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Biology > Control and Coordination > Flashcards

Control and Coordination Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Outline how the endocrine system works:

A
  • hormonal
  • chemical messengers
  • ductless glands
  • transmitted in the bloodstream
  • effectors are target cells/organs
  • hormone will bind to receptors on cell membranes
  • slow response
  • response is widespread and long lasting
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2
Q

Outline how the nervous system works:

A
  • impulses/action potentials
  • travel along neurones
  • receptors and sensory neurones
  • effectors (muscle/gland) and motor neurones
  • travel along synapses
  • speed of transmission is very fast
  • response is not widespread and is short-lived
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3
Q

Describe the structure of a myelinated sensory neurone

A
  • nucleus in cell body
  • long dendron
  • shorter axon
  • many mitochondria in cell body
  • many RER in cell body
  • synaptic knobs
  • terminal dendrites

myelin
- Schwann cells
- nodes of Ranvier

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4
Q

Describe the structure of a motor neurone:

A
  • nucleus in cell body
  • cell body is in brain/spinal cord
  • short dendrites
  • long axon
  • many mitochondria/RER/golgi in cell body
  • many mitochondria at synaptic knob
  • synaptic vesicles

myelin
- Schwann cells
- nucleus in Schwann cell
- nodes of Ranvier

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5
Q

Describe the structure of a relay neurone

A
  • found in the CNS
  • un-myelinated
  • cell body at end of neurone
  • many mitochondria in cell body
  • RER in cell body
  • nucleus in cell body
  • terminal dendrites
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6
Q

How is an action potential transmitted along a sensory neurone?

A
  • Sodium channels open
  • Na+ enter cells
  • inside of axon becomes less negative and the membrane becomes depolarised

repolarisation
- sodium channels close
- potassium channels open
- K+ moves out of cell
- inside of axon becomes negative/ membrane repolarised

  • myelin sheath insulates axon
  • action potential occurs at nodes only
  • saltatory conduction
  • one-way transmission
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7
Q

What is an action potential?

A
  • a change in the potential difference from -70mV to +30mV across membrane
  • due to inward movement of Na+ ions
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8
Q

What is a resting potential?

A
  • when a neurone is not transmitting an action potential
  • normally -70mV inside
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9
Q

How is a resting potential maintained?

A
  1. Na-K pumps in cell surface membrane
    - use ATP to pump 3Na+ out, and 2K+ in
  2. Presence of many organic anions inside axon
    - K+ ions attracted to anions, prevent loss of K+
  3. Impermeability of axon membrane to ions
    - ions cannot escape out
  4. Closure of voltage-gated channel proteins
    - Na+ and K+ cannot diffuse through membrane
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10
Q

What is depolarization?

A
  • influx of Na+ ions
  • results in inside of axon becoming positively charged
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11
Q

What is repolarization?

A
  • when potential difference returns back to normal across a cell surface membrane (-70mV)
  • Na+ channels close
  • K+ channels open
  • K+ diffuse out of axon
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12
Q

How is the speed of conduction of impulses controlled?

A
  • myelin sheath speeds up transmission
  • insulates axon
  • myelin impermeable to Na+/K+
  • depolarization only at nodes of Ranvier
  • action potentials “jump” from node to node
  • saltatory conduction
  • axons with large diameter
  • larger SA, more depolarization
  • reduce resistance
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13
Q

Describe how a nerve impulse crosses a cholinergic synapse:

A
  • action potential reaches presynaptic membrane
  • depolarization of membrane results in Ca2+ channels opening
  • Ca2+ floods into presynaptic knob
  • this causes vesicles of acetylcholine (Ach)
  • to move towards and fuse with presynaptic membrane
  • Ach released into synaptic cleft
  • Ach diffuses across cleft
  • Ach binds to cholinergic receptors on postsynaptic membrane
  • proteins change shape causing sodium channels to open
  • Na+ diffuses into postsynaptic neurone
  • postsynaptic membrane depolarized
  • acetylcholinesterase breaks down Ach
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14
Q

Explain the role of a synapse:

A
  • ensure one-way transmission
  • receptors only in postsynaptic membrane
  • vesicles in presynaptic neurone
  • wide range of responses
  • due to interconnection of many nerve pathways
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15
Q

