Topic 14 Flashcards

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1
Q

The nervous system

A

Coordinates and regulates body functions
. Contains neurones through which electrical impulses travel along

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2
Q

The nervous system: Mammalian nervous system

A

Central nervous system (CNS): brain and spinal chord
Peripheral nervous system (PNS): neurones outside CNS

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3
Q

The nervous system: reflex actions

A

Rapid, automatic responses to stimuli that don’t involve the conscious part of the brain -> passage of nerve impulses in reflex action is called reflex arc

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4
Q

The nervous system: sequence of events in a reflex arc

A

Stimulus -> receptor -> coordinator -> effector -> response
1. Stimulus detected by receptors
2. Impulses sent along sensory neuron to CNS
3. Impulses cross synapse between sensory and relay neurone -> impulses continue along relay neuron
4. Impulses cross synapse between relay and motor neuron -> impulses continue along motor neuron
5. Then impulses reach effector -> If it’s a muscle it contracts and if it’s a gland it secretes a hormone

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5
Q

Types of neurons

A

. Sensory neurones
. Relay neurones
. Motor neurones

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6
Q

Synapses

A

Junction between two neurones
- Structure:
. Vesicles containing neurotransmitters
. Synaptic gap
. Receptor proteins

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7
Q

Nerve impulse passing through synapse:

A
  1. Impulse stimulates release of a neurotransmitter molecules from vesicles into synaptic gap
  2. Neurotransmitter molecules diffuse across gap
  3. Neurotransmitter molecules bind with receptor proteins ( on 1 side so impulses have one direction) on next neuron
  4. Impulse is then stimulated in next neurone
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8
Q

Sense organs

A

Sense organ: group of receptor cells responding to specific stimuli -> light, sound, touch, temperatures and chemicals

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9
Q

Structures of eye

A

Cornea: refelcts light
Iris: controls how much light enters pupil
Lens: focuses light onto retina
Retina: contains light receptors -> some sensitive to light of different colours
Optic nerve: carries impulses to brain

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10
Q

Types of receptors in eyes: Rods

A

. Found in peripheral parts of retina
. Very light sensitive -> work well in dim light
. 1 type of rod gives info in black and white -> not colour vision

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11
Q

Types of receptors in eyes: cones

A

. Found packed together in fovea
. Less light sensitive -> work best in bright light
. 3 types of cones give info in different colours -> colour vision

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12
Q

The eyes: pupil reflex

A

Antagonisitic action of circular and radial muscles in iris
. To make pupil wider: radial muscles contract and circular mucles relax -> increases light that enters eye
. To make pupil smaller: circular muscles contract and radial muscles relax -> decreases light that enters eye

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13
Q

The eyes: accomodation -> near objects

A

Eye focuses light on retina by changing the shape of the lens
- Near objects:
. Ciliary muscles contract -> slackens suspensory ligaments
. Lens becomes fat (more curved)
. Increases amount by which light is refracted

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14
Q

The eyes: accomodation -> distant objects

A
  • Distant objects:
    . Ciliary muscles relax -> suspensory ligaments pull tight
    . Lens goes thin (less curved)
    . Decreases amount by which light is refracted
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15
Q

Hormones

A

A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
. Endocrine glands: produce and secrete hormones

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16
Q

Hormones: endocrine glands

A

. Adrenal glands: secrete adrenaline
. Ovaries: secrete oestrogen
. Testes: secrete testosterone
. Pancreas: secretes insulin and glucagon

17
Q

Hormones: adrenaline

A

Hormone secreted in ‘fight or flight’ situations
- Effects:
. Increased breathing rate
. Increased pupil diameter
. Causes heart muscle to contract more frequently and with more force -> heart rate increases
. Causes liver to breakdown it’s glycogen stores to release glucose -> blood glucose level increases

18
Q

Hormones VS nerve impulses: Hormone

A

. Slower message
. Act for long time

19
Q

Hormones VS nerve impulses: nerve impulses

A

. Very fast message
. Act for very short time

20
Q

Homeostasis

A

Maintenace of a constant internal environment
. Homeostatic control: kept using negative feedback systems -> body receptors detect a condition has gone above/below its normal level + trigger a response to bring level back to its set point again

21
Q

Internal body temperature -> mechanisms to reduce body temperature: hairs lie flat

A

Less air is trapped -> skin less insulated + heat lost easily

22
Q

Internal body temperature -> mechanisms to reduce body temperature: sweating

A

Water in sweat evaporates from skin surface taking heat from body

23
Q

Internal body temperature -> mechanisms to reduce body temperature: vasolidation

A

Arterioles near skin surface dilate + more blood through capillaries near skin surface -> heat loss

24
Q

Internal body temperatures -> mechanisms to increase body temperature: hairs stand up

A

Traps an insulating layer of air -> prevents heat loss

25
Q

Internal body temperatures -> mechanisms to increase body temperature: much less sweat

A

Reduces amount of heat loss

26
Q

Internal body temperatures -> mechanisms to increase body temperature: shivering

A

Muscles contract in spasms -> more heat produced from increased respiration

27
Q

Internal body temperatures -> mechanisms to increase body temperature: vasoconstriction

A

Arterioles near skin surface constrict + less blood through capillaries near skin surface -> less heat loss

28
Q

Controlling blood glucose: blood glucose too high

A
  1. Insulin secreted by pancreas
  2. Glucose from blood to liver and muscle cells
  3. Insulin makes liver turn glucose into glycogen
  4. Blood glucose reduced
29
Q

Controlling blood glucose: blood glucose concentration too low

A
  1. Glucagon secreted by pancreas
  2. Glucagon enters liver -> makes liver turn glycogen into glucose
  3. Glucose released into blood by liver
  4. Blood glucose increased
30
Q

Type 1 diabetes treatment: insulin therapy

A

. Insulin therapy: injecting insulin after meals -> glucose removed quickly once food digested

31
Q

Type 1 diabetes treatment: diet

A

Not eating too many simple carbohydrates

32
Q

Type 1 diabetes treatment: exercise

A

Helps remove excess glucose from blood

33
Q

Tropic response: gravitropism

A

Response which parts of a plant grow towards or away from gravity

34
Q

Tropic response: phototropism

A

Response which parts of a plant grow towards or away from a light source

35
Q

Shoot growth: Auxin

A

Plant hormone that chemically controls growth near tips of shoots -> produced in tips and diffuses unequally through plant from there due to light and gravity + stimulates cell elongation
. Phototropism and gravitoprism: examples of chemical control of plant growth

36
Q

Shoot growth: shoot grow towards light

A
  1. Auxin accumulates on side that’s in shade when shoot tip exposed to light
  2. Stimulates cells to elongate faster on shade side -> shoots bends towards light (positive phototropism)
37
Q

Shoot growth: shoot grow away from gravity

A
  1. Auxin distributed unequally by gravity with more on lower side of tip
  2. Stimulates cells of lower side to elongate faster -> shoots bends upwards (negative gravitropism)