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OCR Biology > 5.1.5b - Animal Resposes > Flashcards

5.1.5b - Animal Resposes Flashcards

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1
Q

What are the 2 main components of the mammalian nervous system?

A
  • central nervous system (CNS) - the brain and spinal cord

* peripheral nervous system (PNS) - all of the nerves in the body

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2
Q

What are neurones?

A
  • nerve cells
  • coordinate the activities of sensory receptors, decision making centres in the CNS, and effectors
  • a bundle of neurones = a nerve
  • information is sent through the nervous system as nervous impulses (electrical signals that pass along neurones)
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3
Q

What is the somatic nervous system?

A

Works under conscious control - voluntary movement
Carries impulses to the body’s muscles

Eg - used when you decide to lift your arm

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4
Q

What is the autonomic nervous system?

A

Under subconscious control - used when the body does something automatically

Autonomic nervous system carries nerve impulses to glands, smooth muscle and cardiac muscle

Eg - causing heart to beat, digesting food

Can be divided into sympathetic and parasympathetic nervous system

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5
Q

What is the sympathetic nervous system?

A

Branch of the autonomic nervous system that is active under stressful conditions (eg ‘fight or flight’)

Stimulates effectors, speeding up activity

Neurotransmitter = noradrenaline

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6
Q

What is the parasympathetic nervous system?

A

A branch of the autonomic nervous system that is active under normal, resting conditions (eg ‘rest and digest’)

Inhibits effectors, slowing down activity

Neurotransmitter = acetylcholine

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7
Q

What are afferent vs efferent neurones?

A

Afferent - carry nerve impulses from receptors to the CNS

Efferent - carry impulses away from CNS to the effector

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8
Q

How do the sympathetic and parasympathetic nervous systems work together?

A

Opposing (antagonistic actions)
• sympathetic = heart rate increases
• parasympathetic = heart rate decreases

In general, sympathetic stimulates systems whereas parasympathetic inhibits the,

The balance of the systems regulates the involuntary activities of glands and organs

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9
Q

Compare the sympathetic and parasympathetic systems

A

BOTH:
•have motor neurones that connect the CNS to their effector organs
•have a pre-ganglionic neurone and a post-ganglionic neurone

SYMPATHETIC SYSTEM
•ganglion is near the spinal cord
• short pre-ganglionic fibres
• long post-ganglionic fibres

PARASYMPATHETIC SYSTEM
•the ganglion is close to/in the effector
• long pre-ganglionic fibre
• short post-ganglionic fibre

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10
Q

What are the different regions of the brain?

A
  • cerebrum
  • hypothalamus
  • pituitary gland
  • cerebellum
  • medulla oblongata
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11
Q

What is the general function of the cerebrum?

A

Controls voluntary actions (conscious activities), thought, vision, speech, memory, problem solving, hearing

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12
Q

What is the general function of the hypothalamus?

A

Control centre that monitors blood an helps maintain homeostasis

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13
Q

What is the general function of the pituitary gland?

A

‘Master gland’ responsible for regulating many body function,s controlling the activity of other glands

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14
Q

What is the general function of the cerebellum?

A

Responsible for muscle coordination and movement

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15
Q

What is the general function of the medulla oblongata?

A

Controls involuntary actions eg heart rate and breathing rate

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16
Q

What is the cerebrum?

A
  • largest part of the human brain
  • Carries out a variety of functions involved with conscious activities
  • consists of 5 lobes
  • divided into 2 halves (cerebral hemispheres), joined together by a band of nerve fibres called corpus callosum
  • has a thin outer layer called the cerebral cortex (grey matter) and white matter underneath (which consists of myelinated axons of neurones)
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17
Q

What is the cerebral cortex?

A
  • outer layer of the cerebrum
  • consists of cell bodies of neurones
  • highly folded, increasing the surface area and allowing it to contain greater number of neurones
  • more neurones in brain = more connections between neurones
  • more connections between neurones = greater ability of brain to carry out more complex behaviours
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18
Q

What is the hypothalamus?

