5.1.5 Animal responses

Question 1

Gross structure

Answer 1

5 main areas:
Cerebrum
Cerebellum
Medulla Oblongata
Hypothalamus
Pituitary gland

Question 2

Cerebrum

Answer 2

• Controls voluntary actions, learning, memory, personality, conscious thought

Question 3

Cerebellum

Answer 3

• Controls unconscious functions, posture, balance and non-voluntary movement - co-ordinates movement not initiate.
• If damaged, can suffer from jerky + uncoordinated movement.

Question 4

Medulla Oblongata

Answer 4

• Used in autonomic control, heart rate + breathing rate
• Also controls activities like swallowing, peristalsis and coughing

Question 5

Hypothlamus

Answer 5

• Main controlling region for the autonomic NS.
• Has 2 centres - for parasympathetic + sympathetic
• Controls complex patterns of behaviour - feeding, sleeping, aggression
• Monitors composition of blood plasma, conc of water + blood glucose - rich blood supply
• Produces hormones - endocrine gland, produces hormones

Question 6

Pituitary gland

Answer 6

• Stores and releases hormones that regulate many body functions
• Anterior pituitary - produces 6 hormones, e.g. FSH (involved in reproduction + growth hormones)
• Posterior pituitary - stores + releases hormones produced by hypothalamus, ADH involved in urine production

Question 7

Cerebrum (extended)

Answer 7

• Receives sensory info, interprets based on prior knowledge, sends impulses along motor neurones to effectors - appropriate response
• Highly convoluted - large SA + capacity for complex activity
• Split in half - cerebral hemispheres - each control the opposite side of the body.
• Cerebral cortex - outer layer - consists of frontal, parietal, temporal and occipital lobe.

Question 8

How is info processed by the cerebrum

Answer 8

• Each sensory area within the cerebral hemispheres receives info from receptor cells located in sense organs
• Info is passed onto other areas in the brain - association areas
• Impulses come into motor areas where motor neurones send out impulses - move skeletal muscles
• Size of sensory/motor area is in proportion to the relative number of motor/sensory endings in it.

Question 9

Process of muscle contraction

Answer 9

1. Tropomyosin molecule prevents myosin prevents myosin head from attaching to the binding site on the actin molecule
2. Ca2+ released from sarcoplasmic reticulum cause the tropomyosin molecule to pull away from the binding sites on the actin molecule
3. Myosin head now attaches to the binding site on the actin filament
4. Head of myosin changes angle, moving the actin filament along as it does so, ADP molecule is released
5. ATP molecule fixes to myosin head, causing it to detach from the actin filament
6. Hydrolysis of ATP to ADP by myosin provides the energy for the myosin head to resume its normal position
7. Head of myosin reattaches to a binding site further along the actin filament and the cycle is repeated.

Question 10

Skeletal muscle

Answer 10

Make up bulk of body muscle tissue. Responsible for movement e.g. biceps, triceps
Striated fibre
Conscious (voluntary)
Regularly arranged so muscle contracts in one direction
Rapid and short contraction
Muscles showing cross stiriations are known as striated or striped muscles
Fibres are tubular and multinucleated

Question 11

Cardiac muscle

Answer 11

Found only in the heart. Myogenic, causing heart to beat regularly.
Specialised striated fibre
Involuntary
Cells branch and interconnected, resulting in simultaneous contraction
Intermediate speed and length of contraction
Cardiac muscle does show striations but they are much fainter than those in skeletal muscles.
Fibres are branched and uninucleated

Question 12

Involuntary/smooth muscle

Answer 12

Found in many party’s of the body e.g. walls of hollow organs like the stomach and blood vessels
Non-striated
Involuntary
No regular arrangement - different cells can contract in different directions
Slow speed and can remain contracted for a relatively long time
Muscles showing no cross striations - non-striated muscles
Fibres are spindle shaped + uninucleated

Question 13

Myofibrils

Answer 13

Actin - thinner filament, consists of 2 strands twisted around each other
Myosin - thicker filament, consists of long rod-shaped fibres with bulbous heads that project to one side.
- Light bands - region where actin + myosin don’t overlap, only actin.
- Dark bands (A-band) - where myosin is overlapped with actin
- Z-line - line at the centre of each light band
- Sarcomere - distance between adjacent Z-lines, functional unit of myofibril, shortens when contracted
- H-zone- lighter coloured in the centre of each dark band - only contains myosin, decreases when contracted.