Response to stimuli

Question 1

sequence from stimulus to response

Answer 1

stimulus > receptor > coordinator > effector > response

Question 2

what is taxis?

Answer 2

directional movement towards favourable stimulus

Question 3

what is kinesis?

Answer 3

non-directional movement - not towards or away from stimulus

Question 4

tropism?

Answer 4

growth of part of a plant in response to a directional stimulus

Question 5

three things plants respond to? what is it called?

Answer 5

light (phototropism)
gravity (gravitropism)
water (hydrotropism)

Question 6

what is IAA?

Answer 6

plant growth factor, indoleacetic acid, controls plant cell elongation

Question 7

what is the central nervous system (CNS) made up of?

Answer 7

brain +spinal cord

Question 8

what is the peripheral nervous system (PNS) made up of?

Answer 8

pairs of nerves that originate from either the brain or the spinal cord

Question 9

what is the peripheral nervous system divided into?

Answer 9

sensory neurones - carry nerve impulses from receptors towards the CNS
motor neurones - carry nerve impulses away from the CNS to effectors

Question 10

what is the motor nervous system subdivided into?

Answer 10

voluntary nervous system - carries nerve impulses to body muscles and is under voluntary (conscious) control
autonomic nervous system - nerve impulse to gland, smooth muscle + cardiac muscle, is not under voluntary control, is involuntary

Question 11

reflex arc?

Answer 11

stimulus > receptor > sensory neurone > coordinator > motor neurone > effector > response

Question 12

importance of reflex arcs?

Answer 12

involuntary - don’t require decision-making powers of brain
protect body from harm
fast, because short neurone pathway
action is rapid

Question 13

what does the autonomic nervous system do?

Answer 13

controls the involuntary activities of internal muscles and glands

Question 14

what are the two divisions of the autonomic nervous system?

Answer 14

sympathetic nervous system - stimulates effectors, speeds up activity, fight or flight response
parasympathetic nervous system - inhibits effectors, slows down activity, conserves energy
THEY ARE ANTAGONISTIC

Question 15

sequence of events of control of basic heart rate?

Answer 15

• wave of electrical excitation from SAN across both atria, they contract
• AV septum prevents wave crossing to the ventricles
• wave of excitation enters AVN (which lies between atria)
• AVN, after short delay, conveys wave between ventricles along Purkyne tissue, which collectively make up the bundle of His
• bundle of His conducts wave through AV septum to base of ventricle, and branches into smaller fibres of Purkyne tissue
• wave of excitation released from Purkyne tissue, ventricles contract quickly at same time, from bottom of heart upwards

Question 16

what are changes to heart rate controlled by?

Answer 16

the medulla oblongata

Question 17

what are the two centres of the medulla oblongata?

Answer 17

• centre that increases heart rate, linked to SAN by sympathetic nervous system
• centre that decreases heart rate, linked to SAN by parasympathetic nervous system

Question 18

what are chemoreceptors?

Answer 18

found in the wall of carotid ateries (the arteries that serve the brain). sensitive to changes in pH of blood that result from changes in CO2 conc.

Question 19

how does the process of control work when one exercises and CO2 conc. increases?

Answer 19

increased muscular/metabolic activity
more CO2 produced by tissues from increased respiration
blood pH lowered
chemoreceptors increase frequency of impulses to medulla oblongata
centre that speeds heart rate increases frequency of impulses to SAN via sympathetic nervous system
SAN increases heart rate
increased blood flow removes CO2 faster
CO2 CONC. BACK TO NORMAL

Question 20

how do pressure receptors operate when blood pressure is higher than normal?

Answer 20

transmit more nervous impulses to centre in m.o that decreases heart rate
centre sends impulses via parasympathetic nervous system to SAN, leads to decrease in heart rate

Question 21

how do pressure receptors operate when blood pressure is lower than normal?

Answer 21

transmit more nervous impulses to centre in m.o that increases heart rate
centre sends impulses via sympathetic nervous system to SAN, leads to increase in heart rate