5.1.5 Animal

Question 1

How is the mammalian nervous system organised structurally?

Answer 1

Split into the CNS - consists of brain and spinal cord - and PNS - consists of all the neurones connecting the CNS to the rest of the body (sensory and motor neurones)

Question 2

How is the peripheral nervous system organised functionally?

Answer 2

Somatic nervous system - under conscious control. It is used when voluntary actions are carried out. The somatic nervous system carries impulses to the body’s muscles.
Autonomic nervous system - under subconscious control. It is used when the body does things automatically. The autonomic nervous system carries nerve impulses to glands, smooth muscle, and cardiac muscle.

Question 3

How is the autonomic nervous system divided?

Answer 3

It is split into the sympathetic nervous system and the parasympathetic nervous system. Generally, if an outcome increases activity, it involves the sympathetic nervous system, while if an outcome decreases activity, it involves the parasympathetic nervous system.

Question 4

What are the five main areas of the brain?

Answer 4

Cerebrum
Cerebellum
Medulla oblongata
Hypothalamus
Pituitary gland

Question 5

What is the function of the cerebrum?

Answer 5

Controls voluntary actions, such as learning, memory, personality, and conscious thought.

Question 6

What is the function of the cerebellum?

Answer 6

Controls unconscious functions such as posture, balance, and non-voluntary movement.

Question 7

What is the function of the medulla oblongata?

Answer 7

Used in autonomic control, such as for heart and breathing rate.

Question 8

What is the function of the hypothalamus?

Answer 8

The hypothalamus is the main controlling region for the autonomic nervous system. It has two centres - one for the sympathetic nervous system and one for the parasympathetic nervous system. It helps to control complex behavioural patterns, monitoring blood plasma composition, and hormone production.

Question 9

What is the function of the pituitary gland?

Answer 9

The main hormone release area of the body. It is divided into two sections:
The anterior pituitary gland produced 6 hormones including FSH. The posterior pituitary gland stores and releases hormones produced by the hypothalamus, such as ADH.

Question 10

Describe the general steps of the reflex arc.

Answer 10

Receptor, sensory neurone, relay neurone, motor neurone, effector.

Question 11

Describe the knee-jerk reflex.

Answer 11

When the leg is tapped below the knee, the patellar tendon stretches, acting as a stimulus. This stimulates a reflex arc causing the extensor muscle on top of the thigh to contract. The relay neurone inhibits the motor neurone of the flexor muscle, causing it to relax. This contraction, coordinated with the relaxation of the antagonistic flexor hamstring muscle, causes the leg to kick.

Question 12

Describe the blinking reflex.

Answer 12

When the cornea is irritated by a foreign body, the stimulus triggers an impulse along a sensory neurone. The impulse then passes through a relay neurone in the lower brain stem. Impulses are then sent along branches of the motor neurone to initiate a motor neurone to close the eyelids. The reflex initiates a consensual response - both eyes are closed in response to the stimulus.

Question 13

What is unique about the blinking reflex?

Answer 13

It is a cranial reflex, involving the brain rather than the spinal cord.

Question 14

What are the three types of muscle?

Answer 14

Skeletal, cardiac, and involuntary

Question 15

What is skeletal muscle?

Answer 15

Muscle that makes up the bulk of muscle tissue. They are responsible for movement

Question 16

What is cardiac muscle?

Answer 16

Muscle cells found only in the heart. They are myogenic

Question 17

What is involuntary muscle also known as?

Answer 17

Smooth muscle

Question 18

Describe skeletal muscle

Answer 18

Striated
Voluntary contraction
Arranged so muscle contracts in one direction
Rapid contraction
Short contraction

Question 19

Describe cardiac muscle

Answer 19

Specialised striated
Involuntary contraction
Cells branch and interconnect, causing simultaneous contraction
Intermediate speed and length

Question 20

Describe smooth muscle

Answer 20

Non-striated
Involuntary contraction
No regular arrangement
Slow contraction
Long contraction

Question 21

What are skeletal muscles made up of?

Answer 21

Bundles of muscle fibres

Question 22

What are the muscle fibres enclosed within?

Answer 22

A plasma membrane known as the sarcolemma

Question 23

What are myofibrils?

Answer 23

Long, cylindrical organelles that are made of protein and specialised for contraction. Each muscle fibre contains many myofibrils

Question 24

What protein filaments are myofibrils made up of?

