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Biology > Chapter 15- Control and Coordination > Flashcards

Chapter 15- Control and Coordination Flashcards

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1
Q

Describe the endocrine system

A
  • sends information through chemical messengers called hormones
  • hormones travel in the blood, they then travel long distances towards their target organs
  • hormones are made in endocrine glands
  • endocrine glands contain secretory cells that pass their products directly to the blood
  • they travel at a slow speed
  • They use less energy compared to the N.S
  • They have a more widespread effect
  • Their receptors are located on the cell membrane or the cell
  • they are long lasting
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2
Q

Describe the Nervous system

A
  • Sends electrical impulses through nerves
  • there are 2 types of nervous systems:
    >CNS
    >PNS
  • They travel at very high speeds
  • their receptors are located on the cell surface membrane
  • They travel in the neurons directly to the target cells
  • they are short term
  • Their effect is more localized
  • They require large amounts of energy
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3
Q

State the 3 types of neurons

A
  • Sensory: transmits impulses from receptors to the CNS
  • motor : sends impulses to the effector from the CNS
  • relay: Sends impulses from the sensory neuron to the motor neuron
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4
Q

Describe the structural features of a motor neuron that link them to their functions

A
  • contains a cell body with a nucleus and the cell body is located in the spinal cord
  • small regions of RER to synthesize proteins
  • they have dendrites that contain a thin cytoplasm and provide a large surface area
  • long axon to conduct impulses over longer distances
  • the ends of the axon as well as well as the cytoplasm contain mitochondria. the ends have vesicles that contain chemicals called transmitter substances
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5
Q

Describe the structural features of a sensory neuron that link them to their functions

A
  • They have the same features as the motor neuron
  • a long axon in order to reach the source of the stimuli
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6
Q

Describe the myelin

A
  • It is an insulating layer made up of layers of cell surface membranes of specialized schwann cells so are very impermeable to water and ions as they are rich in phospholipids
  • they speed up the rate in which action potentials happen
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7
Q

what are the nodes of ranvier

A
  • these are the uncovered regions by the schwann cells on the axon
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8
Q

ways in which the myelin sheat affect speed of conduction

A
  • stops depolarization
  • prevents leakage of ions and increases insulation
  • it brings about saltatory conduction which is when one action potential jumps from one node to another, which is faster than unmyelinated axons
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9
Q

What is a reflex arc

A
  • The transmission of an impulse from a receptor to an effector without involving the conscious regions of the brain. Some of these actions have no relay neurons and connect the sensory neuron directly to the motor neuron
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10
Q

what refers to a potential difference

A
  • a difference in electrical potential between two points. i.e between the inside and outside of the cell membrane
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11
Q

what results to an excess negative charge in the cytoplasm of the nerve

A
  • despite there being potassium pumps, K+ ions will be attracted to the large negative charged molecules present in the cytoplasm
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12
Q

what refers to a resting potential

A
  • a difference in electrical potential which is maintained across the cell membrane of a neuron.
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13
Q

What are the several factors that achieve a resting potential

A
  • when the plasma membrane is impermeable to Na+/K+ (voltage- gated channels)
  • an increase in negatively charged molecules in the cell
  • The sodium potassium pumps that actively push 3Na+ out of the cell and 2K+ into the cell which increases the K+ inside the cell
  • There are more K+ channels than there are Na+, therefore K+ diffuses down its concentration gradient (outside the cell) faster than Na+ diffuses in.
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14
Q

what causes an action potential

A
  • The rapid change in permeability of the cell membrane to sodium and potassium ions
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15
Q

Describe an action potential step by step
(Depolarization and repolarization)

A
  • 1 first the electric current caused by the stimulus will stimulate the axon causing the opening of the voltage-gated -channels allowing sodium ions to pass through
  • 2 Once sodium ions are inside the cell, it causes a change in the electric potential (depolarization)
  • 3 The depolarization leads to more channels opening allowing more and more sodium ions in (positive feedback)
  • 4 as it gets more positive, and reaches the threshold potential (-50mV or -60mV)
  • after 1ms has passed all sodium channels close so sodium ions stop entering.
  • At the same time, another set of voltage channels open to push potassium ions OUT of the cell, reducing the positive charges inside the cell, returning the potential difference back to -70mV (repolarization)
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16
Q

what refers to a refractory periode

A
  • This refers to the period of time during which a neuron is recovering from an action potential and another action potential is not generated
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17
Q

