5.1.5 Plant and Animal Responses

Question 1

What is the central nervous system (CNS)?

Answer 1

• made up of the brain and the spinal cord

Question 2

What is the peripheral nervous system?

Answer 2

• made up of the neurones that connect the CNS to the rest of the body
• has two different functional systems

Question 3

What are the two different functional systems of the peripheral nervous system?

Answer 3

• somatic nervous system: controls conscious activities
• autonomic nervous system: controls unconscious activities
• this has two divisions which have opposite effects on the body

Question 4

What is the sympathetic nervous system?

Answer 4

• part of the peripheral nervous system and the autonomic nervous system
• the flight or fight system
• releases the neurotransmitter nooradrenaline

Question 5

What is the parasympathetic nervous system?

Answer 5

• rest and digest
• calms the body down
• neurones release the neurotransmitter acetylcholine

Question 6

What does the hypothalamus found and what does it control?

Answer 6

• found just above the pituitary gland
• maintains body temperature
• hypothalamus produces hormones and controls the pituitary gland

Question 7

Where is the pituitary gland and what does it do?

Answer 7

• found beneath hypothalamus
• controlled by the hypothalamus
• releases hormones and stimulates other glands e.g. adrenal glands to release their hormones

Question 8

Where is the medulla oblongata and what is its function?

Answer 8

• at the base of the brain, top of the spinal cord
• automatically controls breathing rate and heart rate

Question 9

Where is the cerebellum and what does it control?

Answer 9

• underneath the cerebrum, at the back
• has a folded cortex
• controls muscle coordination, posture and coordination of balance

Question 10

Where is the cerebrum and what does it control?

Answer 10

• largest part of the brain
• divided into the two cerebral hemispheres
• has a thin outer layer called cerebral cortex, which is highly folded
• involved in vision, hearing, thinking, learning

Question 11

Describe the blinking reflex

Answer 11

• sensory nerve endings in the cornea are stimulated by touch
• a nerve impulse is sent along the sensory neurone to a relay neurone in the CNS
• impulse is then passed from the relay neurone to motor neurones
• motor neurones send impulses to the effectors, the orbicularis oculi muscles that move your eyelids
• these muscles contract causing your eyelids to close quickly and prevent your eye from being damaged

Question 12

Describe the knee jerk reflex

Answer 12

• stretch receptors in the quadriceps muscle detect that the muscle is being stretched
• a nerve impulse is passed along a sensory neurone, which communicates directly with a motor neurone in the spinal cord
• no relay neurone involved
• motor neurone carries the nerve impulse to the effector (quadriceps muscle), causing it to contract so the lower leg moves forward quickly

Question 13

Describe what happens during fight or flight response?

Answer 13

• nerve impulses from sensory neurones arrive at the hypothalamus, activating both the hormonal system and the sympathetic nervous system
• the pituitary gland is stimulated to release the hormone ACTH
• this causes the cortex of the adrenal gland to release steroidal hormones
• the sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region of the adrenal gland which then has these effects: (see other flashcard)

Question 14

What effects do adrenaline and sympathetic nervous system have during fight or flight response?

Answer 14

• heart rate is increased, so blood is pumped around faster in the body
• muscles around the bronchioles relax, so breathing is deeper
• glycogen is converted to glucose, so more glucose is available for muscles to respire
• muscles in the arterioles supplying the skin and gut constrict and muscles in the arterioles supplying the heart, lungs and skeletal muscles dilate, so blood is diverted from the skin in the gut to the heart, lungs, and skeletal muscles
• erector pili muscles in the skin contract, making hairs stand on end so the animal looks bigger

Question 15

How do the nervous and hormonal systems control heart rate?

Answer 15

Nervous system:

• the sinoatrial node (SAN) generated electrical impulses that cause the cardiac muscles to contract
• the rate at which the SAN fires are unconsciously controlled by a part of the brain called the medulla
• animals need to alter their heart rate to respond to internal stimuli
• stimuli are detected by pressure receptors and chemical receptors:
• baroreceptors in the aorta and vena cava are stimulated by high and low pressure
• chemoreceptors in the aorta, the carotid artery and in the medulla monitor the oxygen level in the blood and also CO₂ and pH
• electrical impulses from receptors are sent to the medulla along sensory neurones
• the medulla process information and sends impulses to the SAN along motor neurones (look at the table)

Hormonal:

• helps to control heart rate by releasing adrenaline
• adrenaline bonds to specific receptors in the heart
• this causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and heart pumps more blood