Answer 24

Actin - thin filament
Myosin - thick filament

Question 25

What are light bands?

Answer 25

Areas where the actin and myosin filaments do not overlap

Question 26

What are dark bands?

Answer 26

Areas where actin and myosin filaments do overlap

Question 27

What is a z-line?

Answer 27

A line found at the centre of each light band. The distance between adjacent Z-lines is called a sarcomere

Question 28

What is a sarcomere?

Answer 28

Functional unit of the myofibril

Question 29

What is a H-zone?

Answer 29

Light-coloured region at the centre of each dark band. Only myosin filaments are present at this point

Question 30

What is the mechanism of muscle contraction called?

Answer 30

The sliding filament model

Question 31

Describe stimulation of the muscle

Answer 31

Action potential arrives (neuromuscular junction) and causes depolarisation of the sarcolemma and sarcoplasmic reticulum, as the signal travels down the T tubules. The voltage-gated calcium ion channels on the sarcoplasmic reticulum open, releasing calcium ions into the sarcoplasm. These Ca+2 ions then bind to troponin. This leads to a conformational change in the troponin, so the tropomyosin is pulled along, exposing actin-myosin binding sites

Question 32

Describe attachment of the muscle

Answer 32

The myosin head binds to the actin-myosin binding site, forming cross-bridges. The myosin filament then flexes, pulling actin along. This releases ADP from the myosin head.

Question 33

Describe detachment of the muscle

Answer 33

ATP binds to the myosin head, causing it to detach from the actin-myosin binding site. Ca+2 ions then bind to the myosin head, activating ATPase, causing ATP to be hydrolysed into ADP and Pi. This energy releases returns the myosin head back to its original position.

Question 34

Describe the removal of Ca+2

Answer 34

Ca+2 ions are removed from the troponin due to the breakdown of acetylcholine by acetylcholinesterase, causing the repolarisation of the sarcolemma and t-tubules, so the Ca+2 ion channels close once again.

Question 34

Describe the removal of Ca+2

Answer 34

Ca+2 ions are removed from the troponin due to the breakdown of acetylcholine by acetylcholinesterase, causing the repolarisation of the sarcolemma and t-tubules, so the Ca+2 ion channels close once again. Ca+2 pump actively pumps Ca+2 ions from myofibrils back into sarcoplasmic reticulum

Question 35

What is the neurotransmitter at the motor end plate?

Answer 35

Acetylcholine

Question 36

Which nervous system controls the heart rate?

Answer 36

The autonomic nervous system

Question 37

What controls the heart rate in the brain?

Answer 37

The medulla oblongata

Question 38

Describe the centre in the medulla oblongata that increases heart rate

Answer 38

It sends impulses through the sympathetic nervous system via the accelerator nerve to the SAN

Question 39

Describe the centre in the medulla oblongata that decreases heart rate

Answer 39

It sends impulses through the parasympathetic nervous system via the vagus nerve

Question 40

What types of receptors provide the information that affect heart rate?

Answer 40

Baroreceptors and chemoreceptors

Question 41

What are baroreceptors?

Answer 41

Receptors that detect blood pressure. They are present in the aorta, vena cava, and carotid arteries

Question 42

What are chemoreceptors?

Answer 42

Receptors that detect changes in the level of chemicals in the blood such as CO2. Chemoreceptors are located in the aorta, the carotid artery, and the medulla

Question 43

Describe how chemoreceptors may cause a change in heart rate

Answer 43

Metabolic activity increases, resulting in more CO2 being produced from evaporation. This lowers blood pH. This is detected by chemoreceptors, so the a signal travels from the medulla to the SAN via accelerator nerve. The SAN increases heart rate, so the increased blood flow removes CO2 faster.

Question 44

How can heart rate be controlled by hormones?

Answer 44

In times of stress, adrenaline and noradrenaline are released. These hormones affect the pacemaker region of the heart itself, causing an increase in frequency of impulse produced by the SAN

Question 45

Describe the mechanism by which adrenaline acts

Answer 45

When adrenaline binds to receptor, enzyme adenylyl cyclase is activated. Adenylyl cyclase triggers the conversion of ATP into cAMP on the inner surface of the plasma membrane. The increase in cAMP levels activates protein kinases which phosphorylate and activate other enzymes. This is the second messenger model.