Receptors Flashcards
What is a receptor? (2)
Specialised cells which detect a specific stimulus and convert one form of energy into a generator potential
Where is a Pacinian corpuscle found? (2)
Deep in the skin e.g. fingers, soles of the feet and the external genitalia
Joints, tendons, and ligaments
Describe the structure of a Pacinian corpuscle (2)
Made up of many layers called lamellae,
which are each separated by a gel, which surround the ending of a single sensory neuron
contains stretch-mediated sodium ion channels in the cell surface membrane
Describe how a Pacinian corpuscle produces a generator potential when stimulated (5)
Increased pressure on the skin deforms the stretch mediated Na+ channel proteins
Deformation causes stretch mediated Na+ channel proteins to open
Na+ diffuse in down a concentration gradient by facilitated diffusion
More positive ions on the inside of the membrane leading to depolarisation
The depolarisation is called the generator potential
What are the two types of photo-receptor cells in the retina? (2)
Rods
Cones
Describe the properties of rods (5)
Evenly distributed throughout the macula
Sensitive to all wavelength of light
High visual sensitivity to low levels of light intensity
Low visual acuity
Retinal convergence due to several rods sharing a single bipolar neuron
Describe the properties of cones (5)
Densely packed in the fovea
Each cone detects a specific wavelength of light (R,G,B) and is sensitive to a specific wavelength
Less sensitive so required high levels of light intensity of photons
High visual acuity
Each cone cell synapses with a single bipolar neuron
What are the pigments in rods and cones? (2)
Rods - rhodopsin
Cones - iodopsin
How do photons cause a generator potential in rods and cones? (2)
Cause the pigment to break down, altering the chemical structure which leads to the production of a generator potential
Why do rods have low visual acuity? (3)
Several rod cells connected to one bipolar neuron
Light which falls on several rod cells will only generate one impulse to the brain
Brain cannot distinguish between separate light sources that generated them
Why do cones have high visual acuity? (3)
Each cone synapses with an individual bipolar neuron
Light falling on two cone cells generate two electrical impulses to the brain
Brain can distinguish between the light sources that generated them
Brain interprets them as two separate points
Why is the heart muscle known as myogenic? (1)
Can initiate its own contraction without any nervous stimulation
The heart controls and coordinates the regular contraction of the atria and ventricles
Describe how (9)
Sino atrial node sends waves/electrical activity across both atria
Both atria contract
Layer of nonconductive tissue prevents wave reaching ventricles
Wave of electrical activity reaches atrioventricular node
0.1 second delay allowing atria to empty full of blood
Wave of electrical activity sent from the atrioventricular node
Down the bundle of His to the base of the ventricles
Up the Purkinje fibres
Causing the ventricles to contract from the apex of the heart upwards
What controls the heart rate? (1)
In the autonomic nervous system the medulla oblongata controls heart rate
Describe briefly how the sympathetic branch of the ANS works (4)
Stimulates effectors
Speeds up
Fight or flight
Neurotransmitter is noradrenaline