Describe the structure of a striated muscle:

A
  • made of muscle fibres
  • cell surface membrane of muscle fibre is called sarcolemma
  • cytoplasm of muscle cell is called the sarcoplasm
  • contains sarcoplasmic reticulum
  • sarcolemma has deep infoldings called T-tubules that send impulses to the SR
  • myofibrils which are cylindrical bundles of actin and myosin
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16
Q

Outline the structure of a sarcomere:

A

sarcomere = between two Z-lines
M line = attachment for myosin filaments
Z line - attachment for actin filaments
A band = contains both myosin and actin filaments
H band = only thick myosin filaments present
I band = only thin actin filaments present

17
Q

What is the sliding-filament theory?

A
  • when muscle is relaxed, tropomyosin and troponin prevent myosin heads from binding to actin
  • muscle contracts, Ca2+ ions are released from the sarcoplasmic reticulum (SR)
  • and bind to troponin
  • conformational change in shape of troponin
  • troponin and tropomyosin move to different positions on thin filaments exposing actin
  • myosin can bind to actin sites forming cross-bridges
  • myosin heads pull actin towards centre of sarcomere/shortens sarcomere/Z-lines closer together
  • mysoin heads hydrolyze ATP to provide energy
  • to enable heads to detach from actin
  • myosin heads tilt back to original position
18
Q

Describe the role of auxin (IAA) in elongation:

A
  • auxin is a plant growth regulator
  • synthesized in meristems/apical buds
  • stimulates cell elongation
  • moves by diffusion from cell to cell
  • inhibits lateral bud growth
  • plant grows taller/upwards
  • auxin interacts with other plant growth regulators for apical dominance
19
Q

Describe the mechanism of auxin:

A
  • auxin binds to receptor protein
  • auxin stimulates ATPase to pump H+ from cytoplasm into cell wall
  • also stimulates K+ channels to open, K+ enters cell, lowering water potential
  • cell wall becomes acidified
  • expansins loosens linkages between cellulose microfibrils
  • cells absorb water by osmosis
  • increase in internal pressure causes walls to stretch + elongate
20
Q

Describe the role of gibberellins in seed germination:

A
  • gibberellin is a plant growth regulator
  • stimulates cell division and cell elongation
  • plants grow tall
  • dominant allele/Le causes synthesis of enzymes
21
Q

Describe the mechanism of gibberellin:

A
  • seed is dormant
  • water enters seed by osmosis
  • embryo synthesizes gibberellin
  • gibberellin stimulates aleurone layer
  • by causing transcription of mRNA for amylase
  • to produce amylase
  • amylase hydroylses starch
  • in endosperm
  • to maltose —> glucose
  • glucose used for ATP/energy for growth
22
Q

Describe the mechanism of the venus fly trap:

A
  • sensory hair touched, causing action potential
  • triggered in midrib/hinge cells
  • H+ ions pumped into cell wall
  • cell wall cross links broken
  • calcium pectate ‘glue’ in cell wall dissolved
  • Ca 2+ enters hinge cell
  • water follows by osmosis
  • hinge/midrib cells expand
  • trap leaves go from convex to concave
23
Q

Describe how an action potential is generated from our taste buds:

A
  • chemicals act as stimulus
  • papilla —> taste buds —> chemoreceptors
  • chemoreceptors specific to particular chemical
  • Na+ ions diffuse into cell
  • via microvilli
  • membrane depolarized
  • receptor potential generated
  • stimulates calcium channels to open
  • Ca2+ ions enter cell
  • causes exocytosis of vesicles containing neurotransmitter
  • neurotransmitter stimulates action potential in sensory neurone
  • all or none law
24
Q

What movement occurs in muscle contraction?

A
  • sarcomeres in each myofibril get shorter
  • Z-lines move closer together
  • the energy for movement is provided by ATP attached to myosin heads
25
Q

What is the precise role of ATP in the sliding filament model?

A
  • ATP binds to myosin heads
  • ATP is hydrolysed by myosin heads/ATPase
  • energy used to detach myosin heads from actin
  • myosin heads return to original position

Biology (9 decks)

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