Receptors Flashcards
Effect of iodopsin being more stable than rhodopsin
Greater light intensity to break it down and release neurotransmitter
Resting heart rate in typical adult
70 beats per minute
What is acuity
Ability to see something clearly
What neurotransmitter does opsin release
Glutamate
Excitatory NET
Function of the non conducting connective tissue layer between the atria and the ventricles
Prevents electrical impulses from SAN passing into the ventricles
Prevents electrical impulses from the AVN passing into the atria
Importance of the delay at the AVN
Allows the artia to empty
And ventricles to be filled
Before ventricles contract
Benefit of purkinje fibres running to base of ventricles
Ventricular contraction can start at the base
And push blood up into arteries
Functions of autonomic nervous system
Heart rate
Blood pressure
Respiration
Digestion
How do chemoreceptors detect changes in pH
Changes in CO2 levels due to changes in respiration CO2 forms a weak acid in solution Decreasing the pH More CO2 means lower pH (more acidic) Chemoreceptors detect low pH
What is a receptor
Specialised cell
That detects a stimulus
Converting one form of energy into a generator potential (electrical)
Which may cause an action potential in the sensory neurone
What is the pacinian corpuscle
A pressure receptor
That responds to mechanical stimuli
Found deep in the skin (fingers, external genitalia, feet soles)
And in joints, tendons and ligaments
Where are pacinian corpuscles found
Deep under the skin
Of feet, external genitalia, soles of feet
And in joints, tendons and ligaments
Structure of the pacinian corpuscle
Many layers of connective tissue with a viscous gel between (lamellae)
Which surround the ending of a single sensory neurone
Sensory neurone ending has stretch mediated sodium ion channels
And a myelinated axon
How does the pacinian corpuscle work
Stimulus of pressure deforms viscous gel layers
Exposed axons stretch mediated sodium ion channel proteins open
Sodium ions diffuse in down a concentration gradient
More positive ions on inside of membrane
Causing depolarisation
Leading to an electrical potential difference called a generator potential
If generator potential reaches or exceed threshold value an action potential is generated and a nerve impulse propagated along the sensory neurone
How does an increased pressure affect the pacinian corpuscle
More stretch mediated sodium ion channel proteins open
So more sodium ions diffuse in
Leading to a larger generator potential
What is the eye
A sense organ
That has 2 types of receptor
That detect and respond to light intensity and wavelengths of light
Located in retina
Structures of the eye
Cornea Iris Pupil Lens Vitreous gel Retina Macular Fovea Optical nerve
The macular in the retina contains the fovea
Features of rods
Evenly distributed throughout the macula
Low density in fovea
Sensitive to all wavelengths of light
Rhodopsin is the light sensitive pigment
High visual sensitivity to low light intensity
Low visual acuity so unclear image
Retinal convergence due to several rods sharing a single bipolar neurone and generator potentials combine to reach threshold
Where are rods found
Evenly distributed through the macula
Low density in fovea
Features of cones
Densely packed in the fovea
Small area in the macula
Each cone detects a specific wavelength of light
3 types of iodipsin (RGB)
Low visual acuity to low levels of light intensity (iodopsin is more stable so requires a higher light intensity of specific photons per second)
High visual acuity gives a sharp image because each cine synapses with a single bipolar neurone
So send a separate impulse to brain
Why aren’t bipolar neurone myelinated
They are very short (micrometers) in length
So pointless
Myelination more efficient for long neurones
Explain retinal convergence
Many rods synapse with one bipolar neurone
Stimulation of several rods results in enough neurotransmitter released to reach threshold value in bipolar neurone
Leading to spatial summation
How does light lead to a generator potential in rods
Photons of light cause rhodopsin to break down
Into opsin
Altering its chemical structure
Causing it to act like an enzyme
And release the neurotransmitter glutamate
Generator potential reaches threshold value
Action potential produced in bipolar neurone
Opsin used to resynthesise rhodopsin
How does light lead to a generator potential in cones
Photons of light cause iodopsin to break down
Altering its chemical structure
Causing it to act like an enzyme
And release neurotransmitter
Generator potential reaches threshold value
Action potential produced in bipolar neurone
Used to resynthesise iodopsin
3 different types of iodospin (RGB)
Explain how the active site of an enzyme causes a high rate of reaction
Lowers activation energy
Induced fit cause active site of enzyme to change shape slightly so more complementary
Enzyme-substrate complex causes bonds to form/break
Why is the visual cortex so large
Lots of complex information to process
What is a blind spot
Part of a visual field you can’t see
Due to an absence of cones and rods/receptors in the area being stimulated by the light
Why do rods cause low visual acuity
Several rods are connected to one bipolar neurone
So light falling on several rods only generate one impulse to the brain
The brain can’t distinguish between separate light sources that generate the impulses
Why do cones cause high visual acuity
Each cone synapses with an individual bipolar neurone
They are so densely packed, meaning photons of light are likely to fall on 2 separate cone cells
Generating 2 electrical impulses to the brain
So it can distinguish between the light sources that generate them
So the brain interprets this as 2 separate points of light
What is the SAN
Sino-Atrial Node
