Module 5.5 - Plant And Animal Responses - Animals

Question 1

What is the autonomic nervous system?

Answer 1

Part of the nervous system responsible for controlling the involuntary motor actions of the body
e.g. glands, cardiac muscle, smooth muscle in walls of blood vessels, airways and digestive system
Neurones are mostly non-myelinated as the control of many of these effectors does not need rapid responses
At least two neurones involved in connection between CNS and effector, connected at small swellings called ganglia

Question 2

What is the central nervous system?

Answer 2

CNS
The central part of the nervous system composed of the brain and spinal cord
Coordinates responses
Many synapses
Brain is mostly made of non-myelinated relay neurones (grey matter)
Spinal cord has grey matter and white matter (myelinated relay neurones) for more rapid communication

Question 3

What is the peripheral nervous system?

Answer 3

PNS

The sensory and motor nerves connecting the sensory receptors and effectors to the CNS

Question 4

What is the somatic nervous system?

Answer 4

Part of the nervous system responsible for controlling the voluntary motor activities of the body
e.g. skeletal muscles
Neurones are mostly myelinated so responses can be rapid
One single motor neurone connects the CNS to the effector

Question 5

What is the sensory nervous system?

Answer 5

Connects receptors to CNS
Dendrons of neurones enter spinal cord at dorsal root where their cell body also is
Short axon connects to relay neurones in the CNS

Question 6

What is the sympathetic system?

Answer 6

‘Fight or flight’
Consists of many nerves leading out of the CNS, each leading to a separate effector
Ganglia just outside CNS
Short pre-ganglionic neurones, long post-ganglionic neurones (variable in length, depends on position of effector)
Uses noradrenaline as the neurotransmitter
Increases activity, prepares body for activity
Most active at times of stress
Effects include: increases heart rate; dilates pupils; increases ventilation rate; reduces digestive activity; orgasm

Question 7

What is the parasympathetic system?

Answer 7

‘Rest or digest’
Consists of a few nerves leading out of the CNS, which divide up and lead to different effectors
Ganglia in effector tissue
Long pre-ganglionic neurones (variable length, depends on position of effector), short post-ganglionic neurones
Uses acetylcholine as the neurotransmitter
Decreases activity - conserves energy
Most active during sleep or relaxation
Effects include: decreases heart rate; constricts pupils; reduces ventilation rate; increases digestive activity; sexual arousal

Question 8

What is the motor nervous system?

Answer 8

Conducts action potentials from CNS to effectors

Divided into somatic and autonomic

Question 9

Points about the cerebrum

Answer 9

2 hemispheres connected by corpus callosum
Controls: conscious thought; memory; conscious actions (e.g. speech); emotions
Outer layer is the cerebral cortex, divided into areas responsible for the senses
Sensory areas receive action potentials, association areas interpret this and coordinate response
Motor areas on left side send action potentials to effectors on right side of body and visa Versace

Question 10

Points about the cerebellum

Answer 10

Controls: fine movement coordination; posture; balance (e.g. riding a bike, moving muscles to write or coordinate walking, proprioception)
This control is often learnt and nervous pathways become stronger with practice, then becoming ‘second nature’

Question 11

Points about the medulla oblongata

Answer 11

Controls: non-skeletal muscles (e.g. bladder, swallowing, cardiac muscle, smooth muscle in gut)
Action potentials are sent via the autonomic nervous system
Contains: cardiac centre; respiratory centre; vasometer centre (controls circulation and blood pressure

Question 12

Points about the hypothalamus

Answer 12

Controls: homeostasis (e.g. thermoregulation and osmoregulation using negative feedback)
Contains its own receptors (e.g. osmoreceptors, thermoreceptors)
Also regulates eating and sleeping patterns

Question 13

Points about the pituitary gland

Answer 13

Made up of the posterior and anterior lobe
Posterior lobe: linked to hypothalamus by neurosecretry glands; hypothalamus makes hormones (e.g. ADH) and PPG secretes them
Anterior lobe: makes its own hormones (control e.g. lactation, stress, growth); realising factors (hormones) from hypothalamus cause APG to release hormones

Question 14

What is the role of the brain in coordinating responses?

Answer 14

Receptors sense threatening stimulus
Action potential sent to sensory centres in cerebrum and then to association centres which coordinate a response
Cerebrum stimulates hypothalamus in response to threat
Hypothalamus stimulates sympathetic system and the anterior pituitary gland

Question 15

What is the role of the sympathetic nervous system in coordinating responses?

