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Biology A-level OCR Yr13 > neuronal communication- organisation, brain, muscles > Flashcards

neuronal communication- organisation, brain, muscles Flashcards

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1
Q

the nervous system is organised structurally into what two systems?

A

central nervous system and peripheral nervous system

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2
Q

Describe the central nervous system?

A

consists of brain and spinal cord

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3
Q

Describe the peripheral nervous system?

A

consists of all the neurones that connect the CNS to the rest of the body. These are the sensory (carry impulses from receptors to CNS) and motor neurones (carry impulses from CNS to effectors)

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4
Q

the nervous system is functionally organised into what two systems?

A

somatic and autonomic nervous system

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5
Q

Describe the somatic nervous system?

A

-system under conscious control- used to voluntarily decide to do something
-input from sense organs output to skeletal muscles
-heavily myelinated neurones

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6
Q

Describe the autonomic nervous system?

A

-system works under subconscious control- involuntary and automatic.
-input from internal receptors, output to smooth muscles and glands
-lightly myelinated neurones

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7
Q

what two systems is the autonomic system divided into?

A

sympathetic and parasympathetic nervous system.

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8
Q

Describe the sympathetic pathway?

A

-outcome increases activity e.g heart rate
-‘flight or fight’ responses
-neurotransmitter: noradrenaline

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9
Q

Describe the parasympathetic pathway?

A

-outcome decreases activity e.g heart rate after exercise
-relaxing responses
-neurotransmitter: acetylcholine

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10
Q

what are the meninges?

A

protective membranes which surround the brain

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11
Q

what are the five main areas of the brain?

A

cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland

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12
Q

Describe the cerebrum?

A

-controls voluntary actions e.g learning, memory, personality, conscious thought
-controls some involuntary actions

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13
Q

Describe the cerebellum?

A

-controls unconscious functions such as posture, balance and non-voluntary movement
-does not initiate movement, but coordinates it

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14
Q

Describe the medulla oblongata?

A

-contains many regulatory centres of the autonomic nervous system e.g heart rate and breathing rate
-control reflex activities

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15
Q

Describe the hypothalamus?

A

-main controlling region for the autonomic system.
-contains two systems for the parasympathetic and sympathetic nervous system
-controls production of hormones (endocrine gland)
-controls concentration of water and blood glucose

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16
Q

Describe the pituitary gland?

A

-stores and releases hormones that regulate many body functions
-found at the base of the hypothalamus
-two sections: anterior pituitary (front section) and posterior pituitary (back section)

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17
Q

Describe the structure of the cerebrum

A

-it is highly convoluted, increasing surface area and therefore capacity for complex activity
-It is split into cerebral hemispheres (left and right)
-most sophisticated processes such as reasoning and decision-making occur in the frontal and prefrontal lobe of the cerebral cortex.

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18
Q

Describe the cerebral hemispheres?

A

-each hemisphere controls one half of the body and has discrete areas which perform specific functions-these are mirrored in each hemisphere
-the size of the sensory area in a cerebral hemisphere is in proportion to the number of receptor cells in the specific body part. Information is passed to association areas, to be analysed and acted upon
-the size of the motor area allocated is in proportion to the relative number of motor endings in it.
-main region which controls movement is the primary motor cortex located at the back of the frontal lobe.
-left hemisphere receives impulses from right side of body
-right hemisphere receives impulses from left side of body

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19
Q

Describe the anterior pituitary?

A

produces six hormones including FSH

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20
Q

Describe posterior pituitary?

A

stores and releases hormones produced by hypothalamus e.g ADH

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21
Q

what is a reflex?

A

involuntary response to a sensory stimulus

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22
Q

what is the reflex arc?

A

pathway of neurones involved in a reflex action

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23
Q

Describe the spinal cord?

