Animal Responses

Question 1

Outline the process of muscle contraction

Answer 1

Action potential from motor neurone arrives @ muscle cell

AP propagated along sarcolemma & down t-tubules - triggers voltage gated receptors in sarcoplasmic reticulum ; Ca2+ ions released into sarcoplasm

Ca2+ binds to troponin causing it to change shape; moving tropomyosin out of the actin-myosin binding site

Globular myosin head binds to actin-myosin binding site so form actin-myosin cross bridge, sliding the actin filament along to the centre of the sarcomere

Question 2

what is Central Nervous System composed of?

Answer 2

brain & spinal cord; relay neurones & cell bodies of motor neurones

Question 3

what is the peripheral nervous system composed of?

Answer 3

sensory neurones & axons of motor neurones
(sensory system & motor system)
tip: peripheral means edge

Question 4

what 2 categories are the PNS motor neurones divided into?

Answer 4

somatic; conscious control (voluntary)
&
autonomic; unconscious control (involuntary) eg intestinal smooth muscle contractions

Question 5

where do autonomic motor neurones carry nerve impulse from and to?

Answer 5

CNS to the:

cardiac muscle / smooth muscle in gut / blood vessels / glands / bladder

Question 6

difference between somatic and autonomic motor neurones

Answer 6

somatic are myelinated

Question 7

what 2 categories can the autonomic nervous system be split into?

Answer 7

sympathetic; involves noradrenaline- fight or flight response to threatening conditions
&
parasympathetic; involves acetylcholine; relaxed response maintaining suitable state for non-threatening conditions

Question 8

where is the cerebrum located in the brain & what does it control?

Answer 8

involved in 'higher' brain activities
- conscious thoughts
- emotional responses
- intelligence
decision-making, judgement
- factual memory
-overriding reflexes

Question 9

where is the medulla oblongata located in the brain & what does it control?

Answer 9

in brainstem @ top of spinal cord
- controls involuntary responses (autonomic); various centres for: heart rate, breathing rate, digestive system(smooth muscle movements in gut), blood pressure

Question 10

where is the hypothalamus located in the brain & what does it control?

Answer 10

controls autonomic nervous system & endocrine glands (eg. releases hormones that control pituitary gland)
- homeostatic control (eg. temp, osmoreg)

Question 11

where is the pituitary gland located in the brain & what does it control?

Answer 11

endocrine gland under the hypothalamus; controls endocrine system

Question 12

outline the corneal blink reflex pathway

Answer 12

4. 5.

Question 13

outline the corneal blink reflex pathway

Answer 13

1. sensory neurone in cornea stimulated, which enters the pons (area of brainstem)
2. relay neurone
3. motor neurone
4. effector = eyelid muscle; contracts

Question 14

where is the cerebellum located in the brain & what does it control?

Answer 14

underneath cerebrum (tip; belly)

• muscle coordination (memory)
• balance
• posture control

Question 15

what stimulates the blink reflex ?

Answer 15

sudden movements close to eye
foreign object touching eye
loud sounds

Question 16

what is a reflex arc

Answer 16

the nerve pathway involved in a reflex action

Question 17

why is the knee jerk reflex described as a spinal reflex?

Answer 17

nervous pathway passes through spinal cord rather than brain

Question 18

outline the knee jerk reflex pathway

Answer 18

only involves 2 neurones: sensory neurone –> motor neurone

1. tapping patella kneecap stretches the quadriceps muscles
3. 4.

Question 19

what is the role of ATP in muscle contraction

Answer 19

part of the myosin head acts as an ATPase; converts ATP–>ADP + Pi, releasing energy

1. myosin head binds to actin filament; actin-myosin cross bridge forms
2. myosin head moves (tilts backwards), causing the actin filament to slide past the myosin filament
3. after the power stroke, another ATP binds to myosin head; BREAKS the cross-bridge
4. myosin head returns to original position (slides forward), as ATP is hydrolysed, energy is released for this movement to occur
5. same process used for the myosin head to make a new cross-bridge further along the actin filament; sliding the actin further along the myosin

Question 20

there is only enough ATP readily available in muscle tissue to support 1-2 secs of muscle contraction, how is the ATP regenerated to allow contraction to continue?

Answer 20

1. Bohr effect draws more O2 from Hb into the blood, diffusing into the cell.AEROBIC RESP produces more ATP
2. Anaerobic Resp generates ATP: but leads to lactic acid which is toxic if built up
3. Creatine Phosphate in sarcoplasm = reserve of phosphate groups; which can be transferred to ADP quickly by creatine phosphotransferase to generate more ATP.

Question 21

outline what happens at the neuromuscular junction

Answer 21

1. AP arrives @ end of axon- opens Ca2+ channels in membrane so Ca2+ floods into the end of axon
2. Ca2+ binds to Vesicles of acetylcholine; causes them to move towards & bind with fuse with plasma membrane
3. Acetylcholine diffuses across gap & fuses with receptors on sarcolemma- opens Na+ channels , causing Na+ influx into muscle fibre- depolarises sarcolemma.
4. wave of depolarisation spreads along sarcolemma & down transverse(t)tubules into the muscle fibre

Question 22

Outline the basic reflex arc

Answer 22

1. Receptor detects stimulus and creates an action potential in the sensory neurone.
2. Sensory neurone carries impulse to spinal cord.
3. Relay neurone connects sensory neurone to motor neurone in the brain or spinal cord.
4. Motor neurone carries an impulse to the effector to carry out the appropriate response.
5. Effector organ changes in response to stimulus to avoid harm.