A
  • in the middle of lower part of brain, just above the pituitary gland
  • involved in homeostasis - monitors blood flowing through it and releases hormones/stimulates pituitary gland to release hormones

REGULATING BODY TEMPERATURE:
•monitors blood temp and initiates homeostatic response if temp gets too high/low

OSMOREGULATION
• monitors concentration of blood
• if too high, posterior pituitary gland stimulated to release ADH, increasing water retention in kidneys
• hypothalamus also generated feeling of thirst, increasing water intake

REGULATING DIGESTIVE ACTIVITY
• controls secretion of enzymes in gut and peristalsis
• also generates feeling of hunger,causing us to increase food. Intake. If blood nutrient conc is too low

CONTROLLING ENDOCRINE FUNCTIONS
• hypothalamus releases chemicals that cause the pituitary gland to release certain hormones that control a variety of processes (metabolism, sleep, mood, sexual functions etc)

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19
Q

What is the pituitary gland?

A

At bottom of brain below hypothalamus

Produces a range of hormones
• some directly influence and regulate processes, some stimulate the release of further hormones from specific locations in the body

Divided into 2 sections
• anterior pituitary - produces ad releases certain hormones
• posterior pituitary - stores and releases hormones produced by the hypothalamus (ADH and oxytocin)

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20
Q

What is the cerebellum?

A

Lies below cerebrum

Control motor coordination (eg balance - involves eyes, ears, many muscles)

Functions subconsciously

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21
Q

What is the medulla oblongata?

A

Aka medulla

Found at very base of brain where it joins spinal cord

Contains 3 centres that control different functions:
• cardiac centre - heart rate
• vasomotor centre - controls blood pressure by controlling contraction of smooth muscles in arteriole walls
• respiratory centre - breathing rate

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22
Q

What are reflex actions?

A

Involuntary responses to certain stimuli

Very fast and usually have a protective purpose/survival value

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23
Q

What are the benefits of a reflex action?

A

Rapid - reflex arc very short (usually involves only 2 synapses)

Innate - present at birth so immediate protection

Involuntary - no conscious thought requires so brain can deal with more complex responses

Minimises damage to the body

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24
Q

What is the sequence of components on a reflex arc?

A

Stimulus - > receptor -> coordinator -> effector -> response

  • Receptor detects stimulus and creates action potential in the sensory neurone
  • sensory neurone carries impulse to spinal cord
  • relay neurone connects the sensory neurone to the motor neurone within the spinal cord or brain
  • motor neurone carries impulse to the effector to carry out the appropriate response
25
Q

What is the spinal cord?

A

A column of nervous tissues running up the back

Surrounded by the spine for protection

At intervals along the spinal cord, pairs of neurones emerged

26
Q

What is the knee jerk reflex?

A

A spinal reflex - neural circuit only goes up to the spinal cord, not the brain

  • leg is tapped below the patella, stretching the patellar tendon and acting as a stimulus
  • stimulus initiates a reflex arc that causes the extensor muscles on top of the thigh to contract
  • at the same time, a relay neurone inhibits the motor neurone do the flexor muscles causing it to relax
  • the contraction and relaxation of the antagonistic pair of muscles causes the leg to kick

The reflex is used by the body to maintain posture and balance with little effort or conscious thought

Commonly tested by doctors:
•The absence of the reflex may indicate nervous problems
•Multiple oscillations of the leg may be a sign of cerebellar disease

27
Q

What is the blinking reflex?

A

A cranial reflex - it occurs in the brain, not the spinal cord

  • when cornea is irritated by a foreign body, stimulus triggers an impulse along a sensory neurone (5th cranial nerve)
  • impulse passes through a relay neurone in lower brain stem
  • impulse sent along branches of the motor neurone (7th cranial nerve) to close the eyelids
  • a consensual response - both eyelids close in response to stimulus
  • occurs in approx 1/10th of a second

Reflex used to protect the cornea from damage (corneal reflex) , as a result of a bright light to protect lens and retina (optical reflex)

Used by doctors to test if someone is brain dead - if reflex present, lower brain stem is functioning

28
Q

What is the fight or flight response?

A
  • a response in situations where there is a high level of stress, fear or aggravation induced by an environmental stimuli
  • rapid and can be crucial for preserving life
29
Q

How are the nervous and endocrine system coordinated in teh fight or fligh response?