A

it is a column of nervous tissue surrounded by the spine for protection. At intervals along the spinal cord pairs of neurones emerge

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24
Q

Describe the knee-jerk reflex

A

-spinal reflex
-when the leg is tapped just below the kneecap (patella), it stretches the patellar tendon. This stimulus initiates a reflex arc that causes the extensor muscle on top of the thigh to contract. At the same time, a relay neurone inhibits the motor neurone of the flexor muscle, causing it to relax.
-this reflex is needed to maintain posture and balance

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25
Q

Describe the blinking reflex

A

-involuntary blinking of the eyelids
-occurs when the cornea is stimulated e.g being touched
-occurs due to bright light- optical reflex
-reflex protects cornea from damage due to foreign objects e.g dust
-cranial reflex (brain)

26
Q

Describe how blinking reflex occurs

A

-stimulus triggers an impulse along sensory neurone (the fifth cranial nerve)
-impulse passes through a relay neurone in the lower brain stem
-impulses are sent along branches of the motor neurone (seventh cranial nerve) to initiate a motor response.

26
Q

Describe how blinking reflex occurs

A

-stimulus triggers an impulse along sensory neurone (the fifth cranial nerve)
-impulse passes through a relay neurone in the lower brain stem
-impulses are sent along branches of the motor neurone (seventh cranial nerve) to initiate a motor response.

27
Q

How do reflexes increase chances of survival?

A

-being involuntary responses: decision-making regions are not involved so brain is able to deal with more complex responses
-not having to be learnt: provide immediate protection
-extremely fast: normally involves one or two synapses
-many reflexes are what we would consider everyday actions

28
Q

what are the different types of muscle?

A

skeletal, cardiac and involuntary

29
Q

Describe skeletal muscle?

A

-responsible for movement e.g biceps and triceps

30
Q

Describe cardiac muscle?

A

-found in the heart
-myogenic cells: contract without need of nervous stimulus

31
Q

involuntary muscle (smooth muscle)

A

-found in walls of hollow organs e.g stomach, bladder
-found in walls of blood vessels and digestive tract

32
Q

what is a sarcomere?

A

basic functional unit of a muscle fibre

33
Q

what is a sacrolemma?

A

plasmic membrane around muscle fibres

34
Q

what is a sarcoplasm?

A

shared cytoplasm within fibres

35
Q

what is a sarcoplasmic reticulum?

A

endoplasmic reticulum in sacromere. This extends throughout the muscle fibre and stores and releases calcium ions required for muscle contraction.

36
Q

what is a myofibril?

A

long cylindrical organelles (made of actin and myosin filaments)

37
Q

what is a myofibril?

A

long cylindrical organelles made of protein and specialised for contraction (made of actin and myosin)

38
Q

Describe muscle fibre structure

A

-number of nuclei which are much longer than normal cells. They are formed as a result of many embryonic muscle cells fusing together. This makes the muscle stronger as the junction between cells would act as a point of weakness.
-Parts of the sarcolemma fold inwards (known as transverse of T tubules) to help spread electrical impulses through out the sarcoplasm. This ensures that the whole of the fibre receives the impulse to contract at the same time.
-Muscle fibres have lots of mitochondria

39
Q

Describe actin filament?

A

the thinner filament. It consists of two strands twisted around each other.

40
Q

Describe myosin filament?

A

the thicker filament. It consists of long rod-shaped fibres with bulbous heads that project to one side

41
Q

What is the light band in a myofibril?

A

region where actin and myosin filaments do not overlap (they are also known as isotopic bands or I-bands)

42
Q

What is the dark band in a myofibril?

A

region where myosin is overlapped with actin (they are also known as anisotropic bands of A-bands)

43
Q

What is the Z-line in a myofibril?

A

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

44
Q

What is the H-line in a myofibril?

A

lighter coloured region found in the centre of each dark band. Only myosin filaments are present. When muscle contracts the H-zone decreases.

45
Q

Describe the sliding filament model?

