refractory period
Period where axon membrane can’t be depolarised so there’s no new action potential initiated