A

They work together in a complementary manner to coordinate the fight or flight response

The sympathetic nervous system is responsible for coordinating many of the responses to danger

It’s actions are supported by 2 hormones - adrenaline and cortisol (both secreted from the adrenal glands

Initial part of the response is controlled by nervous system, and response is continued by the endocrine system

30
Q

What is the mechanism of the fight-or-flight response?

A

1) sensory neurones detect environmental stimuli associated with danger and send impulses to the brain
2) the amygdala (small region of brain in cerebrum) sends impulses to various other parts of the brain, including hypothalamus

3) hypothalamus is stimulated to send impulses via sympathetic nerves to adrenal glands
• adrenal medulla secretes hormone adrenaline
• adrenaline stimulates target organs/tissues to increase sensory awareness, making organism more alerts and improving ability to respond to danger

4) at the same time, hypothalamus releases a peptide hormone that stimulates the anterior pituitary gland to release ACTH, which is transported to adrenal glands via bloodstream
• causes adrenal cortex to secrete hormone cortisol
• cortisol stimulates target organs and tissues to increase blood pressure + blood glucose, ensuring tissues have sufficient glucose an oxygen needed for rapid response
• cortisol also suppresses immune system

31
Q

What are the effects of adrenaline?

A

Adrenaline is a steroid hormone secreted form adrenal glands

It is transported via bloodstream and has a rapid effect on cells

Can have a range of effects on a number of different cells:
• stimulate muscles in the irises to contract, causing pupils to dilate
•increases the diameter of the bronchioles by relaxing smooth muscles, increasing airflow to alveoli
• increases amount of blood flowing to brain an muscles via vasodilation
•increases heart rate and stroke volume
• stimulates breakdown of glycogen into glucose in liver cells via enzymes, causing the blood glucose concentration to increase

32
Q

Second messenger model and adrenaline

A

Adrenaline increases blood glucose concentrations by binding to receptors on liver cells that activates the same enzyme cascade that occurs when glucagon binds to specific receptors

1) adrenaline (first messenger) binds to specific receptor (complementary in shape) on the membrane of liver cells
2) enzyme adenylyl cyclase changes shape ad becomes activated
3) activated adenylyl cyclase changes shape and catalyses the conversion of ATP to cyclic AMP, a secondary messenger
4) cAMP binds to protein kinase A enzymes, activating them
5) these activated enzymes activate more enzymes (an enzyme cascade), until active glycogen phosphorylase enzymes catalyse glycogenolysis

The enzyme cascade amplifies the original signal from adrenaline and results in the relaxing of extra glucose by the liver to increase blood glucose concentration

Adrenaline also stimulates breakdown of glycogen stores in uncle during exercise

The glucose produced remains in muscle cells and is used for respiration

33
Q

How does the autonomic nervous system control heart rate?

A

Inside the medulla there is a region called the cardioregulatory centre

The cardioregulatory centre is split into 2:
• accelerator centre which causes the heart to speed up
• inhibitory centre which causes the heart to slow down
Both centres are connected to the sinoatrial node by nerves

34
Q

How does the acceleratory centre affect heart rate?\

A
  • once it has been activated, impulses are sent along the sympathetic neurones to the SAN
  • noradrenaline is secreted at the synapse with the SAN, causing it to increase the frequency of electrical waves it produces.
  • this results in an increased heart rate
35
Q

How does the inhibitory centre affect heart rate?

A
  • once it has been activated, impulses are sent along the parasympathetic neurones to the SAN
  • acetylcholine is secreted at the synapse with the SAN, causing it to reduce the frequency of electrical waves it produces.
  • this results in an decreased heart rate, returning it towards resting rate
36
Q

What activates the acceleratory/inhibitory centres?

