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Biology > Organisation of nervous system, the brain, reflexes and muscles > Flashcards

Organisation of nervous system, the brain, reflexes and muscles Flashcards

1
Q

How is the mammalian nervous system STRUCTURALLY organised?

A
  1. CENTRAL NERVOUS SYSTEM
    - Consists of the brain and spinal cord
    - Has nerve tracts instead of nerves
  2. PERIPHERAL NERVOUS SYSTEM
    - Consists of nerves and ganglia outside the brain and spinal cord
    - Has sensory neurones that carry impulses from receptors to the CNS
    - Have motor neurones that carry impulses from CNS to muscles and glands
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2
Q

What is a ganglion?

A

A group of neurone cell bodies in the PNS

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3
Q

How is the mammalian nervous system FUNCTIONALLY organised?

A
  1. SOMATIC NERVOUS SYSTEM
    - Associated with the voluntary control of body movements via skeletal muscles
  2. AUTONOMIC NERVOUS SYSTEM
    - Controls smooth muscle, cardiac muscles and glands
    - It is involuntary

Both are part of the PNS

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4
Q

What are the two parts of the autonomic nervous system?

A
  1. PARASYMPATHETIC
    Rest and Digest
  2. SYMPATHETIC
    Fight or Flight
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5
Q

What are the differences in structure of neurones in sympathetic and parasympathetic nervous system?

A 
SYMPATHETIC
-Short preganglionic neurone
-Long postganglionic neurone
-Uses noradrenaline
PARASYMPATHETIC
-Long preganglionic neurone
-Short postganglionic neurone
-Uses acetylcholine
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6
Q

What’s the structural difference between neurones in the autonomic and somatic nervous system?

A

SOMATIC- heavily myelinated axon

AUTONOMIC- lightly myelinated axon

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7
Q

What are the 5 areas in the human brain’s gross anatomy?

A
  1. Cerebrum
  2. Cerebellum
  3. Medulla Oblongata
  4. Hypothalamus
  5. Pituitary gland
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8
Q

What is the cerebrum?

A

-The largest part of the brain, which is highly convoluted (folded)

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9
Q

What is the structure of the cerebrum?

A
  • Is divided into two cerebral hemispheres that control opposite sides of the body
  • Outer layer of each cerebral hemisphere is the cerebral cortex, made from grey matter
  • Grey matter is unmyelinated neurones, cell bodies and dendrites
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10
Q

What is the function of the cerebrum?

A

With the assistance from the cerebellum, the cerebrum controls all voluntary actions, and some involuntary actions, in the human body

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11
Q

What is the cerebellum?

A
  • Plays an important role in motor control
  • Does not initiate movement, but contributes to coordination, precision and accurate timing
  • Receives impulses from sensory systems of the spinal cord and from other parts of the brain and integrates these impulses to fine-tune motor activity by sending impulses to the prefrontal lobe
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12
Q

Where is movement controlled in the cerebrum?

A

Primary motor cortex located at the BACK OF FRONTAL LOBE

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13
Q

Where does reasoning and decision making occur in the cerebrum?

A

Frontal and prefrontal lobe of cerebral cortex

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14
Q

What is the medulla oblongata?

A
  • Long stem like structure which makes up part of the brainstem
  • Is responsible for autonomic or involuntary functions
  • It contains:
    1) The cardiac centre for heart rate and blood pressure
    2) The respiratory centre for breathing rate
    3) The vasomotor centre for blood pressure
    4) The vomiting, sneezing, coughing and swallowing centres
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15
Q

What is the hypothalamus?

A
  • The main controlling centre for the autonomic nervous system
  • Links the nervous system to the endocrine system via the pituitary gland
  • Functions include:
    1) Monitoring composition of blood plasma
    2) Controlling body temperature
    3) Controlling hunger and thirst
    4) Controlling fatigue, sleep and circadian rhythms
    5) Stimulate or inhibits the pituitary gland by producing and releasing hormones
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16
Q

What is the pituitary gland?

A
  • Is an endocrine gland
  • Is divided into two sections
    1) ANTERIOR gland, producing:
  • ACTH (targets adrenal gland)
  • TSH (targets thyroid gland)
  • FSH and LH (targets ovaries)
  • Growth hormone
    2) POSTERIOR gland, producing:
  • Oxytocin (target uterus and mammary glands)
  • ADH (targets kidneys)
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17
Q

What are the features of reflexes?

