Stimuli and Response Flashcards
Name three receptors
Rod cells
Cone cells
Pacinian Corpuscle
Outline what happens during a simple reflex arc
S > R > SN > RN > MN > R > E
Advantage of a simple reflex
Rapid response to stimuli and instinctive
Common features of a sensory receptor
Acts as energy transducer which establishes a generator potential and responds to a specific stimuli
Describe the basic structure of a Pacinian corpuscle
Single nerve fiber is surrounded by layers of connective tissue which are separated by viscous gel and contained by a capsule. There are stretch-mediated Na+ channels on the plasma membrane and capillary runs along the base layer of tissue.
What stimulus does a PC respond to and what happens
- Pressure deforms the membrane causing the stretch-mediated Na+ channels to open
- If an influx of Na+ raises the membrane to threshold potential, a generator potential is produced.
- Action potential moves along sensory neuron
Where are rod and cone cells located
Rod = Periphery
Cone = Central Fovea
Pigment of rod and cone cells
Rod = Rhodopsin
Cone = 3 types of Iodopsin
Visual acuity of rod and cone cells
Rod = Low resolution as many rod cells to one bipolar neuron
Cone = High resolution as only one cone cell to one bipolar neuron
Colour sensitivity of rod and cone cells
Rod = monochromatic
Cone = Tricolour ( red , blue + green)
Light sensitivity of rod and cone cells
Rod = Very sensitive due to spatial summation of subthreshold impulses
Cone = Less sensitive not involved in night vision
Pathway of light from a photoreceptor to the brain
photoreceptor -> bipolar neuron -> ganglion cell of optic nerve -> brain
what is the autonomic nervous system
The system that controls involuntary actions of glands and muscles. Parasympathetic and sympathetic
Difference between sympathetic and parasympathetic nervous system
Sympathetic = involved in flight or fight response, stimulates effectors to speed up activity
Parasympathetic = Inhibits effectors to slow down activity
Receptor involved in changing heart rate and their function and location
Baroreceptors = change in blood pressure and is found in the carotid body
Chemoreceptors = change in pH , due to increase in CO2 conc. and is found in the carotid and aortic body
How does the body respond to an increase in blood pressure
- Baroreceptors send more impulses to cardioinhibitory centre in the medulla oblongata
- More impulses to SAN down vagus nerve via parasympathetic nervous system
- This stimulate the release of acetylcholine which decrease heart rate
How does the body respond to a decrease in blood pressure
- Baroreceptors send more impulses to the cardioacceleratory centre in the medulla oblongata
- More impulses to SAN via the sympathetic nervous system
- This stimulates release of noradrenaline which increase HR and strength of contraction
How does the body respond to an increase in CO2 conc.
- Chemoreceptors detect pH decrease and send more impulse to cardioacceleratiry centre of medulla oblongata
- More impulse to SAN via the sympathetic nevrous system
- HR increase , so rate of blood flow to lungs increase and so rate of gas exchange and ventilation rate increases.
Formula for cardiac output
SV x HR
Describe how heartbeats are initiated
- SAN initiates a wave of depolarisation
- WOD spreads across both atria (atrial systole)
- Layer of fibrous, non-conducting tissue delays while ventricles fill and valves close
- AVN conveys WOD down septum via Bundle of HIs which branches into Purkinje fibres along ventricles
- This cause ventricles to contract from apex upwards
2 nodes involved in heart contraction + location
Sinoatrial node = right atrium
Atrioventricular node = lower end of right atrium
Define taxis
Directional movement in response to an external stimulus
Define kinesis
Undirectional response to presence and intensity of external stimulus
What are plant growth factors and where are they produced
Chemicals that regulate plant growth repsonse to directional stimuli and are produced in plant growing regions and diffuse from cell to cell via phloem mass transport
Why do shoots show postive phototropism
- IAA diffuse to shade side of the shoot tip
- As IAA diffuses down shaded down side , cells on shaded side elongate faster and shoot bends towards light
Why do roots show positive gravitropism
- Gravity causes IAA to accumulate on lower side of the root.
- IAA inhibits elongation of root cells, cells on upper side of the root elongate faster so root tip bends downwards