Answer 15

Increases activity of effectors via nervous impulses for rapid response
Stimulates adrenal medulla to release adrenaline (which brings about responses in effectors) for longer response

Question 16

Describe the mechanism of adrenaline action

Answer 16

Adrenaline acts as a first messenger by travelling through the blood and binding to receptors on the plasma membrane of target The binding causes a G-protein on the membrane to activate the enzyme adenyl cyclase
Adenyl cyclase converts ATP to cyclic AMP (cAMP), which is the second messenger inside the cell
cAMP causes an effect inside the cell by activating enzyme action, and the precise effect depends on the cell that the adrenaline has bound to

Question 17

Physiological changes associated with the fight or flight response

Answer 17

Pupils dilate
Heart rate and blood pressure increase
Blood vessels to digestive system are constricted
Blood vessels to muscles and liver are dilated
Blood glucose levels increase
Metabolic rate increases
Erector pili muscles in skin contract
Ventilation rate and depth increase
Endorphins are released in the brain

Question 18

Describe the blinking reflex

Answer 18

It is a cranial reflex (goes to brain but doesn’t involve conscious thought)
Protects eyes from damage by covering them
It is a corneal and/or optical reflex
Stimulated by: foreign object touching eye (corneal reflex); sudden bright light (optical reflex); loud sounds; sudden movements close to the eye

Question 19

What is the corneal reflex?

Answer 19

A sensory neurone in the cornea takes the action potential to an unmyelinated relay neurone in the pons
This travels along a motor neurone out of the brain to the facial muscles, causing the eyelids to blink
It is a very short and direct pathway, taking about 0.1s

Question 20

How can the corneal reflex be overridden?

Answer 20

The sensory neurone in the cornea also sends the action potential to myelinated neurones in the pons
They carry the action potential to the sensory region in the cerebral cortex, which can send inhibitory signals to the motor centre in the pons
The myelinated neurones carrying impulses to and from the cerebral cortex transmit action potentials much more quickly than the unmyelinated relay neurones in the pons
Therefore, the inhibitory action potentials can prevent the formation of an action potential in the motor neurone

Question 21

What is the optical reflex?

Answer 21

Protects light-sensitive cells of retina from damage
Stimulus (sudden bright light) is detected by retina and reflex is mediated by the optical centre in the cerebral cortex
Slightly slower than the corneal reflex

Question 22

What is the knee jerk reflex?

Answer 22

Spinal reflex - nervous pathway passes through spine, not brain
When muscles at the front of the thigh are stretched, stretch receptors (muscle spindles) detect the increase in length of the muscle
If this stretching is unexpected, a reflex action causes contraction of the same muscle

Question 23

Why can’t the knee jerk reflex be inhibited?

Answer 23

Its nervous pathway only consists of a sensory and motor neurone
As there is no relay neurone the brain cannot stop the reflex

Question 24

Why is the knee jerk reflex required?

Answer 24

Enables balance

Question 25

How is muscle contraction controlled?

Answer 25

When the muscle is stimulated, the action potential passes along the sarcolemma and down the transverse tubules into the muscle fibre
The action potential is carried to the sarcoplasmic reticulum, which stores calcium ions, and causes the release of calcium ions into the sarcoplasm
The calcium ions bind to the troponin, which alters their shape pulling the tropomyosin aside, and exposes the binding sites on the actin
Myosin heads bind to the actin, forming cross-bridges between the filaments
The myosin heads move, pulling the actin filament past the myosin filament
The myosin heads detach from the actin and can bind again further up the actin filament

Question 26

How to maintain the supply of ATP in the muscles

Answer 26

Muscle tissue contains a large number of mitochondria where aerobic respiration can occur
The Bohr effect helps release more oxygen from the haemoglobin in the blood
Anaerobic respiration is in the sarcoplasm of the muscle tissue
Creatine phosphate in the sarcoplasm acts as a reserve store of phosphate groups, which are transferred to ADP molecules to produce ATP

Question 27

Role of ATP in muscle contraction

Answer 27

Supplies energy for contraction
Myosin heads attaches to the actin filament forming a cross-bridge
The myosin head tilts backwards, causing the thin filament to slide past the myosin filament (power stroke), and ADP and an inorganic phosphate ion are released from the myosin head
After the power stroke, a new ATP molecule attaches to the myosin head, breaking the cross-bridge
The myosin head then returns to its original position (swings forward again) as the ATP is hydrolysed, releasing the energy to make this movement occur
The myosin head can now make a new cross-bridge further along the actin filament