A

Exercise causes several internal conditions to change, creating internal stimuli:
• Carbon dioxide concentration in the blood increases
• There is an initial fall in blood pressure caused by the dilation of muscle arterioles

These internal stimuli can be detected by chemoreceptors and pressure receptors located in the aorta and in the carotid arteries (they supply the head with oxygenated blood)

These receptors release nerve impulses that are sent to the acceleratory and inhibitory centres (coordinators)

The frequency of the nerve impulses increases or decreases depending on how stimulated the receptors are:
• Lower frequency impulses activate the inhibitory centre to slow down the heart rate
• Higher frequency impulses activate the acceleratory centre to speed up the heart rate

37
Q

How does the endocrine system affect heart rate?

A
  • adrenaline and noradrenaline are secreted by the adrenal glads, and they both cause an increase in heart rate
  • thyroxine is produced in the thyroid gland and increases heart rate
38
Q

How does adrenaline increase heart rate?

A

Adrenaline is a hormone released during a ‘fight-or-flight’ response

It causes the heart rate to increase.
•The increase in heart rate is beneficial as it allows for a rapid increase in blood supply to respiring muscles
• This means the muscles will have more oxygen and glucose for respiration

It enables high-intensity activities (like running away from a predator) to be an immediate response

39
Q

What are the different types of muscle found within mammals?

A

Skeletal muscle (aka striated/voluntary muscle) - to move bones/skeleton/joints

Smooth muscle (also called involuntary muscle) - to control diameter of arteries/arterioles/bronchi/control pupil size/peristalsis

Cardiac muscle - to pump blood in the heart

40
Q

What is cardiac muscle?

A

FIBRE APPEARANCE: specialised striated

CONTROL: involuntary

ARRANGEMENT: cells branch and interconnect, resulting in simultaneous contraction

CONTRACTION SPEED: intermediate

LENGTH OF CONTRACTION: intermediate

STRUCTURE: faint striations, fibres are branched, uninucleated

41
Q

What is smooth muscle?

A

FIBRE APPEARANCE: unstriated

CONTROL: involuntary

ARRANGEMENT: no regular arrangement - different cells can contract in different directions

CONTRACTION SPEED: slow

LENGTH OF CONTRACTION: can remain contracted for a relatively long time

STRUCTURE: no cross-striations (unstriped). Spindle shaped. Uninucleated

42
Q

What is skeletal muscle?

A

FIBRE APPEARANCE: striated

CONTROL: voluntary (conscious)

ARRANGEMENT: regularly arranged so muscle contracts in one direction

CONTRACTION SPEED: rapid

LENGTH OF CONTRACTION: short

STRUCTURE: striped muscle, fibres are tubular, multinucleated

43
Q

What is striated muscle?

A

Makes up the muscles in the body that are attached to the skeleton

Striated muscle is made of muscle fibres, which are highly specialised cell like units:
• contain highly organised arrangement of contractile proteins in the cytoplasm
• each muscle fibre contains many nuclei

Structure of a muscle fibre:
• sarcolemma
•sarcoplasm
• sarcoplasmic reticulum (SR)
• myofibrils
• lots of mitochondria 
• long nuclei
44
Q

What is the sarcolemma?

A
  • Plasma membrane enclosing the bundle of muscle fibres.
  • Parts fold inwards to help spread electrical impulses throughout the sarcoplasm, so the muscle contracts at the same time - these are called transverse system tubules (t-tubules)
45
Q

What are long nuclei?

A
  • resulting from embryonic muscle cells fusing together

* makes muscle stronger

46
Q

What is the sarcoplasm?

A
  • shared cytoplasm within a muscle fibre
  • contains many mitochondria, which provides ATP needed for muscle contraction
  • also contains myofibrils
47
Q

What are myofibrils?

A

long cylindrical organelles made of protein, specialised for contraction

composed of individual contractile proteins called myofilments

two types of myofilaments:
•actin - thinner, 2 strands twisted around each other
• myosin - thicker, long rod-shaped fibres with bulbous heads that project to one side

48
Q

What is the sarcoplasmic reticulum?

A
  • modified ER

* extends throughout the muscle fibre and contains Ca ions required for muscle contraction

49
Q

What are the different parts of a myofibril?

A

H band - only thick myosin filaments

I band - only thin actin filaments

A band - contains the area where only myosin filaments present (H band) and areas where myosin and actin filaments overlap

M line - line in the middle of H band where myosin filaments are attached

Z line - line in the middle of the I band where actin filaments are attached

Sarcomere - the section of myofibril between 2 Z lines

50
Q

What is a neuromuscular junction?

