13.12 Receptors and Control of Heart Rate Flashcards
Receptor
- Specialised cells which detect a specific stimulus
- Convert one form of energy into a generator protein
What is the Pacinian corpuscle?
- Pressure receptor
- Found mainly deep in the skin
- Also located in joints, tendons and ligaments
- Made up of many layers called lamellae which surround the ending of a single sensory neuron
How does the Pacinian corpuscle work?
- Increased pressure deforms sodium channels
- Changes the stretched mediated Na+ channels
- Na+ channel proteins open and Na+ diffuse in
- Depolarisation leads to a generator potential
Greater pressure in Pacinian corpuscle?
More stretch mediated Na+ ion channel proteins open, LARGER generator potential
Types of eye receptors
Cones
Rods
Rods
- Evenly distributed throughout the macula
- Sensitive to all wavelengths of light
- High visual sensitivity to low levels of light intensity
- Low visual acuity so image is unclear
- Retinal convergence due to several rods sharing a single Bipolar neuron
Cones
- Densely packed in the fovea
- Each cone detects a specific wavelength of light
- Iodopsin is less sensitive than rhodopsin so requires higher light intensity of photons
- High visual acuity giving sharp image
- This is because each cone cell connected with a single bipolar neuron
- Cones send separate impulses to brain
How many rods link to one neurone
3
How many cones link to one neurone
1
Pigment in rod
Rhodopsin
Pigment in cone
Iodopsin
How is generator potential created in eyes?
Photons cause pigment to break down
Altering the chemical structure
Leads to a production of generator potential
How many types of rod cells
1
How many types of cone cells
3 responding to diff wavelengths of light
What type of summation do rods use
Retinal convergence (leads to spatial summation)
What type of summation do cones use
Temporal summation
Myogenic
Heart muscle is myogenic
Initiates its own contraction
Sinoatrial node
Responsible for initial stimulus for the contraction in heart
The heart controls and coordinates the regular contraction of the atria and ventricles.
Describe how.
- Sino atrial node sends wave or electrical activity across both atria
- Both atria contract
- Layer of nonconductive tissue prevents wave reaching ventricles
- Wave of electrical activity reaches the atrio ventricular node
- 0.1 second delay allowing atria to empty fully 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
Heart rate is under the control of
Autonomic nervous system
Medulla oblongata
Two branches of the autonomic nervous system
Sympathetic
Parasympathetic
Sympathetic
Stimulates effectors
Speeds up heart rate
Fight or flight
Noradrenaline
Parasympathetic
Inhibits effectors
Controls activity at rest
Acetylcholine
Two parts of cardio regulatory center
Acceleratory center
Inhibitory center
Acceleratory centre linked to SA node by
Sympathetic nervous system
Inhibitory centre linked to SA node by
Parasympathetic nervous system
Two receptors for controlling heart rate
Baroreceptors
Chemoreceptors
What change does baroreceptor detect?
Changes in blood pressure
What happens to heart rate if blood pressure increases above normal?
- Detected by baroreceptors in walls of aorta & carotid arteries.
- More frequent impulses sent to medulla oblongata.
- More frequent impulses from inhibitory center in medulla to SA node via parasympathetic nerve.
- Decreases frequency of impulses from SA node across atria. (Acetylcholine)
- Heart rate decreases
What happens to heart rate if blood pressure decreases below normal?
- Detected by baroreceptors in walls of aorta & carotid arteries.
- Less frequent impulses sent to medulla oblongata.
- More frequent impulses from acceleratory center in medulla to SA node via sympathetic nerve.
- Increases frequency of impulses from SA node across atria. (Noradrenaline)
- Heart rate decreases
What change does chemoreceptor detect?
Changes in CO2 levels affecting blood pH
What happens if CO2 levels rise, causing blood pH to decrease below normal after exercise?
- Detected by chemoreceptors in walls of aorta & carotid arteries.
- More frequent impulses sent to medulla oblongata.
- More frequent impuises from acceleratory center in medulla to SA node via sympathetic nerve
- more frequent impulses from SA node across atria (Noradrenaline)
- Heart rate increases
There is no opposite effect for low CO2 levels of the blood.
More CO2 present
Lower pH- more acidic
Explain how the fovea increases the detail of an image
- High (visual) acuity
- Each / single cone is connected to a single bipolar/neurone
- Each cone sends separate impulse to the brain
Explain how the connection of several rods to a single bipolar cell (Retinal convergence) influences visual acuity
- (Spatial) Summation means cannot distinguish between stimuli from different rod cells linked to same bipolar cell;
- Decreases acuity;
Explain how the connection of several rods to a single bipolar cell (Retinal convergence) influences sensitivity
- (Summation of) sub-threshold stimuli produces threshold stimulation;
- Increases sensitivity;
People with red-green colour blindness are unable to distinguish between red and green, and also between other colours
Explain why.
- Green sensitive pigment/cones non-functional
OR
Cones that detect green light non-functional; - Three different types of pigment/cone;
- Other/different colours (‘seen’) due to stimulation of more than one cone/pigment;
Explain how pressure on the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode A.
- (Pressure) deforms / opens (sodium) channels;
- Sodium ions enter;
- Causing depolarisation;
- Increased pressure opens more channels / greater sodium entry;
- [Size of generator potential determines frequency of action potentials]
Explain why increased cardiac output is an advantage during exercise.
- Higher cardiac output - Increases O2 supply (to muscles);
- Increases glucose supply (to muscles);
- More ATP produced by oxidative phosphorylation / more energy release / more aerobic respiration / actively respiring muscles
- Increases CO2 removal (from muscles) / lactate removal;
- Increases heat removal (from muscles) / for cooling;
- Delays the formation of lactate
Describe what is meant by the term threshold
- When threshold has been reached;
- (Threshold or above) causes maximal response / all or nothing principle;