Describe chemoreceptors

A
  • These are receptor cells that respond to chemical stimuli.
  • they are found in the:
  • taste buds
  • nose
  • blood vessels
  • where they detect changes in CO2 and O2 levels
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18
Q

Describe the tongue’s composition

A
  • the tongue is covered with several bumps called Papillae
  • Each papilla has several taste buds
  • each taste buds consists of 50-100 receptors that detect chemicals in drinks and food
  • Each chemoreceptor is covered with receptor proteins that detect these different chemicals
19
Q

Describe how salts are detected in the tongue to the brain

A
  • Highly selective channels for sodium ions open, allowing Na+ to pass through leading to depolarization
  • the increase in positive charge inside the cell is known as receptor potential, thus the Na+ causes the stimulation of more larger receptor potentials
  • Once this occurs, it allows the opening of voltage gated ions for calcium ions
  • Calcium ions triggers exocytosis of vesicles carrying neurotransmitter to the basal membrane
  • the neurotransmitter stimulates an action potential in the sensory neuron which transmits an impulse to the taste center of the cerebral cortex of the brain
20
Q

Describe the sequence of events of transmitting neurotransmitters through a synapse step by step

A
  1. An action potential occurs at the pre-synaptic neuron, stimulating the opening of sodium ion voltage-gated channels and Calcium ion voltage gated channels. Calcium ions come from the surrounding tissue fluid
  2. The influx of Calcium ions trigger the vesicles that contain Acetylcholine (ACh) to move to the pre-synaptic membrane and fuse with it, emptying their contents to the synaptic cleft.
  3. The post-synaptic membrane contains receptor proteins that are complementary to the ACh molecules and temporarily bind to them
  4. Once they bind, this changes the shape of protein, opening ligand-gated channels to allow Na+ to pass through into the post-synaptic neuron
21
Q

What will happen of Acetylcholine remains in the post-synaptic membrane and how is this consequence reduced

A
  • If ACh remains bound then sodium channels will remain open, resulting to continuous depolarization
  • This is prevented by the enzyme acetlycholinesterase which is found in the cleft and hydrolyses ACh to Acetate and choline
22
Q

State the roles of synapses

A
  • Synapses ensure one way transmission
  • Synapses allow the interconnection of nerve pathways
  • Synapses help the nervous system prioritize important signals and filter out irrelevant ones, preventing overstimulation.
23
Q

Describe Striated muscle

A
  • A type of muscle tissue that is attached to the skeleton
  • Striated muscle only contracts once it receives an impulse from the motor neuron
  • Muscle tissue like this is described as being neurogenic
  • When seen under the microscope , the muscle fibers have regular striations
24
Q

Describe Cardiac and Smooth muscles

A

CARDIAC:
- Myogenic
- Striations
- uninucleate cells joined by intercalated discs
- cells are shorter
SMOOTH:
- Neurogenic
- striations
- Uninucleate
- Cells are longer

25
Q

Describe the structure of a striated muscle fibre

A
  • Sacrolemma (Cell membrane)
  • Sacroplasm (Cell cytoplasm)
  • Sacroplasmic reticulum (Endoplasmic reticulum)
  • The sacrolemma has several infoldings into the interior of the fibre called transverse system tubules
  • Has large amounts of mitochondria
  • The membranes of the SR have several protein pumps to allow calcium ions into the cisternae
  • contain myofibrils that are made up of myosin and actin proteins
26
Q

what refers to the sacromere

A

The part of the myofibril between two Z discs

27
Q

A band:

A

The overlap of thick and thin filaments ( Actin and Myosin)

28
Q

I band:

A

No myosin only actin filaments

29
Q

H band:

A

Only Myosin filaments

30
Q

Z line:

A

An attachment for the actin filaments

31
Q

M line:

A

an attachment for the myosin filaments

32
Q

Describe myosins components

A
  • a fibrous protein
  • globular heads pointing away from the m line
  • they lie in a bundle
33
Q

Describe Actin components

A
  • Globular protein
  • they are linked to form a chain
  • they are twisted with tropomyosin and troponin which is attached to the chain at regular intervals
34
Q

Describe the sliding filament model step by step:

A
  • 1.When a muscle contracts, calcium ions are released from stores in the SR and they bind to troponin
  • 2.Troponin changes shape as a result. Troponin and tropomyosin move to a different position, exposing the binding sites for myosin
  • 3.The myosin heads bind with these sites forming cross-bridges between the 2 filaments
  • 4.The myosin head then moves pulling the actin filaments along towards the center of the sacromere
  • 5.The myosin heads let go of actin once ATP molecules have been hydrolyzed, providing enough energy to let go of the actin.
35
Q

Describe the events that occur when an impulse is sent to a neuromuscular junction and muscle fibre

A
  1. An action potential is made and causes the diffusion of calcium ions into the neuron.
  2. Calcium ions cause vesicles which contain ACh to fuse with presynaptic membrane and is released into the cleft
  3. ACh binds to the receptors in the sarcolemma causing them to open proteins for sodium ions, sodium ions then depolarises the membrane.
  4. The depolarisation spreads down to the T-tubules which trigger channel proteins for calcium ions to open, Ca will diffuse out and go to the troponin and tropomyosin
36
Q

How do Venus Fly traps detect insects

A
  • An insect will usually touch the sensory hairs on the inside of the folded leaves. The deflection of the hair activates calcium ion channels in cells to open so that Ca flows in to generate a receptor potential
  • There’s a time interval of 20-35 seconds in which the second and third hairs are deflected. The leaf will shut
  • The shutting is likely a result of a release of elastic tension in the cell walls
  • further deflections of the sensory hairs by the insect stimulate the entry of calcium ions into gland cells. The Ca stimulates exocytosis of vesicles containing digestive enzymes in a similar way to their role in synapses
37
Q

How is the Venus fly trap adapted to avoid closing unnecessarily and wasting energy

A
  • The stimulation of a single hair does not trigger closure
  • The gaps between the stiff hairs form ‘bars’ to prevent big insects from crawling out and allow small insects to pass through
38
Q

State the 2 plant growth regulators

A
  • Auxins
  • Gibberellins
39
Q

Growth occurs in 3 stages:

A
  • Cell division
  • Cell elongation
  • Cell differentiation
40
Q

How do auxins affect the plant’s growth

A
  • Auxins are involved in controlling growth by elongation
  • Auxin binds to a receptor protein on the cell surface membrane which stimulates ATPase proton pumps
  • This allows H+ ions into the cell wall. In the cell wall, there are proteins known as expansions which are activated by the decrease in pH. The protein loosens the bonds between cellulose microfibrils and the matrix surrounding them
  • The cells then absorb water by osmosis and the increase in the internal pressure causes the walls to stretch
  • as they stretch, these cells elongate
41
Q

Where are gibberellins mostly found

A
  • Young leaves
  • seeds
  • stems
42
Q

How do gibberellins stimulate growth in plants

A
  • These promote cell extension in stems
  • Gibberellins stimulate enzymes called XET which break hemicellulose molecules so that cellulose microfibrils move further apart, thus expanding.
43
Q

How are gibberellins involved in the control of germination

A

1- Water uptake initiates germination
2- Embryo synthesizes gibberellin in response to water uptake
3- The aleurone layer synthesizes amylase in response to gibberellin
4- Amylase catalyze the hydrolysis of starch to maltose which is broken down to glucose and transferred to the embryo and respired

44
Q

describe the differences between animal and plant coordination

A

TRANSMISSION OF ELECTRICAL IMPULSE:
Plant- Via the cell membrane through plasmodesmata
Animal- Neurons
DEPOLARISATION:
Plant- Outflow of chloride ions
Animal- Influx of sodium ions
REPOLARISATION:
Plant- Outflow of K+ ions
Animals- Outflow of K+ ions

Biology (19 decks)

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