Stimuli And Responses

Question 1

Define taxis

Answer 1

Directional movement in response to a stimulus eg woodlice

Question 2

Define kenesis

Answer 2

Non directional movement in response to a stimulus.

Question 3

What are receptors made of and what do they do

Answer 3

Cells , proteins on cell surface membranes and they detect stimuli

Question 4

What do baroreceptors do

Answer 4

Detect changes in blood pressure

Question 5

What are effectors and what do they do

Answer 5

Cells that bring about a response to a stimulus to produce an effect they include muscle cells and cells found in glands eg pancreas

Question 6

How do receptors communicate with effectors

Answer 6

Via the nervous system or hormonal system of both

Question 7

What do sensory neurons do

Answer 7

Transmit electrical impulses from the receptors to the CNS

Question 8

What do motor neurones do

Answer 8

Transmit electrical impulses from the CNS to effectors

Question 9

What do relay neurones do

Answer 9

Sensory to motor neurones

Question 10

What is the pathway of nervous communication

Answer 10

Stimulus - receptors - sensory neurone - CNS- motor neurone - effectors - response

Question 11

Why is the nervous response deprived as localized

Answer 11

Neurotransmitters are secreted directly onto cells

Question 12

What is a simple reflex

Answer 12

A rapid involuntary response to a stimulus it does not go through conscious part of brain just spinal chord

Question 13

What is a tropism

Answer 13

The response of a plant to a directional stimulus

Question 14

What is phototropism and how do shoots and roots react to it

Answer 14

Growth of a plant in response to light shoots are positively phototrophic roots are negatively phototrophic

Question 15

What is gravitropism and how do roots and shoots react to it

Answer 15

The growth of a plant in response to gravity shoots are negatively gravitropic and roots are positively gravitropic

Question 16

What do receptors in the nervous system do

Answer 16

Convert the energy of the stimulus into the electrical energy bused by neurones

Question 17

What is resting potential

Answer 17

Inside of cell is relatively negative to outside of cell this creates a potential difference

Question 18

What is generator potential

Answer 18

When stimulus is detected the cell membrane is excited and becomes more permeable allowing more ions to move in and out of the cell altering the potential difference, when its due to a stimulus it is generator potential

Question 19

What is an action potential

Answer 19

When generator potential reaches threshold it’ll trigger an action potential ( electrical impulse alone a neurone )

Question 20

What is the strength of the stimulus measured by

Answer 20

Frequency of action potentials

Question 21

What is the pacinian corpuscle

Answer 21

A mechanoreceptor that detect pressure or vibrations

Question 22

What is the structure of the pacinian corpuscle

Answer 22

Contain the end of a sensory neurone wrapped in loads of layers of connective tissue called lamellae

Question 23

How is the pacinian corpuscle stimulated

Answer 23

Tap on the sync, lamellae are deformed and press on the sensory nerve ending this causes sensory neurones cell membrane to stretch deforming stretch mediated sodium ion channels so they open and sodium ions diffuse into the cell creating generator potential , this may reach the threshold and create an action potential

Question 24

What are photorecepors in the eye and how are they controlled

Answer 24

Detect light and muscles of iris control it

Question 25

What do you call the area of the eye that has the most photoreceptors

Answer 25

Fovea

Question 26

Where are nerve impulses carried in the eye

Answer 26

Nerve impulses from receptor cells are carried from retina to the brain by the optic nerve ( bundle of neurones )

Question 27

Where is the blind spot of the eye

Answer 27

Where the optic nerve leaves the eye , there aren’t any photoreceptors so it’s not sensitive to light

Question 28

How do photoreceptors work?

Answer 28

Light enters the eye , hits photoreceptors and is absorbed by optical pigments. Light bleaches the pigments causing a chemical change altering the membrane permeability to sodium ions. A generator potential is created and if it reaches threshold a nerve impulse is sent along bipolar neurone which connect photoreceptors to the optic nerve which takes impulses to the brain

Question 29

Where are rods and cones found ?

Answer 29

Rods are in the peripheral parts of the retina and cones are packed together in the fovea

Question 30

What are the differences between rods and cones ?

Answer 30

Rods - info in black and white , many rods joins 1 bipolar neurone , highly sensitive to light , give low visual acuity
Cones - give info in colour , one joins one bipolar neurone , low sensitivity to light, gives high visual acuity

Question 31

What’s the difference between the CNS and the peripheral nervous system ?

Answer 31

CNS- brain and spinal chord

Peripheral - made up of neurones that connect the CNS to rest of body

Question 32

What is the peripheral nervous system ?

Answer 32

Somatic and autonomic.
Somatic controls conscious activities autonomic controls unconscious activities eg digestion
Autonomic is sympathetic and parasympathetic . Sympathetic is “fight or flight “ parasympathetic is “rest and digest “

Question 33

Cardiac muscle is myogenic what does that mean ?

Answer 33

It can contract and relax without receiving signals from nerves

Question 34

What is the SAN and what does it do

Answer 34

Small mass of tissue in wall of right atrium that acts as a pace maker by sending refuel waves of electrical impulses to atrial walls which causes right and left atria to contract at same time

Question 35

What does non conducting collagen tissue do

Answer 35

Prevents waves of electrical activity from being passed directly from the Syria to the ventricles instead they go to AVN

Question 36

What does the AVN do

Answer 36

Passes waves of electrical activity on to the bundle of His but there is a slight delay before the AVN reacts to make sure the atria have emptied before the ventricles contract.

Question 37

What is the bundle of his and what does it do

What is purkyne tissue and what does it do

Answer 37

Group of muscle fibers responsible for conducting waves of electrical activity between ventricles to the apex of the heart the bundle splits into finer muscle fibers in the ventricle walls these are the purkyne tissue which carries waves of electrical activity into the muscular walls or lefgcand right ventricles causing them to contract simultaneously from bottom up

Question 38

What is the route of waves of electrical activity in heart beats

Answer 38

SAN, AVN , bundle of his , purkyne fibers

Question 39

What controls rate at which SAN generates electrical impulses ?

Answer 39

Medulla

Question 40

What are pressure receptors and where do you find them

Answer 40

Eg baroreceptors in aorta and carotid arteries stimulated by blood pressure

Question 41

How is high blood pressure controlled

Answer 41

Baroreceptors - Hugh blood pressure - impulse along sensory neurone - medulla - impulse along parasympathetic neurone - secreted acetylcholine which binds to receptors on SAN - heart rate slows down to reduce blood pressure to normal

Question 42

How is low blood o2 high co2 or low blood ph levels controlled

Answer 42

Chemoreceptors detect chemical change in blood and sends impulses along sensory neurones to medulla which sends impulses along sympathetic neurones these secrete Noradrenaline which binds to receptors on SAN this causes heart rate to increase to return o2 co2 and pH levels back to normal