A

-during contraction the myosin filaments pull the actin filaments inwards towards the centre of the sarcomere.
-the light bands becomes narrower
-the Z-lines become closer, shortening the sarcomere
-the H-zone becomes narrower
-the dark band remains the same width, as the myosin filaments themselves have not shortened , but now overlap the actin filaments by a greater amount.
-simultaneous contraction of lots of sarcomeres means that the myofibrils and muscle fibres contract.

46
Q

Describe the structure of myosin?

A

-Hinged globular heads allowing them to move forwards and backwards
-binding site on the head for each of actin and ATP.
-myosin head acts as a ATPase component. Head is attached to ADP.

47
Q

Describe the structure of actin?

A

-Actin filaments have binding sites for myosin heads (actin-myosin binding sites). During resting state, these binding sites are blocked a protein called tropomyosin which is held in place by the protein troponin. This means filaments cannot slide past each other.
-During contraction, the myosin heads form bonds with actin filaments known as actin-myosin cross-bridges.
-troponin can bind to Ca2+ which leads to a conformational shape

48
Q

what is a conformational change?

A

alteration in the shape usually the tertiary structure of a protein

49
Q

What is a neuromuscular junction?

A

point where a motor neurone and a skeletal muscle fibre meet.

50
Q

Why are there many neuromuscular junctions along the length of a muscle?

A

to ensure all the muscle fibres would contract simultaneously.

51
Q

what are the three steps in the mechanism of sliding filament model?

A

1) stimulation
2) attachment
3) detachment

52
Q

Explain the stimulation process of the sliding filament model?

A

-Action potential reaches the neuromuscular junction
-Action potential depolarises sacrolemma and sarcoplasmic reticulum
-Voltage-gated calcium ion channels on the sarcoplasmic reticulum open to release calcium ions into sacroplasm
-Ca2+ binds to troponin
-Ca2+ binding causes its conformational change, pulling the tropomyosin, exposing the actin-myosin binding site

53
Q

Explain the attachment process of the sliding filament model?

A

-myosin head binds to actin-myosin binding site, forming cross-bridges
-myosin filament flexes, pulling actin along, releasing ADP

53
Q

Explain the attachment process of the sliding filament model?

A

-myosin head binds to actin-myosin binding site, forming cross-bridges
-myosin filament flexes, pulling actin along, releasing ADP

54
Q

Explain the detachment process of the sliding filament model?

A

-ATP binds to myosin head, causing it to detach from the actin-myosin binding site on actin
-The ATP attached on the myosin head is hydrolysed to form ADP and Pi
-energy released from ATP hydrolysis returns the myosin head back to its original position.
-Myosin head attaches to the next actin-myosin binding site and the process repeats itself.

55
Q

Describe the neuromuscular junctions

A

-AP arrives at end of the axon causing voltage-gated Ca2+ channels to open
-Ca2+ floods in causing vesicle movement and fusion with the
pre-synaptic membrane
-Acetylcholine is released by exocytosis and diffuses across the
synaptic cleft to fuse with receptors in the sarcolemma
-Binding opens sodium ion channels which allow sodium ions to enter the muscle fibre and cause depolarisation of the sarcolemma
-The wave of depolarisation spreads along the sarcolemma and down the T-tubules into the muscle fibre.

56
Q

Describe aerobic respiration for generating ATP in muscle contraction?

A

aerobic respiration in mitochondria, four in muscle tissue. During in intense activity the rate at which ATP is produced will be limited by the delivery of oxygen to the tissue

57
Q

Describe anaerobic respiration for generating ATP in muscle contraction?

A

oxygen is used up more quickly than the blood supply can replace it, therefore ATP has to generated anaerobically. However this will lead to the production of lactic acid which is toxic and causes muscle fatigue after a few seconds.

58
Q

Describe creatine phosphate for generating ATP in muscle contraction?

A

Creatine phosphate in the sarcoplasm acts as a reserve store of phosphate groups. The phosphate can be transferred to ADP creating ATP very rapidly. This involves the enzyme creatine phosphotransferase and can supply enough ATP for a further 2-4seconds of contraction.

Biology A-level OCR Yr13 (15 decks)

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