A
  1. Have a specific stimulus
  2. Is an involuntary action
  3. Nearly instantaneous response
  4. Prevent damage to body
  5. Involves a neural pathways that doesn’t involve the cerebrum
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18
Q

What is the general reflex arc?

A

1) Stimulus
2) Receptor cells transduces energy to electrical energy
3) Action potential initiated in sensory neurone
4) Nervous impulses travels a long sensory neurone that enters the spinal cord via the dorsal root ganglion
5) Sensory neurone forms synapses with a relay neurone in the spinal cord
6) Relay neurone forms synapses with a motor neurone, which leaves the spinal cord via the ventral root
7) Motor neurone forms synapses with the effector
8) Effector produces response

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19
Q

What is the spinal cord?

A
  • Is a long, thin, tubular structure made up of nervous tissue
  • Extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column
20
Q

What are the functions of the nervous systen?

A

1) Transmission of nervous impulses from the motor cortex to the effectors
2) Transmission of nervous impulses from sensory neurones to the sensory cortex
3) Coordinating reflexes
4) Controlling motor instructions for rhythmic movement, like walking

21
Q

What is the knee-jerk reflex?

A
  1. Striking of patellar stretches the patellar tendon and acts as a stimulus
  2. Stimulus initiates reflex arc that causes extensor muscle on top of thigh to contract
  3. Relay neurone inhibits motor neurone of flexor muscle, causing it to relax
  4. Contraction coordinated with relaxation causes the leg to kick
  5. Absence of reflex may indicate nervous problems and multiple oscillation may be a sign of cerebellar disease
  6. 2 motor neurones, 1 relay and 1 sensory
22
Q

What is the blinking reflex?

A
  • Reflex blink is a cranial reflex involving pons in the lower brainstem
  • Occur in response to an external stimulus such as contact or bright light with the cornea
  • Response is consensual because both eyelids blink
  • Involves 1 sensory, 1 relay and 1 motor neurone
  • Check if lower brainstem is active, confirming if someone unconscious is brain dead or not
23
Q

What are the three types of muscle?

A
  1. Skeletal
  2. Cardiac
  3. Smooth
24
Q

What are the features of skeletal muscle?

A
  1. Striated appearance
  2. Under conscious control of somatic nervous system
  3. Muscle cells are called muscle fibres
  4. Fibres arranged to contract in one direction
  5. Rapid contraction but for a short length of time
25
Q

What are the features of cardiac muscle?

A
  1. Striated appearance but less pronounced
  2. Under involuntary control of the autonomic nervous system
  3. Muscle cells are called cardiomyocytes
  4. Fibres arranged in a branching pattern and connected by intercalated discs
  5. Intermediate contraction speed and length of time
26
Q

What are the features of smooth muscle?

A
  1. Non-striated appearance
  2. Under involuntary control of the autonomic nervous system
  3. Muscle cells are spindle shaped with a wide middle and tapering ends
  4. Fibres arranged in a non-regular pattern
  5. Slow contraction speed but can contract for a long length of time
27
Q

What is the structure of skeletal muscle?

A
  1. Muscle cells are extremely long and are made from many embryonic muscle cells fusing together to make a muscle fibre, making them stronger by reducing cell junctions laterally
  2. Each muscle fibre is multinucleate
  3. The cytoplasm in a muscle fibre is called the sarcoplasm
  4. Bundles of muscle fibres are covered by an additional plasma membrane called the sarcolemma
  5. Sarcolemma folds inwards to from T-Tubules to help spread electrical impulses to allow the muscle to contract as a whole
  6. Many mitochondria to produce ATP for contraction
  7. Endoplasmic reticulum is modified to form the sarcoplasmic reticulum, which contains many calcium ions for muscle to contract
  8. Each muscle fibre contains myofibrils that are specialised organelles that allow the muscle fibre to contract longitudinally.
28
Q

What is the structure of myofibrils?

A
  1. Made from ACTIN and MYOSIN
  2. Actin is thinner and made from two actin molecules twisted around each other
  3. Myosin is thicker and made from many bulbous headed myosin molecules wrapped into a bundle
  4. Myofibrils have a striped appearance with light and dark bands
  5. The SARCOMERE is one repeat pattern of the dark and light bands. It is the functional unit of a myofibril
29
Q

What is the structure of myosin?

