Receptors

Question 1

Definition of stimulus.

Answer 1

Detectable change in internal / external envrionment that causes a change to the organism.

Question 2

Definition of a receptor.

Answer 2

Cell that detects a stimulus. Receptors are specific to one type of stimulus.

Question 3

Definition of co-ordinator.

Answer 3

Formulates a suitable response to a stimulus.

Question 4

Definition of effector.

Answer 4

Organ that produces a response.

Question 5

Definition of taxis.

Answer 5

A directional response.
Towards the stimulus is known as positive taxis.
Away from the stimulus is known as negtaive taxis.

Question 6

Definition of kinesis.

Answer 6

A non-directional response.
Causes organisms to change the speed of their movement.
In favourable conditions, movement is slow with many turns.
In unfavourable conditions, movement is fast with few turns.

Question 7

Definition of tropism.

Answer 7

The growth of a plant in response to a directional stimulus.
Towards the stimulus is known as positive tropism.
Away from the stimulus is known as negative tropsim.

Question 8

Describe phototropism (5 points).

Answer 8

1. Cell at shoot tip produces IAA.
2. IAA diffuses down all regions of shoot.
3. Direction of light affects diffusion of IAA. IAA diffuses away from light.
4. IAA concentration builds up on shaded side of shoot. IAA causes cell elongation.
5. Shaded side of shoot elongated faster than non-shaded side. Shoot tip bends towards light.

Question 9

Describe gravitropism / geotropism(5 points).

Answer 9

1. Cell at root tip produced IAA.
2. IAA diffuses down all regions of root.
3. Gravity causes movement of IAA from upper to lower side of root cells.
4. IAA concentration build up on lower side of root. IAA inhibits cell elongation.
5. Lower side of root elongates slower than upper side of root. Root tip bends downwards deeper into soil.

Question 10

Definition of motor neuron.

Answer 10

A neuron that transmits an action potential from the central nervous system to an effector.

Question 11

Definition of somatic nervous system.

Answer 11

Carries nerve impulses to body muscles which are under conscious control.

Question 12

Definition of central nervous system.

Answer 12

Spinal cord and brain.

Question 13

Definition of sensory neuron.

Answer 13

A neuron that transmits an action potential from a sensory receptor to the central bervous system.

Question 14

Definition of reflex arc.

Answer 14

Pathway of neurons involved in unvoluntary response to sensory stimulus.

Question 15

Definition of peripheral nervous system.

Answer 15

Neurons radiating out from the spinal cord to the rest of the body.

Question 16

Definition of autonomic nervous system.

Answer 16

Carries nerve impulses to glands, smooth or cardiac muscles which are not under conscious control, involuntary. Sympathetic and parasympathetic nervous system form part of this.

Question 17

Definition of sympathetic nervous system.

Answer 17

Increases heart rate by sending more impulses to excite the SAN (sino-atrial nodes).

Question 18

Definition of parasympathetic nervous system.

Answer 18

Descrease heart rate by sending more impulses to inhibit the SAN (sino-atrial nodes).

Question 19

List the 5 features / importance of a reflex arc.

Answer 19

1. Rapid.
2. Protects nody tissues.
3. Doesn’t need to be learnt / involuntary.
4. Helps escape predators / find food sources.
5. Enables homeostasis.

Question 20

*Label a pacinian corpuscle digram.

Answer 20

*Refer to notes.

Question 21

Describe how an action potential is generated across the pacinian corpuscle (7 points).

Answer 21

1. At rest, stretch mediated Na+ channels in the pacinian corpuscle are closed.
2. Pressure applied to corpuscle.
3. Lamella becomes deformed.
4. Membrane around neuron stretches.
5. Causes the stretch-mediated Na+ channels to open.
6. Na+ diffuses into neuron down concentration gradient
7. Produces generator potential. If generator potential is sufficient an action potential passes along the sensory neuron. Greater pressure opens more Na+ channels.

Question 22

What are the two types of receptors in the eye?

Answer 22

1. Rods.
2. Cones.

Question 23

Describe rods.

Answer 23

These detect light intensity and have low visual acuity but a high sensititvity to light. The pigment they have is rhodopsin.

Question 24

Describe cones.

Answer 24

These detect light colour and have a high visual acuity but a low sensitivity to light. The pigment they have is called iodopsin.

Question 25

Definition of visul acuity.

Answer 25

The ability of the brain to distinguish between two separate sources of light.

