Receptors And Control Of Heart Rate- Paper 2

Question 1

What are receptors

Answer 1

Specialised cells which detect a specific stimulus and convert one form of energy into a generator potential, the generator potential then causes an action potential in the sensory neurone

Question 2

What is the Pacinian Corpuscle an example of

Answer 2

A pressure receptor as it responds to a mechanical stimuli and is find deep within the skin - also located within the joints, tendons and ligaments

Question 3

What are Pacinian corpuscles made up of

Answer 3

Many layers of lamellae which surround the ending of a single sensory neurone
Lamellae are made up of connective tissue

Question 4

Describe how the Pacinian corpuscle works

Answer 4

Pressure on the skin deforms the stretch mediated Na+ channel proteins embedded within the membrane axon membrane
Sodium ion channels proteins open and sodium ions diffuse in
Depolarisation leading to generator potential

Question 5

What is the generator potential

Answer 5

The depolarisation or electrical potential difference

Question 6

What happens if a generator potential reaches the threshold value

Answer 6

Action potential is created and never impulse is propagated along the sensory neuron
The frequency of action potentials relates to the intensity of the stimulus
The maximum frequency of action potentials is limited by the refractory period

Question 7

Describe the rod cell and its adaptations to wave lengths (4 points)

Answer 7

They are evenly distributed throughout the macula
Sensitive to all wavelengths of light (rhodopsin is the sensitive pigment)
High visual sensitivity to low levels of light intensity
Low visual acuity, meaning the image is unresolved- retinal convergence due to several rods sharing a single bipolar neuron, generator potentials combine to reach threshold

Question 8

Describe cones and their adaptation to light (4 points)

Answer 8

Densely packed in they fovea
Each cone detected a specific wavelength of light which is Red green or blue. There are three types of iodopsin, each cone cell is sensitive to a specific narrow range of wavelength
Iodopsin is less sensitive as more stable than rhodopsin so requires higher light intensity of specific photons per second
High visual activity giving a sharp image
This is because each cone cell synapses connected with a single bipolar neuron
Cones send separate sets of impulses to the brain

Question 9

Describe the role of pigment and rhodopsin and iodopsin

Answer 9

They break the pigment down, altering the chemical structure and this leads to the production of a generator potential

Question 10

Explain which each rod or cone cell is joined to

Answer 10

Every cone cell has a synapse with a single bipolar neurone
Multiple rods synapse with one bipolar neurone

Question 11

Give detailed description of the different features of rod cells

Answer 11

Low visual acuity- as several rods are connected to one bipolar neuron, this means that the light falls on several rod cells and will only generate one impulse to the brain- brain can’t distinguish between the separate light sources that generated them

Rods are highly sensitive to low light, the stimulation of several rods results in enough NETS released to reach threshold value in the bipolar neuron in low light intensities

Retinal convergence leads to spatial summation

Generator potentials combine to reach threshold

Question 12

Describe the adaptations and functions of cones

Answer 12

Provide high visual acuity- each cone synapses with an individual bipolar neurone

This means that light falling on 2 cone cells generates two electrical impulses to the brain and the brain can distinguish between the light sources that generated them- brain interprets it as two separate points of light

Each cone must release enough neurotransmitter to reach threshold in the bipolar neurone and this can only happen in bright light- this is temporal summation

In low light intensities there is not enough neurotransmitter to create an action potential in the bipolar neurone so cones only operate when light intensity is high

Question 13

explain the process of controlling the heart rate

Answer 13

• SAN–> AVN—> Bundle of His—> Purkinje fibresSino atrial node sends wave or electrical activity across both atria
• 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 fibers
• causing the ventricles to contract from the apex of the heart upwards

Question 14

describe the sympathetic nervous system

Answer 14

• stimulates effectors
• speeds up
• fight or flight
• neurotransmitter is noradrenaline
  can dilute pupils, speed up the heart beat, dilate airways etc

Question 15

describe the parasympathetic nervous system

Answer 15

-inhibits effectors
-controls activity at rest
- neurotransmitter is acetylcholine

Question 16

what is the relationship between the two branches of the autonomic nervous system

Answer 16

sympathetic and parasympathetic are antagonistic

Question 17

what is the heart muscle and describe the role of the sinoatrial node

Answer 17

myogenic- it can initiate its own contraction
SAN–> responsible for the initial stimulus for the contraction

Question 18

what is heart rate controlled by

Answer 18

medulla oblongata in the brain and it has a cardio regulatory center

Question 19

hat are the two parts of the cardio regulatory center

Answer 19

acceleratory center- linked to the SA node by the sympathetic nervous system

inhibitory center- linked to SA node by the parasympathetic nervous system

Question 20

where are receptors found that regulate heart rate

Answer 20

aorta and carotid arteries

Question 21

explain how the baro receptors respond do a high blood pressure that has increased above normal

Answer 21

• increase in blood pressure is detected by baroreceptors in walls of aorta and 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 SÁ node across atria (acetylcholine)
• Heart rate decreases

Question 22

explain how baro receptors respond to a detection of low blood pressure

Answer 22

• decreased blood pressure detected by baroreceptors in walls of carotid arteries
  -less frequent impulses sent to medulla oblongata
• more frequent impulses from acceleratory center in medulla sent to sympathetic nerve
• increases frequency of impulses from SA node across atria
• Heart rate increases

Question 23

describe what chemoreceptors are and their response to CO2 levels increasing

Answer 23

Co2 forms a weak acid in solution and will decrease the pH

if Co2 levels fall below normal:
- detected by chemoreceptors in walls of aorta and carotid arteries
- more frequent impulses sent to medulla oblongata
- more frequent impulses from acceleratory center in medulla to SA node via sympathetic nerve
- more frequent impulses from SA node across atria (noradrenaline)
- heart rate increases