A
  • Has globular heads that are hinged, allowing them to move backwards and forwards
  • One head is a binding site for each actin and ATP
  • Tails of several hundred myosin molecules align to form the myosin filament
30
Q

What is the structure of actin?

A
  • Have a binding site for myosin, which is blocked by tropomyosin
  • The tropomyosin is held in place by troponin
31
Q

What is the structure of a sarcomere?

A
  1. Sarcomere is defined as the segment between two adjacent Z-lines
  2. The light band is where the actin and myosin do not overlap (AKA I-Band)
  3. The dark band is where the actin and myosin filaments overlap. It contains the entire length of a myosin filaments (AKA A-band)
  4. The H-zone is the lighter band in the middle of the dark band, where the actin filaments are absent
  5. The Z line is the centre of each light band. It is made from several proteins and they create transverse stability for sarcomere
32
Q

What are the features of slow-twitch muscles?

A
  • Used for muscular endurance, they contract slowly but do not fatigue easily
  • Use oxygen for aerobic respiration
  • Have a large amount of mitochondria and many blood vessels
  • Typically red in colour due to dense supply of capillaries and presence of myoglobin
  • Prevalent in endurance athletes, such as marathon runners
  • Prevalent in muscles that maintain body posture
33
Q

What are the features of fast-twitch muscles?

A
  • Used for muscular strength, they contract rapidly but fatigue easily
  • Respire anaerobically and have less mitochondria, fewer blood vessels and fewer myoglobin
  • Typically lighter in colour
  • Prevalent in strength athletes and sprinters
  • Contain more and thicker myosin fibres
  • Contain creatine phosphate
34
Q

What is the sliding filament theory?

A

-Skeletal muscles contract longitudinally and to achieve this, the actin filaments and myosin filaments in each myofibril slide past each other

35
Q

What is the result of a sarcomere contracting?

A
  1. Light band becomes narrower
  2. Z lines move closer together
  3. H zone becomes narrower
36
Q

What happens when a muscle is relaxed?

A

The actin-myosin binding sites are blocked by tropomyosin.

Tropomyosin is held in place by a globular protein called troponin

37
Q

What are neuromuscular junctions?

A
  • Synapses between a motor neurone and muscle fibres
  • They are found at motor end plates
  • There are many neuromuscular junctions along a muscle to ensure all muscle fibres contract simultaneously
38
Q

What is a motor neurone?

A

A single motor neurone will connect all muscle fibres in a motor unit. When many motor neurones are stimulated then a strong muscle contraction is achieved

39
Q

How does the depolarisation travel in the sarcolemma?

A

By travelling a long the T-Tubules

40
Q

What are the three types of energy supply during muscular contraction?

A
  1. Aerobic respiration
  2. Anaerobic respiration
  3. Creatine phosphate
41
Q

Aerobic respiration as an energy supply:

A
  • Most ATP in muscle contraction is produced this way
  • Requires oxygen
  • Happens in the mitochondria
  • Used for low intensity and long term cycles of muscle contraction and relaxation
42
Q

Anaerobic respiration as an energy supply:

A
  • Fast way of producing ATP
  • Used at the start of muscles that are doing rapid cycles of contraction and relaxation
  • Does not required oxygen
  • Produces lactic acid and is a short term solution
43
Q

Creatine phosphate as an energy supply:

A
  • Creatine phosphate is a store of phosphate groups that can be quickly used to produce ATP from ADP
  • It is a very short term supply of phosphate
  • Used for short bursts of very vigorous exercise
44
Q

How is muscle contraction stimulated?

A
  1. Action potential arrives at neuromuscular junction
  2. Ca2+ voltage-gated channels stimulated to open and diffuse into synaptic knob
  3. Influx of Ca2+ causes synaptic vesicles to fuse with presynaptic membrane
  4. Vesicles release acetylcholine into synaptic cleft by exocytosis
  5. Acetylcholine binds to receptors on the postsynaptic sarcolemma
  6. Binding causes Na+ channels to open
  7. Influx of Na+ causes depolarisation of muscle fibres
45
Q

What is the role of Ca2+ ions in muscle contraction?

A
  1. Action potential spreads a long T tubules in sarcoplasm
  2. Depolarisation causes Ca2+ channels in sarcoplasmic reticulum to open
  3. Ca2+ binds to troponin causing it to change shape, pulling on the tropomyosin, moving it away from the actin-myosin binding site
  4. Myosin head binds to actin filament, forming actin-myosin cross bridges

Biology (33 decks)

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