A region of specialised muscle fibres
Located in the right atrium wall of the heart
That generates impulses and waves of depolarisation
Which pass across the atria
So the atrial muscles contract
Importance of being able to alter heart rate
In response to the needs of the body
E.g during exercise or avoiding predation the heart rate must increase to supply more oxygen to muscles for more aerobic respiration to produce the ATP needed for muscle contractions and movement
Explain the resting heart rate
Sino-Atrial node generates an impulse
So waves of depolarisation pass over the atria
Atria contract (systole)
Layer of connective, non conducting tissue between the atria and ventricles prevents electrical impulse reaching ventricles
Delaying the impulse at the Atrio-Ventricular node
So they atria can empty and ventricles can fill with blood before contracting
Waves of depolarisation from the Atrio-Ventricular node pass down the purkinje fibres in the Bundle of His
Causing the ventricles to contract from the apex upwards
What is the ANS
Autonomic Nervous System
A branch of the Peripheral Nervous System
With two of its own branches
Called the parasympathetic and sympathetic nervous system
What is the sympathetic nervous system
Branch of the autonomic nervous system That stimulates effectors Speeds up heart rate Involved in fight or flight And uses the neurotransmitter noradrenaline
What is the parasympathetic nervous system
Branch of the autonomic system Inhibits effectors Controls activity at rest (&digest) Slows down the heart rate Uses neurotransmitter acetylcholine
What controls heart rate changes
The medulla oblongata in the brain stem
And it’s cardio regulatory centre
Structure of the cardio regulatory centre
2 parts
Acceleratory centre
Inhibitory centre
What is the acceleratory centre
Found in the cardio regulatory centre in the medulla oblongata
Links to the SAN node
By the sympathetic nerve
Of the sympathetic nervous system
What is the inhibitory centre
Part of the cardio regulatory centre on the medulla oblongata
That links to the SAN by the parasympathetic nerve
Of the parasympathetic nervous system
What are chemoreceptors
Receptors found in the aorta and carotid arteries
Important in the control of the heart rate
That respond to changes in pH
What are baroreceptors
Receptors found in the aorta and carotid arteries
Important in controlling the heart rate
That respond to changes in blood pressure
Increase in blood pressure
Detected by baroreceptors in the walls of the aorta and carotid arteries
More frequent impulses sent to the medulla oblongata
More frequent impulses from the inhibitory centre in the medulla to the Sino-Atrial node
Via the parasympathetic nerve
Decreased frequency of impulses from SAN across atria by acetylcholine
Heart rate decreases
So blood pressure decreases
Decrease in blood pressure
Detected by baroreceptors in the walls of the aorta and carotid arteries
Less frequent impulses sent to the medulla oblongata
More frequent impulses from the acceleratory centre in the medulla to the Sino-Atrial node
Via the sympathetic nerve
Increased frequency of impulses from the SAN across the atria
By noradrenaline
Heart rate increases
So blood pressure increases
How do chemoreceptors work
Carbon dioxide levels rise (e.g from exercise and increased respiration)
So blood pH decreases below normal level
Detected by chemoreceptors in the walls of the aorta and carotid artery
More frequent impulses sent to the medulla oblongata
More frequent impulses sent from the acceleratory centre in the medulla to the Sino-Atrial node
Via the sympathetic nerve
More frequent impulses sent from the SAN across the atria
Via noradrenaline
Heart rate increases
To supply more oxygen to respiration cells to produce the ATP needed for muscle contractions in exercise
Parasympathetic vs sympathetic nervous system
P: Inhibits effectors/S: Stimulates effectors
P: Inhibitory centre to SAN via parasympathetic nerve/S: Acceleratory centre to SAN via sympathetic nerve
P: Acetylcholine/S: Noradrenaline
How does dopamine stimulate the production of nerve impulses in the post synaptic neurone
Similar structure to acetylecholine Diffuses across the synapse Attaching to receptors on post synaptic membrane Opening sodium ion channel proteins Sodium ions can diffuse in Allowing for depolarisation And an action potential to be produced
How does morphine provide pain relief
Similar shape to endorphins
So attatch to opioid receptors
More dopamine released to provide pain reliefe
Advantage of the movement of mitochondria/ATP to the pre synaptic membrane
Mitochondria supply additional ATP
To move vesicles/for active transport of ions
To resynthesise and reabsorbed acetylcholine
How can damaged myelin sheath cause a slower response to stimuli
Less/no saltatory conduction
More depolarisation over length of membranes
Why does it take time for rods to recover sensitivity to light after moving into darkness
Rhodopsin is broken down by light
Required time for the resynthesis of rhodopsin
What causes vision in colour
3 different types of cone cells sensitive to different wavelengths of light
What causes vision to have high visual acuity
Each cone receptor connects to a separate neurone
Impulse sent along separate neurone from each bipolar neurone
How can a high rod density allow night vision
High visual sensitivity to the lower light intensities
Several rods connect to a single bipolar neurone
Spatial summation means enough neurotransmitter to overcome threshold
What is the AVN
Atrio-Ventricular Node
A region of specialised muscle fibres
In the atria above the non conducting connective tissue layer
That sends electrical impulses that travel down Purkinje Fibres in the Bundle of His when stimulated by electrical impulses from the Sino-Atrial Node
With a 0.1s delay