Question 26

Definition of poor visual acuity.

Answer 26

The brain is not able to distinguish between 2 separate sources of light that are close together so are seen as one source of light.

Question 27

Definition of good visual acuity.

Answer 27

The brain is able to distinguish between 2 separate sources of light that are close together so are seen as two separate sources of light.

Question 28

Definition of retinal convergence.

Answer 28

A number of rod cell sare attached to one bipolar cell so it is more likely an action potential will be created.

Question 29

Definition of bleaching.

Answer 29

When light, all pigment inside the rod and cone cells are converted so cell is no longer sensitive to light, so no action potential can be created. If no light, pigment is reformed, so the rod and cone cells are sesnitive again and an action potential can be created.

Question 30

Where are the rod cells located in the eye?

Answer 30

Retina.

Question 31

Where are the cone cells located in the eye?

Answer 31

Fovea (clustered).

Question 32

Definition of sino-atrial nodes (SAN).

Answer 32

Wall of right atrium produces initial wave of excitation to begin cardiac cycle. Pace-maker of the heart.

Question 33

Definition of atrio-ventricular nodes (AVN).

Answer 33

Detects wave of excitation, delays excitation passes excitation down the septum to the purkyne fibres.

Question 34

Definition of Bundles of His.

Answer 34

Fibres connect to the AVN, located in the septum carry wave of excitation to apex of the heart.

Question 35

Definition of myogenic.

Answer 35

Wave of excitation initiated within muscle cell itself.

Question 36

Describe atrial systole in the electrical control of cardiac cycle (3 points).

Answer 36

1. Sin-atrial node sends wave of excitation across both atria causing muscle to contract. 2. Non-conductive tissue stops excitation passing into ventricles. 3. Wave of excitation picked up by AVN and delays excitation to allow atria to fully empty.

Question 37

Describe ventricular systole in the electrical control of cardiac cycle (2 points).

Answer 37

1. Atrio-ventricular node sends wave down bundle of His and the purkynefibres to the apex of the heart. 2. Wave of excitation is released by both sides of the ventricles to contract.

Question 38

Describe diastole in the electrical control of cardiac cycle (1 point).

Answer 38

1. Wave of excitation dissipates into the chest cavity. Muscle relaxes.

Question 39

Describe atrial systole in the cardiac cycle (4 points).

Answer 39

1. Atria walls contract. 2. Vebtricle walls are relaxed. 3. Atria-ventricular valves are open. 4. Semi-lunar valves are closed. 5. Blood flows from the atria into the ventricles quickly.

Question 40

Describe early ventricular systole in the cardiac cycle (3 points).

Answer 40

1. Atria walls are relaxed, ventricle walls are contracting. 2. Atria-ventricular and semi-lunar valves are closed. 3. Blood can't leave the ventricles.

Question 41

Describe late ventricular systole in the cardiac cycle (4 points). .

Answer 41

1. Atria walls are relaxed and ventricle walls are contracting. 2. Atria-ventricular valves are closed to prevent back-flow of blood. 3. Semi-lunar valves are open. 4. Blood is flowing out the ventricles into the arteries.

Question 42

Describe early diastole in the cardiac cycle (3 points).

Answer 42

1. Atria and ventricles walls are relaxed. 2. Atria-ventricular and semi-lunar valves are closed. 3. Blood flows from the veins into the atria.

Question 43

Describe late diastole in the cardiac cycle ( 3 points).

Answer 43

1. Atria and ventricle walls are relaxed. 2. Atria-ventricular valves are open and semi-lunar valves are closed. 3. Blood begins to flow from the atria into the ventricles slowly.

Question 44

Describe the effect on heart rate with a rise in blood pressure (6 points).

Answer 44

1. Increased impulse from baroreceptor to medulla oblongata. 2. Increased impulse via parasympathetic nerve to sino-atrial node. 3. Parasympathetic is inhibitory so reduced impulses from sin-atrial node. 4. More impulses arrive to atria-ventricular node. 5. Heart rate reduces.

Question 45

Describe the effect on heart rate with an increase in carbon dioxide concentration / increased acidity in the blood (5 points).

Answer 45

1. Increased impulses from chemoreceptor to medulla oblongata. 2. Increased impulses via sympathetic nervous system to sino-atrial node. 3. Sympathetic is excitatory so increases impulses from sino-atrial node. 4. More impulses arrive to atrial-ventricular node. 5. Heart rate increases.