A

Similar to a synapse, but between a neurone and a muscle fibre e

Striated muscle contracts when it receives ab impulse from a motor neurone via the neuromuscular junction

51
Q

Describe the transmission of an impulse across a neuromuscular junction

A

1) an impulse travels along the axon of a motor neurone. When the action potential reaches the presynaptic membrane, Ca2+ ions diffuse into the neurone
2) the Ca2+ stimulates vesicles containing ACh (neurotransmitter) to fuse with the presynaptic membrane. The released ACh diffuses across the neuromuscular junction and binds to complementary receptor proteins on the sarcolemma
3) this stimulates ion channels in the sarcolemma to open, allowing Na ions to diffuse in
4) sarcolemma becomes depolarised, generating an action potential that passes down the t-tubules towards centre of muscle fibre, causing voltage gated Ca ion channels in the SR to open
5) Ca diffuses out of the SR and into the sarcoplasm . Ca ions bind to proteins in the muscle, causing it to contract as per the sliding filament model

52
Q

What prevents muscles from contracting continuously?

A

acetylcholinesterase enzyme in the synaptic cleft breaks down ACh molecules to prevent muscles being continuously stimulated by a single impulse

Ca ions pumped back into SR once the sarcolemma, T-tubules and SR are no longer polarised
• the movement of Ca ions terminates muscle contraction

53
Q

What is observed when the muscle fibre contracts

A
  • i band gets smaller
  • sarcomere gets smaller (distance between 2 Z lines gets smaller)
  • h zone gets smaller
  • a band stays the same size
54
Q

What is the structure of the thick filaments in a myofibril?

A

Made up of myosin molecules, which are fibrous proteins with a globular head

The fibrous part of the mason molecule anchors the molecule into the thick filament

Many myosin molecules lie next to each other with the globular head as all pointing away from the M line

55
Q

What is the structure of the thin filaments in a myofibril?

A

Made up of actin molecules, which are globular protein molecules

Many actin molecules link together to form a chain

Two actin chains twist together to form one thin filament

A fibrous protein known as tropomyosin is twisted around the two actin chains

Another protein known as troponin is attached to the actin chains at regular intervals

56
Q

By what mechanism do muscles contract?

A

The sliding filament model

During muscle contraction, sarcomeres within myofibrils shorten as the z discs are pulled closer together

57
Q

What is the mechanism of the sliding filament model?

A

1) binding sites on actin for the myosin heads are covered up by the molecule tropomyosin
2) calcium ions enter the muscle cell and bind to the binding site on troponin, causing it to change shape slightly. The binding sites for the myosin heads on the actin are exposed
3) myosin heads attach to the binding sites, forming across bridge. The myosin heads have a molecule of ADP and a phosphate attached to them. When the cross bridge is formed, they eject the ADP and phosphate, releasing energy
4) energy is used to bend their heads towards the thin filaments, and pull the thin filaments towards them. This is the power stroke
5) a molecule of ATP replaces the one lost on the myosin head, which breaks down the cross bridge
6) ATP is hydrolysed into ADP and a phosphate, returning myosin back to its original state. The myosin head pulls back down, releasing the thin filament

58
Q

What is the role of ATP in muscle contraction?

A
  • energy needed for the return movement of myosin heads that cause the actin filaments to slide
  • the return of calcium ions back into the SR occurs via active transport
59
Q

What can help maintain the ATP supply needed for muscle contraction?

A

AEROBIC RESPIRATION
Produces lots of ATP, but can be a slow process and relies on oxygen.

ANAEROBIC RESPIRATION
Doesn’t produce as much ATP, faster than aerobic but can take up to 10 seconds before ATP is even produced

PHOSPHOCREATINE
ADP + phosphocreatine -> ATP + creatine
Allows muscles to contract for a short amount of time until mitochondria are able to supply ATP

For prolonged activity, after phosphocreatine has run out, rate of muscle contraction must equal rate of ATP production

OCR Biology (25 decks)

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